--a
FINAL REPORT NASA Lyndon B. Johnson Space F l i g h t C t r .
Cont rac t NAS 9-17516
31 Mar 1986
(NASS-CFt-171949) A N E W A F E 6 C A C I i ' I C ) ;Jd7- i 5952 N C N - i h V A S I V E O X Y G E N A T E L IYiXE2 V E A C U S F C 2 ( S U B ) 2 Einal €€port ;Vacun€trics, I u c . )
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https://ntrs.nasa.gov/search.jsp?R=19870006249 2020-06-23T07:36:04+00:00Z
FINAL REPORT
31 March 1986
Contract NAS9- 1 7 516
NASA Lyndon B. Johnson Space F l i g h t Center
CONTENTS
Page
1. S c i e n t i f i c Review: A new approach t o non-invasive 1 2 oxygenated mixed venous PCO
2. F i she r System Users Manual 48
3 . Fishe r System Documented
Appendix A
A l - A l 2
c
. A NEW APPROACH TO NON-INVASIVE OXYGENATED MIXED VENOUS PCOz
Joseph A. Fisher, M.D., F.R.C.P.(C) Department .of Anesthesia The Wellesley Hospital, Toronto Assistant Professor, Faculty of Medicine University of Toronto
Clifford A. Ansel Division of Engineering Science Faculty of Applied Science and Engineering University of Tor on to
Address reprints to: Dr. J. A. Fisher, Department of Anesthesia Room 150, Turner Wing, Wellesley Hospital 160 Wellesley Street, Toronto, Ontario, M4Y 153
- 2 -
Glossary of abbreviations
C.O.
bco,
FRC
vD A
CaC0,
CVCO,
PGCO,
PaC0,
FI
FE
F~~~
- V
cardiac output
amount of C02 exhaled per minute which in steady
state equal to the COq production rate
functional residual capacity
dead space
alveolar
arterial CO, content
mixed venous CO, content
arterial CO, partial pressure
mixed venous CO, content
refers to fractional concentration of inspired gas
refers to fractional concentration of expired gas
fractional concentration of a gas in the FRC
-E1 subscript = end inspiratory
-EE subscript = end expiratory
mixed venous concentration
D(c-A)COi pulmonary arterial (mixed venous)-alveolar COP
concentration gradient
- 3 -
Introduction
The purpose of this study was to develop a clinically practical
techique to calculate mixed venous C02 partial pressure
(P7CO2) for the calculation of cardiac output (C.O.) by the Fick
technique.
.
The basis of using a Fick approach to measuring cardiac output
has been extensively reviewed by Grollman (1).
C02, the Fick principle states that the cardiac output is equal to
the C02 production (VC02) divided by the arterio-venous
C02 content difference of the pulmonary vessels
(C3C02-CaC02). Stated in symbols,
As it applies to
. co = vco, L CX02-CaC02
where CGC02 is the C02 content of blood in mixed venous blood
entering the lungs and CaC02 is the C02 content of arterial
blood. Of these, VC02 can be measured by analyzing a time
collection of expired gas for C02. The CaC02 can be
calculated from arterial partial pressure for C02 (PaC02).
This in turn can be calculated noninvasively from end tidal gases
(2) or relatively easily from an arterial puncture. It is the
difficulties inherent in the noninvasive estimation of (PIC02)
that have been the impediment to widespread application of the
technique.
A review of the principles involved in the various techniques
used to estimate P?CO2 (for C+CO2 calculation) is presented by
Richards and Strauss (3). They classify these techniques as attempts
to "use the lungs as an aerotonometer, in an attempt to bring the lung
gases into equilibrium with inflowing venous (pulmonary artery) blood
before recirculation alters the character of this inflowing blood".
These, as well as the more recent techniques depend on data gathered
after certain subject manoeuvres.
Breath holding techniques
In one method as used by Dubois et at (4, 19) the subjects held
their breath for variable periods of time then exhaled and a
sample of end tidal gas was analyzed. The mixed venous PC02
was derived from extrapolation of the end tidal PC02 values to
an asymptote at infinite time or by calculating when the amount of
C02 added to the lung was equal t o 0 (16).
Frankel et a1 (5) had their subjects take a breath to vital
capacity of gas containing either 100% O2 or 12X C02 in
02. They held their breath and exhaled 500 ml at 5 seconds and
then again at 15 sec.
alveolar PC02 to PVC02, the PVC02 was calculated by
extrapolating to the same PC02 value from above and below.
Rebreathing techniques
Defares (6) had subjects rebreath from a closed container and
samples were analyzed after each exhalation.
steadily in an exponential manner towards an asymptote (PSCO2)
which was mathematically and graphically calculated.
Assuming the exponential approach of
The PC02 rose
ii) Collier ( 7 ) , and later McEvoy et a1 (2) and Powles (8)
described a technique where the subjects rebreathe from a bag
containing an amount of C02 designed to allow the system to
equilibrate at the mixed venous C02 tension.
These techniques have been shown to predict mixed venous PC02
extremely well in clinical situations such as patients under
general anesthesia (9), or patients suffering from congestive heart
failure (lo), severe respiratory disease (ll), with hypercapnea (12)
and other severe diseases requiring intensive care (13, 14). Yet
despite this and despite exhortations to be "less invasive" (15),
none of these methods have been widely employed.
The reasons for this are not difficult to discover. The above
techniques have. 3 major drawbacks.
They are cumbersome to perform. They require multiple pieces of
equipment and critical manoeuvres. Often they require trial and
error to find the proper conditions for a test.
They require a patient manoeuvre.
perform some manoeuvre or it must be performed on the patient.
This may be technically difficult and aesthetically unpleasing to
the physician.
They require complex data analysis. Some techniques present
difficulty in identifying data end points (8). Analysis of
complex differential equations and polynomials is a difficult
bedside procedure.
This study was undertaken to a) develop another noninvasive
method for predicting PVC02 that had the advantages of
being easy to apply in a clinical setting
allowing the patient t o continue to breathe at his own
frequency and tidal volume, requiring no rebreathing or
brea tho lding
having a simple linear mathematical approach.
The patient must actively
i)
ii)
iii)
b) to show the feasibility of the method.
A.
R a t i o n a l e
STUDIES WITH N2 AS AN "INERT GAS"
We assumed the lung t o
a ) .
be a s i n g l e compartment c o n t a i n e r
b ) have ins t an taneous mixing
c)
d )
have a volume "FRC" ( f u n c t i o n a l r e s i d u a l c a p a c i t y )
expand and c o n t r a c t by a c o n s t a n t volume
"VT" ( t i d a l volume)
Consider a s u b j e c t brea th ing spontaneous ly a t rest , e q u i l i b r a t e d
t o a gas such as N2 which i s no t absorbed from, o r does n o t e l u t e
i n t o , the lung. A f t e r normal exha la t ion t h e s u b j e c t i n h a l e s a VT
of gas c o n t a i n i n g a f r a c t i o n a l concen t r a t ion of N2(FIN2)
less than t h e prev ious e q u i l i b r a t e d - t o c o n c e n t r a t i o n . When he
e x h a l e s , the end t ida l N2 fractional c o n c e n t r a t i o n (FEN2)
w i l l be less than the e q u i l i b r a t e d c o n c e n t r a t i o n and g r e a t e r than t h e
FIN2. least .
the FEN2 w i l l be equa l t o t h e FIN2.
To e x p l o r e the r e l a t i o n s h i p between FRC, VT, FIN2 and
FEN2 w e conducted the fol lowing experiment.
I f t h e FIN2 i s 0 then t h e FEN2 w i l l be
I f the FIN2 i s equa l t o t h e e q u i l i b r a t e d v a l u e then *l
EXPERIMENT 1: S i n z l e b r e a t h N2 t e s t i n % - Method
S i x normal h e a l t h y male volunteers ' were s t u d i e d . S u b j e c t s were
a t rest and were i n i t i a l l y brea th ing through a mouthpiece and a
. 0 ~ ~ . ~ . ~ 0 . . . ~ . ~ 0 0 . 0 ~ ~ . . 0 0 0 ~ . 0 . . ~ ~ . . ~ . . . 0 . ~ ~ ~ . . ~ ~ ~ 0 . ~ . 0 0 ~ ~ 0 0 ~ ~ . . . . . ~ . ~ .
l* We are ignor ing the small f l u c t u a t i o n i n c o n c e t r a t i o n caused b y t h e
d i sc repancy i n O2 abso rp t ion and C02 product ion .
c i r c u i t dep ic t ed i n Fig. 1.
a l lowing i n h a l a t i o n from one limb and e x h a l a t i o n through another .
i n h a l a t i o n a l limb conta ined a stopcock which a l lowed e i ther room a i r
o r test gas t o e n t e r i t .
o r i g i n a t i n g c l o s e t o t h e mouth.
r o l l i n g seal sp i rometer connected t o the e x p i r a t o r y p a r t of the
c i r c u i t .
The c i r c u i t had two one-way va lves
"he
Gas sampling w a s done through a catheter
Expi ra tory volumes were measured by a
Sub jec t s brea thed room a i r through the c i r c u i t u n t i l they
developed a r e g u l a r p a t t e r n of r e s p i r a t i o n .
e x h a l a t i o n , the s topcock was turned so that the n e x t f o u r b rea ths
c o n s i s t e d of t es t gas .
a i r .
w i t h another tes t gas.
c o n c e n t r a t i o n s between 2% and 60% were used f o r each . . subjec t .
A t the end of an
The subjec t then went back t o b rea th ing room
A f t e r a pe r iod of a t least 5 minutes the p rocess was repea ted
A t o t a l of f o u r test g a s e s con ta in ing N2
Continuous gas sampling was done by a Perking-Elmer MGA-1100
Medical gas ana lyze r which was r e c a l i b r a t e d w i t h known gases be fo re
each s u b j e c t w a s t e s t ed .
d i g i t a l i z e d a t a ra te of 37 samples p e r second and s t o r e d on d i s k by a
Nors ta r Horizon microcomputer.
sampled gas .
The volume and gas a n a l y s i s d a t a was
A l l volumes were c o r r e c t e d f o r the
The r e s u l t s of t he experiment are t a b u l a t e d i n Table 1.
Figure 2 i s a bar graph made from the d a t a of H.S.
the e f f e c t of va r ious F1N2's on the FEN2. The minimum
FEN2 occurs a t t h e minimum FIN*.
the d i f f e r e n c e between i n s p i r e d and exp i r ed N2 concen t r a t ions
b e a r s a l inear r e l a t i o n s h i p t o t h e FIN2.
It i l l u s t r a t e s
Fig. 3 shows t h a t
- a -
Discuss ion
The l i n e a r r e l a t i o n s h i p between FEN2 - FINz and
FINz can be expla ined as follows.
characteristics of the lung wi th r e s p e c t t o N2 are t h o s e of a
s i n g l e chamber w i t h ins tan taneous mixing of i n s p i r e d gas (Fig. 4).
breath i s taken of a known Nz concen t r a t ion of volume VT. The
e x p i r e d c o n c e n t r a t i o n w i l l be the t o t a l amount o f Nz i n the lung
divided by t h e t o t a l lung volume (16),(18).
Again assume the mechanical.
. - A
-
S t a t e d i n symbols:
(1) <VT x FIN2) + FFRCNZ x FRC FEN2 =
VT + FRC
where FFRCN2 i s t h e N2 concen t r a t ion i n t h e FRC.
S u b t r a c t i n g FIN2 from both s i d e s ,
FEN2 - FIN2 = (VT x FIN2) + (FFRCN2 x FRC) - FIN2
VT + FRC
FFRCN2 x FRC
+ FRC -( vT ;FRc - 9 FIN2 + vT
Equation 3 i s i n t h e form y = mx + b, d e s c r i b i n g t h e l i n e a r
r e l a t i o n s h i p between FENZ - F I N 2 and FINZ.
. The e x c e l l e n t c o r r e l a t i o n of these two variables i l l u s t r a t e d
i n Tab le 1 stems from t h e cons t an t VT for each t es t as measured
and the presumed small variation i n FRC a t t h e beginning of each test
g a s series. C l e a r l y , as t h e VT is known and t h e s l o p e of t h e l i n e
- 9 - i s known, t h e FRC c a n be c a l c u l a t e d from t h e s l o p e o f equat ion 3.
This i s t h e s u b j e c t of work i n progress a t o u r l a b o r a t o r y .
We conclude t h a t t h e f i r s t b r e a t h of n i t r o g e n i s d i s t r i b u t e d over
a volume of the lung which behaves as a s i n g l e chamber wi th
i n s t a t a n e o u s mixing. It i s t h i s characterist ic which g i v e s a l i n e a r
r e l a t i o n s h i p between FENZ and FINZ.
I f one had a s i t u a t i o n where t h e FFRC o f gas was unknown (and
r e c o n s t i t u t e d between tests) one could u s e the approach o f s t imulus ( a
b r e a t h of d i f f e r e n t concen t r a t ion g a s ) and r e s p o n s e (FE) t o
c a l c u l a t e it. Any two p o i n t s on an FE'FI vs FI graph would
d e f i n e a l i n e which c r o s s e s t h e a b s c i s s a a t FImFFRC, as can be
seen from equa t ion 3 b y s e t t i n g the l e f t hand s i d e e q u a l t o 0.
- 10 - B.
PC02 (P+CO2) NON INVASIVELY
R a t i o n a l e
STUDIES TO EXAMINE THE METHOD FOR DETEXMINING THE MIXED VENOUS
To p r e d i c t whether w e could expec t a similar l i n e a r r e l a t i o n s h i p
between i n s p i r e d , e x p i r e d and FRC c o n c e n t r a t i o n s o f C02, w e
cons ide red t h e e f f e c t of d i l u t i o n and d i f f u s i o n on t h e FEC02.
I f w e imagine an ins tan taneous i n s p i r a t i o n of V con ta in ing T some C 0 2 , t h e in s t an taneous end i n s p i r a t o r y FFRcCO~
should bear a l i n e a r r e l a t i o n s h i p t o t h e FIC02 as was shown
f o r N2 i n the previous s e c t i o n , ignor ing f o r t h e moment any
C02 d i f f u s i o n i n t o the lung from blood o r t i s s u e s t o r e s .
Knowles e t a1 (16), Dubois (19), Fenn and Dejours (18) showed
tha t t h e change i n C02 t e n s i o n i n the lung p e r u n i t t i m e varies
d i r e c t l y as the C02 g r a d i e n t between mixed venous blood and the
a l v e o l i .
c o n s t a n t .
the lung t o be d i r e c t l y p r o p o r t i o n a l t o t h i s C02 g r a d i e n t .
I n a r e g u l a r p a t t e r n of r e s p i r a t i o n the d i f f u s i o n t i m e i s
We can expec t t h e r e f o r e , t h e change i n C02 t ens ion i n
F ig . 5 r e p r e s e n t s a schematic summary of the above events . We
assume the mixed venous blood has a p a r t i a l p r e s s u r e equ iva len t t o a
C02 c o n c e n t r a t i o n of an arbitrary v a l u e "8WI . (F1C02 = 0 ) , the end t i d a l C02 concen t r a t ion i s d i l u t e d t o "4'*.
"4".
Breath ing room a i r
This induces a g r a d i e n t from mixed venous blood t o a l v e o l i of
I n t h e d u r a t i o n of a b r e a t h , carbon d i o x i d e d i f f u s e s i n t o the
lung i n an amount s u f f i c i e n t t o r e t u r n t h e c o n c e n t r a t i o n back t o "7".
* I n experiment 2 i n Fig. 5 , we assume t h e e v e n t s t a k e p l a c e b e f o r e
one r e c i r c u l a t i o n t i m e so that t h e e q u i v a l e n t mixed venous C02
c o n c e n t r a t i o n stays c o n s t a n t a t "8". The s u b j e c t begins t o b r e a t h e a
- 11 -
gas con ta in ing a FIC02 g r e a t e r than 0 b u t less than the mixed
venous va lue . A t equi l ibr ium, the end i n s p i r a t o r y d i l u t e d
CO w i l l be g r e a t e r t han the previous v a l u e (when F~~~ 2 FIC02 was 0 ) .
blood and a l v e o l i i s diminished compared t o b r e a t h i n g room a i r . There
w i l l be a p ropor t iona te ly smaller amount of C02 d i f f u s i n g i n t o the
a l v e o l i .
than the mixed venous va lue .
4 each o f which a l s o r e p r e s e n t s a s t e p change f o r a s u b j e c t
e q u i l i b r a t e d t o room a i r .
The g r a d i e n t f o r C 0 2 between mixed venous
.
The F ~ c 0 2 w i l l be g r e a t e r than i n exp t . 1 b u t less
Simi la r even t s occur i n experiment 3 and
I n exp t . 5 t h e s u b j e c t i n h a l e s a c o n c e n t r a t i o n of C02 equa l
t o tha t o f h i s mixed venous blood. Af t e r one o r more b r e a t h s the
C02 e n t e r i n g the lungs from the mixed venous blood and inha led g a s
b r i n g the a l v e o l a r concen t r a t ion t o t h e mixed venous v a l u e and there
i s no d i f f e r e n c e between FIC02 and F ~ c 0 2 as long as
the t e s t time i s less than a r e c i r c u l a t i o n t i m e .
Experiment 6 a l s o r e p r e s e n t s a c o n t i n u a t i o n of t h i s argument f o r
t h e i n h a l a t i o n of a g a s whose FCOZ i s g r e a t e r t han that of the
mixed venous blood. The d i l u t i o n argument h o l d s unchanged. Knowles
( 1 6 ) has a l s o shown tha t the amount of C02 d i f f u s i n g back i n t o the
lung p e r u n i t time cont inues t o be d i r e c t l y p r o p o r t i o n a l t o the
g r a d i e n t .
I n summary, w i th r e s p e c t t o C02, the FEC02 i s
p r o p o r t i o n a l t o the amount of C02 d i f f u s i n g i n t o the a l v e o l i which
i s p r o p o r t i o n a l t o t h e mixed venous - a l v e o l a r C02 g r a d i e n t which
i t s e l f i s p r o p o r t i o n a l t o t h e FIC02.
expec t a l i n e a r r e l a t i o n s h i p between FEC02 - FIC02 and FIC02 @is. 6).
Therefore , w e could
- 12 - Experiment 2:
Methods
Thi rd b r e a t h C02 t e s t - -
S i x normal male vo lun tee r s were s tud ied . Sub jec t s were a t res t
and were b rea th ing through a c i r c u i t i d e n t i c a l t o one desc r ibed f o r
n i t r o g e n t e s t i n g (F ig . 1).
O2 and N2 mix tures .
The FI02 w a s g r e a t e r than 30%.
The test gases c o n s i s t e d of C02 i n . The FIC02 var ied from 2% t o 8%.
I n the test sequence the subjec t was al lowed t o b r e a t h e through
the c i r c u i t u n t i l a r e g u l a r pa t t e rn of r e s p i r a t i o n had developed.
the end of a normal exha la t ion t h e s topcock was turned and t h e s u b j e c t
i nha led f o u r b r e a t h s of a tes t gas t r y i n g n o t t o change the depth and
f requency of h i s b rea ths . A t the end of f o u r breaths the s u b j e c t was
r e t u r n e d t o b r e a t h i n g room a i r for a t least 15 minutes b e f o r e another
test gas was appl ied .
sub j ec t .
A t
A t o t a l of f o u r tests were performed on each
I n s p i r e d and exp i r ed C02 was monitored con t inuous ly by a
Perkins-Elmer MGA-1100 Medical gas analyzer . The volumes were measured
by a r o l l i n g seal sp i rometer . A l l ins t ruments were r e c a l i b r a t e d
b e f o r e each s u b j e c t was t e s t e d .
d i g i t a l i z e d and s t o r e d on d i s k by a Nors ta r Horizon microcomputer.
A l l d a t a were au tomat i ca l ly
R e s u l t s
Table 2 l i s t s the results of changes i n exp i r ed C02
c o n c e n t r a t i o n r e s u l t i n g from test gases c o n t a i n i n g d i f f e r e n t
FIC02's.
c o r r e l a t i o n c o e f f i c i e n t s f o r t h e FEC02
FIC02 l i n e s f o r each s u b j e c t .
. It a l s o l i s t s t h e l i n e a r r e g r e s s i o n equat ion and
FIC02 vs
Figure 7 graphs FIC02
- 13 - vs FEC02 - FIC02 f o r subject H . S . (r=-0.999). This
graph illustrates the linear relationship of the points.
Our hypothesis is that the intercept with the abscissa of this
easily generated line is related to the mixed venous PC02 (Table
111) .
Experiment 3: Comparison of third breath PcCOz prediction to - invasive P X 0 2 -
Methods
This protocol was approved by the University of Toronto and St.
Michael's Hospital Animal Care Committee.
anesthetized with nembutal 30 ml/kg and pancuronium bromide .04
mg/kg. Both drugs were supplemented as necessary. The trachea was
intubated with a cuffed $9 Portex endotracheal tube.
Five mongrel dogs were
One dog was
tested during spontaneous ventilation at various depths of anesthetic
and 4 dogs had controlled ventilation.
a) Circuit f o r controlled ventilation: The dogs were ventilated
with a Bennet MA1 ventilator with a VT of 12 ml/kg.
ventilator was attached to a circuit as illustrated in Fig. 8 and 9.
The ventilator was found to deliver a constant tidal volume between
The
the rates of 6/min and 30/min. The circuit consisted of a "bag in a
bottle" set up.
rubber anesthesia bags inside a 5 litre bottle.
This was initially constructed from two, three litre
The bottle neck had 2
.I openings.
it during the inspiratory phase of the pentilator.
was attached to the circuit by a 3-way respiratory stopcock. The test
gas bag was attached to the circuit proximal to the dog by another
One opening was attached to a mushroom valve which occluded
The other opening
respiratory stopcock. Proximal to this stopcock was the inspiratory
limb of the circuit with a one way valve allowing gas to enter the
circuit but not to waft back into the bag. Exhalation was
accomplished through a port proximal to the one way valve.
was also closed by a mushroom valve during the inspiratory phase of
the ventilator. Thus during the control phase of the expiriment the
- inspired volume bypassed the bottle and entered the dog (Fig. 8). For
This port
the test phase, the anesthesia bag was prefilled with a test gas
containing a C02 concentration 0% - 8%. stopcocks were turned so that the next tidal volume from the
ventilator entered the bottle (Fig. 9) and displaced an equal volume
of gas from the bag into the dog. After 4 breaths the stopcocks were
turned to the original position. The dog was again ventilated directly
by the ventilator.
another C02 concentration. After restoration of equilibrium, the
test was be repeated with the new test gas.
During exhalation the
The bag was filled with a test gas containing
. -
Test gases were pre-mixed from 100% C02 and 100% O2 and
stored in identical, unlabeled Douglas bags. Their composition was
changed throughout the day by adding C02 or O2 to the bags.
b) Vascular lines and monitors
Once anesthetized, the dogs had their femoral artery cannulated.
A silastic pulmonary catheter was passed through the external jugular
vein. Both catheters were monitored constantly for pressure. Blood
was sampled from the vascular catheters and analyzed for hemoglobin
concentration, blood gases, and pH. Temperature was monitored by an
electronic rectal temperature probe.
constantly sampled at the mouth and analyzed by an infra-red
. Tidal PC02 was
capnograph (Beckman model LB2).
on a Beckman type RM dynagraph recorder .
All va lues were recorded cont inuously
c) P ro toco l
One dog was anes the t i s ed and t h e t r a c h e a in tuba ted . Af te r
placement of t h e vascu la r c a t h e t e r s , tes t gases con ta in ing 0 - 8%
C02 were a p p l i e d v ia a c i r c u i t as i l l u s t r a t e d i n Fig 1.
a n e s t h e t i c began t o wear o f f and t h e dog ' s minute v e n t i l a t i o n
i n c r e a s e d , t h e tes t gases were again app l i ed .
c
A s t h e
Four dogs were v e n t i l a t e d throughout t h e experiment a t a cons t an t
VT of 10 - 12 ml/kg.
set and t h e dog was allowed t o come t o a s t e a d y state wi th r e s p e c t t o
his mixed venous PCOz.
The frequency s e t t i n g on t h e v e n t i l a t o r was
This was judged t o occur when two
s u c c e s s i v e P'VCO2 va lues ( a s p i r a t e d from the pulmonary a r te r ia l
c a t h e t e r ) a s p i r a t e d wi th in 5 m i n u t e s of each o t h e r d i f f e r e d by less
than 2 mm Hg. When t h i s occurred a blood sample was .drawn from t h e
femoral ar tery and pulmonary a r t e r y c a t h e t e r s and analyzed f o r pH,
PC02, PO2 and Hb.
g a s c o n t a i n i n g an amount of C02 between 0 and 8Z. A f t e r 4 brea ths
the dog aga in was v e n t i l a t e d d i r e c t l y by t h e v e n t i l a t o r s f o r 3 - 5
A test cons i s t ed of 4 breaths of a test
minutes while the a n e s t h e t i c bag i n t h e b o t t l e was being f i l l e d wi th
a n o t h e r test gas . The test gases were a p p l i e d wi thout cons ide ra t ion
of t h e i r C02 concent ra t ion o r t h e i r p rev ious o r d e r of use.
When a t least 2 test gases had been a p p l i e d t h e v e n t i l a t o r .)
f requency was changed and t h e dog al lowed a g a i n t o come t o a new e q u i l i b r i u m wi th r e spec t t o h i s PTC02. 'The above process was
a g a i n r epea ted a t t h e new PVC02.
- 16 - .. d ) Data a n a l y s i s
i ) Calcu la t ion of non invas ive mixed venous C02 CONTENT.
The FIC02, FECOZ and temperature were r ead
.
from t h e previous ly c a l i b r a t e d s t r i p r eco rde r .
end t i d a l FC02 of the t h i r d breath was taken as the
The h i g h e s t
FEC02. A l i n e a r r eg res s ion equat ion of the
FIC02, FEC02 - FICOZ p a i r s was
.computed and the l i n e ex t r apo la t ed t o t h e p o i n t of c r o s s i n g
t h e abscissa.
converted t o p a r t i a l p ressure . This v a l u e was assumed t o be
the PVC02. The pulmonary c a p i l l a r y PO2 was
c a l c u l a t e d from the a l v e o l a r gas equat ion .
and hemoglobin from the i n v a s i v e v a l u e were used t o complete
t h e c a l c u l a t i o n of C02.
the BASIC t r a n s l a t i o n of a program f o r conver t ing PC02
t o CC02 by Olszowka e t a l . (17).
The invas ive CCOz w a s c a l c u l a t e d i n the same way us ing
t h e measured Pv’CO2, PV02, Hemoglobin, and pH.
The f r a c t i o n of C02 a t the i n t e r c e p t was
The base excess
These d a t a were en te red i n t o
ii)
.
RESULTS
Results are tabulated in Table 4. Dog 1 was breathing
spontaneously from room air. The first test was done soon after
induction of anesthesia. The dog was very deeply anesthetised as
evidenced by its relative hypotension and respiratory depression. The
respiratory rate was 4 per minute and irregular in depth and pattern. .
We include this point as raw data but it does not fall within the
criteria for inclusion in the study. During the subsequent tests the
respirations became more regular.
The remainder of the dogs were studied under controlled
ventilation.
Dogs 2 and 3 which were being ventilated by the secondary circuit
we had constructed initially had a significant drop in their tidal
volume when they were switched into the secondary circuit. This drop
in tidal volume was caused by the added compliance of the
animal-circuit system into which the ventilator delivers its constant
tidal volume. Since the control tidal volume was greater than the test
tidal volumes for dogs #2 and #3, the room air control value was not
incorporated into the calculation of PVCO2.
remaining test values should still predict the PGC02 despite this
sudden decrease in VT.
"bag in the box device" was constructed giving only a 10012% drop in
VT in dogs #4 and #5.
values in the mixed venous PC02 calculation.
Theoretically, the
To correct for this problem a smaller \
. We therefore incorporated these control
Fig. 10 illustrates data obtained from dog 83. The intercepts of
the regression lines with the abscissa are taken as the mixed venous
PCOz .
In Fig. 11 we plot noninvasive vs invasive PC02.
regression equation for this line is y = 1.37~ + 9.71 (r~0.96).
The non invasive PC02 prediction is that of O2 saturated
blood whereas the blood aspirated from the pulmonary artery is O 2
desaturated.
(ref 5).
the same using a P X 0 2 calculated from either technique.
1 2 we plot the C02 content as calculated by the new non invasive
against that calculated by the invasive technique.
equation for the line is y = 1.16~ - 6.33. differ significantly from 1.0
differ significantly from 0 (p>O.l for both).
The
. This could account for the higher noninvasive values
- Theoretically, however, the content of C02 should be
In Fig.
The regression
The slope was found not to
and the intercept was found not to
DISCUSSION
1. Model rationale
a) Single compartment model for C02.
Dubois (19) Fenn and Dejours (18) define a term "equivalent lung
volume for C02 "ELV" which includes the air space volume which the
breath distributes to as well as the effect of the breath on dissolved
C02 stores such as lung tissue and blood.
C02 entering the gas spaces during early parts of the inspiratory
cycle come from fast space tissue buffers.
In this concept the
If gas is sampled early
this would give an apparent greater volume of distribution to a breath
of air. This difference in volume of breath distribution between
C02 and N2 is very small but measureable (18).
these authors have considered their data and calcualtions consistent
Otherwise,
with the model of the lung as having a single compartment. Fenn and
- 19 -
Dejours a l s o showed t h a t a s i n g l e b r e a t h r e s u l t i s n o t a l t e r e d by
mixing a t t empt s such as r a p i d r eb rea th ing . I n f a c t a l l t h e i r d a t a as
w e l l as ou r s are c o n s i s t e n t w i th t h e model of t h e lung as a s i n g l e
compartment c o n t a i n e r w i th ins tan taneous mixing. . . b) The r o l e of ?-A g r a d i e n t i n determining PGC02.
I n de te rmining t h e end t i d a l PC02 of a s u b j e c t b r e a t h i n g room
a i r (0% COz), t h e model assumes t h a t the VT of f r e s h a i r
d i l u t e s t h e e x i s t i n g concen t r a t ion i n t h e FRC, e s t a b l i s h i n g an
in s t an taneous end- insp i r a to ry %A g r a d i e n t .
p r o p o r t i o n a l t o t h i s g r a d i e n t d i f f u s e s i n t o the FRC, i n c r e a s i n g t h e
FRC c o n c e n t r a t i o n t o i t s f i n a l va lue of t h e FEC02.
An amount of C02
Now assume t h a t a t es t g a s con ta in ing an .amount of C02 i s
b rea thed f o r 3 b r e a t h s .
r e p r e s e n t a r i s e . t o w a r d s a new equi l ibr ium v a l u e of FEC02
The r e s u l t a n t FEC02 v a l u e s w i l l
( b e f o r e a r e c i r c u l a t i o n t ime) . This new e q u i l i b r i u m va lue i s
determined by two i n t e r a c t i n g e f f e c t s : one a d i l u t i o n e f f e c t , t h e
o t h e r a d i f f u s i o n e f f e c t .
The tes t g a s serves t o d i l u t e t h e g a s i n the FRC, a l though now
the d i l u t i o n e f f e c t i s smaller due t o t h e presence of t h e C02
i n t h e i n s p i r e d tes t gas . This r e s u l t s i n s u c c e s s i v e l y h i g h e r end
i n s p i r a t o r y FFRC v a l u e s analagous t o t h e
tes t gas .
I1 wash in" e f f e c t of any
Because t h e end- insp i ra tory FFRC v a l u e s are h i g h e r ,
. however, t h e %A g r a d i e n t i s smaller, so t h a t less C02 d i f f u s e s
i n t o t h e lung from t h e venous blood du r ing t h e f i x e d pe r iod of a
b r e a t h . It i s t h i s r educ t ion i n g r a d i e n t which causes t h e .
FEC02 v a l u e s t o level o f f a t a new equ i l ib r ium va lue .
two e f f e c t s , taken toge the r e s t a b l i s h t h e new FECOZ.
These
- 20 -
The technique to determine FTC02, assumes that if FVC02
were inhaled, the equilibrium FFRC would rise to F?C02 thereby
eliminating the gradient. Thus, no C02 would diffuse into the
lung and the expired concentration would also be equal to F X 0 2
(i.e. the difference between inspired and expired concentrations
be 0).
- -
Using reasoning analogous to thaw used to develop equation
N 2 7 we state the formula for the end inspiratory C02
concentration in the FRC
I
FRCEI F ( 4 )
will
for
VT + FRC
Where F = Fractional concentration of C02 in the FRC FRCEI
at the end of inspiration
F = Fractional concentration of C02 in the FRC F R C ~ ~
end exhalation
VT and FRC refer to the volume in milliliters of the tidal
volume and functional residual capacity
respectively.
That this is a linear function of the inspired C02
concentration can be shown by simple re-writing of the equation in the
form
F ~ ~ ~ E E . FRC VT+FRC
vT FFRCEx = [ YT + FRC ] FI +
P 1 W vn m r ~ ~ ~ E E = E R b I vT FRC,, = F
A VT+FRC
- 2 1 -
For the sake of formula simplification, let m = VT + FRC
F ~ ~ ~ , , FRC
and b = VT + FRC
The amount of C02 diffusing into the lung for a given time
(AC02) varies directly as the C02 concentration gradient
between the mixed venous blood and the alveoli:
where F7 = mixed venous concentration. The end tidal CO, L
concentration ( F E ) , then must be the sum of the C02 in the
lung at end inspiration plus the amount diffused in, divided by the
net lung volume.
1 FFRcEI
. FRC + k(G - 'T . FX +- 'FRCEE FE =
VT + FRC
from Eq. 5 and subtracting FI from FRCEI
Substituting for F
both sides to change the formulation to identify our end point:
. FRC + k(FT - SI -b) 'T FI + 'FRCEE - FI FE - Fx =
VT + FRC
. FRC + k(FT - b) i V T - - 1) F, +
(7 )
\VT + FRC 1 VT + FRC .
.
A s was illustrated in Fig. 5, this formula represents a summation
of two lines that we expect to cross the abscissa at FvCOZ.
test gases whose FIC02 approach v values are given, the
A s
rises and the D(B-A)COZ falls. When FIC02 PRCEI
F
is equal to the FTCOZ, COz gas will be added to the
until it is equal to the FvCOz. Subsequent breaths F ~ ~ ~ , , LL
taken before recirculation should reflect the fact that FICOZ
= F C021TVC0z=FFRCEE COZ-FECOZ FRCEI
d)
i) Dead space (VD>.
Expected influences on the FE'FI vs FI curve
It is expected that the presence of dead space will not affect
the determination of E C O z by this technique,
If the dead space has a long time constant and a low V/Q, one
would expect it to have an FV C02 close to that of the
mixed venous blood, and to contribute minimally to FE.
If the dead space has a short time constant, and thus a high
D
V/Q, the F
breathing room air.
COz can be expected to be close to 0 when vD
Considering the FECOZ of the first breath, it is
possible that an FIC02 lower than E C O Z would yield the
result of FECOZ-FICOZ, thus underestimating FFCO2. _-
The reason for this is that when the first breath of test gas is
inhaled, the F
below FICOZ while the FFRC rises slightly to a value
higher than FICOZ.
concentrations may combine to yield FEC02-FIC0z,
COz rises slightly from,zero to some value . vD
When the subject exhales, these two
The case for FEC02 of the third breath is different
however. By the third breath, the F C02 approaches
FIC02, since its time constant is small and V/Q high. vD
The
is higher than FIC02 since it also contains the F~~~
* C02 that diffuses into the lung.
therefore, must be higher than FIC02 since it is a combination
The value of FEC02,
of the two concentrations, FVDC02 =F I CO and -
co > co . F~~~ 2 I 2 The FE'FI line for a subject with dead space will still
pass through FIC02=FvC02 if FEC02 of the
third breath is considered, since then
F C02=Fv and FFRC=F3. vD
The combination of these two equal concentrations to form
ii) Right to left shunt (Qs/QT)
Shunted blood will alter the arterial PC02 which in turn will
affect the PGCO2.
areas of the lung, no systematic error in predicting the PvCOz in
predicting the PV'CO2 is expected on this basis alone with the
technique. The Fick technique is otherwise still valid in the
As it is the same P?C02 that perfuses all
presence of shunted blood.
. iii) Cardiac output
The difference in slope between a %first breath N2 line and
the equilibrium C02 line is related to a "diffusion constant"
YEq. 6 and 9) which probably reflects cardiac output influences as
well as diffusion. For these experiments and equations we assume a
- 24 -
c o n s t a n t c a r d i a c output dur ing each test.
PTCO2 i s p red ic t ed from only one test gas r e s u l t , i t i s assumed
that C.O. was cons t an t dur ing the 20 seconds o r s o of the test .
e)
For c l i n i c a l purposes where
. Phys io logic e f f e c t of brea th ing C02
Fowle and Campbell (21) showed the s h o r t term capac i t ance of the
body f o r C02 i s 40 ml C02/mm Hg PC02.
FIC02 equa l t o the P X 0 2 f o r 3 brea ths over 15 sec. and a
C02 product ion of 200 ml/min w e can expec t 50 ml of C02 t o be
r e t a i n e d by t h e body.
For an
This would g i v e an approximate ly 1 mm Hg rise
i n t i s s u e PC02, presumeably r e f l e c t e d i n the r e c i r c u l a t e d
Pv'C02. I f a test gas con ta ins only a f r a c t i o n of the FGC02,
on ly t h a t f r a c t i o n of the C02 c a n be expected t o be r e t a i n e d
g i v i n g a n e g l i g i b l e r i se i n r e c i r c u l a t e d P8C02.
s i t u a t i o n s where pulmonary gas mixing i s poor , a l lowing t h e test t o
The re fo re i n
proceed i n t o the nex t r e c i r c l u a t i o n t i m e while us ing low FIC02 may y i e l d b e t t e r r e s u l t s on balance.
f ) R e l a t i o n of the technique t o p rev ious ly d e s c r i b e d techniques.
The technique w e d e s c r i b e shares a number of t h e o r e t i c a l p o i n t s
w i t h p rev ious techniques which we have used as a foundat ion . DuBois
e t a1 ( 4 ) e s t a b l i s h e d the concept of an "equiva len t a l v e o l a r lung
volume" o r EVL.
N2 as a marker f o r t h e d i s t r i b u t i o n of an i n h a l e d volume.
s tudy w e c a l l e d th i s t h e FRCEI which is the n e t volume of
d i s t r i b u t i o n of a brea th . Although th i$ may o r may n o t be t h e "FRC"
as measured by body plethysmography o r i n n e r t gas d i l u t i o n i t can be
de f ined as that volume t h a t a known amount of i n d i c a t o r gas i s d i l u t e d
This was la ter used by Knowles e t a1 (16) us ing
I n this
These authors are also credited with being the first to
demonstrate the exponential rise of C02 in the lung during
breatholding. This information was later used by Defares (6) and
Collier(7) to extrapolate to PVCO2. Knowles (16) however used
this information to demonstrate that the amount of C02 entering
the lung per unit time was a linear function of the pulmonary capilary
to alveolar concentration gradient. We used this information to
predict the persistant linearity of the FE-FI vs FI curve
for C02 . Despite this agreement on the basics, all of the previous
techniques have in common attempts to equilibrate pulmonary gases to
P?C02.
equilibration occurs (7, 8). The other methods set conditions where
Some methods involve finding conditions where this
equilibration is approached physically and the final value is
calculated mathematically (5, 6).
Our technique is based however on stimulus and response. A
breath of known concentration of gas is given and from the expired
concentration of that gas all calculations are made. Each test in
effect gives 2 points.
FN2=.79) and the test gas.
line through these two points is all the analysis.that is required.
The point from room air (FIC02=0,
An extrapolation from a straight
SUMMARY
We presented a technique for estimating mixed venous partial
. pressure.
pulmonary physiology.
concentration of C02 other than 0 and observing the expired
concentration.
The technique is based on previusly accepted principles of
The approach involves applying an inspired
We developed the theoretical and mathematical basis
- 26 -
for the technique.
Unlike previously described methods, the present technique is
simple to perform.
application of three or four breaths of a test gas while the patient
continues to breath in his usual fashion. The technique is valid in
spontaneous breathing as well as ventilated subjects.
The calculation of P+CO2 requires only the
-
For the calculation of P<C02, inspired and expired FC02
is monitored continuously.
and the third breath of at least one test gas is noted.
consists of plotting FEC02-FIC02 vs FIC02 for
the control gas (FIC02=0) and at least one test gas.
straight line is fit through these points and extrapolated to its
End tidal C02 for FIC02 of 0
Data analysis
A
intersection of the abscissa.
We have demonstrated that this data is
easily definable end point and correlates h
obtained P’VCO2.
easy to obtain, has an
ghly with invasively
The technique shows advantages over previously described
techniques and as such shows promise as a basis for a new clinical
method for measuring non invasive cardiac output.
.
.
REFERENCES
1. Grollman, A.: The cardiac output of man in heal'th and disease, . Charles C. Thomas, Baltimore Md., 1932.
2. McEvoy, J.D.S., Jones, N.L., Campbell, E.J.M.: Mixed venous and
arterial PC02. British Medical Journal 4:687-690, 1974.
3. Richards, D.W. Jr., Strauss M.: The carbondioxide and oxygen
tensions of mixed venous blood of man at rest. J. Clin. Invest.
9:475-532, 1930.
4. DuBois, A.B., Britt, A.G., Fenn, W.O.: Alveolar C02 during
the respiratory cycle. J. Appl. Physiol. 4:535-548, 1952.
5. Frankel, D.Z.N., Mahutte, C.K., Rebuck, A.S.: A noninvasive
method for measuring the PC02 of mixed venous blood.
of Resp. Dis. 117:63-69, 1978.
Am. Rev.
6. Defares, J.G.: Determination of PvC02 from the exponential
C2 rise during rebreathing.
1958 . Collier, C.R., Determination of mixed venous C02 tensions by
rebreathing. J. Appl. Physiol. 9:25-28, 1956.
Powles, A.C.P., Campbell, E.J.M.: An improved rebreathing method
for measuring mixed venous carbon dioxide tensions and its
clinical application. Can. Med. Ass. J. 118:SOl-504, 1978.
J. Appl. Physiol. 13(2):159-163,
7.
8.
(. 9. Frankel, D.Z.N., Sandham, G., Rebuck, A.S.: A new method for
measuring PC02 during anesthesia.
1979 . Br. J. Anaesth. 51:215-219, .
10. Francoisa J.A., Ragan, D.O., Rubenstone, S . J . : Validation of the
C02 rebreathing method for measuring cardiac output in
.
patients with hypertension or heart failure. J. Lab. Clin. Med.
88(4):672-681, 1976.
11. Hackney, J.D., Sears C.H., Collier, C.R.: Estimation of arterial
C02 tension by rebreathing technique. J. Appl. Physiol.
12:425-430, 1958.
12. McEvoy, J.D.S., Jones, N.L. , Campbell, E.J.M.: Alveolar-arterial
PC02 difference during rebreathing in patients with chronic
hyperapnea. J. Appl. Physiol. 35(4):542-545, 1973.
13. Davis, C.C., Jones, N.L., Sealey, B.J.: Measurements of cardiac
output in seriously ill patients using C02 rebreathing method.
Chest 73:167-172, 1978.
14. Franciosa, J.A.: Evaluation of the C02 rebreathing cardiac
output method in seriously ill patinets. Circulation
55(3):449-455, 1977.
15. Powles, A.C.P., Campbell, E.J.M.: How to be less invasive. Am.
J. Med. 67: 98-104, 1979.
16. Knowles, I.H., Newman, W., Fenn, W.O.: Determination of
oxygenated mixed venous blood C02 tension by breath-holding
method. J. Appl. Physiol. 15(2):225-228, 1960.
17. Olszowka, A., Farhi, L.E.: A system of digital computer
subroutines f o r blood gas calculations. Respir. Physiol.
4:270-280, 1968. . 18. Fenn, W.O., Dejours, P.: Composition of alveolar air during
breath holding with and without prior inhalation of O2 and
C02. J. Appl. Physiol. 7: 313-319, 1954.
19. Dubois, A.B., Alveolar C02 and O2 during breath holding,
expiration and inspiration. J. Appl. Physiol. 5(1): 1-12, 1952.
20. Gideon, A.: A new method f o r noninvasive bedside determination of
pulmonary blood flow.
1980.
Med. and Biol. Eng. and Cornput., 18, 411,
21. Fowle, A.S.E., Campbell, E.J.M.: The immediate carbon dioxide
storage capacity of man. Clin. Sci. 27, 41-49, 1964.
.
t
- XI CA 0
753 742 762 725
HS
JF
A0
CE
HI
846 815 838 840
49 1 51 1 510 515
- 742 673 815 726
- 566 579 55 1 562
- 94 1 850 906 948
F I N 2 E N 2 a b l Z 77.97 70.61 0.64 55.82 74.64 18.82 40.42 72.82 3240 22.95 69.40 46.45 2.16 66.66 64.50
78.03 79.45 1.42 56.45 74.64 20.19 40.42 72.82 32.40 22.95 69.40 46.45 216 66.66 64.50
78.17 80.20 203 57.76 70.92 21.16 41.17 76.72 35.55 26.76 74.86 48.12 5.75 71.19 65.44
77.52 77.54 0.02 57.01 76.32 19.72 41.23 75.76 3453 24.58 71.44 46.86 4.69 71.39 66.70
77.60 80.10 2.50 57.71 79.50 21.79 41.30 74.50 33.28 25.96 72.74 46.78 7.28 72.39 65.1 1
77.32 78.10 0.86 56.12 73.6 17.51 40.09 71.14 31.05 23.04 67.31 48.31 3.18 6293 59.75
REGRESS.EQ” 2 I’ Y= -0.84Z + 66.12 - 1 .O
Yx -0.824t + 65.95 - 1 .O
Y= -0.875X + 7 1.37 - 1 .O
Y= -0.903X + 70.58 -0.999
Yx -0.845X + 68.86 -0.998
Yx -0.8 1 7X + 64.15 -0.997
VT * InSplfed tldal volume (ml) FIN2 = fractional inspired N2 concentration (X) FEN2 = fractional expired N2 concentration (70, first breath of test gas DN2* FEN2-FIN2
.
A0 691 0 4.48 4.48 729 225 5.16 2.91 764 4.16 5.91 1.75 729 6.22 6.05 -0.17 762 7.94 6.29 -1.65
CA
HS
- 0.31 6.34 6.03 787 2.29 7.01 4.72
747 6.21 7.39 1.18 751 7.92 7.76 -0.16
740 4.15 7.54 3.39
- 0.21 5.53 5.32 862 2.30 6.65 4.35 963 4.16 6.43 227 857 6.20 6.85 0.65 884 7.99 7.37 -0.62
HTS 813 0.10 5.78 5.68 908 2.30 6.41 4.1 1 1002 417 6.78 2.61 880 6.22 7.15 0.93 900 7.92 7.25 -0.67
HI
JF
JS
782 0.14 5.82 5.68 1086 2.26 6.30 4.04 831 418 6.63 245 839 6.24 7.00 0.76 884 7.91 7.44 -0.47
0.30 5.83 5.53 537 2.40 6.05 3.65 490 4.23 6.34 2.1 1 535 6.26 6.60 0.34 506 7.94 - 0
-
- 0.13 5.33 5.20 586 3.33 6.01 2.68 625 4.38 6.17 1.79 473 6.23 6.72 1.79 513 7.97 7.01 -0.96
REGRESS.EQ" r Y= -0.77 1X + 4.64 -0.997
Y= -0.83W + 6.5 1 -0.996
Yp -0.799X + 5.72 -0.994
Y= -0.8 1X + 5.89 -0.999
Y= -0.798X + 5.80 -0.9998
Yp -0.868X + 5.77 -0.9999
y= -0.78 1 X + 5.28 -0.9997
Sublect A0 CA HS HTS HI JF JS
wmfceYmi 6.02 X 7.82 X 7.16 X 7.27 X 7.27 X 6.65 X 6.76 X
.
n
0
m a
0. u
0 C Q) . * t) 91 X r(
' E %I
0
Y C
( V V I (21 d \o hl C h e W U hl u * u m m m co h M U U m U U
al E aJ > 4 VI Q > C rl E 0 z 0 c (0
aJ 9 + m 0 3 C W
VI 0
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B O
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c FI r c J . ' . 1 . 1
T I B C
I l lus tra t ion of a lung model whose volume i s "FRC" and the gas concentration i t c o n t a i n s . i s FFRC. The lung expands by volume VT and takes i n concentration FI. These gases are instantly mixed (by the propeller) and the model exhales concentration FE.
.
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1 I f I I I I I I I
ZU33 3AISVANI-NON
FISHER SYSTEM USERS MANUAL
Startup Procedure
.
Refer to Figure 6.
1 . Insure that gas tanks are attached and secured t ight ly.
2. Insert FISHER SYSTEM Program Disc in to the disc drive and
close the drive door.
3. Turn gases on. Second stage of the gas regulator should indicate
approximately 5 PSI.
4. Insure that patient mouth port i s sealed f o r the in i t i a l delay .
measurement.
5. Turn main power switch t o ON position. The FISHER SYSTEM
program w i l l load i t se l f and auxiliary subroutines. The program w i l l s ta r t
the delay measurement function ( see section on MAIN MENU) and upon
completion, w i l l return to the main menu.
6. Calibrate the Andros C02 Analyser as per instructions i n the
calibration section.
Calibrat ion of Andros C02 Analuser - The Andros C02 enalyser must be calibrated af ter the system has been
on f o r a t least 10 minutes t o allow fo r a stable operating temperature. To
calibrate the meter, select option * l from the FISHER SYSTEM MENU. The
monitoring display w i l l appear on the screen ( figure 2 , showing
continuous measurements of WCO, - concentration and t idal volume both
numerical 1 y and graphical 1 y.
48
FISHER SYSTEM USERS MANUAL
.
Zero Setting
To zero the signal, use the "ZERO" knob on the front panel (see
figure 6) and observe the numerical W C02 displsy only . Turn the knob i n
the appropriate direction (UP indicated by "U", DOWN indicated by "D" on
the front panel) unt i l the meter reads some value sl ightly greater than 0%
( for example 0.0 1 W). This slight offset w i l l not af fect C02 measurements
w i th in the specifications of the analyser and i s necessary f o r the
fol lowing reason. The Andros analyser output signal, although nominally
0-lOV, can give B signal a t negative voltage fo r zeroing procedures when
used w i th analog systems. The FISHER SYSTEM, however, digit izes th is
signal using an A/D converter for computer data acquisition and analysis.
The A/D converter responds t o positive voltages only. Thus, a reading of
exactly zero on the monitoring screen may correspond t o an of fset
(negative) signal o f any amount, which would af fect any subsequent C02
value measured.
- Span Setting
Once the zero has been set, test gas * 1 i s used t o complete the
two point calibration. ( It i s suggested that th is procedure be carried out
infrequently, as a sizable volume of gas i s used.) Insure that the
patient port i s closed for proper calibration- Press "C" on the
keyboard as per the instructions appearing on the monitor. The valves w i l l
open t o l e t test gas * 1 f lush past the sampling port. Al low 15-20 seconds
fo r the gas t o flush out any gas that was i n the tubing prior t o calibration.
Using the SPAN knob on the front panel, adjust the meter unt i l the numeric
display shows the concentration of test gas " 1 (which may be read from
..
FISHER SYSTEM USERS MANUAL
.
the cylinder). When th is i s set, press <RETURN> to turn of f gas end return
t o the main menu.
The FISHER SYSTEM MENU
The FISHER SYSTEM i s "menu driven". This means that any one of i t s
functions can be performed i n any order desired (w i th some restr ict ions to
be mentioned) o r redone as often as desired, just by selecting the
appropriate action from the menu. The main menu i s a l i s t o f actions that
may be performed by the system and i s returned to a t the end of each
action. It appears on the screen os below.
FISHER SYSTEM MENU
1) CALIBRATE/MON ITOR
2) COMPUTE DELAY
3) VC02/VE/END TIDAL
4) TEST GAS * 1 (OR TEST GAS '3)
5 ) TEST GAS *2 (OR TEST GAS '4)
6 ) PLOT ,- E-I
7) CONVERT P/CCO2 AND CARDIAC OUTPUT
8) CHANGE 6ASES TO 3 & 4 (OR 1 & 2)
9) RESTART
10) ARTERIAL PC02
Some of the l ines may be printed i n inverse mode. These are the functions
that have alfe8dy been performed. Any one of these may be repeated, w i th
the ef fect of replacing the data from the f i r s t measurement w i th that of
50
FISHER SYSTEM USERS MANUAL
the second. A description of each function w i l l now be given.
.
1. CALIERATEIMONITOR
The calibration procedure has already been described. In addition, th is
may be used t o monitor the patient's t idal volume and end t idal PC02 t o
see i f the patient i s i n a steady state.
2. COMPUTE DELAY
This function measures the inherent response delay o f the Andros C02
analyser due t o the fact that the sample c e l l which performs the analysis
i s distal t o the sampling port near the patient port. This i s necessary f o r
accurate computation of VC02 by integration o f the volume and C02
waveforms. The volume measurements are transmitted t o the computer
electr ical ly and are thus instantaneous. This function i s performed
automatically a f ter power up o f the system, t o insure that the delay i s
measured. It can be remeasured by the user i f the sampling f low rate for
the Andros pump i s changed.
Before selecting th is function, insure that the pat ient port i s
closed. The system w i l l f i l l bag '1 w i th test gas * I . The gas w i l l then be
flushed through the exhalation port. The system then calls a subroutine t o
measure the delay and returns to the main menu. WARNING: SHOULD THE
USER SELECT THIS FUNCTION WHILE THE PATIENT IS ATTACHED
(VENTILATED), THE PROGRAM HUST BE TERMINATED TO PREVENT
POSSIBLE INJURY. SEE SECTION ON TERMINATION FOR THE CORRECT
PROCEDURE !!
-. ~-
5 1
~ ~ ~ ~~ ~
FISHER SYSTEM USERS MANUAL
3. VCO2/VF/ END TIDAL - This function measures minute C02 production (VC02), minute
ventilation (VE) , and end t idal PC02. The screen monitor w i l l appear a f t e r
selection o f th is function. The system w i l l record the volume and C02 data
fo r 5* breaths. A subroutine wi l l be called t o integrate the data for
computation o f VC02 . The C02 wave form w i l l appear on the digit izat ion
screen. Use the fol lowing keys t o move the pointer t o the desired value for
end t idal PC02.
H- cursor l e f t , 5* columns per key depression
J- cursor l e f t , 1 column per key depression
L- cursor r ight, 5* columns per key depression
K- cursor right, 1 column per key depression
The numerical value o f PC02 w i l l be shown on the screen. Once the desired
value for PC02 i s pointed t o by the cursor, press <I> t o select the
value and proceed. The digit ization process i s repeated so that another
end t idal PC02 value may-be chosen ( from a dif ferent breath 1. The reason
f o r th is i s that there i s a small f luctuation i n end t idal PCO, b over
successive breaths. Both these values w i l l be used i n determining PvC02.
*see section on changeable program parameters
4. TEST GAS # 1 ( o r TEST GAS *3)
52
FISHER SYSTEM USERS HANUAL
This function administers test gas "1 (or "3) t o the patient and
allows selection of the F I and FE values by the user. Upon selection o f th is
function,the monitor screen w i l l appear. The system w i l l f i l l beg * 1 w i th
the test gas. Excess gas i s used t o f lush any gas remaining i n the tubes
connecting the bag t o the patient v i a the green "pop-off" valve located near
the patient manifold (see figure 1). This insures a constant inspired
concentration of gas. Once the bag i s full, the system waits fo r the patient
t o expire.
Upon expiration, the valves a r e opened so that the patient inspires fron
the reservoir bag o f test gas. Due t o the l imi ted size of the bag, the
system must intermit tent ly pulse gas into the bag, while the patient i s
exhaling. In order t o do this, the system measures the t ime taken for the
patients last exhalation and f i l l s the bag for a fract ion o f th is time.
Durnig the ref i l l ing, however, the patient cannot inspire as the inspiratory
l imb i s occluded t o prevent the f i l l ing gas from f lowing past the sampling
port (see section on Changeable Parameters for information on Frequency
Response). Since only three breaths o f the test gas are given , the
maximum t idal volume allowable should be 0 600 cc.
A f t e r the test gas is.administered, the valves are turned so that the
patient i s breathing room a i r . The digit ization screen (see figures 3 and 4)
w i l l appear w i th the C02 d8t8 from the test. The user should use the
cursor (see cursor instructions i n previous section) t o select FI where the
inspired concentration i s constant. This concentration should be roughly
equal t o the concentration on the gas tank but not necessarily exactly
equal t o th is number do t o possible mixing of the test gas w i th gas from
53
FISHER SYSTEM USERS MANUAL
.
the tubing pr ior t o the test. Once FI i s selected, use the cursor t o select FE
from the th i rd breath. This should be the maximum value o f the expired
wave for FE>FI (see figure 3) o r the minimum value of the wave fo r FE<FI
(see figure 4 1. When this i s completed, the system w i l l return t o the main
menu.
5. TEST GAS *2 (or TEST GAS *4)
This function administers test g a P 2 (or 4) t o the patient exactly as
described previously w i th test gas * l .
6. PLOT E-I
This function computes the regression s tat is t ics for the FE-FI vs F1
l ine t o determine PvC02 from the x-intercept. The slope, correlation
coeff icient and PvC02 values w i l l be displayed, followed by a graph o f the
regression line. Press <RETURN> t o return t o the main menu when finished
viewing graph. NOTE: This function may be performed only a f te r measuring
end t idal PC02 gr~J administering 2 or 4 test gases.
7. CONVERT P/CCO2 - -
This function calls a subroutine t o convert PC02 t o CC02 (by Olszowka
et. 81. 1982). The user must enter the fol lowing patient parameters: base
excess (if known) o r pH, hemoglobin, PO2, and temperature. The C%
content and O2 content of the mixed venous blood w i l l be printed on the
screen. This function must not be selected unt-il the plot t ing function has
54
FISHER SYSTEM USERS MANUAL
been selected.
8. CHANGE GASES TO 3 & 4
This function allows the user to add two test gases t o the system for a
f i v e point determination o f PvC02. Gas tanks must be changed by the user
The main menu ref lects the change. Once selected, the plot t ing function
may not be selected unt i l both of these gases have been administered a t
least once.
9. RESTART
This function erases a l l patient data. Calibration procedure and delay
measurement need not be repeated a t th is time. .
Termination o f Program
Should the program at any time need to be terminated by the user while
performing any of the system functions (Le. not i n the main menu mode 1, the fol lowing procedure should be followed for ventilated patients. Press
<CONTROL> and <RESET> buttons on the APPLE keyboard simultaneously.
This terminates the program and resets a l l valves to the o f f position as
indicated by the front. panel LEDs being of f . Using the manual override
s w i t c h e s on t h e front panel ( f igure 51, turn B V 4 and BV5 to t h e
ON posi t ion . This insures that the venti lator volume will be delivered
direct ly t o the patient.
Changeable Program Parameters
As this version of the FISHER SYSTEM and i t s software are prototypes
55
FISHER SYSTEM USERS MANUAL
only, certain features of the system as well as program parameters were
l e f t manipulable f o r testing and development purposes. The following i s a
l i s t of variables which may be changed as the user sees necessary, w i th
explanations of the parameters and the l ine numbers where they should be
changed.
1 . MEMORY LOCATION 4105 - the contents o f th is location i s an
indicator of the frequency response o f the system for volume
measurements i n the following way. The routine which detects end o f
expiration counts the t ime f o r which the propellor i n the f low meter does
not turn and matches i t against this number. The higher this number, the
greater i s the confidence that a true end expiration has been detected. The
lower th is number, the faster i s the detection and phase change f l a g
(respiratory phase i s indicated on the monitor screen beside the word
EXPIRING. A 1 indicates expiration, a 0 indicates inspiration. See Figure 2.)
The system ini t ia l izes th is value t o 60 on l ine number 1140. This may
.. ~
be raised o r lowered by the user.
2. Eliminate Gas Pulsing - the gas pulsing t o r e f i l l the bag w i t h
test gas between breaths may be eliminated f o r suitable t idal volumes and
respiratory frequencies. To do this, insert as l ine 4144 the following: L .
4144 GOT0 4160
3. 81 - this variable i s the number o f breaths used i n the
measurement o f VCO, and end tidal PC02 . The maximum number of
breaths alloweble by the memory size i s 8 ( minimum i s 1 1 . A more
accurate VC02 i s measured w i th more breaths, and this also al lows better
56
FISHER SYSTEM USERS MANUAL
determin8tion of end t idal PC02 since there are more t o values t o choose
from. The system sets th is variable t o 5 i n i t ia l l y on line 7025. This may
be changed by the user.
3. Cursor $ P I - change 5 on lines 4485 and 4495 t o a
higher number ((10) for faster movement.
Performing the Test
To perform the test t o determine PvC02, the fol lowing functions must
be performed at least once. Before start ing the user should select
9) RESTART
t o insure that old patient data i s erased. Once this i s done, the fol lowing
should be performed i n any order.
3) VC02JVElEND TIDAL
4) TEST GAS '1 (OR TEST GAS '3)
5) TEST GAS '2 (OR TEST GAS *4)
Once these have been performed, repetition of any of these functions i s
optional. In addition,--for- greater accuracy, the user may want t o obtain
additional data by attaching two.additiona1 gases. This may be performed
by selecting
8) CHANGE GASES TO 3 & 4
attaching the gases and then performing
4) TEST GAS '3
5) TEST GAS '4
FISHER SYSTEM USERS MANUAL
Once a l l o f the data points have been obtained, the user should select
6) PLOT E-I
t o determine PvC02. Should the user require CvC02 for d e t ~ t ? i n 8 t i O n o f
cardiac output, the user should f i r s t select
10) ARTERIAL PC02
and then select
7) CONVERT P/CCO2 AND CARDIAC OUTPUT
For fur ther information about each function see the section on the MAIN
MENU.
Trouble Shooting
The fol lowing i s a l i s t of possible problems that may be encountered
w i t h the system and the appropriate corrective actions which should be
taken.
1 . Al l front panel l ights on simultaneously 7 +SV supply fuse has blown.
Turn power off. Replace (see figure 6) wi th MDL 250W 2-5 A fuse.
2. Patient has d i f f icu l ty breathing test !as - patient may be trying t o
breathe against closed valve due t o pulsing. Patient may decrease
respiratory rate o r pulsing may be omitted. Frequency response may be
adjusted (see section on Changeable Parameters).
3. E r r o r messages when converting PI’CCO~ - entered parameters out o f
range . insure that a l l requirements of a minimum test have been
performed including Plotting. Reselect this function. Check that enetered
parameters are correct.
-
4. &pired test gas concentration not constant- check gas system for
FISHER SYSTEM USERS MANUAL
leaks including ballon valves. These may be tested by opening and closing
using the manual switches on the front panel.
c
c
5 9,
- Sys tem Schematic
9 solenoid valve
balloon valve FIGURE 1 .
60
EXPIRING 1 C 0 2 4.90
- 9 - I
- I
9
FIGURE 2. DISPLAY SCREEN
-
I-
- <
I.... J
.
.
,. ...... . r . . . .-.
I ..
I
I
Fl FE
I
I
FIGURE 3. DIGITIZATION SCREEN (FE>FI 1
YT 32
YT
61
'..../ ' ,-..
SPIRO - e 0 BV3 METER 0 -
- - BV4
i
FI FE
- e 0 - - BV5
EXPI R I MG CO2 6-85
VENT FILL 1
- e - - e - o - -rl O q -
I
I
I
I I
I
I
FILL VENT
- e - - e , - 0 - 0 - - -
L
FIGURE 4. DIGITIZATION SCREEN (FE<FI 1
VT ~
FIGURE 5. FRONT PANEL INDICATORS AND SWITCHES
.
elec span zero cal I I I e
.
the FISHER SYSTEM
U UflCUMEO
~ ~ 0 0 0 0 0
0~00000 0000000
main FUSES
On main k12-15 +15 +5 off 0 0 0 0 . 0
F I G U R E 6. THE FISHER SYSTEM .
63
FLOW TRANSDUCER MAINTENANCE
SC-520
The Kozak Modular Flow Transducer SC-520 consists of the flow transducer body and a removable SC-521 turbine cartridge. All SC-521 cartridges are interchangeable. We recommend you keep a spare cartridge on hand. The transducer bodv comDrises the infrared oDto-electronics. and is not submersible. All the cartridges are shock Droof, immersible. and steriiizable. Moisture, condensed vapor, or saliva expelled by the patient will not affect the operation or accuracy of the flow transducer. It will provide long and reliable service if regularly cleaned by rinsing the cartridge in water after use, or cold chemical sterilization to prevent the drying-out and hardening of the saliva or disinfectant deposits inside the turbine cartridge.
To remove the cartridge from the transducer bodv for inmection or cleanine, simply apply moderate axial pressure to the black rear part of the cartridge, and it will pop out easily. Secure the white front end of the cartridge with the other hand to prevent the cartridge from dropping on the floor while removing it. NEVER clean the cartridge by using a cue tip or similar cleaning probe inserted into the turbine cartridge, as this will damage the turbine blade and/or the pivot assembly. ALWAYS keep the transducer clean and use the proper disposable mouthpieces, such as the VACUMED #1026. Improper mouthpieces may cause air leakage, or may not otherwise work properly. To clean the transducer body, use a lint free dry cloth, and do not apply any pressure to the optical lenses inside the body. Always keep it dry.
The accuracy of the SC-520 flow transducer is given only by the mechanical dimensions of the turbine and the impeller. Because the dimensions are constant and consistent, (precision production technology and components), calibration or recalibration is not needed. The operation of the transducer is strictly digital. It transmits electric pulses and the pulses are counted as volume increments. This is the principle of 100% drift free operation and long term stability. The only and essential condition for consistent accuracy is the proper function of the impeller, i.e., its unobstructed rotation capabilities. Therefore, a very simple test of flow rotation sensitivity is a reliable accuracy indicator. The electronic components of the flow transducer - the infrared emitter and the photo transistor - do not have any influence on the accuracy. Any malfunction of the opto-electronic system will result in loss of the electric output signal.
SENSITIVITY TEST Take the turbine cartridge in your hand so that you are facing the rear black end of the cartridge. Start walking with a speed of about half to one mile per hour, watching the impeller rotate inside the cartridge. If the impeller does not rotate freely, it indicates a malfunction of the jewel bearing suspension system, caused mainly by the saliva deposit buildups as a result of insufficient maintenance. In such a case, the cartridge should be immersed in water for a few hours, and then rinsed to remove dissolved deposits. The most efficient rinsing method is to apply a moderate stream of water into the cartridge input opening (the whie end) directly from the water tap. If any malfunction persists, the turbine cartridge should either be sent to the factory for inspection, or replaced.
(Ref E/FLOWTRAN)
3/86
FISHER SYSTEM DOCUMENTATION
ITEM
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
DescriDtion Drawina No.
Bill of Material
------ List of Standard Commercial Components
Block Diagram 1147-6
Interconnection Diagram
Valve Driver Interface
W A S Computer Interface
Turbine Electronics Schematic
Turbine Electronics Parts List
Apple Interface Schematic
Gas Valve System Schematic
Patient Interface, Block Diagram
1147-7
1147-8
1147-9
1147- 10
1147-3
Fig 1
Page
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