Chapter 9

Lung, Kidney, Bone and SkinLung, Kidney, Bone and Skin

Figure 9.1 The spirometer measures lung capacities and lung volumes. Because the subject cannot make the lung volume equal to zero, the spirometer cannot measure RV and FRC.

Residual Volume (RV)

Functional Residual Capacity (FRC)

Vital Capacity (VC)

Inspiratory Capacity (IC)

Tidal Volume (TV)

Inspiratory Reserve Volume (IRV)

Expiratory Reserve Volume (ERV)

Counterweight

Kymograph

Bell

Pulley

Water seal

Soda-lime cannister

Mouthpiece

Tube to the patient

One-way Valves

Figure 9.2 In the water sealed spirometer, expired CO2 is removed in the soda-lime cannister.

V B

P L

V L

P B

Shutter

P L Flow Q

P B Lung

Pneumotachometer

Body plethysmograph

Figure 9.3 The total body plethysmograph measures lung volume with the shutter closed and the airway resistance via a pneumotachometer with the shutter open.

Airway resistance:RAW = PL/Q

Figure 9.4 A model for two electrode impedance plethysmography for cylindrical vessels.

A

LZ

b

b

:blood of impedance Shunting

A

Electrodes

L

Meter

QF ine m eshscreen

C lose ly packedchanne lsQ

P

(a ) (b )

P

Figure 9.5 A pneumotachometer measures flow from a pressure drop P across resistance elements such as (a) a fine mesh screen or (b) capillary tubes or channels.

Kidneys

Ureter

Bladder

Urethra

Figure 9.6 The kidneys excrete urine through the ureters to the bladder, where it is voided through the urethra.

Blood from the patient

Cleansed blood to patient

Dialysate input

Dialysate output

Dialyser

Hollow fibers

Hollow fibers Adjustable constriction

Figure 9.7 Typical dialyser. (a) indicating the counter current flow of the blood and the dialysate (b) Cross sectional view of the dialyser.

Figure 9.8 Blood from an artery flows past a membrane in the hemodialysis machine, then returns to a vein.

Blood from patient

Heparin infusion

Dialyser Venous pressure gage

Air/foam detector

Blood returning to patient

Blood leak detector

Dialysate flow meter

Dialysate pressure gage

Dialysate pump

Heater Spent dialysate to waste Adjustable

constriction Proportioning pump Conductivity

and pH cell

Pump

Pure water

Concentrate

Dialysate Supply Peritoneal

Cavity Body Fluids

Spent Dialysate

Valve Pump

Heating Element

Check Valve

Catheter

Pump

Figure 9.9 A simple schematic of a peritoneal dialysis system.

R f

vo

v i

R i13 k

2 k

15 V

Figure 9.10 Dialysate weight measuring circuit.

Scintillation detector

X-ray dual beam radiation source

Dual beam

Soft tissue

Bone

Figure 9.10a In a dual photon absorptiometer, an X-ray source is filtered to emit at two discrete energies.

original unstretched length

the elongation of the cylinder

L

F

A, E

L

Force

Force, F Stress,

E = Elastic modulus

AE/L = Stiffness

y = Yield load strength

F y = Yield

c = Ultimate tensile strength F ult = Failure

load

Deflection, L Strain,

Figure 9.11 Tensile stress on a cylindrical bar causes tensile strain .

(a) (b)force

the cross-sectional area

the elastic (Young’s) modulus

LL

F

F

W

A = LW

Figure 9.12 Shear stress , causes shear strain .

the cross-sectional area

force original unstretched length

change in length

Figure 9.13 Four strain gage resistances R1, R2, R3, and R4 are connected as a Wheatstone bridge. vi is the applied voltage and vo is the output voltage, which

must remain ungrounded and feeds a differential amplifier. Potentiometer Rx balances the bridge.

R1

R4

R2

R3

R x

v i

vo

v o

High permeability alloy core

Secondary coil

Secondary

coil

Primary coil

v i

x

Figure 9.14 In a linear variable differential transformer, displacement of the high permeability alloy changes the output voltage.

Moving head

Grip

Specimen

Grip

Fixed head

Bonded strain gage

LVDT

Figure 9.15 The uniaxial tension test measures force versus elongation.

Figure 9.16 Decay of oscillation amplitude in the pendulum device permits calculation of the coefficient of friction of a joint.

Weights

Bone joint(pivot)

Rocking movement

G assource

M eter

H um id ity sensor

S kin

F low ra te = R

Figure 9.17 The flow hygrometer measures the increase in humidity of gas flowing over the skin.

Transepidermal Water Loss:

K = instrument constantV = increase in the sensor outputR = gas flow rateA = the skin area isolated by the measuring chamber

S ensor

S kinT im e

l

v

Transien t linearportion

Figure 9.18 The closed cup hygrometer: (a) configuration of measuring cup, (b) typical sensor output curve.

(a) (b)

K = instrument calibration constantl = distance between the detector and the skin surfacev = detector voltaget = time

Figure 9.19 The open cup hygrometer: (a) configuration of measurement cylinder, (b) typical sensor output curve.

(a) (b)

V and V0 are equilibrium and initial sensor voltagesK = instrument constantD = diffusion coefficient of water in airl = distance between the sensor and the end of the cylindrical chamber open to the room air

V o

S ensorvo ltage

T im e

l

S kin

S ensor

Green

GreenRedRed

Epidermis

DermisSuperficial vascularplexus

Deep vascular plexus

Figure 9.20 The ratio of reflected red to green light is measured in the Dermaspectrometer and erythema meter.

Subcutis

(a) (b)

Figure 9.21 (a) The spectrum of object light is compared with the spectrum of the light source alone to allow for differences in lighting of the object (b) Illuminating light is diffuse whereas measured light is perpendicular to the object (d/0).

Sensors

Light

Sensor

Object Object

Reflected light

Emitted light