38
1 Ventilation Ventilation presented by Draeger-Medical H
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1
Ventilation
Ventilation
presented by
Draeger-Medical
HH
2
Ventilation
Mandatory Ventilation
Spontaneous breathing1
2
3 Basic ventilator settings
4 The model of density
5 Resistance,Compliance,Time constant
6 Ventilation,Perfusion,Diffusion,Distribution
3
Ventilation
Spontaneous breathing1
4
Ventilation
Spontaneous breathing
• Contraction of the diaphragm and the intercostal muscles
• Negative pressure is generated in the lungs to the atmospheric pressure
• Expansion of the chest • Increase in lung volume • Air comes passive from the environment through the upper airways pressure compensation to the atmosphere
INSPIRATION
5
Ventilation
Muscular Force
- 2 mbar
Spontaneous breathing
INSPIRATION
• Contraction of the diaphragm and the intercostal muscles
• Negative pressure is generated in the lungs to the atmospheric pressure
• Expansion of the chest • Increase in lung volume • Air comes passive from the environment through the upper airways pressure compensation to the atmosphere
6
Ventilation
Spontaneous breathing
Position of the diaphragm before inspiration
INSPIRATION
7
Ventilation
Spontaneous breathing
EXPIRATION
• Relaxation of the diaphragm and the intercostal muscles
• Positive pressure is generated in the lungs to the atmospheric pressure
• Reduction of the chest • Decrease in lung volume • Air comes passive through the airways to the environment pressure compen- sation to the atmosphere
8
Ventilation
Elasticity
+2 mbar
Spontaneous breathing
EXPIRATION
• Relaxation of the diaphragm and the intercostal muscles
• Positive pressure is generated in the lungs to the atmospheric pressure
• Reduction of the chest • Decrease in lung volume • Air comes passive through the airways to the environment pressure compen- sation to the atmosphere
9
Ventilation
Spontaneous breathing
Position of the diaphragm after expiration
EXPIRATION
10
Ventilation
Pressure-time-diagram
Flow-time-diagram
Volume-time-diagram
PAW
inmbar
t in sec.
t in sec.
t in sec.
vt
inml
Vinl/min
Spontaneous breathing
ExpirationInspiration
Inspiratory flow
Tidal volume - vt
Expiratory flow
11
Ventilation
• Vocabulary of ventilation
FiO2 fraction of oxygen in the inspired air
0,21 - 1,0
vt tidal volume, volume per breath
4 - 8 ml/kgBW
f breathing frequency 10 - 15 / min
MV minute volume, calculated from the tidal volume and the frequency
MV = f * vt
I : E inspiration - expiration ratio 1 : 1,5
PEEP a positive pressure in the alveoli in comparison to the atmospheric pressure - is increasing the endexpiratory lung volume
12
Ventilation
• Vocabulary of ventilation
paO2 partial pressure of oxygen in the arterial blood
75 - 105 mmHg
paCO2 partial pressure of carbon dioxide in the arterial blood
35 - 45 mmHg
SaO2 oxygen saturation of the arterial blood
95 - 98 %
AaDO2 difference between the partial pressure of oxygen in the alveoli and
the arterial blood
AaDO2 = pAO2 - paO2
at FiO2 = 0,2 10 - 20 mmHg
at FiO2 = 1,0 25 - 65 mmHg
paO2/ FiO2 value with information about the transpulmonary oxygen transport
normal > 450
13
Ventilation
Static Lung Volumes
Tidal volume - vt :• the volume inhaled and exhaled during quiet breathing about 500 - 600 ml
Inspiratory Reserve Volume - IRV :•the volume that can be inhaled further after a quiet inspiration, that is the difference between normal and maximal inspiration about 2,5 l
Inspiratory Capacity :•about 3 l
Expiratory Reserve Volume - ERV :•the volume that can be further ex- haled after a quiet expiration, that is the difference between normal and maximal expiration about 1,5 l
Residual Volume - RV :•the volume remaining in the lungs after a maximal expiration about 1,5 - 2,0 l
Functional Residual Capacity - FRC :•the volume left in the lungs at the end of a quit expiration about 3.0 - 3,5 l
Vital Capacity - VC :•the volume difference between maxi- mum inspiration and maximum expi- ration about 3,5 - 5,5 l
Total Lung Capacity - TLC :•maximal air capacity of the lungs•it is calculated from the VC and RV approximately 6,0 l
14
Ventilation
Mandatory Ventilation2
15
Ventilation
Mandatory ventilation
- Inspiration started by the ventilator- gas delivered by the ventilator goes through the tube, through the airways into the lung- Lung will be stretched- Thorax will be extended and the diaphragm will be pressed down positive pressure inside the thorax
16
Ventilation
Pressure-time-diagram
Flow-time-diagram
Volume-time-diagram
PAW
inmbar
t in sec.
t in sec.
t in sec.
vt
inml
Vinl/min
Plateau pressure - pplat
Peak pressure - ppeak
End expiratory pressure - PEEP
Zero-flow-phase
Volume ControlledVentilation
Constant flow
Tidal volume - vt
17
Ventilation
Inspiration pressure - pinsp
End expiratory pressure - PEEP
Zero-flow-phase
Decelarating flow
Pressure-time-diagram
Flow-time-diagram
Volume-time-diagram
PAW
inmbar
t in sec.
t in sec.
t in sec.
vt
inml
Vinl/min
Pressure ControlledVentilation
Tidal volume - vt
18
Ventilation
3 Basic ventilator settings
19
Ventilation
Volume controlled ventilation - Basic settingse.g. SIMV
FiO2
0,21-1,0
Vt ca.4-8 ml/kgBW
taken from the inspiration timeand the frequency theI:E-ratio is calculatedtinsp=2 sec ; f=10/min
I:E = 1:2
Flow =velocity of breathing gasca. 40 -60 l/min
positive endexpiratory pressureca. 7 - 15 mbarLungprotection / FRC-increase
20
Ventilation
Pressure controlled ventilation - Basic settingse.g. BIPAP
FiO2
0,21-1,0taken from the inspiration time
and the frequency theI:E-ratio is calculatedtinsp=2 sec ; f=10/min
I:E = 1:2
positive endexpiratory pressureca. 7 - 15 mbarLungprotection / FRC-increase
inspiration pressure - pinsp ca. 20-25 mbarvt depends on pressure difference to PEEP
C = ΔV ΔP
21
Ventilation
4 The model of density
22
Ventilation
Position of the diaphragmafter expiration
Position of the diaphragmafter inspiration
Mandatory ventilated patient in supinepositioning
23
Ventilation
25 cm
Modell of density of the human body
1 cm H2O 1 mbar
25 cm
0 cm
Thickness
Pressure0 mbar25 mbar
d =1kg/l
d =0,1 kg/l
d =0,2 kg/l
d =0,5 kg/l
d =0,8 kg/l
25 cm H2O
20 cm H2O12,5 cm H2O5 cm H2O
2,5 cm H2O
Risk of
overdistension
Risk of
atelectasis
Area of
increased ventilation
Area of
increased perfusion
d =1kg/l
d =0,1 kg/l
d =0,2 kg/l
d =0,5 kg/l
d =0,8 kg/l
24
Ventilation
5 Resistance,Compliance,Time constant
25
Ventilation
Compliance
26
Ventilation
p0
Compliance
Normal value - Adult
50-80 ml/mbar
27
Ventilation
Compliance
C=vp
28
Ventilation
Resistance
Normal value - Adult( intubated patient )
8-12 mbar/l/sec
29
Ventilation
Resistance
Law of Hagen-Poiseuille
The flow resistance through a tube with a defined lengthis dependent upon the viscosity of the medium flowingthrough and the fourth power of the tube radius.
In case of an intubated patient the endotracheal tube isa resistance because of the lower diameter in relation-ship to the trachea.
The resistance of the tube is reduced by 50 % when usinga tube with 8,0 mm ID instead of 7,5 mm ID.
30
Ventilation
36.8%
13.5%5.0% 1.8% 0.7%
36.8%
13.5%5.0% 1.8% 0.7%
0 1 2 3 4 5 6 R * C in sec.
0.24%
100%V0
*******Vt
************
Time constant
Filling and evacuation of functional compartment take placeexponentially.The volume is decreased by the same percentage within thesame time intervals. Above all, the important point is the fact that the duration ofexpiration is determined by the product of resistance and compliance.
R * C = t
31
Ventilation
0 1 2 3 4 5 6 R * C in sec.
V0
*******Vt
*******
R * C = t
Time constant - one more time
Pendel-Luft and air trapping
Air oscillates from the fast compartment to the slow ones until there is pressure equilibrium.
A certain volume remains trapped at the end ofexpiration, if the expiration phase does not last long enough = intrinsic PEEP.
32
Ventilation
6 Ventilation,Perfusion,Diffusion,Distribution
33
Ventilation
Ventilation
Expiration
Inspiration
Ventilation describes the process of inspi-ration and expiration - the transport ofbreathing gas between the alveoli and the atmosphere.
34
Ventilation
Shunt
Normal state
Shunt
Alveolar occlusion
If an alveolus is perfused but not ventilated, becauseit is blocked or collapsed - Atelectasis - the bloodwhich flows past it will not be oxygenated.As a result it is the so called intrapulmonary right-to-left-shunt.
35
Ventilation
Perfusion
Perfusion refers to the passage of blood through the capillaries of the lung, whereby carbon dioxide is transported to the alveolar membran and oxygen is taken to the pul-monary veins.Blood which is not enriched with oxygen - normaly 2 % - is described as shunt.
Pulmonary veinO2 CO2
Pulmonary arteryO2 CO2
36
Ventilation
Normal state
Dead space ventilation
Dead Space Ventilation
The alveolar areas which are ventilated but notperfused are described as the alveolar dead space,as no gas exchange can take place here.
37
Ventilation
Diffusion
Pulmonary arteryO2 CO2
Pulmonary veinO2 CO2
The process of gas exchange between the alveoli and the blood flow is known as diffusion. O2 and CO2 are diffusing because of the concentration gradient.
38
Ventilation
Distribution
The breathing gas is distributed throughoutthe different areas of the lung. It is importantfor the breathing gas to be as evenly distri-buted as possible.The distribution of the breathing gas and the pressure compensation occur on the gas con-ducting side, that is from the trachea and thebronchi to the alveoli and alveolar areas.
