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46 Cards in this Set

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Equation and normal value for tidal volume
VT = VE/RR

Norm = 500ml
Peak Inspiratory Pressure
Direct measure.

Norm = 10-100 cmH2O
What happens during inspiration?
diaphragm and chest muscles contract --> increase intrathoracic volume & decrease intrathoracic pressure-->air moves down the gradient and into the lungs
What happens during expiration?
Passive. Muscles relax, lungs recoil --> decrease intrapulmonary volume & increase intrapulmonary pressure --> air moves out of lungs
Perfusion zones:
zone 1
zone 2
zone 3
zone 1- low flow Pa<PA>Pv

zone 2 - Pa>PA>Pv

zone 3 - Pa>PA<Pv
Plateau Pressure
direct measure

<30 cmH2O
Airway resistance
Raw= (PIP-Pplat)/Flow

opposition of flow of gas.
What causes increased airway resistance?
small ETT
mucous plug
water in vent tubing
pt biting on the tube
high flow rate
What is the truest measure of lung compliance?

Define it.
Static Compliance. It reflects the elastic recoil of the lungs. Must use a breath hold maneuver.

Cst=exhaled VT/(Pplat-PEEP)

norm= 70-100 ml/cmH2O
What is dynamic compliance?
exhaled VT/(PIP-PEEP)
norm = 50-80 ml/cmH2O

measures distensibility of lung and its resistance to gas flow.
Why is dynamic compliance always smaller than static compliance?
because PIP is higher than plateau pressure.
a/A ratio
arterial-alveolar ratio = PaO2/PAO2

norm = 0.8

Low a/A ratio (<0.6)=shunt, V/Q mismatch or diffusion defect
What is the measure for preload in the right and left heart?
right heart: CVP, RAP, RVEDP, RVEDV

left heart: PAWP, LVEDP, LVEDV
What is the measure for afterload in the right and left heart?
right: PVR, PVRI
PVR=pulmonary vascular resistance

left: SVR, SVRI
PaO2/FiO2 ratio
reflects the status of oxygenation

norm = 550 mmHg
A-a gradient
PAO2-PaO2

indicates efficacy of gas exchange.
arterial oxygen content
CaO2 = (Hgb x 1.36 x SaO2) + (PaO2 x .0031)

norm = 19-20 ml/dl
What causes an increase in CaO2?
any conditions that increase Hgb, SaO2 and PaO2
What is oxygen delivery?

When is it decreased?
DO2 = CaO2 x CO x 10
norm = 1000ml/min

Decreased with decreased CO as in heart failure or valve disease, decreased Hgb as in anemia.
What is oxygen consumption?
VO2 = CO x (CaO2-CvO2) x 10

norm = 200-250 ml/min

The amount of O2 used by the tissues in one minute.
What would cause an increase in VO2?
increase oxygen demand as with exercise, fever, increased CO, shivering
What is oxygen extraction?
The difference between arterial and venous oxygen concentrations. It is the amount of oxygen used by the tissues.
norm = 4-6 ml/dl
What are the normal ABG parameters?
pH = 7.35-7.45
PCO2 = 35-45
PO2 = 80-100
HCO3 = 22-26
BE = +/- 2
O2sat= 95-100%
Name some conditions that result in a left shift in the oxyhemoglobin dissociation curve?
hypothermia, chronic acidosis, multiple transfusions (decreased 2,3 DPG)
Normal Hgb and Hct values.
Hgb: males 13-18 gm/dl
females 12-16 gm/dl

Hct: males 39-55%
females 36-48%
What is Qs/Qt?
It is the amount of blood passing through the lungs and not coming into contact with ventilated lung tissue...no gas exchange occurring.
Normal is 3-5%
What can cause an increased CVP?
Increases in preload such as hypervolemia,tricuspid insuff.

Increases in afterload such as ARDS, COPD, LVF, PE
What can cause an increased PAWP?
hypervolemia, LVF, pneumothorax, cardiac tamponade
What's the significance of arterial-venous O2 content difference (Ca-vO2)?
It represents tissue O2 consumption and estimates CO.

If Ca-vO2 is increased, then CO is decreased or metabolism has increased.

If Ca-vO2 is decreased, then CO is increased or metabolism is decreased.
O2ER
O2 Extraction Ratio

Norm = 25%

indicator of O2 supply/demand.
cardiac output
CO = SV x HR

norm = 4-8 L/min

indicates pump efficacy and is a determinant in tissue perfusion.
True or False

Plateau pressure is always lower then peak inspiratory pressure.
True.
What is PEEP and why do we use it?

Do all vented patients require PEEP?
PEEP is positive end expiratory pressure, the airway pressure in the lungs at end-expiration that aid in maintaining the alveoli open. PEEP is applied to vented patients to increase oxygenation and aid in alveoli recruitment.

All vented patients need PEEP.
What are some complications of a high PEEP?
decreased CO,
increased chest pressure at end expiration,
increased intrapulmonary shunting,
barotrauma resulting in decreased lung compliance
How is oxygen carried in the blood?
O2 is dissolved in the plasma (PaO2).

O2 is bound to Hgb (SaO2)
List causes for a low SvO2.
1. decreased O2 supply to the tissues as in low Hgb, hemorrage, or low CO.

2. increased O2 use by the tissue as in fever, pain, stress.
What are the components of oxygen delivery?
Oxygen dissolved in plasma (PaO2); oxygen bound to Hgb (SaO2); delivered by work of heart (CO).

So, CaO2 x CO x 10

norm = 1000 ml/min
How much delivered O2 is used by the tissue under normal circumstances?
25%

Therefore if DO2 is 1000ml/min, 25% of that is 250 ml/min, the amount of O@ consumed by tissue or VO2.
What is an easy way to estimate PaO2 based on patient's age?
PaO2 = 110 - 1/2 pt's age

normal should be 80-100 mmHg
What is the significance of SvO2?
It is an early indicator of a threat to tissue oxygenation. Normal is about 75% which means 25% O2 has been used by the tissues and 75% is in reserve for times of increased need.
What parameters are used to assess the adequacy of oxygenation?

Be able to define each.
PaO2 & PvO2
CaO2 & CvO2
SaO2 & SvO2
What parameters are used to assess efficiency of oxygenation?

Be able to define each.
PaO2/PAO2 ratio
PaO2/FiO2 ratio
Qs/Qt
O2ER
DO2
VO2
What are the normal pulmonary pressures during systole, diastole and mean?
SBP 15-25 mmHg

DBP 8-15 mmHg

mean 10-20 mmHg
What is the significance of the A-a gradient?

What factors increase it?
A-a gradient (aka anatomic shunt) is a method to analyze efficacy of oxygen diffusion. The greater the gradient the greater the diffusion defect. Factors that can increase the defect are atelectasis, pulmonary edema, pneumonia
What is PAO2/PaO2 ratio?

List components, norms, causes of increase and decrease.
PaO2/PAO2 norm = 0.8
this is an estimation of intrapulmonary shunting. A decrease in the ratio indicates a greater shunt. Causes are atelectasis, PE, pulmonary edema. An increase in the ratio would be caused by an improvement in any of the disease processes that decrease the ratio.
PaO2/FiO2
This is an estimate of intrapulmonary shunting. Norm = 550.
For every 100 mmHg there is a 5% shunt. Anything that causes injury or inflammation to the lung will cause shunting, such as ARDS, PE, aspiration.