Physiology Flashcards
tidal volume (VT)
volume of normal breathing
0.5 L
inspiratory reserve volume (IRV)
additional amount of air that can enter during forced inspiration
expiratory reserve volume (ERV)
difference between tidal end volume and forceful expiration end volume
residual volume (RV)
amount of air remaining in the lung at max expiration
inspiratory capacity (IC)
VT + IRV
functional residual capacity (FRC)
ERV + RV
volume of air in the lungs after normal expiration
vital capacity (VC)
IC +ERV
volume that can be expired after max inspiration
total lung capacity (TLC)
VC + RV
includes all lung volumes
6-7 L
most sensitive test for restrictive lung disease
forced vital capacity (FVC)
TV + IRV + ERV
amount of air exhaled during a forceful expiration
forced expiratory volume in 1 second (FEV1)
max inspiration then forced expiration
normal is 80% of FVC
obstructive lung disease
FEV1: FVC ratio reduced: less than 70%
increased: TLC, RV, FRC
reduced: FVC, FEV1
difficult expiration: increased compliance, decreased Patm and Palv pressure: collapses airways on forced exhalation
ex: asthma, emphysema, chronic bronchitis, bronchiectasis
restrictive lung disease
reduced FVC, FEV1, TLC, RV, FRC
normal or increased FEV1: FVC ratio
difficult inspiration: decreased compliance, increased resistance
ex: obesity, weak inspiratory mescles, neuromuscular disorder, interstitial lung disease (fibrosis), ARDS, sarcoidosis, pneumonitis
atelectasis
unstable alveoli that collapse on expiration
Normal arterial PO2 and PCO2.
Normal venous PO2 and PCO2.
Normal alveolar PO2 and PCO2.
systemic arterial/ pulmonary venous: PO2: 100 PCO2: 40 systemic venous/ pulmonary arteries: PO2: 40 PCO2: 46 alveolar: PO2: 105 PCO2: 40
hypoventilation
increase in PACO2
hyperventilation
decrease PACO2
V/Q ratio for base and apex of lung
apex: high V/Q ratio (wasted ventilation)
base: low V/Q ratio (wasted perfusion)
What part of the lung is most perfused and has the most alveolar ventilation? least?
most perfused and alveolar ventilation: base
least perfused and alveolar ventilation: apex
A-a gradient for different causes of hypoxemia:
- hypoventilation
- decreased PIO2
- diffusion limitation
- R to L shunts
- V/Q mismatch
Which cannot be corrected by 100% O2?
- normal
- normal
- increased
- increased, NOT corrected with 100% O2
- increased
Decreased PIO2
- Example?
- A-a gradient increase? Intrinsic lung disease?
- Corrected with 100% O2?
- increased altitude
- A-a does NOT increase; no
- corrected with 100% O2
Hypoventilation
- Example?
- A-a gradient increase? Intrinsic lung disease?
- Corrected with 100% O2?
- drug overdose
- A-a does NOT increase; no
- corrected with 100% O2
Diffusion limitation
- Example?
- A-a gradient increase? Intrinsic lung disease?
- Corrected with 100% O2?
- pulmonary fibrosis, hard exercise, emphysema
- increased; yes
- yes
R to L Shunt
- Example?
- A-a gradient increase? Intrinsic lung disease?
- Corrected with 100% O2?
- ASD/VSD after pulmonary HTN reverses original L to R shunt; ARDS (alveolar flooding and collapse causes shunt)
- increased; yes
- NO
IMPORTANT: 100% oxygen should have a very large increase in PaO2: do the equation for A-a gradient to see if it is corrected
ex: PAO2= (760-47) x 1 - PaCO2/1
FiO2=1 at 100% O2
R= 1 at 100% O2
PaO2 should be in 600s; if not: shunt
V/Q mismatch
- example
- A-a gradient increase? Intrinsic lung disease?
- Corrected with 100% O2?
MOST COMMON cause of hypoxemia 1. emphysema, obstructive 2. increased; yes 3. yes normal whole lung V/Q: 0.8