Exam 2, L3 Flashcards
(34 cards)
What is the partial pressure of water vapor in inspired air at body temperature?
47 mmHg at 37°C.
How does water vapor affect inspired O₂ pressure?
It displaces O₂, reducing inspired PO₂ from 159 mmHg to about 149 mmHg.
What is the equation for inspired oxygen pressure (PIO₂)?
PIO₂ = FIO₂ × (Patm − PH₂O)
What are normal values for pulmonary arterial blood?
PO₂ ≈ 40 mmHg, PCO₂ ≈ 45 mmHg.
What are normal values for systemic arterial blood?
PO₂ ≈ 100 mmHg, PCO₂ ≈ 40 mmHg.
Why does arterial PO₂ decrease with age?
Due to decreased lung elasticity and gas exchange efficiency — typically declines after age 20.
What is bronchiolar admixture and how does it affect PaO₂?
Systemic bronchial circulation returns slightly deoxygenated blood to pulmonary veins, reducing PaO₂ by a few mmHg.
What is anatomical dead space?
Air in the conducting airways (≈150 mL) that does not participate in gas exchange.
What is alveolar dead space?
Alveoli that are ventilated but not perfused — often due to disease or embolism.
What is physiologic dead space?
The sum of anatomical + alveolar dead space.
How does dead space change with age?
Alveolar dead space increases due to loss of perfusion and elastic recoil.
What is tidal volume (VT) in a healthy adult?
500 mL per breath.
How much of a tidal breath is used for gas exchange?
About 350 mL.
How much is anatomical dead space in a tidal breath?
150 mL.
What is minute ventilation (VE)?
VE = VT × RR = 500 × 12 = 6 L/min.
What is alveolar ventilation (VA)?
VA = (VT − deadspace) × RR = (500 − 150) × 12 = 4.2 L/min.
What is dead space ventilation per minute?
VD = 150 × 12 = 1.8 L/min.
What is the normal alveolar PO₂ and PCO₂ at rest?
PO₂ ≈ 104 mmHg, PCO₂ ≈ 40 mmHg.
What happens to alveolar PO₂ with increased ventilation?
It increases — more fresh air dilutes alveolar gases.
What happens to alveolar PCO₂ with hyperventilation?
It decreases — more CO₂ is exhaled.
What happens to alveolar PO₂ and PCO₂ with hypoventilation?
PO₂ decreases, PCO₂ increases — poor gas exchange.
What is pulmonary capillary hydrostatic pressure?
About 7 mmHg.
What is interstitial hydrostatic pressure in the lungs?
–8 mmHg, due to pleural pressure and lymphatic suction.
What is the interstitial oncotic pressure in the lungs?
About 14 mmHg — higher than systemic tissues.
