MEDICAL
LUNGS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Palv
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Patm
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Either A or B
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None of the above
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Detailed explanation-1: -Alveolar pressure (PA or Palv) [ intrapulmonary pressure or lung pressure] Alveolar pressure normally changes as the intrapleural pressure changes. During spontaneous inspiration, PA is about −1 cm H2O, and during exhalation it is about +1 cm H2O.
Detailed explanation-2: -Intraalveolar pressure is the pressure inside the alveoli of the lungs. Intrapleural pressure is the pressure within the pleural cavity. These three pressures are responsible for pulmonary ventilation.
Detailed explanation-3: -Partial pressures The alveolar oxygen partial pressure is lower than the atmospheric O2 partial pressure for two reasons. Firstly, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour (47 mmHg) reduces the oxygen partial pressure to about 150 mmHg.
Detailed explanation-4: -Up to middle age, breathing ambient air, normal P(A-a)O2 ranges between 5 and 20 mm Hg.