Physiological Consequences of Lung Disease Flashcards
(39 cards)
What are the four main physiological processes involved in respiration?
Respiratory drive, ventilation, diffusion (gas exchange), and perfusion.
How is minute ventilation calculated?
Minute ventilation = Tidal volume x respiratory rate.
How is alveolar ventilation calculated?
Alveolar ventilation = (Tidal volume – dead space) x respiratory rate.
Which process is active: inspiration or expiration?
Inspiration is active; expiration is passive at rest but active with increased drive.
What does lung compliance refer to?
The change in pressure required to produce a change in lung volume.
What is ventilatory capacity?
The maximum spontaneous ventilation maintainable without respiratory muscle fatigue.
What is ventilatory demand?
The spontaneous minute ventilation required to maintain normal PaCO₂.
According to Fick’s Law, what factors increase the rate of gas diffusion?
Larger surface area and greater partial pressure difference; decreased tissue thickness.
How does CO₂ diffusion compare to O₂ diffusion?
CO₂ diffuses 20 times faster than O₂.
What is the normal thickness of the blood-gas barrier in the lungs?
About ½ micron.
What is the alveolar surface area available for gas exchange?
50–100 square meters.
Where is lung perfusion greatest when upright?
At the lung bases.
What is hypoxic pulmonary vasoconstriction?
Constriction of pulmonary vessels in poorly ventilated lung areas to redirect blood flow.
What happens with reduced ventilation but normal perfusion?
Physiological shunt → deoxygenated blood enters systemic circulation.
What happens with normal ventilation but reduced perfusion?
Alveolar dead space → wasted ventilation.
What does TLCO/DLCO measure?
The transfer factor of the lungs, reflecting diffusion capacity.
What does a reduced DLCO indicate?
Impaired gas exchange due to thickened alveolar membrane.
What imaging is used to assess pulmonary perfusion?
CT pulmonary angiogram.
What does a pulse oximeter measure?
Indirect measurement of arterial oxygen saturation.
When is an arterial blood gas (ABG) indicated?
When O₂ saturation falls below 90–92%.
What PaO₂ corresponds to about 90% hemoglobin saturation?
Approximately 8 kPa.
What pH indicates acidaemia?
pH < 7.35.
What pH indicates alkalaemia?
pH > 7.45.
What causes respiratory acidosis?
Elevated CO₂ (hypoventilation).
