Respiratory Physiology
Ventilation, perfusion, gas exchange, mechanics, control of breathing, oxygen transport and applied respiratory physiology.
How to prepare for the current Primary FRCA MCQ
Build mechanisms first, practise calculations with units, connect equipment to failure modes and finish every SBA by choosing the single best answer to the exact lead-in.
Core concepts
Concept 1
Alveolar ventilation, resistance, compliance and time constants determine carbon dioxide clearance and regional lung filling.
Exam cue: Distinguish oxygen tension, saturation and content.
Concept 2
Ventilation–perfusion relationships, shunt, diffusion and haemoglobin binding determine oxygen transfer and arterial content.
Exam cue: Separate hypoventilation, V/Q mismatch, shunt and diffusion limitation before predicting response to oxygen.
Risk pitfalls and guardrails
Using minute ventilation when a dead-space change makes alveolar ventilation the relevant variable.
Guardrail: Do not choose an option merely because it states a true fact; choose the one that best answers the exact lead-in under the stated conditions.
Treating pulse oximetry as a direct measure of ventilation.
Guardrail: Do not choose an option merely because it states a true fact; choose the one that best answers the exact lead-in under the stated conditions.
Memory anchors
What is alveolar ventilation?
Respiratory rate multiplied by tidal volume minus dead space: fresh gas reaching gas-exchanging alveoli per minute.
What sets a respiratory time constant?
Resistance multiplied by compliance.
What is physiological shunt?
Venous blood reaching the arterial circulation without contact with ventilated alveoli.
What shifts the oxyhaemoglobin curve?
Temperature, pH, carbon dioxide and 2,3-DPG alter haemoglobin affinity.
Why does anaesthesia promote atelectasis?
Reduced FRC, altered mechanics, positioning, high inspired oxygen and loss of muscle tone can close dependent lung units.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is tidal volume?
Which lung volume cannot be measured directly by simple spirometry?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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