Define respiratory compliance, include its components and their normal values (25% marks). Explain the factors that affect respiratory compliance (75% marks).
This question covers a core principle of respiratory physiology and would be expected to have a high pass rate. Most candidates were able to provide a concise definition and distinguish between the different types of compliance. The imprecise use of terminology often created the impression of a lack of fundamental understanding of this key concept. Candidates are encouraged to be accurate and concise in their definitions. A lack of detail in describing the relevant components of compliance and the factors that influence it, immediately limited the capacity of some candidates to achieve an adequate score. Most candidates provided less than half of these factors and only provided a list rather than explaining how compliance was impacted. Marks were maximised by dividing the impacts into those that altered lung compliance versus those that impacted on chest wall compliance, and the better candidates explained how and why compliance was affected. Confusion often arose from the imprecise use of arrows with the result that candidates frequently demonstrated an incorrect fact in relation to the direction of the arrow. Candidates are reminded to take care when using abbreviations or arrows to ensure they are not relying on the examiner to interpret a cause and effect relationship.
Factors which affect compliance can be divided into chest wall factors and lung factors:
|Lung compliance||Chest wall compliance|
Increased lung compliance
Increased chest wall complance
Decreased static lung compliance
Decreased dynamic lung compliance
Decreased chest wall compliance
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