PEEP and compliance

 Q: Positive End Expiratory Pressure (PEEP) _____________ the lung compliance (select one)

A) decreases 

B) increases 

Answer: B

In the diseased lungs, functional residual capacity (FRC) is decreased. FRC as the name applies is the air volume that stays in the lung at the end of expiration. It is determined by the elasticity of the alveoli and chest wall. 

PEEP increases the surface area by reopening the collapsed alveoli. The already partially inflated lung requires less volume and energy in subsequent breaths. This improves compliance. 

Said that, it requires a determination of "optimum PEEP" to find the best compliance.

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References:

1. Smith TC, Marini JJ. Impact of PEEP on lung mechanics and work of breathing in severe airflow obstruction. J Appl Physiol (1985). 1988 Oct;65(4):1488-99. doi: 10.1152/jappl.1988.65.4.1488. PMID: 3053583.

2. Ben Azzouz, R.; Kumba, C.; Itani, O.; Massaut, J. Effect of PEEP on pulmonary compliance and functional residual capacity in cardiac sugery patients during the postoperative period European Journal of Anaesthesiology: June 2004 - Volume 21 - Issue - p 80 European Journal of Anaesthesiology: June 2004 - Volume 21 - Issue - p 80