Effects of 12 and 17 cmH2O positive end-expiratory pressure applied after alveolar recruitment maneuver on pulmonary gas exchange and compliance in isoflurane-anesthetized horses.

The study investigates the effects of different positive end-expiratory pressures (PEEP) applied after an alveolar recruitment maneuver (RM) on oxygen tension difference and lung compliance in anesthetized horses. The results indicated that only a PEEP of 12 cmH2O was able to maintain improvements on both parameters after an RM.

Background

• The study focuses on understanding the impacts of different levels of positive end-expiratory pressure (PEEP) – 7, 12, and 17 cmH2O, deployed post an alveolar recruitment maneuver (RM) in horses undergoing anesthesia.
• This research was motivated by the objective to find out how different PEEP post RM could influence the static compliance (a measure of the ability of a hollow organ to distend and increase volume with increasing transliminal pressure or gradually decreasing pressure) and alveolar-arterial oxygen tension difference (a measure of gas exchange across the lung).

Methodology

• A prospective, randomized, clinical study was conducted with a group of 30 healthy adult horses undergoing arthroscopic surgery.
• The horses were in dorsal recumbency and mechanically ventilated, and were exposed to an RM by systematically increasing and decreasing the PEEP levels.
• The parameters – static compliance (C) and alveolar-arterial oxygen tension difference (P(a-a)O) – were assessed before (baseline) as well as after RM at set intervals and during recovery from anesthesia.

Findings

• Post RM, substantial improvements were observed in P(a-a)O in horses where PEEP of 12 (RM12) and 17 (RM17) cmH2O was used.
• However, enhancements in lung compliance were only sustained in horses with a PEEP of 12 cmH2O (RM12).
• Neither the PEEP of 7 cmHO (RM7) nor the control group showed these improvements.
• No significant differences were observed between the groups during recovery from anesthesia.

Conclusions and Clinical Relevance

• Both 12 and 17 cmHO PEEP effectively maintained the improvements in P(a-a)O achieved after an RM.
• However, only a PEEP of 12 cmHO was able to maintain the enhancement in lung compliance post-RM.
• The observations from this study inferred that the 7 cmHO PEEP, on the other hand, did not influence these variables of interest.