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

OBJECTIVE

To compare static compliance (C) and alveolar-arterial oxygen tension difference [P(a-a)O] between positive end-expiratory pressures (PEEP) of 7, 12 and 17 cmHO applied after an alveolar recruitment maneuver (RM) in isoflurane-anesthetized horses.

STUDY DESIGN

Prospective, randomized, clinical study.

ANIMALS

A group of 30 healthy adult horses undergoing arthroscopic surgery.

METHODS

Animals in dorsal recumbency and mechanically ventilated with a tidal volume of 14 mL kg and 7 cmHO PEEP (control; n = 6) were subjected to an RM by increasing PEEP from 7 to 22 cmHO in 5 cmHO increments at 5 minute intervals, and then decreased similarly to PEEP of 17 (RM17; n = 8), 12 (RM12; n = 8) or 7 cmHO (RM7; n = 8). C and P(a-a)O were assessed prior to (baseline) and after the RM at 5, 10, 15, 20, 40, 60 and 80 minutes after achieving each target PEEP, and during recovery from anesthesia.

RESULTS

Post-RM improvements on P(a-a)O were maintained (baseline versus 80 minutes) in RM12 [216 ± 77 mmHg (28.8 ± 10.3 kPa) versus 194 ± 39 mmHg (25.9 ± 5.2 kPa)] and RM17 [180 ± 86 mmHg (24.0 ± 11.6 kPa) versus 136 ± 75 mmHg [18.2 ± 10.0 kPa]). The improvements on C were maintained only in RM12 (0.80 ± 0.13 versus 0.98 ± 0.13 mL cmHO kg). No such improvements were observed in RM7 and control. No significant differences were observed between groups during recovery from anesthesia.

CONCLUSIONS

and clinical relevance The 12 and 17 cmHO PEEP can be used to maintain the improvements on P(a-a)O obtained after an RM. Only 12 cmHO PEEP maintained the post-RM increase on C. Such variables were not influenced by the 7 cmHO PEEP.