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^?1 and 7 cmH₂O PEEP (control; n = 6) were subjected to an RM by increasing PEEP from 7 to 22 cmH₂O in 5 cmH₂O increments at 5 minute intervals, and then decreased similarly to PEEP of 17 (RM17; n = 8), 12 (RM12; n = 8) or 7 cmH₂O (RM7; n = 8). C_st and P(a–a)O₂ 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)O₂ 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_st were maintained only in RM12 (0.80 ± 0.13 versus 0.98 ± 0.13 mL cmH₂O^?1 kg^?1). 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 cmH₂O PEEP can be used to maintain the improvements on P(a–a)O₂ obtained after an RM. Only 12 cmH₂O PEEP maintained the post-RM increase on C_st. Such variables were not influenced by the 7 cmH₂O PEEP.