ObjectiveTo determine the specific lung elastance (SE
L) in anesthetized dogs and to evaluate the efficacy of a SE
L-based recruiting airway pressure (
RPaw) at improving global and regional lung aeration.
Study designRetrospective and prospective clinical study.
AnimalsA total of 28 adult dogs were included in the retrospective study and six adult dogs in the prospective study.
MethodsRetrospective study: SE
L and SE
L-based
RPaw were determined using previously published data. In mechanically ventilated dogs undergoing thoracic computed tomography (CT), SE
L was calculated as Δ
PL/(V
T/EELV), where Δ
PL is the driving transpulmonary pressure, V
T is the tidal volume and EELV is the end-expiratory lung volume. The ratio of lung to respiratory system elastance (E
L/E
rs) was determined. SE
L and E
L/E
rs were used to calculate the SE
L-based
RPaw. Prospective study: dogs underwent thoracic CT at end-expiration and at end-inspiration using the SE
L-based
RPaw, and global and regional aeration was determined. For analysis of regional aeration, lungs were divided into cranial, intermediate and caudal regions. Regional compliance was also calculated. A
p value <0.05 was considered significant.
ResultsThe SE
L and E
L/E
rs were 12.7 ± 3.1 cmH
2O and 0.54 ± 0.07, respectively. The SE
L-based
RPaw was 29.1 ± 7.6 cmH
2O. In the prospective study, the
RPaw was 28.2 ± 1.3 cmH
2O. During
RPaw, hyperinflation increased (
p = 0.0003) whereas poorly aerated (
p < 0.0001) and nonaerated (
p = 0.01) tissue decreased. Normally aerated tissue did not change (
p = 0.265). Regional compliance was higher in the intermediate (
p = 0.0003) and caudal (
p = 0.034) regions compared with the cranial region. Aeration did not differ between regions (
p > 0.05).
Conclusions and clinical relevanceAn SE
L-based
RPaw reduces poorly and nonaerated lung tissue in anesthetized dogs. In nonsurgical anesthetized dogs, an
RPaw near 30 cmH
2O is effective at improving lung aeration.
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