Recruitment manoeuvres aim at reversing atelectasis during general anaesthesia but are associated with potential risks such as barotrauma.
To explore the range of pressures that can be used safely to fully recruit the lung without causing barotrauma in an ex-vivo healthy lung rabbit model.
Prospective, randomised, experimental study.
Experimental Unit, La Paz University Hospital, Madrid, Spain.ANIMALSFourteen healthy young New Zealand rabbits of 12 weeks of age.
Animals were euthanised, the thorax and both pleural spaces were opened and the animals were allocated randomly into one of two groups submitted to two distinct recruitment manoeuvre strategies: PEEP-20 group, in which positive end-expiratory pressure (PEEP) was increased in 5-cmH(2)O steps from 0 to 20cmH(2)O and PEEP-50 group, in which PEEP was increased in 5-cmH(2)O steps from 0 to 50cmH(2)O. In both groups, a driving pressure of 15cmH(2)O was maintained until maximal PEEP and its corresponding maximal inspiratory pressures (MIPs) were reached. From there on, driving pressure was progressively increased in 5-cmH(2)O steps until detectable barotrauma occurred. Two macroscopic conditions were defined: anatomically open lung and barotrauma.
MAIN OUTCOME MEASURES
We measured open lung and barotrauma MIP, PEEP and driving pressure obtained using each strategy. A pressure safety range, defined as the difference between barotrauma MIP and anatomically open lung MIP, was also determined in both groups.RESULTSOpen lung MIP was similar in both groups: 23.63.8 and 23.3 +/- 4.1cmH(2)O in the PEEP-50 and PEEP-20 groups, respectively (P=0.91). However, barotrauma MIP in the PEEP-50 group was higher (65.7 +/- 3.4cmH(2)O) than in the PEEP-20 group (56.7 +/- 5 0.2cmH(2)O) (P=0.003) resulting in a safety range of pressures of respectively 33.3 +/- 8.7 and 42.1 +/- 3.9cmH(2)O (P=0.035).
In this ex-vivo model, we found a substantial difference between recruitment and barotrauma pressures using both recruitment strategies. However, a higher margin of safety was obtained when a higher PEEP and lower driving pressure strategy was used for recruiting the lung.
2013. Vol. 30, no 9, 567-574 p.