Study objectives: To determine the effects of
different levels of positive end-expiratory pressure (PEEP) during
partial liquid ventilation (PLV) on gas exchange, lung compliance, and
end-expiratory lung volume (EELV).
Setting: Animal physiology research
Subjects: Nine piglets.
Interventions: Animals underwent saline solution lavage to
produce lung injury. Perflubron was instilled via the endotracheal tube
in a volume estimated to represent functional residual capacity. The
initial PEEP setting was 4 cm H2O, and stepwise changes in
PEEP were made. At 30-min intervals, the PEEP was increased to 8, then
12, then decreased back down to 8, then 4 cm H2O.
Measurements and results: After 30 min at each level of
PEEP, arterial blood gases, aortic and central venous pressures, heart
rates, dynamic lung compliance, and changes in EELV were recorded.
Paired t tests with Bonferroni correction were used to
evaluate the data. There were no differences in heart rate or mean BP
at the different PEEP levels. CO2 elimination and
oxygenation improved directly with the PEEP level and mean airway
pressure (Paw). Compliance did not change with increasing PEEP, but did
increase when PEEP was lowered. EELV changes correlated directly with
the level of PEEP.
Conclusions: As previously reported
during gas ventilation, oxygenation and CO2 elimination
vary directly with PEEP and proximal Paw during PLV. EELV also varies
directly with PEEP. Dynamic lung compliance, however, improved only
when PEEP was lowered, suggesting an alteration in the distribution of
perflubron due to changes in pressure-volume