Respective effects of end-expiratory and end-inspiratory pressures on alveolar recruitment in acute lung injury.
OBJECTIVE
A low tidal volume can induce alveolar derecruitment in patients with acute lung injury. This study was undertaken to evaluate whether this resulted mainly from the decrease in tidal volume or from the reduction in end-inspiratory plateau pressure and whether there is any benefit in raising the level of positive end-expiratory pressure (PEEP) while plateau pressure is kept constant.


METHODS
Prospective crossover study.


METHODS
Medical intensive care unit of a university teaching hospital.


METHODS
Fifteen adult patients ventilated for acute lung injury (PaO2/FiO2, 158 +/- 34 mm Hg; lung injury score, 2.7 +/- 0.6).


METHODS
Three combinations were tested: PEEP at the lower inflection point with 6 mL/kg tidal volume, PEEP at the lower inflection point with 10 mL/kg tidal volume, and high PEEP with tidal volume at 6 mL/kg, keeping the plateau pressure similar to the preceding condition.


RESULTS
Pressure-volume curves at zero PEEP and at set PEEP were recorded, and recruitment was calculated as the volume difference between both curves for pressures ranging from 15 to 30 cm H2O. Arterial blood gases were measured for all patients. For a similar PEEP at the lower inflection point (10 +/- 3 cm H2O), tidal volume reduction (10 to 6 mL/kg) led to a significant derecruitment. A low tidal volume (6 mL/kg) with high PEEP (14 +/- 3 cm H2O), however, induced a significantly greater recruitment and a higher Pao than the two other strategies.


CONCLUSIONS
At a given plateau pressure (i.e., similar end-inspiratory distension), lowering tidal volume and increasing PEEP increase recruitment and PaO2.
Richard
Jean-Christophe
JC
Medical Intensive Care Unit, Rouen University Hospital-Charles Nicolle, France.
Brochard
Laurent
L
Vandelet
Philippe
P
Breton
Lucie
L
Maggiore
Salvatore M
SM
Jonson
Bjorn
B
Clabault
Karine
K
Leroy
Jacques
J
Bonmarchand
Guy
G
D000328:Adult; D018592:Cross-Over Studies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods*; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000503:physiopathology*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics; D018709:Statistics, Nonparametric; D013990:Tidal Volume