Early patterns of static pressure-volume loops in ARDS and their relations with PEEP-induced recruitment.
OBJECTIVE
Evaluation of low-flow pressure-volume loop at the bedside in ARDS, as an aid to assess recruitment produced by PEEP.


METHODS
Low-flow pressure-volume loop at the bedside were obtained on the first day of respiratory support in 54 successive pulmonary ARDS patients (49 of whom had pneumonia) treated between April 1999 and June 2002. From the loop obtained at ZEEP, we determined manually the lower inflexion point (LIP). By superimposing the pressure-volume loop at ZEEP and at PEEP, we evaluated recruitment obtained at a constant elastic pressure of 20 cm H2O.


RESULTS
We observed two different types of loops, according to the pattern of the inflation limb. In type 1 (38 cases) the inflation limb was characterized by an inflexion zone, resulting from a progressive or a sudden improvement in compliance. In type 2 (16 patients) the inflation limb was virtually linear, without significant improvement in compliance during inflation, which remained particularly low (26+/-9 cm H2O). Use of a low PEEP (6+/-2 cm H2O) produced a substantial recruitment in type-1 patients (74+/-53 ml), which was marginally improved by a higher PEEP (89+/-54 ml). In type 2, recruitment produced by PEEP was significantly lower (48+/-26 ml, p=0.006).


CONCLUSIONS
Pressure-volume loop at bedside confirmed that a low PEEP was sufficient to obtain recruitment in ARDS. This study also individualized a group of pulmonary ARDS patients exhibiting a markedly reduced compliance, in whom recruitment obtained by PEEP was limited.
Vieillard-Baron
Antoine
A
Medical Intensive Care Unit, University Hospital Ambroise Paré, Assistance Publique Hôpitaux de Paris, 9 avenue Charles de Gaulle, 92104, Boulogne Cedex, France.
Prin
Sebastien
S
Chergui
Karim
K
Page
Bernard
B
Beauchet
Alain
A
Jardin
François
F
D000368:Aged; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D003422:Critical Care / Q000379:methods; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D008170:Lung Compliance; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D019095:Point-of-Care Systems; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics; D012720:Severity of Illness Index; D013147:Spirometry; D013990:Tidal Volume; D013997:Time Factors; D016896:Treatment Outcome