A new simple method to perform pressure-volume curves obtained under quasi-static conditions during mechanical ventilation.

OBJECTIVE

To describe a fast, simple method to acquire pressure-volume curves of the respiratory system and to compare this with a classic method in terms of reliability of the data and speed.

DESIGN

Acquisition of pressure-volume curves by low flow inflation technique (P-Vlf) versus the occlusion technique (P-Vst) using the standard equipment of a Cesar ventilator.

SETTING

General ICU - Aix en Provence Hospital.

PATIENTS

Ten sedated, curarized patients undergoing mechanical ventilation.

INTERVENTIONS

P-Vlf curves were acquired by setting the ventilator parameters at f = 5 c./min, duty time Ti/Ttot = 80 %, VT = 1100 ml, pause time = 0. The pressure and volume data were collected directly on the ventilator screen. P-Vst curves were acquired using an airway occlusion technique. The pressures obtained for the same inflation volumes and times necessary for performance of the two techniques were compared.

RESULTS

The time needed to acquire a P-Vlf curve was 3 min versus 38 min for P-Vst curve. Concordance analysis between the two methods showed a 95 % confidence interval of (-0.5 cm H2O, + 1.8 cm H2O) for pressure.

CONCLUSIONS

P-Vlf curves are close to P-Vst curves, are much less time-consuming, easy to acquire with Cesar ventilator equipment, and may be used in clinical routine to assess the elastic properties of the respiratory system.