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

Abstract

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.