Effects of a low tidal volume ventilation strategy on the pressure/volume curve in ALI/ARDS patients

To evaluate, in ARDS/ALI patients ventilated with a low tidal volume and PEEP, according to the NIH network trial [1], the effects on the parameters of the pressure/volume (PV) curve of the respiratory system.

Four ARDS/ALI sedated and paralyzed patients (age 62 ± 24 years, weight 66 ± 10 kg, PaO₂/FiO₂ 216 ± 70 mmHg, PEEP 12.7 ± 2.2 cmH₂O) were studied. P/V curves were performed at the beginning and after 120 min with the supersyringe technique. A recruitment maneuver was performed at the beginning of the study. Chest wall volume was measured by the optoelectronic plethysmography technique. Lower and upper inflection points (Pcl, Pcu), maximal compliance (C_max) and vital capacity (VC) on the inflation limb were computed according to Venegas' analysis [2]. Compliance at 100 ml (C_0.1), inflation compliance (C_inf), percentage hysteresis (Hyst%) and unrecovered volume (UV) were calculated using standard formulas [3]. In Table 1, the results are expressed as mean ± SD. These data suggest that after 2 hour ventilation with a low tidal volume strategy there are no major modifications in the P/V curve parameters.

Table 1