Gas exchange, specific lung elastance and mechanical power in the early and persistent ARDS

Abstract

PurposeAim of this study was to evaluate the effect of acute respiratory distress syndrome (ARDS) duration on gas-exchange, respiratory mechanics, specific lung elastance and mechanical power. Materials and methodsIn a single center prospective study 28 ARDS patients (66.4 ± 10.0 years, BMI 23.6[21.3–28.8] kg/m2, PaO2/FiO2 148.9[99.6–173.5]) who still presented ARDS criteria after 7-days of mechanical ventilation were studied in early and persistent phase of the disease (day-1 and after 7-days). Each patient underwent PEEP trial at 5–15 cmH2O in both phases. ResultsAt both PEEP levels the PaO2 was similar in both phases (early: 70.7[65.1–84.4] vs 102.0[85.5–131.8] mmHg; persistent 70.7[63.0–76.2] vs 97.4[86.5–117.1] mmHg, 5–15 cmH2O respectively), the PaCO2 was significantly higher in the persistent phase at both PEEP levels (early 50.6 ± 10.2 vs 52.1 ± 10.5 mmHg; persistent 57.7 ± 13.4 vs 56.9 ± 12.8 mmHg). Specific lung elastance was not different in the early compared to the persistent phase 12.5 ± 3.1 vs 12.2 ± 3.8 cmH2O. The mechanical power normalized for the functional residual capacity increased with PEEP and was similar in both phases (early 23.4[12.8–32.8] vs 34.3[25.3–47.9], persistent 16.3[10.9–24.1] vs 26.7[19.9–46.0] J/min/L, 5–15 cmH2O respectively). ConclusionsThe persistent phase of ARDS for 7-days did not affect the respiratory mechanics while significantly impaired the PaCO2 exchange.