Tidal volume lower than 6 ml/kg enhances lung protection: role of extracorporeal carbon dioxide removal.

Background: Tidal hyperinflation may occur in patients with acute respiratory distress syndrome who are ventilated with a tidal volume (V-T) of 6 ml/kg of predicted body weight develop a plateau pressure (P-PLAT) of 28 <= P-PLAT <= 30 cm H2O. The authors verified whether V-T lower than 6 ml/kg may enhance lung protection and that consequent respiratory acidosis may be managed by extracorporeal carbon dioxide removal. Methods: P-PLAT, lung morphology computed tomography, and pulmonary inflammatory cytokines (bronchoalveolar lavage) were assessed in 32 patients ventilated with a V-T of 6 ml/kg. Data are provided as mean +/- SD or median and inter-quartile (25th and 75th percentile) range. in patients with 28 :5 P-PLAT <= 30 cm H2O (n = 10), V-T was reduced from 6.3 +/- 0.2 to 4.2 +/- 0.3 ml/kg, and P-LAT decreased from 29.1 +/- 1.2 to 25.0 +/- 1.2 cm H2O (P < 0.001); consequent respiratory acidosis (Paco(2) from 48.4 +/- 8.7 to 73.6 +/- 11.1 mmHg and pH from 7.36 +/- 0.03 to 7.20 +/- 0.02; P < 0.001) was managed by extracorporeal carbon dioxide removal. Lung function, morphology, and pulmonary inflammatory cytokines were also assessed after 72 h. Results: Extracorporeal assist normalized Paco(2) (50.4 +/- 8.2 mmHg) and pH (7.32 +/- 0.03) and allowed use of V-T lower than 6 ml/kg for 144 (84-168) h. The improvement of morphological markers of lung protection and the reduction of pulmonary cytokines concentration (P < 0.01) were observed after 72 h of ventilation with V-T lower than 6 ml/kg. No patient-related complications were observed. Conclusions: V-T lower than 6 ml/Kg enhanced lung protection. Respiratory acidosis consequent to low V-T ventilation was safely and efficiently managed by extracorporeal carbon dioxide removal.