Comparison of high-frequency oscillation and tracheal gas insufflation versus standard high-frequency oscillation at two levels of tracheal pressure
In acute respiratory distress syndrome (ARDS), combined high-frequency oscillation (HFO) and tracheal gas insufflation (TGI) may improve oxygenation through a TGI-induced increase in mean tracheal pressure (P tr). We compared standard HFO and HFO-TGI matched for P tr, in order to determine whether TGI affects gas exchange independently from P tr. We conducted a prospective, randomized, crossover, physiological study in a 37-bed intensive care unit. Twenty-two patients with early acute lung injury (ALI) or ARDS were enrolled. On day 1, patients were ventilated with HFO, without (60 min) and combined with TGI (60 min) in random order. HFO/HFO-TGI sessions were repeated in inverse order within 7 h. HFO/HFO-TGI mean airway pressure (P aw) was titrated to a P tr that was either equal to (low P aw) or 3 cmH2O higher than (high P aw) the P tr of the preceding conventional mechanical ventilation. On day 2, the protocol was repeated at the alternative P tr level relative to day 1. Gas exchange and hemodynamics were determined before, during, and after HFO/HFO-TGI sessions. HFO-TGI-high P aw versus HFO-high P aw resulted in significantly higher PaO2/inspired O2 fraction (FiO2) [mean ± standard error of the mean (SEM): 281.6 ± 15.1 versus 199.0 ± 15.0 mmHg; mean increase: 42%; P < 0.001]. HFO-TGI-low P aw, versus HFO-low P aw, resulted in significantly higher PaO2/FiO2 (222.8 ± 14.6 versus 141.3 ± 8.7 mmHg; mean increase: 58%; P < 0.001). PaCO2 was significantly lower during HFO-TGI-high P aw versus HFO-high Paw (45.3 ± 1.6 versus 53.7 ± 1.9 mmHg; mean decrease: 16%; P = 0.037). At the same P tr level, HFO-TGI results in superior gas exchange compared with HFO.