Study objectives: Evaluation of the effectiveness of negative-pressure ventilation (NPV) with the use of the iron lung vs noninvasive positive-pressure ventilation (NIPPV) in the treatment of COPD patients with acute on chronic respiratory failure.
Design: A retrospective case-control study.
Setting: Four Italian respiratory intermediate ICUs.
Patients: Of a total of 393 COPD patients admitted to the ICU in 1996, 53 pairs were treated with the iron lung (NPV group). Patients treated with NIPPV (NIPPV group) were matched according to mean (+/- SD) age (70.3 +/- 7.1 vs 70.3 +/- 6.9 years, respectively), sex, causes of acute respiratory failure (ARF), APACHE (acute physiology and chronic health evaluation) II score (22.4 +/- 5.3 vs 22.1 +/- 4.6, respectively), pH (7.26 +/- 0.05 vs 7.27 +/- 0.04, respectively), and PaCO(2) (88.1 +/- 11.5 vs 85.1 +/- 13.5 mm Hg, respectively) on admission to the ICU. The effectiveness of matching was 98.4%.
Results: Five patients from the NPV group (9.4%) and seven patients from the NIPPV group (13.2%) needed endotracheal intubation (EI). The treatment failure rate (ie, death and/or need of EI) was 20.7% in the NPV group and 24.5% in the NIPPV group (difference was not significant). The mean duration of mechanical ventilation (29.6 +/- 28.6 vs 62.3 +/- 35.7 h, respectively) and length of hospital stay (10.4 +/- 4.3 vs 15 +/- 5.2 d, respectively) among the 35 concordant surviving pairs were significantly lower in the NPV group than in the NIPPV group (p = 0.001 and p = 0.001, respectively).
Conclusions: These data suggest that both ventilatory techniques are equally effective in avoiding EI and death in COPD patients with ARF. Prospective trials are needed to confirm these preliminary results.