FLORENCE, ITALY —The iron lung can still be used and appears to work as well as noninvasive positive-pressure ventilation (NIPPV) administered through a mask. That is what Italian investigators discovered when they compared the two treatments in patients with chronic obstructive pulmonary disease (COPD) and acute respiratory failure (ARF).[1]

Their study, the first formal comparison of two different noninvasive ventilatory techniques in this group of patients, showed that treatment with the iron lung prevented endotracheal intubation and death as effectively as did that with NIPPV. Furthermore, the median intensive care unit (ICU) stay and duration of mechanical ventilation were much shorter for the group treated with the iron lung.

GROUPS WERE CLOSELY MATCHED

Close patient matching of the iron lung and NIPPV groups was crucial for study validity because it minimized the effect of important confounders, especially age, sex, causes of ARF, APACHE II score, and arterial carbon dioxide tension levels. Among 393 COPD patients admitted to a respiratory intermediate ICU for ARF, researchers selected 53 pairs that were closely matched for these variables. “The effectiveness of matching was 98.4%,” the investigators noted.

In each pair, one patient was continuously treated with the iron lung and the other with NIPPV for at least four to six hours. The iron lung was set to deliver 30 to 40 cm H2O of negative pressure followed by 10 to 15 cm H2O of positive pressure at a frequency of 15 cycles per minute.

The patients in the NIPPV group received pressure-assisted control or pressure support ventilation through a face or nasal mask. The mean pressures delivered during inspiration and expiration were 20 and 5 cm H2O, respectively.

SIMILAR OUTCOMES AND SAFETY

The rates of mortality, endotracheal intubation, and treatment failure (death and/or intubation) were 15.1%, 9.4%, and 20.7%, respectively, in the iron lung group and 16.9%, 13.2%, and 24.5%, respectively, in the NIPPV group. Between-group differences in these rates were not statistically significant.

However, the iron lung was associated with a significantly shorter median duration of mechanical ventilation—only 24 hours compared with 57 hours for NIPPV. The median ICU stay was 11 days among survivors treated with the iron lung versus 14 days for those who received NIPPV. Although these data point to possible benefits of iron lung use, the researchers admitted that further study is needed because no standardized criteria for discontinuation of ventilation or hospital discharge were set during their investigation.

The study was retrospective, so its findings must be confirmed in a prospective, randomized, controlled trial. The availability of both the iron lung and NIPPV “could widen the field of application of noninvasive ventilation,” the investigators concluded.

—Timothy Begany