Iron lungversusconventional mechanical ventilation in acute exacerbation of COPD

Abstract

The aim of this randomised study was to compare the effects of iron lung ventilation (ILV) with invasive mechanical ventilation (IMV) in patients with acute respiratory failure (ARF) due to exacerbation of chronic obstructive pulmonary disease.Forty-four patients with ARF were assigned either to ILV (22 patients) or IMV (22 patients). Primary end-points were the improvement in gas exchange and complications related to mechanical ventilation.On admission ILV and IMV groups did not differ in age, simplified acute physiology score II, arterial oxygen tension (Pa,O 2 )/inspiratory oxygen fraction (FI,O 2 ), arterial carbon dioxide tension (Pa,CO 2 ) and pH. Compared with baseline, ILV and IMV induced a similar and significant improvement in Pa,O 2 /FI,O 2 , Pa,CO 2 and pH after 1 h of treatment and at discontinuation of mechanical ventilation. Major complications tended to be more frequent in patients treated with IMV than in those treated with ILV (27.3% versus 4.5%), whereas mortality rate was similar (27.3% versus 18.2%). The ventilatorfree days and the length of hospital stay were significantly lower in the ILV than in the IMV group.This study suggests that iron lung ventilation is as effective as invasive mechanical ventilation in improving gas exchange in chronic obstructive pulmonary disease patients with acute respiratory failure, and is associated with a tendency towards a lower rate of major complications. Endotracheal intubation and mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD) and acute or chronic respiratory failure are associated with several complications [1,2]. Compared with standard medical therapy, noninvasive positive pressure ventilation (NIPPV) reduces the need for endotracheal intubation [3][4][5], the length of hospital stay [3], and the in-hospital mortality rate [3][4][5][6]. Recently, it was shown that in COPD patients with severe respiratory failure that failed medical therapy in the ward, NIPPV compared with invasive mechanical ventilation (IMV) resulted in a similar mortality rate, length of hospital stay and duration of mechanical ventilation [7].It has been reported that COPD patients with severe respiratory acidosis and hypercapnic coma can be successfully treated with iron lung ventilation (ILV) [8]. A case-control study [9] suggested that ILV is as effective as IMV in the treatment of COPD patients with acute on chronic respiratory failure and is associated to a shorter duration of ventilation, and a similar length of hospital stay. Nevertheless, to date, no randomised study comparing ILV with IMV for the treatment of exacerbation of COPD has been carried out.The aim of this prospective controlled, randomised, pilot study was to compare the effects of ILV and IMV on gas exchange and the rate of complications associated with mechanical ventilation in COPD patients with acute on chronic respiratory failure.

Management of acute ventilatory failure

“…28 29 This was superseded by the improvements in the area of IPPV and endotracheal intubation in the 1950s. Although negative pressure ventilation has had resurgence in interest during recent years 30 ; NIV is nowadays commonly delivered by the use of positive pressure. This commonly entails the use of continuous positive airway pressure (CPAP; where a constant pressure is set during inspiration and expiration) or non-invasive positive pressure ventilation (NIPPV; where a higher pressure is set during inspiration than expiration).…”

Relative effects of negative versus positive pressure ventilation depend on applied conditions

“…Transpulmonary pressure ( P L ) is the distending pressure across the lung defined by the pressure at the airway opening (Pao) minus pleural pressure; as such, a drop in overall pleural pressure should have the same mechanical impact as an identical rise in airway opening pressure. However, comparisons of negative and positive pressure ventilation have had mixed results in terms of hemodynamics [1–3], respiratory mechanics [1], oxygenation [4], and on outcome in patients with obstructive lung disease [5]. …”

Is there still a negative side to noninvasive ventilation?

“…The current trial [1] and the previous case-control study by the same authors [11] establish that iron lung ventilation is effective at improving gas exchange abnormalities in chronic obstructive pulmonary disease patients with severe hypercarbia. Furthermore, outcomes, such as complication and mortality rates, are within the ranges reported for noninvasive positive pressure ventilation [9,10].…”

“…Based on these studies, the current view is that NPPV should be considered the ventilatory modality of first choice and inMV should be reserved only for patients in whom NPPV is contraindicated or fails. Thus, it is arguable that many of the patients in the inMV group of the study by CORRADO et al [1] might have succeeded with NPPV, with the expectation that complication and mortality rates would have been lower. For this reason, if any large multicentre trial evaluating ILV is to be performed, the comparison should not be with inMV as CORRADO et al [1] suggest, but rather with NPPV as the initial modality.…”

“…One of these centres is that directed by Corrado and colleagues in Italy, who herein report the results of the first randomised controlled trial comparing iron lung ventilation (ILV) to invasive positive pressure ventilation (inMV) in severely hypercarbic (arterial carbon dioxide tension (Pa,CO 2 ) w9.3 kPa) COPD patients with acute on chronic respiratory failure [1]. The authors found that ILV performed very favourably in comparison to inMV, with only four (18.2%) of 22 ILV-treated patients requiring intubation.…”