Intermittent negative pressure ventilation in the treatment of hypoxic hypercapnic coma in chronic respiratory insufficiency.

BACKGROUND: In recent years non-invasive ventilatory techniques have been used successfully in the treatment of acute on chronic respiratory failure (ACRF), but careful selection of patients is essential and a comatose state may represent an exclusion criterion. The aim of this retrospective and uncontrolled study was to evaluate whether a non-invasive ventilatory technique such as the iron lung could also be used successfully in patients with hypoxic hypercapnic coma, thus widening the range for application of non-invasive ventilatory techniques. METHODS: A series of 150 consecutive patients with ACRF and hypoxic hypercapnic coma admitted to our respiratory intensive care unit were evaluated retrospectively. The most common underlying condition was chronic obstructive pulmonary disease (79%). On admission a severe hypoxaemia (Pao2 5.81 (3.01) kPa) and hypercapnia (Paco2 14.88 (2.78) kPa) associated with a decompensated acidosis (pH 7.13 (0.13)) were present, the Glasgow coma score ranged from 3 to 8, and the mean APACHE II score was 31.6 (5.3). All patients underwent intermittent negative pressure ventilation with the iron lung. The study end point was based on a dichotomous classification of treatment failure (defined as death or need for endotracheal intubation) versus therapeutic success. RESULTS: There were 45 treatment failures (30%) and 36 deaths (24%). Nine patients (6%) required intubation because of lack of airway control. The median total duration of ventilation was 27 hours per patient (range 2-274). The 105 successfully treated cases recovered consciousness after a median of four hours (range 1-90) of continuous ventilatory treatment and were discharged after 12.1 (9.0) days. CONCLUSIONS: These results show that, in patients with acute on chronic respiratory failure and hypoxic hypercapnic coma, the iron lung resulted in a high rate of success. As this study has the typical limitations of all retrospective and uncontrolled studies, the results need to be formally confirmed by controlled prospective studies. Confirmation of these results could widen the range of application of non-invasive ventilatory techniques.

Iron lung treatment of acute on chronic respiratory failure: 16 yrs of experience.

Noninvasive ventilatory supports are gaining a prominent position among ventilatory techniques aimed to improve ventilation in patients with acute-on-chronic respiratory failure (ACRF). It has not yet been established whether these techniques can be considered as a preventive measure to avoid the need for endotracheal intubation, or are really another means to provide full ventilatory support. At our respiratory intensive care unit (RICU), the ventilatory treatment of ACRF has, for many years, been based on a conservative method, which relies on the use of a body ventilator (iron lung) providing intermittent negative pressure ventilation (INPV). From 1975 to 1991, we treated ACRF in 2,116 patients with chronic obstructive pulmonary disease (COPD) and 604 patients with restrictive thoracopulmonary disease (RTD). Two thousand and eleven patients (95%) underwent INPV. The mortality rate during hospitalization was 9.9% for the patients as a whole (10% and 8.9% for COPD and RTD patients, respectively). The mean length of stay in the RICU was 10.5 +/- 9.5 days. Furthermore, we report the results of our previous studies which investigated how the iron lung works, and how it affected the short- and long-term prognosis of COPD patients in ACRF. Finally, in 180 patients, we report the effects of INPV provided by iron lung on the treatment of ACRF with hypoxic hypercapnic coma (HHC). INPV resulted in a significant improvement of arterial blood gas values and pH, associated with a progressive recovery of the level of consciousness. Only 13 patients needed intubation and 41 (23%) died during hospitalization.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of intermittent negative pressure ventilation and long-term oxygen therapy for patients with COPD. A 4-year study.

We evaluated retrospectively the effect of long-term oxygen therapy (LTOT) on the prognosis of 35 patients with chronic obstructive pulmonary disease (COPD) and chronic respiratory insufficiency (group A) who were admitted to our respiratory intensive care unit from 1984 to 1986 for acute respiratory failure (ARF). All subjects were given intermittent negative pressure ventilation (INPV) by means of an iron lung to overcome the acute episode and were treated with LTOT after discharge. Forty-four patients with COPD who were treated with the same ventilatory method to overcome an acute disease exacerbation and who were not given LTOT were used as controls (group B). Both groups were followed up for at least 48 months. All relapses of ARF were treated by iron lung in both groups A and B. The overall survival was significantly better in group A than in group B (p = 0.05 by F test) indicating that LTOT improves survival in patients with COPD after a bout of ARF treated with mechanical ventilation. Therefore, combining INPV with LTOT for overcoming acute episodes and relapses of ARF appears to improve the prognosis of patients with COPD.

Iron lung treatment of subjects with COPD in acute respiratory failure. Evaluation of short- and long-term prognosis.

We evaluated retrospectively the short-term and the long-term prognosis of 105 patients with COPD and prolonged respiratory insufficiency admitted to our respiratory intensive care unit from 1976 to 1980 for acute respiratory failure. All subjects underwent intermittent negative pressure ventilation by means of an iron lung to overcome the acute episode. Twelve patients died during hospitalization, six were lost after discharge, while 87 were successfully weaned and were included in a follow-up lasting five years. All relapses of ARF were treated by INPV. The survival rates after one and five years were 82 percent and 37 percent, respectively and were significantly influenced by factors such as age, chronic cor pulmonale, FEV1/VC, PaCO2 on admission. The survival rate observed in our patients was better than that reported previously by other authors in COPD patients with ARF submitted to mechanical ventilation after intubation. These results suggest that INPV can improve survival in this category of patients, but a controlled clinical trial will be needed to address this issue.

Respiratory muscle insufficiency in acute respiratory failure of subjects with severe COPD: treatment with intermittent negative pressure ventilation.

Nine subjects with severe chronic obstructive pulmonary disease (COPD) in acute respiratory failure (ARF) and with marked weakness of the respiratory muscles (Group A) underwent intermittent negative pressure ventilation by means of an iron lung (8 h daily for 7 days). Seven subjects with COPD in stabilized chronic respiratory failure (Group B) were studied as controls and submitted to the same medical therapy without ventilator treatment. Functional respiratory tests were performed before and after 7 days of treatment. After ventilatory treatment, Group A showed an increase of maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax), vital capacity (VC), arterial oxygen tension (PaO2), pH and a decrease of residual volume (RV), total lung capacity of (TLC) and arterial carbon dioxide tension (PaCO2) (all statistically significant). No improvement was ascertained in the functional parameters of Group B. The expiratory muscles seem to play a determining role in ARF. We conclude that the iron lung is a useful therapeutic defence in removing muscular fatigue and in restoring a good level of respiratory compensation of ARF in severe COPD.