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 respirator y 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-inv asive ventilatory technique such as the iron lung could also be used s uccessfully in patients with hypoxic hypercapnic coma, thus widening t he range for application of non-invasive ventilatory techniques. Metho ds - A series of 150 consecutive patients with ACRF and hypoxic hyperc apnic coma admitted to our respiratory intensive care unit were evalua ted retrospectively. The most common underlying condition was chronic obstructive pulmonary disease (79%). On admission a severe hypoxaemia (Pao(2) 5.81 (3.01) kPa) and hypercapnia (Paco(2) 14.88 (2.78) kPa) as sociated 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 scor e was 31.6 (5.3). All patients underwent intermittent negative pressur e ventilation with the iron lung. The study end point was based on a d ichotomous classification of treatment failure (defined as death or ne ed for endotracheal intubation) versus therapeutic success. Results - There were 45 treatment failures (30%) and 36 deaths (24%). Nine patie nts (6%) required intubation because of lack of airway control. The me dian total duration of ventilation was 27 hours per patient (range 2-2 74). The 105 successfully treated cases recovered consciousness after a median of four hours (range 1-90) of continuous ventilatory treatmen t and were discharged after 12.1 (9.0) days. Conclusions - These resul ts show that, in patients with acute on chronic respiratory failure an d hypoxic hypercapnic coma, the iron lung resulted in a high rate of s uccess. As this study has the typical limitations of all retrospective and uncontrolled studies, the results need to be formally confirmed b y controlled prospective studies. Confirmation of these results could widen the range of application of non-invasive ventilatory techniques.