[Effectiveness of intermittent self-ventilation after ventilator weaning]

Abstract

The essential cause for long-term mechanical ventilation with unweanability from respirator is chronic failure of the inspiratory muscles. Principally two different causes exist for chronic respiratory failure: Primary pulmonary diseases with overload or load imbalance of primarily uncompromised respiratory muscles, and neuromuscular diseases with a significant decrease in respiratory muscle capacity. Intermittent nocturnal ventilation (INV) leads to recovery by unloading the respiratory pump. In the present retrospective study we examined the value of INV in the "post-weaning-phase" for previously unweanable, long term ventilated patients. In two years (1993 and 1994) 43 patients who had been ventilated for 57.5 +/- 60.3 days in outward intensive care units (ICU) in a predominantly assisted mode we could wean from the respirator within 8.4 +/- 5.5 days by means of consequently applying an individually adapted, volume cycled weaning regime. In all patients, on admission to our ICU and before discharge blood gases, P0.1, Pimax, breathing frequency and tidal volume were measured during spontaneous breathing. After weaning in about 40% of our patients we decided to initiate INV with intermittent positive pressure ventilation (IPPV). The indication for INV after weaning depended on whether a chronic hypercapnic respiratory failure continued to be demonstrable. In this group of patients, INV was the essential stabilizing factor for continuous weaning success, as the respiratory muscles recovered during the ensuing inpatient phase and the daytime PaCO2 normalised. In most of our patients (14 out of 18) INV could be performed non-invasively via breathing masks. Only 4 out of 18 patients continued to be long-term ventilated invasively via tracheostomy. The remaining patients (25 out of 43) showed normoventilation at daytime during the ensuing inpatient phase so they did not need INV. At the time of the patients' referral to our ICU, there was no predictive value regarding the ultimate indication for INV after weaning from respirator.