Each patient underwent three overnight sleep studies, one prior to the initiation of positive pressure ventilation, a second while receiving positive pressure ventilation, and a third on the first postventilatory night (no mechanical ventilation) after three months of nocturnal ventilation. Standard sleep variables included the electroencephalogram (EEG), submental electromyogram (EMG), electro-occulogram (EOG), and electrocardiogram (ECG), with sleep stages being scored in 40-s epochs by standard criteria. Respiratory movements were monitored by inductive plethysmography (respitrace ambulatory monitoring, Ardsley, NY). ampicillin antibiotic
The SaOa was measured with a pulse oximeter (Ohmeda Biox 3700) and Pcot was measured transcutaneously with a carbon dioxide monitor (Kontron Microgas 7640). Measurements of SaOa were made on an epoch-by-epoch basis, and for each epoch, the highest and lowest values were recorded and the results were expressed as the mean high and mean low values of each sleep stage. Measurements of Pco, were made on an epoch-by-epoch basis and were expressed as the mean and highest value for each sleep stage.