Astral 150

On the day before the test day, the subjects were familiarized with the ventilator equipped with VCM (Astral 150, Resmed, Saint-Priest, France) and with the face mask (Laerdal Medical, Limonest, France). The ventilator, commercially available in Europe, was set to deliver noninvasive volume continuous mandatory ventilation modified to allow a 500% increase in V T and was used in volumetric mode for both VCM and breath-stacking. The subjects received training in both breath-stacking and VCM. V T and other settings were those habitually used by the subject. The number of consecutive insufflations required to optimize the breath-stacking technique was determined for each subject during the training session. Instructions were tailored to each participant.
On the test day, each subject performed both techniques in random order. All measurements were performed with the subject seated in the usual wheelchair. One physiotherapist and one technician carried out the tests, preventing leakage and performing the measurements, respectively. Great care was taken to avoid leaks around the face mask during each of the tests. The tests were performed using the settings determined during the training sessions. During coughing, the subject received strong verbal encouragement from the physiotherapist.