Effect of Mask Selection on the Leak Test in Ventilators Designed for Noninvasive Ventilation

BACKGROUND: The mask leak test used for modern noninvasive ventilators can detect the leak characteristics of masks that are not recommended by the manufacturer, but it has not yet been determined whether this method is acceptable.

METHODS: A noninvasive ventilator equipped with a single-limb circuit and an oronasal mask was connected to a lung simulator. The ventilator was set to S/T mode, and inspiratory positive airway pressure/expiratory positive airway pressure was set to 10/5, 15/5, and 20/5 cm H₂O, respectively. Eight nonmanufacturer-recommended oronasal masks were connected to the ventilator. The lung simulator was used to simulate COPD, restrictive disease, and normal lung, respectively. When switching between masks, the mask leak test was set to “Cancel” or “Start Test” in the noninvasive ventilator. The parameters displayed on the lung simulator and ventilator were recorded before and after the mask leak test.

RESULTS: There were no significant difference before versus after the mask leak test for any lung simulator parameter, including trigger performance (ie, time from the beginning of the simulated inspiratory effort to the lowest value of airway pressure needed to trigger the ventilator, the magnitude of airway pressure drop needed to trigger, and time to trigger), inspiratory pressure delivery, PEEP, tidal volume, and displayed peak inspiratory pressure (all differences < 10%). At different noninvasive ventilation settings, tidal volumes displayed on the ventilator of the 3 masks were significantly different before and after mask leak test (all P < .05, and difference rate > 10%).

CONCLUSIONS: The mask leak test had no effect on the ventilator performance when masks not recommended by the manufacturer were used, but tidal volume monitoring may be more accurate when some masks were used.