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.

The Effect of Different Interfaces on the Aerosol Delivery with Vibrating Mesh Nebulizer During Noninvasive Positive Pressure Ventilation.

Background: The effect of different interfaces on the aerosol delivery with vibrating mesh nebulizer during noninvasive positive pressure ventilation (NIV) is not clear. Materials and Methods: Noninvasive ventilator and four interfaces were connected to IngMar ASL 5000 lung simulator. Meanwhile, the vibrating mesh nebulizer was connected to a ventilator circuit to simulate the nebulization during noninvasive ventilation. The nebulizer position was placed at proximal position (near the mask) and distal position (15 cm away from the mask); the inspiratory positive airway pressure (IPAP) and the expiratory positive airway pressure (EPAP) were set to 16/4, 16/8, 20/4, and 20/8 cmH2O, respectively. The aerosol was collected through a disposable filter placed between the simulated lung and the mask, after which the aerosol delivery was calculated. Meanwhile, we recorded the inspiratory tidal volume and the mean inspiratory flow. Results: The aerosol delivery varied between 1.7% ± 0.0% and 21.1% ± 1.1%. Only when EPAP was set to 4 cmH2O, the statistical difference in aerosol delivery was observed between the two types of interface, and between different leak port locations (p < 0.01; p = 0.04, respectively). When IPAP/EPAP was set to 16/4 and 20/4 cmH2O, respectively, at different nebulizer positions, there was a statistical difference between the interface with the same type but different leak port locations and between the interface with same leak port location but different inner volumes (all p < 0.01). Also, there was a correlation between the aerosol delivery and interface volume (p < 0.01, R2 = 0.55; p < 0.01, R2 = 0.51, respectively), and between aerosol delivery and the intentional leak of interfaces (p < 0.01, R2 = 0.59; p < 0.01, R2 = 0.48, respectively). When EPAP was set to 4 and 8 cmH2O, respectively, the aerosol delivery of nebulizer distal position was significantly higher than that of proximal position (12.2% ± 5.0% vs. 9.1% ± 4.1%, p < 0.05; 2.5% ± 0. 5% vs. 2.1% ± 0.3%, p < 0.01, respectively). Conclusion: Interfaces have a significant effect on aerosol delivery during NIV. The interfaces with different inner volumes, intentional leak, and leak port location may all have an effect on aerosol delivery. The addition of a 15 cm tube between the nebulizer and the mask significantly increases the aerosol delivery.