• Zhi-Xin Cao and Chen Wang.
• Beijing Chaoyang Hospital Affiliate of Capital University of Medical Sciences, Beijing Institute of Respiratory Medicine, Beijing 100020, China.
• Zhonghua Jie He He Hu Xi Za Zhi. 2008 Feb 1;31(2):116-9.

ObjectiveTo study the relationship between air leak and auto-triggering in noninvasive positive pressure ventilation (NIPPV), and the effects of auto-triggering on patient-ventilators interaction.MethodsFive different types of noninvasive ventilators, a lung simulator and 14 healthy volunteers were studied by using a quantificational air leak model and a spirometer which monitoring the pressure, flow and volume curve in the tube continuously. SPSS version 10.0 was used for statistical analysis. Data were presented as x +/- s, and means were compared with analysis of variance.ResultsIn the study of lung simulator, the percentage of times of auto triggering in total testing times was from 24% -90% in the BiPAP mode in various ventilators. Air leaking capacity was the most crucial factor related to auto triggering (beta = 0.709, OR = 2.032). With increased air leak level, 14 volunteers all presented with auto triggering. All the volunteers' respiratory rate increased and tidal volume decreased with the increasing level of air leak.ConclusionAuto-triggering occurred when air leak increased in NIPPV. The insufficient compensation of flow base line may be the cause for auto-triggering. Auto-triggering can impair patients ventilation.

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