1. Asynchrony index at baseline and following optimization of pressure support (PS) level (A), and following optimization of mechanical inspiratory time (mechanical TI) (B).
Asynchrony index at baseline and following optimization of pressure support (PS) level (A), and following optimization of mechanical inspiratory time (mechanical TI) (B). The asynchrony index is the ratio of wasted efforts to the total of wasted efforts plus triggered mechanical breaths collected for 2 minutes, expressed as a percentage. Optimizing the PS (Avea, Viasys Healthcare, Conshohocken, Pennsylvania) level (panel A) or mechanical TI (panel B) improves the asynchrony index. The optimal PS level is defined as the PS at which wasted efforts are eliminated when the PS is reduced by increments of 2 cm H2O, or when the patient shows poor tolerance, whichever occurs first. A positive end-expiratory airway pressure of 5 cm H2O is maintained at baseline and optimal PS. In 8 of 12 patients, optimizing the PS reduced the asynchrony index to 0% (A). In panel B, mechanical TI is adjusted until optimal mechanical TI is achieved. Optimal mechanical TI is obtained by increasing the cycling-off threshold by increments of 10% of peak flow rate. If the maximum cycling-off threshold is reached (45% of peak flow) and wasted efforts persist, the insufflation time is reduced by steps of 0.2 s from the mean insufflation time (by increasing the pressurization rate) until wasted efforts are eliminated or the patient develops respiratory intolerance, as defined above. Values are median and interquartile range. * P < .01 compared to baseline PS and PEEP. (From data in Reference 6.)‏
Catherine SH Sassoon Respir Care 2011;56:39-51
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