The Effect of Breath Termination Criterion on Breathing Patterns and the Work of Breathing During Pressure Support Ventilation

Abstract

Although termination criterion (TC) is usually nonadjustable, it influences the effectiveness of pressure support ventilation for mechanical ventilation. The proper adjustment of TC is crucial to improve patient-ventilator synchrony and decrease work of breathing. TC 5% of the peak inspiratory flow may be the optimal value for patients with acute respiratory distress syndrome or acute lung injury.

Identifying Patient-Ventilator Asynchrony Using Waveform Analysis

“…This may trigger a second breath by the ventilator if the patient inspiratory effort continues after the ventilator cycle to expiratory phase and if these efforts generated by the patient are able to overcome the trigger threshold programmed by the clinician [4]. Other studies agree with the findings of Thilleet al, Takioka H et al also demonstrated that there is a relationship between short-term inspiratory times programmed in the ventilator and double triggering, which is also related to a high ventilatory demand [4,23]. Double triggering can cause great harm to the ventilated patient because if the patient doesn't have enough expiratory time, the tidal volume delivered from the second breath will add to the tidal volume from the first breath which may double the tidal volume delivered to the patient causing over distension, volutrauma and barotrauma.…”

“…Premature cycling produces a significant decrease in airway pressure, which can be seen immediately after the end of the inspiratory phase programmed in the ventilator, accompanied by an increase of the inspiratory flow which can be seen in the flow/time waveform [32][ Figure 6]. This type of PVA could be confused with an ineffective effort during the expiratory phase, with the difference that premature cycling responds to changes in programmed inspiratory time or cycling; where as ineffective efforts responds to changes in the level of PEEP, sensitivity or assistance levels [23]. Another difference is that in premature cycling the drop of the airway pressure occurs immediately after the inspiratory phase has ended, indicating that the patient's inspiratory effort continues.…”

A Comparison of Leak Compensation in Acute Care Ventilators During Noninvasive and Invasive Ventilation: A Lung Model Study

“…Tokioka et al reported that delayed termination with a duty cycle of Ͼ 0.5 sometimes occurred with the lowest values of termination criteria (1% of peak inspiratory flow) in 2 of 8 patients with ARDS or acute lung injury. 9 In CMV, miss-triggering occurred less frequently and the ventilators required fewer breaths to synchronization than in PSV. As shown in the supplementary materials at http:// www.rcjournal.com, just after the system leak was increased, cycling delay due to inspiratory system leak induced miss-triggering, resulting in a longer time to synchronization during PSV.…”

“…5 Vignaux et al demonstrated that auto-triggering was present in 13% of patients, and delayed cycling in 23% of patients during NIV. 6 Patient-ventilator asynchrony can significantly increase the work of breathing, 8,9 and a high incidence of patient-ventilator asynchrony is associated with a longer duration of mechanical ventilation. 4,5 SEE THE RELATED EDITORIAL ON PAGE 2194 Although ICU ventilators were initially built to function without leaks, leak compensation has been added to ICU ventilators to improve patient-ventilator synchronization in the presence of system leaks.…”

Patient-Ventilator Interaction During Noninvasive Ventilation in Simulated COPD

“…5,6 Premature cycling leads to periods of unassisted breathing and increased work of breathing. 7 Furthermore, persistent inspiratory effort after pressure support ceases can lead to double-triggering, 7 resulting in discomfort, elevated tidal volumes (V T ), and volutrauma. 8 Cycling after the end of inspiratory effort shortens the expiratory time, causing intrinsic PEEP 9 and leading to increased work of breathing during triggering of the next breath.…”