Flow beyond intended expiratory flow termination: Why inspiratory pressure rise time should be integrated into Airway Pressure Release Ventilation (APRV) recommendations

Benjamin Neetz, Mascha O Fiedler-Kalenka, Markus A Weigand, Patrick Rehn

Abstract

This letter highlights the role of the inspiratory rise time (IPRT) within the Time-Controlled Adaptive Ventilation (TCAV) protocol. While current guidelines emphasize adjusting T_Low to terminate expiratory flow at approximately 75% of the peak expiratory flow rate to prevent alveolar instability and atelectrauma, the potential impact of IPRT on these flow kinetics has been largely unrecognized. Our prospective data suggest that increasing the IPRT can prolong the release phase, which may be associated with a reduction in end-expiratory lung volume (EELV) and intrinsic PEEP (PEEPi), alongside a potential increase in driving pressure and tidal volume. Notably, conventional assessment methods, such as the expiratory hold maneuver, may fail to detect these alterations, which could limit the reliability of standard clinical monitoring in this context. To safeguard EELV and optimize the protective nature of this strategy, we suggest that future clinical investigations evaluate whether managing IPRT as a protocol consideration can further refine the safety and consistency of the TCAV protocol.

Keywords: Inspiratory pressure rise time, APRV, TCAV

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