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Impact of Inspiratory Pressure Rise Time on Lung-Emptying in Time Controlled Adaptive Ventilation
Benjamin Neetz1,2,3, Patrick Rehn4,5,2, Nicole Kraus1,2
1Department of Pneumology and Critical Care Medicine, Thoraxklinik, Heidelberg University Hospital, Germany.
Setting inspiratory pressure rise time (IPRT) to 0 ms in time-controlled adaptive ventilation (TCAV) may improve lung emptying and reduce driving pressure (ΔP). Prolonged IPRT can mislead measurements of intrinsic PEEP (PEEPi) and negatively impact ventilation.
Area of Science:
- Mechanical Ventilation
- Respiratory Physiology
- Critical Care Medicine
Background:
- Airway pressure release ventilation (APRV) and time-controlled adaptive ventilation (TCAV) aim to minimize ventilator-induced lung injury (VILI).
- The role of inspiratory pressure rise time (IPRT) within TCAV is not well understood.
- Varying IPRTs may affect lung emptying and key ventilatory parameters.
Purpose of the Study:
- To investigate the impact of different IPRTs on lung emptying and ventilatory parameters during TCAV.
- To assess if IPRT influences driving pressure (ΔP), intrinsic PEEP (PEEPi), and exhaled tidal volume (VTe).
- To evaluate the accuracy of conventional PEEPi measurements under varying IPRTs in TCAV.
Main Methods:
- A prospective exploratory study involving 10 intubated subjects on TCAV.
- Consecutive trials with IPRTs of 0 ms (baseline), 500 ms, and 1,000 ms.
- Measurements included ventilator-derived ΔP (ΔPvent), PEEPi, VTe, elastance (ERS), and end-expiratory lung volume (EELV) via electrical impedance tomography (EIT).
Main Results:
- Prolonged IPRT significantly increased elastance-derived ΔP (ΔPelast) compared to ΔPvent.
- This increase in ΔP was associated with a loss of PEEPi, which was not detected by conventional measurements.
- Electrical impedance tomography (EIT) revealed a reduction in end-expiratory lung volume (EELV) with prolonged IPRT.
Conclusions:
- Prolonged IPRT during TCAV reduces EELV and PEEPi, consequently increasing ΔP.
- Conventional PEEPi measurement methods are unreliable in this setting.
- Setting IPRT to 0 ms is recommended for the TCAV protocol to optimize ventilation and potentially reduce VILI.
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