(403) Reducing Overassistance in Neurosurgical Patients Is Safe and Improves Lung Ventilation Homogeneity

Tuesday, February 25, 2025

8:45am – 9:45am Eastern Time

Location: Connections Central - RST 11

First Author(s)

Vorakamol Phoophiboon, MD, MSc (she/her/hers)

Toronto, USA

Co-Author(s)

AR

Antenor Rodrigues, PT, PhD

Physiotherapist
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
MK

Matthew Ko, RRT

Registered respiratory therapist
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
MD

Mattia Docci, MD

Physician
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
AS

Annia Schreiber, MD

Physician
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
LM

Luca Salvatore Menga, MD

Physician
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
AW

Ada Wong, MSd

Research Coordinator
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
MS

Mayson Sousa, PT

Physiotherapist
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
RB

Rosie Butterworth, N/A

Undergraduate student
Department of Biology, Western University, London, ON, Canada, United States
FV

Fernando Vieira, PT

Physiotherapist
St.Michael's hospital, Unity Health Toronto, University of Toronto, Toronto, ON, Canada, United States
LB

Laurent Brochard, MD

Physician
University of Toronto/St. Michael's Hospital Keenan Research Centre, Toronto, ON, Canada, United States

Introduction: Many neurosurgical patients are kept on mechanical ventilation (MV) while waiting for their neurological recovery. Over assistance from MV may occur and lead to adverse outcomes. Recognizing that MV is not needed may lead to shorter decisions for extubation.

Methods: This observational study aimed to identify regional ventilation using electrical impedance tomography (EIT) in neurosurgical patients on clinical pressure support ventilation (CPSV, PS[8-10] & PEEP[5-8]), on low setting (LPSV, PS5 & PEEP5) and 30-minute spontaneous breathing trial (SBT, PS0 & PEEP0). The tidal images derived from EIT was divided into 2 layers representing ventral (V) & dorsal (D) regions. Our main outcome was absolute difference between V & D regions (VD difference), a smaller difference means more homogeneous ventilation. Secondary outcomes included surrogates of over assistance: airway occlusion pressure for the drive; P0.1≤1, muscle pressure; Pmus < 5 and pressure muscle index; PMI≤0 for respiratory activity. ΔPL,dyn≥17 was used as a marker of risky lung distending pressure. Non-invasive regional cerebral oximetry (cStO2) and blood volume index (BVI) were used to monitor brain perfusion. Patients were divided in 2 groups according to the effect of reducing PSV on tidal volume(Vt)/PBW.

Results: Twenty-four patients were included (mean±SD: age 62±15 years, 38%men), all passed the SBT clinically. 63% of patients had at least 1 criterion suggesting over assistance at CPSV (38%P0.1, 29%Pmus, 33%PMI), 38% of patients at LPSV (29%P0.1, 21%Pmus, 1%PMI) and only 25% of patients at SBT had a low drive but no over assistance (25%P0.1, 0Pmus, 0PMI). The number of patients with ΔPL,dyn≥17 was (25% at CPSV, 13% at LPSV, 13% at SBT).
Absolute (VD difference) improved from CPSV to SBT overall (CPSV 24[15-26] vs SBT 16[10-21], p=0.007) and in the patients with a decrease in Vt (n=14; CPSV 25[16-30] vs SBT 17[11-20] p=0.013); it did not change in patients with no change in Vt. cStO2, BVI, SBP, MAP and HR were not different when changing from CPSV to SBT.

Conclusions: Neurosurgical patients under MV seems to be frequently over-assisted at CPSV. Reducing MV support reduce over assistance while improving ventilation homogeneity and maintaining level of brain oxygenation especially when Vt decreases with reduced PS level.