Written By Samuel Rouleau
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Patients with severe brain injury had a worse outcome using a lung-protective compared to conventional ventilation strategy.
Strict lung protective ventilation not the best for everyone
PROLABI was an open-label, multicenter randomized controlled trial of patients who were mechanically ventilated for acute, severe brain injury (unable to follow commands and open eyes on GCS score). The protective ventilation strategy was volume control with tidal volume (Vt) 6 mL/kg and PEEP 8 cm H2O compared to conventional ventilation strategy with Vt ≥ 8 mL/kg and PEEP 4 cm H2O. Goal PaCO2 was 35-38 mm Hg, and the maximum respiratory rate was 35 breaths per minute. The primary outcome was a composite of 28-day death, ventilator dependency, and ARDS. 104 were randomized to the protective strategy and 86 to the conventional strategy. Baseline characteristics and respiratory mechanics between the two groups were similar.
The protective vs. conventional ventilation group had worse outcomes:
- Primary (composite) outcome: 61.5% vs. 45.3%, relative risk (RR) 1.35 (95%CI 1.03–1.79; P = 0.025).
- Mortality: 28.9% vs. 15.1%, RR 1.91 (95%CI 1.06 – 3.42)
- Ventilator dependence: 42.3% v 27.9%, RR 1.52 (95%CI 1.01 – 1.28).
- ARDS: 30.8% vs. 22.1%, RR 1.39 (95%CI 0.85–2.27; P = 0.179).
The study was underpowered and stopped early secondary to funding issues. To compensate for lower tidal volumes and strict PaCO2 goals, the respiratory rate, minute ventilation, and mechanical power were notably higher in the protective ventilation group.
How will this change my practice?
I am not surprised by the results of this study, but I think there are other aspects at play.
- In the original ARMA trial, one principle to protect the lungs from ventilator-induced lung injury (VILI) was permissive hypercarbia to avoid high ventilator settings.
- Permissive hypercapnia (high PaCO2) is contraindicated for severe brain injury. So, patients in the protective group had higher respiratory rates and mechanical power. As mechanical power has been associated with VILI and high respiratory rates can cause atelectrauma, I am not sure that the protective ventilation group actually received “lung protective ventilation.”
- Patients with neurologic injury can be difficult to ventilate from a synchrony perspective (entrainment, reverse triggering, double triggering, centrally-mediated hiccups, Cheyne-Stokes, etc.), so trials should also report the level of sedation required to achieve their ventilation goal.
- My conclusion from PROLABI is that applying a ventilation strategy for ARDS does not translate to severe brain injury patients.
Source
Lung-Protective Mechanical Ventilation in Patients with Severe Acute Brain Injury: A Multicenter Randomized Clinical Trial (PROLABI). Am J Respir Crit Care Med. 2024 Nov 1;210(9):1123-1131. doi: 10.1164/rccm.202402-0375OC. PMID: 39288368
