Abstract
ObjectivesDefined as the energy applied to the respiratory system by ventilator, mechanical power (MP) of ventilation reflects the risk of ventilation-induced lung injury. This study aims to explore the relationship between dynamic changes in MP and prognosis in critically ill patients.MethodsThis was a single-centre retrospective cohort study. Patients receiving mechanical ventilation with acute respiratory failure (ARF) and MP > 10 J/min on admission in the ICU were included. MP (J/min) was calculated as 0.098 × minute ventilation (L/min) × [(peak inspiratory pressure + positive end-expiratory pressure)/2] and the MP variation rate (%) as ([baseline MP − 24-h MP]/baseline MP) × 100. Patients were divided into two groups according to whether MP decreased 24 h after admission (MP-improved group defined as 24-h MP variation rate > 0% vs. MP-worsened group defined as 24-h MP variation rate ≤ 0%).ResultsIn total, 14,463 patients were screened between January 2015 and June 2020, and finally, a study cohort of 602 patients was obtained. The MP-improved group had a lower ICU mortality rate than the MP-worsened group (24% vs. 36%; p = 0.005). The 24-h MP variation rate was associated with ICU mortality after adjusting for confounders (odds ratio, 0.906 [95% CI 0.833–0.985]; p = 0.021), while baseline MP (p = 0.909) and 24-h MP (p = 0.059) were not. All MP components improved in the MP-improved group, while minute ventilation and positive end-expiratory pressure contributed to the increase in MP in the MP-worsened group.ConclusionsThe 24-h MP variation rate was an independent risk factor for ICU mortality among ARF patients with elevated MP. Early decreases in MP may provide prognostic benefits in this population.
Highlights
Ill patients with acute respiratory failure (ARF) are usually exposed to high-intensity mechanicalChi et al BMC Pulm Med (2021) 21:331 overcome the resistance of a patient’s respiratory system over a period, usually expressed as joules per minute (J/ min)
The optimal positive end-expiratory pressure (PEEP) was set by the maximal static respiratory compliance in some patients and by bedside ultrasound [17] or electrical impedance tomography in others [18]. Saturation of peripheral oxygen (SpO2) was not allowed to reach 100% unless at room air
We evaluated the predictive values of baseline mechanical power (MP), 24-h MP and the MP variation rate for intensive care unit (ICU) mortality rates
Summary
Ill patients with acute respiratory failure (ARF) are usually exposed to high-intensity mechanicalChi et al BMC Pulm Med (2021) 21:331 overcome the resistance of a patient’s respiratory system over a period, usually expressed as joules per minute (J/ min). Ill patients with acute respiratory failure (ARF) are usually exposed to high-intensity mechanical. Several retrospective studies have indicated that MP is an independent risk factor for predicting short- or long-term outcomes among critically ill patients [6,7,8,9]. Very limited evidence exists regarding the dynamic change in MP and patient outcomes in the ICU. As both injurious MP and exposure time are considered essential components of VILI development [10, 11], a quick reduction in injurious power over time should provide beneficial effects in terms of patient outcomes. We intend to investigate the relevant factors behind MP changes, namely, the components of MP, including minute ventilation, positive end-expiratory pressure (PEEP) and respiratory compliance, to find possible effective targets for reducing MP
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