Respiratory weakness after mechanical ventilation is associated with one-year mortality - a prospective study.

Clément Medrinal,Aurora Robledo Quesada,Tristan Bonnevie,Antoine Poncet,Bouchra Lamia,Éric Frenoy,Olivier Contal,Guillaume Prieur,Francis-Edouard Gravier

doi:10.1186/s13054-016-1418-y

Abstract

BackgroundDiaphragm dysfunction in mechanically ventilated patients is associated with poor outcome. Maximal inspiratory pressure (MIP) can be used to evaluate inspiratory muscle function. However, it is unclear whether respiratory weakness is independently associated with long-term mortality. The aim of this study was to determine if low MIP is independently associated with one-year mortality.MethodsWe conducted a prospective observational cohort study in an 18-bed ICU. Adults requiring at least 24 hours of mechanical ventilation with scheduled extubation and no evidence of pre-existing muscle weakness underwent MIP evaluation just before extubation. Patients were divided into two groups: low MIP (MIP ≤30 cmH2O) and high MIP (MIP >30 cmH2O). Mortality was recorded for one year after extubation. For the survival analysis, the effect of low MIP was assessed using the log-rank test. The independent effect of low MIP on post mechanical ventilation mortality was analyzed using a multivariable Cox regression model.ResultsOne hundred and twenty-four patients underwent MIP evaluation (median age 66 years (25th–75th percentile 56–74), Simplified Acute Physiology Score (SAPS) 2 = 45 (33–57), duration of mechanical ventilation 7 days (4–10)). Fifty-four percent of patients had low MIP. One-year mortality was 31 % (95 % CI 0.21, 0.43) in the low MIP group and 7 % (95 % CI 0.02, 0.16) in the high MIP group. After adjustment for SAPS 2 score, body mass index and duration of mechanical ventilation, low MIP was independently associated with one-year mortality (hazard ratio 4.41, 95 % CI 1.5, 12.9, p = 0.007). Extubation failure was also associated with low MIP (relative risk 3.0, 95 % CI 1, -9.6; p = 0.03) but tracheostomy and ICU length of stay were not.ConclusionLow MIP is frequent in patients on mechanical ventilation and is an independent risk factor for long-term mortality in ICU patients requiring mechanical ventilation. MIP is easily evaluated at the patient’s bedside.Trial RegistrationThis study was retrospectively registered in www.clinicaltrials.gov (NCT02363231) in February 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1418-y) contains supplementary material, which is available to authorized users.

Highlights

Diaphragm dysfunction in mechanically ventilated patients is associated with poor outcome
124 participants were enrolled in the study and underwent Maximal inspiratory pressure (MIP) evaluation
Demographic and clinical factors according to MIP There were 67 patients (54 %) with low MIP

Summary

Introduction

Diaphragm dysfunction in mechanically ventilated patients is associated with poor outcome. Maximal inspiratory pressure (MIP) can be used to evaluate inspiratory muscle function It is unclear whether respiratory weakness is independently associated with long-term mortality. Levine et al showed that 18–69 hours of controlled MV leads to more than 50 % reduction in the crosssectional area of type I and II diaphragm fibres [3]. This atrophy is the result of a reduction in protein synthesis and acceleration in protein degeneration. Jaber et al confirmed these results, showing progressive reduction in transdiaphragmatic pressure in ventilated patients, with a 32 % drop in strength after 5 days of MV [4]

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