Coexistence and Impact of Limb Muscle and Diaphragm Weakness at Time of Liberation From Mechanical Ventilation in Medical ICU Patients.

American Journal of Respiratory and Critical Care Medicine

PubMedID: 27310484

Dres M, Dubé BP, Mayaux J, Delemazure J, Reuter D, Brochard L, Similowski T, Demoule A. Coexistence and Impact of Limb Muscle and Diaphragm Weakness at Time of Liberation From Mechanical Ventilation in Medical ICU Patients. Am J Respir Crit Care Med. 2016;.
BACKGROUND
Intensive care unit (ICU) and mechanical ventilation (MV) acquired limb muscle and diaphragm dysfunction may both be associated with longer length of stay and worse outcome. Whether they are two aspects of the same entity or whether they have a different prevalence and prognostic impact remains unclear. This study was designed to quantify the prevalence and coexistence of these two forms of ICU-acquired weakness and their impact on outcome.

METHODS
In patients undergoing a first spontaneous breathing trial (SBT) after at least 24 h of MV, diaphragm dysfunction was evaluated using twitch tracheal pressure in response to bilateral anterior magnetic phrenic nerve stimulation (a pressure <11 cmH2O defined dysfunction) and ultrasonography (thickening fraction (TFdi) and excursion). Limb muscle weakness was defined as a Medical Research Council (MRC) score <48.

RESULTS
76 patients were assessed at their first SBT: 63% had diaphragm dysfunction, 34% had limb muscle weakness and 21% had both. There was a significant but weak correlation between MRC score and twitch pressure (Rho=0.26, p=0.03) and TFdi (Rho=0.28, p=0.01), respectively. Low twitch pressure (OR 0.60, 95%CI 0.45-0.79, p<0.001) and TFdi (OR 0.84, 95%CI 0.76-0.92, p<0.001) were independently associated with weaning failure, but the MRC score was not. Diaphragm dysfunction was associated with higher ICU and hospital mortality, and limb muscle weakness was associated with longer duration of MV and hospital stay.

CONCLUSIONS
Diaphragm dysfunction is twice as frequent as limb muscle weakness and has a direct negative impact on weaning outcome. The two types of muscle weakness have only limited overlap.