Author: Thomas Rosenthal
Anesthesiology News
Diaphragm atrophy that develops while patients are mechanically ventilated is specifically associated with increased risks for reintubation, tracheostomy and prolonged ventilation, according to new research.
“The central finding of this study is that the progressive development of diaphragm atrophy during mechanical ventilation is associated with pro longed mechanical ventilation and ICU admission, and an increased risk of complications of acute respiratory failure,” said Ewan C. Goligher, MD, PhD, an assistant professor of medicine at the University of Toronto and a physician-scientist at the Toronto General Hospital Research Institute (Am J Respir Crit Care Med2018;197[2]:204-213).
“We also found that rapid early increases in diaphragm thickness predicted prolonged ventilation, raising the possibility of clinically significant diaphragm injury caused by insufficient respiratory muscle unloading during ventilation,” said Dr. Goligher, who is also the lead author of the study.
The researchers measured the diaphragm thickness daily of 191 adult patients who were mechanically ventilated. For 78 patients (41%), thickness decreased by more than 10%. The decrease was associated with a lower probability that the patient would be able to discontinue ventilation (adjusted hazard ratio, 0.69; 95% CI, 0.54-0.87; per 10% decrease), as well as a prolonged ICU length of stay (adjusted duration ratio, 1.71; 95% CI, 1.29-2.27) and a higher risk for complications (adjusted odds ratio, 3.00; 95% CI, 1.34-6.72). The researchers found that an increased thickness that developed in 47 patients (24%) predicted prolonged ventilation (adjusted duration ratio, 1.38; 95% CI, 1.00-1.90). Abnormally low inspiratory effort was related to decreasing thickness, whereas high effort correlated with increasing thickness. However, patients who had thickening similar to breathing at rest—a fraction of between 15% and 30%—during the first three days had the shortest ventilation duration. The researchers said they could report this association for the first time, as well as a corresponding lower rate of ICU admission.
The researchers said that for patients with acute respiratory failure, preventing and treating diaphragm atrophy or increased diaphragm thickness may significantly improve outcomes. They believe targeting that threshold of inspiratory effort similar to healthy patients at rest may result in an earlier release from mechanical ventilation.
More studies are needed, however, to find a direct link, Dr. Goligher said. Although “diaphragm atrophy may be causally related to the risk of prolonged ventilation, our findings cannot definitely confirm causality, which can only be demonstrated in the context of a randomized study of interventions known to prevent deleterious changes in the diaphragm during mechanical ventilation.” It is also possible that diaphragm activity that closely resembles healthy people at rest results in shorter times with mechanical ventilation, and prolonged ventilator dependence is associated with not only atrophy, but hypertrophy as well.
