Mechanical Ventilation Leads to Diaphragm Muscle Thinning

A new study shows that mechanical ventilation (MV) has an unloading effect on the respiratory muscles, leading to diaphragmatic atrophy and dysfunction.

Researchers at the Columbia University College of Physicians and Surgeons (New York, NY, USA) followed seven intubated patients receiving MV during acute care. The researchers measured diaphragm muscle thickness daily using sonography to quantify the rate and degree of diaphragm thinning during MV, a process known as ventilator-induced diaphragmatic dysfunction (VIDD). Daily measurement continued from the day of intubation until the patient underwent extubation, or tracheostomy, or died. The researchers then analyzed the data using standard descriptive statistics, linear regression, and mixed model effects.

The results showed that diaphragm muscle thinning starts within 48 hours after initiation of MV. The overall rate of decrease in the diaphragm thickness of all seven patients over time averaged 6% per day of MV, which differed significantly from zero. Similarly, the diaphragm thickness decreased for each patient over time.

“The purpose of this study was to quantify, using daily sonographic assessments, the rate and degree of diaphragm thinning during MV,” concluded lead author Horiana Grosu, MD, and colleagues of the division of pulmonary critical care and sleep medicine. “However, it is unclear if diaphragmatic thinning correlates with diaphragmatic atrophy or pulmonary function.”

VIDD results from a number of changes in the ventilatory muscles. First, at the macroscopic level, muscle atrophy occurs, representing a global reduction in the muscle mass and the cross sectional area of muscle fibers. At the ultrastructural level, observed changes include myofibrillar loss, mitochondrial abnormalities, and vacuole development. Third, there is biochemical evidence for oxidative stress and protein breakdown within the muscles. Lastly, at the genetic level, at least 354 gene expressions have been associated with controlled mechanical ventilation (CMV) and thus possibly VIDD.

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Columbia University College of Physicians and Surgeons