Diaphragm Muscle Atrophy in the Mechanically Ventilated Patients

Abstract

PURPOSE: Approximately 40% of patients in medical intensive care units (MICU) require mechanical ventilation (MV), and difficulties in discontinuing MV are encountered in 20-25% of these patients.Multiple studies suggest that MV has an unloading effect on the respiratory muscles leading to diaphragmatic dysfunction, a process called Ventilator-Induced Diaphragm Dysfunction (VIDD). VIDD may be an important factor affecting when and if a patient can be weaned from MV. The purpose of this study was to quantify, through daily sonographic assessments, the rate and degree of diaphragm atrophy. METHODS: Seven intubated patients acutely requiring MV were included and diaphragm muscle thickness was measured daily from the day of intubation until the patient met one of the following criteria: (1) exubation;(2) tracheostomy or (3) expired. We analyzed our data with standard descriptive statistics and linear regression. RESULTS: The overall decrease in the diaphragm thickness of all seven patients over time was at a rate of 5.6% per day of MV which was statistically significant. Similarly the diaphragm thickness decreased for each patient over time. CONCLUSIONS: Sonographic assessment of the diaphragm provides noninvasive measurement of diaphragmatic thickness and degree of atrophy in patients on MV. Diaphragm muscle atrophy starts as early as 24 hours after initiation of MV and progresses throughout at least the first week of MV. CLINICAL IMPLICATIONS: A sensitive and specific diagnostic test for VIDD, could allow physicians valuable information that might influence decisions regarding extubation or tracheostomy. Historically, direct imaging of the diaphragm has been difficult and functional assessment of the diaphragm in intubated patients is effort dependent and unreliable. Using ultrasound to measure diaphragm thickness (tdi) provides a noninvasive image of the diaphragm and can demonstrate atrophy over time. Our study demonstrated this atrophy occurs rapidly and significantly by 24 hours and continues over at least the first week of MV. Although it is clear that loss of diaphragm strength and function occur over time in mechanically ventilated MICU patients, it remains unclear if demonstrating diaphragmatic atrophy clinically correlates to prolonged respiratory failure. Further studies are needed to determine if diaphragmatic atrophy has an impact on weaning from MV.