PURPOSE: Difficulties in imaging the diaphragm have precluded serial measurements of diaphragm thickness of mechanically ventilated intensive care unit (ICU) patients. In this study, we used bedside ultrasound to determine diaphragm thickness shortly after intubation and then weekly thereafter.
METHODS: Patients [N=29] from the Medical ICU and medical wards were enrolled within 48 hours of endotracheal intubation. Charts were abstracted for clinical data. Ultrasound images were obtained using a previously validated method, with the patient seated at a 90 degree angle and the ultrasound probe placed at the 8th or 9th intercostal space at the zone of apposition. Weekly followup images were obtained until either liberation from mechanical ventilation or death. All images were obtained at end expiration. Ultrasound images were masked and diaphragm thickness was measured to the nearest 0.1 mm by a blinded investigator.
RESULTS: Average age of patients was 65-yrs old, with 50% men. Eight (28%) patients were extubated in the first week, and 8 (29%) patients required elective tracheotomy. Thirteen patients had repeat studies at week one, and nine had repeat studies at week two. On average, there was a statistically significant reduction in diaphragmatic thickness when compared to baseline by 17% at week one, and 20% at week two. The six patients who remained mechanically ventilated beyond week three showed no further loss of diaphragm thickness.
CONCLUSION: There is a significant diaphragmatic atrophy as measured by ultrasound within the first two weeks of mechanical ventilation in acutely critically ill patients.
CLINICAL IMPLICATIONS: Diaphragm atrophy may contribute to difficulty in weaning acutely critically ill patients from mechanical ventilation. Further investigations focusing on either preventing or reversing this atrophy may prove beneficial.
DISCLOSURE: Keith Rose, None.