Use of ultrasound to determine changes in diaphragm mechanics during a spontaneous breathing trial

Weaning from mechanical ventilation is one of the most common activities undertaken in intensive care. Currently, the gold standard for weaning and assessing for extubation is a spontaneous breathing trial (SBT). Diaphragmatic ultrasound is an emerging tools that may have considerable utility in augmenting the decision making process surrounding weaning and extubation. We aim to assess diaphragmatic function via ultrasound and electromyographic activity analysis at the start and end of a spontaneous breathing trial. A spontaneous breathing trial consists of the patient being placed on a T-piece without PEEP and given enough supplemental oxygen to maintain adequate oxygen saturation. For a spontaneous breathing trial to be considered successful, it must last at least 30 minutes. Patients who are planned to undergo a spontaneous breathing trial as part of their usual care will be considered for the trial. Ultrasound assessment of the right hemidiaphragm will be conducted within the first 5 minutes of the SBT and at 30 minutes. This will be conducted by a qualified ultrasonographer with the patient lying at 45 degrees. Measurement of diaphragmatic excursion, speed of diaphragmatic contraction and diaphragmatic thickness (at end-inspiration and end-expiration) will be conducted at both assessments.