Using Ultrasound to Study Respiratory Muscle Function in Critically Ill Patients

Mechanical ventilation can be life saving strategy for patients with respiratory failure due to a variety of reasons. Once the underlying illness has resolved, intensive care doctors have to take a decision on when the patient is safe to get off the ventilator or be extubated. They use clinical assessment of the patient's ability to breathe spontaneously and make use of some breathing parameters to make the judgment. Most of the time, a patient can come off the ventilator and do well, but sometimes muscle weakness from sickness can affect the patient's ability to breathe adequately once ventilator support is discontinued. If that occurs, the patient may have to be put back on the ventilator and the physician will suggest some changes to help muscles get stronger. A simple, non-invasive test that can assess respiratory muscle state before taking patients off the ventilator to see if their muscles look healthy can help distinguish which patients may not be ready to be extubated. There are currently several tests available to assess muscle strength, in particular muscles that help in breathing like the intercostal muscles and diaphragm. The study will test the use of Ultrasonography (Ultrasound) as a non-invasive test to assess the muscles of respiration. This test will also help the investigators test physical therapies and interventions of mechanical ventilation that can help patients strengthen the muscles while waiting for extubation.