Diaphragm Ultrasound Measurements With Variations in Modes of Ventilation

Diaphragm Ultrasound Measurements With Variations in Modes of Ventilation

The overall objective of the study is to conduct an observational study involving intensive care unit patients receiving mechanical ventilation and determine if there are differences in diaphragm thickness ultrasound measurements during expiratory and inspiratory phases in a controlled and spontaneous mode. For patients receiving sedatives, an additional set of measurements will be taken during a standard of care interruption of sedatives

In this study diaphragm ultrasound measurements at end-expiration and peak inspiration phases in assist control and pressure support mode in consented patients admitted to the medical intensive care unit. One-time measurements will be obtained during the first 48hrs that the patients are receiving mechanical ventilation. In patients receiving sedatives, additional measurements will be taken after an interruption of sedatives. Measurements will be compared between modes and on assist-control before and after an interruption of sedatives.

Three consecutive images will be obtained by an investigator that is blinded to the mode (controlled vs. spontaneous). Once measurements are obtained, a second investigator will switch to the other mode (controlled vs. spontaneous) and the blinded investigator will obtain three consecutive images after the patient has adjusted to the subsequent mode (one minute). Tidal volumes will be matched between modes as close as possible. The order of modes to ultrasound (controlled then spontaneous or spontaneous then controlled) will be determined by the non-blinded second investigator. Once the ultrasound measurements are obtained by the research team, image acquisition is concluded for the enrolled patient. The ventilator will be programmed back to the original settings determined by the medical ICU team.

The hypothesis is that the end-expiration diaphragm ultrasound measurement will be thicker in spontaneous mode than controlled mode.

Inclusion Criteria:

• Patients > 18 years of age
• intubated and mechanically ventilated for < 48 hours at the time of screening

Exclusion Criteria:

• pregnancy
• history of diaphragmatic paralysis
• neuromuscular blockade
• cardiac arrest