Volume Support/Assist Control Mode Ventilation and Diaphragmatic Atrophy

A Phase III Randomized Trial Comparing the Effects of Volume Support and Assist Control Mode Ventilation on Ventilator-Free Days and Diaphragmatic Atrophy

The objective of the study is to determine how controlled mode ventilation and support mode ventilation impact ventilator-free days and diaphragmatic atrophy.

Ventilator-induced diaphragmatic dysfunction (VIDD) is characterized by diaphragmatic atrophy and weakness leading to an inability to liberate from the ventilator. Patients with VIDD have increased intensive care unit and hospital length of stay, higher reintubation rates, and need for tracheostomy. There are two commonly used modes of ventilation in the ICU - controlled and support mode ventilation. Conventional practice is to initiate mechanical ventilation with controlled mode followed by a support mode to facilitate weaning and eventual extubation. However, this approach may induce irreversible diaphragmatic atrophy. Observational studies suggest that controlled ventilation is associated with higher rates of diaphragmatic atrophy than support modes of ventilation. Diaphragmatic atrophy occurs within the first 24 hours of mechanical ventilation. To date, it remains unknown whether early initiation of support mode ventilation prevents VIDD and its associated complications in comparison to controlled mode ventilation. The investigators hypothesize that by initiating subjects on support mode ventilation, an associated increase in ventilator-free days will be seen in comparison to subjects on controlled mode ventilation. Subjects on support mode ventilation will have less diaphragmatic atrophy and weakness than subjects on controlled mode ventilation. To investigate this hypothesis,investigators are conducting a phase III randomized trial examining the effects of volume support mode versus assist control mode ventilation on ventilator-free days and rate of diaphragm atrophy. enrolled subjects requiring mechanical ventilation will be randomized to either volume support mode or assist control mode within 24 hours of mechanical ventilation initiation. Diaphragm thickness will be measured by ultrasound daily and subsequently diaphragm atrophy rate will be calculated in each arm. The operator acquiring ultrasound images will be blinded to the ventilator mode that the subject was randomized to. Subjects in the study will follow standard ICU sedation awakening trials and spontaneous breathing trials. The medical team in charge of the subject will determine when the subject will be liberated from the ventilator. There will be up to a 24 hour period from initiation of standard, non-study mechanical ventilation during which the subject can be consented and enrolled. This will allow the research team time to contact the subject and/or family in order to obtain informed consent. Once randomized, all subjects will be initiated on study mode of ventilation. The medical team will direct other aspects of care. The phase III trial will be powered to determine if there is a statistically significant difference in rate of diaphragm atrophy and ventilator-free days between volume support mode and assist control mode.

Diaphragm Atrophy, Ventilator Induced Diaphragm Dysfunction, Mechanical Ventilation, Volume Support Mode, Assist Control Mode, Diaphragm Thickening Fraction, Intubation, Delirium, Ventilator-Free Days

Volume support mode ventilation is a spontaneous mode where a target goal volume is set on the ventilator. This ventilatory strategy is dependent on patients spontaneously breathing and triggering (or activating) the ventilator to support the breath. The ventilator adjusts the amount of pressure support to deliver with each breath (i.e. if the patient's tidal volume is greater than the set target volume, then the ventilator will decrease the amount of pressure support in the subsequent breath to try to achieve the goal volume and vice versa). The respiratory rate is not set in this mode of ventilation and is dependent on the patient. For patients randomized to this mode, the goal tidal volume will be set at 6 cc/kg of ideal body weight (IBW).

In assist control mode ventilation, the machine is programmed to deliver a set tidal volume and set respiratory rate. Patients can breathe over the set respiratory rate, but the volume of breath that they receive is fixed and delivered by the ventilator. For patients randomized to this mode, the tidal volume will be set at 6 cc/kg of ideal body weight (IBW).

This is a spontaneous mode of mechanical ventilation that depends on the patient's efforts. A target volume (6 cc/kg of IBW), PEEP and FiO2 are set by the medical team, and the ventilator varies the inspiratory pressure support with each breath to achieve the target volume. The respiratory rate is fully dependent on the patient. Sedation while on mechanical ventilation will be set at a goal RASS of 0 to -2.

This is a controlled mode of mechanical ventilation that is independent of patient's efforts. A tidal volume (6 cc/kg of IBW), respiratory rate, PEEP and FiO2 are set by the medical team. Sedation while on mechanical ventilation will be set at a goal RASS of 0 to -2.

Noninvasive Measurements of Diaphragm Inspiratory Strength 3.+ 9+ Noninvasive Measurements of Diaphragm Function

(diaphragm thickness at end expiration - diaphragm thickness at end inspiration)/diaphragm thickness at end expiration; measured by ultrasound

Including the Following: -reintubation tracheostomy mechanical ventilation > 14 days patients with delirium

Inclusion Criteria: subjects > 18 years of age that have been intubated and mechanically ventilated for < 36 hours at the time of screening will be eligible for enrollment Exclusion Criteria: pregnancy cardiopulmonary arrest history of diaphragmatic paralysis or neuromuscular disease chronic obstructive pulmonary disease (COPD) or asthma exacerbation with evidence of auto-PEEPing requiring intubation neuromuscular blockade expectation to be liberated from ventilator in < 24 hours history of mechanical ventilation in the last 6 months presence of tracheostomy high cervical spine injury