Study: NCT02367170

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Midazolam
Description: In the event a subject shows signs of distress during the Bilateral phrenic nerve stimulation and measurement of transdiaphragmatic pressures, a dose of Midazolam is available. IV (in the vein) dose from 0.5 mg to 2 mg.

Intervention type: DRUG
Group type: SHAM_COMPARATOR
Intervention: Midazolam
Description: In the event a subject shows signs of distress during the Bilateral phrenic nerve stimulation and measurement of transdiaphragmatic pressures, a dose of Midazolam is available. IV (in the vein) dose from 0.5 mg to 2 mg.

Intervention type: PROCEDURE
Group type: EXPERIMENTAL
Intervention: Volitional Measurement of Maximal Inspiratory Pressure (MIP)
Description: MIP is tested on all subjects on day 1, every 7 days after and on the last day of participation. To measure MIP, a subject will be suctioned, disconnected from the ventilator, and instructed to take a few spontaneous breaths. A 1-way exhalation valve connected to a NICO respiratory monitor will be placed on the ET/tracheotomy tube. The subject will be instructed to inhale and exhale as forcefully as possible for 20 seconds, followed by at least 2 minutes of rest on full mechanical ventilation support. MIP trials will be repeated 3 times, and the greatest negative pressure recorded with a NICO respiratory monitor connected to a laptop computer, which will digitize airway pressure, flow and volume signals at 100Hz. This allows for analysis of the individual pressure waves, facilitating pre-post comparisons of MIP at specific time points during inspiration.

Intervention type: PROCEDURE
Group type: SHAM_COMPARATOR
Intervention: Volitional Measurement of Maximal Inspiratory Pressure (MIP)
Description: MIP is tested on all subjects on day 1, every 7 days after and on the last day of participation. To measure MIP, a subject will be suctioned, disconnected from the ventilator, and instructed to take a few spontaneous breaths. A 1-way exhalation valve connected to a NICO respiratory monitor will be placed on the ET/tracheotomy tube. The subject will be instructed to inhale and exhale as forcefully as possible for 20 seconds, followed by at least 2 minutes of rest on full mechanical ventilation support. MIP trials will be repeated 3 times, and the greatest negative pressure recorded with a NICO respiratory monitor connected to a laptop computer, which will digitize airway pressure, flow and volume signals at 100Hz. This allows for analysis of the individual pressure waves, facilitating pre-post comparisons of MIP at specific time points during inspiration.

Intervention type: DEVICE
Group type: EXPERIMENTAL
Intervention: Inspiratory Muscle Strength Training (IMST)
Description: Occurs 5 days/wk using threshold IMST device-Respironics model 735. Prior to training, cuff pressure is assessed, FiO2 increased for 2 min. to keep O2 sats ≥92%. The ventilator circuit is disconnected, IMST device is attached to endotracheal or tracheotomy tube and subject is instructed to exhale then forcefully inhale for 10 breaths. The initial setting of device is set to -5cmH2O, subject must generate a negative inspiratory pressure more negative than -5cmH2O to open spring-loaded valve and receive inspiratory airflow. Pressure setting is made more negative/difficult to open by 2-5cm every few breaths until a setting is found where the patient has difficulty fully opening valve, resulting in valve flutter noise. Training pressure is then made more positive /easier by 2-4cm of H2O, so subject can fully open valve, and 4 sets of 6-10 breaths are completed. Training pressures advanced as rapidly as possible, provided the patient is able to open the valve withoutvalve flutternoise.

Intervention type: DEVICE
Group type: SHAM_COMPARATOR
Intervention: SHAM Inspiratory Muscle Strength Training (IMST)
Description: Training will also be conducted 5 days/wk with an identical IMST device that has been modified by removing the valve leaflet, which essentially removes all inspiratory loading by the device. The modified SHAM IMST device makes a whistling sound during inspiration, which enhances the sham effect. For SHAM treatment, supplemental oxygen FiO2 will be increased for two minute prior to each bout. The ventilator will be disconnected and a SHAM device will be attached to the endotracheal or tracheostomy tube. The subject will be instructed to take 6-10 breaths with a normal tidal volume through the SHAM device and will be reconnected to the ventilator for a 2-minute rest period. The process will be repeated 3 more times for a total of 4 sets of 6-10 breaths.