Neurally Adjusted Ventilatory Assist (NAVA) is a new mode of mechanical ventilation that is controlled by the electrical activity of the diaphragm (EAdi). The EAdi is a signal that represents the patient's breathing effort, and hence with NAVA, the assist being delivered is synchronized and proportional to the demands of the patient. This is a prospective physiological study of the feasibility of NAVA ventilation over 24 hours. The aim is to demonstrate that NAVA can maintain spontaneous breathing and unload the respiratory muscles during both sleep and wake cycles over a 24 hour period.

To date, studies using NAVA technology have been limited to short term evaluations (under 3 hours). No serious adverse events have been observed in patients enrolled in our 3-hour study of NAVA in patients with acute lung injury. All 15 patients successfully tolerated the period of ventilation (i.e. there were no dropouts) with NAVA and the stability of the blood gas parameters over time reveals the efficiency of this new mode of ventilation in regards to oxygenation.

A longer study may help to evaluate patient tolerance of NAVA and stability over time. A longer study will also demonstrate the feasibility of NAVA to adapt to changes in respiratory drive, changes in patient status, and the interventions of health care providers. A longer time frame should help us understand the parameters for titration of NAVA settings over time and establish some indications/limits for the future use of this promising technique. This intermediate study will generate the data necessary for the development of additional protocols to refine NAVA application and to compare NAVA to other assist modes.

Inclusion Criteria:

• Patients admitted to the ICU will be screened on a daily basis for the presence of the following characteristics:

• Adult (>18 years old) intubated and mechanically ventilated patients with evidence of spontaneous breathing defined as:

  1. Patient is on pressure support ventilation OR
  2. Patient is on pressure control ventilation with the ability to trigger 50% of the breaths.

• Sedation Agitation Score (SAS) score greater than or equal to 2

• Presence of an arterial line

• Patients meeting these criteria will be considered eligible for recruitment into the study

General Exclusion Criteria:

• Next of kin unavailable
• Patient/next of kin refuses informed consent.
• Attending physician refuses to allow enrollment
• Pregnancy

Exclusion Criteria Related to the Technique:

• Any contraindication to insertion of a nasogastric tube including, but not limited to: severe oropharyngeal malformation or bleeding, esophageal varices, tumor, infection, stenosis, or rupture
• Hemophilia or other severe bleeding disorder
• Presence or suspicion of central/brain stem neurologic disorder/severe neuromuscular disease
• Treatment with neuromuscular blockers
• History of heart and/or lung transplantation

Exclusion Criteria Related to the Clinical Stability of the Patient:

• Mean arterial blood pressure < 60 mm Hg with or without vasopressors or inotropes
• Any contraindication to reducing sedation to obtain a targeted SAS score of 3 (e.g. anticipated hemodynamic instability after reduction of sedation)
• Patients with evidence of any of the above exclusions will not be eligible for enrollment in this study