Resources to be able to screen and enroll patients are no longer available.

This study will evaluate the correlation between invasively measured parameters (work of breathing/power of breathing, resistance and elastance), derived using esophageal pressure measurements, and their corresponding non-invasive estimated values (noninvasive work of breathing/power of breathing, resistance and elastance), computed using airway pressure and flow measurements only.

This study will evaluate the correlation between invasively measured parameters (work of breathing/power of breathing, resistance and elastance), derived using esophageal pressure measurements, and their corresponding non-invasive estimated values (noninvasive work of breathing/power of breathing, resistance and elastance), computed using airway pressure and flow measurements only. Vent settings will be adjusted to test accuracy over a range of respiratory support conditions.

Inclusion Criteria:

• Adult medical/surgical ICU patients (Age≥18) on mechanical ventilation for respiratory failure, spontaneously breathing and receiving eligible for pressure support ventilation (PSV).

Exclusion Criteria:

• Prisoners and patients with closed-head injury (e.g., trauma), hemodynamic instability, multiple organ system failure or late term pregnancy will not be studied.