Dyspnea During Mechanical Ventilation

In the past 5 years, there are increasing data suggesting that patients treated with mechanical ventilation experience shortness of breath, despite appropriate sedation. This adverse experience is believed to contribute to the finding that up to 25% of patients who survive severe respiratory diseases experience mental health problems including post traumatic distress syndrome (PTSD). The purpose of this study is to evaluate if/how sequential changes in the delivery of mechanical ventilation affect shortness of breath sensation in awake patients requiring mechanical ventilation. Improving the knowledge of the impact of the patient-ventilator interaction on shortness of breath sensation may lead to strategies to improve the comfort of non-sedated and sedated ventilated patients, and thereby reduce mental health sequelae in survivors of acute severe respiratory diseases The investigators hypothesize that current ventilator strategies, particularly reduced tidal volume (size of breath given by the ventilator) utilized in managing patients with severe respiratory diseases, contribute to shortness of breath in patients with increased drive to breathe. In this setting, some safe ventilator changes may improve or worsen the shortness of breath sensation in awake patients on mechanical ventilation.

The investigators will conduct a prospective, observational, two-center ICU study of 60 subjects on mechanical ventilation with respiratory failure of any cause.