Mechanical Ventilator Adjustments and Patient Dyspnea

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.

Inclusion Criteria: * Admitted to a participating ICU at BIDMC * Requiring mechanical ventilation * Awake by both of the following criteria * RASS -2 to +2\* * CAM-ICU negative‡ * Able to communicate/answer dyspnea questionnaire * RASS (Richmond Agitation-Sedation Scale) is a validated scale commonly used in the ICU to assess patient's level of sedation and agitation. It ranges from -5 to +4. While -5 means an unarousable coma, +4 means violent patient with immediate self danger. The scale from -2 to +2 ranges from light sedation to agitated. * CAM-ICU (Confusion Assessment Method) is an ICU validated scale used to assess the presence of delirium. A negative CAM-ICU scale has good positive and negative predictive value to diagnose or exclude delirium. Physicians and nurses are trained to evaluate patients using both scales Exclusion Criteria: * Age \< 18 years old * Comfort measures only * Hemodynamic instability (MAP \< 65 mmHg) or increasing requirement of vasopressor * PEEP \> 10 cmH2O * FiO2 \> 0.6 * Current Prone position * Current Pneumothorax * Bronchopleural fistula * Neuromuscular conditions that impair responding to the dyspnea scale or expression * Dementia * Prisoners * Pregnant women * Patients intubated and ventilated for less than 12 hours during the current ventilation episode * pH \< 7.20 or \> 7.55 * Presence of chest tube * Status post thoracotomy * Treating clinician refusal