1. inability to follow commands (e.g., delirium, dementia) 2. indication for mechanical ventilation (e.g., reduced level of consciousness, rapid clinical deterioration) 3. contraindication to prone positioning (spinal cord injury, unstable c-spine, pelvic fracture, unstable airway, open chest or abdomen, anterior chest tube, recent abdominal surgery in past 14 days) 4. patients on home cpap (continue positive airway pressure) 5. transfer from icu in past 72 hours 6. need for telemetry at the time of randomization 7. pregnant (i.e., more than 20 weeks) 8. body mass index above 40 kg/m2 (based on clinician's assessment) 9. recently completed or plan for intrathoracic or intra-abdominal surgical procedure 10. severe hemoptysis 11. pace-maker inserted in past 48 hours

1. inability to follow commands (e.g., delirium, dementia) 2. indication for mechanical ventilation (e.g., reduced level of consciousness, rapid clinical deterioration) 3. contraindication to prone positioning (spinal cord injury, unstable c-spine, pelvic fracture, unstable airway, open chest or abdomen, anterior chest tube, recent abdominal surgery in past 14 days) 4. patients on home cpap (continue positive airway pressure) 5. transfer from icu in past 72 hours 6. need for telemetry at the time of randomization 7. pregnant (i.e., more than 20 weeks) 8. body mass index above 40 kg/m2 (based on clinician's assessment) 9. recently completed or plan for intrathoracic or intra-abdominal surgical procedure 10. severe hemoptysis 11. pace-maker inserted in past 48 hours

inability to follow commands (e.g., delirium, dementia) indication for mechanical ventilation (e.g., reduced level of consciousness, rapid clinical deterioration) contraindication to prone positioning (spinal cord injury, unstable c-spine, pelvic fracture, unstable airway, open chest or abdomen, anterior chest tube, recent abdominal surgery in past 14 days) patients on home cpap (continue positive airway pressure) transfer from icu in past 72 hours need for telemetry at the time of randomization pregnant (i.e., more than 20 weeks) body mass index above 40 kg/m2 (based on clinician's assessment) recently completed or plan for intrathoracic or intra-abdominal surgical procedure severe hemoptysis pace-maker inserted in past 48 hours

inability to follow commands (e.g., delirium, dementia) indication for mechanical ventilation (e.g., reduced level of consciousness, rapid clinical deterioration) contraindication to prone positioning (spinal cord injury, unstable c-spine, pelvic fracture, unstable airway, open chest or abdomen, anterior chest tube, recent abdominal surgery in past 14 days) patients on home cpap (continue positive airway pressure) transfer from icu in past 72 hours need for telemetry at the time of randomization pregnant (i.e., more than 20 weeks) body mass index above 40 kg/m2 (based on clinician's assessment) recently completed or plan for intrathoracic or intra-abdominal surgical procedure severe hemoptysis pace-maker inserted in past 48 hours

1. inability to follow commands (e.g., delirium, dementia) 2. indication for mechanical ventilation (e.g., reduced level of consciousness, rapid clinical deterioration) 3. contraindication to prone positioning (spinal cord injury, unstable c-spine, pelvic fracture, unstable airway, open chest or abdomen, anterior chest tube, recent abdominal surgery in past 14 days) 4. patients on home cpap (continue positive airway pressure) 5. transfer from icu in past 72 hours 6. need for telemetry at the time of randomization 7. pregnant (i.e., more than 20 weeks) 8. body mass index above 40 kg/m2 (based on clinician's assessment) 9. recently completed or plan for intrathoracic or intra-abdominal surgical procedure 10. severe hemoptysis 11. pace-maker inserted in past 48 hours

1. inability to follow commands (e.g., delirium, dementia) 2. indication for mechanical ventilation (e.g., reduced level of consciousness, rapid clinical deterioration) 3. contraindication to prone positioning (spinal cord injury, unstable c-spine, pelvic fracture, unstable airway, open chest or abdomen, anterior chest tube, recent abdominal surgery in past 14 days) 4. patients on home cpap (continue positive airway pressure) 5. transfer from icu in past 72 hours 6. need for telemetry at the time of randomization 7. pregnant (i.e., more than 20 weeks) 8. body mass index above 40 kg/m2 (based on clinician's assessment) 9. recently completed or plan for intrathoracic or intra-abdominal surgical procedure 10. severe hemoptysis 11. pace-maker inserted in past 48 hours