- bmi ≥ 45 kg/m2 - pregnancy - chest tube placement - hemodynamic instability with mean arterial pressure < 60 mmhg - thoracic or abdominal wounds - chest wall deformities - vertebral column deformities that would preclude prone positioning - facial trauma or surgery in the last 30 days - established diagnosis of interstitial lung disease - prior single or double lung transplant - surgery for spine, femur, or pelvis in the last 3 months - thoracic or cardiac surgery in the last 30 days - pacemaker placement last 7 days

- bmi ≥ 45 kg/m2 - pregnancy - chest tube placement - hemodynamic instability with mean arterial pressure < 60 mmhg - thoracic or abdominal wounds - chest wall deformities - vertebral column deformities that would preclude prone positioning - facial trauma or surgery in the last 30 days - established diagnosis of interstitial lung disease - prior single or double lung transplant - surgery for spine, femur, or pelvis in the last 3 months - thoracic or cardiac surgery in the last 30 days - pacemaker placement last 7 days