Review of new pre-clinical data

Intrathoracic pressure regulation (IPR) therapy, delivered by impedance threshold devices (ITDs) or intrathoracic pressure regulators (ITPRs), increases venous return, preload, cardiac output, blood pressure, and cerebral perfusion pressure by intermittently creating negative intrathoracic pressure, which improves circulation in hypotensive animals and humans. By increasing systemic pressure and cerebral perfusion as well as promoting venous return, IPR therapy potentially improves cerebral oxygenation. The lower intrathoracic pressures may also reduce pulmonary artery pressure, although there is currently little evidence one way or the other. Use of an ITPR can counteract the multifactorial intraoperative hypotension common during surgeries under general anesthesia, and reduce the need for other measures to treat such hypotension; however, they might simultaneously promote pulmonary complications.

The investigators will therefore assess whether the use of intrathoracic pressure regulation in adults having shoulder surgery under general anesthesia in the sitting position reduces vasoactive medication requirements compared with routine clinical practice. Simultaneously, the investigators will assess the effect of intrathoracic pressure regulation on pulmonary circulation, cerebral oxygenation, and postoperative atelectasis.

Inclusion Criteria:

• Age ≥18 years
• American Society of Anesthesiologists (ASA) physical status class ≤3
• Scheduled for surgery in sitting/ beach-chair positions under general anesthesia in the Cleveland Clinic main campus
• Planned length of surgery >60 minutes

Exclusion Criteria:

• Severe peripheral vascular disease or other contraindication for use of vasopressor infusion
• Obstructive lung disease - moderate or severe asthma or COPD
• Baseline hypoxemia (SpO2<92% on room air)
• Body Mass Index (BMI) >35
• Congestive heart failure
• Pneumothorax or hemothorax
• Uncontrolled hemorrhage
• Planned intraoperative hypotension
• Contraindication to trans-esophageal echocardiography (esophageal stricture, surgery involving the esophagus or stomach)