GO2 PEEP Study: Bidirectional Oxygenation Valve in Postoperative Atelectasis

Postoperative pulmonary complications (PPCs) are the principal cause of morbidity, mortality and prolonged hospitalizations in surgical patients, which results in a 50% increase in healthcare costs compared to postoperative cardiac complications. This is especially evident following cardiovascular surgery. One of the most common PPCs is atelectasis, resulting in dyspnea, tachypnea and hypoxemia.

Postoperative atelectasis is a predictable consequence of anesthesia, surgical trauma, and pain associated with breathing. Methods aimed at increasing lung volume and treating atelectasis, commonly known as postoperative physiotherapy, play an important role in preventing PPCs. These methods include cough and deep breathing, continuous positive airway pressure (CPAP), postural drainage, incentive spirometry and positive end expiratory pressure (PEEP).

Incentive spirometry has served as a convenient approach for the postoperative patient to sustain maximal inflations and encourage deep breathing. Although incentive spirometry is used commonly by post-operative patients, evidence fails to support its benefit.

PEEP is a well-known pulmonary physiologic principle. There are on average 600 million alveoli in the lung. Each alveolus has surfactant to resist the natural propensity for these small air sacs to collapse during exhalation. Despite this surfactant, some alveoli will collapse and not be available for gas exchange. This atelectasis results in a ventilation/perfusion mismatch where alveolar units are perfused but not adequately ventilated. This is referred to as shunting and results in hypoxemia (decreased PaO2). PEEP decreases the propensity for the alveoli to collapse by increasing the air pressure in the lungs. This residual pressure in the lungs at the end of exhalation decreases shunting and allows for more complete gas exchange and improved oxygenation. In patients, PEEP is one of the safest ways to increase PaO2 and is used on almost all modern ventilator settings.

The purpose of this study is to compare a novel breathing device, called the GO2 Mouthpiece, which uses the concept of PEEP, to the incentive spirometer in postoperative patients.

Inclusion criteria

• Undergoing coronary artery bypass surgery (CABG) and/or valve replacement surgery
• Able to provide written informed consent
• Maintenance of an arterial line postoperatively

Exclusion criteria

• Active smoking, within three months of surgery
• Forced expiratory volume in one second (FEV1) <75% predicted
• Relative risk to develop pulmonary barotrauma as evident by history of pneumothorax or emphysema
• Unable or unwilling to provide informed consent, cognitive impairment