This is a prospective, randomized, blinded study with a control group. The study group will receive mechanical ventilatory support during CBB, which consists of a preset/predetermined tidal volume, respiratory rate, positive pressure at the end of expiration and FIO2. The control group will receive CPB without additional mechanical ventilatory support during surgery, which at present is the standard of care.
The difference between the study and the control group will occur during the time the heart is arrested and the lungs, under present standard of care, are no longer ventilated. It is at this point in time that those in the study group will continue to receive ventilation, intermittent positive pressure ventilation, while their heart is arrested. The subjects will have their lungs ventilated six times per minute with a tidal volume equal to 7-10 milliliters per kilogram. This range, when combined with a consistent PEEP of 5cm of water pressure, will allow for the peak inspiratory pressure to be maintained at or below 40cm of water pressure. In addition, the FIO2 will remain consistent at the same level that was needed to maintain the pulse oximetry at 94% as well as the end-tidal CO2 at 35mmHg. The values mentioned for this study have been chosen based on not only investigator preference, but also on what is considered "minimally necessary" to prevent atelectasis. Multiple studies have been done utilizing PEEP at 5 and 10 cm of water pressure. With the exception of the potential for mechanical ventilation during the CBP, the care of the subject, regardless of the group randomized into, will be the same. We will in all other aspects continue to utilize the current standard of care.
