Permissive hypercapnia combined with low-level PEEP in bullous emphysema patient undergoing cardiac surgery: a case report and literature review

Background: Bullous emphysema is characterized by destruction of lung parenchyma, reduction in elasticity of the lung, hyperinflation, and ventilation/perfusion mismatch. Ventilatory management of the patient with bullous emphysema is challenging, and especially so for the patient undergoing cardiac surgery. Case report: A 47-yearold man with severe diffuse bullous emphysema requested general anesthesia for tricuspid valve replacement under cardiopulmonary bypass (CPB). Preoperative physical examination detected signs of right heart dysfunction, arterial blood gas (ABG) analysis revealed the partial pressure of CO2 in arterial blood (PaCO2) was 62 mmHg. Echocardiogram detected severe tricuspid regurgitation and pulmonary hypertension. After induction of anesthesia, the lungs were ventilated using volume-controlled ventilation, with a low-tidal volume (6 mL/kg) and a low-level PEEP (5 cmH2O). Under these conditions, ABG analysis revealed PaCO2 64 mmHg. The patient underwent tricuspid valve replacement under CPB. ABG analysis was performed at 20, 60, and 95 minutes following initiating CPB, the PaCO2 was 43, 42, and 36 mmHg, respectively. Forty-five minutes after weaning CPB, ABG analysis showed that the PaCO2 was 64 mmHg. The postoperative period was uneventful and there was not marked ventilator-associated pulmonary complications. Conclusions: Permissive hypercapnia combined with a low level of PEEP as a ventilatory strategy provided adequate oxygenation and minimized ventilator-induced lung injury in the patients with bullous emphysema undergoing cardiac surgery.