Hypercarbia during tracheostomy: a comparison of percutaneous endoscopic, percutaneous Doppler, and standard surgical tracheostomy

Objective: Tracheostomy is one of the most commonly performed surgical procedures in the critical care setting. The early use of tracheostomy as a method of primary airway management has been proposed as a means to decrease pulmonary morbidity and to shorten the number of ventilator, intensive care unit, and hospital days. We set out to (1) determine whether hypercarbia occurs during tracheostomy of the critically ill patient and (2) determine the extent to which the partial pressure of carbon dioxide in arterial blood (PaCO2) rises during percutaneous endoscopic, percutaneous Doppler, and standard surgical tracheostomy. Design: Prospective, open clinical trial. Setting: Surgical intensive care unit and operating room in teaching hospitals. Patients: During mechanical ventilation, patients underwent either percutaneous endoscopic (PET), percutaneous Doppler (PDT), or standard surgical tracheostomy (ST), based on surgeon preference. Arterial blood gas readings were obtained approximately every 4 min throughout each procedure. Measurements and results: All tracheostomies were successfully performed. No serious complications (including hypoxia) occurred during the study. Significant (p < 0.05 vs PDT and ST) hypercarbia (maximum Delta PaCO2 24 +/- 3 mmHg) and acidosis (maximum Delta pH 0.16 +/- 0.02) developed during PET. The changes in PaCO, and pH during PDT (maximum Delta PaCO2 8 +/- 2 mmHg; maximum Delta pH - 0.07 +/- 0.02) and ST (maximum Delta PaCO2 3 +/- 1 mmHg; maximum Delta pH - 0.04 +/- 0.01) were markedly less pronounced. Conclusions: Continuous bronchoscopy during percutaneous tracheostomy contributes significantly to early hypoventilation, hypercarbia, and respiratory acidosis during the procedure. Percutaneous tracheostomy, when performed using the Doppler ultrasound method to position the endotracheal tube, significantly reduces CO2 retention when compared to PET. Because of a possible rise in intracranial pressure, the potential for hypercarbia should be considered when choosing the method of tracheostomy in the critically ill and/or head-injured patient, where hypercarbia may be detrimental. If PET is to be performed, steps to minimize occult hypercarbia, such as using the smallest bronchoscope available, minimizing suctioning during bronchoscopy, and minimizing the length of time the bronchoscope is in the endotracheal tube, should be undertaken.