Occult hypercarbia. An unrecognized phenomenon during percutaneous endoscopic tracheostomy

Bronchoscopy has been incorporated as a useful adjunct to increase the safety and effectiveness of percutaneous endoscopic tracheostomy (PET). Insertion of the bronchoscope, along with the intraluminal dilators of the PET set, into the airway potentially leads to hypoventilation and hypercarbia during the procedure. Using continuous in-line arterial blood gas monitoring, we documented profound hypercarbia in two patients undergoing PET in the surgical ICU. In a third patient, the rise in PaCO2 was accompanied by a marked rise in intracranial pressure (ICP), and a corresponding fall in cerebral perfusion pressure. While transient hypercarbia seems well tolerated by most patients, this phenomenon and its effect on cerebral blood flow should be strongly considered before performing PET on the critically ill patient with evidence of elevated ICP.