OBJECTIVE To determine the patency of standard and modified Portex tracheostomy tubes inserted by the percutaneous dilatational technique. METHODS Prospective observational study. METHODS Medical-surgical ICUs in a tertiary care community hospital. METHODS Medical-surgical ICU patients requiring tracheostomy. METHODS Consecutive medical-surgical ICU patients requiring tracheostomy were eligible for the study. Percutaneous tracheostomy tubes were inserted using the percutaneous dilatational technique with bronchoscopic guidance. The study population consisted of the following two groups: group 1 (receiving the standard Portex Per-fit percutaneous tracheostomy tube); and group 2 (receiving the modified Portex Per-fit percutaneous tracheostomy tube). Patients underwent daily fiberoptic evaluation to assess tracheostomy tube patency following the first 72 h after the tracheostomy tube placement. Demographic data and clinical signs or symptoms of airway obstruction were recorded. RESULTS Thirty-seven patients received the standard percutaneous tracheostomy tube (group 1), and 17 patients received the modified percutaneous tracheostomy tube (group 2). Partial tracheostomy tube occlusion (> 25%) was observed in 21 of 37 group 1 patients (57%) and in 1 of 17 group 2 patients (6%; p < 0.005). Fifteen of 37 group 1 patients (41%) and none of the group 2 patients sustained a > or = 40% occlusion of the distal tracheostomy tube opening (p < 0.005). One patient from group 1 had clinical manifestations of tracheostomy tube obstruction. None of the patients in group 2 experienced signs or symptoms of airway obstruction. CONCLUSIONS The standard Portex Per-fit percutaneous tracheostomy tubes used in this study were associated with partial airway obstruction. Modifications of the standard Portex percutaneous tracheostomy tube markedly decreased the airway obstruction. Due to the findings in this study, the authors recommend abandoning the continued use of the Portex Per-fit percutaneous tracheostomy tube in its current configuration and replacing it with the modified tracheostomy tube described in this study.