Patients who are dependent on continuous noninvasive intermittent positive pressure ventilation for ventilatory support via angled mouthpiece interfaces during daytime hours often need dental interventions that are prevented by the presence of the mouthpiece. To permit dental interventions, however, the noninvasive intermittent positive pressure ventilation can most conveniently and safely be delivered via nasal interface using oximetry monitoring as long as both sedation and supplemental oxygen are avoided. Three mouthpiece continuous noninvasive intermittent positive pressure ventilation users are described who were switched to nasal noninvasive intermittent positive pressure ventilation to permit dental care. The most common mistake is to fail to cover the nasal interface exhalation portals when switching from ventilatory assistance by bilevel positive airway pressure devices with passive ventilator circuits to portable ventilators with active ventilator circuits and exhalation valves.