Tachypnea Seen During Positive Airway Pressure Titration Studies: A Case Series of Four Patients.

We report a case series of four patients where tachypnea was observed during positive airway titration studies, double the baseline breathing rate (tachypnea range 46-68 breaths/min). It happened mainly during non-rapid eye movement to rapid eye movement sleep transitions without significant changes in oxygen saturation or signs of autonomic hyperactivity such as an increased heart rate. The increased respiratory rate may be a normal physiological extreme outlier seen during phasic rapid eye movement sleep triggered by high pressure ventilation and it may also indicate underlying ventilatory instability, making patients predisposed to central sleep apnea.