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. Author manuscript; available in PMC: 2020 May 1.
Published in final edited form as: Auton Neurosci. 2019 Feb 15;218:10–15. doi: 10.1016/j.autneu.2019.02.003

Figure 1. Polysomnography of a 19-year-old patient with FD and severe sleep-disordered breathing.

Figure 1.

The tracing shows two apnea episodes (airflow tracing flattening). During these, O2 saturation (SatO2) decrease and EtCO2 increase, as expected, but the R-R interval increases, i.e., heart rate decreases (see arrows). This is in contrast to the expected tachycardia that typically accompanies hypoxia in patients with typical sleep apnea. Note that the patient had relatively moderate hypercapnia (his highest EtCO2 was 51 mmHg) and mild hypoxia (his lowest O2 was 94%) but his heart rate declined from 75 of 50 bpm during the apneas. It is conceivable that more pronounced hypoxia and/or hypercapnia episodes could result in more severe bradycardia, arrhythmias and cardiac arrest.