Online Supplement
A computer based software system (XL-TEK, Oakville, Ontario, Canada). A standard overnight PSG included a
4 lead electoencephalogram (EEG) (C3, C4, O1, and O2), two bilateral electrooculogram (EOG) leads
referenced to A1 or A2, one submental and two tibial electromyograms (EMG). Respiratory measurements
included chest wall and abdominal movement using inductance pneumography; airflow using a nasal cannula
connected to a Nasal Pressure Airflow (NPAF) by Braebon; oxygen saturation (SaO2) using a Massimo pulse
oximeter (Irvine, CA); transcutaneous carbon dioxide measurement (TcCO2) using a LINDE carbon dioxide
sensor (Munich, Germany); and end tidal carbon dioxide measurements (et CO2) using a Capnocheck (Smiths
Medical, Ashford, Kent, UK). Video and audio recordings were obtained for each study. Sleep architecture was
assessed by standard techniques.
Online Supplement Table 1: Sleep Disordered Breathing and Polysomnogram Definitions
Term
Obstructive apnea
Definition
Reduction in flow by 90% for ≥ 90% of the event, accompanied by continued
inspiratory effort throughout and lasting for the duration of at least 2 breaths
Obstructive hypopnea
Reduction in flow by 30%, for ≥ 90% of the event, the event lasts at least 2
missed breaths (or the duration of 2 breaths as determined by the baseline
breathing pattern ) accompanied by either an arousal, awakening or ≥3% drop
in oxygen saturation
Mixed apnea
Reduction in flow by 90% for ≥ 90% of the event, accompanied by absent
inspiratory effort during the initial part of the event followed by resumption of
effort before the end of the event and lasting for the duration of at least 2
breaths
Central apnea
The event is associated with absent inspiratory effort throughout the entire
duration of the event and one of the following criteria is met: the event lasts
20 seconds or longer or the event lasts at least 2 missed breaths (or the
duration of 2 breaths as determined by the baseline breathing pattern ) and is
associated with an arousal, awakening or ≥ 3% desaturation
Central hypopnea
Reduction in flow by 30%, for ≥ 90% of the event, the event lasts at least 2
missed breaths (or the duration of 2 breaths as determined by the baseline
breathing pattern ) accompanied by either an arousal, awakening or ≥3% drop
in oxygen saturation in the absence of snoring, paradox and increased
inspiratory flattening of the flow signal compared to baseline breathing
Obstructive apnea-hypopnea index
(OAHI)
The number of obstructive apneas, obstructive hypopneas and mixed apneas
per hour
Central apnea-hypopnea index (CAHI)
The number of central apneas and central hypopneas per hour
Hypoventilation
The end tidal or transcutaneous carbon dioxide level greater than 50mmHg for
greater than or equal to twenty-five percent of the night
Obstructive Sleep Apnea (OSA)
OAHI > 2 events/hr
Moderate-severe OSA
OAHI ≥5 events/hr
Clinically significant Central sleep apnea
(CSA)
Combined Sleep Apnea
CAHI ≥ 5 events/hr
Moderate-severe combined sleep apnea
Combined AHI ≥ 5 events/hr
Combined AHI ≥ 2 events/hr