6MWT	Six-Minute Walk Test
AHI	Apnea-Hypopnea Index
ANS	Autonomic Nervous System
BiPAP	Bilevel Positive Airway Pressure
BMI	Body Mass Index
COPD	Chronic Obstructive Pulmonary Disease
CPAP	Continuous Positive Airway Pressure
ECG	Electrocardiogram
HF	High Frequency
HRV	Heart Rate Variability
LF	Low Frequency
LF/HF	Low Frequency to High Frequency Ratio
NN intervals	Normal-to-Normal Intervals
OSA	Obstructive Sleep Apnea
OSAS	Obstructive Sleep Apnea Syndrome
PRV	Pulse Rate Variability
REM	Rapid Eye Movement
SDNN	Standard Deviation of NN Intervals
SDNNI	Standard Deviation of the NN Interval Index