After documenting the presence of obstructive sleep apnea syndrome (OS
AS) through polysomnographic monitoring, we performed simultaneous amb
ulatory recordings of electrocardiogram, oronasal airflow, and pulse o
ximetry on 12 OSAS patients with normal autonomic nervous function for
a period of 24 hours. The power spectrum of heart rate variability wa
s investigated before and during treatments using dental appliances. F
requency domain analysis showed that the very low frequency component
of heart rate (0.008-0.04 Hz) was increased in OSAS patients and that
a very low frequency peak appeared during episodes of obstructive slee
p apnea. The increase in very low frequency identification was synchro
nized with episodes of absence of air exchange or hypoxemia (decreased
arterial oxygen saturation) that occurred repeatedly at a cycle lengt
h of 25-120 seconds in our subjects. Frequency domain analysis of hear
t rate variability before and during prosthetic mandibular advancement
treatment showed that only the very low frequency was significantly d
ecreased during prosthetic mandibular advancement treatment, whereas t
he other frequencies, i.e. high, low, and ultralow frequency component
values, showed no significant changes. Time domain analysis of heart
rate variability before and during prosthetic mandibular advancement t
reatment showed no significant changes in any of these parameters. Fre
quency domain analysis of heart rate variability during nocturnal slee
p, especially investigation of very low frequency and very low frequen
cy peak, can be a noninvasive low-cost approach to diagnose and even b
etter monitor subjects undergoing treatment at home, particularly cons
idering that R-R intervals can be extracted from pulse oximetry and th
at analysis software programs are already commercially available.