Obstructive sleep apnea syndrome (OSA) and periodic limb movement in sleep syndrome (PLMS) are two common sleep disorders. Previous studies showed that OSA and PLMS share common features, such as increased cardio-vascular risk, both apnea events and limb movements occur periodically, they are usually associated with cortical arousals, and both of them can induce declines in peripheral oxygen saturation measured with pulse oximetry. However, the question whether apnea events and limb movements also show similar characteristics in cerebral hemodynamic and oxygenation has never been addressed. In this pilot study, we will first time compare the cerebral hemodynamic changes induced by apnea events and limb movements in patients with OSA (n=4) and PLMS (n=4) with NIRS. In patients with OSA, we found periodic oscillations in HbO2, HHb, and blood volume induced by apnea/hypopnea events, HbO2 and HHb showed reverse changing trends. By contrast, the periodic oscillations linked to limb movements were only found in HbO2 and blood volume in patients with PLMS. These findings of different cerebral hemodynamics patterns between apnea events and limb movements may indicate different regulations of nervous system between these two sleep disorders.
In obstructive sleep apnea syndrome (OSA) the periodic reduction or cessation of breathing due to narrowing or
occlusion of the upper airway during sleep leads to daytime symptoms and increased cardiovascular risk, including stroke.
The higher risk of stroke is related to the impairment in cerebral vascular autoregulation. Continuous positive airways
pressure (CPAP) therapy at night is the most effective treatment for OSA. However, there is no suitable bedside
monitoring method evaluating the treatment efficacy of CPAP therapy, especially to monitor the recovery of cerebral
hemodynamics. NIRS is ideally suited for non-invasive monitoring the cerebral hemodynamics during sleep. In this study,
we will for first time assess dynamic changes of cerebral hemodynamics during nocturnal CPAP therapy in 3 patients
with OSA using NIRS. We found periodic oscillations in HbO2, HHb, tissue oxygenation index (TOI) and blood volume
associated with periodic apnea events without CPAP in all OSA patients. These oscillations were gradually attenuated
and finally eliminated with the stepwise increments of CPAP pressures. The oscillations were totally eliminated in blood
volume earlier than in other hemodynamic parameters. These results suggested that 1) the cerebral hemodynamic
oscillations induced by OSA events can effectively be attenuated by CPAP therapy, and 2) blood flow and blood volume
recovered first during CPAP therapy, followed by the recovery of oxygen consumption. Our study suggested that NIRS is
a useful tool to evaluate the efficacy of CPAP therapy in patients with OSA bedside and in real time.
The hemodynamic changes during natural human sleep are still not well understood. NIRS is ideally suited for monitoring the hemodynamic changes during sleep due to the properties of local measurement, totally safe application and good tolerance to motion. Several studies have been conducted using NIRS in both normal subjects and patients with various sleep disorders during sleep to characterize the hemodynamic changing patterns during different sleep stages and during different symptoms such as obstructive apneas. Here we assessed brain and muscle oxygenation changes in 7 healthy adults during all-night sleep with combined polysomnography measurement to test the notion if hemodynamic changes in sleep are indeed brain specific. We found that muscle and brain showed similar hemodynamic changes during sleep initiation. A decrease in HbO2 and tissue oxygenation index (TOI) while an increase in HHb was observed immediately after sleep onset, and an opposite trend was found after transition with progression to deeper slow-wave sleep (SWS) stage. Spontaneous low frequency oscillations (LFO) and very low frequency oscillations (VLFO) were smaller (Levene’s test, p<0.05) during SWS compared to light sleep (LS) and rapid-eye-movement (REM) sleep in both brain and muscle. Spectral analysis of the NIRS signals measured from brain and muscle also showed reductions in VLFO and LFO powers during SWS with respect to LS and REM sleep. These results indicate a systemic attenuation rather than local cerebral reduction of spontaneous hemodynamic activity in SWS. A systemic physiological mechanism may exist to regulate the hemodynamic changes in brain and muscle during sleep.
Our purpose is to compare the changes in muscle oxygenation in the vastus lateralis (VL) and biceps brachii (BB) muscles simultaneously using near-infrared spectroscopy (NIRS) during incremental rowing exercise in eight rowers. Based on the BB and VL muscle oxygenation patterns, two points are used to characterize the muscle oxygenation kinetics in both the arm and the leg muscles. The first point is the breaking point (Bp), which refers to an accelerated fall in muscle oxygenation that correlates with the gas exchange threshold (GET). The second point is the leveling-off point (Lo), which suggests the upper limit of O2 extraction. The GET occurred at 63.3±2.4% of maximal oxygen uptake (O2 max). The Bp appeared at 45.0±3.8% and 55.6±2.4% O2 max in the BB and VL, respectively. The Lo appeared at 63.6±4.1% and 86.6±1.0% O2 max in these two muscles, respectively. Both the Bp and the Lo occurred earlier in BB compared with VL. These results suggest that arm muscles have lower oxidative capacity than leg muscles during rowing exercise. The rowers with higher exercise performances showed heavier workloads, as evaluated by Bp and Lo. The monitoring of muscle oxygenation by NIRS in arm and leg muscles during rowing could be a useful guide for evaluation and training.
A dual-modality method combining continuous-wave near-infrared spectroscopy (NIRS) and event-related potentials (ERPs) was developed for the Chinese-character color-word Stroop task, which included congruent, incongruent, and neutral stimuli. Sixteen native Chinese speakers participated in this study. Hemodynamic and electrophysiological signals in the prefrontal cortex (PFC) were monitored simultaneously by NIRS and ERP. The hemodynamic signals were represented by relative changes in oxy-, deoxy-, and total hemoglobin concentration, whereas the electrophysiological signals were characterized by the parameters P450, N500, and P600. Both types of signals measured at four regions of the PFC were analyzed and compared spatially and temporally among the three different stimuli. We found that P600 signals correlated significantly with the hemodynamic parameters, suggesting that the PFC executes conflict-solving function. Additionally, we observed that the change in deoxy-Hb concentration showed higher sensitivity in response to the Stroop task than other hemodynamic signals. Correlation between NIRS and ERP signals revealed that the vascular response reflects the cumulative effect of neural activities. Taken together, our findings demonstrate that this new dual-modality method is a useful approach to obtaining more information during cognitive and physiological studies
Functional near-infrared brain imaging (fNIRI) and event-related potential (ERP) were used simultaneous to detect the
prefrontal cortex (PFC) which is considered to execute cognitive control of the subjects while performing the Chinese
characters color-word matching Stroop task with event-related design. The fNIRI instrument is a portable system
operating at three wavelengths (735nm & 805nm &850nm) with continuous-wave. The event-related potentials were
acquired by Neuroscan system. The locations of optodes corresponding to the electrodes were defined four areas
symmetrically. In nine native Chinese-speaking fit volunteers, fNIRI measured the hemodynamic parameters (involving
oxy-/deoxy- hemoglobin) changes when the characteristic waveforms (N500/P600) were recorded by ERP. The
interference effect was obvious as a longer reaction time for incongruent than congruent and neutral stimulus. The
responses of hemodynamic and electrophysiology were also stronger during incongruent compared to congruent and
neutral trials, and these results are similar to those obtained with fNIRI or ERP separately. There are high correlations,
even linear relationship, in the two kinds of signals. In conclusion, the multi-modality approach combining of fNIRI and
ERP is feasible and could obtain more cognitive function information with hemodynamic and electrophysiology signals.
It also provides a perspective to prove the neurovascular coupling mechanism.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.