Pulse transit time changes in subjects exhibiting sleep disordered breathing

Evaluating changes in pulse transit time drop index in patients with obstructive sleep apnea before and during CPAP therapy

Airflow limitation in patients with obstructive sleep apnea (OSA) leads to arousal, increased sympathetic nervous system activity, and elevated blood pressure, which causes a decrease in pulse transit time (PTT). The present study aims to evaluate the effect of CPAP therapy on PTT in patients with moderate to severe OSA. This was a cross‐sectional study. Split‐night polysomnography (PSG) study was performed for each participant with apnea‐hypopnea index (AHI) ≥ 15 before and during CPAP therapy. The PTT was calculated as the time interval between the R wave of the electrocardiogram and the following arrival point in fingertip photoplethysmography. PTT drop was defined as a fall in the PTT curve of ≥15 ms lasting at least for 3 s and at most for 30 s. PTT drop index was defined as the number of drops in PTT that occur per hour of sleep. A total of 30 patients were included. PTT significantly increased, and PTT drop index significantly decreased during CPAP therapy (P < 0.001). PTT was significantly correlated to sleep efficiency (r_s = −0.376, P = 0.049) and oxygen desaturation index (ODI) (r_s = −0.428, P = 0.018). PTT drop index was strongly correlated to AHI (r_s = 0.802, P < 0.001), respiratory disturbance index (RDI) (r_s = 0.807, P < 0.001), ODI (r_s = 0.693, P < 0.001), arousal index (r_s = 0.807, P < 0.001), and periodic leg movement (PLM) index (r_s = 0.400, P = 0.035). Overall, the findings from this study indicated that the PTT drop index is a non‐invasive and useful marker for evaluating the severity of OSA and the effectiveness of treatment in patients with moderate to severe OSA.

Scoring heart rate increases as a surrogate arousal marker on portable monitor studies for obstructive sleep apnea: Impact on diagnostic accuracy and clinical decision-making

Cortical arousal-related hypopneas are not scored on type 3 home devices, which therefore limits their diagnostic accuracy for obstructive sleep apnea. The objective of this study was to evaluate whether scoring heart rate accelerations as surrogate markers of arousal improves type 3 portable monitor diagnostic agreement compared with polysomnography and improves therapeutic decision-making. We prospectively recruited patients evaluated for obstructive sleep apnea to undergo in-laboratory simultaneous full polysomnography + type 3 portable monitoring. Hypopnea events were scored on portable monitor studies with and without autonomic scoring, which was defined as an associated increase in pulse oximetry-derived heart rate ≥6 beats per min (autonomic hypopnea). Portable monitor diagnostic agreement compared with polysomnography with and without autonomic hypopnea scoring was assessed. We also evaluated whether reporting autonomic hypopnea scoring improves portable monitor clinical treatment decision agreement after four physicians reviewed clinical data and sleep study results (polysomnography, portable monitor with autonomic hypopnea, portable monitor without autonomic hypopnea). Eighty-two participants completed simultaneous polysomnography and in-laboratory portable monitor studies. Scoring autonomic hypopnea resulted in a decreased mean difference between in-laboratory portable monitor respiratory event index and polysomnography apnea-hypopnea index in Bland-Altman analysis (mean difference 14.6 per hr without versus 6.1 per hr with autonomic hypopnea scoring [p ˂ 0.01]), and increased intraclass correlation from 0.769 to 0.844. Inclusion of autonomic hypopnea scoring resulted in better accuracy between portable monitor and polysomnography expert's treatment decisions, and ultimately resulted in 24% fewer additional polysomnographies requested. The addition of pulse oximetry heart rate increases for autonomic hypopnea scoring during portable monitor resulted in better diagnostic agreement, improved clinical decision-making and reduced additional polysomnography testing.

Fluctuaciones nocturnas de presión arterial en el síndrome de apnea-hipopnea obstructiva del sueño

Objective

Patients with sleep apnea/hypopnea syndrome and episodes of increased systolic pressure during sleep, with and without arterial hypertension, and HT as a marker of increased cardiovascular risk, were studied in a prospective study. The objective of our study was to demonstrate that patients with increased systolic pressure during sleep who also had arterial hypertension had a higher cardiovascular risk than non-hypertensive patients.

Methods

We analyzed various biometric (muscle mass index, baseline blood pressure) and polysomnographic parameters, including AHI (apnea-hypopnea index/hour), O2 desaturation index/hour, arousal index, baseline and minimum O2 saturation and the proportion of different sleep phases, together with comorbidities and associated treatments in patients with sleep apnea/hypopnea syndrome (64 with arterial hypertension and 38 non-hypertensive patients) with episodes of increased systolic blood pressure during sleep during polysomnographic studies conducted between 2013 and 2017 and in 2020.

Results

There were no statistically significant differences in the different parameters between study groups. Patients in both groups developed comorbidities in the follow-up period, more frequently in the hypertensive group, and required new treatments, especially the group of patients with HT.

Conclusion

Episodes of increased systolic pressure during sleep suggest an increased cardiovascular risk in patients with sleep apnea syndrome and arterial hypertension in terms of associated comorbidities. However, in non-hypertensive patients, episodes of increased systolic pressure may also be associated with a higher risk of vascular comorbidities (higher than the risk associated with isolated obstructive sleep apneas).

Artifacts in pulse transit time measurements using standard patient monitoring equipment

Objective

Pulse transit time (PTT) refers to the time it takes a pulse wave to travel between two arterial sites. PTT can be estimated, amongst others, using the electrocardiogram (ECG) and photoplethysmogram (PPG). Because we observed a sawtooth artifact in the PTT while using standard patient monitoring equipment for ECG and PPG, we explored the reasons for this artifact.

Methods

PPG and ECG were simulated at a heartrate of both 100 and 160 beats per minute while using a Masimo PPG post-processing module and a Philips patient monitor setup at the neonatal intensive care unit. Two different post-processing modules were used. PTT was defined as the difference between the R-peak in the ECG and the point of 50% increase in the PPG.

Results

A sawtooth artifact was seen in all simulations. Both length (59.2 to 72.4 s) and amplitude (30.8 to 36.0 ms) of the sawtooth were dependent on the post-processing module used. Furthermore, the absolute PTT value differed up to 250 ms depending on post-processing module and heart rate. The sawtooth occurred because the PPG wave continuously showed a minimal prolongation during the length of the sawtooth, followed by a sudden shortening. Both artifacts were generated in the post-processing module containing Masimo algorithms.

Conclusion

Post-processing of the PPG signal in the Masimo module of the Philips patient monitor introduces a sawtooth in PPG and derived PTT. This sawtooth, together with a large module-dependent absolute difference in PTT, renders the thus-derived PTT insufficient for clinical purposes.

Autonomic Arousals as Surrogates for Cortical Arousals Caused by Respiratory Events: A Methodological Optimization Study in the Diagnosis of Sleep Breathing Disorders

INTRODUCTION

Portable monitoring (PM) is an alternative to laboratory polysomnography (PSG) for diagnosing obstructive sleep apnea (OSA). However, PM tends to underestimate the apnea-hypopnea index (AHI), as it does not identify non-desaturating events associated with electroencephalographic (EEG) arousal. The objectives were to explore heart rate acceleration (HRa) and decrease in pulse transit time (PTT) as surrogates to EEG arousal for non-desaturating hypopnea and respiratory effort-related arousal (RERA), and to estimate cut-off values for their use with both total sleep time (TST), the standard method for PSG, and total recording time (TRT), the usual method for PM.

METHODS

Twenty-four consecutive individuals with suspected OSA were studied with PSG. Calculated outcomes were: AHI, respiratory disturbance index with EEG arousal (RDIe) and autonomic arousal by HRa (RDI-HRa) and PTT decreases (RDI-PTT) at different time cut-offs. Using RDIe as reference, Bland Altman and intraclass coefficient of correlation (ICC) were used to calculate agreement between indexes, and receiver operating curves (ROC) for sensitivity/specificity of the different cut-offs.

RESULTS

Autonomic arousals, limited to respiratory events, were present in 36% of non-desaturating hypopneas and 29% of RERAs. Using TST, RDI-HRa of 10 bpm (ICC= 0.89) and RDI-PTT with a decrease of -15 msec (ICC=0.90) agreed better with RDIe. With TRT, the RDI-HRa of 5 bpm agreed better with the RDIe (ICC=0.89). Bland-Altman plots showed mean differences of 1.53 between RDI-HRa10-TST and RDIe and 0.89 between RDI-HRa5-TRT and RDIe.

CONCLUSION

Autonomic arousals (HRa and PTT) may be a suitable proxy of EEG arousals associated with respiratory events, using both TST and TRT. Therefore, they could potentially help to capture borderline symptomatic patients and to monitor treatment outcomes.

Accuracy of portable devices in sleep apnea using oximetry-derived heart rate increases as a surrogate arousal marker

PURPOSE

Type 3 home study (HS) monitors do not detect cortical arousal-related hypopneas and may therefore underestimate the polysomnography (PSG)-based apnea-hypopnea index (AHI). Our aim was to test the hypothesis that scoring hypopneas using heart rate accelerations as a surrogate marker for cortical arousal (autonomic hypopnea; AnH) improves the accuracy of HS for OSA diagnosis, using PSG AHI as the diagnostic gold standard.

METHODS

We retrospectively identified patients referred for OSA who underwent complete PSG following an initial inconclusive HS. Respiratory events were scored using AASM research (Chicago) criteria with additional HS scoring for AnH, defined as hypopneas based on flow criteria associated with an increase in pulse oximetry-derived heart rate ≥ 6 beats/min.

RESULTS

A total of 178 patients met inclusion criteria, with mean (±SD) HS AHI = 4.4 ± 4.2/h, which increased to 8.5 ± 5.3/h with AnH scoring. The hypopnea arousal index on subsequent PSG was 7.6 ± 7.7/h, with total AHI 15.6 ± 11.9/h. Bland-Altman analysis showed improved agreement between HS and PSG AHI (mean difference 11.2/h (95%CI 33.6, - 11.1) without vs. 7.2/h (95%CI 29.6, - 15.4) with AnH scoring). Overall diagnostic accuracy was improved with AnH scoring as reflected by an increased area under the receiver-operating characteristic curve for AHI thresholds of 10 and 15 events/h.

CONCLUSIONS

In this retrospective analysis, the diagnostic accuracy of type 3 HS was improved by the inclusion of hypopnea-associated heart rate increases as a surrogate marker of arousal. Prospective studies are warranted to evaluate the impact of AnH scoring on clinical decision-making and patient outcomes.

"Sleep disordered breathing and ECG R-wave to radial artery pulse delay, The Multi-Ethnic Study of Atherosclerosis"

BACKGROUND

Electrocardiography R-wave to radial artery pulse delay (RRD) represents pulse transit time inclusive of pre-ejection period (PEP) and arterial pulse propagation time. RRD is proposed to largely reflect arterial stiffness when PEP is accounted for (shorter RRD = higher arterial stiffness). Sleep disordered breathing (SDB) causes intermittent hypoxemia and sympathetic activation, which negatively influences vascular function. We aimed to examine the association of measures of SDB with RRD.

METHODS

Our sample consisted of participants in the Multi-Ethnic Study of Atherosclerosis without prevalent cardiovascular disease who underwent a daytime arterial elasticity exam, cardiac magnetic resonance imaging (MRI), and overnight polysomnography. SDB measures of interest included apnea hypopnea index (AHI) and oxygen desaturation index (ODI) (N = 1173). RRD was regressed on each measure of SDB separately, with adjustment for other cardiovascular risk factors as well as for correlates of the PEP, another component of RRD, by including cardiac MRI measures of contractility and preload.

RESULTS

In multivariate analysis, among measures of SDB, ODI, a marker of intermittent hypoxemia, was inversely associated with RRD (β = -60.2 msec per SD [15.5/hr], p = 0.04). No significant association was found with AHI. In gender stratified analyses, ODI and AHI were predictive of RRD in men only (β = -111.3 msec per SD [15.5/hr], p = 0.01 and β = -100.3 msec per SD [16.1/hr], p = 0.02 respectively).

CONCLUSION

Severity of SDB as measured by ODI was associated with RRD, a marker of arterial stiffness. Thus, association of RRD with measures of SDB appears to be gender-dependent.