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

Respiratory event index underestimates severity of sleep apnea compared to apnea-hypopnea index

Polygraphy (PG) is often used to diagnose obstructive sleep apnea (OSA). However, it does not use electroencephalography, and therefore cannot estimate sleep time or score arousals and related hypopneas. Consequently, the PG-derived respiratory event index (REI) differs from the polysomnography (PSG)-derived apnea-hypopnea index (AHI). In this study, we comprehensively analyzed the differences between AHI and REI. Conventional AHI and REI were calculated based on total sleep time (TST) and total analyzed time (TAT), respectively, from two different PSG datasets (n = 1561). Moreover, TAT-based AHI (AHITAT) and TST-based REI (REITST) were calculated. These indices were compared keeping AHI as the gold standard. The REI, AHITAT, and REITST were significantly lower than AHI (p < 0.0001, p ≤ 0.002, and p ≤ 0.01, respectively). The total classification accuracy of OSA severity based on REI was 42.1% and 72.8% for two datasets. Based on AHITAT, the accuracies were 68.4% and 85.9%, and based on REITST, they were 65.9% and 88.5% compared to AHI. AHI was most correlated with REITST (r = 0.98 and r = 0.99 for the datasets) and least with REI (r = 0.92 and r = 0.97). Compared to AHI, REI had the largest mean absolute errors (13.9 and 6.7) and REITST the lowest (5.9 and 1.9). REI had the lowest sensitivities (42.1% and 72.8%) and specificities (80.7% and 90.9%) in both datasets. Based on these present results, REI underestimates AHI. Furthermore, these results indicate that arousal-related hypopneas are an important measure for accurately classifying OSA severity.

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.

Comparing respiratory polygraphy with pulse transit time analysis versus overnight polysomnography in the diagnosis of obstructive sleep apnoea in children

OBJECTIVE

Obstructive sleep apnea syndrome in children is associated with significant morbidity. Polysomnography is the main diagnostic tool but is time consuming and requires skilled manpower to supervise the patient overnight and hence long referral to diagnosis time. However, there are limitations and underestimation of the apnoea hyponea index (AHI) with alternative home sleep apnoea testing (HSAT), such as type 3 respiratory polygraphy (RP). Prior studies have demonstrated pulse transit time (PTT) to be a reliable indicator of cortical arousals. In this study, the use of PTT together with RP will be studied to determine whether the derived AHI is comparable to that of PSG.

METHOD

Forty-five patients with suspected OSA met the inclusion criteria underwent PSG in the sleep laboratory for analysis. The raw data for either PSG or RP analysis were allocated separately to two different accredited sleep technicians. The primary outcome AHI derived from PTT with RP was compared to the AHI derived from PSG. Secondary outcomes compared were obstructive apnoea index (OAI), total hypopnoea index (THI) and arousal index (AI). Bland Altman analysis was used to compare the agreement of AHI derived from the 2 modalities and demonstrate whether RP is non inferior or equivalent to the gold standard for diagnosing OSAS.

RESULTS

The patients studied had a median age of 8.8 years (range 3-17 years). The patients were not limited to certain spectrum of severity OSA and had AHI results spread from mild to severe OSA (AHI 0.4/hr to 72.2/hr). The RP with PTT-derived AHI was strongly correlated to the PSG derived AHI as seen on the Spearman plot (r = 0.98). The Bland Altman plot showed no evidence of underestimation of the AHI due to missed arousal related hypopneas. The difference of AHI derived from RP and PSG results were clinically insignificant. The differences between the PSG and RP total hypopnoea index (THI) and arousal index (AI) were also statistically insignificant.

CONCLUSION

The study shows that RP with PTT can be considered a reliable diagnostic alternative compared with PSG. The role of PTT incorporated with RP was to minimize underestimation of AHI due to missed arousal associated hypopnea events. The results were apparent across mild to severe severity of OSA. There are advantages of RPs particularly in paediatrics. Overall this study offers promising preliminary insights that RP incorporated with PTT can be further explored as an acceptable home diagnostic tool for diagnosing OSA in children.

Multitargeting the sleep-pain interaction with pharmacological approaches: A narrative review with suggestions on new avenues of investigation

The multimorbidity formed by sleep disturbances and pain conditions is highly prevalent and has a significant impact in global health and in the socioeconomic system. Although different approaches have been directed toward its management, evidence regarding an optimal treatment is lacking, and pharmacological options are often preferred. Health professionals (e.g., pain and sleep clinicians) tend to focus on their respective expertise, targeting a single symptom with a single drug. This may increase polypharmacy and the risk of drug interactions, adverse events, and mortality. Hence, the use of medications that can directly or indirectly improve sleep, pain, and other possible accompanying conditions without exacerbating them becomes especially relevant. The objectives of this comprehensive review are to: a) describe the beneficial or deleterious effects that some commonly used medications to manage pain have on sleep and sleep disorders; and b) describe the beneficial or deleterious effects that frequently prescribed medications for sleep may have on pain. Moreover, medications targeting some specific sleep-pain interactions will be suggested and future directions for improving sleep and alleviating pain of these patients will be provided with clinical and research perspectives.

The Evaluation of Autonomic Arousals in Scoring Sleep Respiratory Disturbances with Polysomnography and Portable Monitor Devices: A Proof of Concept Study

BACKGROUND

Autonomic arousals can be considered as surrogates of electroencephalography (EEG) arousals when calculating respiratory disturbance index (RDI). The main objective of this proof of concept study was to evaluate the use of heart rate acceleration (HRa) arousals associated with sleep respiratory events in a population undergoing full polysomnography (type 1) and in another undergoing portable monitor study (type 3). Our hypothesis is that when compared to other commonly used indexes, RDI based on HRa will capture more events in both types of recording.

MATERIALS AND METHODS

A retrospective analysis was performed in two different populations of patients with suspected OSA: a) 72 patients undergoing one night of type 1 recording and b) 79 patients undergoing one night of type 3 recording. Variables for type 1 were 4% oxygen desaturation index (ODI), apnea/hypopnea index (AHI), RDI based on EEG arousals (RDIe), and RDI based on HRa with threshold of 5bpm (RDIa5). For type 3, variables were 4% ODI, AHI, and RDIa5 (it is not possible to calculate RDIe due to the absence of EEG). Calculated data were 1) Mean values for each sleep disturbance index in type 1 and 3 recordings; 2) Frequency of migration from lower to higher OSA severity categories using RDIa5 in comparison to AHI (thresholds: ≥5/h mild, ≥15/h moderate, ≥30/h severe); and 3) Bland-Altman plots to assess agreement between AHI vs RDIe and RDIa5 in type 1 population, and AHI vs RDIa5 in type 3 populations.

RESULTS

More respiratory disturbance events were captured with RDIa5 index in both type 1 and type 3 recordings when compared to the other indexes. In type 1 recording, when using RDIa5 37% of patients classified as not having OSA with AHI were now identified as having OSA, and a total of 59% migrated to higher severity categories. In type 3 recording, similar results were obtained, as 37% of patients classified as not having OSA with AHI were now identified as having OSA using RDIa5, and a total of 55% patients migrated to higher severity categories. Mean differences for RDIa5 and AHI in type 1 and 3 populations were similar.

CONCLUSION

The use of autonomic arousals such as HRa can help to detect more respiratory disturbance events when compared to other indexes, being a variable that may help to capture borderline mild cases. This becomes especially relevant in type 3 recordings. Future research is needed to determine its validity, optimization, and its clinical significance.