Pulse Transit Time Improves Detection of Sleep Respiratory Events and Microarousals in Children

doi:10.1378/chest.127.3.722

Chest

Volume 127, Issue 3, March 2005, Pages 722-730

https://doi.org/10.1378/chest.127.3.722 Get rights and content

Objectives

To evaluate the additional information provided by pulse transit time (PTT), a noninvasive tool, when using during polysomnography for the diagnosis of sleep breathing disorders in a pediatric population

Main findings

Respiratory and microarousals events were scored twice. The first scoring was performed using nasal pressure, thermistors, thoracic and abdominal movements, and oxygen saturation. The second scoring, blinded to the first scoring, was performed using PTT in combination with all the other signals. Microarousals were scored once visually on the EEG trace (cortical arousals [CAs]) and once using the PTT signal (autonomic arousals [AAs]) blinded to EEG. For the whole group of 16 children studied (mean age, 9.5 years), there was no significant difference between the respiratory disturbance index (RDI) with or without PTT analysis (22.4 ± 13.5/h vs 20.4 ± 14.3/h; not significant [mean ± SD]). Among the children exhibiting a “without PTT” RDI < 30/h, 5 of 12 children (41.66%) showed a clinically significant ≥ 5/h increase in RDI when using PTT. AAs detected by PTT were significantly more frequent than CAs during rapid eye movement (REM) sleep (7.4 ± 3.9/h vs 3.2 ± 2.3/h; p < 0.001) and slow wave sleep (SWS) [6.0 ± 4.3/h vs 0.6 ± 0.5/h; p < 0.0001]

Conclusions

The quantification of respiratory effort using PTT improves the detection of respiratory events in children. The detection of microarousals is improved particularly in REM and SWS

Section snippets

Patients

Eighteen unselected consecutive children referred for suspected sleep-disordered breathing were prospectively included in the study.

Polysomnography

All children underwent full-night polysomnography. Continuous recordings were taken of EEG with electrode positions C3/A2-C4/A1-Cz/O1 of the international 10–20 electrode placement system, eye movements, chin electromyogram, and ECG with modified V₂ lead. Airflow was measured with NP, associated with the sum of buccal and nasal thermistor signals. Respiration was

Patients

On the 18 children initially included, 2 children were finally not taken into account for data analysis because of technical problems during PTT recordings. Population characteristics and main polysomnographic data are summarized in Table 1. Snoring was a constant symptom. Fifty percent of the children exhibited mouth breathing during wakefulness, 44% had daytime sleepiness, and 6% had enuresis. Six of the 16 children were obese (body mass index above the 18th percentile). None of the children

Optimization of the Detection of Subtle Respiratory Events by the Use of PTT

In adults, NP as a tool for quantifying airflow has demonstrated its ability to markedly increase the detection of nonapneic events compared to thermistors.2, 3 Mouth breathing is a clinical finding reported in up to 90% of children presenting with suspected obstructive sleep apnea.15, 16 Thus, this signal could be less accurate in children with predominant mouth breathing. In the current study, the NP signal was not interpretable for a 20% of the total duration of polysomnographic recordings.

Conclusion

Using PTT with other respiratory signals including NP allowed a better identification of significant respiratory events, particularly in the mild-to-moderate spectrum of the disease. Using PTT also improved the detection of arousals in REM and SWS. These AAs seem to better correlate with the number of respiratory events. Whether this kind of sleep fragmentation is also responsible for specific daytime consequences remain to be demonstrated. PTT signal could also help in identifying and

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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.
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.
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.
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.
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Identifying electroencephalogram (EEG) cortical arousals are crucial in scoring hypopneas and respiratory efforts related arousals (RERAs) during a polysomnogram. As children have high arousal threshold, many of the flow limited breaths or hypopneas may not be associated with visual EEG arousals, hence this may lead to potential underestimation of the degree of sleep disordered breathing. Pulse wave amplitude (PWA) is a signal obtained from finger photoplethysmography which correlates directly to finger blood flow. The drop in PWA has been shown to be a sensitive marker for subcortical/autonomic and cortical arousals. Our aim was to use the drop in PWA as a surrogate for arousals to guide scoring of respiratory events in pediatric patients.
Ten polysomnograms for patients between the ages of 5–15 years who had obstructive apnea-hypopnea indices between 1 and 5 events/hour were identified. Patients with syndromes were excluded. A drop in PWA signal of at least 30% that lasted for 3 s was needed to identify subcortical/autonomic arousals. Arousals were rescored based on this criteria and subsequently respiratory events were rescored. Paired t-tests were employed to compare PSG indices scored with or without PWA incorporation.
The sample of 10 children included 2 females, and the average age was 9.8 ± 3.1 years. Overall, polysomnography revealed an average total sleep time of 464.1 ± 25 min, sleep efficiency of 92% +/−4.2, sleep latency of 19.6 ± 17.0 min, rapid eye movement (REM) latency 143 ± 66 min, N1 3.9% +/−2.0, N2 50.3% +/−12.0, N3 28.2% +/−9.1, REM 16.7% +/−4.0, and wakefulness after sleep onset (WASO) 18.1 ± 7.5 min. Including arousals from PWA changes, respiratory indices significantly increased including total AHI (2.3 ± 0.7 vs 5.7 ± 2.1, p < 0.001), obstructive AHI (1.45 ± 0.7 vs 4.8 ± 1.8, p < 0.001), and RDI (2.36 ± 0.7 vs 7.6 ± 2.0, p < 0.001). Likewise, total arousal index was significantly higher (8.7 ± 2.3 vs 29.4 ± 6.5, p < 0.001).
The drop in pulse wave amplitude signal is a useful marker to guide scoring arousals that are not otherwise easily identified in pediatric polysomnography and subsequently helped in scoring respiratory events that otherwise would not be scored. Further studies are needed to delineate if such methodology would affect clinical outcome.
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: Clinical research funding was provided by PHRC 1997, Ministeère de la recherche (249/97)

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Chest

Clinical Investigations: Sleep and BreathingPulse Transit Time Improves Detection of Sleep Respiratory Events and Microarousals in Children

Objectives

Main findings

Conclusions

Section snippets

Patients

Polysomnography

Patients

Optimization of the Detection of Subtle Respiratory Events by the Use of PTT

Conclusion

Respir Physiol

Clin Neurophysiol

Chest

Clin Neurophysiol

Nasal prongs in the detection of sleep-related disordered breathing in the sleep apnoea/hypopnoea syndrome

Eur Respir J

Detection of flow limitation with a nasal cannula/pressure transducer system

Am J Respir Crit Care Med

Assessment of inspiratory flow limitation in children with sleep-disordered breathing by a nasal cannula pressure transducer system

Pediatr Pulmonol

Use of nasal cannula for detecting sleep apneas and hypopneas in infants and children

Am J Respir Crit Care Med

Comparison of esophageal pressure with pulse transit time as a measure of respiratory effort for scoring obstructive nonapneic respiratory events

Am J Respir Care Med

Pulse transit time as a measure of arousal and respiratory effort in children with sleep-disordered breathing

Pediatr Res

EEG arousals: scoring rules and examples

Sleep

Arousal pattern following central and obstructive breathing abnormalities in infants and children

J Appl Physiol

Standards and indications for cardiorespiratory sleep studies in children

Am J Respir Crit Care Med

Pulse transit time: an appraisal of potential clinical applications

Thorax

Autonomic markers of arousal during sleep in patients undergoing investigation for obstructive sleep apnoea, their relationship to EEG arousal, respiratory events and subjective sleepiness

J Sleep Res

Clinical Investigations: Sleep and Breathing
Pulse Transit Time Improves Detection of Sleep Respiratory Events and Microarousals in Children