Characteristics Of Respiratory Events Research Articles

Automatic identification of respiratory events based on nasal airflow and respiratory effort of the chest and abdomen

Objective. Disease may cause changes in an individual’s respiratory pattern, which can be measured as parameters for disease evaluation, usually through manually annotated polysomnographic recordings. In this study, a machine learning model based on nasal airflow and respiratory effort of the chest and abdomen is proposed to automatically identify respiratory events, including normal breathing, hypopnea and apnea. Approach. The nasal airflow and chest–abdominal respiratory effort signals were collected by polysomnography (PSG). Time/frequency domain features, fractional Fourier transform features and sample entropy were calculated to obtain feature sets. Features selected through statistical analysis were used as input variables of the machine learning model. The performance of different input combinations on different models was studied and cross-validated. Main results. The dataset included PSG sleep records of 60 patients provided by the Chinese People’s Liberation Army General Hospital. The extreme gradient boosting-based model (XGBoost) performed best in several models with an accuracy of 0.807 and a F1 score of 0.807, depending on the combination of nasal airflow and two respiratory effort signals. The precision for normal breathing, hypopnea and apnea events were 0.764, 0.789 and 0.871, respectively. In addition, the recall scores were 0.833, 0.768 and 0.823 for normal breathing, hypopnea and apnea events, respectively. Moreover, it was found that the standard deviation and kurtosis of nasal airflow were the most important features of the respiratory event detection model. Significance. Since nasal airflow and respiratory effort of the chest and abdomen contain the characteristics of respiratory events, their combined use can improve the classification performance for identification of respiratory events. With this method, respiratory events can be automatically detected and labeled from the PSG records, which can be used to screen for patients with sleep apnea–hypopnea syndrome.

Longer apneas and hypopneas are associated with greater ultra-short-term HRV in obstructive sleep apnea

Low long-term heart rate variability (HRV), often observed in obstructive sleep apnea (OSA) patients, is a known risk factor for cardiovascular diseases. However, it is unclear how the type or duration of individual respiratory events modulate ultra-short-term HRV and beat-to-beat intervals (RR intervals). We aimed to examine the sex-specific changes in RR interval and ultra-short-term HRV during and after apneas and hypopneas of various durations. Electrocardiography signals, recorded as a part of clinical polysomnography, of 758 patients (396 men) with suspected OSA were analysed retrospectively. Average RR intervals and time-domain HRV parameters were determined during the respiratory event and the 15-s period immediately after the event. Parameters were analysed in three pooled sex-specific subgroups based on the respiratory event duration (10–20 s, 20–30 s, and > 30 s) separately for apneas and hypopneas. We observed that RR intervals shortened after the respiratory events and the magnitude of these changes increased in both sexes as the respiratory event duration increased. Furthermore, ultra-short-term HRV generally increased as the respiratory event duration increased. Apneas caused higher ultra-short-term HRV and a stronger decrease in RR interval compared to hypopneas. In conclusion, the respiratory event type and duration modulate ultra-short-term HRV and RR intervals. Considering HRV and the respiratory event characteristics in the diagnosis of OSA could be useful when assessing the cardiac consequences of OSA in a more detailed manner.

Polysomnographic characteristics of severe obstructive sleep apnea vary significantly between hypertensive and normotensive patients of both genders

PurposeHypertension is a common finding in patients with obstructive sleep apnea (OSA), but it has remained unclear whether or not the amount of disturbed breathing and characteristics of individual respiratory events differ between hypertensive and normotensive patients with severe OSA.MethodsFull polysomnographic recordings of 323 men and 89 women with severe OSA were analyzed. Differences in the duration of individual respiratory events, total apnea and hypopnea times, and the percentage of disturbed breathing from total sleep time (AHT%) were compared between normotensive and hypertensive patients separately by genders. Furthermore, differences in the respiratory event characteristics were assessed between three AHT% groups (AHT% ≤ 30%, 30% < AHT% ≤ 45%, and AHT% > 45%).ResultsHypertensive women had lower percentage apnea time (15.2% vs. 18.2%, p = 0.003) and AHT% (33.5% vs. 36.5%, p = 0.021) when compared with normotensive women. However, these differences were not observed between hypertensive and normotensive men. Percentage hypopnea time was higher in hypertensive men (13.5% vs. 11.2%, p = 0.043) but not in women (15.2% vs. 12.2%, p = 0.130) compared with their normotensive counterparts. The variation in AHI explained 60.5% (ρ = 0.778) and 65.0% (ρ = 0.806) of the variation in AHT% in normotensive and hypertensive patients, respectively. However, when AHT% increased, the capability of AHI to explain the variation in AHT% declined.ConclusionsThere is a major inter- and intra-gender variation in percentage apnea and hypopnea times between hypertensive and normotensive patients with severe OSA. OSA is an important risk factor for hypertension and thus, early detection and phenotyping of OSA would allow timely treatment of patients with the highest risk of hypertension.

Acute stroke and TIA patients have specific polygraphic features of obstructive sleep apnea

PurposeObstructive sleep apnea (OSA) is associated with increased risk for stroke, which is known to further impair respiratory functions. However, it is unknown whether the type and severity of respiratory events are linked to stroke or transient ischemic attack (TIA). Thus, we investigate whether the characteristics of individual respiratory events differ between patients experiencing TIA or acute ischemic stroke and matched patients with clinically suspected sleep-disordered breathing.MethodsPolygraphic data of 77 in-patients with acute ischemic stroke (n = 49) or TIA (n = 28) were compared to age, gender, and BMI-matched patients with suspected sleep-disordered breathing and no cerebrovascular disease. Along with conventional diagnostic parameters (e.g., apnea-hypopnea index), durations and severities of individual apneas, hypopneas and desaturations were compared between the groups separately for ischemic stroke and TIA patients.ResultsStroke and TIA patients had significantly shorter apneas and hypopneas (p < 0.001) compared to matched reference patients. Furthermore, stroke patients had more central apnea events (p = 0.007) and a trend for higher apnea/hypopnea number ratios (p = 0.091). The prevalence of OSA (apnea-hypopnea index ≥ 5) was 90% in acute stroke patients and 79% in transient ischemic attack patients.ConclusionStroke patients had different characteristics of respiratory events, i.e., their polygraphic phenotype of OSA differs compared to matched reference patients. The observed differences in polygraphic features might indicate that stroke and TIA patients suffer from OSA phenotype recently associated with increased cardiovascular mortality. Therefore, optimal diagnostics and treatment require routine OSA screening in patients with acute cerebrovascular disease, even without previous suspicion of OSA.

Analysis of polysomnography results between pre- and post-operation in pediatric obstructive sleep apnea hypopnea syndrome patients

Objective: To determine the objective effects of adenotonsillectomy on pediatric obstructive sleep apnea hypopnea syndrome (OSAHS) through analyzing the polysomnography (PSG) results between pre and post-operation. Methods: A total of 56 pediatric OSAHS patients were included who underwent adenoidectomy or/and tonsillectomy and completed PSG follow-up from January 1, 2017 to March 31, 2018. All the pediatric patients who underwent adenoidectomy or/and tonsillectomy during the research period were arranged to take a preoperative PSG study. Patients who were diagnosed OSAHS would be encouraged to complete a follow-up PSG study ranged from1 to 3 months after surgery. The parameters of respiration and sleep architecture of PSG were compared and analyzed. The paired student t test was used to compare preoperative and postoperative mean values. The unpaired student t test was used to compare quantitative variables among different groups. The rank sum test was used if the data were abnormal distribution. Results: Totally 238 patients completed preoperative PSG study, 62 patients were diagnosed as pediatric OSAHS, 56 eligible patients finished post-operative PSG. Hypopnea was the majority in all type of respiratory events in 56.45% (35/62) subjects, while central apnea as the majority in 29.03% (18/62) subjects who can also get significant CAI decrease after surgery. However, obstructive apnea as the majority only exist in 14.52% (9/62) subjects. The short-term cure rate of pediatric OSAHS was 85.71% (48/56). The postoperative AHI, MAI, CAI, HI, ODI, LoSpO(2), percentage of stage I sleep and arousal index were significantly decreased, however, the OAI was no statistical decrease. The percentage of stage Ⅱ and rapid eye movement (REM) sleep were significantly increased, while no significant change in percentage of slow wave sleep and sleep efficiency(t=2.32, P=0.017). Conclusions: Pediatric OSAHS manifest different characteristics of respiratory events from that of adults. Adenotonsillectomy can significant decrease respiratory events and improve sleep architecture, however, there are still some patients who can't be completely relieved with adenotonsillectomy.

Obstructive sleep apnea phenotypes in men based on characteristics of respiratory events during polysomnography.

The upper airway (UA) anatomical collapsibility, UA muscle responsiveness, breathing control, and/or arousability are important contributing factors for obstructive sleep apnea (OSA). Differences in clinical manifestations of OSA are believed to reflect interactions among these factors. We aimed to classify OSA patients into subgroups based on polysomnographic (PSG) variables using cluster analysis and assess each subgroup's characteristics. Men with moderate or severe OSA and without any concomitant heart or psychosomatic disease were recruited. A hierarchical cluster analysis was performed using variables including fraction of apnea, respiratory event duration, minimum oxygen saturation, arousal rate before termination, and frequency of respiratory events in the supine position. The impact of sleep stages or body position on PSG variables was also evaluated in each cluster. A total of 210 men (mean age, 50.0years, mean body mass index, 27.4kg/m2) were studied. The three subgroups that emerged from the analysis were defined as follows: cluster 1 (high fraction of apnea and severe desaturation (20%)), cluster 2 (high fraction of apnea and long event duration (31%)), and cluster 3 (low fraction of apnea (49%)). There were differences in the body mass index and apnea type between the three clusters. Sleep stages and/or body position affected PSG variables in each cluster. Patients with OSA could be divided into three distinct subgroups based on PSG variables. This clustering may be used for assessing the pathophysiology of OSA to tailor individual treatment other than continuous positive airway pressure therapy.

Novel parameters reflect changes in morphology of respiratory events during weight loss

Apnea–hypopnea-index (AHI), disregarding the respiratory event morphology, is currently used in estimation of severity of obstructive sleep apnea (OSA). The purpose of the current study was to evaluate the potential of novel parameters in estimation of changes in severity of OSA during weight loss. Polygraphic data of 67 patients, 37 in the control (no weight loss) and 30 in the weight loss (>5%) groups was evaluated at baseline and after two year follow-up. Changes in the values of novel parameters, incorporating detailed information of respiratory event characteristics, were evaluated and compared with changes in AHI. The median AHI in the weight loss group decreased significantly during the follow-up. The number of shorter respiratory events decreased in the weight loss group, while the longer ones remained, increasing the median durations of the respiratory events by 20–62%. For this reason the decrease of the values of the novel parameters were smaller compared to AHI in the weight loss group. This suggests that the severity of OSA might not fall as linearly during weight loss as AHI suggests. Moreover, the novel parameters containing more detailed information on the morphology characteristics may provide valuable supplementary information for the assessment of the severity of OSA.

Respiratory events in preterm infants prior to discharge: with and without clinically concerning apnoea

This study aimed to determine the characteristics of respiratory events in preterm infants with clinically concerning apnoea at or beyond 35 weeks postmenstrual age and to compare these findings with a group of preterm infants ready for discharge, without clinically concerning apnoea. Infants born at <32 weeks of gestation and who underwent nap polysomnography at or beyond 35 weeks corrected age prior to discharge were included. Cases were preterm infants with clinically concerning apnoea, and control infants were preterm infants asymptomatic for apnoea. Infants with upper airway obstruction, congenital malformations or apnoea associated with sepsis were excluded. Studies were retrospectively reviewed for length, type and frequency of apnoea. The relationship between sleep state and changes in oxygen saturation was compared between groups. Peri-natal and demographic data were also compared. Data were complete for 16 case and 18 control infants. Gestational age was similar at birth and at time of study, but cases had a lower birth weight (p = 0.04) and higher weight at study (p = 0.04). There were no group differences in the mean duration, type or numbers of apnoea. The duration of the longest apnoea was greater in case infants (17.4 s vs. 12.3 s, p = 0.02). Lowest oxygen saturation (p < 0.05) and average minimum oxygen saturation (p < 0.05) were lower in case infants. Preterm infants with clinically concerning apnoea have similar amounts and types of apnoea but lower oxygen saturation after apnoea compared with controls. The use of oxygen saturation monitoring is more useful than respiratory monitoring alone in recognising these events.

Use of the pulse transit time trend to relate tidal breathing and central respiratory events

Central sleep apnoea (CSA) is a respiratory event where cessation of breathing effort and airflow occurs. Numerous lumped models have related the physical phenomena in the arterial tree to properties of the arterial wall. However, a limited model is available that describes pulse transit time (PTT) oscillations during CSA and tidal breathing. Data from 28 children (22 males; aged 6.2 +/- 3.6 years) were obtained during overnight polysomnography. Using a lumped-element model, PTT fluctuations during both respiratory events were described and compared with actual experimental data. 222 valid CSA and 222 tidal breathing events were acquired and analysed. For the tidal breathing, undamped PTT oscillations of 3.89 s were predicted while actual data showed a mean value of 3.68 +/- 0.83 s. Conversely, a damped PTT trend was observed during CSA as predicted by the model. The results attained showed that clustered CSA occurrences led to an increase of 7.23 +/- 3.34 per cent in PTT baseline value while the model predicted 7.86 +/- 2.63 per cent. The marginal increase in PTT baseline was expected since the blood pressure and heart rate decreased during such occurrences. The findings herein suggest that the described model has the potential to describe respiratory event characteristics of a sleeping child.