Evaluating oronasal flow with temperature (thermistor) and obstructive pressure (prongs)

The measurement of oronasal flow during sleep studies using thermistors is internationally well accepted. As an alternative the possibility exists to measure the pressure at the nose by means of nasal prongs. Our objective was to compare and evaluate the methods to detect respiratory events in clinical routine, namely O2-saturation by pulse oxymetry oronasal flow by thermistors thoraco-abdominal effort by belts oronasal flow by prongs, 8 consecutive patients suspected of sleep apnoea syndrome (7 m, 1 f), mean age 56.5 +/- 9.5 years, height 173 +/- 6.4 cm, BMI 28.7 +/- 2.6 kg/m2, Epworth sleepiness scale score 9.1 +/- 3.2, AHI 24.9 +/- 13.7 h-1, lowest SaO2 86 +/- 4.9%, were examined. Between nose and mouth we fixed an oronasal 3-point thermistor and oronasal prongs (2 openings at the mouth and 2 openings at the mouth applying a common tube). During breathing the resulting pressure was registered with a pressure transducer parallel to the signal of the thermistors and the other polysomnographic data. We defined a respiratory event if at least one of the 4 signals met the criteria of a respiratory disturbance (for exact definitions see method). The detection rate of the 4 signals was calculated in relation to the sum of all events. Of the 1824 events (100%) only 52.3% were detected by an O2-desaturation of more than 4%, but 61.0% by thermistors. An acceptable detection rate was found measuring effort with 83.4%, only nasal prongs detected 95.1% of all events. We conclude that with regard to the detection rate of respiratory events the measurement of pressure by nasal prongs is superior to the use of thermistors.     

慢性阻塞性肺疾病患者睡眠呼吸紊乱类型及其与呼吸中枢反应性的关系

目的分析重叠综合征[慢性阻塞性肺疾病（COPD）合并睡眠呼吸暂停低通气综合征（SAHS）]患者睡眠呼吸紊乱的特点，并探讨其与呼吸中枢反应性的关系。方法对300例稳定期COPD患者经问卷、Epworth嗜睡量表及家庭血氧饱和度监测，对氧减饱和指数〉5次／h或嗜睡评分≥10分的患者进行多导生理记录仪睡眠呼吸监测，其中呼吸暂停低通气指数（AHI）≥10次／h的患者有79例（重叠综合征组）。选择年龄、性别及体重指数与其相匹配的118例单纯SAHS患者（SAHS组），对比分析其睡眠呼吸紊乱的特点。另外测定重叠综合征组22例患者的呼吸中枢高CO2反应性和低氧反应性，并与300例COPD患者中17例和SAILS组中17例的相应检测结果进行比较。结果40％（32／79）的重叠综合征患者在睡眠过程中出现延续时间〉1min的持续肺泡通气不足，但单纯SAHS患者此种现象很少见。重叠综合征组的低通气指数占AHI百分比[（69±30）％]、总低通气时间占总睡眠时间百分比[（15±12）％]均较单纯SAHS组[（52±31）％、（12±10）％]明显增高。重叠综合征患者在清醒状态下的△呼气流量／△动脉血氧饱和度[（-0．11±0．05）L·min^-1·％^-1]和△呼气流量／△动脉血二氧化碳分压[（1．1±0．8）L·min^-1·mmHg^-1（1mmHg=0．133kPa）]均明显低于单纯SAHS患者[（-0．35±0．24）L·min^-1·％^-1和（1．6±0．8）L·min^-1·mmHg^-1]。结论重叠综合征患者的睡眠呼吸紊乱模式以低通气为主，其清醒时呼吸中枢的低氧反应性降低。     

Comparison of nasal prong pressure and thermistor measurements for detecting respiratory events during sleep

INTRODUCTION AND OBJECTIVES: Thermistor (TH) measurements have been traditionally used to determine airflow during polysomnographic studies (PSG). However, low accuracy in detecting hypopneas is a major drawback. Nasal prong pressure (NPP) measurements are becoming increasingly popular for quantifying respiratory events during sleep. We prospectively compared NPP and TH measurements with respect to their ability to detect respiratory events during routine PSG. METHODS: Forty consecutive patients (26 male, 14 female) with clinically suspected sleep-disordered breathing (SDB) underwent routine diagnostic PSG. Airflow was measured using NPP and TH devices simultaneously. PSG was scored manually according to R and K criteria. Respiratory events were scored in two passes. During the first pass, the TH signal was disabled and the NPP signal was scored. During the second pass, the NPP signal was disabled and the TH signal was scored. Scorers for one method were blinded from the results of the other method. To assess respiratory events, we used the respiratory arousal index (RAI), which was defined as the number of apneas and/or hypopneas followed by an arousal per hour of sleep, as detected by TH (RAI-TH) or NPP (RAI- NPP). Agreement analysis of the results obtained using the two different techniques was performed using the methodology of Bland-Altman. RESULTS: Twenty-six patients had obstructive sleep apnea, 10 had respiratory effort-related arousals and 4 had habitual snoring. The failure time of the flow signal on the raw data was not different between the two methods (NPP: 6 +/- 13 min, TH: 4 +/- 7 min). The Bland-Altman analysis of RAIs demonstrated that more events were nearly always detected using NPP compared to TH devices (44.4 +/- 37 vs. 35.4 +/- 31, p < 0.001). No difference in the index of central apneas between the two methods could be detected. Sleep position had no effect on either measurement method. CONCLUSIONS: NPP measurements are superior to TH measurements for detecting obstructive respiratory events during sleep. Measurement of NPP is a simple, practical, sensitive and reliable method for detecting the whole spectrum of SDB. We recommend incorporating nasal prongs in routine polysomnographic monitoring.     

Description and validation of the apnea risk evaluation system: a novel method to diagnose sleep apnea-hypopnea in the home

STUDY OBJECTIVES: To evaluate the accuracy and practicality of the Apnea Risk Evaluation System (ARES; Advanced Brain Monitoring; Carlsbad, CA), a limited-channel system for diagnosing sleep apnea/hypopnea in the home. DESIGN: Prospective randomized study with blinded analysis. SETTINGS: Two independent, community-based, sleep-disorders centers and the participants' homes. PARTICIPANTS: Two hundred ninety-nine subjects were recruited, including 210 consecutive willing patients referred by community physicians to the centers because of suspected sleep apnea; 36 "general medical" patients recruited from community physicians' offices; and 53 "presumably healthy" subjects recruited from community centers. MEASUREMENTS AND RESULTS: Manual scoring of attended in-laboratory full-night or split-night polysomnography by trained technologists supervised by physicians board certified in sleep medicine, and automated scoring of the limited-channel system used attended in the laboratory and unattended at home. The definition of the polysomnography apnea-hypopnea index (AHI) and the ARES respiratory disturbance index was the total number of events divided by the study duration in hours. Two hundred eighty-four valid comparisons of in-laboratory simultaneous polysomnography and ARES and 187 valid comparisons of in-laboratory polysomnography with a separate 2 nights of unattended self-applied ARES Unicorder (Advanced Brain Monitoring) were obtained. A diagnostic AHI cutoff of > 10 was used to establish the accuracy and validity of the ARES. The concurrent in-laboratory comparison yielded a sensitivity of 97.4, a specificity of 85.6, a positive predictive value of 93.6, and a negative predictive value of 93.9; in-home comparison sensitivity, specificity, positive predictive value, and negative predictive value were 91.5, 85.7, 91.5, and 85.7, respectively. CONCLUSIONS: The ARES demonstrated consistently high sensitivity and specificity for both in-laboratory and in-home recordings. In patients at risk for sleep apnea who do not a priori need an attended study, the ARES could provide a low-cost alternative to traditional polysomnography.     

睡眠诱导的呼吸不稳定性与呼吸暂停

睡眠呼吸暂停低通气综合征（SAHS）以夜间睡眠时反复发生呼吸暂停和低通气为特点。本文通过描述在睡眠期间，由于呼吸调控减弱而诱导出的各种病态和不稳定呼吸的机制和类型，提示了睡眠期易于发生呼吸暂停和低通气的相关机制，以促进对SAHS的认识和治疗。     

Validation of nasal pressure for the identification of apneas/hypopneas during sleep

The reference standard for identifying apneas and hypopneas is a pneumotachograph, but using this can disrupt sleep. Nasal airflow estimation by measuring nasal pressure via nasal prongs is better tolerated by patients. However, nasal pressure has not been validated, using an event-by-event analysis, for detecting apneas/hypopneas during sleep. Eleven patients undergoing polysomnography wore a nasal mask capable of measuring nasal airflow (via pneumotachograph) and nasal pressure simultaneously. Each study was screened for respiratory disturbances, and from these 550 were randomly selected and blindly scored as an apnea/hypopnea or no event each using the pneumotachograph, nasal pressure, square root nasal pressure, and respiratory inductance sum signals independently. Agreement was measured using Cohen's kappa statistic. Intermeasurement agreements between the pneumotachograph and nasal pressure, square root nasal pressure, and respiratory inductance plethysmography sum were 0.76, 0.73, and 0.50, respectively. Inter- and intrarater agreements were, respectively, 0.68 and 0.60 for the pneumotachograph, 0.66 and 0.82 for nasal pressure, 0.61 and 0.78 for square root nasal pressure, and 0.47 and 0.76 for respiratory inductance plethysmography sum. These results indicate that nasal pressure has excellent agreement compared with a pneumotachograph and very good inter-/intrarater agreement. Square root transformation of the nasal pressure signal does not improve these levels of agreement, indicating that it is unnecessary in routine clinical practice for scoring apneas/hypopneas.     

Evaluation of a portable device based on peripheral arterial tone for unattended home sleep studies

BACKGROUND: Diagnosis of obstructive sleep apnea syndrome (OSAS) by ambulatory systems is a growing practice in view of the large number of patients awaiting correct diagnosis. The Watch PAT100 (WP100) [Itamar Medical; Caesarea, Israel] is a portable device based on the peripheral arterial tone (PAT) signal, and is designed for unattended home sleep studies. OBJECTIVES: To evaluate the efficacy, reliability, and reproducibility of the WP100 device for the diagnosis of OSAS as compared to in-laboratory, standard polysomnographic-based manual scoring. Design and methods: One hundred two subjects (78 men; 69 patients with OSAS and 33 normal volunteers; mean +/- SD age, 41.4 +/- 15.2 years; body mass index, 26.8 +/- 5.5) underwent in-laboratory full polysomnography simultaneously with WP100 recording. Fourteen subjects also underwent two additional unattended home sleep studies with the WP100 alone. The polysomnography recordings were blindly scored for apnea/hypopnea according to the American Academy of Sleep Medicine criteria (1999), and the polysomnography respiratory disturbance index (RDI) [PSG-RDI] was calculated. The WP100 data were analyzed automatically for the PAT RDI (PRDI) by a proprietary algorithm that was previously developed on an independent group of subjects. RESULTS: Across a wide range of RDI levels, the PRDI was highly correlated with the PSG-RDI (r = 0.88, p < 0.0001), with an area under the receiver operating characteristic curve of 0.82 and 0.87 for thresholds of 10 events per hour and 20 events per hour, respectively. The PRDI scores were also highly reproducible, showing high correlation between home and in-laboratory sleep studies (r = 0.89, p < 0.001). CONCLUSION: The WP100 may offer an accurate, robust, and reliable ambulatory method for the detection of OSAS, with minimal patient discomfort.     

The impact of obesity on oxygen desaturation in patients with sleep apnea/hypopnea syndrome]

We performed a cross-sectional investigation on the impact of obesity on clinical manifestations in patients with obstructive sleep apnea/hypopnea syndrome (SAHS). The subjects were 87 patients who underwent overnight polysomnography with an apnea/hypopnea index (AHI) of 15/h or more. We divided these patients into non-obese (N) and obese (O) groups based on the median value of the body mass index (BMI), 27 kg/m2. Subjective symptoms, sleep quality and AHI were similar in both groups, but every parameter related to oxygen desaturation was worse in group O than in group N. There was no difference in the mean duration of apnea events between the two groups. The rate of fall in oxygen saturation during apnea events was highly correlated to the BMI (r = 0.72; p < 0.00001). Accordingly, we concluded that profound desaturation in group O is due to a rapid fall in oxygen saturation during apnea events compared with group N. Anthropometric measurements revealed that the rate of fall in oxygen saturation was more related to abdominal circumference (AC) than the neck circumference (NC), which is contrasted with the finding that AHI was more related to NC than AC. This fact suggests that abdominal obesity may deteriorate oxygenation during apnea events and may therefore aggravate the risk of cardiovascular disease in patients with SAHS.     

椎基底动脉供血不足支架植入对改善睡眠呼吸暂停低通气综合征的初步观察

目的 观察椎基底动脉缺血发作与睡眠呼吸暂停低通气综合征(SAHS)之间的关系,以及椎动脉内支架植入治疗对SAHS的作用.方法 对20例椎动脉血管内支架成形术患者在治疗前后进行多导睡眠图监测,同时记录患者的一般资料和临床表现,填写Epworth嗜睡程度量表.按照成人SAHS的诊断标准进行诊断、分型,判断其严重程度及缺氧变化.治疗前后的比较采用配对t检验和秩和检验,偏态分布的计量资料以中位数和四分位间距表示.结果 20例椎基底动脉缺血性狭窄患者合并SAHS者17例,其中轻度10例、中度3例、重度4例,临床类型符合阻塞性睡眠呼吸暂停低通气综合征(OSAHS).治疗后患者的呼吸暂停低通气指数[5.0(1.6～12.7)次/h]、最长呼吸暂停时间[(19.5±12.4)s]、呼吸暂停低通气时间占总睡眠时间百分比[2.3(0.6～9.8)%]、每小时动脉血氧饱和度下降4%的次数[5.8(2.7～17.0)次/h]明显低于治疗前[11.3(6.3～23.6)次/h、(31.5±18.6)s、6.9(2.6～14.3)%、10.1(5.3～29.0)次/h],治疗后患者的夜间最低动脉血氧饱和度[(86.1±3.3)%]明显高于治疗前[(83.6±7.1)%].结论 椎基底动脉缺血患者的睡眠结构紊乱,睡眠效率降低.患者具有较高的SAHS患病率,主要造成阻塞性睡眠呼吸暂停.椎动脉血管内支架成形术治疗可改善缺血性脑血管病患者的睡眠呼吸紊乱及缺氧状况.     

Relevance of linearizing nasal prongs for assessing hypopneas and flow limitation during sleep

Respiratory disturbances in patients with the sleep apnea-hypopnea syndrome (SAHS) may be detected by means of nasal prongs (NP) pressure (PNP). Nevertheless, PNP is nonlinearly related to flow (V). Our aim was to demonstrate the relevance of linearizing P NP for assessing hypopneas and flow limitation in SAHS. V was measured with a pneumotachograph during the hypopneas and flow limitation events in a continuous positive airway pressure (CPAP) titration in six patients with severe SAHS. These flow patterns were reproduced by a flow generator through an analog of the nares and recorded by NP. PNP was linearized [V NP = (PNP)1/2] by a specially designed analog circuit. For each event we used V, P NP, and V NP to compute the hypopnea flow amplitude (HFA) and a flow limitation index (FLI). Owing to NP nonlinearity, PNP considerably misestimated HFA and FLI. By contrast, V NP provided HFA and FLI values that were very close to those obtained from V: HFA (V NP) = 1.098. HFA(V) - 0.063 (r2 = 0.98) and FLI(V NP) = 1.044. FLI(V) + 0.004 (r2 = 0.99). Square-root linearization of NP greatly increases the accuracy of quantifying hypopneas and flow limitation. This procedure, which could be readily carried out in routine practice by means of the analog circuit we developed, is of interest in optimizing the assessment of respiratory sleep disturbances in SAHS.     

A nasal cannula can be used to treat obstructive sleep apnea

RATIONALE: Obstructive sleep apnea syndrome is due to upper airway obstruction and is associated with increased morbidity. Although continuous positive airway pressure efficaciously treats obstructive apneas and hypopneas, treatment is impeded by low adherence rates. OBJECTIVES: To assess the efficacy on obstructive sleep apnea of a minimally intrusive method for delivering warm and humidified air through an open nasal cannula. METHODS: Eleven subjects (age, 49.7+/-5.0 yr; body mass index, 30.5+/-4.3 kg/m2), with obstructive apnea-hypopnea syndrome ranging from mild to severe (5 to 60 events/h), were administered warm and humidified air at 20 L/minute through an open nasal cannula. MEASUREMENTS AND MAIN RESULTS: Measurements were based on standard sleep-disordered breathing and arousal indices. In a subset of patients pharyngeal pressure and ventilation were assessed to determine the mechanism of action of treatment with nasal insufflation. Treatment with nasal insufflation reduced the mean apnea-hypopnea index from 28+/-5 to 10+/-3 events per hour (p<0.01), and reduced the respiratory arousal index from 18+/-2 to 8+/-2 events per hour (p<0.01). Treatment with nasal insufflation reduced the apnea-hypopnea index to fewer than 10 events per hour in 8 of 11 subjects, and to fewer than 5 events per hour in 4 subjects. The mechanism of action appears to be through an increase in end-expiratory pharyngeal pressure, which alleviated upper airway obstruction and improved ventilation. CONCLUSIONS: Our findings demonstrate clinical proof of concept that a nasal cannula for insufflating high airflows can be used to treat a diverse group of patients with obstructive sleep apnea.     

Nasal pressure recordings to detect obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common disease. Given the costs of in-laboratory polysomnography (PSG), alternative ambulatory methods for accurate diagnosis are desirable. The objective of this study was to evaluate the performance of a simple device (SleepCheck) to identify patients with sleep apnea. A total of 30 consecutive patients with suspected OSA syndrome referred to the sleep clinic were prospectively evaluated with standard PSG and SleepCheck simultaneously during an in-laboratory, supervised full-night diagnostic study. The PSG apnea and hypopnea index (AHI) was evaluated according to standard criteria, and SleepCheck assessed the respiratory disturbance index (RDI) based on nasal cannula pressure fluctuations. Compared to the full-night PSG, SleepCheck systematically overscored respiratory events (the mean difference between SleepCheck RDI and PSG AHI was 27.4±13.3 events per hour). This overscoring was in part related to normal physiologic decreases in flow during rapid eye movement sleep or after an arousal. However, there was reasonable correlation between AHI and RDI (r=0.805). Receiver operating characteristic curves with threshold values of AHI of 10 and 20/h demonstrated areas under the curves (AUCs) of 0.915 and 0.910, respectively. Optimum combinations of sensitivity and specificity for these thresholds were calculated as 86.4/75.0 and 88.9/81.0, respectively. Overall, the SleepCheck substantially overscored apneas and hypopneas in patients with suspected OSA. However, after correction of the bias, the SleepCheck had reasonable accuracy with an AUC, sensitivity, and specificity similar to other ambulatory type 4 devices currently available.This study was conducted at the Sleep Laboratory and Division of Orthodontics, The University of British Columbia, Canada     

The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep apnea/hypopnea syndrome

The effect of posture on upper airway dimensions was assessed for two reasons. First, some patients with untreated sleep apnea/hypopnea syndrome (SAHS) report they sleep better sitting upright. Second, to allow comparison of the differing techniques used to determine the site of maximal airway narrowing in awake patients with SAHS, as some are carried out in the erect and others in the supine posture. Lateral cephalometry was therefore carried out in 33 nonsnoring normal subjects and in 29 patients with obstructive SAHS (mean apneas plus hypopneas, 46 per hour; range, 17 to 103). In both normal subjects and patients, uvular width was increased (p less than 0.05) in the supine posture, and this was associated with significant narrowing of the retropalatal airway in the patients with SAHS (erect, 5.0 +/- SD 2.6 mm; supine, 3.6 +/- 2.8 mm; p less than 0.01). In both normal subjects and patients, the retroglossal hypopharynx widened (p less than 0.05) in the supine posture (e.g., in patients with SAHS, posterior airway space was: erect, 11.5 +/- 4.5 mm; supine, 13.4 +/- 4.8 mm; p = 0.003). In the supine posture there was anterior movement of the hyoid and neck flexion in both groups. However, a study of the effect of neck flexion in the erect posture showed that neck flexion produced no changes in airway caliber. Thus, posture is an important determinant of upper airway dimensions.     

Validation of the WristOx 3100? oximeter for the diagnosis of sleep apnea/hypopnea syndrome

OBJECTIVE: To evaluate the diagnostic accuracy of the Nonin WristOx 3100 and its software (nVision 5.0) in patients with suspicion of sleep apnea/hypopnea syndrome (SAHS). METHODS: All participants (168) had the oximetry and polysomnography simultaneously. The two recordings were interpreted blindly. The software calculated: adjusted O(2) desaturation index [ADI]-mean number of O(2) desaturation per hour of total recording analyzed time of >/= 2%, 3%, 4%, 5%, and 6% (ADI2, 3, 4, 5, and 6) and AT90-accumulated time at SO(2) < 90%. The ADI2, 3, 4, 5, and 6 and the AT90 cutoff points that better discriminated between subjects with or without SAHS arose from the receiver operating characteristic curve analysis. The sensitivity (S), specificity (E), and positive and negative likelihood ratio (LR+, LR-) for the different thresholds for ADI were calculated. RESULTS: One hundred and fifty-four patients were included (119 men, mean age 51, median apnea/hypopnea index [AHI] 14, median body mass index [BMI] 28.3 kg/m(2)). The best cutoff points of ADI were: SAHS = AHI >/= 5: ADI2 > 19.3 (S 89%, E 94%, LR+ 15.5 LR- 0.11); SAHS =AHI >/= 10: ADI3 > 10.5 (S 88%, E 94%, LR+ 15 LR- 0.12); SAHS = AHI >/= 15: ADI3 > 13.4 (S 88%, E 90%, LR+ 8.9, LR- 0.14). AT90 had the lowest diagnosis accuracy. An ADI2 /= 5 and 10; S 100%, LR- 0) and ADI3 > 4.3 (AHI >/= 5 and 10) or 32 (AHI >/= 15) confirmed SAHS (E 100%). CONCLUSIONS: A negative oximetry defined as ADI2 /= 5 or 10 with a sensitivity and negative likelihood ratio of 100% and 0%, respectively. Furthermore, a positive oximetry defined as an ADI3 > 32 (SAHS = AHI >/= 15) had a specificity of 100% to confirm the pathology.     

Static and dynamic upper airway obstruction in sleep apnea: role of the breathing gas properties

Increased upper airway collapsibility in the sleep apnea/hypopnea syndrome (SAHS) is usually interpreted by a collapsible resistor model characterized by a critical pressure (Pcrit) and an upstream resistance (Rup). To investigate the role played by the upstream segment of the upper airway, we tested the hypothesis that breathing different gases would modify Rup but not Pcrit. The study was performed on 10 patients with severe SAHS (apnea-hypopnea index: 59 +/- 14 events/hour) when breathing air and helium-oxygen (He-O2) during non-REM sleep. The continuous positive airway pressure that normalized flow (CPAPopt) was measured. Rup and Pcrit were determined from the linear relationship between maximal inspiratory flow VImax and nasal pressure (PN):VImax = (PN - Pcrit)/Rup. Changing the breathing gas selectively modified the severity of dynamic (CPAPopt, Rup) and static (Pcrit) obstructions. CPAPopt was significantly (p = 0.0013) lower when breathing He-O2 (8.44 +/- 1.66 cm H2O; mean +/- SD) than air (10.18 +/- 2.34 cm H2O). Rup was markedly lower (p = 0.0001) when breathing He-O2 (9.21 +/- 3.93 cm H2O x s/L) than air (15.92 +/- 6.27 cm H2O x s/L). Pcrit was similar (p = 0.039) when breathing He-O2 (4.89 +/- 2.37 cm H2O) and air (4.19 +/- 2.93 cm H2O). The data demonstrate the role played by the upstream segment of the upper airway and suggest that different mechanisms determine static (Pcrit) and dynamic (Rup) upper airway obstructions in SAHS.     

Effect of flurazepam on sleep-disordered breathing and nocturnal oxygen desaturation in asymptomatic subjects

We assessed the effect of 30 mg of oral flurazepam on sleep-disordered breathing and nocturnal oxygen desaturation by performing a double-blind, placebo-controlled, randomized study. Asymptomatic subjects, 17 men and three women (mean age 49 years, mean weight 79 kg), were monitored for two consecutive nights. Flurazepam was given to 10 subjects on night 1 and to 10 subjects on night 2. Placebo was ingested on the other nights. Polysomnographic determinations included chest wall movement by impedance pneumography, nasal and oral airflow by thermistor probes, and continuous oxygen saturation by ear oximetry. Flurazepam was associated with significant increases in the number of sleep events (p = 0.01), episodes of apnea (p < 0.01), and total duration of apnea (p < 0.01). The number of episodes of hypopnea of desaturation did not significantly increase, although the degree of desaturation increased after flurazepam ingestion (p = 0.04). Total sleep time significantly increased (p = 0.04), but could not account for the increased number of events. Sleep stage distribution was minimally altered by ingestion of flurazepam.     

Effects of sleep apnea hypopnea syndromes on cardiovascular events: a systematic review and meta-analysis

Sleep and Breathing - Previous studies suggest that sleep apnea hypopnea syndrome (SAHS) is an independent risk factor that contributes to certain cardiovascular events. However, there are studies...     

Validity analysis of respiratory events of polysomnography using a plethysmography chest and abdominal belt

Purpose

Respiratory inductive plethysmography (RIP) is recommended as an alternative respiratory sensor for the identification of each apnea and hypopnea event in polysomnography. Using this sensor, the cumulative RIP results from the chest and abdomen (RIP sum) and time-derived results of the RIP sum (RIP flow) are calculated to track respiratory flow. However, the effectiveness of this sensor and the calculated respiratory results is still unclear, and validation studies for the scoring of respiratory events in polysomnography are rare.

Methods

Two hundred subjects were selected according to the severity of obstructive sleep apnea. A sleep specialist re-evaluated the respiratory events based on RIP flow data in a single-blind study. Statistical analysis was conducted with paired respiratory events scored in each of the RIP flow and polysomnography datasets.

Results

All respiratory events scored from the RIP flow were strongly correlated with those identified with standard sensors of polysomnography, regardless of disease severity. Most of the respiratory parameters from RIP flow trended toward underestimation. The RIP flow obtained from the alternative RIP sensor was appropriate for the diagnosis of obstructive sleep apnea based on a receiver operating characteristic curve.

Conclusions

Scored respiratory events from RIP flow data effectively reflected the respiratory flow and statistically correlated with the results from standard polysomnography sensors. Therefore, analyzing RIP flow utilizing an RIP sensor is considered a reliable method for respiratory event scoring.

     

The use of combined thermal/pressure polyvinylidene fluoride film airflow sensor in polysomnography

Background

The technologies recommended by the American Academy of Sleep Medicine (AASM) to monitor airflow in polysomnography (PSG) include the simultaneous monitoring of two physical variables: air temperature (for thermal airflow) and air pressure (for nasal pressure). To comply with airflow monitoring standards in the sleep lab setting thus often requires the patient to wear two sensors under the nose during testing. We hypothesized that a single combined thermal/pressure sensor using polyvinylidene fluoride (PVDF) film responsive to both airflow temperature and pressure would be effective in documenting abnormal breathing events during sleep.

Methods

Sixty patients undergoing routine PSG testing to rule out obstructive sleep apnea at two different sleep laboratories were asked to wear a third PVDF airflow sensor in addition to the traditional thermal sensor and pressure sensor. Apnea and hypopnea events were scored by the sleep lab technologists using the AASM guidelines (CMS option) using the thermal sensor for apnea and the pressure sensor for hypopnea (scorer 1). The digital PSG data were also forwarded to an outside registered polysomnographic technologist for scoring of respiratory events detected in the PVDF airflow channels (scorer 2).

Results

The Pearson correlation coefficient, r, between apnea and hypopnea indices obtained using the AASM sensors and the combined PVDF sensor was almost unity for the four calculated indices: apnea–hypopnea index (0.990), obstructive apnea index (0.992), hypopnea index (0.958), and central apnea index (1.0). The slope of the four relationships was virtually unity and the coefficient of determination (r ²) was also close to 1. The results of intraclass correlation coefficients (>0.95) and Bland–Altman plots also provide excellent agreement between the combined PVDF sensor and the AASM sensors.

Conclusion

The indices used to calculate apnea severity obtained with the combined PVDF thermal and pressure sensor were equivalent to those obtained using AASM-recommended sensors.