Choice of Oximeter Affects Apnea-Hypopnea Index

Validation of the Nox-T3 Portable Monitor for Diagnosis of Obstructive Sleep Apnea in Patients With Chronic Obstructive Pulmonary Disease

STUDY OBJECTIVES

Clinical practice guidelines recommend polysomnography (PSG) for diagnosis of obstructive sleep apnea (OSA) in patients with major comorbidities. We evaluated home sleep apnea testing (HSAT) using a type 3 portable monitor (PM, Nox-T3, Nox Medical, Reykjavik, Iceland) to diagnose OSA in adults with chronic obstructive pulmonary disease (COPD).

METHODS

Ninety adults with COPD (89.0% males, mean ± standard deviation age 66.5 ± 7.8 years, body mass index 27.5 ± 5.8 kg/m², forced expiratory volume in the first second/forced vital capacity [FEV₁/ FVC] 53.5 ± 12.4%, FEV₁ 54.0 ± 18.4% predicted) underwent unattended HSAT followed by an in-laboratory PSG with simultaneous PM recording.

RESULTS

Scoring hypopneas with a ≥ 4% oxygen desaturation, the apnea-hypopnea index (AHI) was 16.7 ± 20.6 events/h on HSAT, 20.0 ± 23.3 events/h on in-laboratory PM, and 21.2 ± 26.2 events/h on PSG (P < .0001). Bland-Altman analysis of AHI on HSAT versus PSG showed a mean difference (95% confidence interval) of -5.08 (-7.73, -2.42) events/h (P = .0003) and limits of agreement (± 2 standard deviations) of -30.00 to 19.85 events/h; HSAT underestimated AHI to a greater extent for more severe values (rho = -.529, P < .0001). Using an AHI ≥ 5 events/h to diagnose OSA, HSAT had 95% sensitivity, 78% specificity, 88% positive predictive value, and 89% negative predictive value compared to PSG. Mean oxygen saturation was 93.2 ± 3.7% on PSG, 91.0 ± 3.3% on in-laboratory PM, and 90.8 ± 4.0% on HSAT (P < .0001). Percentage time oxygen saturation ≤ 88% was 17.9 ± 26.4% on HSAT, 17.4 ± 25.5% on in-laboratory PM, and 10.0 ± 21.1% on PSG (P < .0001).

CONCLUSIONS

The Nox-T3 PM can be used to diagnose OSA in patients with COPD but, most likely due to differences among pulse oximeters, a greater number of patients with COPD and without OSA qualified for nocturnal oxygen treatment using this PM than PSG.

High Interrater Reliability of Overnight Pulse Oximetry Interpretation Among Inexperienced Physicians Using a Structured Template

STUDY OBJECTIVES

To assess the interrater reliability and accuracy of overnight pulse oximetry (OPO) interpretations by pulmonary fellows using a comprehensive structured template and after a brief educational session.

METHODS

Using the template, four pulmonary and critical care (PCC) fellows interpreted OPO saturation waveforms and parameters extracted from 50 adult consecutive in-laboratory sleep studies. The template included three saturation parameters (mean saturation, oxygen desaturation index [ODI], and cumulative desaturation time) and description of the saturation waveform. A scoring system was proposed combining waveform characteristics and ODI to determine the suspicion for moderate to severe sleep apnea. Waveform description and mean saturation determined the suspicion for cardiopulmonary disease (CPD). Cumulative desaturation time determined need for oxygen prescription. Apnea-hypopnea index was extracted from the sleep study results.

RESULTS

The overall interrater reliability for final recommendations (sleep apnea suspicion, presence of CPD, and oxygen prescription) was high (kappa = .81, 95% confidence interval [CI] .76-.88). Good agreement was noted in CPD evaluation and suspicion of moderate to severe sleep apnea (kappa = .70, 95% CI .46-.86 and kappa = .65, 95% CI .56-.77 respectively). The interrater reliability for oxygen prescription was in an excellent range (kappa = .98, 95% CI .91-1.00). The accuracy of a high sleep apnea suspicion score in detecting apnea-hypopnea index ≥ 15 events/h ranged from 88.0% to 94.0% (sensitivity 91.3% to 95.7%, specificity 81.5% to 92.6%). Desaturations due to CPD were identified by 75% of the raters as desaturations due to conditions other than sleep apnea.

CONCLUSIONS

A structured template for OPO interpretation can produce a high interrater agreement and good accuracy, and make it a reliable clinical tool.

COMMENTARY

A commentary on this article appears in this issue on page 497.

Comparison of two home sleep testing devices with different strategies for diagnosis of OSA

PURPOSE

Home sleep testing devices are being widely used in diagnosis/screening for obstructive sleep apnea (OSA). We examined differences in OSA metrics obtained from two devices with divergent home monitoring strategies, the Apnea Risk Evaluation System (ARES™, multiple signals plus forehead reflectance oximetry) and the Nonin WristOx₂™ (single channel finger transmission pulse oximeter), compared to differences from night-night variability of OSA.

METHODS

One hundred fifty-two male/26 female subjects (BMI = 30.3 ± 5.6 kg/m², age = 52.5 ± 8.9 years) were recruited without regard to OSA symptoms and simultaneously wore both ARES™ and Nonin WristOx₂™ for two nights (n = 351 nights). Automated analysis of the WristOx₂ yielded oxygen desaturation index (ODI_Ox2, ≥4% O2 dips/h), and automated analysis with manual editing of ARES™ yielded AHI4_ARES (apneas + hypopneas with ≥4% O2 dips/h) and RDI_ARES (apneas + hypopneas with ≥4% O2 dips/h or arousal surrogates). Baseline awake oxygen saturation, percent time < 90% O2 saturation (%time < 90%O2Sat), and O2 signal loss were compared between the two methods.

RESULTS

Correlation between AHI4_ARES and ODI_Ox2 was high (ICC = 0.9, 95% CI = 0.87-0.92, p < 0.001, bias ± SD = 0.7 ± 6.1 events/h). Agreement values for OSA diagnosis (77-85%) between devices were similar to those seen from night-to-night variability of OSA using a single device. Awake baseline O2 saturation was significantly higher in the ARES™ (96.2 ± 1.6%) than WristOx₂™ (92.2 ± 2.1%, p < 0.01). There was a significantly lower %time < 90%O2Sat reported by the ARES™ compared to WristOx₂ (median (IQR) 0.5 (0.0, 2.6) vs. 2.1 (0.3, 9.7), p < 0.001), and the correlation was low (ICC = 0.2).

CONCLUSIONS

OSA severity metrics predominantly dependent on change in oxygen saturation and metrics used in diagnosis of OSA (AHI4 and ODI) correlated well across devices tested. However, differences in cumulative oxygen desaturation measures (i.e., %time < 90%O2Sat) between the devices suggest that caution is needed when interpreting this metric particularly in populations likely to have significant hypoxia.

The Need to Apply Medical Device Informatics in Developing Standards for Safe Interoperable Medical Systems

Medical device and health information technology systems are increasingly interdependent with users demanding increased interoperability. Related safety standards must be developed taking into account these systems' perspective. In this article, we describe the current development of medical device standards and the need for these standards to address medical device informatics. Medical device information should be gathered from a broad range of clinical scenarios to lay the foundation for safe medical device interoperability. Five clinical examples show how medical device informatics principles, if applied in the development of medical device standards, could help facilitate the development of safe interoperable medical device systems. These examples illustrate the clinical implications of the failure to capture important signals and device attributes. We provide recommendations relating to the coordination between historically separate standards development groups, some of which focus on safety and effectiveness and others focus on health informatics. We identify the need for a shared understanding among stakeholders and describe organizational structures to promote cooperation such that device-to-device interactions and related safety information are considered during standards development.

The Importance of State and Context in Safe Interoperable Medical Systems

This paper describes why “device state” and “patient context” information are necessary components of device models for safe interoperability. This paper includes a discussion of the importance of describing the roles of devices with respect to interactions (including human user workflows involving devices, and device to device communication) within a system, particularly those intended for use at the point-of-care, and how this role information is communicated. In addition, it describes the importance of clinical scenarios in creating device models for interoperable devices.

Prevalence of sleep-disordered breathing in a multiethnic Asian population in Singapore: A community-based study

BACKGROUND AND OBJECTIVE

Limited data exist on the prevalence variation in sleep-disordered breathing (SDB) across different Asian ethnicities. This population study aimed to estimate the prevalence of SDB in Singapore, a multiethnic nation, and to quantify the prevalence variation among Chinese, Malays and Indians.

METHODS

The Singapore Health Study 2012 was a cross-sectional population study conducted on adults aged 21-79 years. Among 2329 participants who completed baseline examination, a sample of 242 subjects completed home-based sleep testing with an Embletta device (type 3 monitor). Moderate-to-severe SDB, defined as an apnoea-hypopnoea index (AHI) of ≥15 events/h, was used to estimate prevalence.

RESULTS

The weighted estimates of the population prevalence of moderate-to-severe SDB and sleep apnoea syndrome were 30.5% and 18.1%, respectively. Of subjects with AHI ≥15, 91.0% were previously undiagnosed. Moderate-to-severe SDB prevalence varied across the Chinese (32.1%), Malays (33.8%) and Indians (16.5%). The mean body mass index (BMI) was lowest in Chinese (23.3 kg/m(2) ) and highest among Malays (26.0 kg/m(2) ) and Indians (25.4 kg/m(2) ). Compared with Chinese, Indians had lower odds of moderate-to-severe SDB after adjustment for age, sex and BMI (odds ratio 0.82, 95% CI: 0.70-0.96, P = 0.02).

CONCLUSION

Sleep-disordered breathing is prevalent but mostly undiagnosed among Asians in Singapore. There was a lower prevalence of SDB among Indians compared with Chinese that remained after adjustment for age, sex and BMI. Strategies are needed to optimize diagnosis and recognize ethnic differences in SDB prevalence.

Scoring criteria for portable monitor recordings: a comparison of four hypopnoea definitions in a population-based cohort

RATIONALE

Limited-channel portable monitors (PMs) are increasingly used as an alternative to polysomnography (PSG) for the diagnosis of obstructive sleep apnoea (OSA). However, recommendations for the scoring of PM recordings are still lacking. Pulse-wave amplitude (PWA) drops, considered as surrogates for EEG arousals, may increase the detection sensitivity for respiratory events in PM recordings.

OBJECTIVES

To investigate the performance of four different hypopnoea scoring criteria, using 3% or 4% oxygen desaturation levels, including or not PWA drops as surrogates for EEG arousals, and to determine the impact of measured versus reported sleep time on OSA diagnosis.

METHODS

Subjects drawn from a population-based cohort underwent a complete home PSG. The PSG recordings were scored using the 2012 American Academy of Sleep Medicine criteria to determine the apnoea-hypopnoea index (AHI). Recordings were then rescored using only parameters available on type 3 PM devices according to different hypopnoea criteria and patients-reported sleep duration to determine the 'portable monitor AHIs' (PM-AHIs).

MAIN RESULTS

312 subjects were included. Overall, PM-AHIs showed a good concordance with the PSG-based AHI although it tended to slightly underestimate it. The PM-AHI using 3% desaturation without PWA drops showed the best diagnostic accuracy for AHI thresholds of ≥ 5/h and ≥ 15/h (correctly classifying 94.55% and 93.27% of subjects, respectively, vs 80.13% and 87.50% with PWA drops). There was a significant but modest correlation between PWA drops and EEG arousals (r=0.20, p=0.0004).

CONCLUSION

Interpretation of PM recordings using hypopnoea criteria which include 3% desaturation without PWA drops as EEG arousal surrogate showed the best diagnosis accuracy compared with full PSG.

Sedation-related complications in gastrointestinal endoscopy

Defining the risk of procedural sedation for gastrointestinal endoscopic procedures remains a vexing challenge. The definitions as to what constitutes a cardiopulmonary unplanned event are beginning to take focus but the existing literature is an amalgam of various definitions and subjective outcomes, providing a challenge to patient, practitioner, and researcher. Gastrointestinal endoscopy when undertaken by trained personnel after the appropriate preprocedural evaluation and in the right setting is a safe experience. However, significant challenges exist in further quantifying the sedation risks to patients, optimizing physiologic monitoring, and sublimating the pharmacoeconomic and regulatory embroglios that limit the scope of practice and the quality of services delivered to patients.

The American Academy of Sleep Medicine Inter-scorer Reliability program: respiratory events

STUDY OBJECTIVES

The American Academy of Sleep Medicine (AASM) Inter-scorer Reliability program provides a unique opportunity to compare a large number of scorers with varied levels of experience to determine agreement in the scoring of respiratory events. The objective of this paper is to examine areas of disagreement to inform future revisions of the AASM Manual for the Scoring of Sleep and Associated Events.

METHODS

The sample included 15 monthly records, 200 epochs each. The number of scorers increased steadily during the period of data collection, reaching more than 3,600 scorers by the final record. Scorers were asked to identify whether an obstructive, mixed, or central apnea; a hypopnea; or no event was seen in each of the 200 epochs. The "correct" respiratory event score was defined as the score endorsed by the most scorers. Percentage agreement with the majority score was determined for each epoch and the mean agreement determined.

RESULTS

The overall agreement for scoring of respiratory events was 93.9% (κ = 0.92). There was very high agreement on epochs without respiratory events (97.4%), and the majority score for most of the epochs (87.8%) was no event. For the 364 epochs scored as having a respiratory event, overall agreement that some type of respiratory event occurred was 88.4% (κ = 0.77). The agreement for epochs scored as obstructive apnea by the majority was 77.1% (κ = 0.71), and the most common disagreement was hypopnea rather than obstructive apnea (14.4%). The agreement for hypopnea was 65.4% (κ = 0.57), with 16.4% scoring no event and 14.8% scoring obstructive apnea. The agreement for central apnea was 52.4% (κ = 0.41). A single epoch was scored as a mixed apnea by a plurality of scorers.

CONCLUSIONS

The study demonstrated excellent agreement among a large sample of scorers for epochs with no respiratory events. Agreement for some type of event was good, but disagreements in scoring of apnea vs. hypopnea and type of apnea were common. A limitation of the analysis is that most of the records had normal breathing. A review of controversial events yielded no consistent bias that might be resolved by a change of scoring rules.

[Nocturnal monitoring of home non-invasive ventilation: Contribution of simple tools such as pulse-oximetry, capnography, built-in ventilator software and autonomic markers of sleep fragmentation]

Complex respiratory events, which may have a detrimental effect on both quality of sleep and control of nocturnal hypoventilation, occur during sleep in patients treated by non-invasive ventilation (NIV). Among these events are patient-ventilator asynchrony, increases in upper airway resistance with or without increased respiratory drive, and leaks. Detection of these events is important in order to select the most appropriate ventilator settings and interface. Simple tools can provide important information when monitoring NIV. Pulse-oximetry is important to ensure that an adequate SpO2 is provided, and to detect either prolonged or short and recurrent desaturations. However, the specificity of pulse-oximetry tracings under NIV is low. Transcutaneous capnography discriminates between hypoxemia related to V/Q mismatch and hypoventilation, documents correction of nocturnal hypoventilation, and may detect ventilator-induced hyperventilation, a possible cause for central apnea/hypopnea and glottic closure. Data provided by ventilator software helps the clinician by estimating ventilation, tidal volume, leaks, rate of inspiratory or expiratory triggering by the patient, although further validation of these signals by independent studies is indicated. Finally, autonomic markers of sympathetic tone using signals such as pulse wave amplitude of the pulse-oximetry signal can provide reliable information of sleep fragmentation.

Agreement in computer-assisted manual scoring of polysomnograms across sleep centers

STUDY OBJECTIVES

To determine intersite agreement in respiratory event scoring of polysomnograms (PSGs) using different hypopnea definitions.

DESIGN

Technical assessment.

SETTING

Five academic medical centers.

PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Seventy good-quality PSGs performed in middle-aged women were manually scored by two experienced technologists at each of the five sleep centers using the particular laboratory's own software system. Studies were scored once by each scorer using American Academy of Sleep Medicine (AASM) standards for scoring sleep stages, arousals, and apneas. Hypopneas were then scored using three different AASM criteria: recommended, alternate, and research (Chicago). Means of each PSG variable for the scorers at each site were used to calculate an across-site intraclass correlation coefficient (ICC). Average AHI across the 10 scorers was 7.4 ± 12.3 (standard deviation) events/h using recommended criteria (ICC 0.984; 95% confidence interval [CI] 0.977-0.990), 12.1 ± 13.3 events/h using alternate criteria (ICC 0.947; 95% CI 0.889-0.972), and 15.1 ± 13.9 events/h with Chicago criteria (ICC 0.800; 95% CI 0.768-0.828). ICC across sites was 0.870 (95% CI = 0.847-0.889) for total sleep time, 0.861 (95% CI 0.837-0.881) for number of obstructive apneas and 0.683 (95% CI 0.640-0.722) for number of central apneas. ICCs across sites for hypopneas were very good using recommended criteria (ICC 0.843; 95% CI 0.820-0.870) but decreased when alternate criteria (ICC 0.728; 95% CI 0.689-0.763) and Chicago criteria (ICC 0.535; 95% CI 0.485-0.583) were used.

CONCLUSION

Experienced scorers at different laboratories have very good agreement in hypopnea and AHI results when good-quality PSGs are scored using AASM-recommended criteria. Substantial degradation of reliability was observed for alternative definitions of hypopneas, particularly that proposed for research.

Agreement in the scoring of respiratory events and sleep among international sleep centers

STUDY OBJECTIVES

The American Academy of Sleep Medicine (AASM) guidelines for polysomnography (PSG) scoring are increasingly being adopted worldwide, but the agreement among international centers in scoring respiratory events and sleep stages using these guidelines is unknown. We sought to determine the interrater agreement of PSG scoring among international sleep centers.

DESIGN

Prospective study of interrater agreement of PSG scoring.

SETTING

Nine center-members of the Sleep Apnea Genetics International Consortium (SAGIC).

MEASUREMENTS AND RESULTS

Fifteen previously recorded deidentified PSGs, in European Data Format, were scored by an experienced technologist at each site after they were imported into the locally used analysis software. Each 30-sec epoch was manually scored for sleep stage, arousals, apneas, and hypopneas using the AASM recommended criteria. The computer-derived oxygen desaturation index (ODI) was also recorded. The primary outcome for analysis was the intraclass correlation coefficient (ICC) of the apnea-hypopnea index (AHI). The ICCs of the respiratory variables were: AHI = 0.95 (95% confidence interval: 0.91-0.98), total apneas = 0.77 (0.56-0.87), total hypopneas = 0.80 (0.66-0.91), and ODI = 0.97 (0.93-0.99). The kappa statistics for sleep stages were: wake = 0.78 (0.77-0.79), nonrapid eye movement = 0.77 (0.76-0.78), N1 = 0.31 (0.30-0.32), N2 = 0.60 (0.59-0.61), N3 = 0.67 (0.65-0.69), and rapid eye movement = 0.78 (0.77-0.79). The ICC of the arousal index was 0.68 (0.50-0.85).

CONCLUSION

There is strong agreement in the scoring of respiratory events among the SAGIC centers. There is also substantial epoch-by-epoch agreement in scoring sleep variables. Our results suggest that centralized scoring of PSGs may not be necessary in future research collaboration among international sites where experienced, well-trained scorers are involved.

Automated frequency domain analysis of oxygen saturation as a screening tool for SAHS

Sleep apnea-hypopnea syndrome (SAHS) is significantly underdiagnosed and new screening systems are needed. The analysis of oxygen desaturation has been proposed as a screening method. However, when oxygen saturation (SpO(2)) is used as a standalone single channel device, algorithms working in time domain achieve either a high sensitivity or a high specificity, but not usually both. This limitation arises from the dependence of time-domain analysis on absolute SpO(2) values and the lack of standardized thresholds defined as pathological. The aim of this study is to assess the degree of concordance between SAHS screening using offline frequency domain processing of SpO(2) signals and the apnea-hypopnea index (AHI), and the diagnostic performance of such a new method. SpO(2) signals from 115 subjects were analyzed. Data were divided in a training data set (37) and a test set (78). Power spectral density was calculated and related to the desaturation index scored by physicians. A frequency desaturation index (FDI) was then estimated and its accuracy compared to the classical desaturation index and to the apnea-hypopnea index. The findings point to a high diagnostic agreement: the best sensitivity and specificity values obtained were 83.33% and 80.44%, respectively. Moreover, the proposed method does not rely on absolute SpO(2) values and is highly robust to artifacts.

Pulse oximetry for the detection of obstructive sleep apnea syndrome: can the memory capacity of oxygen saturation influence their diagnostic accuracy?

Objective. To assess the diagnostic ability of WristOx 3100 using its three different recording settings in patients with suspected obstructive sleep apnea syndrome (OSAS). Methods. All participants (135) performed the oximetry (three oximeters WristOx 3100) and polysomnography (PSG) simultaneously in the sleep laboratory. Both recordings were interpreted blindly. Each oximeter was set to one of three different recording settings (memory capabilities 0.25, 0.5, and 1 Hz). The software (nVision 5.1) calculated the adjusted O₂ desaturation index-mean number of O₂ desaturation per hour of analyzed recording ≥2, 3, and 4% (ADI2, 3, and 4). The ADI2, 3, and 4 cutoff points that better discriminated between subjects with or without OSAS arose from the receiver-operator characteristics (ROCs) curve analysis. OSAS was defined as a respiratory disturbance index (RDI) ≥ 5. Results. 101 patients were included (77 men, mean age 52, median RDI 22.6, median BMI 27.4 kg/m²). The area under the ROCs curves (AUC-ROCs) of ADI2, 3, and 4 with different data storage rates were similar (AUC-ROCs with data storage rates of 0.25/0.5/1 Hz: ADI2: 0.958/0.948/0.965, ADI3: 0.961/0.95/0.966, and ADI4: 0.957/0.949/0.963, P NS). Conclusions. The ability of WristOx 3100 to detect patients with OSAS was not affected by the data storage rate of the oxygen saturation signal. Both memory capacity of 0.25, 0.5, or 1 Hz showed a similar performance for the diagnosis of OSAS.

A comparison of respiratory patterns in healthy term infants placed in car safety seats and beds

OBJECTIVE

The purpose of this work was to compare the incidence of apnea, hypopnea, bradycardia, or oxygen desaturation in healthy term newborns placed in hospital cribs, infant car safety beds, or infant car safety seats.

METHODS

A consecutive series of 200 newborns was recruited on the second day of life. Each subject was studied while placed in the hospital crib (30 minutes), car bed (60 minutes), and car seat (60 minutes). Physiologic data, including oxygen saturation, frequency, and type of apnea, hypopnea, and bradycardia were obtained and analyzed in a blinded manner.

RESULTS

The mean oxygen saturation level was significantly different among all of the positions (97.9% for the hospital crib, 96.3% for the car bed, and 95.7% for the car seat; P < .001). The mean minimal oxygen saturation level was lower while in both safety devices (83.7% for the car bed and 83.6% for the car seat) compared with in the hospital crib (87.4%) (P < .001). The mean total time spent with an oxygen saturation level of <95% was significantly higher (P = .003) in both safety devices (car seat: 23.9%; car bed: 17.2%) when compared with the hospital crib (6.5%). A second study of 50 subjects in which each infant was placed in each position for 120 minutes yielded similar results.

CONCLUSIONS

In healthy term newborns, significant desaturations were observed in both car beds and car seats as compared with hospital cribs. This study was limited by lack of documentation of sleep stage. Therefore, these safety devices should only be used for protection during travel and not as replacements for cribs.

[Why and how to diagnose sleep respiratory disorders?]

Gas exchange abnormalities occur firstly during sleep in restrictive and obstructive chronic respiratory failure. Nocturnal hypoxemia is often a revealing feature of a sleep-related hypoventilation/hypoxemia syndrome in patients who will have later a diurnal hypoxemia. On the other hand, sleep may induce breathing abnormalities in individuals without lung diseases, like in obstructive sleep apnea syndrome (OSAS). In OSAS, repeated closure and/or narrowing of the pharynx during sleep increases the inspiratory effort and induces sleep fragmentation. Intermittent hypoxemia is another consequence of the obstructive events in OSAS. Besides its direct consequences on sleep, OSAS is also associated with an increased risk of cardiovascular morbi-mortality. Reduced daytime alertness and cognitive functions are usually present in patients with sleep-disordered breathing. These features are believed to be related to both sleep fragmentation and nocturnal hypoxia/hypercapnia. Sleep-related hypoventilation/hypoxemia and pharyngeal obstructive events may occur together in patients with respiratory insufficiency, especially in obese and/or chronic obstructive pulmonary disease (COPD) subjects. A correct qualitative and quantitative assessment of sleep-disordered breathing may only be performed by recording specific physiological signals during sleep.

Pulse oximetric thresholds for tonsillectomy and adenotomy in children: significance of 1-2% decline in oxyhemoglobin saturation

OBJECTIVES

We aimed to establish optimal overnight pulse oximetric thresholds for determining the indication of tonsillectomy and adenotomy (TA) in children by revising the definition of 'desaturation'.

METHODS

One hundred and thirty four children scheduled for TA (TA group, 5.3 +/- 1.4 years old) and 112 otherwise healthy children scheduled for elective minor surgery (control group, 5.4 +/- 1.5 years old) were enrolled into this prospective study. Data were recorded and stored every 10 s using Nellcor N-395. Desaturation/resaturation events were defined as x% change (x = 1-4) of SpO2 (oxyhemoglobin saturation by pulse oximetry) in 10 s. The desaturation/resaturation indices were calculated as events per hour of total sleeping time. For each index, a wide range of temporary thresholds was set. The optimal thresholds for TA were the ones that maximized the weighted average for sensitivity, specificity (based on whether the index improved or not after TA), and the percentage of the control children whose indices were below the threshold.

RESULTS

For all the indices, the optimal thresholds that fulfilled the above condition were determined. Compared with the x = 3-4% results, the application of x = 1-2% approximately doubled the TA patients whose preoperative 'positive' indices improved after TA, with the weighted averages of 84.3-92.3% as described above.

CONCLUSIONS

By defining desaturation/resaturation as a 1-2% change in SpO2 from the preceding value, children with adenotonsillar hypertrophy whose pulse oximetric indices are expected to improve after TA can be detected by pulse oximetry with relatively high sensitivity and specificity.

Diagnosis of obstructive sleep apnea syndrome and its outcomes with home portable monitoring

BACKGROUND

The use of portable respiratory monitoring (PM) has been proposed for the diagnosis of obstructive sleep apnea syndrome (OSAS), but most studies that validate PM accuracy have not followed the best standards for diagnostic test validation. The objective of the present study was to evaluate the accuracy of PM performed at home to diagnose OSAS and its outcomes after first validating PM in the laboratory setting by comparing it to polysomnography (PSG).

METHODS

Patients with suspected OSAS were submitted, in random order, to PM at the sleep laboratory concurrently with PSG (lab-PM) or at home-PM. The diagnostic performance was assessed by sensitivity, specificity, positive and negative predictive values, positive likelihood ratio (+LR), negative likelihood ratio (-LR), intraclass correlation coefficients, kappa statistic, and Bland-Altman plot.

RESULTS

One hundred fifty-seven subjects (73% men, mean age +/- SD, 45 +/- 12 yr) with an apnea-hypopnea index (AHI) of 31 (SD +/- 29) events/h were studied. Excluding inadequate recordings, 149 valid comparisons with lab-PM and 121 with unattended home-PM were obtained. Compared to PSG for detecting AHI > 5, the lab-PM demonstrated sensitivity of 95.3%, specificity of 75%, +LR of 3.8, and -LR of 0.11; the home-PM exhibited sensitivity of 96%, specificity of 64%, +LR of 2.7, and -LR of 0.05. Kappa statistics indicated substantial correlation between PSG and PM results. Bland-Altman plot showed smaller dispersion for lab-PM than for home-PM. Pearson product moment correlation coefficients among the three AHIs and clinical outcomes were similar, denoting comparable diagnostic ability.

CONCLUSIONS

This study used all available comparison methods to demonstrate accuracy of PM in-home recordings similar to that of repeated PSGs. PM increases the possibility of correctly diagnosing and effectively treating OSAS in populations worldwide.

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 > or = 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 > or = 5: ADI2 > 19.3 (S 89%, E 94%, LR+ 15.5 LR- 0.11); SAHS =AHI > or = 10: ADI3 > 10.5 (S 88%, E 94%, LR+ 15 LR- 0.12); SAHS = AHI > or = 15: ADI3 > 13.4 (S 88%, E 90%, LR+ 8.9, LR- 0.14). AT90 had the lowest diagnosis accuracy. An ADI2 < or = 12.2 excluded SAHS (AHI > or = 5 and 10; S 100%, LR- 0) and ADI3 > 4.3 (AHI > or = 5 and 10) or 32 (AHI > or = 15) confirmed SAHS (E 100%).

CONCLUSIONS

A negative oximetry defined as ADI2 < or = 12.2 excluded SAHS defined as AHI > or = 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 > or = 15) had a specificity of 100% to confirm the pathology.

Prevalence and severity of sleep apnea in a group of morbidly obese patients

BACKGROUND

Obesity is the most important risk factor for obstructive sleep apnea. It is estimated that 70% of sleep apnea patients are obese. In the morbidly obese, the prevalence may reach 80% in men and 50% in women. The aim of this study was to determine the prevalence and severity of sleep apnea in a group of morbidly obese patients, leading to bariatric surgery.

METHODS

In a cross-sectional study developed in Bahia, northeastern Brazil. 108 patients (78 women and 30 men) from the Obesity Treatment and Surgery Center--"Núcleo de Tratamento e Cirurgia da Obesidade" underwent standard polysomnography. Patients with an apnea-hypopnea index (AHI) > or = 5 events/hour were considered apneic.

RESULTS

Mean +/- SD for age and BMI were 37.1 +/- 10.2 years and 45.2 +/- 5.4 kg/m2, respectively. The calculated AHI ranged widely from 2.5 to 128.9 events/hour. Sleep apnea was detected in 93.6% of the sample, wherein 35.2% had mild, 30.6% moderate and 27.8% severe apnea. Oxyhemoglobin desaturation was directly related to the AHI and was more severe in men.

CONCLUSION

There was a high frequency of sleep apnea in this group of morbidly obese patients, for whom it was very important to request polysomnography, thus enabling therapeutic management and prognostication.

Minimizing complications: sedation and monitoring

Serious adverse events are fortunately quite rare for procedural sedation. Current physiologic monitoring recommendations are therefore either based on "softer" outcomes, such as transient hypoxemia, or on expert opinion. Pulse oximetry and supplemental oxygen are recommended for the reduction of hypoxemia. Outcomes-based data for extended monitoring are just starting to emerge, and one of these technologies may become a recommended component of patient monitoring. With data on more than 150,000 patients published in the literature, propofol is the most studied sedative agent for gastrointestinal endoscopy. In this author's opinion, its safety and efficacy have been established.

Rapid screening test for sleep apnea using a nonlinear and nonstationary signal processing technique

It is hypothesized that obstructive sleep apnea (OSA) can be detected from a short-time, daytime recording of the nasal airway pressure, resulting in a screening tool to identify adult patients at risk for OSA. A nonlinear and nonstationary signal analysis technique based on the Hilbert-Huang transform was used to extract signals intrinsic to OSA, using the first two intrinsic mode functions from the empirical mode decomposition. The Hilbert spectrum was centered around 1.5Hz for normal subjects and shifted upward in frequency scale with increased likelihood of OSA. The histogram of the 1.5Hz signal from the Hilbert spectrum was used to compute the apnea percentage for assessing OSA. The proposed method was tested with two data sets. Data set 1 consisted of 18 human subjects with 3 OSA cases from retrospective diagnosis. Data set 2 consisted of 16 subjects who went through a prospective study of the all-night polysomnographic test and the 5-min nasal airway pressure test. The proposed OSA detection method achieved 100% sensitivity and 100% specificity for data set 1, 85.7% sensitivity and 100% specificity for data set 2. While further tests will be needed to insure robustness and standardize the instrumentation, the study has demonstrated the feasibility of a rapid screening test for obstructive sleep apnea.