Obstructive Sleep Apnea Syndrome
Validation of a Portable Monitoring System for the Diagnosis of Obstructive Sleep Apnea Syndrome Rogerio Santos-Silva, PhD, RPSGT; Denis E. Sartori; Viviane Truksinas, RN; Eveli Truksinas, SLP; Fabiana F. F. D Alonso, RN; Sergio Tufik, MD, PhD; Lia R. A. Bittencourt, MD, PhD Discipline of Medicine and Biology of Sleep, Psychobiology Department, Universidade Federal de Sao Paulo, Sao Paulo, Brazil
Study Objective: To evaluate if a portable monitor could accurately measure the apnea-hypopnea index (AHI) in patients with a suspicion of obstructive sleep apnea (OSA). Design: Prospective and randomized. Setting: Sleep laboratory. Participants: 80 participants: 70 patients with clinical OSA suspicion and 10 subjects without suspicion of OSA. Interventions: N/A Measurements and Results: Three-order randomized evaluations were performed: (1) STD (Stardust II) used at the participants’ home (STD home), (2) STD used simultaneously with PSG in the sleep lab (STD+PSG lab), and (3) PSG performed without the STD (PSG lab). Four AHI values were generated and analyzed: (a) STD home; (b) STD from STD+PSG lab; (c) PSG from STD+PSG (named PSG+STD lab); and (d) PSG lab. Two technicians, blinded to study details, performed the analyses of all evaluations. There was a strong correlation between AHI from the STD and PSG recordings for all 4 AHI values (all correlations above 0.87). Sensitivity, specificity, and positive and
negative predictive values at AHI cut-off values of 5, 15, and 30 events/ hour were calculated. AHI values from the PSG lab and PSG+STD lab were compared to STD home and STD+PSG lab and showed the best results when STD and PSG were performed simultaneously. In all analyses, the area under ROC curve was at least 0.90. With multiple comparisons, diagnostic agreement was between 91% and 75%. The Bland Altman analyses showed strong agreement between AHI values from the STD and PSG recordings, especially when comparing the AHI from simultaneous STD and PSG recordings. Conclusion: These data suggest that the STD is accurate in confirming the diagnosis of OSA where there is a suspicion of the disorder. Better agreement occurred during simultaneous recordings. Keywords: Sleep apnea, diagnosis, portable monitoring, type 3 diagnostic device Citation: Santos-Silva R; Sartori DE; Truksinas V; Truksinas E; Alonso FFFD; TufikS; Bittencourt LRA. Validation of a portable monitoring system for the diagnosis of obstructive sleep apnea syndrome. SLEEP 2009;32(5):629-636.
THE CURRENT STANDARDS OF PRACTICE FOR DIAGNOSING OBSTRUCTIVE SLEEP APNEA (OSA) REQUIRE OVERNIGHT IN-LABORATORY POLYSOMNOGRAPHY (PSG).1 This conventional approach has been considered costly and technically complex and may present scheduling difficulties when there is high demand. Other approaches considered for their potential to reduce costs and increase accessibility have also been evaluated.2 Portable monitoring (PM) equipment including at least 4 channels (airflow, respiratory movements, oxyhemoglobin saturation [SpO2] and heart rate) is classified as a type 3 portable monitor3 and has been utilized as an alternative diagnostic test for OSA in patients with a high pre-test probability of OSA.2 Previous research has reported the equivalence of PM to PSG. Studies comparing PM with PSG have been performed on different nights.4-7 Studies simultaneously evaluating PM and PSG have been conducted using simplified PMs without the recommended 4 channels to meet the type 3 criteria,8-12 while others compared type 3 PM with PSG simultaneously.13-20 Type 3 monitors were recommended for use in attended settings if recordings were manually reviewed and patients with comorbid conditions were excluded.4 Additionally, symptomat-
ic patients with negative PM results were recommended to have an in-laboratory evaluation with full-night attended PSG.21 The use of PM for continuous positive airway pressure (CPAP) titration or a split night protocol has not been recommended.21,22 In 2004, the Center of Medicare and Medicaid Services (CMS) reviewed its national coverage determination (NCD) (#240.4) regarding the use of PM as a basis for prescribing CPAP. The use of PM remained uncovered by insurance23 until recently, when CMS released its proposed decision for modification of NCD 240.4, which now includes PM.24 The American Academy of Sleep Medicine (AASM)2 recently published clinical guidelines for the use of unattended PM in the diagnosis of OSA and concluded that unattended PM should be performed only (1) in conjunction with a comprehensive sleep evaluation, supervised by a practitioner with qualifications for certification in sleep medicine; (2) in patients with a high pretest probability of moderate to severe OSA (without comorbid conditions or other sleep disorders); (3) in patients for whom in-lab PSG is not possible by virtue of immobility, safety, or critical illness; and (4) to monitor the response to nonCPAP treatment for OSA. Thus, there is still a need to evaluate simple and accurate home diagnostic equipment for reliability and accuracy in diagnosing OSA. The aim of the present study was to demonstrate that a type 3 PM device (Stardust II, Respironics, Inc., USA) would generate AHI values similar to in-laboratory PSG for diagnosis of OSA in a randomized, prospective trial. Comparisons of the PM results were made both with and without simultaneous PSG.
Submitted for publication June, 2008 Submitted in final revised form January, 2009 Accepted for publication January, 2009 Address correspondence to: Lia R. A. Bittencourt, Address: Rua Napoleao de Barros, 925, 04024-002, Sao Paulo, Brazil; Tel: +55 11 21490155; Fax: +55 11 55725092; E-mail:
[email protected] SLEEP, Vol. 32, No. 5, 2009
629
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
METHODS
lasting ≥ 10 sec, and associated with either a 3% reduction in SpO2 or an EEG arousal. EEG arousals were quantified according American Sleep Disorders Association (ASDA) Task Force.29 The following parameters were obtained from the PSG: total recording time (TRT), total sleep time (TST), sleep latency, sleep efficiency, sleep stage distribution, arousals, awakenings, AHI, and SpO2.
Selection of Participants A consecutive sample of patients referred to the Sleep Institute for the assessment of possible OSA was recruited as participants for this study. To better stratify disease severity, a group of 10 subjects without suspicion of sleep disordered breathing was also recruited. Participants were included if they were ≥ 21 years of age, possessed the ability to provide informed consent, and were able to follow study procedures. All participants were referred to the Sleep Institute because of excessive daytime sleepiness, loud snoring, and witnessed apnea. Participants were excluded if they presented with a suspicion of insomnia, restless legs syndrome, periodic limb movements, or other nonOSA sleep disorders in a clinical interview. Participants with other severe or unstable comorbid conditions, such as severe chronic lung disease, diabetes; those receiving oxygen or mechanical ventilation; those with neurological disorders; and those who were using sedative hypnotics, stimulants, alcohol, or drugs of abuse, were also excluded. The study was approved by the Human Ethics Committee. All participants were required to provide informed consent. 2 Body mass index (BMI) (kg/m ), neck circumference (cm), and blood pressure (mm Hg) were recorded at enrollment. A detailed questionnaire25 about symptoms of snoring, sleepiness, and OSA-associated features was completed along with the Epworth Sleepiness Scale (ESS).26
Portable monitoring with the Stardust II (STD) The STD is a type 3 PM that is designed to measure and record 5 diagnostic parameters: SpO2 (via finger probe), pulse rate (from the oximeter probe), airflow (pressure based airflow through a nasal cannula), respiratory effort (piezoelectric sensor in a belt placed mid-thorax), and body position (mercury switch built into the STD unit and worn mid-sternum). An internal 9 V battery powers the STD and allows up to 10 hours of data collection. Data are collected and stored on internal memory in the device. The data are then downloaded to a computer for automated analysis by the host software (Stardust Host Software, Respironics, Inc., USA). Manual review and validation of the automatically scored data can be performed. A sleep laboratory technologist applied both the STD monitor and sensors used for the PSG recording during the overnight PSG in the sleep lab. A research assistant instructed the participants how to use the STD at home. The explanation contained consistent verbal and written instructions illustrating the correct hook-up of the STD, including diagrams and a brief demonstration. Participants were asked to activate an event marker to indicate “lights out” (when the participants settled into bed to go to sleep), “lights on” (when the participants awoke in the morning), and any time that they get up for a sustained period of time (> 15 min) during the night. The participants returned the STD to the Sleep Institute the morning after the home study so that the data could be downloaded and then manually analyzed and edited by a sleep laboratory technologist who was blinded to the participant’s other medical and sleep information. For STD scoring, hypopnea was defined as a 50% or discernable decrement in airflow lasting ≥ 10 sec with a 3% reduction in SpO2. Apneas were required to show cessation of airflow ≥ 10 sec (whether central, obstructive, or mixed). The total recording time was used in the denominator to calculate the AHI.
Protocol Participants had 3 nights of sleep evaluation: (1) a Stardust II (STD) recording done in the home for one night (STD Home); (2) a simultaneous PSG and STD recording in the lab (STD+PSG lab); and (3) a separate attended, in-laboratory PSG (without the STD) (PSG lab). The sequence of these sleep evaluations was determined randomly. All evaluations took place within a 2-week period. The 3 sleep evaluations generated 4 recordings (2 from the STD and 2 from the PSGs) and 4 dependent measures of interest: AHI from the STD home study (called STD Home), AHI from STD during the STD+PSG study (called STD+PSG lab), AHI from PSG during the STD+PSG study (called PSG+STD lab), and AHI from PSG in the laboratory (called PSG lab).
Scoring Procedures
Overnight Polysomnography
A single registered technologist manually scored all STD recordings, and another registered technologist scored all PSGs. Technicians were blinded to the presence or absence of the other recordings and the participants’ medical information. The agreement rate of PSG scoring by the technicians was determined to be 93.3% ± 5.1%, with κ of 0.91 ± 0.03. This was determined by randomly rescoring 4% of the 1042 PSG recordings from the Sleep Institute during the period from July to December 2007, by a registered technologist (RPSGT).
A standard montage was used for the PSG recordings, including electroencephalogram (EEG) (C3/A2, C4/A1, O1/A2, O2/A1), electrooculogram (EOG), submental electromyogram (EMG), left and right anterior tibialis EMG, electrocardiogram, thoraco-abdominal effort, oronasal airflow (thermistor and nasal pressure based flow measurement), SpO2 with pulse oximetry, and body position (EMBLA S7000, Embla Systems, Inc., Broomfield, CO, USA). Sleep and its stages were determined by standard EEG, EOG, and EMG criteria.27 Respiratory event scoring was based on AASM criteria.28 Hypopneas were defined as an event showing a clear amplitude reduction of the airflow during sleep (> 50%), SLEEP, Vol. 32, No. 5, 2009
Sample Size Calculation The sample size calculation was performed based on the data from the study of White and others.13 The standard deviation of 630
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
Table 1—Diagnostic and Agreement/Disagreement Criteria for AHI Obtained from the PSGs (PSG lab and PSG+STD lab) Compared to AHI from STDs (STD Home and STD+PSG lab) AHI PSG ≥ 30 < 30 < 30 < 30
AHI STD ≥ 30 PSG AHI ± 10 or less PSG AHI + > 10 PSG AHI − > 10
Table 2—Demographics of the 80 Participants Evaluated (mean ± SD) Age, years M:F, % BMI, kg/m2 Neck circumference, cm Systolic blood pressure, mm Hg Diastolic blood pressure, mm Hg ESS Berlin risk (Low:High), % Snore reported, % Awakenings reported, % EDS reported, %
Diagnostic Classification Agreement Agreement Overestimation Underestimation
AHI = apnea-hypopnea index; PSG = polysomnography; STD = Stardust portable monitor.
the AHI for their population was 6. For this study, a wider range in AHI (standard deviation of 9) was chosen, and the minimum important difference in AHI was assumed to be 5. With a power of 90% and an α of 0.05, 69 participants were required. A combined dropout rate and equipment failure/data loss rate of 12% for the unattended home studies were predicted. Therefore, a minimum of 78 participants were required.
M = male; F = female; BMI = body mass index; ESS = Epworth Sleepiness Scale; EDS = excessive diurnal somnolence.
not meet exclusion criteria were included. Data from 2 participants were dropped due to incomplete recording results; one performed the STD Home and PSG lab recordings but not the STD+PSG lab recording; the other had a hypertensive crisis during the simultaneous STD+PSG lab recording. Records from 80 participants were analyzed. There were technical problems in 10 participants during the STD recordings. Two STD records were lost due to equipment malfunction in the home (data downloads were not accessible). Seven recordings had a SpO2 failure in part of the recording, and one had a poor belt signal during a portion of the recording; data from these 8 participants were included in the analysis, since more than 80% of the total recording was available. We did not find differences in the frequency of technical problems of STD devices between home and laboratory recordings. Demographic data from the entire group are shown in Table 2. No differences in sleep parameters were seen when comparing data from the PSG lab to PSG+STD lab recordings (P > 0.05). The comparison of respiratory parameters in the 4 recordings is presented in Table 3. Data comparing the 4 recordings were similar, but the lowest SpO2% from the STD+PSG lab was lower than that obtained with PSG in lab and PSG+STD lab. In addition, the correlation between AHIs from both the PSG lab and PSG+STD lab was high (r = 0.89; P < 0.005). A strong correlation was observed between STD and PSG AHI considering the 4 recordings, with all of the correlation coefficients above 0.87 (Figure 1). Sensitivity, specificity, and positive and negative predictive values (at AHI cutoff values of 5, 15, and 30 events/hour) were calculated for the AHI from PSG lab and PSG+STD lab compared to AHI from STD home and AHI from STD+PSG lab (Table 4). The sensitivity diminished and the specificity increased in direct relation with the increase of the AHI cut-off value. The corresponding positive predictive value also decreased. All values were better when PSG and STD were performed simultaneously. Diagnostic agreement, overestimation, and underestimation comparing AHI from STDs and PSGs recordings are presented in Table 5. The results illustrate the comparisons between the AHI from PSG lab vs. the AHIs from PSG+STD lab. Agree-
Statistical Analysis Demographic variables are presented with descriptive statistics (mean ± standard deviation). Data from the PSG and respiratory parameters across the AHI values from the 4 sleep evaluations (i.e., STD home, STD+PSG lab, PSG+STD lab, and PSG lab) were compared using the intra-subject ANOVA procedure. Pearson correlation coefficients were calculated for the various dependent measures. Sensitivity, specificity, and the negative and positive predictive values at AHI cut-off values of 5, 15, and 30 events/hour were calculated using the AHI values from PSG lab vs. STD Home, PSG lab vs. STD+PSG lab, PSG+STD lab vs. STD Home, and PSG+STD lab vs. STD+PSG lab. Using the same series of comparisons, Receiver Operator Curves (ROCs) were constructed to illustrate true and false positive results with AHI cut-off values of 5, 15, and 30 events/ hour. Bland-Altman plots were generated to assess agreement between the PSG and STD results. Diagnostic Agreement The rates of diagnostic agreement, over-estimation, and under-estimation were calculated by comparing AHIs from PSG lab vs. AHIs from the PSG+STD lab. In addition, the AHI obtained from PSG lab and STD+PSG lab recordings were compared to the AHI from STD Home and STD+PSG lab recordings, according to the criteria shown in Table 1. The rate of diagnostic agreement and disagreement was calculated in a manner similar to that described by White and colleagues13 with one modification: while those authors used an AHI value ≥40 as the cut-off for severe OSA in their assessment of diagnostic agreement, we used an AHI ≥ 30 as the generally accepted cut-off for severe OSA. RESULTS A total of 82 participants were recruited from the Sleep Institute. Ten participants without suspicion of OSA and who did SLEEP, Vol. 32, No. 5, 2009
47 ± 14 57:43 28 ± 5 36.6 ± 4.9 129 ± 17 85 ± 15 10.4 ± 5.8 32:68 87 86 88
631
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
Figure 1—Pearson correlation between AHIs from STDs and PSGs in the 4 recordings. A: PSG lab vs. STD Home (r = 0.876; P < 0.0001; 95% CI = 0.81 to 0.91); B: PSG lab vs. STD+PSG lab (r = 0.873; P < 0.0001; 95% CI = 0.80 to 0.91); C: PSG+STD lab vs. STD Home (r = 0.892; P < 0.0001; 95% CI = 0.83 to 0.92); D: PSG+STD lab vs. STD+PSG lab (r = 0.892; P < 0.0001; 95% CI = 0.83 to 0.93).
Table 3—Comparison of Respiratory Parameters Observed in PSG lab, PSG+STD lab, STD Home, and STD+PSG Lab Recordings (mean ± SD) AHI Apnea Index Hypopnea Index Mean SpO2, % Nadir SpO2, % Time SpO2 below 90%, min Desaturation Index, number of 3% drops in SpO2 per hour of sleep
PSG lab 23 ± 24 12 ± 19 11 ± 11 94 ± 2 83 ± 9* 22 ± 43
PSG+STD lab 26 ± 28 15 ± 22 11 ± 14 94 ± 2 82 ± 10# 25 ± 50
STD HOME 23 ± 24 13 ± 20 9 ± 6 95 ± 2 80 ± 9 21 ± 47
STD+PSG lab 27 ± 23 15 ± 20 11 ± 8 95 ± 2 78 ± 11*# 18 ± 41
P NS NS NS NS 0.01 NS
17 ± 22
20 ± 25
14 ± 19
16 ± 19
NS
PSG = polysomnography; STD = Stardust portable monitor; AHI = apnea-hypopnea index. *P = 0.002; #P = 0.01
ment was better when comparing the AHIs from the simultaneous PSG +STD lab. Using AHI cut-off values of 10, 15, and 30 events/hour, the ROC curves from STD vs. PSG during the 4 recordings are presented in Figure 2. The area under the curve was above 0.9 in all comparisons, especially when AHI was compared between the STD and PSG of the STD+PSG lab recording. The Bland Altman analyses generally showed strong agreement between AHI values from the STDs and PSGs from the SLEEP, Vol. 32, No. 5, 2009
4 recordings (Figure 3). Once again, better results were seen when AHI was compared between STD and PSG performed at the same time. An AHI > 5 was observed in 78% of the patients and 30% of the “healthy” participants. In the healthy group, ANOVA test of the AHI values showed that the AHI from STD+PSG lab (6.7) and AHI from STD Home (7.3) were higher than the AHI from PSG+STD lab (3.1) (P = 0.03 and 0.01, respectively). However, we did not find differences when values of AHI from STD 632
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
Figure 2—ROC curves of different AHI cut-offs (5, 15, and 30, columns respectively) from STDs and PSGs considering the 4 recordings. A: PSG lab vs. STD Home (AUC = 0.90, 0.92, and 0.95, respectively); B: PSG lab vs. STD+PSG lab (AUC = 0.91, 0.93, and 0.95, respectively); C: PSG+STD lab vs. STD Home (AUC = 0.95, 0.95, and 0.96, respectively); D: PSG+STD lab vs. STD+PSG lab (AUC = 0.97, 0.98, and 0.98, respectively). AUC = area under the ROC curve.
Home (7.3) were compared with AHI from PSG lab (5) and STD+PSG lab (6.7) (P = 0.26 and 0.96, respectively).
a sleep specialist physician performed an evaluation before entering into the protocol as suggested by the AASM.2 Our study was also the first to randomize participants to home and lab recordings. The sample size evaluated by other studies investigating type 3 PM recordings varied from 25 to 116.6,12-20 We believe that our sample was sufficient to analyze the accuracy of the STD. The technology used in the STD is in accordance with the AASM recommendations.2 At minimum, the PM must record airflow, respiratory effort, heart rate, and blood oxygenation.
DISCUSSION The use of the PM device (in this case, the Stardust II) was demonstrated to be useful as a tool to confirm or exclude the diagnosis of OSA in our sample. Results revealed acceptable sensitivity, specificity, and diagnostic agreement. In this study, participants came from a specific sleep outpatient setting, where SLEEP, Vol. 32, No. 5, 2009
633
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
Figure 3—Bland Altman analysis between AHIs from STDs and PSGs considering the 4 recordings. A: PSG lab vs. STD Home; B: PSG lab vs. STD+PSG lab; C: PSG+STD lab vs. STD Home; D: PSG+STD lab vs. STD+PSG lab.
Table 4—Sensitivity, Specificity, and Positive (PPV) and Negative (NPV) Predictive Value for Different Cut-Offs of AHI from the STD Home and STD+PSG lab vs. AHI from PSG lab and PSG+STD AHI ≥ 5 STD Home STD+PSG lab AHI ≥ 15 STD Home STD+PSG lab AHI ≥ 30 STD Home STD+PSG lab
Sensitivity
PSG lab Specificity PPV
NPV
Sensitivity
PSG+STD lab Specificity PPV
NPV
93 92
59 48
85 82
76 71
95 98
62 62
87 87
81 93
85 94
80 71
80 76
84 93
86 97
78 74
78 78
86 96
77 86
93 79
81 63
91 93
74 96
96 92
91 87
87 98
PSG = polysomnography; STD = Stardust portable monitor; AHI = apnea-hypopnea index.
The biosensors used to monitor these parameters in the laboratory are also recommended for use in a PM. The prior evidence review of type 3 equipment studies reported a range of 3% to 18% data loss in unattended settings.22 Our study showed only 2% data loss due to inaccessible data downloads from STD recorded at home. Our data loss rate caused by transducer problems was 10%, which is lower than rates in other studies.7,12,14,15,30,31 A respiratory effort signal and SpO2 recording problems were observed intermittently in the present study, but not frequently enough to prevent scoring respiratory events. The justification for performing 2 PSG recordings, one of them simultaneously with STD, was based on anticipated nightto-night AHI variability. The variability of sleep parameters during full night PSG, including AHI, has been presented preSLEEP, Vol. 32, No. 5, 2009
viously.26 In our study, however, the mean values of AHI did not differ between 2 full-night PSG recordings (PSG in lab and PSG+STD lab) and showed good agreement. Concerning the accuracy of STD, the diagnostic agreement, sensitivity, specificity, positive and negative predictive values, and area under ROC curves, analyses were better when AHI was compared between STD and PSG of the STD+PSG lab conducted simultaneously. Less variability was expected from the acquisition of data from 2 systems run simultaneously than from those run on different nights. Previous studies comparing simultaneous type 3 PM in home and in-laboratory PSG showed similar agreement in diagnoses of OSA.13-20 Regarding the night-to-night variability of PM devices, one prior unattended home study reported no significant difference in AHI between 2 nights.14 We also did 634
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
Table 5—Diagnostic Agreement, Overestimation, and Underestimation Among AHI from PSG lab and PSG+STD lab vs. AHI from STD Home and STD+PSG lab Diagnostic agreement (%) Overestimation of AHI (%) Understimation of AHI (%)
PSG lab vs. PSG+STD lab 88 7 5
PSG lab vs. STD Home 83 10 7
PSG lab vs. STD+PSG lab 75 20 5
PSG+STD lab vs. PSG+STD lab vs. STD Home STD+PSG lab 87 91 6.5 8 6.5 1
PSG = polysomnography; STD = Stardust portable monitor; AHI = apnea-hypopnea index
not find significant differences between the AHI from the STD home night and the AHI from the STD recorded simultaneously with PSG in lab. Our data showed good performance of the STD compared to PSG between mild, moderate, and severe AHI ranges. Better accuracy of the STD was observed in severe cases, as seen in the area under ROC curves analyses. However, our results showed that some symptomatic patients had a negative PM study. As suggested for practice parameters by the ASDA,3 we agree that those patients must be reevaluated using full-night attended PSG. Our original hypothesis was that STD could present a lower AHI, since respiratory events associated with EEG arousal only (but not with arterial desaturation) would not be scored. However, in our study, the mean values for AHI among the 4 recordings (from STD Home, from STD+PSG lab, from PSG+STD lab, and from PSG lab) did not show significant differences. Only the nadir SpO2 from STD of the STD+PSG night was lower than the other recordings, possibly reflecting the differences between oximeter equipment technologies (i.e., Respironics vs. Medcare), sampling rate, or analytical software. Until 2005, AASM recommendations for using PMs were to use them under supervision.33,34 Recently, unattended recordings have been deemed acceptable.2 Our results demonstrated that the Stardust II, attended by a technician or unattended in home, has strong sensitivity and specificity, compared with traditional PSG. Yin and colleagues30 evaluated the STD, considering only the discomfort, difficulty of applying the various sensors, and operation of the device. In that study, the authors did not compare PM results with PSG but did evaluate the automated and manual scoring of respiratory events. They suggested that the data analysis should be performed manually and that the discomfort score was low. In another study, Yin and colleagues7 evaluated the reliability of STD in OSA patients compared with PSG. The sensitivity, specificity, NPV, and PPV presented were similar to our findings, but they performed PSG only in part of their patient population and did not compare results to a simultaneous PSG. Recent emphasis has been placed upon the utility of a PM device in the clinical context of OSA.2 Based on our results, we believe that PM devices could be used in patients with a high suspicion of OSA when full-night PSG is not available. More studies evaluating of the cost-effectiveness of PM in the diagnosis and treatment of OSA are necessary. Alonso-Alvarez and colleagues35 carried out a cost analysis using a diagnostic algorithm that included home PSG. They took into account not SLEEP, Vol. 32, No. 5, 2009
only the costs of the necessary disposable accessories but also the costs of the time taken by medical personnel and sleep center staff. In that study, home PSG represented a savings of only 18% compared with traditional attended, in-laboratory PSG. Mulgrew and colleagues36 evaluated the diagnosis and initial management of OSA by comparing PSG with the AHI from auto-CPAP and overnight oximetry. They showed that PSG confers no advantage over the ambulatory approach in terms of OSA diagnosis and management. However, we believe that the use of PM + auto CPAP approach without a previous diagnosis increases the chance of treating patients without OSA. Future research evaluating PM is needed, such as larger-scale validation studies in patients with lower pre-test probabilities and in patients with comorbidities. Validation of PM diagnostic reliability in elderly populations is also warranted. In summary, the Stardust II device provides AHI results that are in diagnostic agreement with those determined from conventional, attended full night PSG. There was a lower than expected rate of technical failure and successful use by patients in the home setting. These data demonstrated that the Stardust II device is a reliable tool for diagnosing patients referred for evaluation of OSA. Acknowledgments Financial Support: Associacao Fundo de Incentivo a Psicofarmacologia (AFIP); Respironics (The manufacturer of the Stardust provided the devices and training on the operation of the devices and the host software in addition to providing financial support for this research. The investigators were solely responsible for all aspects of participant recruitment, protocol adherence, randomization, data collection, and data analysis). Disclosure Statement Respironics provided free use of six portable monitoring systems for this study. The authors have indicated no other conflicts of interest. REFERENCES 1. 2.
635
Kushida CA, Littner MR, Morgenthaler T, et al. Practice parameters for the indications for polysomnography and related procedures: An update for 2005. Sleep 2005;28:499-521. Collop NA, Anderson WM, Boehlecke B, et al. Portable Monitoring Task Force of the American Academy of Sleep Medicine. Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. Portable Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
3. 4.
5.
6.
7.
8.
9. 10. 11.
12. 13. 14. 15.
16. 17. 18. 19. 20.
Monitoring Task Force of the American Academy of Sleep Medicine. J Clin Sleep Med 2007;3:737-47. American Sleep Disorders Association. Practice parameters for use of portable recording in the assessment of obstructive sleep apnea. Sleep 1994;17:372-77. Schäfer H, Ewig S, Hasper E, Lüderitz B. Predictive diagnostic value of clinical assessment and non laboratory monitoring system recordings in patients with symptoms suggestive of obstructive sleep apnea syndrome. Respiration 1997;64:194-9. Westbrook PR, Levendowski DJ, Cvetinovic M, et al. Description and validation of the apnea risk evaluation system: a novel method to diagnose sleep apnea-hypopnea in the home. Chest 2005;128:2166-75. Parra O, García-Esclasans N, Montserrat JM, et al. Should patients with sleep apnoea/hypopnoea syndrome be diagnosed and managed on the basis of home sleep studies? Eur Respir J 1997;10:1720-4. Yin M, Miyazaki S, Ishikawa K. Evaluation of type 3 portable monitoring in unattended home setting for suspected sleep apnea: factors that may affect its accuracy. Otolaryngol Head Neck Surg 2006;134:204-9. Zou D, Grote L, Peker Y, Lindblad U, Hedner J. Validation a portable monitoring device for sleep apnea diagnosis in a population based cohort using synchronized home polysomnography. Sleep 2006;29:367-74. Ayappa I, Norman RG, Seelall V, Rapoport DM. Validation of a self-applied unattended monitor for sleep disordered breathing. J Clin Sleep Med 2008;4:26-37. Penzel T, Kesper K, Pinnow I, Becker HF, Vogelmeter C. Peripheral arterial tonometry oximetry and actigraphy for ambulatory recording of sleep apnea. Physiol Meas 2004;25:1025-36. Øverland B, Bruskeland G, Akre H, Skatvedt O. Evaluation of a portable recording device (Reggie) with actimeter and nasopharyngeal/esophagus catheter incorporated. Respiration 2005;72:600-5. Man GC, Kang BV. Validation of a portable sleep apnea monitoring device. Chest 1995;108:388-93. White DP, Gibb TJ, Wall JM, Westbrook PR. Assessment of accuracy and analysis time of a novel device to monitor sleep and breathing in the home. Sleep 1995;18:115-26. Dingli K, Coleman EL, Vennelle M, et al. Evaluation of a portable device for diagnosing the sleep apnoea/hypopnoea syndrome. Eur Respir J 2003;21:253-9. Ballester E, Solans M, Vila X, et al. Evaluation of a portable respiratory recording device for detecting apnoeas and hypopnoeas in participants from a general population. Eur Respir J 2000;16:123-7. Candela A, Hernández L, Asensio S, et al. Validation of a respiratory polygraphy system in the diagnosis of sleep apnea syndrome. Arch Bronconeumol 2005;41:71-7. Calleja JM, Esnaola S, Rubio R, Durán J. Comparison of a cardiorespiratory device versus polysomnography for diagnosis of sleep apnoea. Eur Respir J 2002;20:1505-10. Verse T, Pirsig W, Junge-Hülsing B, Kroker B. Validation of the POLY-MESAM seven-channel ambulatory recording unit. Chest 2000;117:1613-8. Reichert JA, Bloch DA, Cundiff E, Votteri BA. Comparison of the NovaSom QSG, a new sleep apnea home-diagnostic system, and polysomnography. Sleep Med 2003;4:213-8. Claman D, Murr A, Trotter K. Clinical validation of the Bedbugg
SLEEP, Vol. 32, No. 5, 2009
21.
22.
23.
24.
25. 26. 27.
28.
29. 30. 31. 32. 33. 34. 35.
36.
636
in detection of obstructive sleep apnea. Otolaryngol Head Neck Surg 2001;125:227-30. Chesson Jr AL, Berry RB, Pack A. Practice parameters for the use of portable monitoring devices in the investigation of suspected obstructive sleep apnea in adults. A joint project sponsored by the American Academy of Sleep Medicine, the American Thoracic Society, and the American College of Chest Physicians. Sleep 2003;26:907-13 Flemons WW, Littner MR, Rowley JA, et al. Home diagnosis of sleep apnea: a systematic review of the literature. An evidence re view cosponsored by the American Academy of Sleep Medicine, the American College of Chest Physicians, and the American Thoracic Society. Chest 2003;124:1543-79. Decision Memo for Continuous Positive Airway Pressure (CPAP) Therapy for Obstructive Sleep Apnea (OSA) (CAG-00093R). 2005. Accessed at http://www.cms.hhs.gov/MLNMattersArticles/ downloads/MM3843.pdf on 15 June 2008. Centers for Medicare & Medicaid Services. Proposed Decision memo for Continuous Positive Airway Pressure (CPAP) Therapy for Obstructive Sleep Apnea (OSA) 2007. Accessed at https://www.cms.hhs.gov/scripts/ctredirector.dll/.pdf?@_ CPR0a0a043a07d1.XV_RZ02_FB54 on 15 June 2008. Netzer NC, Stoohs RA, Netzer CM, Clark K, Strohl KP. Using the Berlin Questionnaire to identify patients at risk for the sleep apnea syndrome. Am Intern Med 1999;131:485-91. Johns MW. A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep 1991;14:540-5. Rechtschaffen A, Kales A, eds. A manual of standardized terminology, techniques, and scoring systems for sleep stages of human participants. Los Angeles: Brain Information/Brain Research Institute UCLA, 1968. American Academy of Sleep Medicine Task Force. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. Sleep 1999;22:667-89. American Sleep Disorders Association. EEG arousals: scoring rules and examples - Atlas Task Force. Sleep 1992;15:174-82. Yin M, Miyazaki S, Itasaka Y, et al. A preliminary study on application of portable monitoring for diagnosis of obstructive sleep apnea. Auris Nasus Larynx 2005;32:151-6. Metersky ML, Castriotta RJ. The effect of polysomnography on sleep position: possible implications on the diagnosis of positional obstructive sleep apnea. Respiration 1996;63:283-7. Bittencourt LR, Suchecki D, Tufik S, et al. The variability of the apnoea-hypopnoea index. J Sleep Res 2001;10:245-51. American Academy of Sleep Medicine. Portable monitoring in the diagnosis of obstructive sleep apnea. J Clin Sleep Med 2006;2:274. Littner MR. Portable monitoring in the diagnosis of the obstructive sleep apnea syndrome. Semin Respir Crit Care Med 2005;26:56-67. Alonso Alvarez Mde L, Terán Santos J, Cordero Guevara J, et al. Reliability of home respiratory polygraphy for the diagnosis of sleep apnea-hypopnea syndrome: analysis of costs. Arch Bronconeumol 2008;44:22-8. Mulgrew AT, Fox N, Ayas NT, Ryan CF. Diagnosis and initial management of obstructive sleep apnea without polysomnography: a randomized validation study. Ann Intern Med 2007;146:157-66.
Portable Device for Sleep Apnea Diagnosis—Santos-Silva et al
