THE IMPACT OF SPLIT-NIGHT POLYSOMNOGRAPHY

THE IMPACT OF SPLIT-NIGHT POLYSOMNOGRAPHY The Impact of Split-Night Polysomnography for Diagnosis and Positive Pressure Therapy Titration on Treatment Acceptance and Adherence in Sleep Apnea/Hypopnea Mark H. Sanders MD, 1 Joseph P. Costantino PhD, 2 Patrick J. Strollo, Jr. MD, 3 Karen Studnicki RPsgT, CRTT, 4 Charles W. Atwood, Jr. MD 5 1 Professor of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Veterans Affairs Pittsburgh Healthcare System, 2 Professor of Biostatistics, University of Pittsburgh Graduate School of Public Health, 3 Associate Professor of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, 4 Lead Technologist, Pulmonary Sleep Evaluation Center, University of Pittsburgh Medical Center, 5 Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Veterans Affairs Pittsburgh Healthcare System Study Objectives: The time and resource intensive nature of the traditional two-night paradigm for diagnosing and titrating positive pressure therapy for Obstructive Sleep Apnea/Hypopnea (OSA/H) contributes to patient care cost and limitation of service availability. Although split night polysomography (PSG SN ) algorithms can establish a diagnosis of OSA/H and establish a positive pressure prescription for many patients, there has been only limited evidence that this strategy does not impair acceptance and adherence to treatment. The objective of this study was to test the null hypothesis that PSG SN does not adversely impact acceptance and adherence to positive pressure therapy for OSA/H compared with a standard two-night PSG strategy (PSG TN ). Design: Retrospective case-controlled study. Setting: University-based sleep disorders program Patients: Both PSG SN and PSG TN (control) patients were selected on the basis of having an initial medical/sleep evaluation by a full-time physician member of the University of Pittsburgh Sleep Disorders Program, must not have had prior diagnostic PSG or treatment for sleepdisordered breathing, and must have been followed by the Sleep Program team. Selection of PSG SN patients required the ability to be matched with a control patient. Both groups underwent evaluation during the same time period. Of 146 patients who underwent PSG SN between October 1995 and September 1997, 51 had their initial evaluation and subsequent follow-up by physician-staff members of our Program. Of these, 15 were excluded from analysis because of a previous diagnostic PSG's or prior OSA/H therapy. Also, matches were unavailable for 5 patients. Seven patients refusal to use positive pressure at home and were not available for assessment of adherence, but were included in analysis of therapeutic acceptance. Thus, analysis of the impact of PSG SN on adherence to positive pressure therapy was based on a data set of 24 patients in whom a PSG SN was performed and 24 patients who had PSG TN. The two groups were matched for age, Apnea+Hypopnea Index (AHI) and gender. Measurement and Results: There were no significant differences between the PSG SN and PSG TN groups with respect to age, body mass index (BMI), Desaturation Event Frequency (DEF), Arousal Index (ArI) or the Epworth Sleepiness Score (ESS). The nadir of oxyhemoglobin saturation (SpO2) during sleep was lower in the PSG TN than PSG SN group (69.3±15 vs. 79.8±9, mean±sd, p=0.012). During positive pressure titration, the time spent at the final pressure which was prescribed for the patients were comparable in both groups (123.4±64 vs. 161±96 minutes, PSG SN and PSG TN, respectively, p=0.17). Adherence to therapy was objectively assessed by the average daily run-time of the positive pressure device at the first meter-read following initiation of treatment (55.1±44 vs. 40.8±16 days following home set-up, PSG SN and PSG TN, respectively, p=0.14). Depending whether or not patients with previous exposure to positive pressure therapy were included in the analysis, 84-86% of patients undergoing PSG SN accepted therapy. There was no difference between the groups with respect to adherence (5.1±4 vs. 4.6±3 hours, PSG SN and PSG TN, respectively, p=0.64). Conclusions: In a population of predominantly moderate-to-severe OSA/H patients, PSG SN strategy does not adversely impact on adherence to positive pressure therapy over the first six weeks of treatment. Acceptance of therapy is comparable to that reported in the literature following PSG TN. Key words: Sleep apnea; positive pressure therapy; polysomnography; sleep-disordered breathing Accepted for publication October 1999 Address correspondence to: Mark H. Sanders, MD, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, University of Pittsburgh Medical Center, Montefiore University Hospital, Suite S-643, 3459 Fifth Avenue, Pittsburgh, PA 15213 SLEEP, Vol. 23, No. 1, 2000 17

INTRODUCTION SLEEP, Vol. 23, No. 1, 2000 18 THE HUMAN, HEALTH CARE, AND SOCIETAL COSTS OF SLEEP APNEA/HYPOPNEA ARE SUB- STANTIAL. The yearly cost of sleep disorders associated with reduced productivity from all causes has been estimated at $18 billion dollars. 1 A recent study revealed that health care costs of undiagnosed Obstructive Sleep Apnea/Hypopnea (OSA/H) are approximately twice those of a control population. 2 The investigators suggested that earlier diagnosis and treatment might limit medical costs by reducing subsequent utilization of health care services. It is self-evident however, that the diagnostic process of polysomnography (PSG) itself entails monetary costs as well as potential for lost patient productivity associated with travel to, and stay in, a facility with resources to perform this assessment. The magnitude of this burden must also be viewed in light of recent information indicating that 93% and 82% of middle-aged women and men, respectively, with moderate to severe sleep apnea remain undiagnosed. 3 The financial burden of full-night, in-laboratory diagnostic PSG is accentuated not only by its time and hardware intensity, but also by the mandate for attendance by highly trained personnel. These latter requisites also contribute to limited availability of services with consequent patient waiting lists and delays in diagnosis. A number of alternative strategies have been suggested and variably implemented to address these issues, including both full PSG and limited-variable recordings in the home environment. 4-11 The diagnostic reliability and cost-saving potential of these approaches remain controversial. Additionally, they do not address the issue of expediting initiation of treatment. Continuous positive airway pressure (CPAP) is generally considered to be the non-surgical therapy of choice for OSA/H. Some authors have advocated home titration of positive pressure therapy for Obstructive Sleep Apnea/Hypopnea (OSA/H), employing either manual adjustment by a responsible party 4,12 or recently developed automated titration algorithms incorporated into continuous positive airway pressure (CPAP) devices. 13-25 It is evident that manual home CPAP titration is not feasible for many patients and the appropriate role of auto-titrating CPAP devices is still being defined. Combining diagnostic and treatment efforts into a onenight (split-night) session in the sleep laboratory reflects an alternative strategy to reduce health care costs and patient inconvenience. Previous studies have demonstrated a high positive, but sub-optimal negative predictive power for OSA/H on the basis of a partial-night PSG. 26-29 On this basis, it may be reasonable to initiate a trial of positive pressure therapy during the latter portion of the night, after a diagnosis of OSA/H has been established. 30,31 Indeed, a recent informal survey by the American College of Chest Physicians indicated that most sleep centers perform splitnight PSG although there is non-uniformity of indications and uncertainty regarding efficacy. 32 An important component of this uncertainty is concern that patient acceptance/adherence of CPAP therapy will be adversely affected. 33-44 To date, the comprehensive impact of split-night PSG (PSG SN ) on treatment efficacy, defined as amelioration of sleep-disordered breathing as well as patient acceptance of and subsequent adherence to treatment, has not been thoroughly evaluated. Some investigators have noted that an adequate positive pressure prescription cannot be identified in some patients on the basis of less than a full night titration 31,45 and conceivably, without attention to this issue, acceptance and adherence may suffer. In a prospective but uncontrolled study, Fleury et al. observed that 16 of 27 patients who had a successful partial-night CPAP titration were adherent with therapy after an average of 285 days. 46 In a subsequent small case-control study we noted no statistical difference in average daily CPAP use between patients who had initiation of CPAP following a split-night compared with a full-night titration (3.8±2.9 vs. 5.2±2.2 hours/day, mean±sd, respectively). 47 We were concerned however that the absence of a statistically significant difference was a reflection of the small sample size. We now report the results of a second, larger case-controlled study of a different data set to test the null hypothesis that a splitnight diagnostic/therapeutic paradigm does not adversely influence adherence to positive pressure therapy for OSA/H. METHODS Inclusion in this analysis required that patients had an initial medical evaluation and sleep history obtained evaluation by a full-time physician staff member of the University of Pittsburgh Sleep Disorders Program. In addition, patients must not have had prior diagnostic PSG or treatment for sleep-disordered breathing. Patients who had a split-night paradigm (PSG SN ) were those for whom the physician ordered diagnostic PSG with instructions for the technologist to initiate titration of positive pressure therapy if a diagnosis of OSA/H was evident during the first portion of the night (>30 apneas + hypopneas). Inclusion of a PSG SN patient also required that follow-up was by the Sleep Program team as well as the ability to be matched with a patient who followed a traditional two-night paradigm PSG TN. Selection of control patients was based on the same criteria with the exception that they had been ordered to have a full night of diagnostic PSG with a subsequent fullnight positive pressure titration if indicated by the results of the diagnostic study (the two-night PSG strategy, PSG TN ). Between October 1995 and September 1997, 173 patients underwent nocturnal PSG in the Pulmonary Sleep Evaluation Laboratory at the University of Pittsburgh Medical Center with physician orders indicating that a

split-night diagnostic/therapeutic regimen be followed if the criteria described above were met. The decision to order the option for a split-night study was at the discretion of that physician based on the clinical perception of OSA/H severity and logistic issues related to laboratory availability. Of the 173 patients, 146 actually underwent a split-night diagnostic/therapeutic paradigm. Fifty-one of these patients had undergone both an initial clinical evaluation and subsequent follow-up by the physician staff at our program. Of this population, nine individuals had undergone a previous diagnostic PSG, six had received treatment for OSA/H prior to the split-night PSG, and seven refused to use positive airway pressure therapy. In five patients, we were unable to find a suitably matched individual (see below) who had a traditional two-night diagnostic and therapeutic regimen. Thus, the study group consisted of 24 patients who underwent split-night and 24 matched patients who underwent a two-night algorithm. Our goal was to match patients to within ±10 years of age and an Apnea+Hypopnea Index (AHI) within ±5, as well as gender. We were successful in these efforts in all but three patients in whom age was matched to within ±11-16 years and four patients in whom AHI was matched to within ±5-10 (Table 1). All patients completed an Epworth Sleepiness Scale 48 at this time as part of their routine care at the time of their initial medical evaluation. Diagnostic PSG was performed employing standard electroencephalogram, electrooculogram and submental electromyogram recording; 49 airflow was recorded at the nose by nasal pressure transduction 50,51 and at the mouth by thermistor; breathing efforts were recorded by qualitative inductance plethysmography (Respitrace, SensorMedics, Inc. CA); oxyhemoglobin saturation (SpO 2 ) was monitored by finger pulse oximetry Table 1 Comparison of Baseline and Diagnostic Features of the Study Groups PSG SN (n=24) PSG TN (n=24) p value Age, years 48.2 ± 12 50.5 ± 10 0.14 BMI ƒ 40.9 ± 10 41.3 ± 12 0.89 Epworth Score φ 15.2 ± 5 12.7 ± 7 0.07 AHI α 66.1 ± 32 65.1 ±33 0.54 DEF χ 30 ± 30 31.2 ± 35 0.87 ArI Ψ 44 ± 26 43.1 ± 27 0.8 Nadir, S p O 2 (%) 79.8 ± 9 69.3 ± 15 0.012 (Ohmeda model 3700, Boulder CO); and the electrocardiogram was recorded using modified chest leads. CPAP was initiated using a BiPAP STD Ventilatory System (Respironics, Inc. Murrysville PA) employing the patient's interface of choice. Pressure was titrated in 2.5 cmh 2 0 increments to eliminate apneas, and one cmh 2 0 increments to eliminate hypopneas, oxyhemoglobin desaturation, and respiratory event-related arousals. Sleep was scored by the method of Rechtschaffen and Kales. 49 Apneas were defined by an absence of inspiratory airflow for >10 seconds and a hypopnea was defined as a reduction in airflow by >30% from baseline. A desaturation event was identified when there was a reduction in SpO 2 by >5% and arousals were defined according to the American Academy of Sleep Medicine criteria. 52 The Apnea + Hypopnea Index (AHI) is the average number of apneas plus hypopneas per hour of sleep, the Arousal Index (ArI) is the average number of arousals per hour of sleep and the Desaturation Event Frequency (DEF) is the average number of desaturations >5% per hour of sleep. CPAP was changed to bi-level positive airway pressure (BPAP) in the event that the patient was intolerant of CPAP (e.g., discomfort related to the level of pressure). It is our practice to inform all patients who are potential candidates for a split-night algorithm that they may be awakened at some time during the study for initiation of positive pressure therapy titration. On the night of PSG, patients view an educational video relating to the diagnosis and treatment of OSA/H. Prior to bedtime, the they are provided with an opportunity to try the various positive pressure interfaces in order to optimize fit and that they may select the one of their choice should therapeutic adminis- ƒ = BMI, body mass index (weight, kg/height, m 2 ) φ = Score on the Epworth Sleepiness Scale α = Apnea + Hypopnea Index, average number of apneas + hypopneas per hour of sleep χ = Desaturation Event Frequency, average number of desaturations >4% per hour of sleep Ψ = Arousal Index, average number of arousals/hour of sleep = value on the diagnostic PSG Figure 1 Distribution of Apnea + Hypopnea Indices in PSG SN Groups. and PSG TN SLEEP, Vol. 23, No. 1, 2000 19

tration of positive pressure be indicated. This interface may be changed during the study, and/or a chin-strap added at the patient's request or to address problems related to suboptimal function. Acceptance of positive pressure therapy was defined as willingness to initiate positive pressure therapy at home. Adherence was objectively determined as the average number of hours of positive pressure device run time per day, read from the hour meter incorporated into the prescribed machines. Data was taken from the first meter-reading after treatment was prescribed. The readings were either obtained from the home care company personnel or during a scheduled follow-up visit to the Pulmonary Sleep Evaluation Center, whichever came first. As consistent with our clinical practice, the attempts were not made to hide the existence of the meter from the patients but neither were they deliberately informed in this regard as part of the clinical protocol. STATISTICAL ANALYSES Differences between groups with regard to mean values were assessed by paired t-test. Linear regression analyses were performed to determine if various parameters predicted adherence to treatment among the entire study population of 48 patients. For all testing, results were determined to be statistically significant if the p-value was <0.05. Two patients, one in each of the PSGTN and PSGSN groups accepted therapy following titration, and took a Table 2 Comparison of Impact of Positive Pressure Therapy in the Two Study Groups PSG SN (n=24) PSG TN (n=24) p value AHI 9.3 ± 11 9.0 ± 12 0.96 DEF 1.0 ± 2 1.0 ± 2 1 Nadir, S p O 2 (%) 89.7 ± 3 89.6 ±4 0.94 ArI 10.71 ± 9.3 9.4 ± 8.6 0.6 # Days until 1st 55.1 ± 44 40.8 ± 16 0.14 meter reading Average daily 5.1 ± 4 4.6 ± 3 0.64 hours of use, all patients Average daily 4.84 ± 3.9 4.76 ± 3 0.96 hours of use, (n=18) (n=18) CPAP patientsψ = During application of positive pressure therapy = Comparing all patients (CPAP and BPAP) in each group Ψ = Comparing only patients prescribed to receive CPAP in each group CPAP device home and were noted to have zero use time on a meter reading 30 days later. Adherence to therapy was noted as zero hours/day and included in the analysis on an intent-to-treat basis. Data are presented as the mean±standard deviation (SD). The Institutional Review Board of the University of Pittsburgh approved this study protocol. RESULTS There was no significant difference between the patients who underwent a split-night algorithm (PSG SN ) and those who underwent a traditional two-night diagnosis and positive pressure titration protocol (PSG TN ) with respect to age, body mass index (weight in kg/height in meters 2 ), AHI, DEF, Epworth score, or the ArI (Table 1). Although notable oxyhemoglobin desaturation was recorded during the diagnostic PSG in both groups, the nadir of SpO 2 was significantly lower in the patients in the PSG TN group. Although the mean duration on final levels of titrated pressure was less in the PSG SN group, the difference was not significant (123.4±64 versus 161±96 minutes, PSG SN and PSG TN, respectively, p=0.17). This may be related to the relatively severe OSA/H in the PSG SN population, which permitted more rapid diagnosis leaving more time for titration. 45 Patient acceptance of positive pressure therapy was examined in two ways. Evaluation of all 51 patients whose care was managed by the staff of the Pulmonary Sleep Evaluation Center, including the six individuals who had previous exposure to this therapeutic modality, acceptance following PSG SN was 86%. After excluding the population with prior exposure from this data set, 84% of patients accepted this therapy. Eighteen of the 24 patients in the PSG SN group were prescribed CPAP (11.5±3.8 cm H20). The remaining six patients in this group were prescribed BPAP (inspiratory positive airway pressure: 12±3.3 cm H 2 0, expiratory positive airway pressure: 8±2.4 cm H 2 0). All 24 patients in the PSGTN group were prescribed CPAP (11.9±3.5 cm H 2 0). Specific comparison of matched pairs of individuals who received CPAP in the PSG TN and PSG SN, revealed no significant difference in the prescribed pressure levels (11.5± 3.8 cm H 2 0 vs. 12.2±3.5 cm H 2 0, 18 PSGSN who received CPAP and the 18 matched PSGTN patients who also received CPAP, respectively, p=0.61). The two study populations achieved comparable control of OSA/H on the final titrated positive pressure therapy (Table 2). Twenty-one of the 24 PSG SN patients and 22 of the 24 PSG TN patients had rapid eye movement (REM) sleep recorded while they were receiving the final titrated positive pressure level in the laboratory. Although the average time in REM sleep was lower in the PSG SN group, the dif- SLEEP, Vol. 23, No. 1, 2000 20

ference was not statistically significant (29.38±25.2 minutes vs. 43.21±48.03 minutes, PSG SN and PSG TN, respectively, p=0.28). The impact of therapy in the two study groups is summarized in Table 2. There was no significant difference between the two groups with respect to the interval between initiation of positive pressure therapy and the first meter reading (55.1±44 days in the PSG SN group and 40.8±16 in the PSG TN group, p=0.14). Similarly, there was no significant difference in the average daily use of positive pressure therapy (5.1±4 hours vs. 4.6±3 hours, PSG SN and PSG TN, respectively, p=0.64) at the time of the first meterreading. Comparison of adherence exclusively between those patients in PSG SN and PSG TN who were prescribed to receive CPAP revealed no difference (Table 2). The relationships between adherence to positive pressure therapy and potentially influential variables were examined across the entire study population (Table 3, n= 48). There were no significant relationships between baseline objective measures of breathing during sleep, baseline sleep fragmentation, or changes in these variables during administration of positive pressure and the number of hours per day that patients used therapy at home (Table 2). DISCUSSION As health care providers and related organizations have been increasingly successful in heightening public awareness of the prevalence and consequences of OSA/H, the challenge to provide expedient and less costly care while maintaining high quality has increased. One strategy that has been proposed to address these multiple mandates is combining the objective diagnostic assessment and initiation of therapy into a single night, replacing the traditional two-night paradigm. To be successful, the split-night strategy requires that OSA/H patients be accurately identified and that all aspects associated with establishing effective treatment be implemented within the finite period of sleep during one night. We and others have previously demonstrated that a positive diagnosis of OSA/H can be made during less than a full night evaluation or during a relatively brief diurnal sleep study. 26,27,53 To realize benefit from the abbreviated amount of time devoted to establishing the diagnosis of OSA/H during PSG SN, treatment must be started on the same night. Conceptually, positive pressure therapy is ideally suited for this purpose being universally available, easily adjusted according to objective criteria and, provided that sufficiently high pressure is administrated, can almost always stabilize the upper airway during sleep. Earlier studies have showed that the technical task of establishing an effective positive pressure prescription can be successfully determined or nearly approximated during a partial night titration. 30,31 Yamashiro et al. 45 extended this observation by noting that the shorter the diagnostic portion of the PSG, and conversely the longer the therapeutic trial, the greater the likelihood of defining a satisfactory positive pressure prescription. These successes notwithstanding, the impact of the split-night strategy on patient acceptance and adherence to treatment has received limited evaluation. In the current study, acceptance of positive pressure after a split-night PSG, was approximately 85%. This figure is comparable those reported from other studies reporting acceptance following a traditional, full-night titration. 37,46,47,54,55 We were also reassured by the similar adherence to positive pressure therapy after approximately six weeks between those individuals who underwent a splitnight and those who had a two-night paradigm. In as much as patterns of adherence appear to be established soon after commencing therapy, 44 it is likely that the measurements in our study reflect a stable degree of use. Despite extensive investigation, little is known with certainty regarding the factors that determine adherence. Although it appears that baseline subjective sleepiness, per- Table 3 Relationship Between Hours/Day of Positive Pressure Therapy (Dependent Variable) and Other Factors Across the Entire Study Population (n=48) Independent Coefficient of p value Variable Variation (r 2 ) Age, years* <0.01 0.72 Epworth 0.06 0.09 Sleepiness Score AHI DX ** 0.04 0.19 AHI from D x 0.06 0.11 PSG to Positive Pressure Trial Nadir, S p O 2 (%)* <0.01 0.95 ArI DX Ψ <0.01 0.98 ArI from D x 0.01 0.77 PSG to Positive Pressure Trial ~ # Days Until 1st 0.07 0.08 Meter Reading Time On Final 0.01 0.45 Pressure During Titration * = Lowest oxyhemoglobin saturation recorded during diagnostic PSG ** = AHI during diagnostic PSG Ψ = Arousal Index, average number of arousals/hour of sleep ~ = AHI or ArI on the diagnostic PSG minus the respective value on final level of positive pressure SLEEP, Vol. 23, No. 1, 2000 21

SLEEP, Vol. 23, No. 1, 2000 22 ception of impairment and perhaps some side effects are contributing elements, 35-38,42,43,56-59 it is likely that the answer is more complex. Our study was not designed to resolve this issue but like others, we found no compelling evidence to support existence of a predominantly influential objective factor. Although it may influence the ability to develop a positive pressure prescription, we reinforced our previous impression 47 that the amount of time spent on final pressure during the therapeutic titration does not predict adherence. Our results must be interpreted in light of several factors. In view of the retrospective nature of this study, an element of selection bias of the PSG SN patients cannot be definitively excluded. The study cohort was under the care of a practice group that is heavily time, training and resource invested in pulmonary sleep medicine. Many factors are considered in deciding if a patient is a candidate for a split-night study provided certain objective criteria are met during the diagnostic recording. These factors include relative severity of symptoms and logistical factors such as laboratory and patient schedules as well as distance from the laboratory. That our PSG SN and PSG TN patients were reasonably well-matched with respect to baseline characteristics makes it less likely that bias was present based on disease severity. We do not consciously consider the likelihood of acceptance and compliance as determinants of split-night candidacy and although we believe it is improbable that our data set was biased in this regard, the possibility should be considered. Sleep laboratory personnel at our facility have considerable training and experience in providing the educational and technical skills that may enhance adherence to therapy. Although in general, the PSG SN and PSG TN groups were closely matched with regard to pre-treatment severity of OSA/H by most standard measures of comparison, we are unable to exclude the possibility that the degree of OSA/H in the former study group was under-estimated by the diagnostic evaluation exclusively during the first portion of the night. 28 Along these lines, the lower nadir of SpO 2 in the PSG TN group may have been related to increased time in rapid eye movement (REM) sleep associated with the longer diagnostic recording time and the tendency for greater desaturation in that stage. 60 It is clear that, on average, both groups had notable sleep-disordered breathing. In addition, there was no statistically significant difference in the Epworth scores of the two groups suggesting that the functional impact on sleepiness was comparable. It is important to acknowledge that in view of the substantial OSA/H and subjective behavioral sleepiness as reflected by the Epworth score in the study groups, it might not be possible to extrapolate our observations to populations of different severity. There was a wide range of AHI's (Figure 1) and, as noted above, there was no significant relationship between any measures of OSA/H severity and adherence. Others also have found little or no relationship between AHI and CPAP adherence. 34,39,40,61 Finally, during the titration period both the PSG SN and PSG TN groups had similar sleep durations at the final pressure. Although differences in time at final pressure may influence adequacy of the positive pressure prescription, 45 it has not been previously demonstrated to alter subsequent adherence. There was no relationship between this duration and adherence to therapy in either our previous study 47 and this is reinforced in the current, larger data set. 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