External proficiency testing improves inter-scorer reliability of polysomnography scoring.

PURPOSE: This study evaluated whether or not polysomnography (PSG) inter-scorer reliability (ISR) across sleep centres could be improved by external proficiency testing (EPT), or by EPT combined with method alignment training. METHODS: Experienced scorers form 15 sleep centres were randomised to the following: (1) a control group, (2) a group that received a self-directed intervention of EPT reports (EPTPassive) or (3) a group that received an active intervention of method alignment training and EPT reports (EPTActive). Respiratory, arousal and sleep scoring ISR from sixteen PSG fragments were compared between groups across time. RESULTS: Among 30 scorers, there were no ISR changes in controls between baseline (BL) and 6 months (6 m). Both EPT groups showed ISR improvement from BL to 6 m for respiratory, arousal and sleep scoring (p < 0.05). Respiratory scoring back-transformed mean (95CI) proportion of specific agreement (PSA) for the EPTPassive group improved from 0.78 (0.72-0.84) to 0.80 (0.74-0.86) and for the EPTActive group from 0.80 (0.74-0.85) to 0.82 (0.76-0.88). Arousal scoring PSA for the EPTPassive group improved from 0.72 (0.66-0.77) to 0.74 (0.69-0.79) and for the EPTActive group from 0.71 (0.65-0.76) to 0.77 (0.72-0.82). Sleep scoring kappa for the EPTPassive group improved from 0.64 (0.58-0.69) to 0.73 (0.68-0.77) and for the EPTActive group from = 0.75 (0.71-0.80) to 0.80 (0.76-0.85). Overall, poorer performers achieved greater improvement. CONCLUSION: External proficiency testing produced modest, statistically significant PSG inter-scorer reliability improvements among experienced scorers across sleep centres, with potential to improve clinical management of individual patients and increase research study statistical power.

Obstetric outcomes among women with a liver transplant.

BACKGROUND: Women with liver transplants may be at increased risk for adverse outcomes. OBJECTIVE: The objectives of this study were to evaluate trends and provide recent data on outcomes for women with a liver transplant. STUDY DESIGN: The National (Nationwide) Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project from 1998 to 2014 was used for this repeated cross-sectional analysis. Women aged between 15 and 54 years, with a history of liver transplant who underwent delivery, antepartum, or postpartum hospitalizations were identified. Temporal trends in deliveries of women with liver transplants were analyzed. The risk for severe maternal morbidity (SMM) excluding transfusion based on criteria from the Centers for Disease Control and Prevention (CDC), as well as for individual outcomes including hypertensive diseases of pregnancy, postpartum hemorrhage, placental abruption, liver rejection, cesarean delivery, preterm delivery, and coagulopathy during delivery hospitalizations were analyzed. Risks of SMM during antepartum and postpartum hospitalizations were also analyzed. An adjusted log-linear regression model for SMM during delivery hospitalizations including demographic factors, hospital characteristics, and underlying comorbidity was performed. The chi-squared or Fisher's exact test was used for comparisons. Temporal trends were analyzed with the Cochran-Armitage trend test. Population weights were applied to create national estimates. RESULTS: From 1998 to 2014, an estimated 1165 births occurred by women with a liver transplant. The number of births occurring by women with liver transplants increased over the study period from 1.0 per 100,000 in 1998-2000 to 2.8 per 100,000 in 2012-2014 (p < .01). The risk for CDC SMM excluding transfusion was significantly higher during delivery hospitalizations among women with compared to without liver transplant (8.0 versus 0.5%, p < .01, unadjusted risk ratio 15.4, 95% CI 12.7-18.6). Women with liver transplant were also at significantly higher risk for abruption (2.5 versus 1.0%, p = .03), hypertensive diseases of pregnancy (27.8 versus 6.9%, p < .01), postpartum hemorrhage (8.0 versus 2.8%, p = .01), cesarean delivery (51.7 versus 29.5%, p < .01), preterm delivery (27.5 versus 7.0%, p < .01), and coagulopathy (3.1 versus 0.3%, p < .01). A diagnosis of liver rejection was present during 4.1% of delivery hospitalizations for women with liver transplant. In the adjusted analysis for severe morbidity excluding transfusion risk was retained with liver transplant associated with increased likelihood of this adverse outcome (aRR 8.49, 95% CI 5.59-12.87). Women with liver transplants were at significantly higher likelihood of undergoing antepartum and postpartum admissions, and of experiencing SMM during these hospitalizations. CONCLUSION: In this analysis of antepartum, delivery, and postpartum hospitalizations, women with liver transplant were at significantly higher risk for both SMM during all hospitalizations and for a range of adverse outcomes including placental abruption, hypertensive diseases of pregnancy, postpartum hemorrhage, cesarean delivery, and coagulopathy delivery during delivery hospitalizations. While deliveries to women with liver transplant were rare, these births became more frequent over the study period.

AASM criteria for scoring respiratory events: interaction between apnea sensor and hypopnea definition.

STUDY OBJECTIVES: To examine the impact of using a nasal pressure sensor only vs the American Academy of Sleep Medicine (AASM) recommended combination of thermal and nasal pressure sensors on (1) the apnea index (AI), (2) the apnea-hypopnea index (AHI), where the AHI is calculated using both AASM definitions of hypopnea, and (3) the accuracy of a diagnosis of obstructive sleep apnea (OSA). DESIGN: Retrospective review of previously scored in-laboratory polysomnography. SETTING: A tertiary-hospital clinical sleep laboratory. PATIENTS OR PARTICIPANTS: One hundred sixty-four consecutive adult patients with a potential diagnosis of OSA, who were examined during a 3-month period. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Studies were scored with and without the use of the oronasal thermal sensor. AIs and AHIs, using the nasal pressure sensor alone (AI(np) and AHI(np)), were compared with those using both a thermal sensor for the detection of apnea and a nasal pressure transducer for the detection of hypopnea (AI(th) and AHI(th)). Comparisons were repeated using the AASM recommended (AASM(rec)) and alternative (AASM(alt)) hypopnea definitions. AI was significantly different when measured from the different sensors, with AI(np) being 51% higher on average. Using the AASM(rec) hypopnea definition, the mean AHI(np) was 15% larger than the AHI(th); with large interindividual differences and an estimated 9.8% of patients having a false-positive OSA diagnosis at a cutpoint of 15 events and 4.3% at 30 events per hour. Using AASM(alt) hypopnea definition, the mean AHI(np) was 3% larger than the AHI(th), with estimated false-positive rates of 4.6% and 2.4%, respectively. The false-negative rate was negligible at 0.1% for both hypopnea definitions. CONCLUSIONS: This study demonstrates that using only a nasal pressure sensor for the detection of apnea resulted in higher values of AI and AHI than when the AASM recommended thermal sensor was added to detect apnea. When the AASM(alt) hypopnea definition was used, the differences in AHI and subsequent OSA diagnosis were small and less than when the AASM(rec) hypopnea definition was used. In situations in which a thermal sensor cannot be used, for example, in limited-channel diagnostic devices, the AHI obtained with a nasal pressure sensor alone differs less from the AHI obtained from a polysomnogram that includes a thermal sensor when the AASM(alt) definition rather than the AASM(rec) definition of hypopnea is used. Thus, diagnostic accuracy is impacted both by the absence of the thermal sensor and by the rules used to analyze the polysomnography. Furthermore, where the thermal sensor is unreliable for sections of a study, it is likely that use of the nasal pressure signal to detect apnea will have modest impact.

The 2007 AASM recommendations for EEG electrode placement in polysomnography: impact on sleep and cortical arousal scoring.

STUDY OBJECTIVE: To examine the impact of using American Academy of Sleep Medicine (AASM) recommended EEG derivations (F4/M1, C4/M1, O2/M1) vs. a single derivation (C4/M1) in polysomnography (PSG) on the measurement of sleep and cortical arousals, including inter- and intra-observer variability. DESIGN: Prospective, non-blinded, randomized comparison. SETTING: Three Australian tertiary-care hospital clinical sleep laboratories. PATIENTS OR PARTICIPANTS: 30 PSGs from consecutive patients investigated for obstructive sleep apnea (OSA) during December 2007 and January 2008. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: To examine the impact of EEG derivations on PSG summary statistics, 3 scorers from different Australian clinical sleep laboratories each scored separate sets of 10 PSGs twice, once using 3 EEG derivations and once using 1 EEG derivation. To examine the impact on inter- and intra-scorer reliability, all 3 scorers scored a subset of 10 PSGs 4 times, twice using each method. All PSGs were de-identified and scored in random order according to the 2007 AASM Manual for the Scoring of Sleep and Associated Events. Using 3 referential EEG derivations during PSG, as recommended in the AASM manual, instead of a single central EEG derivation, as originally suggested by Rechtschaffen and Kales (1968), resulted in a mean ± SE decrease in N1 sleep of 9.6 ± 3.9 min (P = 0.018) and an increase in N3 sleep of 10.6 ± 2.8 min (P = 0.001). No significant differences were observed for any other sleep or arousal scoring summary statistics; nor were any differences observed in inter-scorer or intra-scorer reliability for scoring sleep or cortical arousals. CONCLUSION: This study provides information for those changing practice to comply with the 2007 AASM recommendations for EEG placement in PSG, for those using portable devices that are unable to comply with the recommendations due to limited channel options, and for the development of future standards for PSG scoring and recording. As the use of multiple EEG derivations only led to small changes in the distribution of derived sleep stages and no significant differences in scoring reliability, this study calls into question the need to use multiple EEG derivations in clinical PSG as suggested in the AASM manual.

The new AASM criteria for scoring hypopneas: impact on the apnea hypopnea index.

STUDY OBJECTIVES: To compare apnea-hypopnea indices (AHIs) derived using 3 standard hypopnea definitions published by the American Academy of Sleep Medicine (AASM); and to examine the impact of hypopnea definition differences on the measured prevalence of obstructive sleep apnea (OSA). DESIGN: Retrospective review of previously scored in-laboratory polysomnography (PSG). SETTING: Two tertiary-hospital clinical sleep laboratories. PATIENTS OR PARTICIPANTS: 328 consecutive patients investigated for OSA during a 3-month period. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: AHIs were originally calculated using previous AASM hypopnea scoring criteria (AHI(Chicago)), requiring either >50% airflow reduction or a lesser airflow reduction with associated >3% oxygen desaturation or arousal. AHIs using the "recommended" (AHI(Rec)) and the "alternative" (AHI(Alt)) hypopnea definitions of the AASM Manual for Scoring of Sleep and Associated Events were then derived in separate passes of the previously scored data. In this process, hypopneas that did not satisfy the stricter hypopnea definition criteria were removed. For AHI(Rec), hypopneas were required to have > or =30% airflow reduction and > or =4% desaturation; and for AHI(Alt), hypopneas were required to have > or =50% airflow reduction and > or =3% desaturation or arousal. The median AHI(Rec) was approximately 30% of the median AHI(Chicago), whereas the median AHI(Alt), was approximately 60% of the AHI(Chicago), with large, AHI-dependent, patient-specific differences observed. Equivalent cut-points for AHI(Rec) and AHI(Alt), compared to AHI(Chicago) cut-points of 5, 15, and 30/h were established with receiver operator curves (ROC). These cut-points were also approximately 30% of AHI(Chicago) using AHI(Rec) and 60% of AHI(Chicago) using AHI(Alt). Failure to adjust cut-points for the new criteria would result in approximately 40% of patients previously classifled as positive for OSA using AHI(Chicago) being negative using AHI(Rec) and 25% being negative using AHI(Alt). CONCLUSIONS: This study demonstrates that using different published standard hypopnea definitions leads to marked differences in AHI. These results provide insight to clinicians and researchers in interpreting results obtained using different published standard hypopnea definitions, and they suggest that consideration should be given to revising the current scoring recommendations to include a single standardized hypopnea definition.

Rectal temperature correction overestimates the frequency of exercise-induced hypoxemia.

INTRODUCTION: Exercise-induced hypoxemia (EIH) occurs in an uncertain proportion of endurance trained athletes. Whereas blood gas measurements must be corrected for core temperature at the time of sampling, the commonly used rectal temperature readings may not be the most appropriate. METHODS: Ten males [mean peak oxygen uptake, (.-)VO(2peak), 65.4 +/- 7.0 mL x kg x min] performed incremental treadmill exercise from rest to exhaustion with radial artery blood samples collected at the end of each 2-min workload for gas analysis. The thermogenic effect of exercise was monitored with rectal, arterial blood, and esophageal temperature probes, and the values obtained at all three sites, simultaneous with blood sampling, were used to correct the standard blood gas measurements made at 37 +/- C. RESULTS: The mean increase in rectal temperature across exercise (1.4 +/- 0.4 +/- C) was approximately half that recorded in radial arterial blood (2.3 +/- 0.5+/- C) and the esophagus (2.4 +/- 0.5 degrees C). In consequence, the uncorrected fall in PaO2 across exercise of 15.4 +/- 8.2 mm Hg was reduced to 8.4 +/- 7.7 mm Hg when corrected for rectal temperature, and to 2.9 +/- 7.4 and 2.1 +/- 8.8 mm Hg when corrected for arterial blood and esophageal temperatures. Using a fall of > or = 10 mm Hg as the index of EIH, the proportion in the 10 subjects in the present study fell from 80% (uncorrected) through 50% (rectal correction) to 20% (arterial blood and esophageal corrections). CONCLUSION: When correcting arterial blood gas values for the thermogenic effects of exercise, the proportion of athletes meeting the definition of EIH depends on the site of core temperature measurement.