David J. Cotton

Outcomes of Home-Based Diagnosis and Treatment of Obstructive Sleep Apnea

BACKGROUND Home diagnosis and therapy for obstructive sleep apnea (OSA) may improve access to testing and continuous positive airway pressure (CPAP) treatment. We compared subjective sleepiness, sleep quality, quality of life, BP, and CPAP adherence after 4 weeks of CPAP therapy in subjects in whom OSA was diagnosed and treated at home and in those evaluated in the sleep laboratory. METHODS A randomized trial was performed consisting of home-based level 3 testing followed by 1 week of auto-CPAP and fixed-pressure CPAP based on the 95% pressure derived from the auto-CPAP device, and in-laboratory polysomnography (PSG) (using mostly split-night protocol) with CPAP titration; 102 subjects were randomized (age, 47.4 +/- 11.4 years; 63 men; BMI, 32.3 +/- 6.3 kg/m(2); Epworth Sleepiness Scale [ESS]: 12.5 +/- 4.3). The outcome measures were daytime sleepiness (ESS), sleep quality (Pittsburgh Sleep Quality Index [PSQI]), quality of life (Calgary Sleep Apnea Quality of Life Index [SAQLI], 36-Item Short-Form Health Survey [SF-36], BP, and CPAP adherence after 4 weeks. RESULTS After 4 weeks of CPAP therapy, there were no significant differences in ESS (PSG 6.4 +/- 3.8 vs home monitoring [HM] 6.5 +/- 3.8, P = .71), PSQI (PSG 5.4 +/- 3.1 vs HM 6.2 +/- 3.4, P = .30), SAQLI (PSG 4.5 +/- 1.1 vs HM 4.6 +/- 1.1, P = .85), SF-36 vitality (PSG 62.2 +/- 23.3 vs HM 64.1 +/- 18.4, P = .79), SF-36 HM (PSG 84.0 +/- 10.4 vs HM 81.3 +/- 14.9, P = .39), and BP (PSG 129/84 +/- 11/0 vs HM 125/81 +/- 13/9, P = .121). There was no difference in CPAP adherence (PSG 5.6 +/- 1.7 h/night vs HM 5.4 +/- 1.0 h/night, P = .49). CONCLUSIONS Compared with the home-based protocol, diagnosis and treatment of OSA in the sleep laboratory does not lead to superior 4-week outcomes in sleepiness scores, sleep quality, quality of life, BP, and CPAP adherence. TRIAL REGISTRATION clinicaltrials.gov; Identifier: NCT00139022.

Pregnant women with gestational hypertension may have a high frequency of sleep disordered breathing.

BACKGROUND Gestational hypertension is a common complication of pregnancy. Recent evidence suggests that women with gestational hypertension have a high rate of sleep disordered breathing (SDB). Using laboratory-based polysomnography, we evaluated for the frequency of SDB in women with gestational hypertension compared to healthy women with uncomplicated pregnancies. METHODS In this single-center cross-sectional study, women with the diagnosis of gestational hypertension were screened in the Fetal Assessment Unit and Antepartum ward. Healthy subjects were recruited by local advertising. Subjects completed a series of questionnaires addressing sleep quality and daytime sleepiness, followed by full night polysomnography. The primary outcome was frequency of SDB (defined as a respiratory disturbance index ≥ 5) in the gestational hypertension and healthy groups. RESULTS A total of 34 women with gestational hypertension and singleton pregnancies and 26 healthy women with uncomplicated singleton pregnancies consented to participate in the study. The mean ages and gestational ages, but not the body mass indices, of the 2 groups were similar. The frequencies of SDB in the more obese gestational hypertension group and the healthy group were 53% and 12%, respectively (P < 0.001). INTERPRETATION Women with gestational hypertension may have a significantly higher frequency of SDB than do healthy women with uncomplicated pregnancies of similar gestational age. The relative causal contributions, if any, of SDB and obesity remain to be determined.

A Theoretical Analysis of the Single Breath Diffusing Capacity for Carbon Monoxide

We used a computerized lung model to examine methods of measuring the single breath diffusing capacity for carbon monoxide (DLCOSB). Although the single breath maneuver consists of inhalation, breath holding, and exhalation, current methods of measuring DLCOSB use one equation that is accurate only for breath holding, and they attempt to correct for the effects of inhalation and exhalation using a rigidly standardized procedure. Using a uniform lung model, we verified that variations in performing the standarized maneuver and variations in alveolar gas sampling, which frequently occur in practice, cause wide variability in the measured DLCOSB. We developed a new method of calculating DLCOSB based on three equations to describe diffusion in the lung during inhalation, breath holding, and exhalation. In computer simulations of the single breath maneuver, this method yielded accurate measurements of DLCOSB despite variations in flow rates, breath hold times, or the size and timing of the collected sample of exhaled alveolar gas. Furthermore, using a lung model in which the diffusing capacity was nonuniformly distributed, we found that this method gave an accurate estimate of the overall diffusing capacity of the lung from the collection of the entire exhaled alveolar gas sample, while previously accepted methods overestimated DLCOSB. We predict that a more precise calculation of the overall diffusing capacity using the entire alveolar gas sample can minimize errors in the test introduced by variations in the maneuver or variations in the distribution of diffusion.

Comparison of polysomnographic and portable home monitoring assessments of obstructive sleep apnea in Saskatchewan women.

OBJECTIVES To compare a commercially available, level III in-home diagnostic sleep test (Embletta, Embletta USA) and in-laboratory polysomnography (PSG) in women with suspected obstructive sleep apnea (OSA). METHODS Consecutive women scheduled for routine PSG testing for evaluation of clinically suspected OSA and who met inclusion⁄exclusion criteria, were invited to participate. An in-home Embletta portable monitor test was performed one week before or after diagnostic PSG. RESULTS Forty-seven of 96 women who met the inclusion⁄exclusion criteria agreed to participate. The mean (± SD) age of the patients was 52.0 ± 11.0 years, with a mean body mass index of 34.86 ± 9.04 kg⁄m2, and 66% (31 of 47) of patients were at high risk for OSA according to the Berlin score. Paired analysis of the overall population revealed no significant difference in mean apnea⁄hypopnea index (AHI) between the two diagnostic methods (P = 0.475). At an AHI of ≥ 5, the Embletta test was highly sensitive (90.6%) in determining abnormal versus normal OSA, with a positive predictive value of 82.7%. However, a higher Embletta AHI threshold of ≥ 10 may be more useful, with a higher level of agreement (kappa coefficient) with PSG testing and a positive predictive value of 92.3%. The in-home study was less useful at distinguishing severe from nonsevere OSA, yielding a sensitivity of 50%. CONCLUSIONS In women believed to be at high-risk for OSA, Embletta in-home sleep testing is useful for the detection of sleep disordered breathing.

Sleep disordered breathing and gestational hypertension: postpartum follow-up study.

BACKGROUND Gestational hypertension (GH) is a newly recognized risk factor for adverse cardiovascular events later in life. Sleep disordered breathing (SDB) is an established risk factor for adverse cardiovascular events. Recent research has suggested that women with GH may have an increased rate of SDB during pregnancy, but it is not known if this higher rate of SDB persists into the postpartum state. OBJECTIVE To assess whether women with GH continue to have an increased rate of SDB compared to healthy pregnant women, after the physiologic changes of pregnancy resolve. METHODS We previously studied women with GH and uncomplicated pregnancies with sleep questionnaires and level 1 polysomnography. Participants were invited to participate in repeat testing 1-2 years postpartum. Respiratory disturbance index (RDI) differences were assessed. RESULTS Eighteen subjects (11 GH and 7 healthy) had complete follow-up data available for comparison with antepartum data. This group was representative of the initial antepartum cohort. Women with GH experienced a decrease in mean RDI from antepartum to postpartum (12.0 ± 12.3 vs. 2.9 ± 2.9; P = 0.02). Healthy women did not experience the same change (2.8 ± 5.3 vs. 2.1 ± 3.2; P = 0.81). Postpartum comparisons showed the mean RDI of women with GH had decreased to be similar to that of healthy women (P = 0.75). CONCLUSIONS SDB in women with gestational hypertension improved in the postpartum state to levels indistinguishable from our healthy subjects. This suggests that the physiologic effects of pregnancy may have had a pathologic role in the development of antepartum SDB in women with GH.

Effect of a deep breath on gas mixing and diffusion in the lung.

We examined the effect of a previous deep breath on both inert gas mixing and the single breath diffusing capacity (DLCOSB) during submaximal single breath maneuvers in normal subjects. Single breath washouts were performed either immediately after a deep breath or after breathing tidally for 10 min. Maneuvers consisted of inhaling test gas from functional residual capacity to 50% inspiratory capacity and, after either 0 or 6 s of breath holding, exhaling slowly back to residual volume. We measured the Fowler dead space, the Phase III slope of the alveolar plateau of the He washout (delta He/L), the amplitude of the cardiogenic oscillations (Oc), closing capacity, mixing efficiency (Emix) and DLCOSB using the three equation method. For maneuvers immediately after a deep breath we found that delta He/L was steeper and the Oc were larger for washouts with 6 s but not 0 s of breath holding, while Emix was significantly lower and DLCOSB significantly higher for both the 0 s and the 6 s breath holding maneuvers. We conclude that a deep breath increases DLCOSB but simultaneously also increases convective-dependent inhomogeneity in the lung.

Effect of high negative inspiratory pressure on single breath CO diffusing capacity

We measured the single breath diffusing capacity for carbon monoxide (DLcoSB) using a three-equation method to describe CO uptake in 10 normal seated subjects who either voluntarily inhaled slowly (0.5 L/sec) to total lung capacity (TLC), or inhaled slowly to TLC with maximal effort through a high inspiratory resistance which created high negative inspiratory pressure. Subjects then immediately exhaled slowly at a voluntarily controlled exhaled flow. Single breath maneuvers were performed in duplicate both with and without high negative inspiratory pressure while subjects were seated upright at rest and during steady-state bicycle exercise. We found that high negative inspiratory pressure increased DLcoSB by 10.5 +/- 4.9% (mean +/- 1 SD) at rest (P less than 0.001). In 7 subjects low level exercise alone increased DLcoSB by a similar amount (12.1 +/- 7.3%; P = 0.005). In six of the subjects there was a significant correlation between the increase in DLcoSB during high negative inspiratory pressure at rest and the increase in DLcoSB during steady-state exercise (r = 0.89; P less than 0.01). During steady-state exercise, high negative inspiratory pressure further increased DLcoSB 6.4 +/- 6.3% compared to exercise alone (P = 0.05). We conclude that the increase in DLcoSB with high negative inspiratory pressure at rest is a simple reproducible method of assessing recruitment of the pulmonary capillary bed in man.

Grain Dust and Health. I. Host Factors

Excerpt Twenty-three papers including work in progress as well as previously published data were considered (1-23). Populations at risk are 500 000 workers in the United States (4), and 30 000 in C...

Implementing the Three-Equation Method of Measuring Single Breath Carbon Monoxide Diffusing Capacity

Conventional methods of measuring the single breath diffusing capacity of the lung for carbon monoxide (DLcoSB) are based on the Krogh equation, which is valid only during breath holding. Rigid standardization is used to approximate a pure breath hold manoeuvre, but variations in performing the manoeuvre cause errors in the measurement of DLcoSB. The authors previously described a method of measuring DLcoSB using separate equations describing carbon monoxide uptake during each phase of the manoeuvre: inhalation, breath holding and exhalation. The method is manoeuvre-independent, uses all of the exhaled alveolar gas to improve estimates of mean DLcoSB and lung volume, and is more accurate and precise than conventional methods. A slow, submaximal, more physiological single breath manoeuvre can be used to measure DLcoSB in patients who cannot achieve the flow rates and breath hold times necessary for the standardized manoeuvre. The method was initially implemented using prototype equipment but commercial systems are now available that are capable of implementing this method. The authors describe how to implement the method and discuss considerations to be made in its use.

Can gestational hypertension be modified by treating nocturnal airflow limitation

OBJECTIVE Recent evidence suggests that women with gestational hypertension (GH) have a high rate of sleep disordered breathing (SDB), and treatment for even marginal SDB may improve blood pressure control in women with GH. We assessed whether the application SDB treatment could improve blood pressure in women with GH. METHODS This was a single-center randomized study. Subjects underwent an unattended home-based diagnostic sleep study. The study was then repeated with subjects wearing one of two randomly assigned treatments: auto-titrating continuous positive airway pressure (auto-CPAP) or mandibular advancement device (MAD) + nasal strip. First morning blood pressure and blood for standard GH measures plus inflammatory markers were taken after each study. Subjects completed a series of questionnaires addressing sleep quality and tolerance of assigned therapy. RESULTS Twenty-four women completed the protocol-13 in the MAD group and 11 in auto-CPAP. The overall rate of SDB was 38%. Auto-CPAP was more effective at treating SDB than MAD + nasal strip, although the women randomized to MAD + nasal strip reported the greater comfort with therapy. First morning blood pressure was not consistently improved with either therapy. When subjects were stratified according to those whose blood pressure increased or decreased with therapy, an association was suggested between blood pressure improvement and reduced levels of tumour necrosis factor-α. CONCLUSION We demonstrated that 38% of women with GH had concurrent SDB. We did not find an improvement in blood pressure or inflammatory markers with a single night of either the auto-CPAP or MAD + nasal strip interventions. However important lessons from this study may guide future investigations in this area.