Inspiratory flow limitation during sleep in pre-eclampsia: comparison with normal pregnant and nonpregnant women

Adverse pregnancy outcomes and pharyngeal flow limitation during sleep: Nulliparous Pregnancy Outcomes Study Monitoring Mothers-to-be (nuMoM2b)

BACKGROUND

Pharyngeal flow limitation during pregnancy may be a risk factor for adverse pregnancy outcomes but was previously challenging to quantify. Our objective was to determine whether a novel objective measure of flow limitation identifies an increased risk of pre-eclampsia (primary outcome) and other adverse outcomes in a prospective cohort: Nulliparous Pregnancy Outcomes Study Monitoring Mothers-to-be (nuMoM2b).

METHODS

Flow limitation severity scores (0%=fully obstructed, 100%=open airway), quantified from breath-by-breath airflow shape, were obtained from home sleep tests during early (6-15 weeks) and mid (22-31 weeks) pregnancy. Multivariable logistic regression quantified associations between flow limitation (median overnight severity, both time-points averaged) and pre-eclampsia, adjusting for maternal age, body mass index (BMI), race, ethnicity, chronic hypertension and flow limitation during wakefulness. Secondary outcomes were hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM) and infant birthweight.

RESULTS

Of 1939 participants with flow limitation data at both time-points (mean±sd age 27.0±5.4 years and BMI 27.7±6.1 kg·m-2), 5.8% developed pre-eclampsia, 12.7% developed HDP and 4.5% developed GDM. Greater flow limitation was associated with increased pre-eclampsia risk: adjusted OR 2.49 (95% CI 1.69-3.69) per 2sd increase in severity. Findings persisted in women without sleep apnoea (apnoea-hypopnoea index <5 events·h-1). Flow limitation was associated with HDP (OR 1.77 (95% CI 1.33-2.38)) and reduced infant birthweight (83.7 (95% CI 31.8-135.6) g), but not GDM.

CONCLUSIONS

Greater flow limitation is associated with increased risk of pre-eclampsia, HDP and lower infant birthweight. Flow limitation may provide an early target for mitigating the consequences of sleep disordered breathing during pregnancy.

Common sleep disorders in pregnancy: a review

In this review, we provide a comprehensive overview of common sleep disorders during pregnancy, including their characterization, prevalence, risk factors, and possible contribution to maternal and fetal outcomes. We conducted a quasi-systematic literature search of the MEDLINE database and identified 744 studies from 1991 through 2021, inclusive, that met our inclusion criteria. We synthesized the existing literature on sleep disorders during pregnancy and highlighted controversies, research gaps, and needed clinical developments. Our review covers a range of sleep disorders, including insomnia, obstructive sleep apnea, restless legs syndrome, and circadian rhythm disorders. We discuss the prevalence of these disorders in pregnancy and their potential impact on maternal and fetal health outcomes. We also explore the relationship between sleep disorders, pre-pregnancy comorbidities such as obesity, and pregnancy-related conditions such as gestational diabetes mellitus and preeclampsia. In addition to summarizing the existing literature on sleep disorders during pregnancy, we also highlight opportunities for further research in this area. We suggest that future studies should strive to employ validated and objective measurement tools for sleep disorders and prioritize utilization of longitudinal methods with participant follow-up through postpartum, mid-life, menopause, and beyond. We also put forward investigation into the impact of circadian rhythm disruption on reproductive physiology and early pregnancy outcomes as an area of important work. Overall, our review provides valuable insights on sleep and reproduction and into common sleep disorders during pregnancy and their potential impact on maternal and fetal health outcomes.

Treatment of obstructive sleep apnea in high risk pregnancy: a multicenter randomized controlled trial

BACKGROUND

Obstructive sleep apnea (OSA) during pregnancy is a risk factor for preeclampsia possibly through a link to placental physiology. This study evaluates the efficacy of continuous positive airway pressure (CPAP) on the modulation of blood pressure and the reduction in preeclampsia in women with high-risk pregnancy and OSA.

METHODS

A multicenter open-label, randomized controlled trial comparing CPAP treatment versus usual antenatal care was conducted in three academic hospitals in Bangkok, Thailand. Participants included singleton pregnant women aged older than 18 years with any high-risk condition (i.e., chronic hypertension, obesity, history of preeclampsia or gestational diabetes in the previous pregnancy, or diabetes), and OSA (respiratory disturbance index 5-29.99 events/hour by polysomnography), who presented either in the first trimester (gestational age, GA 0-16 weeks) or subsequently developed OSA during the 2nd trimester (GA 24-28 weeks). The primary endpoint was blood pressure during antenatal care. Secondary endpoints included the incidence of preeclampsia. An intention-to-treat analysis was performed with additional per-protocol and counterfactual analyses for handling of nonadherence.

RESULTS

Of 340 participants, 96.5% were recruited during the first trimester. Thirty participants were later excluded leaving 153 and 157 participants in the CPAP and usual-care groups for the modified-intention-to-treat analysis. CPAP adherence rate was 32.7% with average use of 2.5 h/night. Overall, CPAP treatment significantly lowered diastolic blood pressure (DBP) by - 2.2 mmHg [95% CI (- 3.9, - 0.4), p = 0.014], representing approximately - 0.5 mmHg per hour of CPAP use [95%CI (- 0.89, - 0.10), p = 0.013]. CPAP treatment also altered the blood pressure trajectory by continuously lowering DBP throughout pregnancy with mean differences (95% CI) of - 3.09 (- 5.34, - 0.93), - 3.49 (- 5.67, - 1.31) and - 3.03 (- 5.20, - 0.85) mmHg at GA 18-20, 24-28, and 32-34 weeks, respectively compared to 0-16 weeks. Preeclampsia rate was 13.1% (20/153 participants) in the CPAP and 22.3% (35/157 participants) in the usual-care group with a risk difference (95% CI) of - 9% (- 18%, - 1%, p-value = 0.032) and a number-needed-to-treat (95% CI) of 11 (1, 21).

CONCLUSIONS

CPAP treatment in women with even mild-to-moderate OSA and high-risk pregnancy demonstrated reductions in both DBP and the incidence of preeclampsia. CPAP treatment also demonstrated a sustained reduction in DBP throughout gestation. Trial registration ClinicalTrial.GovNCT03356106, retrospectively registered November 29, 2017.

Immediate Physiological Responses to Inspiratory Flow Limited Events in Mild Obstructive Sleep Apnea

Rationale: Inspiratory flow limitation (IFL), characterized by flattening of individual breaths on the airflow/time tracing, is a noninvasive indicator of elevated upper airway resistance. An IFL "event" in isolation has not been defined, nor has the ability to reproducibly identify event occurrence been tested. IFL events and their association with immediate physiological responses-as well as the impact of characteristics such as age, sex, sleep stage, sleepiness, and event duration on their association with such outcomes-have not been studied. Symptomatic patients with a normal to mildly abnormal apnea-hypopnea index who have predominant IFL on their polysomnography may benefit from treatment. Objectives: To test the reproducibility of identifying IFL events and their termination and to determine the frequency of the immediate physiological response to their occurrence, including desaturation, electroencephalography (EEG) arousal, and increased heart rate (HR). Methods: Fifty-eight patients with obstructive sleep apnea (OSA) underwent full diagnostic polysomnography. IFL events and their termination were identified manually using predefined rules from the unscored nasal cannula flow channel alone and were evaluated for responses such as EEG arousal, oxygen desaturation of ⩾3%, and HR increase. Results: Interscorer reliability was acceptable, with an average percent agreement for occurrence of 82% ± 3%. Of all IFL events, 24% (regardless of the definition) were not associated with an EEG arousal, an increase in HR, or O₂ desaturation. Of all IFL events scored, 25% caused O₂ desaturation, 40% were associated with an EEG arousal, and 55% were associated with an increase in HR; 67% caused either an EEG arousal and/or an increase in HR. Responses were observed to occur either in isolation or in combination. IFL events that terminated with at least two non-IFL breaths, one of which had a 200% increase in amplitude, were significantly associated with O₂ desaturation, EEG arousal, and increase in HR compared with events that ended in one non-IFL breath. IFL events that had a >50% reduction in flow amplitude compared with baseline were significantly associated with O₂ desaturation compared with events that had a 30% reduction or less. Conclusions: Most IFL events resulted in immediate physiological responses, and no single consequence reliably occurred after every event. We propose a framework that can incorporate the scoring of IFL events into assessing the diagnosis and severity of OSA and suggest that no single consequence be used to define IFL as a respiratory event. The relationship of IFL events to OSA outcomes remains to be tested.

Frequency of flow limitation using airflow shape

STUDY OBJECTIVES

The presence of flow limitation during sleep is associated with adverse health consequences independent of obstructive sleep apnea (OSA) severity (apnea-hypopnea index, AHI), but remains extremely challenging to quantify. Here we present a unique library and an accompanying automated method that we apply to investigate flow limitation during sleep.

METHODS

A library of 117,871 breaths (N=40 participants) were visually classified (certain flow limitation, possible flow limitation, normal) using airflow shape and physiological signals (ventilatory drive per intra-esophageal diaphragm EMG). An ordinal regression model was developed to quantify flow limitation certainty using flow-shape features (e.g. flattening, scooping); breath-by-breath agreement (Cohen's ƙ) and overnight flow limitation frequency (R 2, %breaths in certain or possible categories during sleep) were compared against visual scoring. Subsequent application examined flow limitation frequency during arousals and stable breathing, and associations with ventilatory drive.

RESULTS

The model (23 features) assessed flow limitation with good agreement (breath-by-breath ƙ=0.572, p<0.001) and minimal error (overnight flow limitation frequency R 2=0.86, error=7.2%). Flow limitation frequency was largely independent of AHI (R 2=0.16) and varied widely within individuals with OSA (74[32-95]%breaths, mean[range], AHI>15/hr, N=22). Flow limitation was unexpectedly frequent but variable during arousals (40[5-85]%breaths) and stable breathing (58[12-91]%breaths), and was associated with elevated ventilatory drive (R 2=0.26-0.29; R 2<0.01 AHI v. drive).

CONCLUSIONS

Our method enables quantification of flow limitation frequency, a key aspect of obstructive sleep-disordered breathing that is independent of the AHI and often unavailable. Flow limitation frequency varies widely between individuals, is prevalent during arousals and stable breathing, and reveals elevated ventilatory drive.

Fetal Heart Rate Decelerations in Women with Sleep-Disordered Breathing

Emerging literature has shown that women with sleep-disordered breathing (SDB) have increased risk for gestational hypertension/preeclampsia and gestational diabetes. Case reports suggest an association between maternal apnea and fetal heart rate deceleration but data are lacking on how maternal sleep impacts fetal health. Since decelerations may be associated with adverse outcomes, we sought to determine whether fetal heart rate decelerations were associated with SDB. A cohort study of third trimester pregnant women with a singleton fetus was conducted. Participants underwent a home sleep test with continuous portable electronic fetal monitoring. SDB was defined as a respiratory disturbance index (RDI)≥10 events/hour. The temporality between a respiratory event and fetal heart rate decelerations was determined to be present if a deceleration occurred < 30 s after a respiratory event. Forty women were included with mean (±SD) age, BMI, and gestational age of 32.0±5.5 years, 37.1±8.0 kg/m², and 34.6±2.4 weeks respectively. Overall, n=23 (57.5%) women had SDB. Thirty-seven late decelerations were observed in 18 women; of these, 84% were temporally associated with a respiratory event. Nine of the 18 women (50%) had SDB. Ten prolonged decelerations were observed in 6 women of which nine (90%) were temporally associated with a respiratory event. Five of the six women (83%) had an RDI≥10. These initial data suggest that, in this population, the majority of both late and prolonged fetal heart rate decelerations occur with a maternal respiratory event. Since respiratory events are characteristic of maternal SDB, this raises the possibility that SDB may influence fetal well-being.

Sleep-disordered breathing in pregnancy: a developmental origin of offspring obesity?

Sleep-disordered breathing (SDB) worsens over pregnancy, and obstructive sleep apnea is associated with serious maternal complications. Intrauterine exposures that provoke insulin resistance (IR), inflammation, or oxidative stress may have long-term offspring health consequences. In obesity, worsening maternal SDB appears to be an exposure that increases the risk for both small- or large-for-gestational-age (SGA, LGA, respectively), suggesting distinct outcomes linked to a common maternal phenotype. The aim of this paper is to systematically review and link data from both mechanistic rodent models and descriptive human studies to characterize the impact of maternal SDB on fetal development. A systematic review of the literature was conducted using PubMed, Embase, and CINAHL (01/2000-09/2019). Data from rodent (9 studies) and human models (48 studies, 5 meta-analyses) were included and reviewed using PRISMA guidelines. Evidence from rodent models suggests that intermittent maternal hypoxia results in mixed changes in birth weight (BW) followed by accelerated postnatal growth, while maternal sleep fragmentation results in normal BW followed by later metabolic derangement. Human studies support that maternal SDB is associated with both SGA and LGA, both of which may predispose offspring to later obesity. Evidence also suggests a link between SDB, inflammation, and oxidative stress that may impact maternal metabolism and/or placental function. SDB is common in pregnancy and affects fetal growth and development. Given that SDB has significant potential to adversely influence the intrauterine metabolic environment, larger, prospective studies in humans are urgently needed to fully elucidate the effects of this exposure on offspring metabolic risk.

Sleep disordered breathing in pregnancy: A review of the pathophysiology of adverse pregnancy outcomes

Sleep disordered breathing (SDB) is a common obesity-related co-morbidity with strong associations to cardiometabolic disease. The risk of SDB is increased during pregnancy, particularly among obese pregnant women. Accumulating evidence suggests that an association exists between maternal SDB and the development of adverse pregnancy outcomes, particularly gestational diabetes and hypertensive disorders of pregnancy. Intermittent hypoxia, a central characteristic of SDB, has been shown in animal and clinical studies to dysregulate several biological pathways. This includes the promotion of oxidative stress, increased inflammation, activation of the hypothalamic-pituitary-adrenal axis, increased sympathetic activity and impaired glucose and insulin metabolism. This review considers how, during pregnancy, these pathophysiological processes are plausible mechanisms through which SDB may contribute to an increased risk of adverse outcomes, for the mother and perhaps also the offspring. However, a lack of robust evidence specific to the pregnant population, including limited evaluation of the placental function in affected pregnancies, limits our ability to draw definite conclusions on mechanisms contributing to adverse pregnancy outcomes and, indeed, the strength of association between SDB and certain pregnancy complications.

Intermittent Hypoxia Impairs Trophoblast Cell Viability by Triggering the Endoplasmic Reticulum Stress Pathway

Intermittent hypoxia (IH) is a prominent characteristic of many clinical complications such as obstructive sleep apnea syndrome (OSAS). OSAS is related to a higher incidence of adverse pregnancy outcomes, and IH has been suggested as the preliminary physiological etiology. However, further studies remain to be performed on the underlying cellular and molecular pathogenic mechanisms of OSAS-related IH on adverse pregnancy outcomes. Here, we used a trophoblast cell line (HTR8/SVneo), primary extravillous trophoblast cells (EVTs), and a normal-term placenta villi explant culture model in vitro in this research. The effects and possible molecular mechanisms of IH on trophoblast motility, cell cycle progression, and apoptosis were investigated. IH reduced HTR8/SVneo cell and EVT motility significantly, which could be partially attributed to the reduced secretion of matrix metalloproteinase 2. IH treatment blocked HTR8/SVneo cell proliferation significantly by modulating the expression of D-type Cyclins. IH also induced significant trophoblast cell apoptosis. Moreover, our study supports the premise that IH attenuates trophoblast cell motility and proliferation and induces excessive trophoblast cell apoptosis by specifically triggering the endoplasmic reticulum (ER) stress signaling pathway. Briefly, differing from the mechanism of trophoblast motility and proliferation inhibition, and apoptosis induction by hypoxia, IH is apt to weaken trophoblast viability mainly by activating the ER stress signaling pathway with a time-dependent pattern, which is further implicated in OSAS-associated adverse pregnancy outcomes.

Flow limitation/obstruction with recovery breath (FLOW) event for improved scoring of mild obstructive sleep apnea without electroencephalography

OBJECTIVE

Apnea/hypopnea index (AHI), especially without arousal criteria, does not adequately risk stratify patients with mild obstructive sleep apnea (OSA). We describe and test scoring reliability of an event, Flow Limitation/Obstruction With recovery breath (FLOW), representing obstructive airflow disruptions using only pressure transducer and snore signals available without electroencephalography.

METHODS

The following process was used (i) Development of FLOW event definition, (ii) Training period and definition refinement, and (iii) Reliability testing on 10 100-epoch polysomnography (PSG) samples and two 100-sample tests. Twenty full-night in-laboratory baseline PSGs in OSA patients with AHI with ≥4% desaturations <15 were rescored for FLOW events, traditional hypopneas with desaturations, respiratory-related arousal (RRA) events (hypopneas with arousals and respiratory-effort related arousals) and non-respiratory arousals (NRA).

RESULTS

Scoring of FLOW events in 100-epoch samples had good reliability with intraclass correlation (ICC) of 0.91. The overall kappa for presence of events on two sets of 100 sample events was 0.84 and 0.87 demonstrating good agreement. Moreover, 80% of RRA and 8% of NRA were concurrent with FLOW events. Furthermore, 56% of FLOW events were independent of RRA events. FLOW stratifies patients in traditional AHI categories with 50%/8% of AHI with ≥3% desaturations (AHI3) <5 and 12%/63% of AHI3 >5 in lowest/highest tertiles of AHI3 plus FLOW index.

CONCLUSIONS

Scoring of FLOW after training is reliable. FLOW scores a high proportion of RRA and many currently unrepresented obstructive airflow disruptions. FLOW allows for stratification within the current normal-mild OSA category, which may better identify patients who will benefit from treatment.

Mild Maternal Obstructive Sleep Apnea in Non-obese Pregnant Women and Accelerated Fetal Growth

The prevalence of obstructive sleep apnea (OSA) during pregnancy is rising. OSA during pregnancy has been associated with hypertensive disorders of pregnancy and gestational diabetes. The effect of maternal OSA on the fetus, particularly on fetal growth, is less apparent. Most of the currently available human data is based on non-objective assessment of OSA and includes heterogeneous populations with inadequate control on confounders, such as maternal obesity and pregnancy complications. Using objective tools in non-obese women with uncomplicated pregnancies, we aimed to investigate the association between maternal OSA and fetal growth. A total of 155 non-obese pregnant women were recruited. Birth-weight percentile of the newborns of women with mild OSA was significantly higher compared with the newborns of non-OSA controls (72% vs. 57%, respectively, P < 0.01). Birth-length and triceps thickness measurements were significantly higher among the newborns of women with OSA compared with controls (P = 0.02 for both). The proportion of large for gestational age (LGA) newborns was higher among women with OSA compared with controls (28% vs. 8%, respectively, P = 0.04). Our results suggest that maternal OSA during the third trimester of pregnancy - even in a mild form -is associated with accelerated fetal growth.

An Official American Thoracic Society Workshop Report: Noninvasive Identification of Inspiratory Flow Limitation in Sleep Studies

This report summarizes the proceedings of the American Thoracic Society Workshop on the Noninvasive Identification of Inspiratory Flow Limitation in Sleep Studies held on May 16, 2015, in Denver, Colorado. The goal of the workshop was to discuss methods for standardizing the scoring of flow limitation from nasal cannula pressure tracings. The workshop began with presentations on the physiology underlying flow limitation, existing methods of scoring flow limitation, the effects of signal acquisition and filtering on flow shapes, and a review of the literature examining the adverse outcomes related to flow limitation. After these presentations, the results from online scoring exercises, which were crowdsourced to workshop participants in advance of the workshop, were reviewed and discussed. Break-out sessions were then held to discuss potential algorithms for scoring flow limitation. Based on these discussions, subsequent online scoring exercises, and webinars after the workshop, a consensus-based set of recommendations for a scoring algorithm for flow limitation was developed. Key conclusions from the workshop were: (1) a standardized and automated approach to scoring flow limitation is needed to provide a metric of nonepisodic elevated upper airway resistance, which can then be related to clinical outcomes in large cohorts and patient groups; (2) at this time, the most feasible method for standardization is by proposing a consensus-based framework, which includes scoring rules, developed by experts (3) hardware and software settings of acquisition devices, including filter settings, affect the shape of the flow curve, and should be clearly specified; and (4) a priority for future research is the generation of an open-source, expert-derived training set to encourage and support validation of automated flow limitation scoring algorithms.

A Pilot Randomized-Controlled Trial on the Effect of CPAP Treatment on Glycemic Control in Gestational Diabetes: Study Design and Methods

Background: Gestational diabetes (GDM) is associated with adverse short- and long-term maternal and fetal outcomes. Observational data support a link between sleep-disordered breathing (SDB) during pregnancy and GDM. However, it is unknown whether treatment of SDB with continuous positive airway pressure (CPAP) improves glucose control in this patient population. In addition, CPAP adherence and feasibility as a treatment option in pregnancy is unknown. This pilot randomized, controlled trial aims to primarily determine the feasibility of CPAP treatment in pregnant women with SDB and GDM. This study is also investigating the effect of SDB treatment on 24-h glucose profiles as an exploratory outcome. Objectives: To describe the study methodology in this ongoing study of pregnant women with GDM and SDB. Patients and Methods: Pregnant women with GDM and SDB defined by apnea-hypopnea index (AHI) ≥10 (Chicago Scoring Criteria) on level 2 polysomnography are randomized to either auto titrating CPAP (experimental group) or a nasal dilator strip (control group) until delivery. The primary outcome, objectively-assessed adherence to CPAP, is measured over the course of the treatment period using device-specific software. Recruitment and retention rates will be calculated to assess the feasibility for planning future trials. Twenty-four hour glucose profiles are measured over a 72-h period using the continuous glucose monitoring (CGM) system, before and after the intervention. Conclusion: The results of this study will be highly informative to determine whether CPAP is a feasible treatment for pregnant women with GDM and SDB, a specialized population at risk for substantial comorbidity. The trial results will ultimately be useful in planning future SDB treatment trials in pregnancy and GDM. The study is registered on clinicaltrials.gov (NCT02245659).

Exploring the Abnormal Modulation of the Autonomic Systems during Nasal Flow Limitation in Upper Airway Resistance Syndrome by Hilbert-Huang Transform

Patients with nasal flow limitation and upper airway resistance syndrome (UARS) during sleep can present with low blood pressure and disturbing symptoms associated with hypervagotony. We hypothesized that the dynamic changes of the autonomic system related to inspiratory flow limitation can be quantified by the developed analytic technique applied on beat-to-beat heart rate (RR intervals) and finger photoplethysmography (PPG).

Síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) y embarazo

El embarazo es una condición temporal de la vida en la que ocurren importantes cambios en la fisiología de la mujer, los cuales se resuelven, en gran medida, después del parto. Hay cambios físicos, hormonales y psicológicos, con un aumento progresivo de peso. Estos factores pueden predisponer a un trastorno respiratorio del sueño o a exacerbar alguno ya existente. La literatura científica sugiere una mayor prevalencia de ronquido en las mujeres embarazadas. Las bases de datos demuestran que en menos del 1% de los embarazos aparece el código del diagnóstico de apnea de sueño. Se ha relacionado la presencia tanto de ronquido como de apnea durante el embarazo con algunos desenlaces adversos que se tratan en este artículo, el cual busca sensibilizar a los médicos para que consideren este diagnóstico durante el embarazo.

Sleep disordered breathing in pregnancy: the maternal and fetal implications

Sleep disordered breathing (SDB) which includes obstructive sleep apnoea (OSA) and upper airway resistance syndrome (UARS), has emerged as a risk factor for adverse maternal-foetal outcomes in pregnancy. Physiological changes of pregnancy predispose a woman 'at risk' towards developing SDB. The increasing incidence of OSA in pregnancy closely correlates with the population trends of obesity. Common screening tools validated in non-pregnant subjects including Epworth Sleepiness Scale (ESS) and Berlin Questionnaire (BQ) are poor predictors of SDB in pregnancy. Preeclampsia, gestational hypertension and gestational diabetes mellitus (GDM) are linked with SDB. Preeclampsia and OSA share common pathological associations. It is unclear if one predisposes the other. Foetal morbidity includes intrauterine growth restriction (IUGR), preterm delivery, low birth weight, neonatal intensive care unit (NICU) admission and Apgar score of less than seven at one minute. Continuous positive airway pressure (CPAP) is a well-documented treatment of SDB in pregnancy and has been shown to reverse some of the adverse events. It becomes imperative to diagnose and manage this condition as OSA causes substantial morbidity in the untreated pregnant patient and foetus. Three short clinical cases and a literature review on SDB on pregnancy are presented.

The role of flow limitation as an important diagnostic tool and clinical finding in mild sleep-disordered breathing

Obstructive sleep apnea (OSA) is defined by quantifying apneas and hypopneas along with symptoms suggesting sleep disruption. Subtler forms of sleep-disordered breathing can be missed when this criteria is used. Newer technologies allow for non-invasive detection of flow limitation, however consensus classification is needed. Subjects with flow limitation demonstrate electroencephalogram changes and clinical symptoms indicating sleep fragmentation. Flow limitation may be increased in special populations and treatment with nasal continuous positive airway pressure (CPAP) has been shown to improve outcomes. Titrating CPAP to eliminate flow limitation may be associated with improved clinical outcomes compared to treating apneas and hypopneas.

The Role of Obesity in Preeclampsia

The incidence of obesity is increasing at an alarming rate. There is compelling evidence that obesity increases the risk of preeclampsia about 3-fold, and in developed countries is the leading attributable risk for the disorder. In this presentation we explore this relationship and propose targets for future studies guided by the much more extensively studied relationship of obesity to cardiovascular disease. We further address the hypothesis that asymmetric dimethyl arginine (ADMA), an endogenous inhibitor of nitric oxide synthase, may be one convergence point for the mechanism by which obesity increases the risk of preeclampsia. We conclude with consideration of the clinical implications of this information.

Hypertension, snoring, and obstructive sleep apnoea during pregnancy: a cohort study

OBJECTIVE

To assess the frequency of obstructive sleep apnoea among women with and without hypertensive disorders of pregnancy.

DESIGN

Cohort study.

SETTING

Obstetric clinics at an academic medical centre.

POPULATION

Pregnant women with hypertensive disorders (chronic hypertension, gestational hypertension, or pre-eclampsia) and women who were normotensive.

METHODS

Women completed a questionnaire about habitual snoring and underwent overnight ambulatory polysomnography.

MAIN OUTCOME MEASURES

The presence and severity of obstructive sleep apnoea.

RESULTS

Obstructive sleep apnoea was found among 21 of 51 women with hypertensive disorders (41%), but in only three of 16 women who were normotensive (19%, chi-square test, P=0.005). [Author correction added on 16 June 2014, after first online publication: Results mentioned in the abstract were amended.] Non-snoring women with hypertensive disorders typically had mild obstructive sleep apnoea, but >25% of snoring women with hypertensive disorders had moderate to severe obstructive sleep apnoea. Among women with hypertensive disorders, the mean apnoea/hypopnoea index was substantially higher in snorers than in non-snorers (19.9±34.1 versus 3.4±3.1, P=0.013), and the oxyhaemoglobin saturation nadir was significantly lower (86.4±6.6 versus 90.2±3.5, P=0.021). Among women with hypertensive disorders, after stratification by obesity, the pooled relative risk for obstructive sleep apnoea in snoring women with hypertension compared with non-snoring women with hypertension was 2.0 (95% CI 1.4-2.8).

CONCLUSIONS

Pregnant women with hypertension are at high risk for unrecognised obstructive sleep apnoea. Although longitudinal and intervention studies are urgently needed, given the known relationship between obstructive sleep apnoea and hypertension in the general population, it would seem pertinent that hypertensive pregnant women who snore should be tested for obstructive sleep apnoea, a condition believed to cause or promote hypertension.

Obstructive sleep apnea in pregnancy: reliability of prevalence and prediction estimates

OBJECTIVE

We sought to ascertain the validity of two screening scales for obstructive sleep apnea (OSA) in pregnancy and to establish the prevalence of OSA in pregnancy.

STUDY DESIGN

In this prospective observational study, two screening scales were administered. Screen positive subjects were referred for diagnostic polysomnography (PSG); if admitted for antepartum care, screen positive subjects underwent a modified study with a type 3 device (T3D).

RESULT

A total of 1509 subjects underwent OSA screening; 58 completed diagnostic testing. Neither measure was a reliable diagnostic tool for OSA as determined by T3D or PSG (detection rates of 10.3% and 18.0%, respectively). Among screen positive subjects undergoing PSG or T3D testing, 15.5% ultimately met 'gold standard' OSA diagnostic criteria for an estimated point prevalence of 4.9%.

CONCLUSION

In this prospective trial, screening positive on the Berlin questionnaire or Epworth sleepiness scale was poorly predictive of OSA among gravidae and was associated with a high false referral rate.

Analysis of pulmonary function in high-risk pregnancies: a case-control study

OBJECTIVE

To evaluate the pulmonary function in high-risk pregnant women.

METHODS

This was a prospective cross-sectional study on 60 pregnant women, of whom 30 were high-risk and 30 were low-risk cases, with gestational age ≥28 weeks. For the high-risk group, preeclampsia and/or gestational diabetes were the conditions taken into consideration. To evaluate pulmonary function, the following parameters were assessed: forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), Tiffeneau index (FVC/FEV1) and forced expiratory flow (FEF25-75%). Fisher's exact test or the chi-square test was used to analyze the variables.

RESULTS

There were no statistical differences in the pulmonary function parameters according to gestational age (p > 0.05). Similarly, there were no statistical differences in the pulmonary function tests for the variables of smoking habit, birth weight, Apgar index, duration of gestation, childbirth type and need for the newborn to go to the intensive care unit (p > 0.05). For the pregnant women with preeclampsia and gestational diabetes, only FEF25-75% presented statistical significance (p = 0.01 and 0.034, respectively).

CONCLUSION

In high-risk pregnant women, pulmonary function suffered alterations characterized by limitations regarding airflow through the airways, although without repercussions on gestational outcome.

Association of adverse perinatal outcomes with screening measures of obstructive sleep apnea

OBJECTIVE

This prospective observational study explored the association of hypertensive disorders of pregnancy and small-for-gestational age with obstructive sleep apnea (OSA) as determined by screening measures for OSA and sleep studies.

STUDY DESIGN

Two symptom-based screening questionnaires, the Berlin Questionnaire (BQ) and the Epworth Sleepiness Scale (ESS), were administered to enroll 1509 gravidae. Screen-positive subjects were referred for polysomnography. The primary outcome was the occurrence of either gestational hypertension or preeclampsia. Generalized linear models (GLM) were used to estimate the relative risks of associations.

RESULT

One thousand one hundred and fifty-seven subjects were available for outcomes analysis. Screening positive on the BQ was positively associated with hypertensive disorders in GLM models (adjusted relative risk=1.90, 95% confidence interval 1.52 to 2.37).

CONCLUSION

In this large prospective trial, GLM modeling suggests that the BQ but not the ESS demonstrated significant association with measured adverse pregnancy outcomes, and specific items predicted these outcomes better than others. However, causative association of BQ with OSA cannot be assumed.

Airflow limitations in pregnant women suspected of sleep-disordered breathing

BACKGROUND AND AIM

Pregnancy physiology may predispose women to the development of airflow limitations during sleep. The goal of this study was to evaluate whether pregnant women suspected of sleep-disordered breathing (SDB) are more likely to have airflow limitations compared to non-pregnant controls.

METHODS

We recruited pregnant women referred for polysomnography for a diagnosis of SDB. Non-pregnant female controls matched for age, body mass index (BMI), and apnoea-hypopnoea index (AHI) were identified from a database. We examined airflow tracings for changes in amplitude and shape. We classified airflow limitation by (a) amplitude criteria defined as decreased airflow of > or =10 s without desaturation or arousal (FL 10), or decreased airflow of any duration combined with either 1-2% desaturation or arousal, (FL 1-2%); and (b) shape criteria defined as the presence of flattening or oscillations of the inspiratory flow curve.

RESULTS

We identified 25 case-control pairs. Mean BMI was 44.0±6.9 in cases and 44.1±7.3 in controls. Using shape criteria, pregnant women had significantly more flow-limited breaths throughout total sleep time (32.4±35.8 vs. 9.4±17.9, p<0.0001) and in each stage of sleep (p<0.0001) than non-pregnant controls. In a subgroup analysis, pregnant women without a diagnosis of obstructive sleep apnoea (OSA) who had an AHI <5 had similar findings (p<0.0001). There was no difference in airflow limitation by amplitude criteria between pregnant women and controls (p=0.22).

CONCLUSIONS

Pregnant women suspected of OSA have more frequent shape-defined airflow limitations than non-pregnant controls, even when they do not meet polysomnographic OSA criteria.

Maternal sleep-disordered breathing and adverse pregnancy outcomes: a systematic review and metaanalysis

OBJECTIVE

Symptoms of sleep-disordered breathing (SDB) are increased in pregnancy compared to the nongravid state. Maternal SDB may be associated with adverse pregnancy outcomes, but this is still under investigation. We performed a systematic literature review, and where feasible, a metaanalysis, to evaluate whether women with SDB in pregnancy have a higher risk of specific adverse pregnancy outcomes compared with women without SDB.

STUDY DESIGN

Original studies published until June 2012 evaluating the association between gestational hypertension/preeclampsia, gestational diabetes, low birthweight infants, and maternal SDB, defined either by symptoms or the reference standard polysomnography, were identified from PubMed, EMBASE, and Web of Science. Data were extracted on study design and outcome estimates. When appropriate, effect estimates from each study were pooled using a random-effects model.

RESULTS

Of the 4386 studies identified, 31 met the defined criteria. Twenty-one studies, all observational in design, reported dichotomous outcomes; 9 of these adjusted for potential confounders. Maternal SDB was significantly associated with gestational hypertension/preeclampsia (pooled adjusted odds ratio [aOR], 2.34; 95% confidence interval [CI], 1.60-3.09; 5 studies), and gestational diabetes (pooled aOR, 1.86; 95% CI, 1.30-2.42; 5 studies).

CONCLUSION

Based on published observational studies to date, maternal SDB is associated with an increased risk of gestational hypertension and gestational diabetes after adjusting for potential confounders. However, large-scale, prospective cohort, and interventional studies are needed to further elucidate the relationship between maternal SDB and adverse pregnancy outcomes.

Sleep and pregnancy-induced hypertension: a possible target for intervention?

Sleep disturbances in the general population are associated with elevated blood pressure. This may be due to several mechanisms, including sympathetic activation and hypothalamic-pituitary-adrenal (HPA) axis disturbance. Elevated blood pressure in pregnancy can have devastating effects on both maternal and fetal health and is associated with increased risk for preeclampsia and poor delivery outcomes. Preliminary evidence suggests that mechanisms linking sleep and blood pressure in the general population may also hold in the pregnant population. However, the effects of disturbed sleep on physiologic mechanisms that may directly influence blood pressure in pregnancy have not been well studied. The role that sleep disturbance plays in gestational blood pressure elevation and its subsequent consequences warrant further investigation. This review evaluates the current literature on sleep disturbance and elevated blood pressure in pregnancy and proposes possible treatment interventions.

Risk factors for sleep-disordered breathing in pregnancy

RATIONALE

Symptoms of sleep-disordered breathing (SDB) are common among pregnant women, and several studies link SDB symptoms with gestational hypertension and preeclampsia. However, few prospective studies objectively measuring SDB during pregnancy have been performed.

OBJECTIVES

We performed a prospective cohort study examining risk factors for third trimester SDB in pregnant women.

MEASUREMENTS AND METHODS

105 pregnant women from the Hospital of the University of Pennsylvania obstetrics practices completed first and third trimester overnight polysomnography studies. We examined whether the number of SDB events per hour of sleep increased during pregnancy. We performed unadjusted and multivariable logistic regression analyses to estimate the effects of usual and pregnancy-specific characteristics on development of third trimester obstructive sleep apnoea (OSA). In secondary analyses, we examined the relationship between objectively measured SDB, hypertensive disorders of pregnancy, and other adverse maternal-fetal outcomes.

MAIN RESULTS

Mean Apnoea-Hypopnoea Index increased from 2.07 (SD 3.01) events/h at baseline (first trimester) to 3.74 (SD 5.97) in the third trimester (p=0.009). 10.5% of women had OSA in the first trimester. By the third trimester, 26.7% of women had OSA. In multivariable analyses, first trimester body mass index (BMI) and maternal age were significantly associated with third trimester OSA.

CONCLUSIONS

Third trimester OSA is common. Risk factors for third trimester OSA among women without baseline SDB include higher baseline BMI and maternal age.

Inspiratory flow limitation in a normal population of adults in São Paulo, Brazil

STUDY OBJECTIVES

Inspiratory flow limitation (IFL) during sleep occurs when airflow remains constant despite an increase in respiratory effort. This respiratory event has been recognized as an important parameter for identifying sleep breathing disorders. The purpose of this study was to investigate how much IFL normal individuals can present during sleep.

DESIGN

Cross-sectional study derived from a general population sample.

SETTING

A "normal" asymptomatic sample derived from the epidemiological cohort of São Paulo.

PATIENTS AND PARTICIPANTS

This study was derived from a general population study involving questionnaires and nocturnal polysomnography of 1,042 individuals. A subgroup defined as a nonsymptomatic healthy group was used as the normal group.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

All participants answered several questionnaires and underwent full nocturnal polysomnography. IFL was manually scored, and the percentage of IFL of total sleep time was considered for final analysis. The distribution of the percentage of IFL was analyzed, and associated factors (age, sex, and body mass index) were calculated. There were 95% of normal individuals who exhibited IFL during less than 30% of the total sleep time. Body mass index was positively associated with IFL.

CONCLUSIONS

Inspiratory flow limitation can be observed in the polysomnography of normal individuals, with an influence of body weight on percentage of inspiratory flow limitation. However, only 5% of asymptomatic individuals will have more than 30% of total sleep time with inspiratory flow limitation. This suggests that only levels of inspiratory flow limitation > 30% be considered in the process of diagnosing obstructive sleep apnea in the absence of an apnea-hypopnea index > 5 and that < 30% of inspiratory flow limitation may be a normal finding in many patients.

Common sleep disorders: management strategies and pregnancy outcomes

Sleep disorders, prevalent in industrialized countries, are associated with adverse health outcomes such as hypertension, diabetes, and obesity. Disturbed sleep during pregnancy is frequently overlooked by health care providers, yet recent studies suggest there is an association between sleep disorders and adverse pregnancy outcomes, including preeclampsia, elevated serum glucose, depression, prolonged labor, and cesarean birth. Growing evidence indicates that the recognition and management of prenatal sleep disorders may minimize adverse pregnancy outcomes and improve maternal and fetal well-being. This focused review of prenatal sleep disturbance literature suggests there are 3 main sleep disorders of interest: breathing-related sleep disorders (ie, habitual snoring and obstructive sleep apnea), restless legs syndrome, and insomnia. These sleep disorders are common in pregnancy and have maternal and fetal consequences if left untreated. This article describes sleep disorders of pregnancy, elucidates their relationship with maternal and neonatal outcomes, and presents current evidence regarding diagnostic and management strategies.

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.

Sleep-disordered breathing and daytime napping are associated with maternal hyperglycemia

OBJECTIVES

Sleep disturbances in pregnancy may impair glucose mechanism. This study aimed to examine associations of sleep-disordered breathing, sleep, and nap duration with 1-h glucose challenge test (GCT) levels in pregnant women after controlling for known risk factors for gestational diabetes.

METHODS

This is a case-control study of 104 pregnant women. All women underwent full polysomnography and a GCT and completed the multivariable apnea prediction and Pittsburgh Sleep Quality indexes. The primary outcome was maternal hyperglycemia measured by GCT. Bivariate and multivariable logistic regression analyses were performed.

RESULTS

Over 13 % subjects reported habitual snoring in the first trimester. Only 9.3 % women with normoglycemia (GCT < 135) were habitual snorers, whereas 45.5 % women with hyperglycemia (GCT ≥ 135) had habitual snoring (p < 0.001). Sleep-disordered breathing symptoms (loud snoring, snorting/gasping, and apneas) (odds ratio (OR) 2.85; 95 % confidence interval (CI) 1.50-5.41; p = 0.001) and total nap duration (OR 1.48; 95 % CI 0.96-2.28; p = 0.08) were associated with hyperglycemia. After adjusting for confounders, sleep-disordered breathing symptoms (OR 3.37; 95 % CI 1.44-8.32; p = 0.005) and nap duration (OR 1.64; 95 % CI 1.00-2.681.02; p = 0.05) continued to be associated with hyperglycemia. However, the primary exposure measure, the apnea/hypopnea index in the first trimester was not significantly associated with hyperglycemia (OR 1.03; 95 % CI 0.83-1.28; p = 0.77).

CONCLUSIONS

Sleep-disordered breathing symptoms and nap duration are associated with hyperglycemia. Sleep duration was not associated with hyperglycemia. Research is needed concerning whether women with sleep-disordered breathing and/or daytime napping are at risk for gestational diabetes.

Treatment of sleep disordered breathing reverses low fetal activity levels in preeclampsia

STUDY OBJECTIVES

Preeclampsia affects 5% to 7% of pregnancies, is strongly associated with low birth weight and fetal death, and is accompanied by sleep disordered breathing. We hypothesized that sleep disordered breathing may link preeclampsia with reduced fetal movements (a marker of fetal health), and that treatment of sleep disordered breathing might improve fetal activity during sleep.

DESIGN, SETTING, AND PARTICIPANTS

First, a method of fetal movement recording was validated against ultrasound in 20 normal third trimester pregnancies. Second, fetal movement was measured overnight with concurrent polysomnography in 20 patients with preeclampsia and 20 control subjects during third trimester. Third, simultaneous polysomnography and fetal monitoring was done in 10 additional patients with preeclampsia during a control night and during a night of nasal CPAP.

INTERVENTION

Overnight continuous positive airway pressure.

MEASUREMENTS AND RESULTS

Women with preeclampsia had inspiratory flow limitation and an increased number of oxygen desaturations during sleep (P = 0.008), particularly during REM sleep. Preeclampsia was associated with reduced total fetal movements overnight (319 [SD 32]) versus controls (689 [SD 160], P < 0.0001) and a change in fetal movement patterns. The number of fetal hiccups was also substantially reduced in preeclampsia subjects (P < 0.0001). Continuous positive airway pressure treatment increased the number of fetal movements and hiccups (P < 0.0001 and P = 0.0002, respectively).

CONCLUSIONS

The effectiveness of continuous positive airway pressure in improving fetal movements suggests a pathogenetic role for sleep disordered breathing in the reduced fetal activity and possibly in the poorer fetal outcomes associated with preeclampsia.

Validation of Watch-PAT-200 against polysomnography during pregnancy

STUDY OBJECTIVES

To determine the relationships between key variables obtained from ambulatory polysomnography (PSG) and the wrist-worn Watch-PAT 200 device in pregnant women.

METHODS

In this prospective cohort study, women in their third trimester of pregnancy underwent full overnight home PSG using the 22-channel MediPalm system and the Watch-PAT 200 device. PSGs were scored by a blinded, experienced technologist using AASM 2007 criteria; the Watch-PAT was scored automatically by the manufacturer's proprietary software.

RESULTS

A total of 31 pregnant women were studied. Mean age was 30.2 ± 7.1 years; mean gestational age was 33.4 ± 3.0 weeks; mean BMI was 31.9 ± 8.1 kg/m(2); 39% of women were nulliparous. Key variables generated by PSG and Watch-PAT correlated well over a wide range, including the apnea-hypopnea index (AHI, r = 0.76, p < 0.001); respiratory disturbance index (RDI, r = 0.68, p < 0.001), mean oxygen saturation (r = 0.94, p < 0.001), and minimum oxygen saturation (r = 0.88, p < 0.001). The area under the curve for AHI ≥ 5 and RDI ≥ 10 were 0.96 and 0.94, respectively. Association between stage 3 sleep on PSG and deep sleep on Watch-PAT was poor. Watch-PAT tended to overscore RDI, particularly as severity increased.

CONCLUSIONS

Among pregnant women, Watch-PAT demonstrates excellent sensitivity and specificity for identification of obstructive sleep apnea, defined as AHI ≥ 5 on full PSG. Watch-PAT may overestimate RDI somewhat, especially at high RDI values.

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.