Normal oxyhemoglobin saturation during sleep. How low does it go?

Effects of moderate alcohol consumption and hypobaric hypoxia: implications for passengers' sleep, oxygen saturation and heart rate on long-haul flights

BACKGROUND

Passengers on long-haul flights frequently consume alcohol. Inflight sleep exacerbates the fall in blood oxygen saturation (SpO2) caused by the decreased oxygen partial pressure in the cabin. We investigated the combined influence of alcohol and hypobaric hypoxia on sleep, SpO2 and heart rate.

METHODS

Two groups of healthy individuals spent either two nights with a 4-hour sleep opportunity (00:00-04:00 hours) in the sleep laboratory (n=23; 53 m above sea level) or in the altitude chamber (n=17; 753 hPa corresponding to 2438 m above sea level, hypobaric condition). Participants consumed alcohol before one of the nights (mean±SE blood alcohol concentration 0.043±0.003%). The order of the nights was counterbalanced. Two 8-hour recovery nights (23:00-07:00 hours) were scheduled between conditions. Polysomnography, SpO2 and heart rate were recorded.

RESULTS

The combined exposure to alcohol and hypobaric condition decreased SpO2 to a median (25th/75th percentile) of 85.32% (82.86/85.93) and increased heart rate to a median (25th/75th percentile) of 87.73 bpm (85.89/93.86) during sleep compared with 88.07% (86.50/88.49) and 72.90 bpm (70.90/78.17), respectively, in the non-alcohol hypobaric condition, 94.97% (94.59/95.33) and 76.97 bpm (65.17/79.52), respectively, in the alcohol condition and 95.88% (95.72/96.36) and 63.74 bpm (55.55/70.98), respectively, in the non-alcohol condition of the sleep laboratory group (all p<0.0001). Under the combined exposure SpO2 was 201.18 min (188.08/214.42) below the clinical hypoxia threshold of 90% SpO2 compared with 173.28 min (133.25/199.03) in the hypobaric condition and 0 min (0/0) in both sleep laboratory conditions. Deep sleep (N3) was reduced to 46.50 min (39.00/57.00) under the combined exposure compared with both sleep laboratory conditions (alcohol: 84.00 min (62.25/92.75); non-alcohol: 67.50 min (58.50/87.75); both p<0.003).

CONCLUSIONS

The combination of alcohol and inflight hypobaric hypoxia reduced sleep quality, challenged the cardiovascular system and led to extended duration of hypoxaemia (SpO2 <90%).

Assessing the contribution of mild high-altitude exposure to obstructive sleep apnea-hypopnea syndrome comorbidities

Background

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common sleep disorder. The lower atmospheric pressure and decreased oxygen levels of high-altitude areas can exacerbate the severity of OSAHS, but research into OSAHS in high-altitude areas remains limited. This study, from June 2015 to January 2020, involved 4,667 patients with suspected OSAHS and 38 healthy volunteers. The non-OSAHS group (AHI <5/h) had 395 patients, while the larger OSAHS group (AHI ≥5/h) comprised 4,272 patients. The significant size difference between the groups emphasized the study's focus on OSAHS, using the non-OSAHS mainly for comparison.

Methods

Sleep technicians monitored the OSAHS patient group overnight by polysomnography (PSG), the apnea-hypopnea index (AHI), the mean oxygen saturation (MSpO2), lowest oxygen saturation (LSpO2), the oxygen desaturation index (ODI) and the total sleep time with oxygen saturation less than 90% (TST-SpO2 <90%). Healthy volunteers self-monitored sleep patterns at home, using the CONTEC RS01 respiration sleep monitor with a wristwatch sleep apnea screen meter. The RSO1 wristwatch-style device has already been studied for consistency and sensitivity with the Alice-6 standard multi-lead sleep monitor and can be used for OSAHS screening in this region.

Results

LSpO2 recordings from healthy volunteers (86.36 ± 3.57%) and non-OSAHS (AHI <5/h) cohort (78.59 ± 11.99%) were much lower than previously reported normal values. Regression analysis identified no correlations between AHI levels and MSpO2 or TST-SpO2 <90%, weak correlations between AHI levels and LSpO2 or MSpO2, and a strongly significant correlation between AHI levels and the ODI (r = 0.76, p < 0.05). The data also indicated that the appropriate clinical thresholds for OSAHS patients living at mild high altitude are classified as mild, moderate, or severe based on LSpO2 saturation criteria of 0.85-0.90, 0.65-0.84, or <0.65, respectively.

Conclusion

The study findings suggest that individuals with an AHI score below 5 in OSAHS, who reside in high-altitude areas, also require closer monitoring due to the elevated risk of nocturnal hypoxia. Furthermore, the significant correlation between ODI values and the severity of OSAHS emphasizes the importance of considering treatment options. Additionally, the assessment of hypoxemia severity thresholds in OSAHS patients living in high-altitude regions provides valuable insights for refining diagnostic guidelines.

Nocturnal Hypoxemia Associates With Symptom Progression and Mortality in Patients With Progressive Fibrotic Interstitial Lung Disease

BACKGROUND

OSA and nocturnal hypoxemia (NH) are common in patients with fibrotic interstitial lung disease (F-ILD), but their relationship with disease outcomes remains unclear.

RESEARCH QUESTION

What is the relationship between NH and OSA and clinical outcomes in patients with F-ILD?

STUDY DESIGN AND METHODS

This was a prospective observational cohort study of patients with F-ILD and without daytime hypoxemia. Patients underwent home sleep study at baseline and were followed up for at least 1 year or until death. NH was defined as ≥ 10% of sleep with oxygen saturation of < 90%. OSA was defined as an apnea-hypopnea index of ≥ 15 events/h.

RESULTS

Among 102 participants (male, 74.5%; age, 73.0 ± 8.7 years; FVC, 2.74 ± 0.78 L; 91.1% idiopathic pulmonary fibrosis), 20 patients (19.6%) demonstrated prolonged NH and 32 patients (31.4%) showed OSA. No significant differences were found between those with and without NH or OSA at baseline. Despite this, NH was associated with a more rapid decline in both quality of life as measured by the King's Brief Interstitial Lung Disease questionnaire (change, -11.3 ± 5.3 points in the NH group vs -6.7 ± 6.5 in those without NH; P = .005) and higher all-cause mortality at 1 year (hazard ratio, 8.21; 95% CI, 2.40-28.1; P < .001). No statistically significant difference was seen between the groups in annualized change in measures of pulmonary function testing.

INTERPRETATION

Prolonged NH, but not OSA, is associated with worsening disease-related quality of life and increased mortality in patients with F-ILD.

Thoracic Society of Australia and New Zealand Position Statement on Acute Oxygen Use in Adults: 'Swimming between the flags'

Oxygen is a life-saving therapy but, when given inappropriately, may also be hazardous. Therefore, in the acute medical setting, oxygen should only be given as treatment for hypoxaemia and requires appropriate prescription, monitoring and review. This update to the Thoracic Society of Australia and New Zealand (TSANZ) guidance on acute oxygen therapy is a brief and practical resource for all healthcare workers involved with administering oxygen therapy to adults in the acute medical setting. It does not apply to intubated or paediatric patients. Recommendations are made in the following six clinical areas: assessment of hypoxaemia (including use of arterial blood gases); prescription of oxygen; peripheral oxygen saturation targets; delivery, including non-invasive ventilation and humidified high-flow nasal cannulae; the significance of high oxygen requirements; and acute hypercapnic respiratory failure. There are three sections which provide (1) a brief summary, (2) recommendations in detail with practice points and (3) a detailed explanation of the reasoning and evidence behind the recommendations. It is anticipated that these recommendations will be disseminated widely in structured programmes across Australia and New Zealand.

Asthma and obstructive sleep apnoea in adults and children - an up-to-date review

Obstructive sleep apnoea (OSA) and asthma are two common respiratory disorders in children and adults. Apart from common risk factors, such as obesity, gastroesophageal reflux disease and allergic rhinitis, emerging evidence suggest that the two diseases may complicate the clinical course of each other. On one hand, OSA modifies asthmatic airway inflammation and is associated with poor asthma control. On the other hand, asthma and its medications increase the collapsibility of the upper airways contributing to the development and worsening of OSA. The overnight respiratory symptoms of OSA and asthma are often similar, and an inpatient polysomnography is often necessary for a proper diagnosis, especially in children. Continuous positive pressure, the gold standard treatment for OSA can improve asthma control in patients suffering from both diseases. However, there is limited evidence how anti-asthma medications act in the same patients. Nevertheless, adenotonsillectomy seems to be effective in children with concomitant asthma and OSA. This review summarises the evidence for the bidirectional link between asthma and OSA, focuses on diagnostic and therapeutic challenges and highlights the need for further research.

Sleep-Induced Hypoxia under Flight Conditions: Implications and Countermeasures for Long-Haul Flight Crews and Passengers

PURPOSE

Recuperation during sleep on board of commercial long-haul flights is a safety issue of utmost importance for flight crews working extended duty periods. We intended to explore how sleep and blood oxygenation (in wake versus sleep) are affected by the conditions in an airliner at cruising altitude.

METHODS

Healthy participants' sleep was compared between 4-h sleep opportunities in the sleep laboratory (n = 23; sleep lab, ie, 53 m above sea level) and in an altitude chamber (n = 20; flight level, ie, 753 hPa, corresponding to 2438 m above sea level). A subgroup of 12 participants underwent three additional conditions in the altitude chamber: 1) 4-h sleep at ground level, 2) 4-h sleep at flight level with oxygen partial pressure equivalent to ground level, 3) 4-h monitored wakefulness at flight level. Sleep structure and blood oxygenation were analysed with mixed ANOVAs.

RESULTS

Total sleep time at flight level compared to in the sleep laboratory was shorter (Δ mean ± standard error -11.1 ± 4.2 min) and included less N3 sleep (Δ -17.6 ± 5.4 min), while blood oxygenation was decreased. Participants spent 69.7% (± 8.3%) of the sleep period time but only 13.2% (± 3.0%) of monitored wakefulness in a hypoxic state (<90% oxygen saturation). Oxygen enrichment of the chamber prevented oxygen desaturation.

CONCLUSION

Sleep - but not wakefulness - under flight conditions induces hypobaric hypoxia which may contribute to impaired sleep. The results caution against the assumption of equivalent crew recovery in-flight and on the ground but hold promise for oxygen enrichment as a countermeasure. The present results have implications for flight safety and possible long-term consequences for health in crews.

Changes in Sleep Quality Following Treatment for Chronic Rhinosinusitis: A Systematic Review and Meta-Analysis

BACKGROUND

Chronic rhinosinusitis (CRS) presents with broad and systemic manifestations, including impaired sleep; however, the impact of CRS treatments upon sleep is unknown.

OBJECTIVE

To establish the effect of medical or surgical CRS treatment on subjective and objective sleep metrics for patients not previously diagnosed with sleep apnea.

METHODS

Review of PubMed, Scopus, Web of Science, and the Cochrane Library was performed from the databases' date of inception through August 13, 2020, for studies evaluating the effect of CRS treatment on sleep quality. All studies reporting on subjective and objective sleep parameters for patients with CRS, with completed pre- and posttreatment data were included. Studies composed of patients with diagnosed sleep apnea were excluded.

RESULTS

Sixteen unique studies reporting data on a total of 1770 patients (mean age, 50.6 ± 15.6 (n = 1675) years) following treatment for CRS were included. Patient-reported outcome measures, Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, and Fatigue Severity Scale, demonstrated mean posttreatment differences of -2.8 (95% CI: -4.9 to -0.7), -2.4 (95% CI: -3.7 to -1.2), and -1.2 (95% CI: -1.6 to -0.7), respectively. The SNOT-22 and its sleep domain demonstrated a mean posttreatment difference of -23.5 (95% CI: -31.7 to -15.3) and -5.4 (95% CI: -6.8 to -4.0), respectively. EpSS, FSS and SNOT-22 exceeded their respective reported MCID values. Objective findings did not significantly change with treatment; mean difference: AHI: 0.7 (95% CI: -1.5 to 2.9), oxygen nadir: 0.3 (95% CI: -0.4 to 0.9).

CONCLUSIONS

Treatment of CRS may lead to clinically meaningful reduction in disease burden and improvements in both overall sleep quality and patient-reported fatigue. Despite clinically meaningful quality of life improvements, objective sleep parameters did not demonstrate corresponding posttreatment improvements.

Impact of Treatment for Nasal Cavity Disorders on Sleep Quality: Systematic Review and Meta-analysis

OBJECTIVE

To determine the impact of treatment for patients with nasal obstruction secondary to allergic rhinitis (AR) and nasal septal deviation (NSD) on sleep quality.

DATA SOURCES

Primary studies were identified though PubMed, Scopus, Cochrane Library, and Web of Science.

REVIEW METHODS

A systematic review was performed by querying databases for articles published through August 2020. Studies were included that reported on objective sleep parameters (apnea-hypopnea index) and sinonasal and sleep-specific patient-reported outcome measures: Rhinoconjunctivitis Quality of Life Questionnaire, Nasal Obstruction Symptom Evaluation, Epworth Sleepiness Scale (EpSS), and Pittsburgh Sleep Quality Index (PSQI).

RESULTS

The database search yielded 1414 unique articles, of which 28 AR and 7 NSD studies were utilized for meta-analysis. A total of 9037 patients (8515 with AR, 522 with NSD) were identified with a mean age of 35.0 years (35.3 for AR, 34.0 for NSD). Treatment for AR and NSD significantly improved subjective sleep quality. For AR, the EpSS mean difference was -1.5 (95% CI, -2.4 to -0.5; P = .002) and for the PSQI, -1.7 (95% CI, -2.1 to -1.2; P < .00001). For NSD, the EpSS mean difference was -3.2 (95% CI, -4.2 to -2.2; P < .00001) and for the PSQI, -3.4 (95% CI, -6.1 to -0.6; P = .02).

CONCLUSION

Subjective sleep quality significantly improved following treatment for AR and NSD. There were insufficient data to demonstrate that objective metrics of sleep quality similarly improved.

Effect of the new dual orexin receptor antagonist daridorexant on nighttime respiratory function and sleep in patients with mild and moderate obstructive sleep apnea

In this randomized, double-blind, placebo-controlled, two-period crossover study, the effect of the dual orexin receptor antagonist daridorexant was evaluated on nighttime respiratory function and sleep in 28 patients with mild and moderate obstructive sleep apnea (OSA). In each period, 50 mg daridorexant or placebo was administered every evening for 5 days. The primary endpoint was apnea/hypopnea index (AHI) during total sleep time (TST) after the last dosing. Other endpoints included peripheral oxygen saturation (SpO2), sleep duration, latency to persistent sleep (LPS), wake after sleep onset (WASO), and sleep efficiency index (SEI). Pharmacokinetics, safety, and tolerability were also assessed. The mean treatment difference for AHI during TST (i.e. daridorexant - placebo) after the last dosing was 0.74 events/hour (90% confidence interval [CI]: -1.43, 2.92). The corresponding treatment difference for SpO2 during TST was 0.16% [90% CI: -0.21, 0.53]. Overall, there was no clinically relevant effect of daridorexant on AHI or SpO2-related data after single and repeated dosing irrespective of sleep phase (i.e. rapid eye movement [REM] vs non-REM). Moreover, after single and repeated dosing, daridorexant prolonged TST by 39.6 minutes (90% CI: 16.9, 62.3) and 38.8 minutes (19.7, 57.9), respectively, compared with placebo and favorably modulated other sleep-related endpoints (i.e. increased SEI, decreased WASO, and shortened LPS). It attained expected plasma concentrations and was well tolerated in patients with mild and moderate OSA. These results indicate that single and repeated doses of 50 mg daridorexant do not impair nighttime respiratory function and improve sleep in patients with mild and moderate OSA. Clinical Trial Registration: ClinicalTrials.gov NCT03765294. A study to investigate the effects of ACT-541468 on nighttime respiratory function in patients with mild to moderate obstructive sleep apnea. https://clinicaltrials.gov/ct2/show/ NCT03765294.

Effect of the novel dual orexin receptor antagonist daridorexant on night-time respiratory function and sleep in patients with moderate chronic obstructive pulmonary disease

In patients with chronic obstructive pulmonary disease (COPD), sleep is often fragmented while, conversely, the use of sleep medications is of concern in these patients due to potential impairment of nocturnal breathing. This randomised, double-blind, placebo-controlled, two-period crossover study was conducted to evaluate the effect of the new dual orexin receptor antagonist daridorexant on night-time respiratory function and sleep in patients with moderate COPD. In each period, the highest Phase-III dose of 50 mg daridorexant or placebo was administered once daily in the evening for 5 consecutive days. The primary endpoint was peripheral oxygen saturation (SpO₂ ) during total sleep time (TST) after last dosing. Night-time respiratory function and sleep were further evaluated based on the apnea-hypopnea index (AHI), sleep duration, and objective sleep parameters. Pharmacokinetics, safety, and tolerability were also assessed. Primary endpoint analysis revealed no significant mean treatment difference (i.e. daridorexant - placebo) for SpO₂ during TST as it was 0.18% (90% confidence interval: -0.21 to 0.57). There was also no difference from placebo for SpO₂ during non-rapid eye movement (REM) and REM sleep at Night 5 and after first dosing. The AHI was slightly increased compared to placebo, but not to a clinically meaningful extent. In addition, daridorexant improved objective sleep parameters (i.e. prolonged TST, increased sleep efficiency, and decreased wake after sleep onset), reached expected plasma concentrations, and was safe and well tolerated. In conclusion, single and multiple doses of 50 mg daridorexant do not impair night-time respiratory function and improves sleep in patients with moderate COPD.

A Review of Cerebral Hemodynamics During Sleep Using Near-Infrared Spectroscopy

Investigating cerebral hemodynamic changes during regular sleep cycles and sleep disorders is fundamental to understanding the nature of physiological and pathological mechanisms in the regulation of cerebral oxygenation during sleep. Although sleep neuroimaging methods have been studied and have been well-reviewed, they have limitations in terms of technique and experimental design. Neurologists are convinced that Near-infrared spectroscopy (NIRS) provides essential information and can be used to assist the assessment of cerebral hemodynamics, and numerous studies regarding sleep have been carried out based on NIRS. Thus, a brief historical overview of the sleep studies using NIRS will be helpful for the biomedical students, academicians, and engineers to better understand NIRS from various perspectives. In this study, the existing literature on sleep studies is reviewed, and an overview of the NIRS applications is synthesized and provided. The paper first reviews the application scenarios, as well as the patterns of fluctuation of NIRS, which includes the investigation in regular sleep and sleep-disordered breathing. Various factors such as different sleep stages, populations, and degrees of severity were considered. Furthermore, the experimental design and signal processing, as well as the regulation mechanisms involved in regular and pathological sleep, are investigated and discussed. The strengths and weaknesses of the existing NIRS applications are addressed and presented, which can direct further NIRS analysis and utilization.

Rhinologic disease and its impact on sleep: a systematic review

BACKGROUND

Rhinologic disease can be responsible for systemic symptoms affecting mood, cognition, and sleep. It is unclear whether sleep disturbance in specific rhinologic disorders (chronic rhinosinusitis [CRS], rhinitis, and nasal septal deviation [NSD]) is an obstructive phenomenon or due to other mechanisms. In this review we examine the impact of CRS, rhinitis, and NSD on objective and subjective sleep outcome metrics and draw comparisons to normal controls and patients with known obstructive sleep apnea (OSA).

METHODS

A systematic review of 4 databases (PubMed, Scopus, Cochrane Library, and Web of Science) was performed. Studies reporting on objective (apnea-hypopnea index [AHI], respiratory disturbance index [RDI], oxygen nadir) and subjective (Epworth Sleepiness Scale [EpSS], Pittsburgh Sleep Quality Index [PSQI], Fatigue Severity Scale [FSS]) sleep parameters and disease-specific patient-reported outcome measures (PROMs; 22-item Sino-Nasal Outcome Test [SNOT-22], Rhinoconjunctivitis Quality of Life Questionnaire [RQLQ], Nasal Obstruction Symptom Evaluation [NOSE]) were included.

RESULTS

The database search yielded 1414 unique articles, of which 103 were included for analysis. Baseline PROMs were at the high end of normal to abnormal for all 3 conditions: EpSS: CRS (9.8 ± 4.0), rhinitis (9.7 ± 4.3), and NSD (8.9 ± 4.6); and PSQI: CRS (11.0 ± 4.5), rhinitis (6.1 ± 3.7), and NSD (8.6 ± 3.5). Objective measures demonstrated a mild to moderate OSA in the studied diseases: AHI: CRS (10.4 ± 11.5), rhinitis (8.6 ± 8.8), and NSD (13.0 ± 6.9). There were significant differences when compared with reported norms in all measured outcomes (p < 0.001).

CONCLUSION

Sleep quality is impacted by rhinologic (CRS, rhinitis, NSD) disease. There is likely a mild obstructive component contributing to poor sleep, but other contributing factors may be involved.

Sleep disordered breathing and chronic obstructive pulmonary disease: a narrative review on classification, pathophysiology and clinical outcomes

Chronic obstructive pulmonary disease (COPD) causes load-capacity-drive imbalance in both wakefulness and sleep, principally driven by expiratory flow limitation and hyperinflation. Sleep imposes additional burdens to the respiratory muscle pump, driven by changes in respiratory muscle tone, neural respiratory drive and consequences of the supine position. COPD patients are therefore at higher risk of decompensation during sleep, which may manifest as altered sleep architecture, isolated nocturnal desaturation, sleep hypoventilation and restless legs. Each form of sleep disordered breathing in COPD is associated with adverse clinical and patient-reported outcomes, including increased risk of exacerbations, hospitalisation, cardiovascular events, reduced survival and poorer quality of life. COPD-obstructive sleep apnoea (OSA) overlap syndrome represents a distinct clinical diagnosis, in which clinical outcomes are significantly worse than in either disease alone, including increased mortality, risk of cardiovascular events, hospitalisation and exacerbation frequency. Sleep disordered breathing is under-recognised by COPD patients and their clinicians, however early diagnosis and management is crucial to reduce the risk of adverse clinical outcomes. In this narrative review, we describe the pathophysiology of COPD and physiological changes that occur during sleep, manifestations and diagnosis of sleep disordered breathing in COPD and associated clinical outcomes.

Admission oxygen saturation and all-cause in-hospital mortality in acute myocardial infarction patients: data from the MIMIC-III database

Background

Acute myocardial infarction (AMI) is mainly caused by a mismatch of blood oxygen supply and demand in the myocardium. However, several studies have suggested that excessively high or low arterial oxygen tension could have deleterious effects on the prognosis of AMI patients. Therefore, the relationship between blood oxygenation and clinical outcomes among AMI patients is unclear, and could be nonlinear. In the critical care setting, blood oxygen level is commonly measured continuously using pulse oximetry-derived oxygen saturation (SpO₂). The present study aimed to determine the association between admission SpO₂ levels and all-cause in-hospital mortality, and to elucidate the optimal SpO₂ range with real-world data.

Methods

Patients diagnosed with AMI on admission in the Medical Information Mart for Intensive Care III (MIMIC-III) database were included. A generalized additive model (GAM) with loess smoothing functions was used to determine and visualize the nonlinear relationship between admission SpO₂ levels within the first 24 hours after ICU admission and mortality. Moreover, the Cox regression model was constructed to confirm the association between SpO₂ and mortality.

Results

We included 1,846 patients who fulfilled our inclusion criteria, among whom 587 (31.80%) died during hospitalization. The GAM showed that the relationship between admission SpO₂ levels and all-cause in-hospital mortality among AMI patients was nonlinear, as a U-shaped curve was observed. In addition, the lowest mortality was observed for an SpO₂ range of 94–96%. Adjusted multivariable Cox regression analysis confirmed that the admission SpO₂ level of 94–96% was independently associated with decreased mortality compared to SpO₂ levels <94% [hazard ratio (HR) 1.352; 95% confidence interval (CI): 1.048–1.715; P=0.028] and >96% (HR 1.315; 95% CI: 1.018–1.658; P=0.030).

Conclusions

The relationship between admission SpO₂ levels and all-cause in-hospital mortality followed a U-shaped curve among patients with AMI. The optimal oxygen saturation range was identified as an SpO₂ range of 94–96%, which was independently associated with increased survival in a large and heterogeneous cohort of AMI patients.

Considerations for target oxygen saturation in COVID-19 patients: are we under-shooting?

BACKGROUND

The current target oxygen saturation range for patients with COVID-19 recommended by the National Institutes of Health is 92-96%.

MAIN BODY

This article critically examines the evidence guiding current target oxygen saturation recommendation for COVID-19 patients, and raises important concerns in the extrapolation of data from the two studies stated to be guiding the recommendation. Next, it examines the influence of hypoxia on upregulation of ACE2 (target receptor for SARS-CoV-2 entry) expression, with supporting transcriptomic analysis of a publicly available gene expression profile dataset of human renal proximal tubular epithelial cells cultured in normoxic or hypoxic conditions. Finally, it discusses potential implications of specific clinical observations and considerations in COVID-19 patients on target oxygen saturation, such as diffuse systemic endothelitis and microthrombi playing an important pathogenic role in the wide range of systemic manifestations, exacerbation of hypoxic pulmonary vasoconstriction in the setting of pulmonary vascular endothelitis/microthrombi, the phenomenon of "silent hypoxemia" with some patients presenting to the hospital with severe hypoxemia disproportional to symptoms, and overburdened health systems and public health resources in many parts of the world with adverse implications on outpatient monitoring and early institution of oxygen supplementation.

CONCLUSIONS

The above factors and analyses, put together, call for an urgent exploration and re-evaluation of target oxygen saturation in COVID-19 patients, both in the inpatient and outpatient settings. Until data from such trials become available, where possible, it may be prudent to target an oxygen saturation at least at the upper end of the recommended 92-96% range in COVID-19 patients both in the inpatient and outpatient settings (in patients that are normoxemic at pre-COVID baseline). Home pulse oximetry, tele-monitoring, and earlier institution of oxygen supplementation for hypoxemic COVID-19 outpatients could be beneficial, where public health resources allow for their implementation.

The uses of overnight pulse oximetry

Overnight pulse oximetry (OPO) has proven to be an effective and beneficial technique to determine the cardiorespiratory status of patients in both the inpatient and outpatient settings. It is a cheap, safe, reliable, simple, and accurate method of patient monitoring as compared to the expensive and labor-intensive method of multichannel polysomnography for detecting sleep-disordered breathing. It provides accurate information about patient's oxygenation status and also helps in monitoring the response to continuous positive airway pressure and in the surgical treatment of obstructive sleep apnea (OSA). Nocturnal hypoxemia portends a poor prognosis in patients of chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), and neuromuscular diseases. OPO can help its early detection and management.

Sleep-disordered breathing and comorbidities: role of the upper airway and craniofacial skeleton

Obstructive sleep-disordered breathing (SDB), which includes primary snoring through to obstructive sleep apnea syndrome (OSAS), may cause compromise of respiratory gas exchange during sleep, related to transient upper airway narrowing disrupting ventilation, and causing oxyhemoglobin desaturation and poor sleep quality. SDB is common in chronic disorders and has significant implications for health. With prevalence rates globally increasing, this condition is causing a substantial burden on health care costs. Certain populations, including people with sickle cell disease (SCD), exhibit a greater prevalence of OSAS. A review of the literature provides the available normal polysomnography and oximetry data for reference and documents the structural upper airway differences between those with and without OSAS, as well as between ethnicities and disease states. There may be differences in craniofacial development due to atypical growth trajectories or extramedullary hematopoiesis in anemias such as SCD. Studies involving MRI of the upper airway illustrated that OSAS populations tend to have a greater amount of lymphoid tissue, smaller airways, and smaller lower facial skeletons from measurements of the mandible and linear mental spine to clivus. Understanding the potential relationship between these anatomical landmarks and OSAS could help to stratify treatments, guiding choice towards those which most effectively resolve the obstruction. OSAS is relatively common in SCD populations, with hypoxia as a key manifestation, and sequelae including increased risk of stroke. Combatting any structural defects with appropriate interventions could reduce hypoxic exposure and consequently reduce the risk of comorbidities in those with SDB, warranting early treatment interventions.

Individuals With Scleroderma May Have Increased Risk of Sleep-Disordered Breathing

STUDY OBJECTIVES

Scleroderma is associated with abnormal skin thickening, interstitial lung disease, pulmonary hypertension, and abnormalities of the upper airway. These changes can cause cardiopulmonary complications, potentially including sleep-disordered breathing. The objective of this study is to examine the risk of sleep-disordered breathing in patients with scleroderma.

METHODS

We retrospectively identified patients with documented scleroderma. We abstracted data from their electronic health records, including findings from antibody tests, serial pulmonary function tests, transthoracic echocardiography, high-resolution computed tomography, and overnight forehead oximetry.

RESULTS

We identified 171 patients with scleroderma. Mean age at the time of initial consult was 56.5 years (range, 18-96 years), and 150 (86.7%) were women. Scleroderma was categorized as limited disease for 108 (62.4%), diffuse disease for 59 (34.1%), and mixed connective tissue disease for 6 (3.5%). Fifty-four patients (31.2%) had abnormal overnight forehead oximetry results, defined as an oxygen desaturation index greater than 5 or a baseline mean arterial oxygen saturation level less than 90%.

CONCLUSIONS

Cardiopulmonary complications are common in patients with scleroderma, one of which may be sleep-disordered breathing. In our cohort, approximately one-third of individuals with scleroderma had evidence of sleep-disordered breathing. Moreover, the rate of sleep-disordered breathing in our population of scleroderma patients was twice the rate of pulmonary hypertension and was approximately the same as the rate of interstitial lung disease. Future prospective studies are needed to further assess the role of sleep-disordered breathing in scleroderma clinical outcomes.

Sleep and interstitial lung disease

PURPOSE OF REVIEW

There is an increasing recognition of the impact of sleep and sleep disorders on respiratory disease. Recent years have seen a new focus on the relationship between sleep and outcomes in patients interstitial lung disease (ILD).

RECENT FINDINGS

Recent studies suggest a high prevalence of sleep issues in ILD cohorts, which seem to have a meaningful negative impact on quality of life, disease progression, and survival.

SUMMARY

Sleep disordered breathing is common in ILD patients: obstructive sleep apnoea (OSA) is found in 44-72% of ILD patients, and nocturnal hypoxemia is relatively common even in the absence of OSA. Sleep disorders are associated with worse quality of life in ILD, and may also predict more rapid disease progression and increased mortality. It remains unknown if nocturnal hypoxemia may itself cause progression of ILD. Uncontrolled and retrospective studies have suggested that treating OSA may improve ILD-related outcomes, but prospective studies are lacking in this field.

Prevention of Morbidity in Sickle Cell Disease (POMS2a)-overnight auto-adjusting continuous positive airway pressure compared with nocturnal oxygen therapy: a randomised crossover pilot study examining patient preference and safety in adults and children

DESIGN

This randomised crossover trial compared nocturnal auto-adjusting continuous positive airway pressure (APAP) and nocturnal oxygen therapy (NOT) in adults and children with sickle cell anaemia, with patient acceptability as the primary outcome. Secondary outcomes included pulmonary physiology (adults), safety, and daily pain during interventions and washout documented using tablet technology.

METHODS

Inclusion criteria were age > 8 years and the ability to use an iPad to collect daily pain data. Trial participation was 4 weeks; week 1 involved baseline data collection and week 3 was a washout between interventions, which were administered for 7 days each during weeks 2 and 4 in a randomised order. Qualitative interviews were transcribed verbatim and analysed for content using a funnelling technique, starting generally and then gaining more detailed information on the experience of both interventions. Safety data included routine haematology and median pain days between each period. Missing pain day values were replaced using multiple imputation.

RESULTS

Ten adults (three female, median age 30.2 years, range 18-51.5 years) and eleven children (five female, median age 12 years, range 8.7-16.9 years) enrolled. Nine adults and seven children completed interviews. Qualitative data revealed that the APAP machine was smaller, easier to handle, and less noisy. Of 16 participants, 10 preferred APAP (62.5%, 95% confidence interval (CI) 38.6-81.5%). Haemoglobin decreased from baseline on APAP and NOT (mean difference -3.2 g/L (95% CI -6.0 to -0.2 g/L) and -2.5 g/L (95% CI -4.6 to 0.3 g/L), respectively), but there was no significant difference between interventions (NOT versus APAP, 1.1 (-1.2 to 3.6)). Pulmonary function changed little. Compared with baseline, there were significant decreases in the median number of pain days (1.58 for APAP and 1.71 for NOT) but no significant difference comparing washout with baseline. After adjustment for carry-over and period effects, there was a non-significant median difference of 0.143 (95% CI -0.116 to 0.401) days additional pain with APAP compared with NOT.

CONCLUSION

In view of the point estimate of patient preference for APAP, and no difference in haematology or pulmonary function or evidence that pain was worse during or in washout after APAP, it was decided to proceed with a Phase II trial of 6 months APAP versus standard care with further safety monitoring for bone marrow suppression and pain.

TRIAL REGISTRATION

ISRCTN46078697 . Registered on 18 July 2014.

Mobile Health for Central Sleep Apnea Screening Among Patients With Stable Heart Failure: Single-Cohort, Open, Prospective Trial

Background

Polysomnography is the gold standard for detection of central sleep apnea in patients with stable heart failure. However, this procedure is costly, time consuming, and a burden to the patient and therefore unsuitable as a screening method. An electronic health (eHealth) app to measure overnight oximetry may be an acceptable screening alternative, as it can be automatically analyzed and is less burdensome to patients.

Objective

This study aimed to assess whether overnight pulse oximetry using a smartphone-compatible oximeter can be used to detect central sleep apnea in a population with stable heart failure.

Methods

A total of 26 patients with stable heart failure underwent one night of both a polygraph examination and overnight saturation using a smartphone-compatible oximeter. The primary endpoint was agreement between the oxygen desaturation index (ODI) above or below 15 on the smartphone-compatible oximeter and the diagnosis of the polygraph.

Results

The median age of patients was 66.4 (interquartile range, 62-71) years and 92% were men. The median body mass index was 27.1 (interquartile range, 24.4-30.8) kg/m². Two patients were excluded due to incomplete data, and two other patients were excluded because they could not use a smartphone. Seven patients had central sleep apnea, and 6 patients had obstructive sleep apnea. Of the 7 (of 22, 32%) patients with central sleep apnea that were included in the analysis, 3 (13%) had an ODI≥15. Of all patients without central sleep apnea, 8 (36%) had an ODI<15. The McNemar test yielded a P value of .55.

Conclusions

Oxygen desaturation measured by this smartphone-compatible oximeter is a weak predictor of central sleep apnea in patients with stable heart failure.

Evaluating the clinical value of the hypoxia burden index in patients with obstructive sleep apnea

PURPOSE

We aimed to develop a novel index, the hypoxia burden index (HBI), that reflects the degree and duration of oxygen desaturation, and to determine whether this index is better than the apnea hypopnea-index (AHI) for evaluating obstructive sleep apnea (OSA) and cardiovascular diseases morbidities.

METHODS

We retrospectively analyzed 459 adult subjects who underwent overnight polysomnography (PSG) in this study. The HBI was calculated by dividing the total desaturation area of SpO₂ below 90% by the TST measured in seconds. Correlations between the HBI and PSG parameters and the cardiovascular diseases (CVDs) of inpatients were explored.

RESULTS

For the 459 participants, the HBI was highly correlated with the AHI (r = 0.690), lowest oxygen saturation (SpO₂min) (r = -0.733), and proportion of cumulative sleep time with SpO₂ below 90% in total sleep time (TST) (CT90%) (r = 0.801). The HBI was mildly correlated with Epworth sleepiness scale score, morning systolic blood pressure, diastolic blood pressure, and mean arterial pressure. Among the significantly different parameters in the CVD and non-CVD groups in 202 inpatients (age, sex, the longest time of apnea, AHI, and HBI), only age, sex, and HBI [OR 1.006 (1.001-1.011), p = 0.021] were independently correlated with CVDs.

CONCLUSIONS

The HBI considers both hypoxia duration and severity during sleep. It may have potential value in predicting the clinical outcomes of OSA based on its correlation with ESS scores and morning blood pressure as well as its independent association with the prevalence of CVDs, whereas the AHI is not significantly associated with CVD prevalence.

Diurnal changes of arterial oxygen saturation and erythropoietin concentration in male and female highlanders

In Caucasians and Native Americans living at altitude, hemoglobin mass is increased in spite of erythropoietin concentrations ([Epo]) not markedly differing from sea level values. We hypothesized that a nocturnal decrease of arterial oxygen saturation (SaO₂) causes a temporary rise of [Epo] not detected by morning measurements. SaO₂ (continuous, finger oximeter) and [Epo] (ELISA, every 4 h) were determined in young highlanders (altitude 2600 m) during 24 h of usual daily activity. In Series I (six male, nine female students), SaO₂ fell during the night with the nadir occurring between 01:00 and 03:00; daily means (range 92.4–95.2%) were higher in females (+1.7%, P < 0.01). [Epo] showed opposite changes with zenith occurring at 04:00 without a sex difference. Mean daily values (22.9 ± 10.7SD U/L) were higher than values obtained at 08:00 (17.2 ± 9.5 U/L, P < 0.05). In Series II (seven females), only SaO₂ was measured. During follicular and luteal phases, SaO₂ variation was similar to Series I, but the rhythm was disturbed during menstruation. While daily [Epo] variations at sea level are not homogeneous, there is a diurnal variation at altitude following changes in SaO₂. Larger hypoventilation‐dependent decreases of alveolar PO₂ decreases during the night probably cause a stronger reduction of SaO₂ in highlanders compared to lowlanders. This variation might be enlarged by a diurnal fluctuation of Hb concentration. In spite of a lower [Hb], the higher SaO₂ in women compared to men led to a similar arterial oxygen content, likely explaining the absence of differences in [Epo] between sexes.

Sleep as a New Target for Improving Outcomes in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common type of interstitial pneumonia but remains a disease with a poor outcome. Two drugs, pirfenidone and nintedanib, have shown promising results at stalling disease progression; however, the interplay of sleep disruption or sleep disorders overall and in relation to medication effectiveness remains understudied. In the past, there was limited interest in the role of sleep in patients with IPF. Treating physicians tended to address only the daily disabling symptoms while disregarding the possible significant role of sleep alterations or coexisting sleep disorders. During the past few years, there has been more research related to sleep disturbances in patients with IPF and their possible role in sleep and overall life quality, disease progression, and outcome. In summary, sleep in patients with IPF is significantly impaired, with alterations in sleep architecture, changes in sleep breathing pattern, and decreases in oxygen saturation mainly during vulnerable rapid eye movement sleep. There also is evidence that OSA has an increased prevalence in these patients, playing an important role in the already worse sleep quality related to the disease itself. The focus of this review is not only to present current data related to sleep in patients with IPF but also to point out that therapy for sleep problems and OSA is likely to improve sleep and life quality as well as disease outcome. The main priority remains to increase awareness among treating physicians about early diagnosis of OSA in patients with IPF and to emphasize the need for intense future research, especially on the role of intermittent hypoxia superimposed on chronic hypoxia during sleep in patients with IPF.

Lower hypoxic ventilatory response in smokers compared to non-smokers during abstinence from cigarettes

BACKGROUND

Carotid body O₂-chemosensitivity determines the hypoxic ventilatory response (HVR) as part of crucial regulatory reflex within oxygen homeostasis. Nicotine has been suggested to attenuate HVR in neonates of smoking mothers. However, whether smoking affects HVR in adulthood has remained unclear and probably blurred by acute ventilatory stimulation through cigarette smoke. We hypothesized that HVR is substantially reduced in smokers when studied after an overnight abstinence from cigarettes i.e. after nicotine elimination.

METHODS

We therefore determined the isocapnic HVR of 23 healthy male smokers (age 33.9 ± 2.0 years, BMI 24.2 ± 0.5 kg m^-2, mean ± SEM) with a smoking history of >8 years after 12 h of abstinence and compared it to that of 23 healthy male non-smokers matched for age and BMI.

RESULTS

Smokers and non-smokers were comparable with regard to factors known to affect isocapnic HVR such as plasma levels of glucose and thiols as well as intracellular levels of glutathione in blood mononuclear cells. As a new finding, abstinent smokers had a significantly lower isocapnic HVR (0.024 ± 0.002 vs. 0.037 ± 0.003 l min^-1 %^-1BMI^-1, P = 0.002) compared to non-smokers. However, upon re-exposure to cigarettes the smokers' HVR increased immediately to the non-smokers' level.

CONCLUSIONS

This is the first report of a substantial HVR reduction in abstinent adult smokers which appears to be masked by daily smoking routine and may therefore have been previously overlooked. A low HVR may be suggested as a novel link between smoking and aggravated hypoxemia during sleep especially in relevant clinical conditions such as COPD.

Respiratory Periodicity and Electroencephalogram Arousals During Sleep in Older Adults

The aim of this exploratory study was to examine the relationship of electroencephalogram (EEG) arousals to breathing patterns and the relationship of both arousals and breathing patterns to arterial oxygenation during sleep in older adults. Five older adults were monitored using standard polysomnography. Records were divided into 5-min segments and breathing patterns identified based on the level of respiratory periodicity and the variability in the frequency of breathing cycles. Standard criteria were used to determine sleep states and occurrence of EEG arousals. High respiratory periodicity was seen in 23% of the segments, whereas 24% had low respiratory periodicity with minimal variability in the frequency of breathing (Type A low respiratory periodicity) and 53% had low respiratory periodicity with high variability in the frequency of breathing (Type B low respiratory periodicity). Nearly all (97%) segments with high respiratory periodicity had EEG arousals, whereas fewer segments (33%) with low respiratory periodicity had arousals, regardless of the stage of sleep. Desaturations occurred more often in segments with high respiratory periodicity, F (2,4) = 57.3, p < .001, but overall, the mean SaO2 of segments with high respiratory periodicity did not differ from levels seen in segments with low respiratory periodicity, F( 2,4) = 0.77, ns. Our findings suggest that high respiratory periodicity is a common feature of EEG arousals and, in older adults, may be important for maintaining oxygen levels during desaturations during sleep.

Thoracic Society of Australia and New Zealand oxygen guidelines for acute oxygen use in adults: 'Swimming between the flags'

The purpose of the Thoracic Society of Australia and New Zealand guidelines is to provide simple, practical evidence-based recommendations for the acute use of oxygen in adults in clinical practice. The intended users are all health professionals responsible for the administration and/or monitoring of oxygen therapy in the management of acute medical patients in the community and hospital settings (excluding perioperative and intensive care patients), those responsible for the training of such health professionals, and both public and private health care organizations that deliver oxygen therapy.

Could transient hypoxia be associated with rhythmic masticatory muscle activity in sleep bruxism in the absence of sleep-disordered breathing? A preliminary report

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth during sleep. Sleep bruxism activity is characterised by rhythmic masticatory muscle activity (RMMA). Many but not all RMMA episodes are associated with sleep arousal. The aim of this study was to evaluate whether transient oxygen saturation level change can be temporally associated with genesis of RMMA/SB. Sleep laboratory or home recordings data from 22 SB (tooth grinding history in the absence of reported sleep-disordered breathing) and healthy subjects were analysed. A total of 143 RMMA/SB episodes were classified in four categories: (i) no arousal + no body movement; (ii) arousal + no body movement; (iii) no arousal + body movement; (iv) arousal + body movement. Blood oxygen levels (SaO2 ) were assessed from finger oximetry signal at the baseline (before RMMA), and during RMMA. Significant variation in SaO2 over time (P = 0·001) was found after RMMA onset (+7 to +9 s). No difference between categories (P = 0·91) and no interaction between categories and SaO2 variation over time (P = 0·10) were observed. SaO2 of six of 22 subjects (27%) remained equal or slight increase after the RMMA/SB onset (+8 s) compared to baseline; 10 subjects (45%) slightly decreased (drop 0·01-1%) and the remaining (27%) decreased between 1% and 2%. These preliminary findings suggest that a subgroup of SB subjects had (i) a minor transient hypoxia potentially associated with the onset of RMMA episodes, and this (ii) independently of concomitant sleep arousal or body movements.

Sleep apnea and oxygen saturation in adults at 2640 m above sea level

PURPOSE

To describe the SpO2 in wakefulness, sleep and during the apnea-hypopnea in adults living in Bogotá, located at 2640 m above sea level.

METHODS

Descriptive observational study in adults referred for polysomnogram (PSG). A normal Apnea hypopnea index (AHI) was defined as ≤5 and obstructive sleep apnea (OSA) was classified as mild (AHI 5-15), moderate (AHI 15-30), and severe (AHI >30). T-test or ANOVA test for SpO2 differences between groups was used.

RESULTS

1799 patients, 33% women. 222 (12.8%) did not have OSA (normal IAH), 268 (14.9%) mild OSA, 315 (17.5%) moderate ,and 993 (55.2%) severe. In all cases a low SpO2 (SpO2<90%) was found. The SpO2 was lower when the AHI was higher, in wakefulness, in non-REM and in REM (p<0.001). For all grades of severity, SpO2 decreased significantly from wakefulness to non-REM sleep and to REM sleep (p<0.001). Patients with severe OSA had higher desaturation during wakefulness (85.2±6.6%), non-REM sleep (83.1±7.7%), REM sleep (78.8±10.2), and during events (75.1±9.1%).

CONCLUSIONS

Patients with OSA at 2640 m have nocturnal desaturation lower than 88%, which decreases with higher severity of OSA. The clinical impact of sleep disorders at this point may be greater than at sea level and should be studied.

Sensitivity of Intravenous and Oral Alfentanil and Pupillary Miosis as Minimally Invasive and Noninvasive Probes for Hepatic and First-Pass CYP3A Activity

This investigation determined the ability of alfentanil miosis and single-point concentrations to detect various degrees of CYP3A inhibition. Results were compared with those for midazolam, an alternative CYP3A probe. Twelve volunteers were studied in a randomized 4-way crossover, targeting 12%, 25%, and 50% inhibition of hepatic CYP3A. They received 0, 100, 200, or 400 mg oral fluconazole, followed 1 hour later by 1 mg intravenous midazolam and then 15 microg/kg intravenous alfentanil 1 hour later. The next day, they received fluconazole, followed by 3 mg oral midazolam and 40 microg/kg oral alfentanil. Dark-adapted pupil diameters were measured coincident with blood sampling. Area under the plasma concentration-time curve (AUC) ratios (fluconazole/control) after 100, 200, and 400 mg fluconazole were (geometric mean) 1.3*, 1.4*, and 2.0* for intravenous midazolam and 1.2*, 1.6*, and 2.2* for intravenous alfentanil (*significantly different from control), indicating 16% to 21%, 31% to 36%, and 43% to 53% inhibition of hepatic CYP3A. Single-point concentration ratios were 1.5*, 1.8*, and 2.4* for intravenous midazolam (at 5 hours) and 1.2*, 1.6*, and 2.2* for intravenous alfentanil (at 4 hours). Pupil miosis AUC ratios were 0.9, 1.0, and 1.2*. After oral dosing, plasma AUC ratios were 2.3*, 3.6*, and 5.3* for midazolam and 1.8*, 2.9*, and 4.9* for alfentanil; plasma single-point ratios were 2.4*, 4.5*, and 6.9* for midazolam and 1.8*, 2.9*, and 4.9* for alfentanil, and alfentanil miosis ratios were 1.1, 1.9*, and 2.7*. Plasma concentration AUC ratios of alfentanil and midazolam were equivalent for detecting hepatic and first-pass CYP3A inhibition. Single-point concentrations were an acceptable surrogate for formal AUC determinations and as sensitive as AUCs for detecting CYP3A inhibition. Alfentanil miosis could detect 50% to 70% inhibition of CYP3A activity, but was less sensitive than plasma AUCs. Further refinements are needed to increase the sensitivity of alfentanil miosis for detecting small CYP3A changes.

Comorbidities and survival in obstructive sleep apnoea beyond the age of 50

BACKGROUND

Although mortality risk associated with obstructive sleep apnoea (OSA) tends to disappear from the age of 50, it has been suggested that OSA treatment by continuous positive airway pressure (CPAP) improves survival even in older subjects. Life expectancy of subjects with several diseases is worse if OSA coexists. The objectives of this study were to evaluate the relevance of comorbidities in the relationship between OSA and mortality, and in the effect of CPAP on survival, in subjects ≥ 50 years old.

METHODS

Data from 810 patients studied by polysomnography for suspected OSA between 1991 and 2000 were retrospectively evaluated. In 2009, state of survival and use of CPAP were enquired. Three hundred and thirteen subjects were < 50 and 497 were ≥ 50 years at diagnosis.

RESULTS

Age and comorbidities, but not apnoea/hypopnoea index (AHI) or lowest nocturnal arterial oxygen saturation (Nadir SaO(2)), predicted mortality in the whole sample. Nadir SaO(2) was related to mortality among the younger subjects without comorbidities (P = 0·01), but not among the older subjects. In the older patients with an AHI > 30 CPAP treatment was associated with a better survival only if comorbidities coexisted.

CONCLUSIONS

Unlike in younger subjects, in subjects ≥ 50 years old, comorbidities do not mask an effect of OSA on mortality. Among OSA subjects ≥ 50 years old, comorbidities could separate those who may expect an improvement in survival with CPAP treatment from those who may not. Possibly, after the age of 50, OSA per se does not affect survival, but worsens prognosis of subjects with coexisting diseases.

Nocturnal oxygen saturation in children with stable cystic fibrosis

BACKGROUND

Hypoxemia during sleep is a common finding in Cystic Fibrosis (CF) patients with more advanced lung disease. Nocturnal hypoxemia is associated with frequent awakenings and poor sleep quality. For children with CF, data of nocturnal oxygen saturation are sparse.

OBJECTIVE

To assess the oxygen saturation profile during sleep in 25 clinically stable children with CF lung disease and to correlate these data with spirometry, cough frequency, sleep quality, and CT-scan scores.

METHOD

During two nights cough was recorded with a digital audio recorder in 25 clinically stable CF patients. In addition oxygen saturation was measured. The day following the recording spirometry was carried out. CT scores were obtained from the most recent routine CT scan.

RESULTS

Twenty-two patients were included in the study. Mean age (range) was 13 (6-18) years. Spirometry was FVC% 84 (range 52-114), FEV(1) % 77 (range 43-115), and FEF(75) % 50 (range 12-112). The mean SO(2) was 95.6% for the first and 96.2% for the second night. Mean SO(2) between the two nights correlated strongly (r(s) = 0.84, P < 0.001). Positive correlation was observed between mean SO(2) of the two nights (mean × SO(2)) and FVC, FEV(1) and FEF(75). Correlations were found between mean × SO(2) and the total CT score (r(s) = -0.45, P = 0.05) and the bronchiectasis subscore (r(s) = -0.48, P = 0.03).

CONCLUSION

Nocturnal oxygen saturation in children with stable CF is lower than that in healthy children, and is correlated with lung function parameters and CT scores. Monitoring oxygen saturation during one night is sufficient to get a representative recording.

Supplemental oxygen therapy: Important considerations in oral and maxillofacial surgery

The administration of supplemental oxygen is an essential element of appropriate management for a wide range of clinical conditions; crossing different medical and surgical specialities. The present review summarizes the role of supportive oxygen therapy in various clinical conditions encountered in our day-to-day practice in the speciality of oral and maxillofacial surgery; including major trauma, shock, sepsis; perioperative and postoperative considerations and in patients with various other medical comorbidities. Regular and judicious use of oxygen as a drug is thus recommended in our day-to-day practice in oral and maxillofacial surgery to reduce the morbidity and improve the prognosis of patients.

Apnea produces excitotoxic hippocampal synapses and neuronal apoptosis

Obstructive sleep apnea (OSA) results in the degeneration of neurons in the hippocampus that eventuates in neurocognitive deficits. We were therefore interested in determining the effects of apnea on monosynaptic excitatory processes in a hippocampal pathway (cornu ammonis 3-cornu ammonis 1, CA3-CA1) that has been shown to mediate the processing of cognitive information. In addition, to substantiate an anatomical basis for the cognitive dysfunction that occurs in OSA patients, we examined the effects of apnea with respect to neurodegenerative changes (apoptosis) in the same hippocampal pathway. In order to determine the effects of apnea, an automated system for the generation and analysis of single and recurrent periods of apnea was developed. Utilizing this system, the field excitatory postsynaptic potential (fEPSP) generated by pyramidal neurons in the CA1 region of the hippocampus was monitored in α-chloralose anesthetized rats following stimulation of glutamatergic afferents in the CA3 region. A stimulus-response (input-output) curve for CA3-CA1 synaptic activity was determined. In addition, a paired-pulse paradigm was employed to evaluate, electrophysiologically, the presynaptic release of glutamate. Changes in the synaptic efficacy were assessed following single episodes of apnea induced by ventilatory arrest (60 to 80 s duration, mean=72 s; mean oxygen desaturation was 53% of normoxia level). Apnea resulted in a significant potentiation of the amplitude (mean=126%) and slope (mean=117%) of the baseline CA1 fEPSP. This increase in the fEPSP was accompanied by a significant decrease in the amplitude (71%) and slope (81%) of normalized paired-pulse facilitation (PPF) ratios. Since the potentiation of the fEPSP is inversely proportional to changes in PPF ratio, the potentiated fEPSP accompanied by the reduced PPF reveals that apnea produces an abnormal increase in the preterminal release of glutamate that results in the over-activation (and calcium overloading) of hippocampal CA1 neurons. Thus, we conclude that individual episodes of apnea result in the development of excitotoxic processes in the hippocampal CA3-CA1 pathway that is critically involved in the processing of cognitive information. Morphologically, the deleterious effect of recurrent apnea was substantiated by the finding of apoptosis in CA1 neurons of apneic (but not normoxic) animals.

Sleep desaturation and its relationship to lung function, exercise and quality of life in LAM

BACKGROUND

Lymphangioleiomyomatosis (LAM) is characterised by progressive airway obstruction and hypoxaemia in young women. Although sleep may trigger hypoxaemia in patients with airway obstruction, it has not been previously investigated in patients with LAM.

METHODS

Consecutive women with lung biopsy proven LAM and absence of hypoxaemia while awake were evaluated with pulmonary function test, echocardiography, 6-min walk test, overnight full polysomnography, and Short Form 36 health-related quality-of-life questionnaire.

RESULTS

Twenty-five patients with (mean±SD) age 45±10 years, SpO(2) awake 95%±2, forced expiratory volume in the first second (median-interquartile) FEV(1)(% predicted) 77 (47-90) and carbonic monoxide diffusion capacity, DL(CO) (%) 55 (34-74) were evaluated. Six-minute walk test distance and minimum SpO(2) (median-interquartile) were, respectively, 447m (411-503) and 90% (82-94). Median-interquartile apnoea-hypopnoea index was in the normal range 2 (1-5). Fourteen patients (56%) had nocturnal hypoxaemia (10% total sleep time with SpO(2) <90%), and the median sleep time spent with SpO(2) <90% was 136 (13-201)min. Sleep time spent with SpO(2) <90% correlated with the residual volume/total lung capacity ratio (r(s)=0.5, p: 0.02), DL(CO) (r(s)=-0.7, p: 0.001), FEV(1) (r(s)=-0.6, p: 0.002). Multivariate linear regression model showed that RV/TLC ratio was the most important functional variable related to sleep hypoxaemia.

CONCLUSION

Significant hypoxaemia during sleep is common in LAM patients with normal SpO(2) while awake, especially among those with some degree of hyperinflation in lung function tests.

Nocturnal home pulse oximetry: variability and clinical implications in home mechanical ventilation

BACKGROUND

Nocturnal home pulse oximetry (NHPO) provides information by measuring a series of variables: time spent with SaO(2) <90% expressed as percentage (T90) or in minutes (Tm90), mean SaO(2) (MnS), and lowest SaO(2) (LwS.) The presence of significant nocturnal desaturation has been proposed as a parameter in decision making with regard to initiating home mechanical ventilation (HMV) or monitoring HMV effectiveness. However, there is limited information on the possible variability of the test, and this could influence the interpretation of results.

OBJECTIVES

To explore the variability between 2 consecutive measurements of NHPO and to determine clinical applications in HMV.

METHODS

The patients presented diseases susceptible to HMV treatment and were enrolled in stable condition without respiratory failure. NHPO was conducted on 2 consecutive nights. The variables analyzed were: T90, Tm90, Mns, and LwS. The coefficient of variation (CV), a concordance coefficient (CC), and the Bland-Altman method were used in order to explore the variability.

RESULTS

We studied 40 cases. Two were excluded, and the remaining 38 were aged 58 ± 16 years (19 males). Eighteen were receiving HMV. CV values exceeded 100% for T90 and Tm90 and were below 5% for MnS and LwS. The CC for T90, Tm90, and LwS showed confidence intervals with lower limits below 0.5, while for MnS the value was 0.88 (0.79-0.93).

CONCLUSIONS

There is a wide variability in NHPO recordings for T90, Tm90, and LwS, so a single determination to detect nocturnal desaturation may not be valid for decision making; the parameter with the least interindividual variability and intraindividual variability was MnS.

Cerebral oxygenation in wake and during sleep and its relationship to cognitive function in community-dwelling older adults without sleep disordered breathing

BACKGROUND

This descriptive cross-sectional study investigated the relationships between cerebral oxygen reserve and cognitive function in community-dwelling older adults.

METHODS

Participants (72 women and 40 men) underwent standard polysomnography, including regional measures of percent oxyhemoglobin saturation (rcSO(2)) determined by cerebral oximetry. Two variables were used to calculate cerebral oxygen reserve: (a) awake rcSO(2) (mean presleep rcSO(2)) and (b) the change in rcSO(2) from before sleep to the end of the first non-rapid-eye movement cycle. General linear models, adjusted for the effects of education and occupation, tested differences in performance on standard tests of memory, attention, and speed of mental processing.

RESULTS

Awake rcSO(2) values were normal (60%-79.9%) in 64 participants, marginal (50%-59.9%) in 41, and low (43%-49.9%) in 7. Participants with normal awake levels had higher cognitive function than those with low levels (p < .05). Changes in rcSO(2) were greatest in participants with marginal awake rcSO(2) values; among whom, those who increased rcSO(2) during sleep (n = 17) had better memory function than the 24 who did not (p < .05).

CONCLUSIONS

Low awake rcSO(2) values mark individuals with low cerebral oxygen reserves and generally lower cognitive function; marginal awake rcSO(2) values that fall during sleep may indicate loss of cerebral oxygen reserve and an increased risk for cognitive decline. Further studies may clarify the significance of and mechanisms underlying individual differences in awake rcSO(2) and the changes that occur in rcSO(2) while asleep.

Cerebrovascular disease and patterns of cerebral oxygenation during sleep in elders

PURPOSE

The aim of this descriptive exploratory study was to describe patterns of cerebral oxygen reserves during sleep and their association with cerebrovascular risk factors in elders.

METHOD

Participants--115 elders, age 70+ years--were monitored overnight using standard polysomnography. Measures included arterial oxyhemoglobin (SaO2) and regional measures of percentage of cerebral oxyhemoglobin saturation (rcSO2) via cerebral oximetry. Participants were classified based on the magnitude of change in rcSO2 from resting baseline to the end of the first nonrapid-eye-movement (NREM) period. One-way ANOVA and Chi-square were used to test group differences in SaO2 and the prevalence of cerebrovascular risk factors.

FINDINGS

20 participants (Group 1) experienced an increase in rcSO2 during sleep along with sleeping rcSO2 levels >or= 55%; 95 participants experienced a decline in rcSO2; 72 participants (Group 2) had sleeping rcSO2 levels >or= 55%; and 23 participants had sleeping rcSO2 levels <55% (Group 3). Although all three groups had equivalent declines in SaO2 levels during sleep, Group 3 had more cardiovascular comorbidity than Groups 1 and 2.

CONCLUSIONS

Although SaO2 levels decline in most people during sleep, compensatory vascular responses to these drops in SaO2 are important for preventing rcSO2 from falling during sleep. Those entering sleep with lower baseline rcSO2 levels and those with greater declines in cerebral oxygenation during sleep may have greater cardiovascular burden and be at greater risk for stroke and other forms of disabling cerebrovascular disease.