Prospective study to evaluate quality of life in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative rare disease characterized by symptoms and signs in the upper and lower motor neurons, leading to progressive neuro-degeneration and muscle atrophy. Our objective was to analyse the quality of life (QoL) in patients with ALS and compare with general population and with patients with cancer. Prospective study from consecutive ALS patients in one center. In order to assess quality of life, during the first visit three questionnaires were administered: Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R), Short Form-36 (SF-36) and EuroQoL 5D (EQ-5D). We compared SF-36 of ALS patients with a reference population (n = 9151), and we compared the EQ-5D index score of ALS patients versus patients with cancer in the same area and in the same period (2015-2018). Between June 2015 and September 2017, 23 were included. The mean age was 65.1 ± 12.6 years and 56.5% were women. Compared with the general population, patients with ALS showed lowest QoL (p < 0.05) in all the dimensions, with a very important impairment in physical function (median: 0; p25-75: 0-10) and physical role (median: 0; p25-75: 0-6.25). In EQ-5D questionnaire, patients with ALS presented an EQ-5D index score of 0.21 ± 0.39 (mean ± standard deviation) with a visual analog scale (VAS) score of 0.32 ± 0.24. Compared with an oncological population, patients with ALS had a worse EQ-5D index score both clinically and statistically (0.21 ± 0.39 vs. 0.77 ± 0.27; p < 0.05). We demonstrate a poorer quality of life in patients with ALS is poor, and clinically and statistically worse than in patients with cancer or general population. New studies need to evaluate the impact of strategies in this population to improve the quality of life.

Rearrangement of cell types in the rat carotid body neurogenic niche induced by chronic intermittent hypoxia

The carotid body (CB) is a prototypical acute oxygen (O₂ )-sensing organ that mediates reflex hyperventilation and increased cardiac output in response to hypoxaemia. CB overactivation, secondary to the repeated stimulation produced by the recurrent episodes of intermittent hypoxia, is believed to contribute to the pathogenesis of sympathetic hyperactivity present in sleep apnoea patients. Although CB functional plasticity induced by chronic intermittent hypoxia (CIH) has been demonstrated, the underlying mechanisms are not fully elucidated. Here, we show that CIH induces a small increase in CB volume and rearrangement of cell types in the CB, characterized by a mobilization of immature quiescent neuroblasts, which enter a process of differentiation into mature, O₂ -sensing and neuron-like, chemoreceptor glomus cells. Prospective isolation of individual cell classes has allowed us to show that maturation of CB neuroblasts is paralleled by an upregulation in the expression of specific glomus cell genes involved in acute O₂ -sensing. CIH enhances mitochondrial responsiveness to hypoxia in maturing neuroblasts as well as in glomus cells. These data provide novel perspectives on the pathogenesis of CB-mediated sympathetic overflow that may lead to the development of new pharmacological strategies of potential applicability in sleep apnoea patients. KEY POINTS: Obstructive sleep apnoea is a frequent condition in the human population that predisposes to severe cardiovascular and metabolic alterations. Activation of the carotid body, the main arterial oxygen-sensing chemoreceptor, by repeated episodes of hypoxaemia induces exacerbation of the carotid body-mediated chemoreflex and contributes to sympathetic overflow characteristic of sleep apnoea patients. In rats, chronic intermittent hypoxaemia induces fast neurogenesis in the carotid body with rapid activation of neuroblasts, which enter a process of proliferation and maturation into O₂ -sensing chemoreceptor glomus cells. Maturing carotid body neuroblasts and glomus cells exposed to chronic intermittent hypoxia upregulate genes involved in acute O₂ sensing and enhance mitochondrial responsiveness to hypoxia. These findings provide novel perspectives on the pathogenesis of carotid body-mediated sympathetic hyperactivation. Pharmacological modulation of carotid body fast neurogenesis could help to ameliorate the deleterious effects of chronic intermittent hypoxaemia in sleep apnoea patients.

Effectiveness of CPAP vs. Noninvasive Ventilation Based on Disease Severity in Obesity Hypoventilation Syndrome and Concomitant Severe Obstructive Sleep Apnea

RATIONALE

Obesity hypoventilation syndrome (OHS) with concomitant severe obstructive sleep apnea (OSA) is treated with CPAP or noninvasive ventilation (NIV) during sleep. NIV is costlier, but may be advantageous because it provides ventilatory support. However, there are no long-term trials comparing these treatment modalities based on OHS severity.

OBJECTIVE

To determine if CPAP have similar effectiveness when compared to NIV according to OHS severity subgroups.

METHODS

Post hoc analysis of the Pickwick randomized clinical trial in which 215 ambulatory patients with untreated OHS and concomitant severe OSA, defined as apnoea-hypopnea index (AHI)≥30events/h, were allocated to NIV or CPAP. In the present analysis, the Pickwick cohort was divided in severity subgroups based on the degree of baseline daytime hypercapnia (PaCO₂ of 45-49.9 or ≥50mmHg). Repeated measures of PaCO₂ and PaO₂ during the subsequent 3 years were compared between CPAP and NIV in the two severity subgroups. Statistical analysis was performed using linear mixed-effects model.

RESULTS

204 patients, 97 in the NIV group and 107 in the CPAP group were analyzed. The longitudinal improvements of PaCO₂ and PaO₂ were similar between CPAP and NIV based on the PaCO₂ severity subgroups.

CONCLUSION

In ambulatory patients with OHS and concomitant severe OSA who were treated with NIV or CPAP, long-term NIV therapy was similar to CPAP in improving awake hypercapnia, regardless of the severity of baseline hypercapnia. Therefore, in this patient population, the decision to prescribe CPAP or NIV cannot be solely based on the presenting level of PaCO₂.

Risk factors associated with pulmonary hypertension in obesity hypoventilation syndrome

STUDY OBJECTIVES

Pulmonary hypertension (PH) is prevalent in obesity hypoventilation syndrome (OHS). However, there is a paucity of data assessing pathogenic factors associated with PH. Our objective is to assess risk factors that may be involved in the pathogenesis of PH in untreated OHS.

METHODS

In a post-hoc analysis of the Pickwick trial, we performed a bivariate analysis of baseline characteristics between patients with and without PH. Variables with a p value ≤0.10 were defined as potential risk factors and were grouped by theoretical pathogenic mechanisms in several adjusted models. Similar analysis was carried out for the two OHS phenotypes, with and without severe concomitant obstructive sleep apnea (OSA).

RESULTS

Of 246 patients with OHS, 122 (50%) had echocardiographic evidence of PH defined as systolic pulmonary artery pressure ≥40 mmHg. Lower levels of awake PaO₂ and higher body mass index (BMI) were independent risk factors in the multivariate model, with a negative and positive adjusted linear association, respectively (adjusted odds ratio 0.96; 95% CI 0.93 to 0.98; p = 0.003 for PaO₂, and 1.07; 95% CI 1.03 to 1.12; p = 0.001 for BMI). In separate analyses, BMI and PaO₂ were independent risk factors in the severe OSA phenotype, whereas BMI and peak in-flow velocity in early (E)/late diastole (A) ratio were independent risk factors in the non-severe OSA phenotype.

CONCLUSIONS

This study identifies obesity per se as a major independent risk factor for PH, regardless of OHS phenotype. Therapeutic interventions targeting weight loss may play a critical role in improving PH in this patient population.

CLINICAL TRIALS REGISTRATION

Registry: Clinicaltrial.gov; Identifier: NCT01405976.

Repeated Pulses of Methyl-Prednisolone in Adults Hospitalized With COVID-19 Pneumonia and Acute Respiratory Distress Syndrome: A Preliminary Before-After Study (CortiCOVID Study)

Introduction

The use of systemic corticosteroids in severely ill patients with coronavirus disease 2019 (COVID-19) is controversial. We aimed to evaluate the efficacy and safety of corticosteroid pulses in patients with COVID-19 pneumonia.

Methods

A quasi-experimental study, before and after, was performed in a tertiary referral hospital, including admitted patients showing COVID-19-associated pneumonia. The standard treatment protocol included targeted COVID-19 antiviral therapy from 23rd March 2020, and additionally pulses of methylprednisolone from 30th March 2020. The primary outcome was a composite endpoint combining oro-tracheal intubation (OTI) and death within 7 days.

Results

A total of 24 patients were included. Standard of care (SOC) (before intervention) was prescribed in 14 patients, while 10 received SOC plus pulses of methylprednisolone (after intervention). The median age of patients was 64.5 years and 83.3% of the patients were men. The primary composite endpoint occurred in 13 patients (92.9%) who received SOC vs. 2 patients (20%) that received pulses of methylprednisolone (odds ratio, 0.02; 95% confidence interval, 0.001 to 0.25; p = 0.019). Length of hospitalization in survivors was shorter in the corticosteroids group (median, 14.5 [8.5-21.8] days vs. 29 [23-31] days, p = 0.003). There were no differences in the development of infections between both groups. There were 3 deaths, none of them in the corticosteroids group.

Conclusions

In patients with severe pneumonia due to COVID-19, the administration of methylprednisolone pulses was associated with a lower rate of OTI and/or death and a shorter hospitalization episode.

Echocardiographic Changes with Positive Airway Pressure Therapy in Obesity Hypoventilation Syndrome. Long-Term Pickwick Randomized Controlled Clinical Trial

Rationale: Obesity hypoventilation syndrome (OHS) has been associated with cardiac dysfunction. However, randomized trials assessing the impact of long-term noninvasive ventilation (NIV) or continuous positive airway pressure (CPAP) on cardiac structure and function assessed by echocardiography are lacking.Objectives: In a prespecified secondary analysis of the largest multicenter randomized controlled trial of OHS (Pickwick Project; N = 221 patients with OHS and coexistent severe obstructive sleep apnea), we compared the effectiveness of three years of NIV and CPAP on structural and functional echocardiographic changes.Methods: At baseline and annually during three sequential years, patients underwent transthoracic two-dimensional and Doppler echocardiography. Echocardiographers at each site were blinded to the treatment allocation. Statistical analysis was performed using a linear mixed-effects model with a treatment group and repeated measures interaction to determine the differential effect between CPAP and NIV.Measurements and Main Results: A total of 196 patients were analyzed: 102 were treated with CPAP and 94 were treated with NIV. Systolic pulmonary artery pressure decreased from 40.5 ± 1.47 mm Hg at baseline to 35.3 ± 1.33 mm Hg at three years with CPAP, and from 41.5 ± 1.56 mm Hg to 35.5 ± 1.42 with NIV (P < 0.0001 for longitudinal intragroup changes for both treatment arms). However, there were no significant differences between groups. NIV and CPAP therapies similarly improved left ventricular diastolic dysfunction and reduced left atrial diameter. Both NIV and CPAP improved respiratory function and dyspnea.Conclusions: In patients with OHS who have concomitant severe obstructive sleep apnea, long-term treatment with NIV and CPAP led to similar degrees of improvement in pulmonary hypertension and left ventricular diastolic dysfunction.Clinical trial registered with www.clinicaltrials.gov (NCT01405976).

Long-term Noninvasive Ventilation in Obesity Hypoventilation Syndrome Without Severe OSA: The Pickwick Randomized Controlled Trial

BACKGROUND

Noninvasive ventilation (NIV) is an effective form of treatment in obesity hypoventilation syndrome (OHS) with severe OSA. However, there is paucity of evidence in patients with OHS without severe OSA phenotype.

RESEARCH QUESTION

Is NIV effective in OHS without severe OSA phenotype?

STUDY DESIGN AND METHODS

In this multicenter, open-label parallel group clinical trial performed at 16 sites in Spain, we randomly assigned 98 stable ambulatory patients with untreated OHS and apnea-hypopnea index < 30 events/h (ie, no severe OSA) to NIV or lifestyle modification (control group) using simple randomization through an electronic database. The primary end point was hospitalization days per year. Secondary end points included other hospital resource utilization, incident cardiovascular events, mortality, respiratory functional tests, BP, quality of life, sleepiness, and other clinical symptoms. Both investigators and patients were aware of the treatment allocation; however, treating physicians from the routine care team were not aware of patients' enrollment in the clinical trial. The study was stopped early in its eighth year because of difficulty identifying patients with OHS without severe OSA. The analysis was performed according to intention-to-treat and per-protocol principles and by adherence subgroups.

RESULTS

Forty-nine patients in the NIV group and 49 in the control group were randomized, and 48 patients in each group were analyzed. During a median follow-up of 4.98 years (interquartile range, 2.98-6.62), the mean hospitalization days per year ± SD was 2.60 ± 5.31 in the control group and 2.71 ± 4.52 in the NIV group (adjusted rate ratio, 1.07; 95% CI, 0.44-2.59; P = .882). NIV therapy, in contrast with the control group, produced significant longitudinal improvement in Paco₂, pH, bicarbonate, quality of life (Medical Outcome Survey Short Form 36 physical component), and daytime sleepiness. Moreover, per-protocol analysis showed a statistically significant difference for the time until the first ED visit favoring NIV. In the subgroup with high NIV adherence, the time until the first event of hospital admission, ED visit, and mortality was longer than in the low adherence subgroup. Adverse events were similar between arms.

INTERPRETATION

In stable ambulatory patients with OHS without severe OSA, NIV and lifestyle modification had similar long-term hospitalization days per year. A more intensive program aimed at improving NIV adherence may lead to better outcomes. Larger studies are necessary to better determine the long-term benefit of NIV in this subgroup of OHS.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01405976; URL: www.clinicaltrials.gov.

Long-term Effect of CPAP Treatment on Cardiovascular Events in Patients With Resistant Hypertension and Sleep Apnea. Data From the HIPARCO-2 Study

BACKGROUND

There is some controversy about the effect of continuous positive airway pressure (CPAP) on the incidence of cardiovascular events (CVE). However, the incidence of CVE among patients with both obstructive sleep apnea (OSA) ans resistant hypertension (HR) has not been evaluated. Our objective was to analyze the long-term effect of CPAP treatment in patients with RH and OSA on the incidence of CVE.

METHODS

Multi-center, observational and prospective study of patients with moderate-severe OSA and RH. All the patients were followed up every 3-6 months and the CVE incidence was measured. Patients adherent to CPAP (at least 4h/day) were compared with those with not adherent or those who had not been prescribed CPAP.

RESULTS

Valid data were obtained from 163 patients with 64 CVE incidents. Treatment with CPAP was offered to 82%. After 58 months of follow-up, 58.3% of patients were adherent to CPAP. Patients not adherent to CPAP presented a non-significant increase in the total CVE incidence (HR:1.6; 95%CI: 0.96-2.7; p=0.07). A sensitivity analysis showed that patients not adherent to CPAP had a significant increase in the incidence of cerebrovascular events (HR: 3.1; CI95%: 1.07-15.1; p=0.041) and hypertensive crises (HR: 5.1; CI95%: 2.2-11.6; p=0.006), but the trend went in the opposite direction with respect to coronary events (HR: 0.22; CI95%: 0.05-1.02; p=0.053).

CONCLUSIONS

In patients with RH and moderate-severe OSA, an uneffective treatment with CPAP showed a trend toward an increase in the incidence of CVE (particularly neurovascular events and hypertensive crises) without any changes with respect to coronary events.

Experimental Approach to Examine Leptin Signaling in the Carotid Bodies and its Effects on Control of Breathing

An adipocyte-produced hormone leptin is a potent respiratory stimulant, which may play an important role in defending respiratory function in obesity. The carotid bodies (CB), a key organ of peripheral hypoxic sensitivity, express the long functional isoform of leptin receptor (LepR^b) but the role of leptin signaling in control of breathing has not been fully elucidated. We examined the hypoxic ventilatory response (HVR) (1) in C57BL/6J mice before and after leptin infusion at baseline and after CB denervation; (2) in LepR^b-deficient obese db/db mice at baseline and after LepR^b overexpression in CBs. In C57BL/6J mice, leptin increased HVR and effects of leptin on HVR were abolished by CB denervation. In db/db mice, LepR^b expression in CB augmented the HVR. Therefore, we conclude that leptin acts in CB to augment responses to hypoxia.

Relationship between the endothelial dysfunction and the expression of the β1-subunit of BK channels in a non-hypertensive sleep apnea group

STUDY OBJECTIVES

Vascular damage must be diagnosed early in patients with hypertension. In this regard, endothelial dysfunction (ED) is an early sign of vascular disease and a predictor of cardiovascular diseases. In obstructive sleep apnea (OSA), intermittent hypoxia triggers ED, but mechanisms are not clear. In this context, it has been described that BK channels regulates arterial tone and that chronic and intermittent hypoxia downregulates the expression of the BK channel β1-subunit facilitating vasoconstriction. Thus, we investigated the relationship among hypoxemia, ED, and mRNA expression of the β1-subunit in patients with severe OSA. We aimed to assess (1) ED in non-hypertensive patients with OSA using laser-Doppler flowmetry, (2) BK β1-subunit mRNA expression, and (3) the impact of continuous positive airway pressure (CPAP) treatment on ED and β1-subunit regulation.

METHODS

OSA patients underwent 24-hour blood pressure monitoring to exclude hypertension. Laser-Doppler flowmetry was performed to assess ED, and β1-subunit mRNA expression was evaluated using a blood test of peripheral blood leukocytes at baseline and after 3 months of CPAP treatment.

RESULTS

In normotensive patients with OSA, endothelial function correlated with the severity of OSA. CPAP improved endothelial function in normotensive OSA patients and the speed of the arterial response was significantly correlated with β1-subunit mRNA expression. β1-subunit mRNA expression at baseline correlated inversely with its change after CPAP.

CONCLUSIONS

Sleep apnea is related to ED in normotensive patients with OSA. CPAP therapy improves endothelial function and regulates β1-subunit mRNA expression.

Sleep-disordered breathing in C57BL/6J mice with diet-induced obesity

Obesity leads to sleep-disordered breathing (SDB) manifested by recurrent upper airway obstructions termed obstructive sleep apnea (OSA) and carbon dioxide retention due to hypoventilation. The objective of this work was to characterize breathing during sleep in C57BL6/J mice with diet-induced obesity (DIO). Arterial blood gas was measured in nine obese and nine lean mice during wakefulness. Nine male mice with DIO and six lean male C57BL/6J mice were head mounted with electroencephalogram (EEG) and electromyogram (EMG) electrodes. Sleep recordings were performed in the whole body plethysmography chamber; upper airway obstruction was characterized by the presence of inspiratory flow limitation in which airflow plateaus with increases in inspiratory effort. Obese mice showed significantly lower pH and higher partial pressure of arterial CO2 (PaCO2) in arterial blood gas compared to lean mice, 7.35 ± 0.04 versus 7.46 ± 0.06 (p < 0.001) and 38 ± 8 mm Hg versus 30 ± 5 mm Hg (p < 0.001). Obese mice had similar levels of minute ventilation to lean mice during sleep and wakefulness, despite higher body weight and temperature, indicating an increase in the metabolic rate and hypoventilation. Obese mice also showed baseline hypoxemia with decreased mean oxyhemoglobin saturation across sleep/wake states. Obese mice had a higher prevalence of flow-limited breathing compared to lean mice during sleep. However, the oxygen desaturation index in lean and obese mice did not differ. We conclude that DIO in mice leads to hypoventilation. Obesity also increases the frequency of inspiratory limited breaths, but it does not translate into progression of OSA.

Long-term clinical effectiveness of continuous positive airway pressure therapy versus non-invasive ventilation therapy in patients with obesity hypoventilation syndrome: a multicentre, open-label, randomised controlled trial

BACKGROUND

Obesity hypoventilation syndrome is commonly treated with continuous positive airway pressure or non-invasive ventilation during sleep. Non-invasive ventilation is more complex and costly than continuous positive airway pressure but might be advantageous because it provides ventilatory support. To date there have been no long-term trials comparing these treatment modalities. We therefore aimed to determine the long-term comparative effectiveness of both treatment modalities.

METHODS

We did a multicentre, open-label, randomised controlled trial at 16 clinical sites in Spain. We included patients aged 15-80 years with untreated obesity hypoventilation syndrome and an apnoea-hypopnoea index of 30 or more events per h. We randomly assigned patients, using simple randomisation through an electronic database, to receive treatment with either non-invasive ventilation or continuous positive airway pressure. Both investigators and patients were aware of the treatment allocation. The research team was not involved in deciding hospital treatment, duration of treatment in the hospital, and adjustment of medications, as well as adjudicating cardiovascular events or cause of mortality. Treating clinicians from the routine care team were not aware of the treatment allocation. The primary outcome was the number of hospitalisation days per year. The analysis was done according to the intention-to-treat principle. This study is registered with ClinicalTrials.gov, number NCT01405976.

FINDINGS

From May 4, 2009, to March 25, 2013, 100 patients were randomly assigned to the non-invasive ventilation group and 115 to the continuous positive airway pressure group, of which 97 patients in the non-invasive ventilation group and 107 in the continuous positive airway pressure group were included in the analysis. The median follow-up was 5·44 years (IQR 4·45-6·37) for all patients, 5·37 years (4·36-6·32) in the continuous positive airway pressure group, and 5·55 years (4·53-6·50) in the non-invasive ventilation group. The mean hospitalisation days per patient-year were 1·63 (SD 3·74) in the continuous positive airway pressure group and 1·44 (3·07) in the non-invasive ventilation group (adjusted rate ratio 0·78, 95% CI 0·34-1·77; p=0·561). Adverse events were similar between both groups.

INTERPRETATION

In stable patients with obesity hypoventilation syndrome and severe obstructive sleep apnoea, non-invasive ventilation and continuous positive airway pressure have similar long-term effectiveness. Given that continuous positive airway pressure has lower complexity and cost, continuous positive airway pressure might be the preferred first-line positive airway pressure treatment modality until more studies become available.

FUNDING

Instituto de Salud Carlos III, Spanish Respiratory Foundation, and Air Liquide Spain.

Beyond Resistant Hypertension

Obstructive sleep apnea (OSA) is an independent cause of resistant hypertension (RH) but its association with refractory hypertension (RfH), a recently described form of severe hypertension, has not yet been investigated. This study seeks to analyze the association between the presence and severity of OSA/OSA syndrome with RfH and to compare it with a group of patients with OSA/OSA syndrome and RH. We conducted a multicenter, cross-sectional study of consecutive patients diagnosed with RH by means of 24-hour ambulatory blood pressure monitoring. Those patients with blood pressure levels ≥130/80 mm Hg, despite taking at least 5 antihypertensive drugs, were considered to have true RfH. All patients underwent a sleep study and completed a detailed clinical history related to OSA, current medication, and cardiovascular diseases. Overall, 229 patients were included (mean age, 58.3 years; 63% male), of whom 42 (18.3%) satisfied the criteria for RfH. Compared with those with RH, patients with RfH had a higher cardiovascular risk profile, higher blood pressure measurements, and a 2-fold greater risk of having both severe OSA (odds ratio, 2.1, with a prevalence of apnea-hypopnea index ≥15, 95.2% and apnea-hypopnea index ≥30, 64.3%) and OSA syndrome (apnea-hypopnea index ≥5+Epworth Sleepiness Scale >10; odds ratio, 1.9; 52.4% versus 37.3%; P=0.023), as well as higher OSA severity (apnea-hypopnea index, 41.8 versus 33.8 events/h; P=0.026). Patients with RfH had an even greater prevalence and severity of OSA and OSA syndrome than RH patients, highlighting the need to identify these patients to refer them to sleep units on a preferential basis.

Good long-term adherence to continuous positive airway pressure therapy in patients with resistant hypertension and sleep apnea

Although adequate adherence is paramount in achieving the beneficial effects of continuous positive airway pressure therapy in patients with obstructive sleep apnea, long-term adherence and the variables involved in continuous positive airway pressure compliance in patients with resistant hypertension and obstructive sleep apnea are yet unknown. We conducted a prospective, multicentre, observational study in 177 patients recruited from hypertensive units with resistant hypertension confirmed by means of 24-hr blood pressure monitoring (blood pressure ≥ 130 and/or ≥ 80 mmHg, despite taking at least three antihypertensive drugs or < 130/80 mmHg with > 3 drugs) and obstructive sleep apnea (apnea-hypopnea index ≥ 5 in a respiratory polygraph) who were prescribed continuous positive airway pressure treatment. Good adherence was defined as an average cumulative continuous positive airway pressure use of ≥ 4 hr per night at the end of the follow-up. A multivariate Cox regression analysis was performed to identify independent predictors of continuous positive airway pressure adherence. Patients were followed for a median of 57.6 (42-72) months after initiating continuous positive airway pressure therapy. At the end of the follow-up, the median continuous positive airway pressure use was 5.7 (inter-quartile range 3.9-6.6) hr per night, and 132 patients (74.5%) showed good continuous positive airway pressure adherence. The only baseline variable associated with poor adherence was the presence of previous stroke (hazard ratio 4.00, 95% confidence interval 1.92-8.31). Adequate adherence at 1 month also predicted good adherence at the end of the follow-up (hazard ratio 14.4, 95% confidence interval 4.94-56). Both variables also predicted adherence at a threshold of 6 hr per night. Our results show that good continuous positive airway pressure adherence is an achievable and feasible goal in patients with resistant hypertension and obstructive sleep apnea. Previous stroke and short-term adherence predicted long-term adherence.

Leptin acts in the carotid bodies to increase minute ventilation during wakefulness and sleep and augment the hypoxic ventilatory response

KEY POINTS

Leptin is a potent respiratory stimulant. A long functional isoform of leptin receptor, LepR^b , was detected in the carotid body (CB), a key peripheral hypoxia sensor. However, the effect of leptin on minute ventilation (V_E ) and the hypoxic ventilatory response (HVR) has not been sufficiently studied. We report that LepR^b is present in approximately 74% of the CB glomus cells. Leptin increased carotid sinus nerve activity at baseline and in response to hypoxia in vivo. Subcutaneous infusion of leptin increased V_E and HVR in C57BL/6J mice and this effect was abolished by CB denervation. Expression of LepR^b in the carotid bodies of LepR^b deficient obese db/db mice increased V_E during wakefulness and sleep and augmented the HVR. We conclude that leptin acts on LepR^b in the CBs to stimulate breathing and HVR, which may protect against sleep disordered breathing in obesity.

ABSTRACT

Leptin is a potent respiratory stimulant. The carotid bodies (CB) express the long functional isoform of leptin receptor, LepR^b , but the role of leptin in CB has not been fully elucidated. The objectives of the current study were (1) to examine the effect of subcutaneous leptin infusion on minute ventilation (V_E ) and the hypoxic ventilatory response to 10% O₂ (HVR) in C57BL/6J mice before and after CB denervation; (2) to express LepR^b in CB of LepR^b -deficient obese db/db mice and examine its effects on breathing during sleep and wakefulness and on HVR. We found that leptin enhanced carotid sinus nerve activity at baseline and in response to 10% O₂ in vivo. In C57BL/6J mice, leptin increased V_E from 1.1 to 1.5 mL/min/g during normoxia (P < 0.01) and from 3.6 to 4.7 mL/min/g during hypoxia (P < 0.001), augmenting HVR from 0.23 to 0.31 mL/min/g/Δ F I O 2 (P < 0.001). The effects of leptin on V_E and HVR were abolished by CB denervation. In db/db mice, LepR^b expression in CB increased V_E from 1.1 to 1.3 mL/min/g during normoxia (P < 0.05) and from 2.8 to 3.2 mL/min/g during hypoxia (P < 0.02), increasing HVR. Compared to control db/db mice, LepR^b transfected mice showed significantly higher V_E throughout non-rapid eye movement (20.1 vs. -27.7 mL/min respectively, P < 0.05) and rapid eye movement sleep (16.5 vs 23.4 mL/min, P < 0.05). We conclude that leptin acts in CB to augment V_E and HVR, which may protect against sleep disordered breathing in obesity.

Obstructive sleep apnoea syndrome, endothelial function and markers of endothelialization. Changes after CPAP

Study objectives

This study tries to assess the endothelial function in vivo using flow-mediated dilatation (FMD) and several biomarkers of endothelium formation/restoration and damage in patients with obstructive sleep apnoea (OSA) syndrome at baseline and after three months with CPAP therapy.

Design

Observational study, before and after CPAP therapy.

Setting and Patients

We studied 30 patients with apnoea/hypopnoea index (AHI) >15/h that were compared with themselves after three months of CPAP therapy. FMD was assessed non-invasively in vivo using the Laser-Doppler flowmetry. Circulating cell-free DNA (cf-DNA) and microparticles (MPs) were measured as markers of endothelial damage and the vascular endothelial growth factor (VEGF) was determined as a marker of endothelial restoration process.

Measurements and results

After three month with CPAP, FMD significantly increased (1072.26 ± 483.21 vs. 1604.38 ± 915.69 PU, p< 0.005) cf-DNA and MPs significantly decreased (187.93 ± 115.81 vs. 121.28 ± 78.98 pg/ml, p<0.01, and 69.60 ± 62.60 vs. 39.82 ± 22.14 U/μL, p<0.05, respectively) and VEGF levels increased (585.02 ± 246.06 vs. 641.11 ± 212.69 pg/ml, p<0.05). These changes were higher in patients with more severe disease. There was a relationship between markers of damage (r = -0.53, p<0.005) but not between markers of damage and restoration, thus suggesting that both types of markers should be measured together.

Conclusions

CPAP therapy improves FMD. This improvement may be related to an increase of endothelial restoration process and a decrease of endothelial damage.

Gamma glutamyl transferase and oxidative stress in obstructive sleep apnea: a study in 1744 patients

OBJECTIVE

We analyze a large population of patients to determine whether gamma glutamyl transferase (GGT) levels are increased in sleep apnea-hypopnea syndrome (OSA) and whether these levels are related to clinical characteristics or polygraphic indexes.

METHODS

A cross-sectional study in a population of 1744 patients referred for OSA suspicion was conducted. The following variables were determined: glucose, cholesterol, triglycerides, aspartate aminotransferase (GOT), alanine aminotransferase (GPT), GGT, body mass index, waist-hip ratio (WHR), and overnight sleep study.

RESULTS

The 483 patients with GGT ≥40 IU/l were younger and more obese, and had a pattern of more centrally distributed fat than the 1261 with GGT <40 IU/l. Patients with high levels of GGT also consumed more alcohol, had a poorer biochemical profile, and had more respiratory and oximetric alterations during sleep. GGT levels were significantly correlated with AHI, DI, and CT90. In the binary regression test, WHR, glucose, cholesterol, triglycerides, and grams of alcohol consumed per day predicted GGT levels ≥40 IU/l, while none of the polygraphic variables had predictive value.

CONCLUSIONS

High GGT levels were associated with the severity of OSA. However, this relationship seems to be due to the coexistence of other associated factors, mainly central obesity, rather than to the respiratory disorders found in this disease.

Glucose sensing by carotid body glomus cells: potential implications in disease

The carotid body (CB) is a key chemoreceptor organ in which glomus cells sense changes in blood O2, CO2, and pH levels. CB glomus cells have also been found to detect hypoglycemia in both non-primate mammals and humans. O2 and low-glucose responses share a common final pathway involving membrane depolarization, extracellular calcium influx, increase in cytosolic calcium concentration, and neurotransmitter secretion, which stimulates afferent sensory fibers to evoke sympathoadrenal activation. On the other hand, hypoxia and low glucose induce separate signal transduction pathways. Unlike O2 sensing, the response of the CB to low glucose is not altered by rotenone, with the low glucose-activated background cationic current unaffected by hypoxia. Responses of the CB to hypoglycemia and hypoxia can be potentiated by each other. The counter-regulatory response to hypoglycemia by the CB is essential for the brain, an organ that is particularly sensitive to low glucose. CB glucose sensing could be altered in diabetic patients, particularly those under insulin treatment, as well as in other medical conditions such as sleep apnea or obstructive pulmonary diseases, where chronic hypoxemia presents with plastic modifications in CB structure and function. The current review will focus on the following main aspects: (1) the CB as a low glucose sensor in both in vitro and in vivo models; (2) molecular and ionic mechanisms of low glucose sensing by glomus cells, (3) the interplay between low glucose and O2 sensing in CB, and (4) the role of CB low glucose sensing in the pathophysiology of cardiorespiratory and metabolic diseases, and how this may serve as a potential therapeutic target.