Continuous positive airway pressure for asthma: not a big stretch?

Contribution of Obstructive Sleep Apnea to Asthmatic Airway Inflammation and Impact of Its Treatment on the Course of Asthma

Asthma and obstructive sleep apnea (OSA) are very common respiratory disorders in the general population. Beyond their high prevalence, shared risk factors, and genetic linkages, bidirectional relationships between asthma and OSA exist, each disorder affecting the other's presence and severity. The author reviews here some of the salient links between constituents of the alternative overlap syndrome, that is, OSA comorbid with asthma, with an emphasis on the effects of OSA or its treatment on inflammation in asthma. In the directional relationship from OSA toward asthma, beyond direct influences, multiple factors and comorbidities seem to contribute.

Nocturnal bilevel positive airway pressure for the treatment of asthma

Nocturnal worsening of asthma may be due to reduced lung volumes and fewer sigh breaths, which have been shown to increase airway resistance and bronchoreactivity. We hypothesized that mimicking deep inspiration using nocturnal mechanical support would improve symptoms in patients with asthma. Subjects with asthma underwent usual care and bilevel positive airway pressure (PAP) therapy for 4 weeks, separated by 4 weeks, and methacholine challenge (PC20) and subjective assessments. 13 patients with asthma alone and 8 with asthma + OSA completed the protocol. Change in bronchoreactivity (ratio of Post/Pre PC20) was not significantly different during usual care and bilevel PAP [0.86 (IQR 0.19, 1.82) vs 0.94 (IQR 0.56, 2.5), p = 0.88], nor was the change in Asthma Control Test different: 0.1 ± 2.2 vs. -0.2 ± 2.9, p = 0.79, respectively. Bilevel PAP therapy for four weeks did not improve subjective or objective measures of asthma severity in patients with asthma or those with asthma and OSA, although there was heterogeneity in response.

[The problem of obstructive sleep apnea syndrome in asthmatic patients]

Asthma and obstructive sleep apnea syndrome (OSAS) are one of the most common chronic respiratory diseases. These have common risk factors that include obesity, gastroesophageal reflux disease (GERD) and impaired nasal breathing (allergic rhinitis, sinusitis). At the same time, experimental evidence demonstrates common pathophysiological mechanisms of these diseases, such as involvement in the process of the respiratory tract, a systemic inflammatory response, and implementation of neuromechanical reflexes. Thus, there is an obvious synergism between these conditions, which affects symptoms, response to therapy, and prognosis. The available data allow discussion on whether there is a need to identify and treat OSAS in asthmatic patients. By keeping in mind the high incidence of OSAS in patients with severe asthma, it may be suggested that treatment for OSAS can reduce the number of exacerbations, improve the quality of life, and decline the number of obstinate asthma cases. It is very important for general practitioners to assess risk factors, such as body weight, nasal stuffiness, and GERD, and to utilize screening tools for more efficient use of healthcare resources. Considering the known positive effects of CPAP therapy in short-term studies, future investigations should focus on the impact of CPAP therapy on asthma symptoms in the long-term, as well as on the effects of asthma drugs on the course of OSAS.

Characterization and redox mechanism of asthma in the elderly

Asthma is a chronic disease characterized by reversible airflow limitation, coughing, bronchial constriction, and an inflammatory immune response. While asthma has frequently been categorized as emerging in childhood, evidence has begun to reveal that the elderly population is certainly susceptible to late-onset, or even long-standing asthma. Non-atopic asthma, most commonly found in elderly patients is associated with elevated levels of serum and sputum neutrophils and may be more detrimental than atopic asthma. The mortality of asthma is high in the elderly since these patients often possess more severe symptoms than younger populations. The redox mechanisms that mediate inflammatory reactions during asthma have not been thoroughly interpreted in the context of aging. Thus, we review the asthmatic symptoms related to reactive oxygen species (ROS) and reactive nitrogen species (RNS) in seniors. Moreover, immune status in the elderly is weakened in part by immunosenescence, which is broadly defined as the decline in functionality of the immune system that corresponds with increasing age. The effects of immunosenescence on the expression of biomarkers potentially utilized in the clinical diagnosis of asthma remain unclear. It has also been shown that existing asthma treatments are less effective in the elderly. Thus, it is necessary that clinicians approach the diagnosis and treatment of asthmatic senior patients using innovative methods. Asthma in the elderly demands more intentional diagnostic and therapeutic research since it is potentially one of the few causes of mortality and morbidity in the elderly that is largely reversible.

Nocturnal continuous positive airway pressure in severe non-apneic asthma. A pilot study

INTRODUCTION

It has been demonstrated that brief periods of nocturnal continuous positive airway pressure (nCPAP) reduce airway reactivity in animal models and in patients with asthma. The effects of nCPAP in severe uncontrolled non-apneic asthmatic patients are not well known.

AIM

In this open pilot study, we aimed to assess the effect nCPAP on peak flow (PEF) variability and asthma control in this type of patients.

METHODS

CPAP was applied to 10 patients with severe long-standing asthma without obstructive sleep apnea for seven consecutive nights. CPAP was titrated in auto setting and applied to the patients. Daily PEF, was measured from 2 weeks before the intervention to 2 weeks after the end of nCPAP treatment. PEF amplitude and PEF morning dip (MD) over 24-h periods averaged over 1 week were calculated as indexes of PEF variability. Asthma control test (ACT) and European quality of life (EuroQol) questionnaire were measured at baseline and after 1 month, and at baseline and at the end of CPAP period, respectively.

RESULTS

The PEF amplitude significantly decreased both during CPAP period and in the first week after nCPAP discontinuation as compared with the baseline (19.8 ± 7.5%, 23.9 ± 9.1% and 28.9 ± 11.5%, respectively, always P < 0.05). PEF MD significantly decreased during nCPAP in comparison with the baseline (P < 0.001). The ACT and EuroQol significantly improved after nCPAP in comparison with the basal value.

CONCLUSIONS

In this preliminary report, brief period of nCPAP reduces PEF variability and improves control in severe non-apneic asthma at a short-term evaluation. Further studies with longer-term evaluation and larger number of patients are warranted.

Obstructive sleep apnea and asthma: associations and treatment implications

Obstructive sleep apnea (OSA) and asthma are highly prevalent respiratory disorders and are frequently co-morbid. Risk factors common to the two diseases include obesity, rhinitis, and gastroesophageal reflux (GER). Observational and experimental evidence implicates airways and systemic inflammation, neuromechanical effects of recurrent upper airway collapse, and asthma-controlling medications (corticosteroids) as additional explanatory factors. Therefore, undiagnosed or inadequately treated OSA may adversely affect control of asthma and vice versa. It is important for clinicians to be vigilant and specifically address weight-control, nasal obstruction, and GER in these populations. Utilizing validated screening instruments to affirm high risk of co-morbid OSA or asthma in persistently symptomatic patients will allow clinicians to cost-effectively test and treat appropriate patients, potentially improving outcomes. While non-invasive ventilation in acute asthma improves outcomes, the role of chronic continuous positive airway pressure (CPAP; the first-line treatment for OSA) in improving long-term asthma control is not known. Future research should focus on the impact of optimal CPAP therapy and adherence on asthma symptoms and outcomes.

Obesity and asthma

Asthma is a chronic disorder affecting millions of people worldwide. The prevalence of asthma is around 300 million and is expected to increase another 100 million by 2025. Obesity, on the other hand, also affects a large number of individuals. Overweight in adults is defined when body mass index (BMI) is between 25 to 30 kg/m(2) and obesity when the BMI >30 kg/m(2). It has been a matter of interest for researchers to find a relation between these two conditions. This knowledge will provide a new insight into the management of both conditions. At present, obese asthma patients may be considered a special category and it is important to assess the impact of management of obesity on asthma symptoms.

Association of obstructive sleep apnea risk or diagnosis with daytime asthma in adults

OBJECTIVE

Obstructive sleep apnea (OSA) worsens nocturnal asthma, but its potential impact on daytime asthma remains largely unassessed. We investigated whether the sleep disorder is associated with daytime, in addition to nighttime, asthma symptoms.

METHODS

Asthma patients at tertiary-care centers completed the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ), and an asthma control questionnaire. SA-SDQ scores ≥36 for males and ≥32 for females defined high OSA risk. Medical records were reviewed for established diagnosis of OSA and continuous positive airway pressure (CPAP) use.

RESULTS

Among 752 asthma patients, high OSA risk was associated similarly with persistent daytime and nighttime asthma symptoms (p < .0001 for each). A diagnosis of OSA was robustly associated with persistent daytime (p < .0001) in addition to nighttime (p = .0008) asthma symptoms. In regression models that included obesity and other known asthma aggravators, high OSA risk retained associations with persistent daytime (odds ratio [OR] = 1.96 [95% confidence interval [CI] = 1.31-2.94]) and nighttime (1.97 [1.32-2.94]) asthma symptoms. Diagnosed OSA retained an association with persistent daytime (2.08 [1.13-3.82]) but not with nighttime (1.48 [0.82-2.69]) asthma symptoms. CPAP use was associated with lower likelihood of persistent daytime symptoms (0.46 [0.23-0.94]).

CONCLUSIONS

Questionnaire-defined OSA risk and historical diagnosis were each associated with persistent daytime asthma symptoms, to an extent that matched or exceeded associations with nighttime asthma symptoms. Unrecognized OSA may be a reason for persistent asthma symptoms during the day as well as the night.

Upper airway function in the pathogenesis of obstructive sleep apnea: a review of the current literature

PURPOSE OF REVIEW

Obstructive sleep apnea is an increasingly prevalent disease, with a considerable societal burden. The disease is defined by recurrent intermittent collapse of the upper airway. Understanding of and treatment for the disease is largely confined to relief of the mechanical obstruction of the upper airway by application of continuous positive airway pressure, and less commonly weight loss or surgery. However, recent work has focused on the function, rather than structure alone, of the upper airway.

RECENT FINDINGS

The following contributors to upper airway structure and function have been studied: traditional fixed anatomical abnormalities, dynamic anatomical changes, upper airway dilator muscle dysfunction, lung volumes, and instability in control of breathing. In each patient with obstructive sleep apnea, the relative contribution of each of these components may be quite variable. The studies reviewed here describe methods to evaluate these factors, and some attempts at treatment.

SUMMARY

Ongoing studies are attempting to classify patients on the basis of the underlying pathophysiology. This work suggests that obstructive sleep apnea is a heterogeneous disease with multiple root causes. Ultimately, such a classification may allow more individualized treatment, not only relying on mechanical relief of the upper airway obstruction.

Obesity and the lung: 3. Obesity, respiration and intensive care

Obesity is a major problem from a public health perspective and a difficult practical matter for intensivists. The obesity pandemic has required treating clinicians to develop an appreciation of the substantial pathophysiological effects of obesity on the various organ systems. The important physiological concepts are illustrated by focusing on obstructive sleep apnoea, obesity hypoventilation syndrome, abdominal compartment syndrome and ventilatory management of the obese patient with acute respiratory distress syndrome.

Obesity and asthma: possible mechanisms

Epidemiologic data indicate that obesity increases the prevalence and incidence of asthma and reduces asthma control. Obese mice exhibit innate airway hyperresponsiveness and augmented responses to certain asthma triggers, further supporting a relationship between obesity and asthma. Here I discuss several mechanisms that may explain this relationship. In obesity, lung volume and tidal volume are reduced, events that promote airway narrowing. Obesity also leads to a state of low-grade systemic inflammation that may act on the lung to exacerbate asthma. Obesity-related changes in adipose-derived hormones, including leptin and adiponectin, may participate in these events. Comorbidities of obesity, such as dyslipidemia, gastroesophageal reflux, sleep-disordered breathing, type 2 diabetes, or hypertension may provoke or worsen asthma. Finally, obesity and asthma may share a common etiology, such as common genetics, common in utero conditions, or common predisposing dietary factors. Novel therapeutic strategies for treatment of the obese patient with asthma may result from an increased understanding of the mechanisms underlying this relationship.