Continuous Positive Airway Pressure Use in Asthma With Moderate to Severe Obstructive Sleep Apnea Patients
Condition: OSA
MeSH terms: Sleep Apnea, Obstructive
Study type: Interventional

Summary: 
      Obstructive sleep apnea syndrome (OSAS) and asthma are both common disorders in Hong Kong,
      with prevalence of at least 4% among the middle-aged male Hong Kong (HK) Chinese populations
      and 7.2% in young adults respectively. OSAS is characterized by repetitive episodes of upper
      airway obstruction, causing intermittent hypoxia, sleep fragmentation, disabling daytime
      sleepiness, impaired cognitive function and poor health status. Continuous positive airway
      pressure (CPAP) is the first line of therapy for sleep apnea. CPAP provides a pneumatic stent
      for the upper airway, eliminating the airway collapse during inspiration.

      Asthma is a chronic inflammatory disorder of airways, characterized by airway
      hyperresponsiveness that leads to recurrent episodes of wheezing, breathless, chest
      tightness, and coughing, particularly at night or in the early morning. Nocturnal asthma is
      not a different condition from asthma and is defined as a variable worsening of asthma at
      night, in which the mechanisms are not completely understood.

      The prevalence of OSAS in asthmatic patients has not yet been studied, but several studies
      have reported an increased prevalence of OSAS symptoms in asthmatic patients. OSAS and asthma
      share some common risk factors, which include obesity, gastroesophageal reflux and rhinitis.
      CPAP treatment has been shown in prospective clinical studies to have a positive impact on
      asthma outcome in patients with concomitant OSAS, for example, improvement of asthma related
      quality of life in subjects with stable mild-to-moderate asthma, but there was no change in
      the airway responsiveness or forced expiratory volume in one second. Although important,
      these studies included small numbers of participants used nonrandomized designs. This study
      is to assess the impact of CPAP treatment on asthma control among patients with nocturnal
      symptoms and moderate OSAS.
    

Detailed description: 
      Obstructive sleep apnea syndrome (OSAS) and asthma are both common disorders in Hong Kong,
      with prevalence of at least 4% among the middle-aged male Hong Kong (HK) Chinese populations
      and 7.2% in young adults respectively. OSAS is characterized by repetitive episodes of upper
      airway obstruction, causing intermittent hypoxia, sleep fragmentation, disabling daytime
      sleepiness, impaired cognitive function and poor health status. Continuous positive airway
      pressure (CPAP) is the first line of therapy for sleep apnea. CPAP provides a pneumatic stent
      for the upper airway, eliminating the airway collapse during inspiration.

      Asthma is a chronic inflammatory disorder of airways, characterized by airway
      hyperresponsiveness that leads to recurrent episodes of wheezing, breathless, chest
      tightness, and coughing, particularly at night or in the early morning. Nocturnal asthma is
      not a different condition from asthma and is defined as a variable worsening of asthma at
      night, in which the mechanisms are not completely understood. It may be driven by circadian
      rhythms of circulating hormones such as epinephrine, cortisol, and melatonin and neural
      mechanisms such as cholinergic tone. An increase in airway inflammation at night has been
      reported. This might reflect a reduction in endogenous anti-inflammatory mechanisms. Other
      factors that have been proposed as possible causes for overnight bronchoconstriction are
      interruption of bronchodilator or other treatment, allergens in bedding, airway cooling,
      supine posture, and gastroesophageal reflux (GER).

      Prevalence of OSAS in asthma: The prevalence of OSAS in asthmatic patients has not yet been
      studied, but several studies have reported an increased prevalence of OSAS symptoms in
      asthmatic patients. Large epidemiologic studies demonstrated that asthma patients are more
      frequently report snoring. In a longitudinal study, asthma was an independent risk factor for
      development of snoring. OSAS symptoms are highly prevalent in clinic-based populations of
      well-characterized asthma patients. Polysomnography revealed high frequencies of OSAS (88%
      and 95.5%) in patients with difficult-to-control asthma.

      Common risk factors contributing OSAS asthma: OSAS and asthma share some common risk factors.
      Fifty percent of the obese in Caucasian populations have OSAS, and among those with OSAS, 40%
      are obese. However, in a community study of sleep-disordered breathing in middle-aged Chinese
      men in Hong Kong, the average body mass index (BMI) of habitual snorer was 25.1 kg/m2 and
      that of OSAS was 27kg/m2, making the contribution of obesity in OSAS less as important as in
      the western counterpart. Apart from obesity, the prevalence of GER is increased in patients
      with OSAS. It has been suggested that obesity contributes to the same risk factors for OSAS
      and GER. However, OSAS patients exhibit significantly more GER than do members of the average
      population even when one controls for alcohol intake and BMI. GER occurring during sleep is a
      well-known trigger for nocturnal asthma and can provoke asthma symptoms through vagal
      reflexes induced by exposure of the esophagus to acid. OSAS-induced acid reflux may play a
      causative role in triggering asthma symptoms. Another possible etiology for the high
      prevalence of OSAS symptoms in asthmatic patients is the increased incidence of nasal
      obstruction in asthmatic patients. The nose is preferred breathing route during sleep, and
      nasal obstruction contributes to sleep disordered breathing in predisposed individuals.
      Rhinitis and chronic sinusitis are common conditions that may cause nasal congestion and
      consequently contribute to upper airway obstruction in OSAS.

      The effect of CPAP treatment on asthma control:

      CPAP treatment has been shown in prospective clinical studies to have a positive impact on
      asthma outcome in patients with concomitant OSAS. Although important, these studies included
      small numbers of participants used nonrandomized designs.

      We hypothesize that OSAS contribute to the symptoms related to nocturnal asthma and that CPAP
      therapy would improve the asthma symptoms, airway hyperactivity and quality of life in
      patients with nocturnal asthma and OSAS. We aim to assess (1) asthma control, airway
      responsiveness, daytime sleepiness, cognitive function and health status at baseline and at 3
      months after nasal CPAP treatment among our asthma patients with nocturnal symptoms and OSAS;
      (2) the acceptance and compliance of nasal CPAP treatment.
    

Intervention name(s): CPAP group; non CPAP group
Intervention type(s): Procedure; Procedure
Intervention description(s): Patients will be given a CPAP education program by our respiratory nurse supplemented by education brochure and a video. Attended overnight CPAP titration will be performed with the auto-titrating device. The CPAP level for each patient in the therapeutic CPAP arm is set at the minimum pressure needed to abolish snoring, obstructive respiratory events and airflow limitation for 95% of the night as determined by the overnight CPAP titration study. Patients in the CPAP therapy will be provided careful mask-fitting, chin strap to prevent mouth leak, regular review by our nurses, a basic CPAP device with intrinsic time clock to monitor CPAP usage and standard stroke rehabilitation programme. Patients on conservative treatment will only be offered standard treatment for asthma; Patients who are randomised to non CPAP group will receive general health advice and no CPAP therapy will be arranged for them during the study period.
Other intervention name(s): CPAP intervention group; No CPAP given
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Investigator)
Primary purpose: Treatment