Affiliations: Sanno Hospital
Tokyo University Hospital Tokyo, Japan,
Uppsala University Uppsala, Sweden
Vifilsstadir Hospital Gardabaer, Iceland
Correspondence to: Shinji Teramoto, MD, FCCP, Dept. Geriatric Medicine, University of Tokyo Hospital, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8655, Japan; e-mail: firstname.lastname@example.org
To the Editor:
In a recent issue of CHEST (January 2002), Gislason and coworkers1demonstrated that the occurrence of gastroesophageal reflux (GER) after bedtime is strongly associated with both asthma and respiratory symptoms, as well as with symptoms of obstructive sleep apnea syndrome (OSAS). Further, Palombini and colleagues2 reported that asthma, postnasal drip syndrome (PNDS), and gastroesophageal reflux disease (GERD), alone or in combination, were responsible for > 90% of the causes of chronic cough. Thus, a variety of respiratory symptoms are associated with GER.
However, the mechanisms of the linkage of GER and respiratory symptoms are not fully elucidated. We have reported that GER is frequently found in patients with OSAS.3–4 The swallowing reflex is impaired in patients with OSAS, suggesting that OSAS may perturb the inspiratory-expiratory transition during deglutition in the patients.4Indeed, many patients with OSAS complain of sleep-related heartburn and regurgitation of gastric contents into the pharynx.5It has been reported that treatment with nasal continuous positive airway pressure (nCPAP) at night can correct the sleep apnea-related GER in patients with OSAS.6–7 We further reported that nocturnal oxyhemoglobin desaturation and hypercapnia were associated with the impaired swallowing function in patients with OSAS.8 Because the upper airway function is inhibited by hypoxia and hypercapnia, nocturnal disturbed breathing often causes chronic hypoxia and hypercapnia, which lead to damage of upper airways in the patients, resulting in the impaired swallowing reflex.
Because OSAS and GER may aggravate bronchial asthma, it is more difficult to control asthma in such patients. There is a possible pathologic link, through GER, between chronic cough and OSAS in young and adult patients.9–10 In these patients, treatment with nCPAP at night is reported to improve control of asthmatic condition.11–12 These GER-related respiratory symptoms should be carefully considered in many obese patients with pulmonary diseases including asthma, posterior laryngitis, and nocturnal chronic coughing.
We are grateful for the comments from Teramoto et al that gastroesophageal reflux (GER) is an important determinant for both obstructive sleep apnea and asthma. Like the authors of the comment above, we have previously found an association between GER and chronic cough.1We have also previously reported that GER is related to daytime sleepiness and insomnia.2–3
We agree that the mechanism behind the association between GER and respiratory symptoms needs to be further elucidated. In our recent paper in CHEST,4 we suggested that the association may be partly explained by the swings in intrathoracic pressure caused by partial narrowing or complete occlusion of the upper airway during sleep, a condition which is present in patients suffering from the upper airway resistance syndrome or the obstructive sleep apnea syndrome (OSAS). We are grateful to Teramoto et al for bringing to our attention their important findings of an impaired swallowing reflex in patients with OSAS. The combination of the intrathoracic pressure swing and an impaired swallowing reflex would increase the risk of microaspirations of gastric fluid and would be a plausible explanation for the association between GER and respiratory symptoms.
We also fully agree that GER should be considered as a possible underlying disorder in obese patients with respiratory symptoms
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