Bronchial asthma-related night-time symptoms
Bronchial disturbances during sleep are observed in most patients with bronchial asthma. While some patients have bronchial obstruction during sleep, which is a continuation of bronchial permeability disorders that occur during awakening, others have isolated or predominant bronchial obstruction during sleep.
There are several theories explaining these daily variations in bronchial obstructive movement during night–time sleep in patients with bronchial asthma.
To some extent, this may be a reflection of natural circadian fluctuations in bronchial permeability. For example, the Hetzel M.R. et al. (1980) showed that both healthy individuals and patients with bronchial asthma had the same type of daily variation in bronchial permeability with the onset or increase of bronchial obstruction during night–time sleep. In addition, according to P. Gervais et al. (1977), which is one of the most important links of asthma pathogenesis, bronchial hyperreactivity also has its own daily rhythm and is maximal at night. It is suggested that the increasing hyperreactivity of the bronchi leads to the fact that the same natural physiological stimuli, which in healthy people lead to only a slight decrease in the diameter of the bronchi, in asthma patients are realized in the form of clinically significant bronchospasm during sleep. As a result, while healthy sleep obstructions are minimal and subclinical, asthma can be significant in patients with asthma, which is manifested by a wide range of bronchial asthma–related night–time symptoms.
Since in many cases these patients suffer from atopic disease, the role of allergens surrounding the patient in bed is suggestive. In addition, there is evidence that the severity of the allergic response is subject to circadian fluctuations. In the study, the intensity of atopic reactions was maximal late in the evening and minimal in the morning. Our experience shows that measures to eliminate allergens from the bedroom include the use of special bed linen, regular wet cleaning, etc. – can significantly reduce the severity of night–time symptoms in some patients. On the other hand, in many patients the elimination of contact with potentially dangerous allergens does not prevent night–time bronchospasm. Moreover, as shown by C.K. Connolly (1979) disorders of bronchial permeability during sleep are equally common in patients with allergic and non–allergic forms of bronchial asthma. According to N. J. Douglas (2011) allergic reactions are only one of the mechanisms to promote night–time symptoms of bronchial asthma and can play a significant role, but only in a few patients. At the same time, the author suggests that in patients with night asthma, the consequences of contact with allergens are more realized not directly, but through the development of inflammatory response and subsequent increase in bronchial hyperreactivity, which creates prerequisites for the emergence of bronchial obstruction during sleep.
Cold and dry air is a well–known non–specific irritant that can cause impaired bronchial flow in many asthmatic patients. There is a theory that asthma symptoms during sleep may be partly caused by inhaling cooler night air. So in the W.Y. study. Chen et al. (1982) has shown that warming and moisturizing the bedroom air prevents the onset of night–time asthma symptoms in the majority of patients who had previously experienced bronchial obstruction while sleeping with normal room air. However, although in our country there is no tradition, typical for many Western Europeans, to turn off heating at home during sleep, the problem of asthma at night does not become less urgent for Russian patients. It seems that the key point in this case is not so much the temperature as the humidity of the inhaled air. This is supported by the fact that many of the patients we observe empirically come to the necessity to use devices to moisturise the home air during the winter heating season.
According to S.J. Sontag (1997) and others, gastroesophageal reflux is common in patients with bronchial asthma. The presence of respiratory complaints, primarily chronic unproductive coughing, in patients with gastroesophageal reflux disease is well known and has been described in detail in the literature. According to modern notions, the cause of these symptoms is stimulation of vagus receptors of the distal esophagus, sometimes in combination with microaspiration of the gastric content in the upper respiratory tract and lumen of the bronchial tree. According to several authors, the number of pathological refluxes increases during night–time sleep, which, in their opinion, may be due to the circadian rhythm of hydrochloric acid secretion in the stomach, which peaks between 0 and 4 a.m., lower esophageal sphincter tone decrease and horizontal position of the body in bed. As a result, in patients with a combination of bronchial asthma and gastroesophageal reflux disease, night symptoms often prevail. Thus, according to E. G. Tikhomirova (2006), seizure coughing and episodes of difficulty in breathing during sleep are found in 87% of these patients, and the prescription of antisecretory drugs increases the efficacy of treatment and improves control over bronchial asthma. Our experience also shows that in the absence of an adequate response to asthma therapy among the first possible reasons that can explain the ineffectiveness of the treatment should be borne in mind the possibility of gastroesophageal reflux. Moreover, it is not uncommon for the disease to be asymptomatic, even at the stage of severe reflux esophagitis, or to manifest itself only in coughing, which in this case is easy to take for granted as an asthma symptom.
Despite this, the term “reflux–induced asthma“, which is periodically found in the Russian literature, does not seem to us to be quite correct, as it is not about the primary pathogenetic mechanisms of asthma, but about the concomitant pathological process that aggravates the course of the main disease.