Asthma See Also Chapter

Nocturnal worsening of asthma symptoms has been an acknowledged feature of asthma since the fifth century a.d. when Aurelianus Caelius (10) described an increased nocturnal frequency of asthma attacks. Turner Warwick (11) observed that up to 64% of asthmatic patients were awakened with symptoms of asthma at least three nights per week. In a more recent questionnaire-based study, Bellia et al. (12) assessed the frequency of nocturnal asthma symptoms in 1100 patients randomly selected from general medical practices. Up to 24% of patients with the diagnosis of asthma experienced troublesome nocturnal symptoms "sometimes," while 15% of patients experienced such symptoms "often." Peak expiratory flow rate (PEFR) measurements are widely used to diagnose nocturnal worsening of asthma, which is typically indicated by at least a 15% decrement in PEFR from bedtime to morning awakening.

The etiology of the nocturnal worsening of asthma is controversial, and is likely multifactorial. Potential mechanisms include circadian changes in parasym-pathetic activity and circulating levels of corticosteroids and catecholamines. An early morning increase in airway inflammation associated with increased airflow obstruction and bronchial responsiveness has been reported by some investigators (13), although others have been unable to duplicate this finding (14).

There is evidence that sleep itself plays a role in this pattern of nocturnal worsening. Clark and Hetzel (15) studied asthmatic shift workers, observing that virtually all subjects immediately shifted their daily rhythm of PEFR in conjunction with changing their work shifts. These same investigators subsequently observed that sleep disruption had little effect on overnight worsening of PEFR, although total sleep deprivation eliminated overnight decrements in PEFR in about 50% of all asthmatic patients (16). Catterall et al. (17) evaluated the effect of complete overnight sleep deprivation in 12 asthmatic patients with regular nocturnal worsening. PEFR fell significantly overnight, regardless of whether patients were kept awake or allowed to sleep during the night. However, both absolute and percent overnight decreases in PEFR were greater when patients were allowed to sleep.

Nocturnal worsening of asthma is also apparently linked to snoring and sleep-disordered breathing. Chan et al. (18) evaluated nine patients with asthma and concurrent OSA, noting that all patients had frequent nocturnal exacerbations of their asthma. After initiating effective CPAP therapy, all patients demonstrated marked improvement in their asthma, with decreased symptoms, improved PEFR, reduced need for bronchodilator therapy, and resolution of their nocturnal worsening (Fig. 1). Guilleminault et al. (19) subsequently reported two separate populations of asthmatics, one group of middle-aged males with confirmed OSA, and a second group of younger males with recurrent snoring. Nocturnal worsening of asthma resolved in both groups after initiating CPAP therapy. Yigla et al. (20) studied 22 consecutive patients with severe, unstable asthma. Subsequent polysomno-graphy detected OSA in 21 (95.5%) of these patients, although the patient group had a normal mean body mass index. These studies suggest strong relationships between snoring and/or sleep-disordered breathing and overall asthma severity

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Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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