cough

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Coug h Anne B. Chang, MBBS, MPHTM, FRACP, PhD KEYWORDS Cough Evidence-based medicine Children Systematic review Clinical evaluation Protocol

The prevalence of chronic cough (5%–10%)1,2 is likely dependent on the setting, age of the cohort studied, instrument used, and definition of chronic cough.3 Cough as a symptom is almost ubiquitous for the entire respiratory system, ranging from uncomplicated minor respiratory tract infections (RTI) to major illnesses, such as cystic fibrosis. Rarely, it may be a symptom of extrapulmonary disease, such as cardiac abnormalities. Most acute cough in children is related to RTIs. Not surprisingly, cough is often trivialized. Cough, however, especially when chronic, significantly impacts on parents’ quality-of-life scores.4,5 THE BURDEN AND BRIEF PATHOPHYSIOLOGY OF COUGH

The burden of cough is also reflected in the billions of dollars spent annually on overthe-counter (OTC) cough medications,6 and the number of consultations sought for cough. In an Australian study, the number of medical consultations for coughing illness in the last 12 months was high: more than 80% of children had greater than or equal to five doctor visits, and 53% had greater than 10.5 Parents of children with chronic cough did not have symptoms of anxiety or depression but were stressed.5 This is in contrast to adults with chronic cough, which is associated with the presence of depression and anxiety.7,8 Clinicians need to be cognizant of the stress parents have when dealing with children with chronic cough. The reasons for parental fears and concerns included cause of the cough, fear of choking, and long-term respiratory damage.1,5,9 Physiologically, cough has three phases: (1) inspiratory, (2) compressive, and (3) expiratory.10 The inspiratory phase consists of inhaling a variable amount of air, which serves to lengthen the expiratory muscles, optimizing the length-tension relationship. The compressive phase consists of a very brief (200 millisecond) closure of the glottis to maintain lung volume as intrathoracic pressure builds (up to 300 mm Hg in adults) because of isometric contraction of the expiratory muscles against a closed glottis. The expiratory phase starts with opening of the glottis, releasing a brief (30–50

A.B. Chang is funded by the Royal Children’s Hospital Foundation and the National Health and Medical Research Council, Australia. Menzies School of Health Research, Charles Darwin University, Queensland Children’s Respiratory Centre, Royal Children’s Hospital, Herston Road, Brisbane, Queensland 4029, Australia E-mail address: annechang@ausdoctors.net Pediatr Clin N Am 56 (2009) 19–31 doi:10.1016/j.pcl.2008.10.002 pediatric.theclinics.com 0031-3955/08/$ – see front matter ª 2009 Elsevier Inc. All rights reserved.


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