Putting lung function and physiology into perspective: cystic fibrosis in adults

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Abstract

Adult cystic fibrosis (CF) is notable for the wide heterogeneity in severity of disease expression, both between patients and within the lungs of individuals. Although CF airways disease appears to start in the small airways, in adults there is typically widespread bronchiectasis, increased airway secretions, and extensive obstruction and inflammation of the small airways. The complexity and heterogeneity of airways disease in CF means that although there are many different methods of assessing and describing lung ‘function’, none of these single-dimensional tests is able to provide a comprehensive assessment of lung physiology across the spectrum seen in adult CF. The most widely described measure, the forced expiratory volume in 1 s, remains a useful and simple clinical tool, but is insensitive to early changes and may be dissociated from other more detailed assessments of disease severity such as computed tomography. In this review, we also discuss the use of more sensitive novel assessments such as multiple breath washout tests and impulse oscillometry, as well as the role of cardiopulmonary exercise testing. In the future, hyperpolarized gas magnetic resonance imaging techniques that combine regional structural and functional information may help us to better understand these measures, their applications and limitations.

A case report illustrating this review is available inRespirology Case Reports:http://dx.doi.org/10.1002/rcr2.69.

Barry PJ, Horsley AR. Discordance between clinical, physiological and radiological measures in cystic fibrosis. Respirology Case Reports 2014; doi:10.1002/rcr2.69.

Summary:

We report the case of a 20-year-old gentleman with cystic fibrosis who had what appeared to be mild lung disease, with a forced expiratory volume in 1 s of 86% predicted. However, high-resolution computed tomography (CT) revealed extensive bilateral bronchiectasis and severe patchy air trapping. Formal exercise testing showed the patient to have a depressed maximal oxygen consumption (66% predicted) and marked oxygen desaturation from 98% to 79%.

Main teaching points:

• This case highlights that different assessments of respiratory health may be necessary to clinically phenotype patients.

• Spirometry may be insensitive to significant disease which is apparent clinically.

• Other assessments such as CT, lung clearance index or exercise testing may be beneficial in those patients who display clinical discordance from their spirometric findings.

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