Elevated peripheral airway nitric oxide in bronchiectasis reflects disease severity

Abstract

Background: Bronchiectasis is characterised by neutrophilic bronchial inflammation and patients are prone to recurrent or chronic bacterial airway infections. Direct measurement of lung inflammation would be useful in order to assess disease activity and guide need for antibiotic treatment and to monitor response. Current methods of monitoring inflammation are invasive, indirect or insensitive. Exhaled nitric oxide (FE(NO)) is a direct simple non-invasive test of inflammation used in other airway diseases. The aim of this study was to test whether peripheral airway nitric oxide (C(alv)) can provide a clinically useful direct measure of inflammation in the lungs of patients with bronchiectasis.

Methods: Fifty three patients with bronchiectasis were studied when clinically stable and a further 20 patients during an exacerbation of bronchiectasis. FE(NO) was measured by chemiluminescence using a NO analyser. Two models of pulmonary exchange dynamics were used to calculate proximal and peripheral contributions to final FE(NO) concentration.

Results: FE(NO) was elevated in bronchiectasis patients compared to 30 healthy controls (p < 0.05). Compartmental modelling reveals that this elevation is due to an increase in peripheral airway NO (bronchiectasis 3.6 ppb (2.1), controls 2.7 ppb (1.5) p < 0.05) whereas proximal airway NO levels are normal (bronchiectasis 777(751) pl/s, controls 582(579) pl/s ns). C(alv) relates to disease severity measured by lung function and HRCT scan and correlates with the quality of life score. There is no change in FE(NO) parameters at exacerbation and following treatment.

Conclusions: Peripheral airway NO is elevated and reflects disease severity in bronchiectasis but does not provide information to inform acute treatment decisions.