Assessment of airway inflammation with exhaled NO measurement

Abstract

Assessing airway inflammation is important for investigating the underlying mechanisms of many lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, primary ciliary dyskinesia (PCD) and cystic fibrosis. A growing interest has recently directed toward non-invasive methods for the assessment of airway inflammation. Measurement of exhaled nitric oxide in exhaled air is an exciting innovative technique that gives new insights into the pathophysiology of lung disease and asthma in particular, with many potential clinical applications. Careful standardisation of measurement techniques has facilitated the use of this new measurement in paediatric respiratory medicine. Non-invasiveness and instantaneous results potentially make it a suitable instrument for use in children starting from the age of 4, with useful applications both in asthma diagnosis and monitoring.

Keywords: airway inflammation; asthma; cystic fibrosis; exhaled nitric oxide; non-invasive monitoring; primary ciliary dyskinesia.

Figure 1.. Synthesis of nitric oxide (NO) and NO-related products (panel A). Sources of NO in exhaled air (panel B). (Revised from Reference 63).

Figure 2.. a) Flow (airflow), b) fractional exhaled nitric oxide, and c) pressure (airway pressure) tracings for a 6-yr-old female using the single-breath on-line method at a flow rate of 50 mL/sec. The exhalation lasted 7sec, a good plateau can be identified and the expiratory pressure is maintained at 11 cmH2O during the manoeuvre. (NO: nitric oxide; ppb: parts per billion). (From Reference 55).

Figure 3.. Scatter gram of exhaled NO in normal and in asthmatic children. eNO was significantly higher in asthmatic (24.3±14.8 ppb) than in healthy children (9.9 ±3.4 ppb); p<0.0001. (From Reference 62).

Figure 4.. Exhaled and nasal NO in primary ciliary dyskinesia (PCD) and cystic fibrosis (CF). (From Reference 130 and 135).