Exhaled nitric oxide in an elderly population

The gas nitric oxide (NO) is naturally produced in the human airway, and is involved in a wide variety of pulmonary processes, including vasodilation and the inflammatory response. Exhaled NO (eNO) can be measured in normal subjects, and elevated eNO levels have been shown to occur in asthma and other inflammatory lung conditions. To date there has been no data published examining eNO in an elderly population, yet the test may be particularly relevant to the elderly as it is simple to perform. The aims of this project were to compare eNO values in an elderly population with those of a control population and to evaluate the different reported techniques for measuring eNO. Methods: 68 subjects (30 elderly, 30 control) exhaled either directly into the NO analyser or into bags, the contents of which were subsequently analysed. Exhaled NO was measurable in all subjects. Results: Mean (SD) log eNO in young subjects was 1.43 (0.22) parts per billion, whereas in the elderly it was 1.52 (0.19) pps (p=NS for difference). No correlation was demonstrated between eNO levels and age, or spirometric values. Comparison between direct exhalation, exhalation into a Tedlar bag and into an Impermeable gas bag showed correlations of r=0.87 and r=0.88 respectively. The majority of elderly subjects rated the NO techniques as easier to perform than spirometry, with the bag techniques easier than the direct exhalation into the analyser. Only three subjects were unable to perform the direct techniques. All subjects were able to perform the bag techniques. Conclusions: This study has shown that eNO is readily applicable to the elderly population and may be useful for assessing airway inflammation and thus planning treatment.