| Popis: |
It was hypothesized that Respiratory heat and moisture loss (RHML) would be altered in patients with Asthma and Chronic obstructive pulmonary disease (COPD) due to the effects of airway inflammation and re-modeling. By designing a novel device incorporating humidity, temperature and flow sensors, RHML was measured in 25 normal controls, 33 asthmatics and 17 patients with COPD. In normal subjects RHML was found to be dependent on breathing pattern as defined by tidal volume and minute ventilation whereas no association was found between RHML and body surface area. At matched breathing patterns asthmatics whether in the exacerbation or stable group showed a small but significantly increased RHML compared to controls (exacerbation group-93.2 (SD=8.0), p=0.0003, stable group - 89.3 (SD=7.4), p=0.025 and controls 85 (SD=4.3) Joules/L). No significant difference was found in RHML between the asthmatics with an exacerbation and those with stable disease. COPD patients showed no significant difference in RHML (stable group-83 (SD=4.8), p=0.23 and exacerbation group-81 (5D=5.8), p=0.06 Joules/L) compared to controls or between exacerbation and stable groups. Evaporative heat loss accounted for the major heat transfer modality (up to 3-times the dry convective heat loss). It can be concluded that asthma is associated with a measurable increase in heat and moisture loss in breath and that this may reflect the inflammatory and vascular changes known to occur in the asthmatic airway. Further studies are required to assess whether the technique developed in this study may provide a practical means to measure inflammation in asthma. |
