CHANGES IN MUCOCILIARY CLEARANCE DURING AND AFTER ISOCAPNIC HYPERVENTILATION IN ASTHMATIC AND HEALTHY-SUBJECTS

Hyperpnoea with dry air could lead to a reduction in depth and hyperos molarity of the periciliary fluid layer (PFL) as a consequence of evap orative water loss, We investigated whether mucociliary clearance (MCC ) is likely to be affected by dry air hyperpnoea, which also results i n airway narrowing in asthmatics, MCC was measured by radioaerosol tec hnique, for about 1 h, in 10 asthmatic and 8 healthy subjects on 3 sep arate days: 1) nasal resting breathing with ambient air; 2) isocapnic hyperventilation (ISH) with dry air; and 3) ISH with warm humid air. A nalysis of the initial and post-intervention lung radioactivity for th e whole right lung and for defined regions of interest showed that, co mpared to ISH with warm humid air and nasal resting breathing, MCC was reduced during and increased post-ISH with dry air in the whole right lung of both groups, The mean reduction in clearance (+/- 95% confide nce interval (95% CI)) was -9.3% (-3.1 to -15.6%) and 3.6% (-2.0 to -9 .1%), and the mean increase (+/-95% CI) was 19.2% (11.8 to 26.6%) and 14.8% (7.1 to 22.5%), compared to warm humid air, in asthmatic and hea lthy subjects, respectively, However, regional analysis showed that th e changes were present in all lung regions of the asthmatics, whilst o nly in the central region of the healthy subjects, The duration of the increased clearance rates post-ISH was also different in both groups. The changes in mucociliary clearance during and after isocapnic hyper ventilation with dry air were probably related to the water content of the inspired air, causing transient changes in the periciliary fluid layer.