THE EFFECT OF INHALING A DRY POWDER OF SODIUM-CHLORIDE ON THE AIRWAYSOF ASTHMATIC SUBJECTS

Wet aerosols of 4.5% sodium chloride (NaCl) are often used to assess t he bronchial responsiveness associated with asthma, We questioned whet her dry NaCl could be used as an alternative, Dry powder NaCl was inha led from capsules containing either 5, 10, 20 or 40 mg to a cumulative dose of 635 mg, The powder was delivered via an Inhalator(TM) or Hale rmatic(TM). The airway sensitivity to the dry and wet NaCl was compare d in 24 patients with asthma aged 19-39 yrs, All subjects responded to both preparations and the geometric mean (95% confidence intervals) f or the provocative dose of NaCl causing forced expiratory volume in on e second (FEV1) to fall 20% from baseline (PD20,NaCl) for dry NaCl was 103 mg (68-157) versus 172 mg (102-292), p<0.03 for the wet NaCl. The response to dry NaCl was reproducible and on repeat challenge the PD2 0 was 108 mg (75-153). The mean maximum fall in FEV1 was approximately 25% on each of the two test days, Spontaneous recovery occurred withi n 60 min after challenge with dry NaCl and within 5 min after bronchod ilator. There were no serious side-effects requiring medical attention , however some patients coughed on inhalation of the 40 mg dose and th ree gagged, Arterial oxygen saturation remained within normal limits, We conclude that a suitably prepared dry powder of sodium chloride cou ld potentially replace wet sodium chloride to assess bronchial respons iveness in patients with asthma, but further studies are required to e stablish the long-term stability of the dry powder preparation.