title: Acidity potentiates bronchoconstriction induced by hypoosmolar aerosols.
abstract: Naturally occurring fogs are usually hypoosmolar with respect to body fluids and can be quite acidic. Because both hypoosmolarity and acidity can cause bronchoconstriction, we studied whether there was a positive interaction between these stimuli in 12 subjects with asthma. We administered the following aerosols: hypoosmolar saline (30 mOsm) at pH 5.5, 3 hypoosmolar acids (0.005 M H2SO4, 0.01 M HNO3 and a 1:1 mixture of 0.005 M H2SO4 and 0.01 M HNO3, all 30 mOsm) at pH 2, and isoosmolar 0.005 M H2SO4 (300 mOsm) at pH 2. Each aerosol was administered on a separate day and was inhaled through a mouthpiece during tidal breathing. Specific airway resistance (SRaw) was measured before and after the subjects inhaled aerosols delivered at as much as 5 doubling nebulizer outputs. For each aerosol challenge, an output-response curve was generated, and the nebulizer output required to increase SRaw by 100% above baseline (PO100) was calculated. Mean values of PO100 were significantly lower for each of the hypoosmolar acids than for hypoosmolar saline (1.65 + 0.43 g/min [mean + SEM] for saline compared with 0.95 + 0.11, 1.05 + 0.20, and 0.90 + 0.14 for H2SO4, HNO3, and a 1:1 mixture of the two; all p values less than 0.025). Mean values of PO100 did not differ among the 3 acids studied. For 7 of 12 subjects, all 3 acids caused a leftward shift in the output-response curve from the curve generated for hypoosmolar saline aerosol. Isoosmolar H2SO4 did not increase SRaw by 100% in any subjects, even at the maximal nebulizer output that delivered a concentration of H2SO4 in excess of 40 mg/m3.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Northern California Occupational Health Center, San Francisco.
authors.forename: J R
authors.initials: JR
authors.lastname: Balmes
authors.forename: J M
authors.initials: JM
authors.lastname: Fine
authors.forename: D
authors.initials: D
authors.lastname: Christian
authors.forename: T
authors.initials: T
authors.lastname: Gordon
authors.forename: D
authors.initials: D
authors.lastname: Sheppard
mesh_terms: D000328:Adult; D000336:Aerosols; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology*; D001980:Bronchi / Q000187:drug effects* / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D004338:Drug Combinations; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D009566:Nitrates / Q000494:pharmacology*; D017942:Nitric Acid; D009994:Osmolar Concentration; D012965:Sodium Chloride / Q000494:pharmacology; D013464:Sulfuric Acids / Q000494:pharmacology*; D014887:Weather
chemical_list: D000336:Aerosols; D004338:Drug Combinations; D009566:Nitrates; D013464:Sulfuric Acids; D017942:Nitric Acid; D012965:Sodium Chloride; C033158:sulfuric acid