Acute metabolic alkalosis (NaHCO3), acidosis (NH4Cl), and placebo (NaCl) we
re induced in 15 healthy volunteers (12 females, median age 34 (range 24-56
) years) in a double blind, placebo controlled study to evaluate the presen
ce of the effects on airway calibre. Acid-base shifts were determined by ca
pillary blood gas sampling. Measurements were performed at the maximal acid
-base shift, 90 min after intervention. Airway resistance (R-aw) and specif
ic airway conductance (sG(aw)), were evaluated, as primary variables, pre a
nd post intervention. Secondary variables, including bronchial responsivene
ss to histamine, maximal respiratory mouth pressures and grip strength, wer
e evaluated post intervention. In alkalosis, base excess (BE) increased fro
m -0.3 (- 3.0-1.9) to 3.0 (1.0-4.8) mmol/l and pH increased from 7.41 (7.37
-7.43) to 7.44 (7.39-7.47) (both P < 0.01), accompanied by an increase in P
a-CO2: 4.7 (4.0-5.7) to 5.0 (4.7-6.1) kPa (P < 0.05). R-aw increased from 0
.156 (0.134-0.263) to 0.169 (0.132-0.271) kPa s/L (P < 0.05), sG(aw) decrea
sed, but this was not statistically significantly. In acidosis, BE decrease
d from -0.2 (-2.0-2.2) to -3.5 ( - 6.3-1.1) mmol/l and pH decreased from 7.
41 (7.39-7.45) to 7.36 (7.31 - 7.40) (both P < 0.01), accompanied by a non-
significant decrease in Pa-CO2. Changes in R-aw and sG(aw) were contrary to
those in alkalosis, but did not reach statistical significance. Acute meta
bolic acid-base shifts mildly influence the airway calibre in healthy human
subjects. (C) 2001 Elsevier Science B.V. All rights reserved.