Airway responses to histamine aerosol in clinically normal foods.

This research article investigates the range of nonspecific airway reactions in clinically normal foals through exposure to aerosol histamine, highlighting the variability in reactions which could influence how foals respond to infections, inflammation, and environmental irritants.

Study Design and Methodology

• The study involved 12 clinically normal mixed-breed foals that were 48 to 92 days old and had no history of clinical lung disease.
• The nonspecific airway reactivity was determined by the researchers by observing the changes in dynamic compliance when the foals were exposed to increasing concentrations of histamine aerosol.
• The level of airway reactivity was quantitatively expressed as the dose of aerosol histamine that caused a 35% decrease in dynamic compliance or a 35% increase in pulmonary resistance.

Results of the Study

• The researchers found that it was possible to induce a decline in Cdyn in all the foals, to less or equal to 65% of the baseline, depending on the histamine dose.
• The foals’ pulmonary resistance reaction was less predictable; in one foal there was a decrease in R(L), rather than an increase, after being exposed to histamine.
• The average dose of histamine that induced a decrease in Cdyn to 65% of the baseline (PC65Cdyn) was 5.43mg/ml, while the dose that evoked an increase in pulmonary resistance to 135% of baseline (PC135R(L)) was 3.34mg/ml.
• There was no correlation found between the body weight of the foals and baseline Cdyn, R(L), PC65Cdyn, or PC135R(L).

Conclusions of the Study

• The study concluded that there was a wide range of airway reactivity amongst clinically normal foals.
• This variation might be a contributing factor to the differences in how foals clinically respond to similar stimuli such as infections, inflammation, and environmental irritants.