Histamine phosphate has a cumulative effect when inhaled at five minute intervals

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• Histamine phosphate inhalation causes bronchoconstriction lasting over five minutes.
• Standardized procedures often involve histamine inhalation at five-minute intervals.

Purpose of the Study:

• To investigate the cumulative effect of histamine inhalation at five-minute intervals in adult asthmatic subjects.
• To determine if repeated histamine doses lead to an additive bronchoconstrictor response.

Main Methods:

• Clinically stable adult asthmatic subjects inhaled doubling concentrations of histamine (non-cumulative stage).
• Subjects then inhaled multiple doses of the same histamine concentration at five-minute intervals without recovery (cumulative stage).
• Linear regression analysis assessed cumulative effects on lung resistance and forced expiratory volume in one second.

Main Results:

• Significant positive correlations (p < 0.01) indicated a cumulative effect in most subjects.
• Histamine inhalation at five-minute intervals led to progressively greater bronchoconstriction.

Conclusions:

• Histamine exhibits a cumulative bronchoconstrictor effect when inhaled every five minutes after initial bronchoconstriction.
• This suggests that adequate recovery time is crucial between histamine challenges in asthmatic individuals.