Asthma and suggestion: psychological or physical?

Area of Science:

• Respiratory Medicine
• Pulmonary Physiology

Background:

• Previous research suggested psychological suggestion could induce bronchoconstriction.
• The role of suggestion versus physiological factors in airway responses required further investigation.

Purpose of the Study:

• To investigate the effect of suggestion on airway responses to saline and isoprenaline in normal and asthmatic subjects.
• To determine the underlying cause of bronchoconstriction observed after saline inhalation.

Main Methods:

• 12 healthy and 30 asthmatic subjects inhaled normal saline and isoprenaline.
• Subjects received suggestions about the solutions' effects (bronchoconstrictor/bronchodilator).
• Airway response was measured by specific airway conductance (sGaw).

Main Results:

• Nine asthmatic subjects showed bronchoconstriction after saline, with a 40% fall in sGaw.
• This response was dose-dependent.
• Bronchoconstriction was abolished when inhalations were performed at 37°C and 100% relative humidity.
• Suggestion did not influence saline or isoprenaline responses in either group.

Conclusions:

• Airway cooling, not suggestion, causes bronchoconstriction following saline inhalation in asthmatics.
• Environmental conditions (temperature, humidity) play a critical role in airway reactivity.
• The findings challenge previous attributions of bronchoconstriction to psychological suggestion.