Hypocapnia and Airway Resistance in Normal Humans
Airway constriction causes an increase in airflow resistance and a breathing limitation. This constriction may be mediated by airway sensitivities to airborne allergens (Widdicombe 1983), cooling (Julia-Serda, Molfino, Califaretti, Hoffstein and Zamel 1996; Fontanari, Burnet, Zattara-Hartmann and Jammes 1996) or drying (Fontanari et al. 1996). Additionally, variations in carbon dioxide tension (PCO2) have been implicated as a factor affecting airway tone, with both hypercapnia (Sterling 1969; Tashkin and Simmons 1972) and hypocapnia (Newhouse, Becklake, Macklem and McGregor 1964; Sterling 1968) causing an increase in airway resistance. However, in most experiments both of these conditions are accompanied by hyperventilation, which may itself result in airway drying and or cooling. To date, conclusive evidence of the specific role of CO2 tension on airway tone has yet to be produced.
Keywordshypocapnia hyperventilation airway resistance asthma
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