Upper airway response during bronchoprovocation and asthma attack.

We measured laryngeal resistance (Rla), upper airway resistance (Ruaw), and lower respiratory resistance below the larynx (Rlrs) during methacholine and histamine provocation in 10 normal and 12 asthmatic subjects. In another 10 asthmatic subjects, Rla was measured during medication for spontaneous asthma attack. The Rla was measured with the low-frequency sound method (see reference 9). Direct measurements of Ruaw and Rlrs were obtained using the 3-Hz forced oscillation technique with a needle inserted below the cricoid cartilage. In normal subjects, Ruaw increased in proportion to the increase in Rlrs during methacholine and histamine provocation. In asthmatic subjects, control Ruaw was higher than the control Ruaw in normal subjects (p less than 0.001) and Ruaw did not change despite an increase in Rlrs during methacholine and histamine provocation. After medication for spontaneous asthma attack, Rla decreased in proportion to the decrease in total respiratory resistance (Rrs). We conclude that in asthmatic subjects, Rla contributes to an increase in Rrs during both the nonspasmodic period and the spontaneous asthma attack but does not do so during bronchoprovocation, probably because the larynx is less sensitive than the lower respiratory tract.