The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Results
The sGaw values tended to return to the baseline within 30 min. However, the bronchocon-striction tended to remain during a longer time period in the three patients who had subnormal baseline values lie, <1.3 [sxkPa]); their mean value of sGaw remained at 27 ±9 percent of baseline (mean±SD), while in those who had normal baseline sGaw, the decrements reversed to reach 90 ± 41 percent of their baseline values within 30 min after the challenge. The perfusion distributions, as assessed by log SDQ, broadened immediately after the challenge (Table 1, p<0.01), and the maximal broadening was recorded 30 min after the inhalation of methacholine in most patients. The abnormality in log SDQ then typically remained throughout the experiment, and log SDQ was significantly elevated relative to the baseline (p<0.05) still at the end of the experiment, 2 h after the challenge. The ventilation distributions tended to increase during the experiment, but the changes relative to baseline did not reach statistical significance. After the challenge, bimodal distributions of the perfusion were recorded in all eight patients, and the bimodality remained until the end of the experiment, 2 h after the challenge. The postchallenge decline in arterial P02 reached nadir immediately after the challenge and reversed to the prechallenge range in the last measurement (Table 1). There were no significant postchallenge changes in arterial PCO2.
Peripheral Airway Deposition of Methacholine: Matched doses of methacholine were inhaled on the two separate experimental days, as indicated by the similarity (p>0.05) and the correlation between the count rate recorded by the gamma camera over the chest immediately after the two separate bronchial challenges (r=0.91, p<0.005). An immediate and marked response to the peripheral airway deposition of methacholine was indicated by a significant decline in sGaw of 0.68 ±0.31 (skPa) (p<0.02), which on an average corresponded to 53 percent of the baseline value. The magnitude of the response was, however, significantly less pronounced after the peripheral than after the central airway deposition of nebulized methacholine (p=0.02, Fig 2). canadian health care mall
Figure 2. Mean (SEM) of sGaw (a) and log SDQ (b) (see text for explanations) obtained before, immediately after, 30 min, and 120 min after a bronchoprovocation with aerosolized methacholine in either trachea and the main bronchi (squares) or the peripheral airways (circles). Significant differences in values obtained after the two separate deposition patterns are indicated (asterisk; p=0.02, Wilcox-ons matched paired test). Note that the scaling of the horizontal axis is discontinuous.