The nebulizer was driven at a flow rate of 7 17min, which nebulized 5 ml of a 0.9 percent saline solution over 2 min. The FEV, was then measured again 30 and 90 s after the end of this control nebulization. If the FEV! remained within 20 percent of the initial value, the patient then inhaled concentrations of either histamine or methacholine over a 2-min period, the dose of both drugs then being doubled every 5 min until a 20 percent fall in FEV, occurred. The dose of either histamine or methacholine that induced a fall of 20 percent in FEV, (the PC,) was then obtained by interpolation. Thereafter, the patient took 2 puffs (200 p.g) of salbutamol, (albuterol) from a metered-dose inhaler, and FEV, was measured 15 min later. canadian pharmacy
Breathing patterns were measured in the seated patients by a respiratory inductive plethysmograph (Respitrace: 15). One band was taped securely around the ribcage at the 2nd to 4th intercostal space anteriorly and the other around the abdomen at the level of the umbilicus. The relative gains of the chest and abdominal bands were arbitrarily fixed to be unity, and the sum of these two signals was then calibrated as the patient gently inflated a 600-ml bag. There was a 4-min adaptation period after calibration, and then breathing patterns were recorded for 4 min before the first bronchial challenge, then from 1 Vi to 5Vi min following the inhalation of the dose of histamine that produced a 20 percent or greater fall in FEV.
Breathing patterns were again recorded over 15 to 19 min after the inhalation of salbutamol (albuterol). All periods of recording the breathing patterns excluded occasions when the FEV, was being measured and 20 s thereafter. The Sa02 was recorded throughout by the Hewlett-Packard 47201A ear oximeter.
This Respitrace calibration could be influenced by changes in FRC or by changes in the relative contributions of the chest and abdominal movement.