This statistic was originally described in the patent for the device, and has subsequently been described by others. The formula and equipment for assessing and computing V was derived from studies using cross-spectral analysis to determine the proportion of the periodic fluctuations in heart period that occur within the expected respiratory frequencies for an adult human population.
Spirometry testing and the administration of medication were performed by a board-certified pulmonary physician. Doubleblind procedures were used, such that neither the physician nor the patient was told whether active drug or placebo was being administered in any given session.
Subjects were seen on two separate occasions, separated by between 2 days and 1 month. Buy birth control pills online read only The order of placebo/active drug was randomized, using a table of random numbers. Half the subjects were tested with the drug in the first session and half with the placebo. Subjects received the other condition (drug or placebo) in the second session. For each subject, both sessions were held during an afternoon visit at approximately the same time of day in order to minimize the effects of diurnal variation in asthma. Upon subjects’ arrival, resting ECG was recorded for 5 min. During this procedure, subjects were instructed to sit comfortably in a straight back chair, with eyes closed, and to remain still. Following ECG recording, flow volume loops were obtained using standard technique. Three forced expiratory maneuvers were performed using maximal effort. If equivalent flow volume curves were achieved (ie, FEVi + FVC within 5 percent) the curve with the highest FEVi + FVC was chosen for analysis. Subjects were then administered IB or placebo, as described below. If equivalent curves were not obtained, additional maneuvers were done until the subject produced three equivalent curves.
After taking medication, subjects were asked to remain in the waiting room for 30 min. Thereafter, ECG and spirometry tests were repeated exactly as described above.