Forty-seven acutely ill asthmatic patients were entered into this study. Seventeen were men and 30 were women (mean age, 30 years, range 16 to 65 years) and had presented to the emergency room for treatment of asthma. Technically satisfactory values for spirometry, taken within a few minutes of arriving in the emergency room, were obtained in 27 of 47 patients, while satisfactory spirometry postbroncho- dilator therapy was obtained in 26 patients. Peak expiratory flow rate (PEFR) was obtained in 31 of 47 patients. At the time of presentation, the mean initial FEVx (1.43 ± 0.49 L) was 43 ± 16 percent of predicted value, calculated for age, sex and height. Accordingly, these patients may be viewed, as a group, as having had an episode of asthma of moderate severity. Among patients for whom initial spirometry was obtained, there were inverse correlations between respiratory rate and several indices of airflow: FEWl (r = — 0.45, p<0.05), PEFR (r= -0.42, p<0.02) (Fig 1), and flow at 50 percent of vital capacity (V50) (r= —0.45, p<0.05). One hour after initiation of inhalation therapy with nebulized sympathomimetic or anticholinergic drugs or both, respiratory rate had slowed from 26.8 ±6.8 to 20.6 ±4.3 breaths/min (p<0.001), a level that was still higher than in the 42 control subjects (17.8 ±4.3 breaths/min, p<0.01) (Fig 2). However, while flow rates had increased following therapy (FEV1 = 1.43±0.49 vs 2.10±0.70 L, p<0.001), respiratory rate no longer correlated with any of the measures of flow (FEVb PEFR, V^, V*, p>0.3).
Figure 1. Relation between respiratory rate and peak expiratory flow rate on admission to emergency room. Solid line represents least squares linear regression.
Forty-two nonasthmatic patients presenting with noncardiorespiratory complaints were also studied in the same emergency room; 22 were men and 20 were women and their mean age was 39 years (range 11 to 80 years). The initial respiratory rate of the asthmatic patients was significantly higher than that observed in the nonasthmatic patients (26.8 ±6.8 vs 18.3 ±4.6 breaths/min, p<0.001). buy cialis super active
Respiratory rate was not altered by methacholine challenge in asthmatic subjects (16.0±3.7 vs 15.8 ±5.0 breaths/min, p>0.2) or in control subjects (18.0 ±5.1 vs 17.9 ±4.7 breaths/min, p>0.2). Rate was not significantly different between asthmatic and control subjects after methacholine challenge (p>0.2). The mean decrease in FEV, in asthmatics was 33 percent. All asthmatic subjects had a PC20 of less than 8 m^ml, whereas all control subjects had a PC20 exceeding 8 mg/ml of methacholine. In three control subjects, FEVi fell between 22 and 26 percent after inhaling 16 mg/ml of methacholine. In these subjects, respiratory rate changed 1 breath/minute or less between baseline and completion of the challenge. In asthmatic patients but not in control subjects, overall Ve and Vt were increased by methacholine (after last dose: Ve = 11.1±3.5 vs 7.6±2.1 L/min, p<0.05; Vt=0.79 ±0.46 vs 0.46 ±0.16 L, p<0.08) (Fig 3).
FIGURE 2. Respiratory rate on admission and at one-hour after therapy in emergency room for asthmatic and non-asthmatic control subjects. Bars represent ± 1 SEM.
Respiratory rate was not significantly different between asthmatic and control subjects at rest (12.7 ± 4.7 vs 15.1 ±2.7 breaths/min, p>0.2) and following exercise-induced asthma (14.8 ±4.3 vs 17.1 ±3.5 breaths/ min, p>0.2). Following exercise, FEV, fell a mean of 25 percent for asthmatics and 2 percent for control subjects. Following exercise, Ve and Vt were both significantly higher throughout the postexercise period in asthmatics than in normal subjects. When FEVi in asthma patients was at its lowest (15 minutes postexercise, 2.22 ±0.49 L), Ve and Vt were both more than double that of control subjects (Ve = 14.60 vs 7.24 L/min, p<0.01; Vt= 1.07 vs 0.41 L, p<0.01) (Fig 3). canadian discount drugs
FIGURE 3. Respiratory rate, minute ventilation and tidal volume before and after exercise and before and after methacholine inhalation for asthmatic and non-asthmatic control subjects. Bars represent ± I SEM.