Propranolol and inspiratory muscle performance in normal subjects.

We studied the effects of propranolol on respiratory muscle performance during inspiratory threshold-loaded endurance breathing in eight normal subjects. Propranolol (mean daily dose = 160 + 17 mg, SEM) reduced loaded 15-second MVV (92 versus 81 L/min;P = .01) and maximal sustainable ventilatory capacity (52.3 versus 44.5 L/min, P = .02) but did not affect the fraction of MVV, which was sustainable. Maximal static inspiratory pressures were reduced at two of three lung volumes, whereas maximal static expiratory pressures were unaffected by propranolol. The reduction in inspiratory muscle performance in the whole population could be accounted for almost entirely by four subjects who developed symptoms of "tiredness" and easy fatigability while receiving propranolol. There was no significant difference in propranolol dose, in degree of beta-receptor blockade, or in physical fitness in symptomatic and asymptomatic groups, and in neither group did propranolol alter pulmonary function test results. Propranolol directly depresses inspiratory muscle strength in subjects who develop drug-induced symptoms of fatigue by a mechanism probably unrelated to beta-adrenergic-receptor blockade.

The tuberculin test. Studies of the dynamics of reactivity to tuberculin and Candida antigen in institutionalized patients.

To determine the importance of the recall phenomenon ("booster effect") in chronically hospitalized patients, we performed three sequential tuberculin and Candida antigen skin tests in patients at two hospitals. Twenty of 162 patients (12.3%) demonstrated a significant reaction on the initial tuberculin test, and 9 additional patients (5.5%) showed a significant reaction (booster response) to a second tuberculin test administered 3 wk later. Five patients (3.1%) demonstrated a significant reaction only when a third tuberculin test was administered 6 wk after the initial test. Only 1 patient (0.6%) with a significant tuberculin reaction on the first 2 tests was nonreactive on the third test. Nineteen patients (11.7%) demonstrated a significant response to Candida antigen on the initial test and a booster effect was noted in 11 (6.2%) and 6 (3.7%) patients, respectively, on subsequent tests. Four patients (2.5%) appeared to lose reactivity to Candida antigen on each of the 2 repeat tests. Only 25% of patients who demonstrated a tuberculin booster response had a significant reaction to the initial Candida skin test. Serial skin tests may be necessary to reliably determine the ability of a chronically hospitalized patient to demonstrate a response to tuberculin.

Inspiratory muscle training in clinical practice. Physiologic conditioning or habituation to suffocation?

Six healthy volunteers and 19 patients with stable chronic obstructive pulmonary disease underwent a multistage, maximal, ventilatory stress test, ie, serial imposition of increasingly severe resistances to inspiration by means of a commercially available device (Pflex Inspiratory Trainer). Patients consistently underventilated and suffered desaturation during the test; healthy individuals did not. Eight patients completed three weeks or more of daily training stints using the inspiratory resistive device. There was no significant improvement in performance of the test after training. Those individuals whose condition improved showed no discernible change in ventilatory pattern but did suffer further desaturation.