title: Effect of beta-adrenergic blockade on hyperventilation and exercise tolerance in emphysema.
abstract: Ventilation, heart rate, and arterial blood gas tensions were measured at rest and during incremental exercise in 10 patients with emphysema after intravenous placebo or 7 mg metoprolol. Metoprolol reduced heart rate by 14% (P less than 0.001) and ventilation by 11% (P less than 0.01), but there was no significant difference in arterial O2 or CO2 tension (Pao2 and PaCO2, respectively). Metoprolol increased the time to exhaustion on a cycle ergometer (P less than 0.05) but did not improve the 12-min walking distance. A double-blind randomized crossover comparison of 4 wk treatment with atenolol (100 mg/day), metoprolol (100 mg/day), or matched placebo was performed in 12 patients with emphysema. Both beta-adrenoceptor antagonists reduced resting heart rate by 33% (P less than 0.001) and resting minute ventilation by 11% (P less than 0.025). There was no change in resting or exercise Pao2 or Paco2. During steady-state exercise on a cycle ergometer, atenolol and metoprolol reduced ventilation by 14 and 4%, respectively. This was accompanied by 11 and 5% reductions in O2 consumption (P less than 0.05) and 13 and 6% falls in CO2 production (P less than 0.05). There were no significant changes in tests of exercise tolerance, but forced expiratory volume in 1 s and forced vital capacity were reduced during beta 1-adrenergic blockade. beta 1-Blocking drugs reduce hyperventilation in emphysema by reducing pulmonary gas exchange without a change in arterial blood gas tensions. Increased airflow obstruction prevents this reduction being of therapeutic value.
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D007275:Injections, Intravenous; D008176:Lung Volume Measurements; D008297:Male; D008790:Metoprolol / Q000008:administration & dosage*; D008875:Middle Aged; D010807:Physical Endurance / Q000187:drug effects*; D005082:Physical Exertion; D011412:Propanolamines / Q000008:administration & dosage*; D011656:Pulmonary Emphysema / Q000188:drug therapy / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012119:Respiration / Q000187:drug effects*
chemical_list: D011412:Propanolamines; D008790:Metoprolol