Effect of salbutamol on respiratory muscle function and ventilation in awake canines

• Published in: Respiratory physiology & neurobiology Vol. 161; no. 3; pp. 253 - 260
• Main Authors: Easton, P.A, Katagiri, M, Johnson, M.W, Rothwell, B.C, Holroyde, M.C, Kusuhara, N
• Format: Journal Article
• Language: English
• Published: Amsterdarm Elsevier B.V 31.05.2008; Elsevier
• Subjects: Albuterol - pharmacology; Animals; Biological and medical sciences; Bronchodilator Agents - pharmacology; Costal diaphragm; Dogs; Dose-Response Relationship, Drug; Electromyogram; Electromyography; Fundamental and applied biological sciences. Psychology; Hypercapnia - physiopathology; Medical Education; Parasternal intercostal; Pulmonary/Respiratory; Respiratory Muscles - drug effects; Respiratory Physiological Phenomena - drug effects; Salbutamol; Sonomicrometer; Tidal Volume - drug effects; Tidal Volume - physiology; Transversus abdominis; Ventilation; Vertebrates: respiratory system; Wakefulness; β-Agonist; Sonomicrometer; Transversus abdominis; β-Agonist; Electromyogram; Ventilation; Salbutamol; Costal diaphragm; Parasternal intercostal; Fissipedia; Carnivora; Agonist; Electrophysiology; β2-Adrenergic receptor; β-Adrenergic receptor agonist; Respiratory system; Vertebrata; Mammalia; Respiratory muscle; Electromyography; Diaphragm; Pulmonary ventilation; Respiration; Dog
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2008.02.012

Abstract The effect of the β-agonist bronchodilator salbutamol on respiratory muscles and ventilation is uncertain. The presence of β2 receptors on skeletal muscles and increased diaphragm contractility in vitro with salbutamol predict a significant effect that has not been confirmed, in vivo in non-fatigued diaphragm or in clinical studies using standard bronchodilator dosages. Therefore, we infused salbutamol at a higher dosage (23.3 μg/min) used clinically for treatment of respiratory emergencies, while measuring directly the length, shortening and EMG activation of costal and crural diaphragm, parasternal intercostal and transversus abdominis muscles, in 10 awake canines. At this salbutamol dosage, ventilation and tidal volume increased significantly during both resting and CO2 -stimulated breathing. Salbutamol elicited significant increases in respiratory muscle shortening with much smaller increases in EMG activity, so the proportionally greater muscle shortening per unit EMG showed increased muscle contractility. The effects of salbutamol were not extinguished by inspiratory flow resistance or fluid challenge but were reversed specifically by the β-blocker, propranolol. This study demonstrates that, in sufficient intravenous dosage, the β-agonist salbutamol elicits increased ventilation and a β2 receptor-mediated increase in contractility of respiratory muscles.