Biomaterial Database

Inspiratory and expiratory muscle function during continuous positive airway pressure in dogs. 1990

J D Road, and A M Leevers

Department of Medicine, University Hospital, University of British Columbia, Vancouver, Canada.

Continuous positive airway pressure (CPAP) is known to produce activation of the expiratory muscles. Several factors may determine whether this activation can assist inspiration. In this study we asked how and to what extent expiratory muscle contraction can assist inspiration during CPAP. Respiratory muscle response to CPAP was studied in eight supine anesthetized dogs. Lung volume and diaphragmatic initial length were defended by recruitment of the expiratory muscles. At the maximum CPAP of 18 cmH2O, diaphragmatic initial lengths were longer than predicted by the passive relationship by 52 and 46% in the costal and crural diaphragmatic segments, respectively. During tidal breathing after cessation of expiratory muscle activity, a component of passive inspiration occurred before the onset of inspiratory diaphragmatic electromyogram (EMG). At CPAP of 18 cmH2O, passive inspiration represented 24% of the tidal volume (VT) and tidal breathing was within the relaxation characteristic. Diaphragmatic EMG decreased at CPAP of 18 cmH2O; however, VT and tidal shortening were unchanged. We identified passive and active components of inspiration. Passive inspiration was limited by the time between the cessation of expiratory activity and the onset of inspiratory activity. We conclude that increased expiratory activity during CPAP defends diaphragmatic initial length, assists inspiration, and preserves VT. Even though breathing appeared to be an expiratory act, there remained a significant component of active inspiratory diaphragmatic shortening, and the major portion of VT was produced during active inspiration.

UI	MeSH Term	Description	Entries
D008176	Lung Volume Measurements	Measurement of the amount of air that the lungs may contain at various points in the respiratory cycle.	Lung Capacities,Lung Volumes,Capacity, Lung,Lung Capacity,Lung Volume,Lung Volume Measurement,Measurement, Lung Volume,Volume, Lung
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D011175	Positive-Pressure Respiration	A method of mechanical ventilation in which pressure is maintained to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange.	Positive End-Expiratory Pressure,Positive-Pressure Ventilation,End-Expiratory Pressure, Positive,End-Expiratory Pressures, Positive,Positive End Expiratory Pressure,Positive End-Expiratory Pressures,Positive Pressure Respiration,Positive Pressure Ventilation,Positive-Pressure Respirations,Positive-Pressure Ventilations,Pressure, Positive End-Expiratory,Pressures, Positive End-Expiratory,Respiration, Positive-Pressure,Respirations, Positive-Pressure,Ventilation, Positive-Pressure,Ventilations, Positive-Pressure
D012132	Respiratory Muscles	These include the muscles of the DIAPHRAGM and the INTERCOSTAL MUSCLES.	Ventilatory Muscles,Respiratory Muscle,Muscle, Respiratory,Muscle, Ventilatory,Muscles, Respiratory,Muscles, Ventilatory,Ventilatory Muscle
D003964	Diaphragm	The musculofibrous partition that separates the THORACIC CAVITY from the ABDOMINAL CAVITY. Contraction of the diaphragm increases the volume of the thoracic cavity aiding INHALATION.	Respiratory Diaphragm,Diaphragm, Respiratory,Diaphragms,Diaphragms, Respiratory,Respiratory Diaphragms
D004285	Dogs	The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)	Canis familiaris,Dog
D004576	Electromyography	Recording of the changes in electric potential of muscle by means of surface or needle electrodes.	Electromyogram,Surface Electromyography,Electromyograms,Electromyographies,Electromyographies, Surface,Electromyography, Surface,Surface Electromyographies
D000009	Abdominal Muscles	Muscles forming the ABDOMINAL WALL including RECTUS ABDOMINIS; ABDOMINAL OBLIQUE MUSCLES, transversus abdominis, pyramidalis muscles and quadratus abdominis.	Cremaster Muscle,Pyramidalis Muscle,Quadratus Abdominis,Transverse Abdominal,Transversus Abdominis,Abdominal Muscle,Abdominal, Transverse,Abdominals, Transverse,Abdomini, Quadratus,Abdominis, Quadratus,Cremaster Muscles,Muscle, Abdominal,Muscle, Cremaster,Muscle, Pyramidalis,Muscles, Abdominal,Muscles, Cremaster,Muscles, Pyramidalis,Pyramidalis Muscles,Quadratus Abdomini,Transverse Abdominals
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013990	Tidal Volume	The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are TV or V with subscript T.	Tidal Volumes,Volume, Tidal,Volumes, Tidal