Expiratory Muscle Recruitment Research Articles

The increased expiratory muscle use in upright dogs: role of cardiovascular receptors

A change from the supine to upright posture in anesthetized dogs promoted increased expiratory muscle use during breathing. To examine the role of cardiovascular receptors in eliciting this expiratory muscle recruitment, the electromyographic (EMG) activity of the triangularis sterni (TS) and abdominal external oblique (EO) muscles was recorded in seven spontaneously breathing animals during head up tilting and during occlusion of the inferior vena cava. Head up tilting was associated with a reduction in cardiac output, a transient fall in systematic blood pressure, and considerable increases in TS and EO expiratory EMG activity. On an average (mean ± SE), the amount of TS and EO expiratory activity in the supine posture was 44.7 ± 12.9 and 10.3 ± 7.3%, respectively, of the activity recorded in the 80° head up posture. When occlusion of the inferior vena cava in the supine animals induced a reduction in cardiac output and a fall in systemic blood pressure that were comparable to those measured during head up tilting, the TS and EO expiratory EMG activity also increased. This activity, however, always remained smaller than that recorded during breathing in the upright posture; for the seven animals, the amount of TS and EO expiratory activity during vena cava occlusion was only 58.4 ± 5.7 and 17.9 ± 10.4% of the activity in upright posture, respectively ( P < 0.001 for both muscles). We conclude, therefore, that the reduced venous return and systemic hypotension of the upright posture are not the critical sensory events for promoting the increased expiratory muscle use in this posture. It must, therefore, be elicited by respiratory receptors.

The increased expiratory muscle use in upright dogs: role of cardiovascular receptors

A change from the supine to upright posture in anesthetized dogs promotes increased expiratory muscle use during breathing. To examine the role of cardiovascular receptors in eliciting this expiratory muscle recruitment, the electromyographic (EMG) activity of the triangularis sterni (TS) and abdominal external oblique (EO) muscles was recorded in seven spontaneously breathing animals during head up tilting and during occlusion of the inferior vena cava. Head up tilting was associated with a reduction in cardiac output, a transient fall in systemic blood pressure, and considerable increases in TS and EO expiratory EMG activity. On an average (mean ± SE), the amount of TS and EO expiratory activity in the supine posture was 44.7 ± 12.9 and 10.3 ± 7.3%, respectively, of the activity recorded in the 80° head up posture. When occlusion of the inferior vena cava in the supine animals induced a reduction in cardiac output and a fall in systemic blood pressure that were comparable to those measured during head up tilting, the TS and EO expiratory EMG activity also increased. This activity, however, always remained smaller than that recorded during breathing in the upright posture; for the seven animals, the amount of TS and EO expiratory activity during vena cava occlusion was only 58.4 ± 5.7 and 17.9 ± 10.4% of the activity in upright posture, respectively ( P < 0.001 for both muscles). We conclude, therefore, that the reduced venous return and systemic hypotension of the upright posture are not the critical sensory events for promoting the increased expiratory muscle use in this posture. It must, therefore, be elicited by respiratory receptors.

Differential recruitment of expiratory muscles during opossum development.

Relationships between time-averaged electromyogram (EMG) discharge in abdominal (ABD) and lateralintercostal (IC) muscles (interspaces 1-10) were evaluated when Inactin-anesthetized supine opossums between 20 and 100 days of age were challenged by positive-pressure breathing (PPB) (3, 6, and 8 cmH2O). Expiratory activity upon initiation of PPB was observed in ABD muscles after the 30th postnatal day; recruitment of IC muscles requires further maturation. For example, at a PPB level of 6 cmH2O, animals up to 50-55 days of age recruited IC muscles from the lowest three interspaces on 44% of the occasions where ABD muscles were activated; in older animals the incidence of IC recruitment increased to 87%. Additionally, the occurrence of IC relative to ABD recruitment increased with increasing levels of PPB; IC muscles of highest interspaces (1-3) were activated less often at all pressures. At the onset of PPB, ABD muscles were usually recruited before IC muscles; this effect was more prominent in the younger animals. During the 5th min of PPB, ABD muscles were recruited earlier in expiration than IC muscles in the majority of animals at all ages. Since IC and ABD motor groups are activated from similar levels of the spinal cord, the delayed maturation of IC muscle responses to PPB may reflect developmental processes involving reflexes from the chest or abdomen, and/or may be a function of nonrespiratory utilization (i.e., postural) of ABD and IC muscles.

Effect of five human anesthetics on respiratory control in cats.

The effect of halothane, fentanyl, Innovar, thiopental, and ketamine on inspiratory output, vagal influence, and chest wall reflex was assessed in seven cats lightly anesthetized with pentobarbital, using the method of airway occlusion with and without rapid vagal cooling. All anesthetics depressed inspiratory output, as expressed by deltaP/deltat, of the first occluded inspiration. However, only halothane depressed peak inspiratory output (Pmax). Phasic vagal influence was markedly depressed by 2% halothane but was preserved under other anesthetics. The ability to induce tonic vagal influence (expiratory muscle recruitment) was lost under halothane. Inspiratory inhibitory chest wall reflex was evident in two cats during airway occlusion. Addition of any test anesthetic abolished the reflex. It is concluded that halothane should be avoided in studies dealing with assessment of vagal influence.

Effects of hyperinflation of the thorax on the mechanics of breathing.

ARTICLESEffects of hyperinflation of the thorax on the mechanics of breathingA. E. Grassino, G. E. Lewinsohn, and J. M. TylerA. E. Grassino, G. E. Lewinsohn, and J. M. TylerPublished Online:01 Sep 1973https://doi.org/10.1152/jappl.1973.35.3.336MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByHyperinflation and expiratory muscle recruitment during NREM sleep in humansRespiration Physiology, Vol. 82, No. 1Effect of Helium Concentration on Experimental Upper Airway Obstruction28 June 2016 | Annals of Otology, Rhinology & Laryngology, Vol. 99, No. 7Load compensation during positive pressure breathing in anesthetized manRespiration Physiology, Vol. 65, No. 3Effects of an increase in end-expiratory volume on the pattern of thoracoabdominal movementRespiration Physiology, Vol. 53, No. 3Respiratory mechanics of Pekin ducks under four conditions: Pressure breathing, anesthesia, paralysis or breathing CO2-enriched gasRespiration Physiology, Vol. 47, No. 2Muscle activity during chest wall restriction and positive pressure breathing in manRespiration Physiology, Vol. 35, No. 3The effect of hyperoxia, hypoxia and hypercapnia on FRC and occlusion pressure in human subjectsRespiration Physiology, Vol. 33, No. 2Airway occlusion pressures in awake and anesthetized goatsRespiration Physiology, Vol. 27, No. 1Effect of inspiratory resistance on occlusion pressure in hypoxia and hypercapniaRespiration Physiology, Vol. 24, No. 3Occlusion pressure as a measure of respiratory center output cm conscious manRespiration Physiology, Vol. 23, No. 2 More from this issue > Volume 35Issue 3September 1973Pages 336-342 Copyright & PermissionsCopyright © 1973 the American Physiological Societyhttps://doi.org/10.1152/jappl.1973.35.3.336PubMed4269954History Published online 1 September 1973 Published in print 1 September 1973 Metrics