Hyperinflation due to Tonic Activity in Inspiratory Muscles

In anesthetized rabbits, direct and integrated phrenic neurogram (Ephr) and electromyograms from the diaphragm (Edi) and intercostal (Eic) (2nd space) and transversus abdominis muscles (Etr) were simultaneously recorded in two protocols. 1) In animals breathing spontaneously, we used infinite inspiratory (RI) or expiratory (RE) resistive load and intravenous injections of carbachol, histamine, or phenyl diguanide (PDG). All circumstances except RE evoked tonic activities in Ephr, Edi, and Eic but never in Etr. Intravenous atropine abolished carbachol-induced bronchoconstriction and associated tonic inspiratory activities, but this effect persisted with RI, histamine, and PDG. Selective procaine block of conduction in thin vagal fibers (with persistence of the Breuer-Hering inflation reflex) reduced or suppressed the tonic response, which was abolished in all cases after vagotomy. 2) In rabbits artificially ventilated with open chest, passive deflation of the lung or intravenous injections of histamine or PDG also produced tonic discharge in Ephr and often in Eic. The present results demonstrate that 1) stimulation of vagal afferents and mostly thin sensory fibers elicits tonic inspiratory discharges, 2) bronchoconstriction is not necessary for the induction of the response, and 3) reflexes from the chest wall do not mediate this response in rabbits.

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Decay of inspiratory muscle activity in chronic airway obstruction

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.6.1388 ◽

1981 ◽

Vol 51 (6) ◽

pp. 1388-1397 ◽

Cited By ~ 21

Author(s):

G. Citterio ◽

E. Agostoni ◽

A. Del Santo ◽

L. Marazzini

Keyword(s):

Airway Obstruction ◽

Time Course ◽

Normal Subjects ◽

Inspiratory Muscle ◽

Resistive Load ◽

Tonic Activity ◽

Persistence Time ◽

Elastic Load ◽

Inspiratory Muscles ◽

Chronic Airway

Relative decay rate of inspiratory muscle electrical activity (RDRI) in patients with chronic airway obstruction increased with decreasing expiratory time (TE), being faster than in normal subjects for a given TE. Time course of decay was similar in shape to that of normal subjects, whereas persistence time of activity during expiration was about half. Hence, braking action of inspiratory muscles in patients was smaller than in normal subjects. No tonic activity of inspiratory muscles was found in patients, even when frequency was increased and hyperinflation enhanced. Hence tonic activity of inspiratory muscles found by others in asymptomatic asthmatic or normal subjects after histamine inhalation seems elicited by histamine. In normal subjects breathing under resistive load, RDRI became similar to that of patients for a given TE: tonic activity of extradiaphragmatic inspiratory muscles occurred only if frequency was voluntarily increased at least three times, an unphysiological condition with resistive load. Under discontinuous inspiratory elastic load, RDRI of patients decreased or did not change, whereas previously that of normal subjects was found to increase.

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Tonic inspiratory muscle activity as a cause of hyperinflation in asthma

Journal of Applied Physiology ◽

10.1152/jappl.1981.50.2.279 ◽

1981 ◽

Vol 50 (2) ◽

pp. 279-282 ◽

Cited By ~ 36

Author(s):

N. Muller ◽

A. C. Bryan ◽

N. Zamel

Keyword(s):

Muscle Activity ◽

Inspiratory Muscle ◽

Tonic Activity ◽

Surface Electrodes ◽

Inspiratory Muscles ◽

Thoracic Gas Volume ◽

Before And After ◽

Male Patients ◽

Gas Volume ◽

Proportional Reduction

We studied tonic activity of the inspiratory muscles during exacerbation of asthma in five female and two male patients. Exacerbation was provoked by withholding bronchodilatory medication for 12 h prior to the study. Thoracic gas volume (TGV) at the end of resting expiration was determined before and after albuterol (salbutamol) inhalation with a body plethysmograph. Intercostal muscle electromyogram (EMG) was recorded with surface electrodes and diaphragmatic EMG with esophageal electrodes. Tonic activity was defined as electrical activity in the EMG present throughout expiration. After salbutamol the TGV decreased 13.4 +/- 2.9% (mean +/- SE) (P less than 0.01). This decrease in TGV was accompanied by a proportional reduction in tonic intercostal (r = 0.78, P less than 0.05) and diaphragmatic activity (r = 0.84, P less than 0.05). These findings suggest that the hyperinflation present during exacerbation of asthma is at least in part due to active inspiratory muscle activity present throughout expiration.

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Viral bronchiolitis and the detrimental effects of sleep

Dalhousie Medical Journal ◽

10.15273/dmj.vol46no2.10141 ◽

2020 ◽

Vol 46 (2) ◽

Author(s):

Daniel Hughes

Keyword(s):

Pulse Oximetry ◽

Eye Movement ◽

Supplemental Oxygen ◽

Oxygen Desaturation ◽

Rapid Eye Movement ◽

Tonic Activity ◽

Rapid Eye Movement Sleep ◽

Inspiratory Muscles

Infants recovering from bronchiolitis and no longer requiring supplemental oxygen will have brief episodes of oxygen desaturation during sleep when monitored with pulse oximetry. These episodes can be explained by the inhibition of the tonic activity of the inspiratory muscles during rapid eye movement sleep. Pulse oximetry monitoring should be discontinued, and these infants considered for discharge.

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Activity of respiratory muscles in upright and recumbent humans

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.6.1552 ◽

1981 ◽

Vol 51 (6) ◽

pp. 1552-1561 ◽

Cited By ~ 115

Author(s):

W. S. Druz ◽

J. T. Sharp

Keyword(s):

Respiratory Muscles ◽

Pressure Change ◽

Normal Subjects ◽

Oblique Muscle ◽

Upright Posture ◽

Tonic Activity ◽

Rib Cage ◽

Inspiratory Muscles ◽

Supine Posture ◽

Gastric Pressure

It is established that during tidal breathing the rib cage expands more than the abdomen in the upright posture, whereas the reverse is usually true in the supine posture. To explore the reasons for this, we studied nine normal subjects in the supine, standing, and sitting postures, measuring thoracoabdominal movement with magnetometers and respiratory muscle activity via integrated electromyograms. In eight of the subjects, gastric and esophageal pressures and diaphragmatic electromyograms via esophageal electrodes were also measured. In the upright postures, there was generally more phasic and tonic activity in the scalene, sternocleidomastoid, and parasternal intercostal muscles. The diaphragm showed more phasic (but not more tonic) activity in the upright postures, and the abdominal oblique muscle showed more tonic (but not phasic) activity in the standing posture. Relative to the esophageal pressure change with inspiration, the inspiratory gastric pressure change was greater in the upright than in the supine posture. We conclude that the increased rib cage motion characteristic of the upright posture owes to a combination of increased activation of rib cage inspiratory muscles plus greater activation of the diaphragm that, together with a stiffened abdomen, acts to move the rib cage more effectively.

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Tonic inspiratory muscle activity as a cause of hyperinflation in histamine-induced asthma

Journal of Applied Physiology ◽

10.1152/jappl.1980.49.5.869 ◽

1980 ◽

Vol 49 (5) ◽

pp. 869-874 ◽

Cited By ~ 49

Author(s):

N. Muller ◽

A. C. Bryan ◽

N. Zamel

Keyword(s):

Lung Volume ◽

Muscle Activity ◽

Normal Subjects ◽

Inspiratory Muscle ◽

Intercostal Muscle ◽

Tonic Activity ◽

Surface Electrodes ◽

Inspiratory Muscles ◽

Thoracic Gas Volume ◽

Gas Volume

We studied the change in tonic activity of the inspiratory muscles during acute hyperinflation. Hyperinflation was provoked in two asthmatic and three normal subjects by progressively doubling doses of histamine. Changes in lung volume were determined with magnetometers and with a body plethysmograph. Intercostal muscle activity was recorded with surface electrodes and diaphragmatic activity with esophageal electrodes. Tonic activity was defined as electrical activity in the electromyogram present at end expiration. After histamine the maximal observed increase in plethysmographic thoracic gas volume in the five subjects was 29.8 +/- 6.4% of control (mean +/- SE). Hyperinflation was accompanied by a significant increase in tonic activity of the intercostal muscles (P < 0.01) and the diaphragm (P < 0.01). There was a significant correlation between the increase in thoracic gas volume and the increase in tonic intercostal (r = 0.82, P = 0.003) and diaphragmatic (r = 0.89, P = 0.003) activity. We conclude that histamine-induced hyperinflation is accompanied by persistent inspiratory muscle activity throughout expiration.

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TONIC ACTIVITY AND GRAVITATIONAL CONTROL OF THE POSTURAL MUSCLE

Aerospace and Environmental Medicine ◽

10.21687/0233-528x-2020-54-6-58-72 ◽

2020 ◽

Vol 54 (6) ◽

pp. 58-72

Author(s):

B.S. Shenkman ◽

◽

T.M. Mirzoev ◽

I.B. Kozlovskaya ◽

◽

...

Keyword(s):

Nervous System ◽

Signal Pathways ◽

Tonic Activity ◽

Postural Muscle ◽

Continuous Work ◽

Tonic System ◽

The Brain ◽

Almost Continuous ◽

Fundamental Conclusion ◽

Sensory Mechanisms

The review is an attempt to describe and give a meaning to the accumulated data about the mechanisms controlling the structure and functionality of the postural muscle the almost continuous work of which makes it possible for the humans and animals to exist actively on Earth's surface. A great bulk of these data was obtained, described and systematized by professor I.B. Kozlovskaya and her pupils. A body of the most interesting facts and regularities was documented in other laboratories and research centers, quite often under the influence of ideas suggested by I.B. Kozlovskaya. The concept of the tonic system, that is, an integral physiological apparatus comprising not only slow and fast muscular fibers and small controlling motoneurons but also a complex of the brain (up to and including the striatum and motor cortex) and sensory mechanisms, constitutes the most important parts of her theoretical legacy. The fundamental conclusion of this review is that the gravity-dependent tonic contracting activity of the postural muscle controlled by the nervous system and afferent mechanisms is key to maintaining its structure, signal pathways and mechanic properties crucial for its constant anti-gravity activity.

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Changes in electromyographic activity, mechanical power, and relaxation rates following inspiratory ribcage muscle fatigue

Scientific Reports ◽

10.1038/s41598-021-92060-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Antonio Sarmento ◽

Guilherme Fregonezi ◽

Maria Lira ◽

Layana Marques ◽

Francesca Pennati ◽

...

Keyword(s):

Muscle Fatigue ◽

Low Frequency ◽

Mechanical Power ◽

Electromyographic Activity ◽

Median Frequency ◽

Relaxation Rates ◽

Shortening Velocity ◽

Inspiratory Muscles ◽

Underlying Mechanisms

AbstractMuscle fatigue is a complex phenomenon enclosing various mechanisms. Despite technological advances, these mechanisms are still not fully understood in vivo. Here, simultaneous measurements of pressure, volume, and ribcage inspiratory muscle activity were performed non-invasively during fatigue (inspiratory threshold valve set at 70% of maximal inspiratory pressure) and recovery to verify if inspiratory ribcage muscle fatigue (1) leads to slowing of contraction and relaxation properties of ribcage muscles and (2) alters median frequency and high-to-low frequency ratio (H/L). During the fatigue protocol, sternocleidomastoid showed the fastest decrease in median frequency and slowest decrease in H/L. Fatigue was also characterized by a reduction in the relative power of the high-frequency and increase of the low-frequency. During recovery, changes in mechanical power were due to changes in shortening velocity with long-lasting reduction in pressure generation, and slowing of relaxation [i.e., tau (τ), half-relaxation time (½RT), and maximum relaxation rate (MRR)] was observed with no significant changes in contractile properties. Recovery of median frequency was faster than H/L, and relaxation rates correlated with shortening velocity and mechanical power of inspiratory ribcage muscles; however, with different time courses. Time constant of the inspiratory ribcage muscles during fatigue and recovery is not uniform (i.e., different inspiratory muscles may have different underlying mechanisms of fatigue), and MRR, ½RT, and τ are not only useful predictors of inspiratory ribcage muscle recovery but may also share common underlying mechanisms with shortening velocity.

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Thoracic weighting of restrained subjects during exhaustion recovery causes loss of lung reserve volume in a model of police arrest

Scientific Reports ◽

10.1038/s41598-021-94157-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Mark Campbell ◽

Roslyn Dakin ◽

Symon Stowe ◽

Kira Burton ◽

Brianna Raven ◽

...

Keyword(s):

Electrical Impedance ◽

Human Subjects ◽

Work Of Breathing ◽

High Sensitivity ◽

Abdominal Muscle ◽

Combined Effects ◽

Impedance Tomography ◽

Head Restraint ◽

Inspiratory Muscles ◽

Life Threatening

AbstractRestraint asphyxia has been proposed as a mechanism for some arrest-related deaths that occur during or shortly after a suspect is taken into custody. Our analysis of the literature found that prone positioning, weight applied to the back, recovery after simulated pursuit, and restraint position have led to restrictive, but non life-threatening respiratory changes when tested in subsets. However, the combined effects of all four parameters have not been tested together in a single study. We hypothesized that a complete protocol with high-sensitivity instrumentation could improve our understanding of breathing physiology during weighted restraint. We designed an electrical impedance tomography (EIT)-based protocol for this purpose and measured the 3D distribution of ventilation within the thorax. Here, we present the results from a study on 17 human subjects that revealed FRC declines during weighted restrained recovery from exercise for subjects in the restraint postures, but not the control posture. These prolonged FRC declines were consistent with abdominal muscle recruitment to assist the inspiratory muscles, suggesting that subjects in restraint postures have increased work of breathing compared to controls. Upon removal of the weighted load, lung reserve volumes gradually increased for the hands-behind-the-head restraint posture but continued to decrease for subjects in the hands-behind-the-back restraint posture. We discuss the possible role this increased work of breathing may play in restraint asphyxia.

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