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At least 1,225 records · Page 68Linked to original sources
PubMed1979

Contribution of rib cage and abdomen-diaphragm to tidal volume during CO2 rebreathing.

In man, there is wide interindividual range in the tidal volume response to CO2. To determine which (rib cage or abdomen-diaphragm) compartment had a greater influence on this range, ventilatory response to CO2 was measured, using Read's method, in eight men and two women seated in a constant-pressure body plethysmograph. Rib cage and abdominal tidal volume was simultaneously measured using magnetometers. Correcting for body size, the tidal volume response of the abdominal compartment was similar in all subjects, whereas that of the rib cage was larger in subjects with high tidal volume response to CO2; a significant correlation was found (P less than 0.01). Rib cage volume displacement lagged behind abdominal in all subjects; phase lag was greatest in the subject with the lowest ventilatory response to CO2. These results suggest that, at high levels of ventilation, a larger volume displacement of the rib cage may reflect a more effective coupling of the diaphragm pressure generator to it or alternatively a reduction in its impedance relative to the abdominal compartment.

Abdominal Muscles↗
PubMed1996

Regulation of ventilatory muscle blood flow.

The ventilatory muscles perform various functions such as ventilation of the lungs, postural stabilization, and expulsive maneuvers (e.g., coughing). They are classified in functional terms as inspiratory muscles, which include the diaphragm, parasternal intercostal, external intercostal, scalene, and sternocleidomastoid muscles; and expiratory muscles, which include the abdominal muscles, internal intercostal, and triangularis sterni. The ventilatory muscles require high-energy phosphate compounds such as ATP to fuel the biochemical and physical processes of contraction and relaxation. Maintaining adequate intracellular concentrations of these compounds depends on adequate intracellular substrate levels and delivery of these substrates by arterial blood flow. In addition to the delivery of substrates, blood flow influences muscle function through the removal of metabolic by-products, which, if accumulated, could exert negative effects on several excitatory and contractile processes. Skeletal muscle substrate utilization is also dependent on the ability to extract substrates from arterial blood, which, in turn, is accomplished by increasing the total number of perfused capillaries. It follows that matching perfusion to metabolic demands is critical for the maintenance of normal muscle contractile function. In this article, I review the factors that influence ventilatory muscle blood flow. Major emphasis is placed on the diaphragm because a large number of published reports deal with diaphragmatic blood flow. The second reason for focusing on the diaphragm is because it is the largest and most important inspiratory muscle.

Animals↗
PubMed1988

The rib cage and abdominal components of respiratory system compliance in tetraplegic patients.

The specific compliance of the chest wall and lungs combined was measured in eight patients with stable tetraplegia. Expiration was impeded with a series of spring-loaded resistances, and end-expiratory pressures plotted against changes in chest wall volume at end-expiration. An optical contour mapping system was used to partition changes in chest wall volume into rib cage and abdominal components. These measurements suggest that the compliance of the whole system is reduced by one third in patients with stable tetraplegia, compared with normal subjects. This may be because of abnormal stiffening of the rib cage.

Abdominal Muscles↗
PubMed1993

[The development of periodic apneic breathing during the activation of the GABA-ergic system of the brain].

Experiments on sodium pentobarbital (40 mg/kg i.p.) anesthetized mongrel cats of either sex weighing from 2.25 to 4.25 kg showed that administration of sodium hydroxybutyrate (200 mg/kg, i.v.) resulted in periodic apneic breathing with inspiratory arrests in more than 80%. An abrupt decrease of respiratory rate and thus ventilation was conditioned by a prolonged activation of inspiratory muscles (diaphragm and external intercostals). Under these conditions, the activity of expiratory muscles (internal intercostals and abdominal muscles) was not depressed. The changes in the respiratory pattern were not due to alterations in systemic hemodynamics. The periodic breathing affected the arterial blood components as follows: the most pronounced variations were in pO2 less pronounced ones in pCO2 and the smallest ones in pH. After the periodic apneic breathing formation, vagotomy either produced no marked alterations in the respiratory pattern or even promoted restoration of more regular breathing. It is assumed that the activation of GABA-ergic system of the brain can interfere with the generation of the respiratory rhythm depressing the "switch-off" mechanism and breaking the vagal afferent transmission to the neurons of respiratory centre.

Afferent Pathways↗
PubMed1980

The role of respiratory muscles in the hyperinflation of bronchial asthma.

To examine the mechanism of hyperinflation in bronchial asthma we studied lung and chest wall mechanics in 7 asymptomatic patients in whom progressive bronchoconstriction was induced by doubling the amount of inhaled aerosolized histamine. An increase in pulmonary resistance (RL) from 2.5 +/- 0.3 cmH2O . 1-1 . s (mean, +/- 1 SE) to 12.3 +/- 0.9 cmH2 was associated with a linear increase in functional residual capacity (FRC) up to 74.7 +/- 1.7% of control total lung capacity (TLCc). The mean regression coefficient was 2.3% TLCc . cmH2O-1 . 1 . s-1. At each level of hyperinflation the most positive expiratory pleural pressures measured during spontaneous breathing were generally less than the predicted chest wall relaxation pressures, indicating persistent inspiratory muscle contraction throughout expiration. This was predominantly due to inspiratory intercostal and accessory muscle activity, because measurements of transdiaphragmatic pressure indicated complete diaphragmatic relaxation early in expiration. Recruitment of abdominal muscles during expiration, inferred from measurements of gastric pressure (Pg) and abdominal antero-posterior (A-P) diameter, was progressively more apparent with increasing bronchoconstriction. We concluded that the increase in FRC in induced asthma is substantially influenced by persistent inspiratory intercostal and accessory muscle activity during expiration. Concomitant abdominal muscle recruitment results in a chest wall configuration that tends to optimize diaphragmatic function.

Abdomen↗
PubMed1984

Gate mechanism in breathlessness caused by chest wall vibration in humans.

The effects of bilateral alternating out-of-phase vibrations were studied in 10 normal healthy subjects and five asthmatic patients. The second or third intercostal spaces were vibrated during expiration, and the seventh to ninth intercostal spaces were vibrated during inspiration. Most subjects sensed breathlessness during such vibrations, and 100 Hz was most effective. The degree of breathlessness correlated positively with increased respiratory rate. Respiratory rate increased from 14.1 +/- 3.78 (mean +/- SD) to 22.3 +/- 7.14 breaths/min (P less than 0.05) during relatively severe breathlessness and to 20.39 +/- 5.66 breaths/min (P less than 0.05) during less uncomfortable sensation. Slight or negligible breathlessness induced no significant increase in rate (15.33 +/- 4.19 breaths/min). All asthma patients described the sensations during vibration as similar to those during asthma attacks, and their respiratory rates increased 20.7 +/- 11.03% during 100 Hz vibration (P less than 0.01). It is suggested that the uncomfortable sensation of breathlessness may be induced by muscle spindles in the intercostal muscles being activated out of phase with the respiratory cycle. The central mechanism that receives the intercostal afferents may have a certain gate that operates in relation to the sensation of breathlessness.

Adult↗
PubMed1983

Mechanism of functional residual capacity increase in haemorrhagic shock.

Shock was elicited in anaesthetized dogs by maintaining a haemorrhagic hypotension of 4 kPa until 30 per cent spontaneous refusion, followed by total reinfusion. Functional residual capacity (FRC) and minute ventilation increased considerably similarly to our previous experiments. Lactate content in both the external intercostal and the biceps femoris muscles increased significantly in advanced shock. The expiratory external abdominal oblique muscle showed electromyographic signs of fatigue. At the height of the FRC changes tonic contraction of the external intercostal muscle could be demonstrated electron microscopically. This tonic contraction is the main factor in the large FRC rise in late shock forming the basis of a hitherto unknown vicious circle.

Abdominal Muscles↗
PubMed1980

Respiratory function of the larynx in developing sheep and the influence of sleep state.

The activities of laryngeal abductor and adductor muscles were recorded in conjunction with other respiratory muscles in unanaesthetized chronically monitored foetal, newborn and adult sheep. In foetuses, rhythmical breathing movements occurred in the presence of rapid eye movements and a low voltage electrocorticogram (REM state) and were accompanied by phasic laryngeal abduction; adductor muscles and intercostals were largely inactive. During the foetal non-REM state laryngeal adductor muscles were tonically active at a low level, but the glottis remained open. Deep inspiratory efforts which occurred at low frequency in this behavioural state were not accompanied by abductor activity and resembled inspiratory efforts associated with regurgitation in ruminants. After birth, expiratory adductive activity of the larynx was also maximal during non-REM sleep and negligible during REM sleep. Active laryngeal adduction was accompanied by delayed expiratory airflow, prolonged TE and reduced respiratory frequency. Adduction of the larynx is dependent on behavioural state and appears to be the principal means of regulating TE in sheep, particularly during early post-natal development.

Action Potentials↗