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Biomedical subjects

M Gorini

Publications and source records attributed to M Gorini.

At least 55 records · Page 3Linked to original sources
PubMed1995

Control of breathing in patients with limb girdle dystrophy: a controlled study.

BACKGROUND: In patients with limb girdle dystrophy the relative contribution of peripheral factors (respiratory muscle weakness, and lung and/or airway involvement) and central factors (blunted and/or inadequate chemoresponsiveness) in respiratory insufficiency has not yet been established. To resolve this, lung volumes, arterial blood gas tensions, respiratory muscle strength, breathing pattern and neural respiratory drive were investigated in a group of 15 patients with limb girdle dystrophy. An age-matched normal group was studied as a control. METHODS: Respiratory muscle strength was assessed as an arithmetic mean of maximal inspiratory (MIP) and expiratory (MEP) pressures. Breathing pattern was evaluated in terms of volume (ventilation VE, tidal volume VT) and time (respiratory frequency Rf, inspiratory time TI, expiratory time TE) components of the respiratory cycle. Neural respiratory drive was assessed as the mean inspiratory flow (VT/TI), mouth occlusion pressure (P0.1) and electromyographic activity (EMG) of the diaphragm (EMGd) and the intercostal parasternal (EMGp) muscles. In 10 of the 15 patients the responses to carbon dioxide (PCO2) stimulation were also evaluated. RESULTS: Most patients exhibited a moderate decrease in vital capacity (VC) (range 37-87% of predicted), MIP (range 23-84% of predicted), and/or MEP (range 13-41% of predicted). The arterial carbon dioxide tension (PaCO2) was increased in three patients breathing room air, while PaO2 was normal in all. Compared with the control group Rf was higher, and VT, TI and TE were lower in the patients. EMGd and EMGp were higher whilst VT/TI and P0.1 were normal in the patients. Respiratory muscle strength was inversely related to EMGd and EMGp. PaCO2 was found to relate primarily to VC and duration of illness, but not to respiratory muscle strength. During hypercapnic rebreathing delta VE/delta PCO2, delta VT/delta PCO2, and delta P0.1/delta PCO2 were lower than normal, whilst delta EMGd/delta PCO2 and delta EMGp/delta PCO2 were normal in most patients. A direct relation between respiratory muscle strength and delta VT/delta PCO2 was found. CONCLUSIONS: The respiratory muscles, especially expiratory ones, are weak in patients with limb girdle dystrophy. Reductions in respiratory muscle strength are associated with increased neural drive and decreased ventilatory output (delta VT/delta PCO2). The decrease in VC, together with the duration of disease, influence PaCO2. VC is a more useful test than respiratory muscle strength for following the course of limb girdle dystrophy.

Adult↗
PubMed1995

Effects of increased +Gz on chest wall mechanics in humans.

We studied the effects of head-to-foot acceleration (+Gz) on chest wall mechanics in five normal subjects seated in a human centrifuge. Results were compared with those previously obtained in the same subjects in microgravity during parabolic flights. In all subjects, end-expiratory abdominal pressure (Pga) and volume (Vab) increased with Gz. On average, end-expiratory Pga increased from 7.4 +/- 1.7 cmH2O at + 1 Gz to 14.9 +/- 2.8 cmH2O at + 3 Gz and end-expiratory Vab increased by 0.32 +/- 0.06 liter between + 1 and + 3 Gz. On the other hand, the abdominal contribution to tidal volume (Vab/VT) and abdominal compliance decreased from 34.7 +/- 5.9% and 52 +/- 6 ml/cmH2O at + 1 Gz to 29.3 +/- 5.1% and 26 +/- 4 ml/cmH2O at + 3 Gz, respectively. Changes in end-expiratory Pga were linear between 0 and + 3 Gz, but changes in end-expiratory Vab, Vab/VT, and abdominal compliance were greater in microgravity than in hypergravity. In contrast to weightlessness, which did not alter minute ventilation and tidal changes in Pga and transdiaphragmatic pressure, these variables increased with increasing Gz. These results indicate that, although changes in Gz have a linear effect on abdominal transmural pressure, hypergravity and weightlessness do not have symmetrical effects on chest wall mechanics.

Abdomen↗
PubMed1995

Carbon dioxide responsiveness in COPD patients with and without chronic hypercapnia.

To ascertain whether and to what extent the reduced ventilatory response to a hypercapnic stimulus in chronic obstructive pulmonary disease (COPD) patients depends on a blunted chemoresponsiveness of central origin or to mechanical impairment, we studied two groups of COPD patients without (group A) and with (group B) chronic hypercapnia, but with similar degrees of airway obstruction and hyperinflation. The study was performed on 17 patients (9 normocapnic and 8 hypercapnic). Six age-matched normal subjects (group C) were also studied as a control. During a CO2 rebreathing test, ventilation (VE), mouth occlusion pressure (P0.1), and the electromyographic activity of diaphragm (Edi) were recorded and then plotted against end-tidal carbon dioxide tension (PCO2). Inspiratory muscle strength was significantly lower in the hypercapnic group (group B) compared to normocapnic group (A), and in these groups compared to the control group (C). Both patient groups exhibited significantly lower delta VE/delta PCO2 than the control group. In hypercapnics, delta P0.1/delta PCO2 was significantly lower than in normocapnics and control group, whilst mouth occlusion pressure as % of maximal inspiratory pressure delta P0.1 (% MIP)/delta PCO2 did not differ significantly among the three groups. delta Edi/delta PCO2 increased from C to A. At a PCO2 of 8.65 kPa, VE was similar in the normocapnic and control group, but lower in hypercapnics; Edi was similar in hypercapnic and control group; but greater in normocapnics. P0.1(% MIP) did not differ significantly among groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Effects of the iron lung on respiratory function in chronic hypercapnic COPD patients.

Whether or not short-term negative pressure ventilation (NPV) improves respiratory function by decreasing the drive to the respiratory muscles in hypercapnic chronic obstructive pulmonary disease (COPD) patients remains to be defined. In six severely obstructed hypercapnic COPD patients (Group A) with grade IV dyspnoea (modified Medical Research Council (MRC) dyspnoea scale), we evaluated pulmonary volumes, arterial blood gases, the pattern of breathing (tidal volume (VT) and respiratory frequency (Rf)) and the neuromuscular respiratory drive (NMRD), before and immediately after a 7 day period with the iron lung (IL). NMRD was assessed by expressing mouth occlusion pressure (P0.1) recorded during quiet breathing as a percentage of maximal P0.1 recorded during exogenous CO2 stimulation (P0.1 max,CO2). A group of six hypercapnic, less dyspnoeic (grade II to III) COPD patients (Group B), with similar mechanical characteristics, and another less obstructed historically normocapnic control group (Group C) were also considered. Before IL, in Group A VT was lower than in C, and P0.1 (%P0.1 max,CO2) was greater than in Group B and C. After a 7 day period with IL, VT increased, Rf decreased, and arterial blood gases and dyspnoea grade improved; P0.1 (%P0.1 max,CO2) significantly decreased remaining, however, greater than in Group C. In Group A the time course of arterial carbon dioxide tension (Pa,CO2) and P0.1 (%P0.1 max,CO2) were significantly related to each other. These data seem to indicate that IL is effective in improving respiratory function and symptoms in chronic hypercapnic severely dyspnoeic COPD patients. The observation that these effects were associated with a decrease in NMRD reflects an improved efficiency of the respiratory system. After IL, respiratory function in Group A was similar or even better than that in Group B. This study also considers the possibility of putting severely dyspnoeic hypercapnic COPD patients into an IL trial before starting a traditional rehabilitation programme.

Aged↗
PubMed1994

Histamine induced changes in breathing pattern may precede bronchoconstriction in selected patients with bronchial asthma.

BACKGROUND: In asthmatic patients methacholine or histamine challenge may result in more rapid and shallow breathing. Bronchoconstriction can also be associated with changes in the pattern of breathing. However, few studies, particularly in patients with asthma, have investigated the possibility that changes in the pattern of breathing may precede the onset of bronchoconstriction. METHODS: Eight subjects were selected from 34 consecutive asthmatic patients who had previously exhibited a significant increase in respiratory frequency (Rf) and decrease in tidal volume (VT) accompanying a 20% or greater fall in FEV1 during a histamine bronchial provocation test. These patients also had bronchial hyperresponsiveness (histamine PC20FEV1 0.1-0.25 mg/ml). VT, Rf, and the ratio of VT to Rf were evaluated breath by breath under control conditions and two minutes after inhalation of either saline or each of a series of progressively increasing concentrations of histamine. In each subject the coefficient of variation (CV) for each breathing pattern variable was calculated under control conditions and at each histamine concentration over at least 30-40 breaths. For FEV1, VT and Rf step by step coefficients of variation were averaged and the mean (2SD) CV was considered to represent a threshold value in each patient. RESULTS: Histamine challenge resulted in increased Rf and Rf/VT, and decreased VT and FEV1. In all but one subject change in Rf and Rf/VT beyond the threshold value preceded change in FEV1 beyond the threshold value. The threshold concentrations of histamine for Rf and Rf/VT did not correlate with the threshold value for FEV1. CONCLUSIONS: In selected asthmatic patients a change in breathing pattern occurs prior to a change in FEV1. These results suggest that narrowing of the airways, in terms of decrease in FEV1, does not play a major part in the initial change in the pattern of breathing. This may be caused by direct stimulation of vagal airway receptors.

Adult↗
PubMed1994

Adverse effect of hyperinflation on parasternal intercostals.

The force-generating ability of the parasternal intercostals is maintained during acute hyperinflation in the dog (Jiang et al. Am. Rev. Respir. Dis. 139: 522-528, 1989). In the present studies, we assessed whether the ability of these muscles to expand the rib cage and inflate the lungs is really maintained. We thus measured the electromyogram and the changes in length of these muscles, the axial motion of the sternum and the ribs, and the changes in pleural pressure and tidal volume in anesthetized vagotomized phrenicotomized dogs during selective parasternal stimulation and during spontaneous breathing at different lung volumes corresponding to 0, 5, 10, and 15 cmH2O positive airway pressure. Compared with functional residual capacity, parasternal stimulation at 15 cmH2O positive airway pressure caused a mild decrease in muscle shortening, a large reduction in cranial rib motion, and a large reduction in pleural pressure fall. The caudal displacement of the sternum, however, was increased. Similar alterations in rib and sternal motions and in muscle shortening were seen during spontaneous breathing; tidal volume was markedly reduced as well. These observations thus indicate that hyperinflation affects the action of the parasternal intercostals on the rib cage; their rib-elevating action is decreased, whereas their action on the sternum is increased. As a result, their ability to inflate the lung is reduced. Thus, the inflationary actions of both the diaphragm and parasternal intercostals are reduced by hyperinflation.

Animals↗
PubMed1994

Aminophylline and respiratory muscle interaction in normal humans.

The effects of intravenous infusion of aminophylline on respiratory muscle interaction were examined in seven normal subjects breathing at rest. Rib cage (RC-Ap) and abdominal (AB-Ap) volume displacements, pleural (Ppl), gastric (Pg), and transdiaphragmatic (Pdi) pressure swings, and electromyographic activity of the diaphragm (Edi) and the parasternal (Eps) muscles were measured under control and during infusion of either aminophylline or placebo in a double-blind randomized manner. Compared with placebo, aminophylline induced an increase in ventilation (p < 0.01) that was mainly accounted for by an increase in tidal volume (p = 0.01). Aminophylline induced a significant and similar increase in RC-Ap and AB-Ap as associated with increased Ppl and Pg swings (p = 0.002, and p < 0.01, respectively). On the contrary, no changes in end-expiratory RC and AB volume and in Ppl and Pg at end-expiration were observed, indicating that expiratory muscles did not contribute to the increase in tidal volume. Edi and Eps increased significantly with aminophylline, whereas Pdi/Edi ratio remained unchanged. We conclude that in normal humans breathing at rest: (1) aminophylline increases ventilation, promoting larger tidal volume; (2) this effect is due to increased neural drive to inspiratory muscles; (3) aminophylline does not promote any appreciable expiratory muscle recruitment and distortion in the pattern of chest wall motion.

Adult↗
PubMed1994

Evidence of dynamic airway compression during cough in tetraplegic patients.

Although all the well-recognized muscles of expiration are paralyzed after traumatic transection of the lower cervical cord, tetraplegic subjects can still empty their lungs actively by contracting the clavicular portion of the pectoralis major. It is not known, however, whether contraction of this muscle bundle may raise pleural pressure enough to cause dynamic compression of the intrathoracic airways, which is critical for the production of an effective cough. To investigate this question, we measured expiratory flow rate and esophageal pressure during a series of forced expiratory vital capacity (VC) maneuvers in twelve subjects with C5-8 traumatic tetraplegia and constructed isovolume-pressure flow (IVPF) curves. The curves were interpretable with certainty in nine patients. Three of them did not show any plateau of flow. On the other hand, six patients had clearcut plateaus of flow on all IVPF curves between 80-60 and 20% VC, suggesting they had dynamic airway compression. Videoendoscopic recordings in two patients confirmed trachea and main bronchi collapse during forced expiration and cough. We conclude, therefore, that contraction of the pectoralis major causes dynamic airway compression during expiratory efforts in a substantial proportion of tetraplegic subjects. Increasing the pressure-generating capacity of this muscle might thus improve the effectiveness of cough and reduce the prevalence of bronchopulmonary infections.

Adult↗
PubMed1994

Four-week negative pressure ventilation improves respiratory function in severe hypercapnic COPD patients.

Studies on respiratory muscle resting by negative pressure ventilation (NPV) in patients with stable COPD have given conflicting results. Probable explanations lie in criteria of patients' selection, method of NPV application, and lack of supervision of respiratory muscle rest. Thirteen hypercapnic patients with COPD were, therefore, randomly assigned to either a NPV group or a control group. The NPV was applied by an airtight jacket (pneumosuit), 5 h a day, 5 consecutive days a week for 4 weeks. Both NPV group and control group performed in-hospital pulmonary rehabilitation program for a 4-week period. Arterial blood gases, spirometry, maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP), breathing pattern, and electromyogram (EMG) of the diaphragm and parasternal intercostal muscles were measured on the preintervention day, and at the end of the second and fourth weeks of treatment (days 13 and 27, respectively). The short-term effect of NPV on EMG suppression was also checked throughout the ventilatory sessions in three different days (1, 12, and 26, respectively). A 6-min walking test (WT) and level of dyspnea by a modified Borg scale were evaluated on the preintervention and the last days. Negative pressure ventilation resulted in a significant reduction in EMG activity of both diaphragm and parasternal muscles, associated with significant increase in MIP, tidal volume, and ventilation, and increase in PaO2 and decrease in PaCO2. A significant relationship between change in MIP and change in PaCO2 was observed (r = 0.72, p < 0.01). Improve-ment in 6-min WT and dyspnea sensation was also observed, both being the sole changes in the control group. These data seem to indicate a beneficial role of respiratory muscle rest in improving respiratory function. Adequate supervision by personnel familiar with the equipment is likely to contribute to successful treatment.

Action Potentials↗
PubMed1994

Iron lung treatment of acute on chronic respiratory failure: 16 yrs of experience.

Noninvasive ventilatory supports are gaining a prominent position among ventilatory techniques aimed to improve ventilation in patients with acute-on-chronic respiratory failure (ACRF). It has not yet been established whether these techniques can be considered as a preventive measure to avoid the need for endotracheal intubation, or are really another means to provide full ventilatory support. At our respiratory intensive care unit (RICU), the ventilatory treatment of ACRF has, for many years, been based on a conservative method, which relies on the use of a body ventilator (iron lung) providing intermittent negative pressure ventilation (INPV). From 1975 to 1991, we treated ACRF in 2,116 patients with chronic obstructive pulmonary disease (COPD) and 604 patients with restrictive thoracopulmonary disease (RTD). Two thousand and eleven patients (95%) underwent INPV. The mortality rate during hospitalization was 9.9% for the patients as a whole (10% and 8.9% for COPD and RTD patients, respectively). The mean length of stay in the RICU was 10.5 +/- 9.5 days. Furthermore, we report the results of our previous studies which investigated how the iron lung works, and how it affected the short- and long-term prognosis of COPD patients in ACRF. Finally, in 180 patients, we report the effects of INPV provided by iron lung on the treatment of ACRF with hypoxic hypercapnic coma (HHC). INPV resulted in a significant improvement of arterial blood gas values and pH, associated with a progressive recovery of the level of consciousness. Only 13 patients needed intubation and 41 (23%) died during hospitalization.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1993

Control of breathing in patients with severe hypothyroidism.

PURPOSE: Hypothyroid patients have been reported to have a blunted ventilatory response to carbon dioxide stimulation. However, previous data did not clarify the localization of abnormalities responsible for that disorder. The present investigation was aimed at evaluating to what extent central (neural) and/or peripheral (muscular) factors are involved in the abnormalities of the ventilatory control system in hypothyroid patients. PATIENTS AND METHODS: We studied 13 patients with severe hypothyroidism before and after 6 to 9 months of replacement therapy; 7 age- and sex-matched normal subjects were also studied as a control. In each subject, we assessed (1) inspiratory muscle strength by measuring maximal inspiratory pressure (MIP), and (2) respiratory control system during a carbon dioxide rebreathing test by measuring minute ventilation (VE), tidal volume (VT), mean inspiratory flow (VT/TI), and electromyographic (EMG) activity of the diaphragm (Edi) and intercostal (Eint) muscles. RESULTS: Compared with the normal control group (Group C), patients exhibited similar MIP, and similar VE and EMG response slopes to carbon dioxide. However, evaluating individual VE response slopes, we were able to identify two subsets of patients: Group A (six patients) with low VE response (less than mean -SD.1.65 of Group C) and Group B (seven patients) with normal VE response. Compared with both Groups B and C, Group A exhibited significantly lower VT/TI, Edi, and Eint response slopes; the difference between Groups B and C was not significant. Six patients (two from Group A and four from Group B) exhibited low MIP values compared with that in Group C. After replacement therapy, (1) VE, VT/TI, and Edi response slopes increased significantly in Group A; and (2) MIP increased, but not significantly in patients with low MIP. CONCLUSIONS: We conclude that: (1) In patients with severe hypothyroidism, the ventilatory control system may be altered at the neural level, as indicated by a blunted chemosensitivity; (2) Impaired respiratory muscle function does not seem to play a major role in the decreased ventilatory response to carbon dioxide stimulation; (3) Replacement therapy appears to normalize the response to hypercapnic stimulation, but not respiratory muscle strength.

Adult↗
PubMed1993

Respiratory response to abdominal and rib cage muscle paralysis in dogs.

To assess the respiratory response to abdominal and rib cage muscle paralysis, we measured tidal volume, esophageal and gastric pressures, arterial blood gases, and the electromyogram (EMG) of the diaphragm during progressive epidural anesthesia (lidocaine 2%) in 35 supine anesthetized dogs. The EMG activity of the diaphragm was measured with fine-wire electrodes; the abdominal cavity was thus left intact. Paralysis of the abdominal muscles alone did not produce any alterations. In contrast, when all rib cage muscles were also paralyzed, there were substantial increases in the peak height and the rate of rise of diaphragmatic EMG activity that were associated with a decrease in tidal volume and an increase in arterial PCO2 (PaCO2); swings in transdiaphragmatic pressure, however, were unchanged. The increased diaphragmatic activation due to rib cage muscle paralysis persisted after bilateral cervical vagotomy and was well explained by the increased PaCO2. These observations indicate that in the dog 1) the rib cage muscles contribute significantly to tidal volume, and their paralysis causes, through the increased hypercapnic drive, a compensatory increase in diaphragmatic activation; and 2) the rib cage inspiratory muscles enhance the diaphragm's ability to generate pressure during breathing.

Abdomen↗
PubMed1993

Preventive effects of beclomethasone on histamine-induced changes in breathing pattern in asthma.

Bronchial mucosa inflammation is a hallmark of asthma. Epithelial damage due to inflammatory process may contribute to induce a pattern of rapid and shallow breathing (RSB). Probably due to its effects on inflammatory process, beclomethasone dipropionate (BDP) decreases bronchial hypersensitivity (BH), as assessed in terms of histamine concentration causing a 20 percent FEV1 decrease from saline solution (PC20FEV1); however, no data are available on the effect of BDP on RSB. We studied 32 asymptomatic asthmatic subjects with a severe to moderate levels of BH (PC20FEV1 0.01 to 1.7 mg/ml). After they were randomly assigned to one month of either BDP (2 mg daily, 17 patients) or placebo (15 patients), they inhaled progressively doubling concentrations of histamine phosphate by tidal breathing method. With histamine in seven BDP-treated and in five placebo-treated patients, decrease in FEV1 > or = 20 percent from saline solution was paralleled by a significant decrease in tidal volume (VT), inspiratory time (Ti), and expiratory time (Te), and increase in respiratory frequency (RF). In the remaining patients, histamine failed to change the breathing pattern. In the seven RSB patients, BDP resulted in a smaller VT decrease (p < 0.02) and a smaller RF increase (p < 0.02) with histamine. The five RSB placebo-treated patients were then given one month BDP (2 mg daily): inhaled BDP, but not placebo, resulted both in a significant increase in PC20FEV1 and modulation in histamine-induced changes in breathing pattern. We conclude that high doses of BDP seem to be able to modulate histamine-induced RSB, an effect that might be linked to reversal of airway inflammation.

Adolescent↗
PubMed1993

Effects of intravenous broxaterol on respiratory drive and neuromuscular coupling in COPD patients.

Broxaterol, a new selective beta 2-agonist, has been shown to exert inotropic effects on both fresh and fatigued canine diaphragm. We evaluated the effect of broxaterol on the activation and force output of the respiratory muscles in patients with chronic obstructive pulmonary disease (COPD). We studied 9 patients with moderate to severe COPD. Each patient was infused with saline and Broxaterol (200 micrograms) in saline alternately. We measured lung volumes, maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), breathing pattern, P0.1, respiratory muscle EMG (diaphragm, EMGd, and parasternal, EMGp) and P0.1/EMGd ratio. Measurements were made under control conditions and at 15, 30, 60, and 120 min after each infusion. Broxaterol, but not saline, resulted in a slight but significant increase in vital capacity (VC), forced expiratory volume in one second (FEV1) and MIP, and a decrease in functional residual capacity (FRC). Breathing pattern did not change, while EMG significantly decreased, and P0.1/EMGd significantly increased in 5 of the 9 patients after broxaterol. These data seem to indicate that by partially unloading the respiratory muscles, broxaterol results in decreased muscle activation (EMG). Increase in chest wall neuromuscular coupling (P0.1/EMGd) may also be observed.

Adrenergic beta-Agonists↗
PubMed1993

Control of breathing in patients with neuromuscular diseases.

We reviewed the studies devoted to investigate the control of breathing in patients with neuromuscular diseases. Neural respiratory drive has been assessed in terms of minute ventilation and mouth occlusion pressure (P0.1) in patients with several types of neuromuscular affections (amyotrophic lateral sclerosis, poliomyelitis and post-polio syndrome, Guillain Barré syndrome, muscular dystrophies, inflammatory muscle diseases). More recently we have used electromyographic activity of diaphragm to evaluate neural drive in patients with myasthenia gravis and muscular dystrophies. The results of these studies seem to indicate that patients with myasthenia gravis are not likely to have a decreased respiratory drive, the disorder in neuromuscular transmission being probably the reason for the apparent decrease in diaphragmatic neural activation during hypercapnic stimulation. Increase in neural afferent information from lung and/or rib cage might explain both the increased neural respiratory drive and the faster breathing observed in patients with neuromuscular disease.

Humans↗
PubMed1992

Action of the diaphragm during cough in tetraplegic subjects.

Subjects with traumatic tetraplegia use the pectoralis major to compress the upper rib cage and increase intrathoracic pressure during cough. It is not known, however, whether they also contact the diaphragm during the expiratory phase of cough, as normal subjects do. We have investigated the action of the diaphragm during single voluntary coughing efforts in subjects with complete transection of the lower cervical (n = 5) or midthoracic (n = 2) cord. All subjects showed at least one peak of transdiaphragmatic pressure during the expiratory phase of the effort, and simultaneous bursts of electrical activity were recorded from the diaphragm. Coughing also resulted in an outward (paradoxical) motion of the abdomen during the compressive phase. We conclude that antagonistic contraction of the diaphragm is present during the expiratory phase of cough in spinal cord-injured subjects with paralysis of the abdominal muscles; this contraction, therefore, does not occur in response to activation of these muscles. The present results also indicate that the cough-induced paradoxical expansion of the abdomen is due to contraction of the pectoralis major and not of the diaphragm.

Adult↗
PubMed1992

Rib cage shape and motion in microgravity.

We studied the effect of microgravity (0 Gz) on the anteroposterior diameters of the upper (URC-AP) and lower (LRC-AP) rib cage, the transverse diameter of the lower rib cage (LRC-TR), and the xiphipubic distance and on the electromyographic (EMG) activity of the scalene and parasternal intercostal muscles in five normal subjects breathing quietly in the seated posture. Gastric pressure was also recorded in four subjects. At 0 Gz, end-expiratory LRC-AP and xiphipubic distance increased but LRC-TR invariably decreased, as did end-expiratory gastric pressure. No consistent effect was observed on tidal LRC-TR and xiphipubic displacements, but tidal changes in URC-AP and LRC-AP were reduced. Although scalene and parasternal phasic inspiratory EMG activity tended to decrease at 0 Gz, both muscle groups demonstrated an increase in tonic activity. We conclude that during brief periods of weightlessness 1) the rib cage at end expiration is displaced in the cranial direction and adopts a more circular shape, 2) the tidal expansion of the ventral rib cage is reduced, particularly in its upper portion, and 3) the scalenes and parasternal intercostals generally show a decrease in phasic inspiratory EMG activity and an increase in tonic activity.

Electromyography↗