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Results for “Diaphragmatic function”

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PubMed1993

[Development of the diaphragmatic muscle].

Muscle biopsies were taken at the oesophageal opening and in the costal part of the diaphragm from 15 foetuses (aged between 11 and 40 weeks) and from four children aged 1 week, 5 months, 3 and 16 years. Subjects with multiple congenital abnormalities or neuromuscular diseases were not included in this study. Enzyme histochemistry (myosin ATPases) and immunohistochemistry using antibodies directed against vimentin, desmin, titin and different isoforms of the myosin heavy chains (MHCs) were carried out on serial frozen sections. The diameters of the different types of fibres were measured using a Leitz ASM 68K and the corresponding results were expressed either as mean values or as histograms. In both of the regions of the diaphragm which were examined (oesophageal opening and costal portion). The skeletal muscle fibres are formed from two successive generations in a manner very similar to that which we have previously described for the limb muscles. The chronology of the various events involved in the maturation of the diaphragm does however present certain distinctive features since the adult MHCs are expressed well before 30 weeks even though paradoxically large amounts of fetal MHC were still present at birth. These findings suggest the existence of a special regulatory mechanism in the diaphragm resulting either from its innervation by the phrenic nerve or from its specific functional constraints.

Adolescent↗

PubMed2003

Posterior pituitary bright spot in large adenomas: MR assessment of its disappearance or relocation along the stalk.

PURPOSE: To evaluate the disappearance or relocation patterns of posterior pituitary bright spot (PPBS) in the infundibuloneurohypophyseal (INH) system and endocrinologic implications in large pituitary adenomas. MATERIALS AND METHODS: Sixty-nine patients with adenoma and supradiaphragmatic extension were classified into PPBS-visible and PPBS-nonvisible groups on the basis of findings at preoperative T1-weighted magnetic resonance (MR) imaging. The adenoma shapes were classified into hourglass type with indentation and barrel type without indentation at the diaphragmatic level. RESULTS: The PPBS-visible group included 55 (80%) patients. PPBS most commonly occurred at the distal pituitary stalk immediately above the diaphragm in 48 patients with hourglass-type adenoma. In the remaining seven patients with barrel-type adenoma, PPBS occurred in the sella or in varying sites along the pituitary stalk. Postoperatively, two patients, whose PPBS became nonvisible, developed persistent diabetes insipidus. The PPBS-nonvisible group included 14 (20%) patients. Five had hourglass-type and nine had barrel-type adenoma. Occurrence of the barrel type was marked. In these patients, four developed postoperative permanent diabetes insipidus. CONCLUSION: The diaphragm, a probable major anatomic determinant of indentation, may serve as a transportation blockade and facilitate proximal accumulation of PPBS material, as evidenced in the hourglass-type adenoma. PPBS was more commonly nonnvisible in the barrel-type adenoma. The presence of PPBS in the INH system indicates its functional maintenance in large adenomas.

Adenoma↗

PubMed1992

Resistive breathing activates the glutathione redox cycle and impairs performance of rat diaphragm.

Free radical activation and lipid peroxidation have been described in skeletal muscle during strenuous exercise. We hypothesized that oxygen radicals could also be formed in the diaphragm muscle during strenuous resistive breathing and that these radicals might affect diaphragm function. Seven control and 12 experimental male Sprague-Dawley rats were studied. Six experimental animals were subjected to resistive breathing (RB) alone and six animals received 15 min of mechanical ventilatory support (MV) after the resistive breathing period. Inspiratory resistance was adjusted to maintain airway opening pressure at 70% maximum in both groups until exhaustion. Diaphragm samples were obtained for analysis of thiobarbituric acid-reactive substances (TBAR), reduced glutathione (GSH), and glutathione disulfide (GSSG). In vitro isometric contraction times, twitch (Pt) tension and maximum tetanic (Po) tension, force-frequency curves, fatigue index, and recovery index were measured. In RB and MV compared with controls, there were significant decreases in Pt and Po. Diaphragm TBAR concentrations were increased in MV compared with controls or RB. GSSG-to-total glutathione ratio was increased in RB and MV compared with controls. Production of free radicals during RB and MV may represent an important mechanism of diaphragmatic injury that could contribute to the decline in contractility.

Airway Resistance↗

PubMed2000

Diaphragm structure and function in the Florida manatee (Trichechus manatus latirostris).

Relative to many other mammals, little is known about the functional morphology of the four extant species of the order Sirenia. In this study, 166 Florida manatee (Trichechus manatus latirostris) carcasses fresh enough to collect detailed anatomical information were examined to describe the gross anatomy of the diaphragm. Our results show that the Florida manatee's diaphragm differs from those of other mammals in that it: lies in a dorsal plane, rather than in the more typical transverse plane; is located dorsal to the heart and does not attach to the sternum; and attaches medially at the "I"-shaped central tendon to bony projections extending ventrally from the vertebral bodies, forming two distinct hemidiaphragms. The manatee's transverse septum is a separate structure that lies at a right angle to the diaphragm and separates the heart from the liver and other viscera. The extreme muscularity of the diaphragm and the ability of manatees to adjust their position in the water column with minimal external movement suggest that diaphragmatic contractions may change the volume of each pleural cavity to affect buoyancy, roll, and pitch. We also hypothesize that such contractions, in concert with contractions of powerful abdominal muscles, may compress gas in the massive large intestine, and thereby also contribute to buoyancy control.

Animals↗

PubMed1977

Thoracic reflexes stabilizing loaded ventilation in normal and cord-injured man.

The ability to regulate tidal volume was quantified in 24 cervical cord-injured patients by comparing the "effective" elastance (E'rs) observed during single-breath elastic loads to the passive respiratory elastance (Ers) measured separately with relaxed muscles. Thirteen patients, the majority of whom had an abnormal subjective perception of loading, usually failed to demonstrate any tidal volume compensation under load conditions (i.e. E'rs less than or equal to Ers). This impaired tidal volume defense, which could not be attributed either to diaphragmatic paralysis or rib cage instability, was accompanied by a markedly shortened inspiratory duration and, hence, a prematurely terminated phrenic motoneuron output. Conversely, those patients who developed a larger then previously reported "effective" elastance (i.e., E'rs greater than or equal to 2Ers) described loading as an inspiratory obstruction, as did all our normal subjects, and usually prolonged loaded inspiratory duration, probably by a consciously mediated mechanism. These findings are consistent with the hypothesis that, in spontaneously breathing intact man, thoracic sensory receptors normally maintain phrenic motoneuron output under load conditions and thereby promote tidal volume stability.

Adolescent↗

PubMed1998

Imaging evaluation of the diaphragm.

The diaphragm performs most of the physiologic work of inspiration, and forms an anatomic barrier between the thoracic and abdominal cavities. Disorders of the diaphragm can be related to impairment of either of these functions, and most have radiologic manifestations. Both intrathoracic and intra-abdominal disease processes can alter the normal radiologic appearance of the diaphragm. Abnormalities are usually first detected on chest radiographs, often incidentally in asymptomatic patients, and many require further characterization by other imaging studies for definitive diagnosis. Fluoroscopy, CT, and MR imaging are frequently the most useful additional studies, whereas ultrasonography, barium contrast studies, and liver-spleen scintigraphy are occasionally helpful. Selection of the most appropriate radiologic technique in a given clinical situation can greatly facilitate the diagnosis of diaphragm abnormalities.

Diagnostic Imaging↗

PubMed1979

Patterns of postcibal gastroesophageal reflux in symptomatic infants.

Symptomatic infants displayed three patterns of gastroesophageal reflux after drinking apple juice (20 ml/kg or 300 ml/m2 of body surface area). The type I pattern occurred in patients who had continuous postcibal gastroesophageal reflux, large hiatal hernias and frequently required an antireflux operation. A functional motility disorder suggesting delayed gastric emptying appeared to be important in infants with discontinuous reflux (type II pattern). These infants had frequent gastroesophageal reflux for only 2 3/4 hours postcibally, antral-pylorospasm, increased low esophageal sphincter pressures, and a high incidence of pulmonary symptoms and non-specific watery diarrhea. The mixed (type III) pattern of gastroesophageal reflux occurred in a small number of infants and exhibited features of both type I and II patterns.

Child, Preschool↗

PubMed1978

Mechanics of the human diaphragm during voluntary contraction: dynamics.

We determined the static, isometric relationship between diaphragmatic EMG (Edi) and transdiaphragmatic pressure (Pdi) in man at specified abdominothoracic configurations, assessed with magnetometers. During inspiratory airflow, measurements of Edi and Pdi were taken as the respiratory system passed through the same configuration as obtained during the static isometric contractions, allowing a comparison of static and dynamic contractions of the diaphragm at a given length and curvature. When voluntary inspiratory maneuvers are performed with no associated outward displacement of the abdominal wall, or with slight inward displacement, the Pdi developed dynamically is the same as that developed statically at a given Edi. When outward movement of the abdominal wall occurs during inspiratory airflow, the Pdi developed dynamically depends on the rate of abdominal displacement, not on overall inspiratory airflow rate. We conclude that the velocity of shortening of the diaphragm increases directly as the rate of abdominal displacement. We construct a pressure-flow analogue of the force-velocity relationship for the diaphragm and discuss the functional implications of these observations in relation to spontaneous breathing.

Adult↗

PubMed1990

Respiratory changes in diaphragmatic intramuscular pressure.

We attempted to measure diaphragmatic tension by measuring changes in diaphragmatic intramuscular pressure (Pim) in the costal and crural parts of the diaphragm in 10 supine anesthetized dogs with Gaeltec 12 CT minitransducers. During phrenic nerve stimulation or direct stimulation of the costal and crural parts of the diaphragm in an animal with the chest and abdomen open, Pim invariably increased and a linear relationship between Pim and the force exerted on the central tendon was found (r greater than or equal to 0.93). During quiet inspiration Pim in general decreased in the costal part (-3.9 +/- 3.3 cmH2O), whereas it either increased or slightly decreased in the crural part (+3.3 +/- 9.4 cmH2O, P less than 0.05). Similar differences were obtained during loaded and occluded inspiration. After bilateral phrenicotomy Pim invariably decreased during inspiration in both parts (costal -4.3 +/- 6.4 cmH2O, crural -3.1 +/- 0.6 cmH2O). Contrary to the expected changes in tension in the muscle, but in conformity with the pressure applied to the muscle, Pim invariably increased during passive inflation from functional residual capacity to total lung capacity (costal +30 +/- 23 cmH2O, crural +18 +/- 18 cmH2O). Similarly, during passive deflation from functional residual capacity to residual volume, Pim invariably decreased (costal -12 +/- 19 cmH2O, crural -12 +/- 14 cmH2O). In two experiments similar observations were made with saline-filled catheters. We conclude that although Pim increases during contraction as in other muscles, Pim during respiratory maneuvers is primarily determined by the pleural and abdominal pressures applied to the muscle rather than by the tension developed by it.

Animals↗

PubMed2005

Enzyme replacement therapy in classical infantile pompe disease: results of a ten-month follow-up study.

Infantile Pompe disease (IPD) is a fatal, autosomal recessive muscle-wasting disorder. Due to a deficiency of the lysosomal enzyme acid alpha-glucosidase patients develop a generalized myopathy, diaphragmatic weakness, and cardiomyopathy leading to death usually within the first year of life. So far there is no therapy available. We report on the safety and efficacy of transgenically derived recombinant human precursor acid alpha-glucosidase (rhGAA) in a 10-month follow-up study in two children with IPD who previously completed a 48-week course of enzyme replacement therapy (ERT) with the same medication at the same dose in a phase II clinical trial. Under this therapy cardiac status and muscle strength had improved, leading to survival beyond the age of one year. These results, together with data from two other phase II clinical trials encouraged further evaluation of the long-term safety and efficacy of enzyme replacement therapy in patients with infantile-onset Pompe disease. During the 10-month follow-up period, ERT was well-tolerated and neither patient experienced a single infusion-associated reaction. The initial improvements in cardiac size and function, as measured by left ventricular mass index and the fractional shortening, were maintained in both patients, and a continued improvement of motor function, as measured by the Alberta infant motor scale, was observed.

Adolescent↗

PubMed2005

Cardiovascular issues in respiratory care.

The hemodynamic effects of ventilation are complex but can be grouped under four clinically relevant concepts. First, spontaneous ventilation is exercise, and critically ill patients may not withstand the increased work of breathing. Initiation of mechanical ventilatory support will improve oxygen delivery to the remainder of the body by decreasing oxygen consumption. To the extent that mixed venous oxygen also increases, Pao(2) will increase without any improvement in gas exchange. Similarly, weaning from mechanical ventilatory support is a cardiovascular stress test. Patients who fail to wean also manifest cardiovascular insufficiency during the failed weaning attempts. Improving cardiovascular reserve or supplementing support with inotropic therapy may allow patients to wean from mechanical ventilation. Second, changes in lung volume alter autonomic tone and pulmonary vascular resistance (PVR), and at high lung volumes compress the heart in the cardiac fossa. Hyperinflation increases PVR and pulmonary artery pressure, impeding right ventricular ejection. Decreases in lung volume induce alveolar collapse and hypoxia, stimulating an increased pulmonary vasomotor tone by the process of hypoxic pulmonary vasoconstriction. Recruitment maneuvers, positive end-expiratory pressure, and continuous positive airway pressure may reverse hypoxic pulmonary vasoconstriction and reduce pulmonary artery pressure. Third, spontaneous inspiration and spontaneous inspiratory efforts decrease intrathoracic pressure (ITP). Since diaphragmatic descent increases intra-abdominal pressure, these combined effects cause right atrial pressure inside the thorax to decrease but venous pressure in the abdomen to increase, markedly increasing the pressure gradient for systemic venous return. Furthermore, the greater the decrease in ITP, the greater the increase in left ventricular (LV) afterload for a constant arterial pressure. Mechanical ventilation, by abolishing the negative swings in ITP, will selectively decrease LV afterload, as long as the increases in lung volume and ITP are small. Finally, positive-pressure ventilation increases ITP. Since diaphragmatic descent increases intra-abdominal pressure, the decrease in the pressure gradient for venous return is less than would otherwise occur if the only change were an increase in right atrial pressure. However, in hypovolemic states, positive-pressure ventilation can induce profound decreases in venous return. Increases in ITP decrease LV afterload and will augment LV ejection. In patients with hypervolemic heart failure, this afterload reducing effect can result in improved LV ejection, increased cardiac output, and reduced myocardial oxygen demand.

Blood Pressure↗

PubMed1996

[Effects of pulmonary rehabilitation in patients with chronic respiratory failure].

To evaluate the effects of pulmonary rehabilitation in patients with chronic respiratory failure, 43 patients with stable chronic respiratory failure were enrolled in a pulmonary rehabilitation program. The program included education, instruction in diaphragmatic breathing, respiratory muscle training, and exercise training (walking and riding a stationary bicycle). Patients were divided into 2 groups by the lowest SpO2 during a 12-minute-walk test done before rehabilitation: lowest SpO2 < 90% (Group A, 32 patients) and lowest SpO2 > or = 90% (Group B, 11 patients). In group A, SpO2 during exercise training was maintained over 90% by O2 inhalation, by load reduction, or by maintaining a slower walking speed. During 2 months of rehabilitation, the distance walked in 12 minutes and the maximum distance walked with an SpO2 > or = 90% significantly increased in both groups, but PaO2, VC, and FEV1 increased only in group A. In group A, the patients with chronic obstructive pulmonary disease had significant increases in PaO2, VC, and FEV1, but those with old tuberculosis sequelae had significant increases in PaO2 only. Pulmonary rehabilitation in patients with chronic respiratory failure may not only increase exercise tolerance but may also improve arterial oxygenation and pulmonary function.

Aged↗

PubMed2001

Left ventricular remodeling and mechanics after successful repair of aortic coarctation.

Forty normotensive patients (mean age 12.3 +/- 6.5 years) followed up after a successful repair of aortic coarctation (mean age at coarctectomy 5.1 +/- 4.8 yrs) were studied by echo-Doppler to (1) evaluate left ventricular (LV) remodeling and endocardial and midwall mechanics, and (2) identify factors that might predispose to persistent abnormalities. Sex- and age-specific cutoff levels for LV mass/height2.7 and relative wall thickness were defined to assess LV geometry. To adjust for age-and growth-related changes in ventricular mechanics, all echocardiographic variables were expressed as a Z-score relative to the normal distribution. In addition, the smallest diameter of the aorta was assessed by magnetic resonance imaging and calculated as percent narrowing compared with the diameter of the aorta at the diaphragmatic level. In the study group, 24 of 40 patients (60%) had normal LV geometry. Among the 16 patients (40%) with abnormal LV geometry, 5 (12.5%) had a pattern of concentric remodeling and 11 (27.5%) an eccentric hypertrophy. LV hypertrophy was marked (LV mass index >51 g/m2.7) in 5 of these patients. No patient had a pattern of concentric hypertrophy. LV contractility was increased (Z-score >95th percentile) in 28 patients (70%) as assessed using the endocardial stress-velocity index. In contrast, LV contractility assessed using midwall stress-velocity index remained elevated (Z-score >95th percentile) in 15 patients (37.5%). The stepwise multiple logistic regression analysis was not able to detect any significant independent predictor of abnormal LV remodeling, including sex, age at surgical repair, length of postoperative follow-up, heart rate, body mass index, systolic and diastolic blood pressure, and smallest diameter of the aorta, as well as indexes of LV geometry (shape, mass, volume, mass/ volume ratio) and function (preload, afterload, pump function, and myocardial contractility). Thus, normotensive patients after surgical repair of aortic coarctation may be in an LV hyperdynamic cardiovascular state (more frequent in those who have undergone late repair) and have multiple patterns of LV geometry.

Adolescent↗

PubMed1991

[Respiratory patterns induced by bent posture in COPD patients].

Three body positions were studied in order to determine their influence on the respiratory pattern in 7 subjects with chronic airflow obstruction. The positions were sitting lying back (AR), sitting with the trunk leaning forwards (AP) and standing with the trunk leaning forwards (DP). Compared to sitting lying back, sitting in the forward position favoured diaphragmatic improvement and improved the length/tension relationship of the diaphragmatic fibres and of its mechanical coupling with the thoracic cage; as a result the diaphragm took a more important part in the overall inspiratory effort thus relieving the thoracic inspiratory muscular effort. In relation to AR, the standing, leaning forward (DP) increased the end expiratory level and gave rise to the development of active expiration. This change in the usual respiratory manner enables the diaphragm to benefit on inspiration from the help bought by the restoration of the potential energy stored up in the respiratory system during the course of expiration.

Evaluation Studies as Topic↗

PubMed1979

Ectopic atrial tachycardia on swallowing. Report on favourable effect of verapamil.

A female patient who suffered from atrial tachycardia associated with the ingestion of food or drink was examined in our department. No signs of organic heart disease were discovered, oesophageal motility was normal, but X-ray revealed a small hiatal hernia. The arrhythmia started with an atrial extrasystole arising well outside the functional refractory period of the AV node, and it could be reproduced by inflation of a balloon. It is suggested that the arrhythmia is induced by a mechanical effect of the passage of food on the left atrial wall. Several drugs were tried in order to stop or relieve the complaints. None of them prevented or stopped the atrial tachycardia but verapamil and edrophonium chloride caused 2:1 AV block, and follow-up study has shown that sufficient doses of verapamil are able to relieve the patient's complaints.

Atrioventricular Node↗

PubMed2000

Specific subnuclei of the nucleus tractus solitarius play a role in determining the duration of inspiration in the rat.

Our previous data obtained in the cat suggest that the neurons of the ventrolateral subnucleus of the tractus solitarius (vlNTS) act as an inspiratory off-switch and terminate the inspiratory phase of the respiratory cycle (Berger et al., Eur. J. Pharmacol. 277 (1995) 195-208; Gillis et al., Neurosci. Abstr. 23 (1997) 725). The purpose of the present study was to determine whether inhibition of the region of the vlNTS of the rat using drugs that hyperpolarize, disfacilitate or block both axonal conduction and action potential generation would alter the inspiratory phase of the respiratory cycle. Experiments were conducted in anesthetized, vagotomized and spontaneously breathing rats while monitoring diaphragmatic electromyogram activity. Vagus nerves were sectioned in order to rule out prolongation of inspiration evoked by microinjection of agents into the vlNTS which block excitatory drive from lung afferent inputs. Bilateral microinjection of the inhibitory amino acid gamma-aminobutyric acid (GABA) 25 nmol/45 nl produced an immediate prolongation of inspiratory duration (484+/-18 to 1291+/-84 ms) and an apneustic pattern of breathing. Other effects observed were a significant shortening of expiratory duration (778+/-36 to 432+/-38 ms), rise in blood pressure (83+/-4 to 108+/-6 mmHg) and a small but significant increase in heart rate (439+/-17 to 452+/-18 beats/min). Bilateral microinjection of the ionotropic glutamate receptor antagonist kynurenic acid (1 nmol) and the Na(+) channel blocker tetrodotoxin (10 pmol) into the region of the vlNTS consistently produced a similar prolongation of inspiratory duration and an apneustic pattern of breathing. These results support the hypothesis that neurons in the region of the vlNTS promote the transition from inspiration to expiration and function as part of the 'Inspiratory Off Switch'.

Action Potentials↗

PubMed1981

Clinical hemodynamic and angiographic findings in 94 patients with old myocardial infarction. Comparison with 79 patients with coronary artery disease and no myocardial infarction.

Clinical, hemodynamic, coronary arteriographic, and ventriculographic findings of 94 patients (pts) with coronary artery disease (CAD) and old myocardial infarction (MI) have been described and compared with those of 70 pts with CAD and no previous MI. Pts with old MI presented a more compromised functional and hemodynamic status, with a higher incidence of NYHA class III-IV pts (40%), symptoms of left ventricular (LV) failure (31%), cardiomegaly (70%), higher left ventricular end-diastolic pressure (LVEDP) (19.6 +/- 9.6 mmHg, p less than 0.05), compared with 32%, 22%, 54% and 16.0 +/- 6.8 mmHg respectively in CAD pts with no MI. MI pts presented more severe CAD, higher incidences of three vessel disease (56%, p less than .005) and of left anterior descending (LAD) (34%) and right coronary artery (RCA) (36%) occlusions, compared with 34%, 6%, and 9% respectively in pts with no MI. Furthermore, pts with old MI showed more diffused and severe LV segmental wall contraction abnormalities, with higher frequencies of LV aneurysm (31%) and of pts with asynergy of more than 2 LV segments (26%), compared with 1% and 3% respectively in pts with no MI. Within the group with old MI, LVEDP was higher in pts with anterior (A) (22.0 +/- 11 mmHg, p less than .02) and anterior ł diaphragmatic (AłD) (21.5+/- 7.9 mmHg, p less than .05) MI, compared with pts with diaphragmatic (D) MI (16.6 +/- 7.1 mmHg); furthermore, LVEDP increase was significantly correlated with the severity and the extent of LV asynergy. In A and D MI, LAD and RCA stenoses or occlusions were prevalent respectively; pts with AłD MI showed larger numbers of coronary stenosis (3.05) and occlusions (1.05) per patient. The coronary artery supplying the infarcted area showed stenosis (greater than 75%) in 95.6% and was normal in 2.2% of cases. Thus, pts with CAD and old MI, and particularly of AłD and A MI, show a more compromised hemodynamic status and more severe degrees of CAD and of LV segmental wall contraction abnormality, which are responsible for their poor prognosis, compared to pts with CAD but no old MI.

Adult↗

PubMed2002

Contribution of respiratory acidosis to diaphragmatic fatigue at exercise.

The factors that may modulate ventilatory muscle fatigue during exercise are controversial. In this study the contribution of acidosis to exercise-induced diaphragmatic fatigue was investigated, using measurements of the twitch mouth pressure response (tw,Pmo) to cervical magnetic stimulation. After learning sessions, 14 healthy subjects performed two cycling tests (at 60% of maximal aerobic power for 16 min), one while breathing spontaneously (mean minute ventilation (V'E) 67.9 L x min(-1)) and the other while hypoventilating voluntarily (mean V'E 53.8 L x min(-1)). Exercise was voluntarily set at a moderate power to avoid a fatiguing effect of exercise per se. As compared with spontaneous breathing (SB), voluntary hypoventilation (VHV) significantly increased mean carbon dioxide tension in arterial blood (Pa,CO2) (51 mmHg versus 41 mmHg) and significantly decreased arterial pH (7.28 versus 7.34). After 10 min of SB test, tw,Pmo was unchanged compared to the baseline value (19.1 versus 18.5 cmH2O) whereas tw,Pmo fell significantly as compared to baseline (17.1 versus 18.5 cmH2O) and to SB (17.1 versus 19.1 cmH2O) after the VHV test. The results of this study suggest that exposure to hypercapnia may impair respiratory muscle function. This impairment could be more clinically relevant in patients with chronic obstructive lung disease.

Acidosis, Respiratory↗