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At least 793 records · Page 44Linked to original sources
PubMed1989

Diaphragmatic electromyography using a multiple electrode array.

We have developed a new technique for diaphragmatic electromyography using an array of seven sequential electrode pairs at 1.0-cm spacing on an esophageal catheter. This array provides information about the spatial distribution of the electrical field generated by the diaphragm and reveals a sharply peaked variation of electrical potential with distance along the esophagus. The rectified and integrated information from each of the seven pairs is summed to give an approximation to the total electrical activity over the span of the array, providing a signal that is relatively insensitive to the position of the array over approximately 4 cm of catheter movement and removes the requirement for balloon stabilization of the catheter. With our array, we have confirmed the artifact in the evoked compound muscle action potential that seems to be related to diaphragmatic shape as reported by others who used supramaximal phrenic nerve stimulation, but the magnitude of this artifact (compared with the functional residual capacity level) was modest near functional residual capacity, averaging 12 +/- 14% (SD) for lung volumes 1.0 l above and -4 +/- 15% for lung volumes 1.0 l below functional residual capacity along the rib cage-abdomen relaxation line.

Action Potentials↗
PubMed1997

Effects of transverse fiber stiffness and central tendon on displacement and shape of a simple diaphragm model.

Our previous experimental results (A. M. Boriek, S. Lui, and J. R. Rodarte. J. Appl. Physiol. 75: 527-533, 1993 and A. M. Boriek, T. A. Wilson, and J. R. Rodarte. J. Appl. Physiol. 76: 223-229, 1994) showed that 1) costal diaphragm shape is similar at functional residual capacity and end inspiration regardless of whether the diaphragm muscle shortens actively (increased tension) or passively (decreased tension); 2) diaphragmatic muscle length changes minimally in the direction transverse to the muscle fibers, suggesting the diaphragm may be inextensible in that direction; and 3) the central tendon is not stretched by physiological stresses. A two-dimensional orthotropic material has two different stiffnesses in orthogonal directions. In the plane tangent to the muscle surface, these directions are along the fibers and transverse to the fibers. We wondered whether orthotropic material properties in the muscular region of the diaphragm and inextensibility of the central tendon might contribute to the constancy of diaphragm shape. Therefore, in the present study, we examined the effects of stiffness transverse to muscle fibers and inextensibility of the central tendon on diaphragmatic displacement and shape. Finite element hemispherical models of the diaphragm were developed by using pressurized isotropic and orthotropic membranes with a wide range of stiffness ratios. We also tested heterogeneous models, in which the muscle sheet was an orthotropic material, having transverse fiber stiffness greater than that along the fibers, with the central tendon being an inextensible isotropic cap. These models revealed that increased transverse stiffness limits the shape change of the diaphragm. Furthermore, an inextensible cap simulating the central tendon dramatically limits the change in shape as well as the membrane displacement in response to pressure. These findings provide a plausible mechanism by which the diaphragm maintains similar shapes despite different physiological loads. This study suggests that changes of diaphragm shape are restricted because the central tendon is essentially inextensible and stiffness in the direction transverse to the muscle fibers is greater than stiffness along the fibers.

Animals↗
PubMed1996

The normal pulmonary vascular transition at birth.

Although the normal pulmonary vascular transition at birth takes place quickly in the delivery room, it has its basis in the complex structural and biochemical development of the lung. We are only beginning to understand the stimuli that initiate and mediate the transition, as well as their interrelationships. Comprehension of normal structure and function is the foundation that will enable us to understand how this process is impaired in the baby born with congenital diaphragmatic hernia.

Hernias, Diaphragmatic, Congenital↗
PubMed1988

Characteristics and functional significance of canine abdominal muscles.

To assess the characteristics and function of the muscles of the anterolateral abdominal wall, we have examined the isometric contractile properties of bundles of canine rectus abdominis (RA) and external oblique (EO) muscles. In addition, we have related the lengths of these muscles measured sonometrically in vivo at supine functional residual capacity (FRC) to in vitro optimal force-producing length (Lo). We also investigated the action of the abdominal muscles on the displacement of costal and crural diaphragm. We found that 1) contraction time of RA was longer and that the RA developed greater force than the EO at submaximal stimulation frequencies; 2) maximal tetanic force and the active length-tension curves were similar in both abdominal muscles; 3) on passive stretch, the compliance of the RA was one-third that of the EO; 4) at supine FRC, the EO is operating at 83% of Lo, whereas the RA is operating at 105% of Lo; 5) stimulation of either RA or EO (abdominal pressure of 15 cmH2O) lengthened the costal and crural diaphragm toward their Lo values, with greater crural excursion occurring than costal. We conclude that the RA is well suited for restraining the abdominal viscera in prone quadrupeds, whereas the EO is better designed to assist expiration. Stimulation of both muscles improves in situ diaphragmatic operating length.

Abdominal Muscles↗
PubMed2006

Congenital intrathoracic kidney with right Bochdalek defect.

Intrathoracic kidney is a rare congenital anomaly. Since most reported cases are asymptomatic, it is extremely rare for this ectopia to be diagnosed in the neonatal period. We report a male infant with right intrathoracic kidney associated with Bochdalek defect. Chest X-ray demonstrated a right posterior mediastinal mass and intestinal gas in the right lung field. Contrast-enhanced CT and intravenous urography led to a diagnosis of intrathoracic kidney. Due to the presence of Bochdalek defect, the intrathoracic kidney was reduced into the abdominal cavity at the time of diaphragmatic repair. The intrathoracic kidney with attached adrenal gland was located at the level of the carina and was covered with protruded retroperitoneum. The kidney was thought to have been pushed this high by the small intestine and left lobe of the liver, which had also herniated through the defect. Postoperative hemodynamics and renal function were normal.

Adult↗
PubMed1993

Reflex control of diaphragm activation by thoracic afferents.

Recent studies suggest that chest wall reflexes may have a role in modulating diaphragm activation. The purpose of this study was to more closely examine this issue by assessing the diaphragmatic motor response to airway occlusion. Studies were performed in vagotomized mongrel dogs anesthetized with pentobarbital sodium. Diaphragmatic electromyogram (EMG) and phrenic neurogram (ENG) responses to airway occlusion were evaluated at different precontractile respiratory muscle lengths, achieved by passive inflation and deflation with a volume syringe during the preceding expiration. Lung volume was expressed as the corresponding change in airway pressure. At functional residual capacity, deflation (-5 cmH2O), and large inflation (+25 cmH2O), phrenic ENG during occlusion was 90 +/- 2 (SE), 84 +/- 5, and 86 +/- 3% of the preceding control breaths, respectively (n = 9). Qualitatively similar, but somewhat more pronounced, responses were observed on diaphragmatic EMG. With small lung inflations, the degree of reduction of phrenic ENG with airway occlusion was less. Consequently, the relationship between airway pressure and degree of inhibition was best described as a reverse parabola with the maximum at approximately +10-15 cmH2O. Responses were not significantly affected by bilateral cervical phrenicotomy. Complete section of the spinal cord at the high thoracic level (T1-T2) abolished the observed reduction in phrenic ENG in response to airway occlusion. Our results demonstrate 1) the existence of nonvagal nonphrenic reflex control of diaphragm activation most likely secondary to activation of intercostal afferents and 2) that the magnitude of this reflex is highly dependent on factors related to lung volume.

Airway Obstruction↗
PubMed2002

Effects of mechanical ventilation on diaphragm function and biology.

The pathophysiological mechanisms of weaning from mechanical ventilation are not fully known, but there is accumulating evidence that mechanical ventilation induces inspiratory muscle dysfunction. Recently, several animal models have provided potential mechanisms for mechanical ventilation-induced effects on muscle function. In patients, weaning difficulties are associated with inspiratory muscle weakness and reduced endurance capacity. Animal studies demonstrated that diaphragm force was already decreased after 12 h of controlled mechanical ventilation and this worsened with time spent on the ventilator. Diaphragmatic myofibril damage observed after 3-days controlled mechanical ventilation was inversely correlated with maximal diaphragmatic force. Downregulation of the diaphragm insulin-like growth factor-I and MyoD/myogenin messenger ribonucleic acid occurred after 24 h and diaphragmatic oxidative stress and increased protease activity after 18 h. In keeping with these findings, diaphragm fibre atrophy was shown after 12 h and reduced diaphragm mass was reported after 48 h of controlled mechanical ventilation. These animal studies show that early alterations in diaphragm function develop after short-term mechanical ventilation. These alterations may contribute to the difficulties in weaning from mechanical ventilation seen in patients. Strategies to preserve respiratory muscle mass and function during mechanical ventilation should be developed. These may include: adaptation of medication, training of the diaphragm, stabilisation of the catabolic state and pharmacotherapy.

Animals↗
PubMed1986

Pulmonary function in chronic renal failure patients managed by continuous ambulatory peritoneal dialysis.

The influence of intraperitoneal fluid on pulmonary function was studied in 20 unselected continuous ambulatory peritoneal dialysis (CAPD) patients, all but one of whom had at least one cardiorespiratory disorder. Measurements of pulmonary function were made with the abdomen empty and following the instillation of 2 1 of dialysis fluid (full). Functional residual capacity fell with the peritoneal cavity full, due to decreases in residual volume, and expiratory reserve volume, but there was a corresponding increase in inspiratory capacity. The vital capacity remained unchanged and the total lung capacity fell only slightly. The FEV1, diffusing capacity, and distribution of ventilation were unaltered. These findings can be attributed to an increase in intra-abdominal pressure resulting in elevation of the diaphragm and increased diaphragmatic contractility. We conclude that the instillation of 21 of dialysis fluid in CAPD patients with cardiorespiratory disease does not result in a clinically significant deterioration in these aspects of pulmonary function.

Adult↗
PubMed2006

Vitamin A improves Pax3 expression that is decreased in the heart of rats with experimental diaphragmatic hernia.

BACKGROUND/AIMS: Rats with nitrofen-induced congenital diaphragmatic hernia (CDH) have hypoplasia and malformations of the heart. The mechanism of action of nitrofen involves changes in neural crest signaling. Pax3 function is required for cardiac neural crest cells to complete their migration to the developing heart. Vitamin A improves heart hypoplasia. The aims of this study were to examine whether Pax3 expression is decreased in the heart of E13 E15 and E21 rats exposed to nitrofen and if vitamin A reverts this effect. MATERIAL AND METHODS: Pregnant rats received either 100 mg nitrofen or olive oil on E9.5. Each group was divided into 2 subgroups according to the subsequent treatment with intragastric vitamin A (15000 IU) or vehicle on E10.5 to E11.5. The pups were recovered on E13, E15 and E21 and the hearts were dissected out. Pax3 mRNA expression was determined by quantitative real time PCR. Comparisons among groups were made with ANOVA and Bonferroni post hoc tests with a threshold of significance of P < .05. RESULTS: Pax3 mRNA expression was significantly decreased on E13 and E15 in the hearts of nitrofen-treated embryos and it remained decreased although not significantly on E21. Vitamin A recovered this expression on E13, partially on E15 and above normal levels on E21. CONCLUSIONS: Pax3 is underexpressed in the hearts of nitrofen exposed embryonal rats on days 13th and 15th of gestation and tends to be lower than normal near term. Vitamin A up-regulates this expression on the 3 end points. The mechanism of action of Pax3 should be further investigated because it could be one of the targets for future prenatal transplacental intervention.

Animals↗
PubMed1996

Diaphragmatic hernia and associated anemia: response to surgical treatment.

From 1985 to 1993, 49 patients (35 women and 14 men) with diaphragmatic hernia and associated anemia underwent surgical repair. The median age was 64.5 years (range 24 to 84 years). Hematologic and gastroenterologic evaluations revealed no other potential cause of bleeding. Each patient had a diaphragmatic hernia. The median time between the diagnosis of anemia and surgical repair was 36 months (range 1 to 334 months). Forty-five patients (91.8%) had received replacement therapy, including iron for 43 and blood transfusions for 32 (median 6 units; range 2 to 70 units). Forty-six patients (93.9%) had symptoms: heartburn in 28, early satiety with bloating in 19, regurgitation in 11, dysphagia in 7, and aspiration in 4. Preoperative upper gastrointestinal endoscopic evaluation demonstrated gastric erosions at the level of the hiatus in 22 patients (44.9%), esophagitis in 7, stenosis in 1, and Barrett's disease in 1. An uncut Collis-Nissen fundoplication was performed in 44 patients, Belsey fundoplication in 2, a cut Collis-Nissen fundoplication, Nissen fundoplication, and Hill repair in 1 each. There was one operative death (2% mortality). Complications occurred in 18 patients (36.7%). Follow-up was complete and ranged from 4 to 103 months (median 63 months). Forty-five patients (91.8%) had resolution of their anemia. Functional results were excellent in 40 patients (81.6%), good in 2 (4.1%), fair in 4 (8.2%), and poor in 3 (6.1%). In most patients with diaphragmatic hernia and associated anemia refractory to medical treatment, surgical repair can result in successful resolution of the anemia.

Adult↗
PubMed1999

Functional and mechanical sequelae of colon interposition for benign oesophageal disease.

OBJECTIVE: In an attempt to estimate the incidence and severity of the functional and mechanical problems associated with colon interposition for benign oesophageal disease, a retrospective analysis of a single centre experience was undertaken. METHODS: Between 1961 and 1990, a total of 365 patients who survived the postoperative stay in hospital were followed up over 7-38 years and form the basis for this study. Upper gastro intestinal symptoms in these patients were investigated clinically, radiologically, endoscopically and in the oesophageal laboratory. Mechanical and functional abnormalities requiring surgical intervention for relief of symptoms were documented. RESULTS: There were two late presentations of colo bronchial fistulae, two instances of persistent colo cutaneous fistulae, three cases of diaphragmatic herniation and two adenocarcinomata of the colo gastric junction in the patients with short segment colon interposition. Amongst the long segment colon interposition patients there was one hiatal obstruction, two thoracic inlet delays associated with pseudo diverticulosis and one hiatal obstruction. One other patient presented with an adenocarcinoma of the intrathoracic colon. There were four patients requiring revision of the cervical oesophago colic anastomosis, two of them on recurrent occasions. The remaining sequelae were functional and were associated with increasing redundancy of the colonic segments at different levels. There were 17 such patients, two of whom developed significant redundancy at two different levels. CONCLUSIONS: Although the patients with short segment colon interposition developed predominantly avoidable iatrogenic complications, those undergoing long segment colon interposition developed functional sequelae requiring re-operations in later life.

Adult↗
PubMed1991

A laryngeal pacemaker for inspiration-controlled, direct electrical stimulation of the denervated posterior cricoarytenoid muscle in sheep.

Bilateral recurrent nerve palsies were induced in four sheep and unilateral nerve palsy in one sheep. Vocal cord abductions were achieved by direct electrical stimulation of the posterior cricoarytenoid muscles (PCMs). By means of the diaphragmatic myogram, respiratory synchronous activation of the glottis opening musculature was shown possible. In all cases an adequate glottis opening for respiratory function was achieved during a maximum period of stimulation of 5-8 h in each animal. Abductor movements of the vocal cords were documented with video laryngoscopy. Using digital image processing, the areas of the open glottis were measured at rest and during bilateral direct electrical stimulation of the PCMs.

Animals↗
PubMed1998

Radiographic assessment of atrial dipole position in single pass lead VDD and DDD pacing. The Multicenter Study Group.

Atrial electrode position was determined by radiographic analysis in 160 patients paced in single-lead VDD for second- or third-degree A-V block, implanted > 1 year with Phymos single pass leads and Phymos 3D pacemakers. The packing lead features an atrial dipole with a 30-mm electrode interspace. In 44% of patients, the upper atrial electrode was positioned within a band of 20 mm centered at the level of the superior vena caval insertion (junctional area) and was in the inferior vena cava or in the atrium in 35% and 21% of cases, respectively. In spite of these different dipole locations, all patients had stable atrium-driven pacing at routine follow-up visits. With the electrode in the junctional area, unipolar stimulation of up to 5 V for 1 ms resulted in stable atrial capture in 63% and 59% of the patients in supine and upright positions, respectively. With the electrode in the atrium, corresponding success rates were 45% and 54%. In the atrium, however, the prevalence of diaphragmatic stimulation was significantly lower than at the junction (10% vs 42% in supine position; 21% vs 47% upright). Though atrial sensing function proved adequate in a wide range of positions, these results suggest that the Phymos lead atrial dipole should be positioned within the atrium, as close as possible to the atrial wall, to maximize the number of VDD patients who might benefit from single-lead DDD pacing.

Cardiac Pacing, Artificial↗
PubMed1977

Respiratory arrest--a fatal complication of myelography.

Respiratory arrest occurred in a patient undergoing cervical myelography in the Trendelenberg position. Autopsy revealed infiltration of the phrenic nerves by metastatic breast cancer resulting in diaphragmatic paralysis. Though this is a very rare complication of myelography, it is suggested that more attention be paid to the respiratory function of patients with neurological conditions prior to myelography.

Female↗