PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Diaphragmatic function”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1979

Immersion vs pressure-breathing and diaphragmatic function in the upright position.

In seven anesthetized dogs, immersion in the upright position to mid-neck level (IM) was compared to pressure breathing (PB) under dry conditions during constant-stimulus diaphragmatic contraction (EPS). The comparison was in terms of EPS-induced changes in alveolar pressure under static condition (Pmus); EPS-induced tidal volume (VT); and the VT/Pmus ratio (C'). It was found that at iso-lung volume (V): (a) Pmus was greater in IM than in PB, the difference increased at higher V; (b) VT was greater in IM than in PB, but the VT difference (deltaVT) did not parallel that in Pmus; VT was maximum at a V equal to approximately 90% of FRC in air (FRCd) and decreased below and above this volume; (c) during both IM and PB, the VT-V relationship reflected a biphasic relationship of C' to V and appeared to be inherent to the upright position.

Animals↗
PubMed1987

Effects of upper or lower abdominal surgery on diaphragmatic function.

Changes in abdominal (delta AB) and rib cage (delta RC) movements, and in vital capacity, were compared between 23 patients undergoing upper or lower abdominal surgery at 1, 3 and 7 days after surgery. Diaphragmatic index was obtained by measuring the relative abdominal motion (delta AB/delta AB + delta RC) using magnetometers. Electrical activity of abdominal muscles was assessed using needle electrodes after upper abdominal surgery in four additional patients. After upper abdominal surgery, the vital capacity and the diaphragmatic index were markedly reduced for 1 week. No abdominal muscle activity was observed at day 1. After lower abdominal surgery, the vital capacity returned to the normal range within 3 days of operation, without any diaphragmatic impairment. These findings substantiate the role of diaphragmatic dysfunction in postoperative reduction in vital capacity observed after upper abdominal surgery.

Abdomen↗
PubMed1992

Effect of inspiratory resistive loaded breathing and hypoxemia on diaphragmatic function in the piglet.

The combined effects of inspiratory resistive loaded breathing (IRL) and hypoxemia on transdiaphragmatic pressure (Pdi) in nine 1-mo-old Yorkshire piglets were studied. IRL was adjusted to increase spontaneously generated Pdi five to six times above baseline but maintain arterial PCO2 < 70 Torr to prevent hypercapnic depression of diaphragmatic contractility. Measurements of ventilation, blood gases and pH, Pdi, diaphragmatic electromyogram, Pdi during phrenic nerve stimulation, diaphragmatic blood flow, and end-expiratory lung volume were obtained at baseline, after 2 h of IRL, and then after 1 h of hypoxemia (arterial PO2 approximately 40 Torr) combined with IRL. Diaphragmatic muscle samples were obtained after study completion and immediately frozen in liquid nitrogen for determination of tissue ATP, phosphocreatine, lactate, and glycogen levels. Ten 1-mo-old piglets were subjected to IRL alone and served as controls. IRL alone resulted in significant impairment of Pdi generation. The addition of hypoxemia for 1 h did not further compromise Pdi in comparison to control animals who were subjected to IRL alone. Blood flow to both the costal and crural segments of the diaphragm increased significantly during IRL; the addition of the hypoxemic stress resulted in further significant augmentation of blood flow to both segments of the diaphragm. No differences were noted in diaphragmatic muscle tissue ATP, phosphocreatine, or glycogen between control and IRL animals or between control and IRL plus hypoxemia animals. Muscle lactate levels increased significantly in the IRL plus hypoxemia animals only. The data from this study suggest that moderate hypoxemia during resistive-loaded breathing in the piglet does not accentuate diaphragmatic fatigue.

Animals↗
PubMed1985

Diaphragmatic function following cervical cord injury: neurally mediated improvement.

Vital capacity measurements from 36 people rendered quadriplegic by traumatic cervical cord injuries generally increased during the first ten months after injury, indicating spontaneous improvement in respiratory muscle function. Reasoning that a renewal of neural supply to the diaphragm would probably be accompanied by a parallel renewal of neural supply to other muscles having adjacent motor pathways, the present study compared vital capacity measurements with concomitant muscle function evaluations from 20 of these people. Qualitatively, increases in vital capacity were invariably accompanied by increases in the function of a group of muscles (primarily of the shoulder and upper arm) having some segmental innervation in common with the diaphragm (C3-C5) but were only sometimes accompanied by increases in the function of a group of muscles (primarily of the forearm and wrist) having segmental innervation below that of the diaphragm (C6-C8). These findings suggest that the spontaneous improvement in vital capacity observed in quadriplegic people is mediated in part by corresponding improvement in the neural supply to the diaphragm. Quantitatively, however, linear regression analysis indicated that neither the rate nor the absolute amount of improvement in vital capacity could be predicted with any reliability from pulmonary function tests, neurologic examinations, or muscle function evaluations performed in the early stage of recovery.

Adolescent↗
PubMed1992

Effect of fatigue on diaphragmatic function at different lung volumes.

The transdiaphragmatic pressure twitches (PdiT) in response to single maximal shocks delivered bilaterally to the phrenic nerves were recorded as a function of lung volume when the diaphragm was fresh and when fatigued. All relationships were linear and negatively sloped (all r greater than 0.85). From these relationships PdiT was found to decrease with fatigue more rapidly and to recover more quickly at high than at low lung volumes. Complete recovery of PdiT at all lung volumes was greater than 1 h. Contraction and relaxation rate constants of PdiT did not change significantly with fatigue. We conclude that fatigue affects diaphragm contractility more at high than at low lung volumes and that changes in diaphragm contractility are best reflected in the measurement of PdiT as a function of lung volume.

Adult↗
PubMed1985

Effect of theophylline on respiratory muscle function.

Theophylline improves diaphragmatic contractility of the respiratory muscles both in isolated muscle preparations, as well as in animals and normal human beings. Furthermore, theophylline restores diaphragmatic fatigue and prevents fatigue of the diaphragm when given prophylactically. Finally, it was recently shown that theophylline improves diaphragmatic function in COPD patients, all of whom were CO2 retainers (PaCO2 53 +/- 3 mm Hg) and hypoxemic (PaO2 57 +/- 8 mm Hg). Patients improved transdiaphragmatic pressure and were less susceptible to fatigue. Presently the mechanisms of action of theophylline regarding its effects on diaphragmatic function are not fully elucidated. Experimental evidence, however, suggests that theophylline may have an effect on transmembrane calcium movements by blocking adenosine receptors.

Aminophylline↗
PubMed1991

Bilateral diaphragm paralysis after cardiac surgery with topical hypothermia.

Bilateral diaphragm paralysis is a rare but important complication of open heart surgery. Two cases were found among 360 prospectively studied patients undergoing open heart surgery during one year. Both patients had insulin dependent diabetes with peripheral neuropathy and this may have contributed to their diaphragm paralysis. The patients were studied postoperatively for one year with measurements of lung function, nocturnal oximetry, diaphragmatic function, and phrenic nerve conduction. Treatment with intermittent positive airway pressure ventilation by nasal mask was effective in both patients. After nine months one patient had recovered completely with normal phrenic nerve conduction and diaphragmatic function; the other continues most of his normal daytime activities, but still requires nasal positive airway pressure ventilation for six hours at night.

Cardiac Surgical Procedures↗
PubMed1990

Relationship of diaphragm glycogen, lactate, and function to respiratory failure.

Diaphragmatic function and biochemical changes were studied during respiratory failure induced by incremental inspiratory threshold loading in anesthetized rabbits (1) who were unbound and spontaneously breathing, (2) during lower thoracic and abdominal binding, and (3) while bound and undergoing transvenous phrenic nerve pacing of the diaphragm. There was no evidence of contractile fatigue or alterations in glycogen or lactate concentrations in the diaphragm of unbound spontaneously breathing animals. With thoracoabdominal binding, there was a fall in maximal transdiaphragmatic pressure (Pdimax) and the ratio of diaphragmatic force divided by neural input (Pdi/Edi ratio); there was no change in diaphragm glycogen, but there was a significant rise in lactate. In the bound and phrenic-paced animals Pdimax and Pdi/Edi ratio fell, and there was significant glycogen depletion and lactate accumulation. There was a significant correlation between diaphragm function and the levels of diaphragm glycogen and lactate at the point of respiratory failure. We conclude that (1) respiratory failure induced by incremental inspiratory threshold loading was not associated with either contractile fatigue of the diaphragm or diaphragmatic biochemical changes in unbound spontaneously breathing animals, (2) when mechanisms that preserve diaphragmatic function are circumvented by phrenic pacing and/or thoracoabdominal binding, diaphragm fatigue and biochemical changes occur, and (3) there is a significant relationship between in vivo evidence of contractile fatigue of the diaphragm and diaphragmatic glycogen depletion and lactate accumulation.

Acid-Base Equilibrium↗
PubMed1987

Effect of theophylline on diaphragmatic muscle function.

Recent investigations have shown that theophylline improves diaphragmatic contractility of the respiratory muscles in isolated muscle preparations in animals and in normal human subjects. It has also been demonstrated that theophylline can reverse diaphragmatic fatigue and prevent fatigue of the diaphragm when given prophylactically. These effects have also been demonstrated in patients with severe chronic obstructive pulmonary disease, all of whom retained CO2 (PaCO2 53 +/- 3 mm Hg) and had hypoxia (PaO2 57 +/- 8 mm Hg). Theophylline, which increases respiratory muscle strength and delays the onset of diaphragmatic fatigue therefore could be a very useful agent in the treatment of patients with chronic airway obstruction.

Aminophylline↗
PubMed1986

Inspiratory muscle function in unilateral diaphragmatic paralysis.

Pulmonary function has been extensively studied in unilateral diaphragmatic paralysis (UDP), but there is scarce information regarding inspiratory muscle function in this condition. We therefore studied inspiratory muscle function in 8 patients with UDP (Group 1: age 48.3 +/- 2.1 yr of age, means +/- SD) as well as in 7 patients with UDP and concomitant cardiopulmonary disease (Group 2: 60.6 +/- 13 yr of age). Twelve young normal subjects were also studied (32.3 +/- 7.7 yr of age). Maximal static transdiaphragmatic and inspiratory mouth pressure were measured at FRC. Gastric (Pga), esophageal (Pes), and transdiaphragmatic (Pdi) pressure swings were measured during quiet breathing. There was no difference in inspiratory muscle function in left-sided versus right-sided UDP. Paradoxical gastric pressure swings were observed in 4 patients from Group 1 and in 5 from Group 2. In 2 patients from Group 1 and 1 from Group 2, Pga did not change during quiet breathing. In the remaining 3 patients, Pga swings were similar to those observed in the normal subjects. Maximal Pdi was reduced in half of the patients from Group 1 and in all of the patients from Group 2. Maximal inspiratory pressure was below normal values in 2 patients from Group 1 and in all patients from Group 2. We conclude that unilateral diaphragmatic paralysis is associated with an abnormal pattern of use of respiratory muscles during quiet breathing, characterized by the use of intercostal and accessory inspiratory muscle or compensatory use of abdominal expiratory muscles. Inspiratory muscle strength was impaired in some of the patients, and it worsened when cardiopulmonary disease was present.

Adult↗