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J W Fitting

Publications and source records attributed to J W Fitting.

At least 91 records · Page 5Linked to original sources
PubMed1988

Effect of transdiaphragmatic pressure partitioning on activation and fatigue of the diaphragm.

Fatiguing contractions of the diaphragm during inspiratory resistive loading are accompanied by a predictable rate of decay in the high/low (H/L) frequency ratio of the diaphragmatic EMG (EMG-DI) when the esophageal and gastric pressure (Pes and Pga) components of transdiaphragmatic pressure (Pdi) are equal. However, Pes and Pga do not contribute equally to Pdi under a number of clinical and physiologic conditions. We therefore tested the effect of varying the Pes and Pga contribution to Pdi on the EMG-DI using an esophageal electrode in 5 normal men during fatiguing contractions. Falls in the H/L occurred in all subjects regardless of the relative contribution of Pes and Pga to Pdi at a tension-time index of 0.29 +/- 0.1 (mean +/- SE). However, the time constant of decay of the H/L varied widely among subjects when Pes predominated (173.9 +/- 45.7 s; coefficient of variation, 58.7%) or Pga predominated (78.4 +/- 19.4 s; coefficient of variation, 55.2%), whereas it was consistent among subjects when Pes and Pga were equal (72.3 +/- 3.8 s; coefficient of variation, 11.6%). In addition, a significant relationship was found between the mean integrated activity of the EMG-DI compared with maximum and the time constant of decay of the H/L (r = 0.57, p less than 0.03). We conclude that the differences in the rate of decay of the H/L was at least partly a result of differences in the relative activation of the crural diaphragm at the same Pdi.

Adult↗
PubMed1987

Effect of anesthesia on canine diaphragm length.

General anesthesia has been shown to induce a cephalad shift of the end-expiratory position of the diaphragm in recumbent human subjects. The authors used the technique of sonomicrometry in chronically instrumented dogs to measure the length changes occurring in the costal and crural diaphragm during anesthesia. Seven dogs were studied in lateral decubitus; first awake, and then during pentobarbital anesthesia. The end-expiratory length (LFRC) of the crural segment increased gradually and reached a plateau after 30 min of anesthesia. Costal LFRC did not change. The results were similar when the hemidiaphragm under study was placed in a gravity-dependent or in a non-dependent position. In the awake state, variable levels of post-inspiratory or tonic diaphragmatic EMG activity were observed, which disappeared during anesthesia. The authors conclude that anesthesia induces a 7-8% increase in end-expiratory length of the crural, but not of the costal, diaphragm. This selective adjustment is not due to a pressure gradient effect, but is compatible with a loss of tone in the crural diaphragm.

Anesthesia, General↗
PubMed1987

Effect of thoracoabdominal breathing patterns on inspiratory effort sensation.

The respiratory sensations evoked by added inspiratory loads are currently thought to be largely mediated by the activity of the inspiratory muscles. Because of the differences in proprioceptors and in afferent and efferent innervations among the inspiratory muscles, we hypothesized that the sensation evoked by a given load would be different when the motor command is directed mainly to rib cage muscles or mainly to the diaphragm. To test this hypothesis, we studied six normal subjects breathing against several inspiratory resistances while emphasizing the use of rib cage muscles, or the diaphragm, or a combination of both. At the end of 10 loaded breaths the subjects rated the perceived magnitude of inspiratory effort on a Borg scale. A linear and unique relationship (r = 0.96 +/- 0.02; P less than 0.001) was found between the sensation and esophageal pressure (Pes) in the three thoracoabdominal breathing patterns. We conclude that the level of Pes, whether generated mainly by the rib cage muscles or the diaphragm, is the main variable related to the sensation of inspiratory effort under external inspiratory loads.

Abdomen↗
PubMed1987

Costal and crural diaphragm in early inspiration: free breathing and occlusion.

Changes in length of costal and crural segments of the canine diaphragm were measured by sonomicrometry within the first 100-300 ms of inspiration during CO2 rebreathing in anesthetized animals. Both segments showed small but significant decreases in end-expiratory length during progressive hypercapnia. Although both costal and crural segments showed electromyographic activity within the first 100 ms of inspiration, in early inspiration crural shortening predominated with minimal costal shortening. Neither segment contracted isometrically early in inspiration in the presence of airway occlusion. The amount of crural shortening during airway occlusion exceeded costal shortening; both segments showed increased shortening with prolonged occlusion and increasing CO2. Costal and crural shortening at 100 ms was not different for unoccluded and occluded states. These observations suggest that neural control patterns evoke discrete and unequal contributions from the diaphragmatic segments at the beginning of an inspiration; the crural segment may be predominately recruited in early inspiration. Despite traditional assumptions about occlusion pressure measurement (P0.1), diaphragm segments do not contract isometrically during early inspiratory effort against an occluded airway.

Airway Obstruction↗
PubMed1987

Diagnosis of diaphragmatic dysfunction.

Diaphragmatic dysfunction is an important entity, as it can cause severe dyspnea, ventilation-perfusion abnormalities, and ventilatory failure. The most frequent and important dysfunctions are diaphragmatic weakness, incoordination between the diaphragm and other respiratory muscles, fatigue, and paralysis. Methods for the diagnosis of dysfunction are reviewed and specific dysfunctions are briefly discussed with methods for their evaluation.

Diaphragm↗
PubMed1986

Velocity of shortening of inspiratory muscles and inspiratory flow.

Respiratory muscle length was measured with sonomicrometry to determine the relation between inspiratory flow and velocity of shortening of the external intercostal and diaphragm. Electromyographic (EMG) activity and tidal shortening of the costal and crural segments of the diaphragm and of the external intercostal were recorded during hyperoxic CO2 rebreathing in 12 anesthetized dogs. We observed a linear increase of EMG activity and peak tidal shortening of costal and crural diaphragm with alveolar CO2 partial pressure. For the external intercostal, no consistent pattern was found either in EMG activity or in tidal shortening. Mean inspiratory flow was linearly related to mean velocity of shortening of costal and crural diaphragm, with no difference between the two segments. Considerable shortening occurred in costal and crural diaphragm during inspiratory efforts against occlusion. We conclude that the relation between mean inspiratory flow and mean velocity of shortening of costal and crural diaphragm is linear and can be altered by an inspiratory load. There does not appear to be a relationship between inspiratory flow and velocity of shortening of external intercostals.

Animals↗
PubMed1986

The relation of inspiratory effort sensation to fatiguing patterns of the diaphragm.

Tension in the respiratory muscles and the subsequent intrathoracic subatmospheric pressure swing plays a role in respiratory effort sensation. However, the role of a diaphragmatic fatiguing process in the genesis of this sensation has not been examined. Therefore, we studied the effect of fatiguing contractions of the diaphragm on inspiratory effort sensation (IES) in 6 normal male subjects during inspiratory resistive loading. Four diaphragmatic fatiguing and 4 diaphragmatic nonfatiguing patterns were developed for each subject. These 8 patterns were imposed in random order for 10 breaths (50 s) with duty cycle and tidal volume fixed. The presence or absence of a diaphragmatic fatiguing process was confirmed by analysis of the high to low ratio of the electromyographic signal from an esophageal electrode. Subjects scored their IES immediately after each run using a modified Borg scale. There was a very strong correlation between IES and esophageal pressure (Pes) expressed as a percentage of maximal inspiratory esophageal pressure (Pes/Pesmax %) (r = 0.88, p less than 0.001). However, IES was independent of the presence of a diaphragmatic fatiguing pattern. Furthermore, there was no difference in the slope or intercept of the regression lines relating IES to Pes/Pesmax % when fatiguing and nonfatiguing runs were analyzed separately. We conclude that the severity of IES during resistive loading held for 50 s is independent of the development of diaphragmatic fatigue.

Adult↗
PubMed1986

[Technics for the functional evaluation of the thoracic cage].

A study of lung volumes offers an overall index of thoracic mobility. The techniques of magnetometry and respiratory plethysmography by induction allow studies of thoracic wall movements to be separated into two compartments by measuring thoracic and abdominal movements. These techniques enable a quantitative evaluation of thoraco-abdominal incoordination seen notably in patients with chronic airflow obstruction and in cases of respiratory muscle fatigue. Similar information is obtained by measuring variations in inspiratory pleural and abdominal pressure, using oesophageal and gastric balloons. The maximal force of respiratory muscles is an important index of the functional reserve at a patient's disposal and may be assessed by measuring maximal inspiratory and expiratory pressures at the mouth against an occlusion. Diaphragmatic force is assessed by the maximal trans-diaphragmatic pressure. Respiratory muscle fatigue appears when their contraction is sustained above a certain threshold of tension and duration. This phenomenon may be detected by a diminution of maximal pressures. For example, the fatigue of inspiratory muscles is accompanied by a fall of maximal inspiratory and trans-diaphragmatic pressures. The fatigue process can also be detected early by changes in the pattern of the diaphragmatic electromyogram. The principles and limitations of different techniques of assessment of respiratory muscle fatigue are analysed. The use of one or several of these techniques accompanied by an awareness of the clinical signs of respiratory muscle fatigue ought to enable an early detection of this condition.

Humans↗
PubMed1984

[Increase in polynuclear neutrophils of the broncho-alveolar irrigation fluid following exposure in a case of acute alveolitis].

We report a case of a patient admitted to hospital for respiratory distress caused by an acute alveolitis due to exposure to goose feathers in a duvet. Several months after the acute episode a series of examinations, including a broncho-alveolar lavage, were performed before and after a challenge test of exposure to the suspected duvet. We noted a febrile reaction, an increase of the alveolar-arterial oxygen gradient, a rise in neutrophils both in the blood and broncho-alveolar lavage liquid. In the absence of specific demonstrable antibodies, this surge of neutrophils in the alveolar walls does not seem to be due to an immune complex reaction, but is more likely to be a non-immunological phenomenon.

Alveolitis, Extrinsic Allergic↗
PubMed1979

Neuropathy, amyloidosis, and monoclonal gammopathy.

Three cases of neuropathy with monoclonal gammopathy and amyloid deposits in peripheral nerves are described. They appeared to present a benign gammopathy because of the duration of the neuropathy in the absence of any clinical or biological sign of myeloma or macroglobulinaemia. The pathological abnormality found in the sural nerves of the three patients was characterised by a marked loss of myelinated and unmyelinated nerve fibres because of active axonal degeneration with Wallerian degeneration. The most striking feature in all three cases was the finding of deposits identified as an accumulation of microfibrils.

Aged↗
PubMed1978

[Clinical and radiological diagnosis of chronic obstructive lung syndromes].

The clinical signs produced by the respiratory movements reveal the main patho-physiological types in patients with chronic obstructive lung disease. Roentgenological signs do not correlate with the severity of ventilatory disorders and pre-capillary hypertension. Conversely the roentgenological signs of the post-capillalry hypertension are precocious and reliable.

Aged↗
PubMedDate not supplied

Body composition by X-ray absorptiometry and bioelectrical impedance in chronic respiratory insufficiency patients.

Nutrition assessment is important during chronic respiratory insufficiency to evaluate the level of malnutrition or obesity and should include body composition measurements. The appreciation of fat-free and fat reserves in patients with chronic respiratory insufficiency can aid in designing an adapted nutritional support, e.g., nutritional support in malnutrition and food restriction in obesity. The purpose of the present study was to cross-validate fat-free and fat mass obtained by various bioelectric impedance (BIA) formulas with the fat-free and fat mass measured by dual-energy X-ray absorptiometry (DXA) and determine the formulas that are best suited to predict the fat-free and fat mass for a group of patients with severe chronic respiratory insufficiency. Seventy-five patients (15 women and 60 men) with chronic obstructive and restrictive respiratory insufficiency aged 45-86 y were included in this study. Body composition was calculated according to 13 different BIA formulas for women and 12 for men and compared with DXA. Because of the variability, calculated as 2 standard deviations, of +/- 5.0 kg fat-free mass for women and +/- 6.4 kg for men for the best predictive formula, the use of the various existing BIA formulas was considered not clinically relevant. Therefore disease-specific formulas for patients with chronic respiratory insufficiency should be developed to improve the prediction of fat-free and fat mass by BIA in these patients.

Absorptiometry, Photon↗