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Biomedical subjects

J W Fitting

Publications and source records attributed to J W Fitting.

At least 73 records · Page 4Linked to original sources
PubMed1991

Esophageal and mouth pressure during sniffs with and without nasal occlusion.

The sniff maneuver has recently been advocated for assessing inspiratory muscle strength. We characterized the relationship between mouth pressure (Pmo) and esophageal pressure (Pes) during sniffs performed with open, semi-occluded, and occluded nose. In seven normal subjects, pressure was simultaneously measured with a mouthpiece (Pmo) an esophageal balloon (Pes) during high- and low-intensity sniffs performed from FRC. With open nose, the mean ratio Pmo/Pes was 0.96 +/- 0.05 (mean +/- SE). The mean ratio Pmo/Pes was not significantly different in high- and low-intensity sniffs. With one nostril occluded, the mean ratio Pmo/Pes was 1.03 +/- 0.04. The ratio Pmo/Pes was significantly higher than with open nose for all sniffs (P less than 0.05) and low-intensity sniffs (P less than 0.01). With both nostrils occluded, the mean ratio Pmo/Pes was 1.06 +/- 0.03, with occasional marked overestimation of Pes by Pmo. We conclude that Pmo generally reflects Pes during sniffs performed with open and semi-occluded nose, but not with complete nasal occlusion.

Adult↗
PubMed1991

Maximal sniff mouth pressure compared with maximal inspiratory pressure in acute respiratory failure.

Inspiratory muscle strength most often is better reflected by sniff Pes than PImax against occlusion. Furthermore, sniff Pes can be estimated noninvasively by the measurement of sniff Pmo in normal subjects and in patients with respiratory muscle weakness. The aim of this study was to compare sniff Pmo and P.PImax to assess inspiratory muscle strength in patients with acute respiratory failure. The highest pressure was produced by P.PImax in 61 percent of measurements, and by sniff Pmo in 39 percent. Above 35 cm H2O P.PImax yielded the highest pressure in 55 percent of cases and the ratio sniff Pmo/P.PImax was 1.20 +/- 0.54. Below 35 cm H2O, P.PImax yielded the highest pressure in 75 percent of cases and the ratio sniff Pmo/P.PImax was 0.76 +/- 0.35 (p less than 0.02). Thus, measurements of sniff Pmo and P.PImax complement one another for assessing inspiratory muscle strength. However, sniff Pmo underestimates inspiratory muscle strength in patients with severe inspiratory muscle weakness.

Acute Disease↗
PubMed1991

Respiratory muscle fatigue limiting physical exercise?

Inspiratory muscle fatigue has been documented during loaded breathing or acute respiratory failure, but its role in exercise limitation is still undetermined. Electromyographic (EMG) signs of diaphragmatic fatigue develop in normal subjects hyperventilating above 70% of maximal voluntary ventilation (MVV), a ventilatory level commonly attained at peak exercise. EMG signs of diaphragmatic fatigue also occur during high power cycling exercise in normal subjects and chronic obstructive pulmonary disease (COPD) patients. However, a loss of respiratory muscle strength has rarely been documented following strenuous physical exercise with techniques independent of the subjects' collaboration. Prior inspiratory muscle fatigue decreases exercise tolerance in normal subjects but its effect is largely unknown in COPD patients. Respiratory muscle rest by negative pressure ventilation was reported to improve exercise tolerance in COPD, but this beneficial effect was not confirmed by controlled studies. The effect of inspiratory muscle training on exercise tolerance is still undefined by existing data, in part because of differences in methods and selection criteria between studies. Although respiratory muscle fatigue may occur during exercise, it is not clearly established whether interventions directed at respiratory muscles may improve exercise tolerance in COPD.

Electromyography↗
PubMed1990

[Ventilatory function and bronchial responsiveness in army recruits].

Lung function and determination of the bronchial responsiveness to methacholine were performed in two groups of Swiss army recruits aged 20 years (total 233), where 144 had respiratory complaints or a history of prior asthma and 89 were asymptomatic, among whom 26 had recently suffered from upper respiratory tract infection (URTI). A bronchial obstruction (ratio FEV1/FVC less than 73%) was observed among 6% of the subjects with symptoms, 6% of the asymptomatic control subjects and 4% in the group with recent URTI. The differences are not significant. A bronchial hyperresponsiveness (defined as PD20 less than 900 mcg) was observed in 45% of the symptomatic subjects (54% in 109 recruits complaining of dyspnea on exertion) against 3% in the control group (p less than 0.001) and 12% in the group with recent URTI (NS, p = 0.14). Among subjects complaining of dyspnea on exertion, more than half have an obvious bronchial hyperresponsiveness at a level usually observed in asthmatics, most of them without any clinical finding or permanent bronchial obstruction. Although the sensitivity of the determination of bronchial responsiveness is low (47%) its specificity is high (97%). The test allows detection of some subjects with asthma among young subjects complaining of respiratory troubles in spite of normal clinical examination and lung function. A normal level of bronchial responsiveness practically excludes asthma.

Adult↗
PubMed1990

[Measurement of the effect of a bronchodilator agent].

Response in a bronchodilator must be expressed by the combining the largest amplitude of response with the highest reproducibility. The forced expiratory volume in the first second (FEV1) meets these conditions and thus represents the best test. The bronchodilator response is commonly expressed in percent of the initial FEV1. Through a mathematical bias, this method overestimates the response in the most severely obstructed subjects. Expressing the bronchodilator response in percent of predicted FEV1 eliminates this distortion and must be preferred.

Airway Obstruction↗
PubMed1990

[Evaluation of the strength, reserve and fatigue of the respiratory muscles in weaning from mechanical ventilation].

Beyond a certain threshold of intensity and duration of contraction the respiratory muscles are prone to fatigue, and this process may preclude weaning from mechanical ventilation. Respiratory muscle fatigue can be detected by several techniques (maximal voluntary pressures, electrical stimulation, electromyography, muscle relaxation rate, analysis of breathing movements, occlusion pressure). The most reliable techniques are complex, but new noninvasive tests are presently under development.

Electric Stimulation↗
PubMed1990

Muscle fatigue in acute respiratory failure.

Fatigue of the respiratory muscles is now well documented but still remains a process that cannot be assessed easily. Several methods are available to detect fatigue; they represent windows allowing different viewpoints on the same phenomenon. The definition and determinants of respiratory muscle fatigue and some of the methods used to detect it are reviewed. On the basis of the available evidence provided by each of these methods, the role played by muscle fatigue in acute respiratory failure (ARF) is discussed.

Acute Disease↗
PubMed1990

Resting energy expenditure in interstitial lung disease.

Because interstitial lung disease increases the work of breathing, the aim of this study was to determine if this condition is associated with increased energy requirements. A group of 12 clinically stable patients with interstitial lung disease was studied. Patients with a history of weight loss had significantly more severe lung volume restriction. Regression analysis showed that 42% of body weight variation was explained by vital capacity (p less than 0.025). Resting energy expenditure was measured by standard methods of indirect calorimetry. The measurements were performed with a ventilated hood during prolonged steady-state periods after an overnight fast. We found that resting energy expenditure was increased to 117.3 and 118.7% of the predicted basal metabolic rate, according to Fleisch and to Harris and Benedict reference values, respectively (p less than 0.001). Furthermore, resting energy expenditure was increased to 120.8% of the predicted value according to body fat-free mass (p less than 0.001). This extra energy expenditure in patients with interstitial lung disease is similar to that recently reported in patients with chronic obstructive pulmonary disease.

Adult↗
PubMed1989

Recovery of diaphragm function after laparotomy and chronic sonomicrometer implantation.

If sonomicrometry transducers could be implanted permanently into the diaphragm, direct measurements of costal and crural length and shortening could be made during recovery from the laparotomy and then indefinitely in an awake, non-anesthetized mammal. We report results from six canines in which we successfully implanted transducers onto the left hemidiaphragm through a midline laparotomy and measured segmental shortening and ventilation at intervals through 22 days of postoperative recovery. After laparotomy, breathing pattern, including tidal volume, respiratory rate and mean inspiratory flow, stabilized by the 4th postoperative day (POD). Tidal shortening of costal and crural segments increased from 1.82 and 1.45% of end-expiratory length (%LFRC) on the 2nd POD to 5.32 and 8.56% LFRC, respectively, after a mean of 22 POD. Segmental shortening did not stabilize until 10 POD, and the recovery process displayed a sequence of segmental motions: lengthening, biphasic inspiratory lengthening-shortening, and increasing simple shortening. Three weeks after implantation, costal and crural segments were stable and shortening 5.32 and 8.56% LFRC, respectively, and capable of shortening 49% LFRC with maximal phrenic stimulation. In a pair of recovered animals, the initial postoperative dysfunction did not recur after a subsequent, simple laparotomy. At postmortem examination, the chronically implanted sonomicrometer transducers were found to have evoked only a thin fibrotic capsule within the diaphragm.

Animals↗
PubMed1989

Diaphragm length adjustments with body position changes in the awake dog.

Sonomicrometry was used to measure end-expiratory length and tidal shortening of the costal and crural diaphragm in awake chronically instrumented dogs in the right lateral decubitus, standing, and sitting postures. End-expiratory length did not change significantly in standing but fell by 11.5% for the costal and by 14.4% for the crural segment in sitting, when compared with decubitus position. Tidal shortening of both segments did not change significantly in the three postures. From decubitus to sitting, diaphragmatic electromyogram (EMG) activity increased only in some dogs, not significantly for the group. The inspiratory swing of abdominal pressure was always positive in decubitus and negative in standing and sitting. In the latter two postures, abdominal pressure increased gradually during expiration and fell in inspiration, suggesting a phasic expiratory contraction of abdominal muscles. We conclude that diaphragmatic tidal shortening is maintained in the different postures assumed by the awake dog during resting breathing. It seems that the main compensatory mechanism for changes in diaphragmatic operational length is a phasic expiratory contraction of the abdominal muscles rather than an increase in diaphragmatic EMG activity.

Abdomen↗
PubMed1989

Procainamide for dyspnea in myotonic dystrophy.

We report the case of a patient with myotonic dystrophy who developed tachypnea and severe dyspnea without respiratory failure. Myotonia of inspiratory muscles was diagnosed on the grounds of marked prolongation of transdiaphragmatic pressure (Pdi) decay during sniffs. In view of the recognized sensory role of inspiratory muscles in dyspnea, it was hypothesized that antimyotonic therapy might relieve dyspnea in this patient. Procainamide therapy induced a decrease in half relaxation time of Pdi during sniffs and yielded a striking clinical improvement with cessation of tachypnea and dyspnea. Later, this beneficial effect was maintained by tocainide after procainamide was stopped because of a lupus syndrome. We conclude that myotonia of respiratory muscles can cause severe dyspnea that can be improved by antimyotonic therapy.

Diaphragm↗
PubMed1989

Probability of malignancy in pleural fluid eosinophilia.

Pleural fluid eosinophilia is rare and is commonly considered as an indicator of good prognosis. In a series of 224 patients, pleural eosinophilia was present in four of 84 malignant cases; however, the incidence of malignancy in the presence of pleural eosinophilia was 0.40, being explained by a relatively high prevalence of malignancies in the population studied. Although pleural eosinophilia is rare in malignant effusions, it cannot be considered as indicating a good prognosis without taking into consideration the local prevalence of malignancies.

Eosinophilia↗
PubMed1989

Energy expenditure and rib cage-abdominal motion in chronic obstructive pulmonary disease.

The resting energy expenditure (REE) was measured by indirect calorimetry in 10 patients with chronic obstructive pulmonary disease (COPD) in stable clinical state and in 10 normal subjects. In order to avoid artefactually increased values, REE was obtained from prolonged measurements in steady state using a ventilated hood, without facial apparatus. The REE of COPD patients was significantly increased to 117% of predicted basal metabolic rate and to 125% of the control group values. Rib cage and abdominal movements were measured in COPD patients by inductance plethysmography and expressed with three indices: rib cage contribution to tidal volume (RC/VT), variability in compartmental contribution to tidal volume (SD RC/VT), and maximal compartmental amplitude/tidal volume ratio (MCA/VT). No correlation was found between REE and any of the indices of rib cage and abdominal motion. We conclude that the REE is increased in patients with COPD in stable clinical state, but is not related to the degree of abnormal rib cage-abdominal motion.

Adult↗
PubMed1988

Dissociation between diaphragmatic and rib cage muscle fatigue.

To assess rib cage muscle fatigue and its relationship to diaphragmatic fatigue, we recorded the electromyogram (EMG) of the parasternal intercostals (PS), sternocleidomastoid (SM), and platysma with fine wire electrodes and the EMG of the diaphragm (DI) with an esophageal electrode. Six normal subjects were studied during inspiratory resistive breathing. Two different breathing patterns were imposed: mainly diaphragmatic or mainly rib cage breathing. The development of fatigue was assessed by analysis of the high-to-low (H/L) ratio of the EMG. To determine the appropriate frequency bands for the PS and SM, we established their EMG power spectrum by Fourier analysis. The mean and SD for the centroid frequency was 312 +/- 16 Hz for PS and 244 +/- 48 Hz for SM. When breathing with the diaphragmatic patterns, all subjects showed a fall in H/L of the DI and none had a fall in H/L of the PS or SM. During rib cage emphasis, four out of five subjects showed a fall in H/L of the PS and five out of six showed a fall in H/L of the SM. Four subjects showed no fall in H/L of the DI; the other two subjects were unable to inhibit diaphragm activity to a substantial degree and did show a fall in H/L of the DI. Activity of the platysma was minimal or absent during diaphragmatic emphasis but was usually strong during rib cage breathing. We conclude that fatigue of either the diaphragm or the parasternal and sternocleidomastoid can occur independently according to the recruitment pattern of inspiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗