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Biomedical subjects

J C Yernault

Publications and source records attributed to J C Yernault.

At least 55 records · Page 3Linked to original sources
PubMed1995

Comparison of computed density and macroscopic morphometry in pulmonary emphysema.

High-resolution computed tomography (HRCT) scans were obtained at 1 cm intervals in 63 subjects referred for surgical resection of a cancer or for transplantation to find out whether the relative area of lung occupied by attenuation values lower than a threshold would be a measurement of macroscopic emphysema. Using a semiautomatic procedure, the relative areas occupied by attenuation values lower than eight thresholds ranging from -900 to -970 HU were calculated on the set of scans obtained through the lobe or the lung to be resected. The extent of emphysema was quantified by a computer-assisted method on horizontal paper-mounted lung sections obtained every 1 to 2 cm. The only level for which no statistically significant difference was found between the HRCT and the morphometric data was -950 HU. To determine the number of scans sufficient for an accurate quantification, we recalculated the relative area occupied by attenuation values lower than -950 HU on progressively fewer numbers of scans and investigated the departure from the results obtained with 1 cm intervals. Because of wide variations in this departure from patient to patient, a standard cannot be recommended as the optimal distance between scans.

Adult↗
PubMed1995

Inert gas single-breath washout after heart-lung transplantation.

We prospectively studied the distribution of ventilation in 22 heart-lung transplant (HLT) recipients. At entry into study, the patients had undergone surgery an average of 6.7 mo earlier, and were followed for a mean period of 16 mo. Vital-capacity (VC) single-breath washouts as well as single-breath washouts using a 1-L inspiration from FRC were performed on a total of 395 occasions. The inhaled gas mixture consisted of 5% He, 5% SF6, and 90% O2, and the expired N2, He, and SF6 concentrations were analyzed. Six patients showed normal standard pulmonary-function tests and indexes of ventilation distribution throughout the study. Five patients gradually developed an irreversible airflow obstruction, presumably due to obliterative bronchiolitis (OB). They showed increases in the slopes of the N2, SF6, and He alveolar plateaus (SN2, SSF6, S(He)), but because S(He) increased more than SSF6, the slope difference (SSF6-S(He)) invariably decreased and became negative in four of five patients. Thirteen patients developed 16 episodes of reversible airflow obstruction as a result of acute infection or rejection of the lung allograft. The alterations in ventilation distribution were qualitatively similar to those seen in patients with OB. We conclude that: (1) ventilation distribution in the lung periphery is normal in HLT recipients with adequate allograft function; (2) the airflow obstruction elicited by OB and acute episodes of lung infection or rejection is accompanied by increases in SN2, SSF6, and S(He) and decreases in SSF6-(He)).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Chest percussion.

The direct method of chest percussion, first described by Auenbrugger but disseminated by Corvisart, has rapidly been replaced by the indirect or digitodigital method. Chest percussion has not been evaluated by modern acoustic means, so that our present knowledge of the method does not consistently differ from the 19th century approach. Auscultatory percussion is not superior to conventional percussion.

Auscultation↗
PubMed1995

Can computed tomography quantify pulmonary emphysema?

In the last decade, several studies have suggested the possible role of computed tomography (CT) in the detection and the quantification of pulmonary emphysema. In order to verify whether this new method is adequately validated, this article gives an overview of these studies. The review shows that most of the studies used conventional CT and were based on visual scoring. Only a few were based on high resolution CT (HRCT) or concerned objective measurements of computed density. In addition, only a few studies included normal subjects and distinguished centrilobular from panlobular emphysema. The number of scans obtained in each study is extremely variable, whilst the minimum number necessary to provide accurate results remains unknown. Recently, automatic objective procedures which are truly quantitative and are applicable to HRCT have been made available. They should take the place of subjective scoring methods but further studies, based on macroscopic as well as on microscopic comparisons, are needed to validate and to standardize these techniques.

Humans↗
PubMed1995

[Respiratory toxicity due to atmospheric pollutants. General review and a study of the relation to respiratory infections].

The main primary pollutants released into the atmosphere are sulfur dioxide (SO2), nitrogen monoxide and dioxide (NOx), particulate dust and in a less important part carbon monoxide (CO), hydrocarbons and heavy metals (Pb, Cd). Sulfur and nitrogen oxides are released from combustion of coals and fuels. Sulfates, nitrates and ozone are secondary pollutants resulting from chemical reactions within the atmosphere. While governmental directives limiting emissions have decreased SO2 and particulate matter levels, air quality in urban regions has improved in the last two decades. The role of air pollution as a risk factor for respiratory infections is difficult to address. Animal experiments demonstrate that air pollutants decrease the efficacy of lung defense mechanisms and increase the sensibility to respiratory infections. Nevertheless, because of difference in sensitivity between animal species and between exposure conditions, these effects are difficult to extrapolate to humans. Moreover, it is obvious that direct exposure studies of the sensibility of humans to respiratory infections are rare for ethical reasons. Epidemiological data addressing the role of air pollutants at usual levels can only suggest that some pollutants (SO2, suspended particulates) constitute a risk factor for respiratory infections. Since most of these studies do not include bacteriologic and virologic confirmation, it is unclear whether this respiratory morbidity is due to respiratory irritation or infection. In conclusion, we think that high concentrations of air pollutants are very likely to increase sensibility to respiratory infections in humans. There are however no sufficient data to clearly establish whether air pollution constitutes a risk factor for respiratory infections at usual ambient concentrations.

Air Pollutants↗
PubMed1994

[Quantifying dyspnea].

Several methods have been proposed in the recent years to quantitate dyspnoea in healthy subjects or patients. Dyspnoea can be serially assessed on exercise, using either a visual analogue scale or a Borg scale, and is usually analyzed in relation to ventilation, which defines a dyspnoea threshold and a dyspnoea/ventilation slope. Inhaled bronchodilators, oral morphine, continuous (or inspiratory) positive airway pressure or respiratory rehabilitation programmes are able to decrease the dyspnoea/ventilation slope in patients with chronic obstructive pulmonary disease, while atenolol and pneumectomy have a deleterious effect. Measurement of dyspnoea in everyday life is feasible using the oxygen cost diagram or the baseline dyspnoea index; these indices are responsive to therapy, e.g. to oral theophylline in patients with chronic obstructive pulmonary disease. Dyspnoea measured at rest is a marker for evaluating the perception of added loads (open scale) or acute bronchoconstriction in normals or patients; in the latter it may also reflect the perception of the degree in baseline ventilatory impairment or that of acute bronchodilation (bipolar visual analogue scale). Some respiratory patients being poor perceivers, methods able to improve the perception of airway obstruction are desirable in these individuals.

Differential Threshold↗
PubMed1994

On-line expiratory flow-volume curves during thoracic surgery: occurrence of auto-PEEP.

Flow-volume loops were monitored continuously in 39 patients undergoing thoracic surgery requiring one-lung ventilation. In 26 of the 39 patients (67%), auto-positive end-expiratory pressure (auto-PEEP) was seen on the flow-volume curves during both two-lung and one-lung ventilation. Eighty-seven percent of the patients whose trachea was intubated with a smaller size (35- and 37-French gauge) double-lumen tracheal tube exhibited auto-PEEP, compared with patients in whom the tube used was larger (39- or 41-French gauge: 54% and 50%, respectively). Before operation, mean airway resistance was significantly greater in patients who exhibited auto-PEEP during anaesthesia (2.4 cm H2O litre-1 s) than in patients without auto-PEEP (1.7 cm H2O litre-1 s).

Adult↗
PubMed1994

Neck muscle activity in patients with severe chronic obstructive pulmonary disease.

The present studies were designed to assess the pattern of activity and the frequency of activation of the neck muscles in patients with chronic obstructive pulmonary disease (COPD). Using concentric needle electrodes, we thus recorded the electromyograms of the scalene, sternocleidomastoid, and trapezius muscles during resting breathing in 40 stable patients with severe chronic airflow obstruction (FEV1 = 0.69 +/- 0.18 L) and hyperinflation (FRC = 228 +/- 40% of predicted); 17 patients were hypercapnic at rest. When breathing in the seated posture, all patients (100%) had strong inspiratory contraction of the scalenes. In contrast, no patient showed inspiratory activity in the trapezius, and only four patients (10%) showed definite, invariable inspiratory activity in the sternocleidomastoid. These two muscles were silent in the supine posture as well, even though the adoption of this posture was associated with an increase in dyspnea in most patients. We conclude, therefore, that in contrast to conventional thinking, most stable patients with severe COPD do not use the sternocleidomastoids or the trapezii when breathing at rest. Additional measurements indicated that the sternocleidomastoid inspiratory activity previously recorded in such patients was in general caused by a cross-contamination from surrounding muscles.

Adult↗
PubMed1994

Dyspnoea and flow-volume curve during exercise in COPD patients.

The purpose of this study, in patients with chronic obstructive pulmonary disease (COPD), was to examine the relationship of dyspnoea, rated on a visual analogue scale (VAS), to 1) tidal ventilatory variables measured on exercise and 2) pre-exercise lung function. Twenty one patients (forced expiratory volume in one second (FEV1) mean (SD) 1.19 (0.32) l) were studied. During a preliminary test, the maximal workload was assessed and the upper end of the VAS was anchored. On the study day, the tidal flow-volume curve on exercise was monitored and dyspnoea was assessed serially every minute. In each individual, the relationship of dyspnoea to various tidal ventilatory variables was studied using linear regression analysis; results were reported squared correlation coefficients, slopes and dyspnoea thresholds. Subsequently, the relationship of slopes and thresholds to pre-exercise lung function was examined. In all patients, dyspnoea showed a close correlation with ventilation, tidal volume, breathing frequency and tidal flow. The tidal peak inspiratory flow was the best individual predictor of dyspnoea with a median r2 of 0.91. Patients with the poorest pre-exercise lung function exhibited the highest rates of increase in dyspnoea and the lowest thresholds, the strongest correlation being observed between the dyspnoea/ventilation slope and pre-exercise maximal peak inspiratory flow (r2 = 0.54). In conclusion, for individual COPD patients dyspnoea on exercise is closely related to inspiratory flow. The degree of pre-exercise ventilatory impairment accounts, at most, for only half of the variation in dyspnoea perception between subjects.

Dyspnea↗
PubMed1994

Comparative analysis of inhaled particles contained in human bronchoalveolar lavage fluids, lung parenchyma and lymph nodes.

Translocation of inhaled particles from the alveolar spaces to lung parenchyma and lymph nodes is one of the mechanisms that determine the biopersistence of particles. This study compares the nonfibrous particulate burden in bronchoalveolar lavage (BAL) fluids, lung parenchyma, and thoracic lymph nodes and attempts to detect the degree of differentiation, if any, based on particle size or type. This comparison can only be done on BAL, lung parenchyma, and lymph node samples collected from the same subject over a short time. Patients undergoing surgical lung resection are suitable for this purpose. Particles recovered by digestion-filtration were counted, sized, and analyzed by analytical transmission electron microscopy. Total particle load ranges grossly between 10(5) to 10(7) p/ml in BAL, 10(9) to 10(10) p/g dry tissue in parenchyma and 10(10) to 10(11) p/g dry tissue in lymph nodes. Diameters are log-normally distributed and mean diameters range between 0.5 to 0.9 micron. Nonlamellar silicate particles have a significantly larger diameter in lymph nodes. Differences in particle type between the three sampling sites are small and nonsystematic.

Adult↗