Bulletin de physio-pathologie respiratoire最新文献

Acutely ill patients often show rapid and sometimes concomitant changes in haemodynamics, pulmonary exchange and O2-uptake. PaO2 reflects the interrelationships between these three factors. The Qs/Qt shunt is computed by taking two simultaneous blood samples, one systemic arterial, the other mixed venous, with the patient inhaling pure O2 for twenty minutes. In estimating the fraction of total cardiac output unsaturated in pulmonary transit, Qs/Qt is practically used as a selective test for pulmonary gas exchange. We propose a nomogram, showing in terms of Qs/Qt shunt the variations of PaO2, of haemoglobin O2 saturation and of arterial-venous difference of O2 concentrations. Blood gas changes during treatment of shock or of acute respiratory insufficiency are explained by use of this nomogram.

This review considers functional repercussions of shock state on the different stages of oxygen transport from alveolus to mitochondria. At the pulmonary level, the decrease in perfusion pressure induces disturbances in the distribition of VA/Q ratio, and therefore leads to aerial hypoxaemia. Prolonged ischemia injures the air-blood barrier and reduces the area of exchange. Decrease in oxygen delivery to the tissue is related to a fall in cardiac output (hemorrhagic and cardiogenic shock) or to a primary disturbance in peripheral circulatory distribution (septic shock) or to a primary disturbance in peripheral circulatory distribution (septic shock). The intervention of compensating factors leads to a redistribution of the regional perfusion and probably to an easier oxygen delivery by haemoglobin. However circulatory inhomogeneity by itself produces a progressive deterioration of microcirculation. Decrease in intracapillary circulation. Decrease in intracapillary circulation and impairment in blood rheologic properties contribute to aggregates formation and intravascular coagulation. The result is a decrease in capillary diffusion capacity and in oxygen intracellular transport. When intracellular PO2 reaches a critical level, the functional exclusion of mitochondria involves a metabolic shift to anaerobiosis. The value of hyperlactacidemia as a sign of oxygen debt is discussed.

There is remarkably little information about the direct relationship of physiological abnormality in coal workers' pneumoconiosis with structural changes in the lung and there are major difficulties in attempting such a correlation. The general population, including coal workers, has a regrettably high prevalence of pulmonary functional abnormalities attributable to chronic bronchitis or to emphysema occurring either separately or together. The pathological basis for the functional impairment in chronic bronchitis and possible functional sequelae to the anatomical changes of emphysema are not clearly understood, making it extremely difficult to identify separately the functional effects associated with coal workers' pneumoconiosis. Any study of coal workers' pneumoconiosis must take into account the background population. The published investigations relating the functional abnormalities and pathological changes in the lung in coal workers' pneumoconiosis are reviewed. The relationship of functional change to emphysema, chronic bronchitis, cor pulmonale and the specific lesions of coal workers' pneumoconiosis are dealt with. There is great need for further work in this field, both in the form of simple studies of pathological changes in miners' lungs as well as more complex attempts to correlate such pathological surveys with physiological abnormalities in life.

Over the past five years the cardio-respiratory function of selected groups of U.S. coal workers has been intensively studied. The subjects studied included approximately 10,000 working miners at mines selected as part of an epidemiological study of the prevalence and progression of coal workers' pneumoconiosis (CWP) as well as selected groups of non-working symptomatic miners. The occupation of coal mining per se is sometimes associated with a mild reduction in ventilatory capacity which is not closely related to radiographic category of simple CWP. Slight abnormalities in gas exchange and lung mechanics appear to be associated with the higher categories of simple CWP which do not appear to affect longevity. Subjects with complicated CWP (massive fibrosis) demonstrate moderate to severe degrees of obstruction, abnormalities of gas exchange and lung mechanics that generally relate to the extent of the massive fibrosis and result in premature disability and death.

Lung function was examined in 55 patients with sandblasters' silicosis. In this type of silicosis, patients with simple nodular disease had normal function. Restrictive and obstructive impairment was present in patients with large opacities, and was more marked in patients with radiographic evidence of contraction or cavitation. In the last group, striking average annual declines in ventilatory function occurred. Compared to patients with classical silicosis, these patients were younger and had intense, short exposures to free crystalline silica. The pattern of functional abnormalities suggested that restriction of lung volumes is a fundamental abnormality in this form of silicosis.

The lung diffusing capacity for carbon monoxide (DLCO single-breath) and its two components, the capillary blood volume (Vc) and the diffusing capacity of the membrane (DMCO) were measured at rest in 43 miners and 141 control subjects, the values in whom enabled reference formulae to be established; in 30 control subjects and in the majority of the miners these indices were measured during exercise. The main results are as follows: the diffusion indices are on average slightly decreased in simple coal workers' pneumoconiosis; both DMCO and Vc contribute to the lowering of DLCO, at rest and during exercise; individually Vc is more often significantly altered than DMCO; on effort the percentage increase of DLCO is normal in coal miners; the data during exercise suggest that smoking habit contributes more to lowering DLCO than does pneumoconiosis itself; lastly the diffusion indices are lower in miners with "pin-head" than those with micronodular opacities: this tendency is more pronounced during exercise. These findings are discussed.

Three homogeneous groups of patients with silicosis, coal workers' pneumoconiosis and arc welders' pneumoconiosis had been reexamined after an interval of six years. The same examinations were repeated on each occasion with the purpose of evaluating the evolution of radiographic and functional changes. The clinical course, roentgenographic findings and results of function tests differed in the three groups. In silicosis and coal workers' pneumoconiosis the roentgenographic changes showed distinct progression. This progression was less evident in coal workers' pneumoconiosis, but deterioration of pulmonary function was more pronounced than in silicosis, apparently due to emphysema. In pneumoconiosis of welders roentgenographic changes showed a clear tendency to regression and respiratory function was not impaired.

Epidemiological investigations of ventilatory capacity in men working in British coal mines are reviewed. The results are related to radiological category of pneumoconiosis, respiratory symptoms, cigarette smoking and dust exposure. In summary it was found that dust exposure was associated with a fall in FEV1.0 but that there was no further fall assoicated with the presence of simple pneumoconiosis. Simple pneumoconiosis appeared to be evidence of the amount of previous dust exposure and suggested that this had been sufficient to cause a measurable fall in FEV1.0. The extent of the ventilatory impairment associated with simple pneumoconiosis was less than that due to age alone in most men. Cigarette smoking was found to be an important cause of ventilatory impairment.

Two simple indices of pulmonary mixing (helium mixing time in a closed circuit, and mixing ventilation) were measured in 274 patients (mostly miners) with silicosis, aged 50 years or less (mean 42.4 years); the results were analysed in respect to silicosis category and type, presence of co-existent chronic bronchitis and ventilatory performance, and were compared to those of a group of normal subjects to assess statistical significance. The average results for the whole group were 5.81 min for mixing time (tmix) and 62.3 1 for mixing ventilation (Vmix), representing 1.8 times and 2.4 times the normal, respectively; the results were higher for patients with co-existent chronic bronchitis within each radiological category, except the last ("C" opacities), but the differences were significant only for patients with small opacities and with "suspect pneumoconiosis". Among patients with small rounded opacities the co-existence of healed tuberculosis (apical fibrous nodules) or of other X-ray changes did not influence the pulmonary mixing; no difference was found between the three types of small opacities. A slight tendency towards lower values in patients with early conglomeration ("A" opacities) allows the suggestion of conglomeration starting in "slow" lung spaces. The best results were those of patients with normal ventilatory function followed by those with a restrictive and then by those with an obstructive ventilatory impairment. The most severe mixing disturbance was found among patients with chronic bronchitis and obstructive defect with "suspect pneumoconiosis", who are not covered by occupational disablement compensation.