Search PubMed⌕ Search

Biomedical subjects

A Harf

Publications and source records attributed to A Harf.

258 records · Page 15Linked to original sources
PubMedDate not supplied

[Effects of histamine on the pressure-volume curve of the respiratory system in the guinea pig].

Intravenous infusion of histamine has been shown to constrict smooth muscle of alveolar ducts. In this study, we have assessed the effects of a prolonged infusion of histamine to obtain a steady state response on quasistatic pressure-volume curves (P-V curves) together with the changes in dynamic compliance (Cdyn) and conductance (G) of the respiratory system. Increasing doses of histamine were given in order to obtain the dose-response characteristics of the changes in Cdyn, G and P-V curves. In nine anesthetized guinea-pigs under mechanical ventilation, administration of histamine resulted in a fall in Cdyn and G with a decrease of 50% of initial value approximately for 150 ng X kg-1 X s-1 of histamine. Modifications of the P-V curves were characterized by a decrease in the maximal volume, and an increase in the hysteresis of the P-V loop due to the downward displacement of the inflation limb. With infusion of histamine, there was a large decrease of quasi-static compliance which appeared to account for most of the decrease in dynamic compliance. Such changes in P-V curves can be related both to a closure of alveolar ducts and to an alteration of lung distensibility. Comparison of the dose-response curves for the different parameters indicated that Cdyn and G reflect, at least in part, events occurring in the periphery of the lung.

Animals↗
PubMedDate not supplied

[Mechanical properties of the lung in paraquat-poisoned rats. Histopathologic correlates].

Paraquat intoxication in both the initial and late stages is responsible for a decrease in lung volumes and lung elasticity. In this study, we tried to separate these two stages with analysing the quasi-static pressure-volume curves (P-V) obtained both during inflation and deflation of the lungs. Three groups of rats were studied: group I: control (n = 9), group II: 11 animals studied 48 h after intraperitoneal injection of paraquat (24 mg X kg-1), group III: 6 animals studied 9 days after the administration of paraquat. Groups II and III, when compared to group I, were characterized by a significant decrease of 1) functional residual capacity (p less than 0.001), 2) the lung volume obtained for a 3 kPa distending pressure, and 3) the slope of the P-V curve during deflation (p less than 0.001). In group II, there was a clear increase in the hysteresis of the P-V loop due to an inflection of the inflation P-V limb. Such a shape is the only characteristic of the P-V curves which separates groups II and III. By contrast, the P-V curve during deflation, even when analysed with an exponential fitting, does not separate these two groups which were clearly different in their morphological aspect: alveolar edema (group II), interstitial pneumonitis (group III).

Animals↗
PubMedDate not supplied

[Plethysmographic measurement of lung volume in chronic obstructive pulmonary disease. Influence of the panting pattern].

In 9 healthy subjects and 22 patients with chronic obstructive disease, we computed total lung capacity (TLC) using an integrated flow pressure-corrected body plethysmograph. During panting manoeuvre, TLC derived from oesophageal pressure (TLCes) was compared to TLC derived from mouth pressure (TLCm). In healthy subjects, TLCm was identical to TLCes. Patients with obstructive disease exhibited different behaviours according to experimental conditions: a) in free frequency panting with mouth occlusion close to functional residual capacity (FRC) (9 patients), TLCm appeared to be significantly higher than TLCes (mean difference: 0.25 1; p less than 0.05); b) in panting with both low (less than 1 Hz) and high (2 Hz) frequencies and mouth occlusion close to FRC (7 patients), TLCm appeared to be significantly higher than TLCes only at a high frequency (p less than 0.05); c) in panting with both low and high frequencies and mouth occlusion close to TLC (6 patients), no significant difference was observed between TLCm and TLCes. These results suggest that in patients with chronic obstructive disease plethysmographic lung volume measurements are subject to error, due to the influence of extrathoracic airways. During occlusion at FRC, panting frequency was found to influence the results obtained, the error being minimized with low frequencies. In contrast, by occluding at TLC, we found that panting frequency was less likely to influence the results. However, potential sources of error still exist: for instance, the influence of abdominal gas or the panting pattern.

Adult↗
PubMedDate not supplied

[Estimation of intrapulmonary shunt in resuscitation (use of a nomogram) (author's transl)].

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.

Carbon Dioxide↗