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Biomedical subjects

C Hatzfeld

Publications and source records attributed to C Hatzfeld.

15 recordsLinked to original sources
PubMed1990

Ventilatory adjustments during sustained resistive unloading in exercising humans.

Effect of He-O2-breathing (79.1%:20.9%) compared to air-breathing on inspiratory ventilation (VI) and its different components [tidal volume (VT), the duration of the phases of each respiratory cycle (tI, tTOT)] as well as on inspiratory mouth occlusion pressure (P0.1) were studied in six normal men at rest and during 72 constant-load exercises (90 W) over a much longer period than in previous studies. Results showed that, irrespective of the order of administration of the two gases (7 min air----7 min He-O2 or vice versa): at rest, P0.1 decreased during He-O2 inhalation but no changes in VI and breathing pattern were detectable; during exercise, sustained He-induced hyperventilation was observed without any change in the absolute value of P0.1; increase in P0.1 between the resting period and exercise (delta P0.1) was significantly higher during He-O2-breathing than during air breathing; this He-induced hyperventilation was associated with a sustained increase in VT/tI, but with constant tI/tTOT. Helium-breathing during exercise cannot be a simple situation of resistance unloading, as has been suggested. We conclude that He-O2-breathing, after the initial compensation period, induces reflex changes in ventilatory control with an increase in inspiratory neural drive. Moreover, it appears that exercise P0.1 is not a legitimate index of inspiratory neural drive whenever rest P0.1 changes according to the nature of the inhaled gas mixture.

Adaptation, Physiological↗
PubMed1989

Transverse images of the human thoracic trachea during forced expiration.

The thoracic trachea and the proximal portion of the major bronchi were imaged in five normal volunteers during a forced expiration maneuver using a cine-computer-tomography system. Sixteen images of two contiguous slices were obtained in less than 1 is while expiratory flow was recorded at the mouth. The area of the thoracic trachea decreased rapidly as flow rate rose to its maximum and the wave of collapse propagated distally. The compressive narrowing of both the pars membranacea and the ventrolateral wall was asymmetric. A contact area appeared between the posterior and the left lateral walls. In one subject the trachea was imaged during the entire maneuver with a lower scan frequency. By 725 ms after the beginning of the forced expiration, the area had first decreased to 15% of its initial value and then reincreased to 46% of its initial value. It stayed constant for the remainder of the maneuver. The measured maximum air velocity was greater than the estimated local wave velocity.

Adult↗
PubMed1977

Three-gas diffusion--experimental and theoretical study.

The purpose of this work was to compare experimental diffusion among three gases with the solution given by Stefan's equations to understand better how this phenomenon can work in the multicomponent alveolar gas. Experiments were performed in a cylinder full of beads open at one end and closed at the other in which a mixture of oxygen with helium or argon or sulphur hexafluoride could diffuse with ambient air through the open end. We solved Stefan's equations for the non-steady state by a finite-difference method and applied them to our experimental conditions with diffusion coefficients we had measured in binary experiments. We then made experiments and calculations to show the influence of the beads on gas transport. Provided that diffusion is the only phenomenon, experimental and theoretical curves are very close together. Moreover beads nearly stop motions due to vortices or small differences of density. We conclude that: Stefan's equations should replace Fick's equations when more than two gases are involved. One should bear in mind the possible influence of gravity and devise diffusion experiments accordingly. In small spaces such as alveoli the influence of gravity must be negligible compared to diffusion.

Diffusion↗
PubMed1977

The determination of dissolved nitrogen in blood by gas phase chromatography.

A method for measuring dissolved nitrogen in blood is described. Gas-phase chromatography is used. The apparatus is provided with a column of 5 A molecular sieve material and with an extraction chamber. CO2 and O2 are absorbed. As in Lenfant's method, extraction by equilibration is completed by elution. The main features are: the design of the extraction chamber, faciliting gas flow; an auxiliary circuit for freeing the chamber and the reagents from nitrogen, in which the pressure can be equilibrated against the inlet pressure of the column; the care taken to avoid any kind of contamination; the use of a special guide mounted on the blood-transfer syringe, which makes it possible to get reproducible samples at last the checking and measurement of the residual nitrogen which makes it possible to extract and measure the whole of the dissolved nitrogen. At the present stage, the accuracy of the method is better than 1.5% and the coefficient of variation of the reproducibility is 0.57%. These results make the method suitable for measuring (PaN2-PAN2) in cases of chronic respiratory insufficiency.

Chromatography, Gas↗
PubMed1975

[Flow rates and pulmonary volumes in athetosis patients with speech disorders].

In 9 controls and in 10 athetosic subjects, authors performed a pneumotachographic registering of ventilation under rest conditions for each phase and determined : the phase duration, the delay between the onset of the phase and the moment where the maximal output occurs, the output reached at the first 1/10th of second after phase change. These determinations were performed in 189 cycles in the controls and in 257 cycles in the athetosic subjects. For each cycle, ventilation and frequency reported to one minute were reckoned, and the relation was established between the duration of expiration and inspiration and between the time necessary for the output to reach its maximal level and the phase duration. The hereafter mentioned facts were noted : in the athetosic subjects there exists a tachypnea for normal ventilation figures, a proportional lengthening in the expiration duration with a reduced mean output; in the beginning of the phase, the output gets increased more rapidly and reaches a higher level than in the controls; then a slow and irregular decrease occurs. Inspiration is rapid and regular. The most perturbed expiration is to be found in the athetosic subjects who exhibit the most severe vocal disorders. These expiratory anomalies appear to be bound with a poor thoracic and laryngeal motor controlling during the passive phase of the respiration, whereas the automatic inspiratory movement takes place in a normal mood.

Athetosis↗
PubMedDate not supplied

[A control trial of home I.P.P.B. therapy in patients with chronic obstructive respiratory insufficiency. Protocol and state of the study (author's transl)].

Because a previous retrospective study did not allow any conclusion as to the efficacy of home IPPB therapy in patients with chronic airflow obstruction, a control trial has been started. The protocol includes definition of patients, modalities of treatment, criteria for evaluation. Among criteria for a patient to enter the trial is a chronic hypercapnia (with PaCO2 greater than or equal to 48 mmHg) observed over a preliminary period of 4 months. At the end of this period patients are allocated at random into two groups with and without IPPB at home (at least 1 to 2 hours daily through a mouthpiece); medical prescriptions are same in the 2 groups so as surveillance which is planned for 2 years. Evaluation should be based upon 5 predetermined criteria. This trial is in progress.

Activities of Daily Living↗
PubMedDate not supplied

[I.P.P.B. therapy at home in chronic respiratory insufficiency in France. I. Survey method. Description of the prescribers. 1960-1977 prescription evolution (author's transl)].

In order to assess the usage of IPPB therapy at home in chronic respiratory insufficiency in France, a mail survey has been conducted among 2,062 chest physicians and physicians involved in intensive care. The response rate was 57%. Among those caring for chronic respiratory insufficient patients, 296, i.e. 38%, have prescribed IPPB to 3,778 patients from 1960 till 1977. A study among a sample of the non-spontaneous-responders allows the estimation of about 400 physicians who prescribed IPPB on the whole for France at this time. Those who prescribed, worked more often in hospital though 4% had only a private practice. Those involved in intensive care prescribed more often than the chest physicians (47% versus 37%). The development of this therapy was different according to the different regions in France. But, in a general way, the prescription of IPPB at home particularly spread out since 1975, 65% of all the prescriptions have been done in 1975, 76, 77.

France↗
PubMedDate not supplied

[IPPB therapy at home in chronic respiratory insufficiency in France. II. Indications. Technics and surveillance (author's transl)].

A survey has been conducted among French chest physicians and physicians involved in intensive care. 296 physicians have prescribed IPPB at home to 3 778 patients with chronic respiratory insufficiency between 1960 and 1977. Acute respiratory failure was the first criteria considered in the indications (57% of the patients); hypercapnia, hypoxemia and right heart failure episode frequency were the other criteria of severity the most often taken into account. Since 1960, the indications among those with airflow obstruction have decreased, whereas they have increased for those with restrictive insufficiencies, expressing the questions raised about the efficacy of IPPB in these two types. 18% of the patients have had IPPB through tracheostomy canula. 70% of the patients have used a pressure cycling respirator and 30% a volume or flow cycling respiratory. This second type was quite always used in the case of IPPB through canula. Oxygen was added for half of the patients. The physicians have regularly followed the patients. Great importance was accorded to home care surveillance.

France↗
PubMedDate not supplied

[Mode of action and results of long-term assisted ventilation at home of chronic respiratory insufficient patients (author's transl)].

It is generally agreed that one assisted ventilation session has direct effects in chronic respiratory insufficiencies (C.R.I.) of chronic obstructive pulmonary diseases: hyperventilation where PaCO2 decreases and PaO2 increases, diminution of ventilatory work, reduction of cardiac output. Less is known, however, about the action on V and Q distribution and mechanics of breathing. The return to control values occurs quite rapidly after the end of the session. Long-term effects are much more questionable. Many publications in English have concluded that ona long-term basis, patients do not benefit from intermittent positive pressure. But, the daily assisted ventilation sessions usually lasted only a short time (1 h-1 h 30 in several sessions). According to a number of publications in French, assistance prolonged for several hours seems effective (decrease in the number of acute failures, annual hospitalization duration, more prolonged survival). However, a tracheostomy which enables assistance at night is often required. Results seem encouraging in the treatment of severe restrictive insufficiencies and particularly in the case of cyphoscoliotic patients. On the other hand, it is more difficult to draw a conclusion concerning chronic obstructive patients and further comparative studies are necessary in this direction.

Airway Obstruction↗
PubMedDate not supplied

[The effect on gas mixing of a He-O2 mixture in chronic obstructive lung diseases (author's transl)].

In order to estimate the role played by gaseous diffusion in the mixing disorders of chronic obstructive lung disease (COLD), the effect of breathing a gas mixture lighter than air has been studied. Twenty four patients with severe airflow obstruction have been tested in the following way: in a random order they breathed two different mixtures with the same PO2 : air and helium-oxygen (heliox) for 20 min. Ventilation was monitored during the whole of each run; during the 2 last min arterial blood was sampled. While breathing heliox a slight, non-significant, increase in ventilation has been observed with a slight but statistically significant decrease of PaO2 (p less than 0.01), of PaCO2 (p less than 0.05) and increase of pH (p less than 0.01). These changes suggest a slight increase of distribution disorders with alveolar hyperventilation. For these results to be consistent with stratification, improvement of the diffusion due to low density should have been masked by other phenomena; the possible effects of ternary diffusion, increased viscous resistances and change of transfer factor have been looked at. No conclusive evidence has been found of such counter-effects. Therefore it looks unlikely that stratification be the major factor in distribution impairment in COLD.

Adult↗
PubMedDate not supplied

[Critical study of a new method for measuring total CO2 in plasma (author transl)].

A new analyser for total CO2 in blood--Ericsen E-100--has been tested and its performances compared with those of the manometric Van Slyke apparatus. Ericsen E-100 makes it possible to measure very small samples (50 microliter) in a short time (35 s). It appears that Ericsen E-100 underestimates total CO2; the higher the total CO2 the larger the error. Simple improvements are suggested, especially concerning the way injection is performed in the reaction chamber.

Blood Gas Analysis↗