PubMed Health⌕ Search

Biomedical subjects

C Prefaut

Publications and source records attributed to C Prefaut.

47 records · Page 3Linked to original sources
PubMed1976

Relationships between eupnoeic pattern of breathing and ventilatory control in man II. Early response to transient hypercapnia.

The individual importance of peripheral chemosensitive afferents was studied using a transient hypercapnia (inhalation of a 5% or a 10% CO2 in air gas mixture respectively during 4 or 2 breaths) in human conscious subjects chosen for their different eupnoeic ventilatory patterns. Calculation of the speed of change in end-tidal CO2 pressure in tracheal gas (sPETCO2) and of the rate of change in tidal volume (sVI) gave assessment for quantifying the sensitivity of arterial chemoreceptors to hypercapnia (sCO2=SVI/SPETCO2). Our results showed that, independently of any outside influence of the eupnoeic ventilatory pattern on the components of the chemical stimulus, sVI and sCO2 were found to be much smaller in subjects whose pattern of breathing was slow (i.e. having a large tidal volume). The possible causes of the weak importance of peripheral chemosensitive afferents in such subjects were discussed.

Adolescent↗
PubMed1976

[Effect of low lung volume ventilation on the relative proportions of carbon monoxide partial ductances (author's transl)].

Lacoste has shown the interest of determination of overall ductance of CO and partial expired alveolar ductance and arterio-alveolar partial ductances in the assessment of the efficacy of gaseous exchanges in the lung. DuCO was, by definition, the product : DuACO X DuaCO, the increase in partial ductance may theoretically compensate reduction in the other, the overall ductance then remains normal. This theory was verified studying the effects of low lung volume ventilation. Under these conditions, the dead space series becomes reduced and the DuACO should increase at the same rate, for ventilation occurs at the level of the closing volume. The inspired air is then directed preferentially towards the lung apices. These artificial changes in distribution of ventilation should produce a reduction in DuaCO. The measurements carried out confirmed these theories during low lung volume ventilation ; whereas the differences observed in overall ductance were not significant, those observed on partial ductance were very definitely significant. It appears that isolated measurement of overall ductance is insufficient and may lead to misdiagnosis of a change in the lung exchanges.

Adult↗
PubMedDate not supplied

Immunologic and genetic factors predisposing to allergy.

Allergy often begins with a subtle and/or transient T cell defect. This defect is first responsible for an IgA deficiency. The normal function of IgA is immune exclusion. In its absence, allergens can pass through the mucosa and stimulate the immunocompetent cells. The T cell defect may also be implied by the synthesis of IgE directed against the allergens which passed through. Clinical, biological and immunological findings (T cell defect in allergic disease, low range of IgA in the early life of atopics) are in agreement. The genetic factor for pollinosis and house dust allergy are segregated. In ragweed allergy there is an Ir gene coding for antigen-specific Ig of different classes and a group of non-linked major histocompatibility complex alleles coding for non antigen-specific IgE. There are some links with HLA. In house dust allergy the Ir gene is very common and almost everyone can produce an allergy under some conditions (T cell defect). Whatever the immunologic and genetic factors are, they need allergens and environmental factors to induce allergy. Allergy is a complex state in which several mechanisms, often associated and sometimes unclear, are involved. Some of them may be an abnormality of the autonomic nervous system, and/or an increase in the mucous membrane permeability, and/or a subtle immunodeficiency. All these mechanisms are regulated by genetic factors and modulated by environmental ones.

Environment↗