Bulletin de physio-pathologie respiratoire最新文献

A device that allows continuous monitoring and recording of expired minute volume, tidal volume, resistance, compliance, indices of hyperinflation and other measures of ventilation and lung mechanics during automatic ventilation is described. After connection to the ventilator (Servoventilator 900) with one cable it is operating without any calibrations or other measures. The calculation of expired minute volume is done in a new way that eliminates errors due to compression of gas in the connecting lines. Calculations of compliance is made in a way allowing measurements even in patients with hyperinflation. Expiratory and inspiratory resistance values are obtained. The indices of hyperinflation in terms of measured flow and estimated alveolar pressure at the end of an expiration are discussed. The problems and benefits associated with measurements in much obstructive patients are analyzed. A short study of the performance of the calculator is presented.

In 85 patinets withstatus asthmaticus, the authors have studied the acid-base balance, the blood gas tensions and various humoral parameters. The values were classified into two groups according to the PaCO2 level: below or equal to 44 torr (Group I), higher than 44 torr (Group II). In the 58 cases of Group II, there was a very close positive correlation between PaCO2 and H + ions, practically the same as that established by BRACKETT et al. [3] in experimental acute hypercapnia in man. On the contrary, the correlation derived from cases of status asthmaticus in the literature showed, in some cases, a metabolic component in acidosis. In the present work, the mean value of lactates was close to normal; there was a slow increase in protein content and hematocrit, in the two groups. The prognosis of the status asthmaticus depends on the degrees of hypercapnia: when it reaches 70 torr, mechanical ventilation is urgently needed and is the main part of the treatment; the use of additional drugs remains a matter of specific case.

Study of ventilatory mechanics implies collection of input variables (stresses estimated by pressures) and output variables (strains), from which the parameters (compliance, resistance, etc.) of a model reproducing the functioning system can be computed. From this point of view, patients under artificial ventilation show a twofold difficulty: the one is the collection of variables, very difficult in consideration of the patients' precarious state, the other the type of the model: the first order linear model, used for lack of better solution, can be criticized, on the one hand by severe pulmonary changes in these patients, and by the special mode of applying constraints during artificial ventilation on the other. All these facts explain the methodologic and theoretical difficulties encountered in ventilatory mechanics analysis in resuscitation, which actually leads to the expression of one parameter as representative of the pulmonary parenchymal elasticity: the static compliance, and to the determination of the balancing point of the system: the functional residual capacity.

The study of fluid and electrolyte disturbances by isotope radiodilution method is carried out in 22 patients with chronic respiratory insufficiency and cardiac failure. The simultaneous measurements of hydro-ionic compartments have been carried out with tritiated water (HTO), labelled sodium (22Na), labelled potassium (42K) and labelled bromine (82Br). From these measurements, the various water spaces are calculated: total water (ET) and extracellular fluids (LEC), also exchangeable electrolytes: sodium (NaE), potassium (KE), chlorine (ClE) and derived values. Results are compared to corresponding values in controls with the same obesity index. Patients with respiratory insufficiency show a fluid and sodium rise, similar to that found in cardiac failure and denutrition. The (NaE + KE)/ET ratio is not significantly decreased and the natremia is only slightly lower. There is no real potassium depletion in most patients.

The amount of oxygen made available to the tissues of the body depends essentially upon pulmonary gas exchanges, cardiac output and its regional distribution, haemoglobin concentration and also upon the oxygen affinity of the haemoglobin molecule. That a standard oxyhaemoglobin dissociation curve faithfully describes oxygen loading and unloading both in healthy subjects and in those suffering from pathological process has come under attack. Beside the effect of pH, PCO2 and temperature, the oxyhaemoglobin dissociation curve can be modified by alterations of other factors (concentration of 2,3-diphosphoglycerate, hormones, drugs). Although the shifts of the oxyhaemoglobin dissociation curve, expressed by variations of P50 may seem minute, the effect of these shifts, expressed in terms of the "functional value of haemoglobin" are very large. Assessment of the intensive care patient must take into account the effect of alterations of the oxyhaemoglobin dissociation curve which can either increase or diminish tissue oxygenation.

This work sums up several studies: clinical observation (electrocardiogram, cardiac rhythm, circulatory state), and biology (glycemia, blood oxygenation, acid-base balance) in 24 cases of accidental hypothermia, not related to poisoning by central nervous system depressive agents; haemodynamics in 18 of these cases; pathology of the myocardium in 11 cases; haemodynamics and microscopy of the myocardium in dogs with slowly induced or prolonged hypothermia; finally an electron microscope study in hypothermic rats. Electrocardiographic study and continuous monitoring of cardiac rhythm and tracing show, in addition to well known manifestations (bradycardia, lenghtening of QT, J wave), acute dysrhythmias, particularly circulatory arrests by asystole during or even 72 hours after rewarming. The clinical haemodynamic changes, measurable (cardiac output, mean arterial pressure, central venous pressure), or computable (stroke volume, peripheral resistances) are observed during rewarming. Several haemodynamic developments can be distinguished: --favourable evolution when the initial disturbances (decrease in cardiac output and in stroke volume, increase in peripheral resistances) disappear without any therapeutic support: --haemodynamic developments showing at a certain time evidence of hypovolemia requiring only moderate vascular replacement; --haemodynamic developments showing myocardial damage. In some cases, only hypothermia accounts for these. In circulatory arrests during or after rewarming, these haemodynamic disturbances raise the hypothesis of severe cardiac changes due to hypothermia itself.