A Fossion

Effects of intravascular volume expansion on lung fluid balance in a canine model of septic shock

We tested the early effects of endotoxin on both the permeability of capillary membranes and microvascular pressure. One group of dogs (n = 8) were fluid loaded (30 ml/kg dextran-40) after having been subjected to a 2-h Escherichia coli endotoxin infusion (0.25 micrograms/kg X min). A second control group of animals (n = 6) was submitted to a similar (25 ml/kg) volume loading over an equivalent 30-min period. We estimated extravascular lung water (EVLW), calculated the effective pulmonary capillary pressure, and determined the alveolar-capillary filtration coefficient (Kf) after volume loading. Only the septic animals consistently showed elevated EVLW values consistent with pulmonary edema. The results showed, however, that the Kf calculated for the dogs that received endotoxin was no different from that of control group (Kf = 0.005 ml/kg X min X mm Hg). Instead, endotoxin constricted the pulmonary veins which led to a considerable rise in microvascular hydrostatic pressure above the level at which the lungs could not resist edema formation. We conclude that acute pulmonary edema that follows endotoxin insult and subsequent therapeutic volume replacement is due to an increased filtration force instead of an alteration in the microvascular permeability.

Identification of three-element windkessel model: comparison of time and frequency domain techniques.

The problem of the parameter identification of the three-element windkessel model is studied. Minimization by least-square technique--LSQ--in time domain and frequential techniques--FFT--are compared. Continuous pressure and flow curves were recorded in the proximal aorta of an open chest dog. Comparison shows very high correlations between the parameter estimations obtained by LSQ and FFT methods. However, systematic differences appear between the calculated values, but do not seem to endanger physiological interpretation of the results.

Équivalent énergétique de la production du lactate plasmatique dans la course d'intensité supramaximale

AbstractThe energy equivalent of plasma lactate production (ELAp) represents the amount of energy that can be derived from the anaerobic glycolysis per kg body weight when the peak plasma lactate concentration (LAp) after exercice increases by 1 mM. ELAp has been calculated from the relationship between the oxygen deficit (Do2) and LAp in 32 subjects. LAp and oxygen uptake measurements were made during constant speed supramaximal running untill exhaustion or during the course of constant-speed supramaximal runs of different duration interrupted by 8- to 10- min resting periods. The relationship between Do2 and LAp is described by a linear equation where the slope is equal to ELAp. This equation is: Do2 = 12.3 + 2.4 LAp (r = 0.958; P < 0.001), where Do2 is expressed in ml O2/kg and LAp in mmol/litre (mM). These findings validate LAp measurements as an index of the anaerobic metabolism during supramaximal running.

Effects of Peep on abdominal aortic input impedance

ConclusionThe ratio of mean aortic pressure and mean aortic flow does not completely describe the mechanical properties of the arterial system. Using the impedance spectrum, a shift of the resistances to the small vessels was observed while total resistance and arterial tonus were unchanged during the application of Peep.

Effets du blocage des recepteurs beta-adrenergiques sur l'hyperlactacidemie induite par des exercices d'intensites differentes.

AbstractThe effects of beta-adrenergic blockade on the exercise-induced hyperlactatemia (Lap) have been studied in 31 adult male subjects [age: 25 ± 1 years; body weight: 69 ± 1 kg; ±O2max: 54 ± 1 ml O2. kg−1. min−1 (mean values ± SEM)] randomly divided in 3 groups. All exercises were performed on a 10% inclined treadmill. In group 1 (n= 11), the subjects were walking during 20 minutes at 5 km.h−1 (55.6± 1.4% ±O2max). In group 2 (n = 10), they were running during 9 minutes at 8 km.h−1 (79.4 + 1.5% ±O2max). The subjects of the third group (n= 10) were submitted to a 4 minutes run at 9,5 km.h−1 92 ± 1.6% ±O2max). These exercises were performed 1 hour after ingestion of a placebo or a single dose of 40 mg propranolol, in a double-blind randomized order. Blood samples were drawn at regular time intervals from an antecubital vein.Exercise tachycardia was reduced by about 20% (P < 0.001) by propranolol in each group. Lap was significantly reduced by 15% by propranolol (P < 0.005) at the lowest exercise intensit...