Biomedical subjects
Publications and source records attributed to C Chopin.
The authors describe a new device for weaning from mechanical ventilation, based on continuous measurement of end-expiratory concentration of CO 2 (FCO 2 ET). The spontaneous or controlled mode of ventilation is automatically determined by the level of FCO 2 ET in relation to preselected maximum and minimum thresholds. The authors call this device "CO 2MV".
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Angiotensin-converting enzyme (ACE) levels, complement activation, and intravascular coagulation were studied in 36 patients with adult respiratory distress syndrome (ARDS) (17 aseptic, 19 septic), in order to investigate the possible interrelations among ACE, immunologic data, and hematologic findings. The severity of respiratory impairment was assessed with measurements of mechanical and gas exchange functional qualities of the lung. Serial measurements of ACE could be done in 14 patients during an eight-day period. During the first 24 hours, ACE levels were always normal (38 percent) or decreased (62 percent). No difference could be found between patients with septic and aseptic ARDS. Complement activation occurred in 78 percent (28/36) and used, in most cases, the classic pathway with presence of circulating immune complexes. Criteria for intravascular coagulation were present in 58 percent (21/36). No relation between coagulation, complement, and ACE could be found except for the patients with a greater respiratory impairment, who had complement activation, intravascular coagulation, and significantly lower ACE levels. In all patients together, ACE levels had no diagnostic value for aseptic cause of ARDS and a poor prognostic value. Only intravascular coagulation was linked with a higher significant mortality and a greater functional impairment. Serial measurements showed a diphasic evolution of ACE levels, with a maximum decrease between the 72nd and 96th hours and a further normalization (seventh day). The persistence of low levels seemed to be associated with evolutive sepsis or secondary aggravation and fibrosis.
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Patients hospitalized in critical care unit for acute renal failure (ARF) in a multiorgan failure syndrome have often a poor intra-dialysis tolerance. Change from Ac to Bi for dialysate buffering has been advocated to improve this dialytic tolerance. In a retrospective study, 70 patients who received Bi hemodialysis are compared with 106 patients who received Ac hemodialysis. If the mortality is not different between these two groups, intra-dialysis tolerance is significantly better (p less than 0.001) in the Bi group according to the mean intra-dialysis systolic blood pressure decrease, the collapse occurrence and the mean vascular volume infusion. Ultrafiltration rate is higher and reach more often the desired values. On a biochemical point of view, hemodialysis efficacy is the same in the two groups according to urea and creatinin clearance, but end dialysis Bi plasma concentrations are higher and nearer of the normal range in the Bi group even though predialysis Bi plasma concentrations were similar. The only side effect observed with Bi dialysis was a hypoglycemic episode without clinical consequence, due to the lack of glucose in the bicarbonate dialysate. Nevertheless, in patients under controlled ventilation, a end dialysis alkalosis can occur if a hyperventilation is imposed. Change from Ac to Bi in dialysate buffering improves the intra-dialysis tolerance of patients with ARF in a multiorgan failure syndrome. This kind of hemodialysis is now used routinely in our critical care unit.
285 patients affected by carbon monoxide poisoning were admitted in our intensive care unit over a period of two years (from july 1980 to july 1982). 18 patients had a pulmonary edema (P.E.). The occurrence of P.E. was more frequent when coma was grade 2, 3 or 4 (p less than 10(-3]. The acute physiologic score (weighting of physiologic measurements) as proposed by Knauss is higher in patients with P.E. (p less than 10(-2]. However death is never due to P.E.; about 54 patients with coma, 5 died; death is related to neurologic aggravation. Neurologic sequelae are not related to the occurrence of P.E. but to a delay in hyperbaric oxygen therapy. These date show that prognosis of carbon monoxide poisoning is related to neurological status and is not influenced by the occurrence of P.E. when correctly treated and when hyperbaric oxygen therapy is early realized.
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We have studied the hemodynamic effects of an intravenous single dose of nitroglycerin in 13 patients with secondary pulmonary hypertension and Cor Pulmonale, during the acute course of respiratory failure and under assisted ventilation. We observed a significant decrease in systolic, diastolic and mean pulmonary arterial pressures, and in pulmonary resistance and systolic right ventricular work index, without any change in right or left pre-loads. The systolic arterial pressure decreased slightly, without any change in cardiac index or diastolic pressure. The arterial and mixed venous oxygen contents, and the pulmonary shunting ( Qs/Qt) were unchanged. These results suggest that nitroglycerin may be a useful therapy in patients in the acute stages of pulmonary hypertension resulting from chronic lung disease and under assisted ventilation. In addition, the lack of change in cardiac index, intrapulmonary shunting and oxygen content suggests that this decrease in pulmonary resistance is not linked with any deleterious effect in oxygen transfer.
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In 12 patients suffering from the Guillain-Barré syndrome, with autonomic dysfunction, a hemodynamic study was performed and biological counts of neurotransmitter metabolites were repeatedly taken in the urine, the plasma and the lumber cerebrospinal fluid. In the course of the Guillain-Barré syndrome with autonomic dysfunction the changes in hemodynamic indices suggest a state of sympathetic hyperactivity. There is an increase in cerebrospinal neurotransmitter metabolite levels with an increase in central cathecholaminergic and serotoninergic activity. The findings point to an interference of central structures in the sympathetic hyperactivity observed.
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