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Cytokine production by cord blood lymphocytes
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Ventilation!perfusionratioand cardiovascular respome to high-frequency positive pressure ventilation in neonates with severe respiratory failure. Oleg B. Milenin, Department of Neonatology, Central Institute for Advanced Medical Studies, Barrikadnaja 2, Moscow 123836 (Russian Federation). This study evaluated ventilation/perfusion ratio and cardio-vascular response to high-frequency positive pressure ventilation in neonates. Thirty-one infants less than 7 days old were enrolled who were: more than 30 weeks gestation, weighed between 1300 and 4000 g and were ventilated for respiratory distress syndrome (RDS) or MAS. After normahsing blood gases with conventional intermittent positive pressure ventilation (IPPV) haemodynamic values were measured and high frequency positive pressure ventilation (HFPPV) was started at settings adequate to maintain normal blood gases. Sixty minutes later haemodynamic vaiues were remeasured. No sedatives, muscle relaxants or cardiovascular drugs were administered. The ventilation/perfusion ratio was evaluated using the A-aDQ2 and veno-arterial shunt (Qs/Qt). Haemodynamic values were evaluated by echocardiography, colour flow mapping and pulsed Doppler with a 5.0-MHz annular phased array probe. HFPPV at 117 (SE 4)/min versus IPPV at 44 (SE Z)/min allowed the peak pressure to be reduced from 2.74 (SE 0.07) kP, to 2.22 (SE 0.09) kP, (P < 0.01) and mean airway pressure from 1.19 (SE 0.04) kP, to 0.98 (SE 0.04) kP, (P < 0.01) without changing FIO, or positive end-expiratory pressure (PEEP). This was followed by a significant decrease of the right ventilation preejection period/right ventricular ejection time ratio (RPEPIRVET), reflecting the increased preload and decreased afterload of the right ventricle with HFPPV. As a result stroke volume and cardiac output increased significantly. A positive cardiovascular response to HFPPV was seen more distinctly in infants with hypovolemia and pulmonary hypertension. In 21 infants with a closed ductus arteriosus A-aDQ2 and Qs/Qt were not affected with HFPPV. In 10 infants with a PDA these values increased significantly, reflecting predominance of perfusion over ventilation. To decrease the pulmonary vascular bed overload in these babies during HFPPV the PEEP was increased. In conclusion, HFPPV provides adequate gas exchange with the lower positive inspiratory pressure (PIP) and mean airway pressure (MAP) compared with conventional IPPV and reduces the harmful effects of mechanical ventilation on the cardiovascular system. In infants with PDA an optimal ventilation/perfusion ratio may be achieved with a low PIP by increasing PEEP.
Cytokine production by cord blood lymphocytes. C.A. Michie, D. Harvey and P.C.L. Beverley, Queen
Charlotte’s and Che1se.a Hospital, London W6 (UK). Neonatal responses to infection and immunisation differ from those in adults both qualitatively and quantitatively. Cytokine secretion by lymphocyes is central to the immune response. A reverse haemolytic plaque assay has been developed to measure the frequency of lymphocytes secreting IL-2, IL-4, IL-6, IFNy, TNF-a and Rantes. The technique has been used to compare cytokine secretion by cord blood T lymphocytes (five term infant cords sampled) with subsets of adult lymphocytes: CD45RA+ve T cells (or ‘naive’ lymphocytes) and CWSRO+ve T cells (‘memory’ lymphocytes; five individuals sampled). These subsets were selected as cord blood lymphocytes are antigenically ‘naive’and are all CD45RA+ve. Lymphocytes were activated with mitogen or antibodies to CD2, CD3 and CD28, or combinations of these antibodies. We observed distinct behaviour from cord blood lymphocyte populations: only IL-2 could be secreted in response to any stimulus. By contrast a low frequency of adult ‘naive’ cells secrete IFN-y by 48 h (4% f 1.5% S.D.); adult ‘memory’ lymphocytes secrete all the cytokines by 24-36 h. However, cord blood T lymphocytes secrete IL-2 as rapidly as either adult ‘naive’ or adult ‘memory’ lymphocytes, with a maximal frequency of 24% ( f 2.3% S.D.) at 36 h. These differences in cytokine production will contribute to differences observed clinically in neonatal immune responses.
Dilution kinetics of H2’8O for tbe estimation of total body water in preterm babies in tbe fit week after birth. Wing Tanga, Neena Media and Peter Clark b, sDepartment of Paediatrics Royal Postgraduate Medical School, Du Cane Road, London W12 ONN, and bDepartment of Medical Physics, Royal Postgraduate Medical School, Du Cane Road, London W12 ONN (UK).
Ventilation!perfusionratioand cardiovascular respome to high-frequency positive pressure ventilation in neonates with severe respiratory failure. Oleg B. Milenin, Department of Neonatology, Central Institute for Advanced Medical Studies, Barrikadnaja 2, Moscow 123836 (Russian Federation). This study evaluated ventilation/perfusion ratio and cardio-vascular response to high-frequency positive pressure ventilation in neonates. Thirty-one infants less than 7 days old were enrolled who were: more than 30 weeks gestation, weighed between 1300 and 4000 g and were ventilated for respiratory distress syndrome (RDS) or MAS. After normahsing blood gases with conventional intermittent positive pressure ventilation (IPPV) haemodynamic values were measured and high frequency positive pressure ventilation (HFPPV) was started at settings adequate to maintain normal blood gases. Sixty minutes later haemodynamic vaiues were remeasured. No sedatives, muscle relaxants or cardiovascular drugs were administered. The ventilation/perfusion ratio was evaluated using the A-aDQ2 and veno-arterial shunt (Qs/Qt). Haemodynamic values were evaluated by echocardiography, colour flow mapping and pulsed Doppler with a 5.0-MHz annular phased array probe. HFPPV at 117 (SE 4)/min versus IPPV at 44 (SE Z)/min allowed the peak pressure to be reduced from 2.74 (SE 0.07) kP, to 2.22 (SE 0.09) kP, (P < 0.01) and mean airway pressure from 1.19 (SE 0.04) kP, to 0.98 (SE 0.04) kP, (P < 0.01) without changing FIO, or positive end-expiratory pressure (PEEP). This was followed by a significant decrease of the right ventilation preejection period/right ventricular ejection time ratio (RPEPIRVET), reflecting the increased preload and decreased afterload of the right ventricle with HFPPV. As a result stroke volume and cardiac output increased significantly. A positive cardiovascular response to HFPPV was seen more distinctly in infants with hypovolemia and pulmonary hypertension. In 21 infants with a closed ductus arteriosus A-aDQ2 and Qs/Qt were not affected with HFPPV. In 10 infants with a PDA these values increased significantly, reflecting predominance of perfusion over ventilation. To decrease the pulmonary vascular bed overload in these babies during HFPPV the PEEP was increased. In conclusion, HFPPV provides adequate gas exchange with the lower positive inspiratory pressure (PIP) and mean airway pressure (MAP) compared with conventional IPPV and reduces the harmful effects of mechanical ventilation on the cardiovascular system. In infants with PDA an optimal ventilation/perfusion ratio may be achieved with a low PIP by increasing PEEP.
Cytokine production by cord blood lymphocytes. C.A. Michie, D. Harvey and P.C.L. Beverley, Queen
Charlotte’s and Che1se.a Hospital, London W6 (UK). Neonatal responses to infection and immunisation differ from those in adults both qualitatively and quantitatively. Cytokine secretion by lymphocyes is central to the immune response. A reverse haemolytic plaque assay has been developed to measure the frequency of lymphocytes secreting IL-2, IL-4, IL-6, IFNy, TNF-a and Rantes. The technique has been used to compare cytokine secretion by cord blood T lymphocytes (five term infant cords sampled) with subsets of adult lymphocytes: CD45RA+ve T cells (or ‘naive’ lymphocytes) and CWSRO+ve T cells (‘memory’ lymphocytes; five individuals sampled). These subsets were selected as cord blood lymphocytes are antigenically ‘naive’and are all CD45RA+ve. Lymphocytes were activated with mitogen or antibodies to CD2, CD3 and CD28, or combinations of these antibodies. We observed distinct behaviour from cord blood lymphocyte populations: only IL-2 could be secreted in response to any stimulus. By contrast a low frequency of adult ‘naive’ cells secrete IFN-y by 48 h (4% f 1.5% S.D.); adult ‘memory’ lymphocytes secrete all the cytokines by 24-36 h. However, cord blood T lymphocytes secrete IL-2 as rapidly as either adult ‘naive’ or adult ‘memory’ lymphocytes, with a maximal frequency of 24% ( f 2.3% S.D.) at 36 h. These differences in cytokine production will contribute to differences observed clinically in neonatal immune responses.
Dilution kinetics of H2’8O for tbe estimation of total body water in preterm babies in tbe fit week after birth. Wing Tanga, Neena Media and Peter Clark b, sDepartment of Paediatrics Royal Postgraduate Medical School, Du Cane Road, London W12 ONN, and bDepartment of Medical Physics, Royal Postgraduate Medical School, Du Cane Road, London W12 ONN (UK).