Meconium aspiration syndrome--a 21-years' experience from a tertiary care center and analysis of risk factors for predicting disease severity.

Aim of this study was to describe the course of perinatal factors in neonates with meconium aspiration syndrome (MAS) from 1990 to 2010 and to determine risk factors for a severe course of the disease.All neonates with MAS hospitalized in our level III neonatal intensive care unit from 1990 to 2010.Retrospective analysis of trends of perinatal factors in neonates with MAS over time and of the association of these factors with severe MAS (need for invasive mechanical ventilation for ≥7 days, or need for high frequency oscillation or need for extracorporeal membrane oxygenation).We included 205 neonates with MAS, 55 had severe MAS (27%). MAS incidence and absolute number of MAS cases per year decreased during the observation period (p=0.003 and 0.005, respectively) as well as rates of outborn deliveries (p=0.004), duration of invasive mechanical ventilation (p=0.004), and hospital stay (p=0.036). Incidence and absolute number of severe MAS cases per year decreased (p=0.008 and 0.006, respectively), though the percentage of severe MAS among all neonates with MAS did not change. Risk factors for severe MAS were acute tocolysis (odds ratio 18.2 (95% confidence interval 2.1-155.3), p<0.001) fetal distress (3.4 (1.8-6.4), p<0.001), and severe and moderate birth asphyxia (4.4 (2.0-9.7), p=0.001 and 2.9 (1.5-5.6), p=0.009).The incidence and absolute numbers of MAS and severe MAS cases changed during the study period as well as neonatal management. Acute tocolysis, fetal distress, and asphyxia were associated with severe MAS.

Ventilation in dogs on cardiopulmonary bypass with and without lungs.

In 13 anesthetized or awake dogs, on cardiopulmonary bypass, we varied PaO2 and PaCO2 while continuously monitoring ventilatory responses and mechanics, to assess the dog's ability to maintain eupneic ventilation for any chemical drive. In a second group of 13 dogs on cardiopulmonary bypass we repeated the tests after removal of both lungs, to assess the importance of pulmonary feedback and mechanics. The VE/PO2 plot formed two hyperbolas, asymptotic to 39 Torr PO2 with lungs, and to 27 without; both intercepted zero ventilation near 200 Torr. Hyperoxic apnea occurred at, or below, PCO2 30 +/- 7 Torr under barbiturate and 20 +/- 4 Torr under morphine. Steady-state low PCO2 (10 Torr) turned off hypoxic drives as low as 20 Torr PO2. Empty-chest dogs had a low respiratory frequency (18 vs. 40), and near zero dynamic elastance; ventilatory work per minute and airway resistance were the same with and without lungs. Chest wall ventilatory responses are grossly independent of the presence of absence of lungs.

Continuous in vivo measurement of arterial PO2 in humans.

A system suitable for prolonged continuous in vivo measurement of human arterial PO2 is described. The system uses a polarographic electrode developed by Kimmich and Kreuzer, inserted in a specially made shunt between the radial artery and an antecubital vein. Nhe electrode surface is maintained in a fixed position parallel to the flow of blood; blood velocity dependency is small owing to the high flow rate achieved (more than 40 cm/s); clotting is prevented by the material used and the continuous instillation of heparin through the arterial end of the shunt. The system has been tested in vitro; it is stable (variation less than 0.5% in 24 h), linear and precise (plus or minus 0.2%) in a broad range of PO2 values (from about 10 mmHg to more than 700 mmHg); its response time is 0.4 s per 95% of deflection. It has been applied to 35 patients for periods ranging between 6 and 24 h; most of the patients were ventilated by an Engstrom respirator.