Infants with very low birth weight (VLBW) and respiratory disease have dominated neonatal intensive care units during recent decades. However, the pattern of morbidity has changed lately, and both the severity of the lung disorders and the number of sick neonates are decreasing. Improved pre- and postnatal care with increased use of prenatal maternal steroid treatment, exogenous surfactant, improved ventilatory techniques and methods for extracorporeal gas exchange are factors that might contribute to the change in both morbidity and mortality of newborn infants.

L.G. Thijs (Netherlands)*(~) G. Baltopoulos (Greece) 9 D. Bihari (UK) H. Burchardi (Germany) 9 J. Cartet (France)" R. Chiolbro (Switzerland) L. Dragsted (Denmark) ' DJ. Edwards (UK) ' P. Ferdinande (Belgium) ' F. Giunta (Italy)" A. Karl (Finland). W. Kox (Germany). M. Planas (Spain) J.L. Vincent (Belgium) J. Pfenninger (Switzerland) ' K.E. Edberg (Sweden)D. Floret (France). M. Leijala (Finland) . F.K. Tegtmeyer (Germany)

Introduction: Nitric oxide innalational therapy requires a dosage unit, consisting of flow controlllers for bias and NO flow as well as NO and NO, monitoring devices.Aim Of the study: We examined the accuracy Of each component as well as the accuracy Of the complete system in combination with a high frequency oscillatory ventilator (HFO-V).Materials and Methods: We Compared accuracy Of digital mass flow controllers IMFC) (BrOnkhorst Hi-Tec, Veenendaal, The Netherlands) versus Conventional analog flow controllers (Brooks Europe, Veenendaal, The Netherlands) for NO and biasFloW control.NO and NO, concentrations were measured With Chemiluminescence (CLD 700, EcoPhysics, DUrnten, Switserland) in dry gas containing 21% oxygen.Furthermore accuracy of NO measurement in clinical Conditions was assessed, with NO and bias flow MFC controlled.NO and NO, concentrations were measured using both ChemiluminescenCe (CLD 700) and electrochemical analysers (SensorNOx, Sensor Medics Europe, Bilthoven, The Netherlands).The HFO-V ventilator used was a Sensor Medics 3100-A (Sensor Medics, Yorba Linda, Ca).Results: We found major influences of used flow controllers, humidification, and measurement method used.Data are presented in the table as mean (95%Cl limits) Of the ratio Of pre-calculated to measured NO value.Dosage accuracy (Cnemiluminescence) 2 MFC 0.99 (0.983-0.998) 3100 A biasfiow, MFC (NO) 0.856 (0.835-0.877) 3100 A biasflow, rotameter (NO) 1.175 (0.793-1.74)Measurement accuracy 12 MFC) electrochemical, dry gas 1.017 (1.006-1.029)electrochemical, humid gas 1.131 (1.089-1.175)chemoluminescence, humid gas 1.136 (1.126-1.136) Conclusions:We conclude, that a system consisting of one MFC for NO dosage, rotameter for biasflOw control and electrochemical NO and NO, analyser has adequate accuracy for clinical use during HFO-V.Our electrochemical analyser uses a cell, with limited sensitivity to high oxygen levels, sampled gas was dried via permapure tubing and pressure swings were not allowed to reach the analyser.

A single compartment model has been used to describe the dynamic respiratory mechanics in 21 newborn infants. The subjects were intubated and studied during mechanical ventilation. A whole-body plethysmograph was used to record the ventilatory flow. The estimated resistance and compliance values of the respiratory system have been compensated for the effect of alveolar gas compression. The average compensated resistance value was 11% lower than the uncompensated value and the average compensated compliance value was 6% higher than the uncompensated value.