OBJECTIVES:Besides its vasodilative actions, nitric oxide (NO) is also involved in host defense on a cellular level. We studied the antimicrobial properties of NO in concentrations used with inhaled NO therapy for the treatment of pulmonary hypertension in neonates.DESIGN:In vitro study of bacterial growth of five species, with and without NO exposure.SETTING:Level IV neonatal intensive care unit at a university children's hospital.SUBJECTS:In vitro bacterial cultures.INTERVENTIONS:We tested ten different strains of five bacterial species (Staphylococcus aureus, Staphylococcus epidermidis, group B streptococcus [GBS/Streptococcus agalactiae], Escherichia coli, and Pseudomonas aeruginosa), derived from the tracheal isolates of ventilated premature and term infants. Cultures were exposed to three different concentrations of NO (40, 80, and 120 parts per million [ppm]) and bacterial growth was compared with the same strains incubated in ambient air for 24 hrs. After incubation (with or without NO), colony-forming units were counted.MEASUREMENTS AND MAIN RESULTS:Bacterial growth of S. aureus, E. coli, and P. aeruginosa was not reduced with the NO concentrations applied. The number of colony-forming units of S. aureus increased at 80 ppm of NO. Growth of S. epidermidis and GBS was significantly affected at 120 ppm, resulting in decreased numbers of colony-forming units as compared with controls exposed to ambient air.CONCLUSIONS:We conclude that NO has a selective bacteriostatic effect on some of those bacteria most commonly cultured in tracheal specimens of premature infants and neonates. This effect appears to be dose-dependent and occurs in the upper range of dosages used with inhaled NO therapy. However, in the range of dosages applied in ongoing controlled trials of inhaled NO in neonates and premature infants (1 to 80 ppm), a bacteriostatic effect of NO is not to be expected.

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.