Fluctuations of inspiratory concentration of nitric oxide (NO) during mechanical ventilation
© Current Science Ltd 1997
Published: 1 March 1997
To test inspiratory NO concentrations along the inspiratory limb of the respiratory circuit during mechanical ventilation with different inhaled NO concentrations.
A Servo 300 NO-A prototype (Siemens-Servotek, Solna, Sweden) was used for controlled mechanical ventilation of an artificial test lung with a filling volume of 1 l at an FiO2 of 1.0. Different NO concentrations of 0.1, 1, 10 and 100 ppm (NOin) were applied. In the Servo 300 NO-A a digital controlled valve is used allowing the exact flow-proportional admixture of NO into the inspiratory gas stream. NO is delivered from an NO tank with a fixed concentration dissolved in N2. NO was measured by chemiluminescence (CLD 700 AL, Eco Physics, Duernten, Switzerland) at four different positions (Pos 1–4) along the inspiratory limb of standard respiratory tubing including an active heating system (Concha Therm III with Aerodyne humidification column. Kendall, Neustadt, Germany). Pos 1: immediately behind the respirator's inspiratory outlet: Pos 2: immediately behind the heating column: Pos 3: in the middle between the heating column and the y-piece: Pos 4: immediately before the y-piece.
The results for the NO measurements at the different positions are shown in the figure (left hand side) for the different inhaled NO concentrations. Values are shown as a percentage of NOin. NO2 concentrations in ppm are shown in the figure (right hand side) for the different NOin.
This study was in part supported by DFG: Fa139/4-l.