Sven-Gunnar Olsson

Nitric oxide gives maximal response after coronary artery bypass surgery

The dose-response to inhalation of nitric oxide (NO) after coronary artery bypass surgery was studied in seven patients with normal preoperative lung function and chest radiograms. During postoperative controlled ventilation with PEEP 5 and 10 cmH2O, the patients inhaled NO in concentrations of 2 to 25 ppm, in random order, for 6 to 10 minutes. Hemodynamic and oximetric data were analyzed before, 5 minutes after start of the NO inhalation, and 5 minutes after the cessation. The response was the same at all concentrations; mean pulmonary artery pressure decreased by 11 +/- 1% (P < 0.05) and pulmonary vascular resistance decreased by 22 +/- 2% (P < 0.05). Systemic hemodynamics did not change, but oximetric parameters tended to improve. Changes in PEEP did not affect the response. It is concluded that, in patients who have undergone coronary artery bypass grafting, inhalation of 2 to 25 ppm NO causes a dose-independent decrease in pulmonary artery pressure and pulmonary vascular resistance. In order to investigate the dose-response curve, concentrations lower than 2 ppm of NO must be used.

A delivery system for inhalation of nitric oxide evaluated with chemiluminescence, electrochemical fuel cells, and capnography.

OBJECTIVE To evaluate a system for delivery of inhaled nitric oxide. DESIGN Prospective, laboratory study. SETTING Engineering laboratory. SUBJECTS A standard ventilator (Servo Ventilator 300), supplemented with extra gas modules for nitric oxide delivery. INTERVENTIONS Two ventilator-integrated gas modules, delivering < or = 10 parts per million (ppm) or < or = 100 ppm of nitric oxide, were used in adult and neonatal modes during volume-controlled ventilation. Set nitric oxide concentration and FIO2 were systematically changed and compared with the measured concentration. Short-term mixing was tested in adult, pediatric, and neonatal modes by substituting nitric oxide with CO2, and measuring the delivered concentration by a fast-response CO2 analyzer during five successive respiratory cycles. Long-term mixing was tested with the administration of 25 ppm of nitric oxide for 7 days. MEASUREMENTS AND MAIN RESULTS Delivered concentration of nitric oxide and nitrogen dioxide were simultaneously measured at the Y-place by two methods-chemiluminescence and electro-chemical fuel cells. The maximum absolute difference between set and measured concentrations of nitric oxide in the adult mode was 0.6 ppm at a set concentration of 10 ppm and 2.7 ppm at a set concentration of 100 ppm. In the neonatal mode, the maximal difference was 3.1 ppm at a set concentration of 100 ppm. Nitrogen dioxide concentration increased with increasing concentration of nitric oxide and oxygen to 2.6 ppm (as measured by the chemiluminescence analyzer) and 3.6 ppm (as measured by the electro-chemical fuel cell), at a setting of 100 ppm of nitric oxide with an FIO2 of 0.90 in the neonatal mode (2 L/min). During the short-term test of mixing stability throughout the respiratory cycles, a constant set CO2 concentration varied maximally by +/-6.2% from the set value in the neonatal mode, whereas the variance was by +/-6.5% in pediatric mode, and by +/-8.0% in the adult mode. During the long-term test, nitric oxide concentration varied maximally by +/-2.6% (as measured by the chemiluminescence analyzer) and by +/-2.3% (as measured by the electrochemical fuel cell). CONCLUSIONS An accurate precision in delivered nitric oxide concentration was achieved during intermittent flow ventilation, and this accuracy was independent of tested ventilator settings. The delivery system administered an almost stable concentration throughout a respiratory cycle and during long-term delivery. If the mixing point is in the inspiratory part of the ventilator, valid measurement of nitric oxide and nitrogen dioxide delivery concentrations are possible. Both techniques for measuring nitric oxide and nitrogen dioxide have drawbacks.

A new device for continuous measurement of gas exchange during artificial ventilation.

A new apparatus, which uses a fuel cell for measuring O2 concentration and calculates O2 consumption (Vo2), has been developed for use on the Servo Ventilator. Together with an IR CO2 Analyzer, this equipment also provides CO2 production, end-tidal CO2 concentration, and the respiratory quotient.The accuracy of this equipment was evaluated by comparison with results from two standard methods: the Scholander technique in combination with a dry gas meter, and mass spectrometry combined with a wet gas meter.The results show that the differences between the Vo2 calculated from this equipment and two other standard methods are less than 5%. Thus, the accuracy of the new equipment seems reliable enough to make it a valuable tool in clinical use.

Detection of mouth alcohol during breath alcohol analysis.

The presence of mouth alcohol (MA) during alcohol breath test for law enforcement is the most common cause of falsely high breath alcohol concentrations (BrAC). A fast and reliable test for detection of MA roadside at the scene of the act would facilitate the police efforts for proper prosecution. A tentative technique to use orally exhaled water vapour as a reference gas to position the origin of alcohol was validated. BrAC and water vapour concentration (WVC) were simultaneously measured as a known MA component was added to subjects with existing blood alcohol. In the absence of MA, water always precedes alcohol in a volumetric expirogram. In the presence of MA this relationship reversed. A scatterplot of WVC versus BrAC from similar fractional exhaled volumes illustrates how their relative positions change by MA. A deviation area (DA) between the scatterplot curve and a fictitious linear relationship was defined as a measurement of MA. The accuracy and cut-off level of the DA to detect MA were determined with receiver operating characteristic (ROC) curve analysis. The area under the ROC curve (AUC) was 0.95 (95% CI 0.90-1.0), indicating excellent discriminatory ability. The optimal cut-off for DA to discriminate between MA ≥0.010 mg/L (1 μg/100 ml, 0.002 g/210 L) or lack of MA was -0.35, with a sensitivity of 0.91 and specificity of 0.95. Analysis of BrAC in relation to WVC is a practical method to detect and confirm MA contamination with high reliability.