Measurement of pulmonary capillary blood flow by a nitrous oxide rebreathing technique

Abstract

Measurements of pulmonary capillary blood flow by a nitrous oxide rebreathing technique (QN2O) were performed in 21 anesthetized and artificially ventilated minipigs with normal lungs and in nine minipigs with thrombin-induced (75-150 U kg-1 h-1) lung pathology. QN2O was calculated with the Hook-Meyer-formula and compared to cardiac output measurements (thermodilution, QT, or direct Fick's principle, QFick). The coefficient of variation in double QN2O measurements was 0.05. If the tidal volume to dead space ration (VD/VT) is normal, the nitrous oxide method works well, but when the efficacy of ventilation worsens, this gas uptake method fails to detect the circulation of the poorly ventilated parts of the lung. The mean ratio QN2O/QFick in pigs with normal lungs (58 measurements) was 1.00 +/- 0.10 (mean +/- s.d.). During thrombin infusion, the mean ratio QN2O/QT was 0.84 +/- 0.17 (n = 49). After corrections for shunt perfusion (Qs), the mean ration QN2O/(QT-Qs) was 0.89 +/- 0.17 (n = 49). QN2O/QT-Qs) decreased with increasing VD/VT. In measurements during thrombin infusion with VD/VT less than 0.33, the mean ratio QN2O/(QT-Qs) was 0.97 +/- 0.11 (n = 21), with a VD/VT between 0.33 and 0.44, the mean ratio QN2O (QT-QS) was 0.90 +/- 0.08 (n = 20), and with a VD/VT greater than or equal to 0.45, this ratio was 0.62 +/- 0.18 (n = 8). In the presence of only moderate functional inhomogeneities, this noninvasive rebreathing method will offer reliable data on pulmonary perfusion.

Nichtinvasive Bestimmung des Herzzeitvolumens bei beatmeten Patienten

“…Rückatmungsmethoden werden bereits seit langem zur nichtinvasiven Messung des Herzzeitvolumens sowohl bei spontan atmenden [26,29] als auch bei maschinell beatmeten Patienten benutzt [5,24].Ihre Verwendung in der klinischen Routine wurde jedoch bislang vor allem durch die Notwendigkeit einer akkuraten Gaskonzentrationsmessung erschwert.In der Vergangenheit wurde hierfür häufig die Massenspektrometrie herangezogen, die jedoch ein teures und zudem unhandliches Verfahren darstellt,das für den Routineeinsatz am Patientenbett wenig geeignet ist.…”

“…Es ergeben sich abfallende Gaskonzentrationskurven, deren Steigung proportional zu PBF ( [24].Das Messsystem konstruiert automatisch Regressionsgeraden durch die endexspiratorischen Kurvenanteile der Gaskonzentrationskurven innerhalb des Messintervalls. Um eine Beeinträchtigung der PBF-Bestimmung durch rezirkulierendes N 2 O zu vermeiden,wurde die Analyse der N 2 O-Kurve auf die ersten 25 s der Rückat-mung beschränkt [29].Da es während der Rückatmung aufgrund der Aufnahme von N 2 O und O 2 bzw.…”

Clinical developments for treating ARDS

“…In addition, ip. administration of ONO-5046 significantly inhibited endotoxininduced vascular injury in rats [60]. Phase I and II clinical trial data have been encouraging and large-scale clinical trials of ONO-5046 are underway in ALI/ARDS.…”

“…ONO-5046 (Sivelestat) has undergone extensive animal testing. In various models of lung injury, administration of ONO-5046 resulted in significant reduction in pulmonary vascular permeability, neutrophil accumulation and haemorrhage [60]. In addition, ip.…”

Development andin vitro validation of a device for measuring non-shunt cardiac output by nitrous oxide throughflow

“…cardiac output before the re-circulation time, but the technique was suitable only for single or occasional measurement of cardiac output (AYOTTE et al, 1970;CANDER and FORSTER, 1959;HENEGHAN and BRANTHWAITE, 1981;KROGH and LINDHARD, 1912;PETERSON etal., 1978;SACKNERetal., 1975;STOKKE et al, 1986;TEICHMANN et aL, 1974;TRIEBWASSER et al, 1977;ZEIDIFARD et al, 1976). Other methods to calculate the mixed venous partial pressure of nitrous oxide required special breathing techniques, such as breath-holding, singlebreath and rebreathing or partial rebreathing (CAPEK and RoY, 1988;GEDEON et al, 1980;BINDER and PA~KIN, 2001), which limit the frequency of measurement.…”