Summary
A method for measuring pulmonary oedema (ETVl) is described using sodium ions as the intravascular indicator and heat as the extravascular indicator. The technique offers the advantage of virtually unlimited repeatability, relatively uncomplicated instrumentation and no blood loss. There is also the potential for differentiating between pulmonary oedema and pulmonary congestion and determining the efficacy of therapy.
A sensing catheter to detect blood conductivity and temperature changes is required. Ideally the sensing catheter should be situated at a point just distal to the aortic valve. However, a commercially manufactured detecting catheter we had built proved troublesome to insert because of its relatively large diameter. Therefore, an external sensing catheter has been constructed to measure ETVl and the values obtained have been compared with those from an internal catheter. There was no difference between the internal and external catheter Qt, but ETVL was consistently overestimated by 2.46 ± 0.26 ml/kg. However, this value can be related to the internal value and can be used for clinical studies.
Résumé
La mesure de ľeau pulmonaire extra-vasculaire (ETVL) s’est butée jusqu’ici à des difficultés techniques qui la rendaient à peu près impraticable. En cherchant des indicateurs plus maniables que les isotopes, Pearce et Beazell ont proposé ďutiliser la chaleur qui en ľoccurence se comporte comme un indicateur non moléculaire diffusible. Noble et Severinghaus utilisent une solution de NaCl à 3 pour cent à la température de la pièce: la diffusion thermique sert ďindicateur extra-vasculaire et les ions sodium ďindicateur intra-vasculaire. Ce travail décrit ľemploi de ces indicateurs pour mesurer ľETVL. La technique nécessite des instruments relativement simples, n’entraîne pas de perte de sang et est virtuellement répétable à satiété.
II faut disposer ďun cathéter capteur capable de percevoir des changements de la conductivité du sang et de sa température. De façon idéale, ce capteur se place dans ľaorte, tout près de la valve aortique. Cependant, celui qu’on nous avait fabriqué, s’est avéré impraticable à cause de sa taille et aussi nous en avons conçu un autre pour usage externe. Les mesures de ETVL et de débit cardiaque par diffusion thermique ( Qt ), obtenues par ľun et ľautre cathéter ont été comparées: les QT étaient tout à fait comparables ďun cathéter à ľautre mais ľETVL était constamment surestimé par le capteur externe. Cependant, ľinformation recueillie par ce capteur extrene peut être redressée et utilisée cliniquement.
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Kay, J.C., Noble, W.H. Lung water estimation using an external sensing catheter. Canad. Anaesth. Soc. J. 24, 322–331 (1977). https://doi.org/10.1007/BF03005105
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DOI: https://doi.org/10.1007/BF03005105