Pulmonary Circulation During Anesthesia
The anatomie arrangement and composition of the lung has evolved so as to allow gas exchange across a large and exquisitely thin membrane at the blood/gas interface (1). The entire cardiac output must be accommodated at low pulmonary vascular pressures and this imposes a design constraint that is common to all mammals. The low pressure is necessary to avoid the development of edema. The plasma oncotic pressure is normally about 35 cm H2O and, according to the relationships governing fluid flow enunciated by Starling a century ago, this is also the upper limit for the normal pulmonary artery pressure. Patients with pulmonary artery pressure consistently above 35 cm H2O are diagnosed as having pulmonary hypertension (2). Interestingly in all these species the vital capa city of the lung is achieved with transpulmonary pressures of 35 cm H2O, and barotrauma occurs in otherwise normal lungs ventilated with pressures in excess of this. The pulmonary circulation is therefore a system of elastic tubes in parallel the dimensions of which are governed passively by intravascular and extravascular fore es and by vasoactivity.
KeywordsPulmonary Artery Pressure Pulmonary Vascular Resistance Pulmonary Circulation Bronchial Artery Left Atrial Pressure
Unable to display preview. Download preview PDF.
- 1.Weibel E.R.: The Pathway for Oxygen. Cambridge, Harvard University Press, 1984Google Scholar
- 2.Marshall B.E., Marshall C.: Pulmonary hypertension. The Lung: Scientific Foundation. Crystal R.G., West J.B., Cherniak H., Weibel R. (eds.). New York, Raven Press, pp. 1177–89, 1991Google Scholar
- 3.Yen R.T., Foppiano L.: Elasticity of small pulmonary veins in the cat. J. Biomech Eng 103:38–42Google Scholar
- 6.Fung Y.C.: Biodynamics. New York, Springer Verlag, p. 290–369, 1984Google Scholar
- 8.Murray T.K., Chen L., Marshall B.E., et al: Hypoxic contraction of cultured pulmonary vascular smooth muscle cells. Am J Resp Cell & Mol. Biol 3:457–65, 1990Google Scholar
- 10.Marshall B.E., Marshall C., Magno M., et al: The influence of bronchial artery oxygen tension on pulmonary vascular resistance. J Appl Physiol 405–15,1991Google Scholar