Annals of cardiac anaesthesia
-
Minimally invasive and non-invasive methods of estimation of cardiac output (CO) were developed to overcome the limitations of invasive nature of pulmonary artery catheterization (PAC) and direct Fick method used for the measurement of stroke volume (SV). The important minimally invasive techniques available are: oesophageal Doppler monitoring (ODM), the derivative Fick method (using partial carbon dioxide (CO2 ) breathing), transpulmonary thermodilution, lithium indicator dilution, pulse contour and pulse power analysis. Impedance cardiography is probably the only non-invasive technique in true sense. ⋯ The physical and the physiological aspects underlying the pulse contour and pulse power analyses, various pulse contour techniques, their development, advantages and limitations are also covered. The principle of thoracic bioimpedance along with computation of CO from changes in thoracic impedance is explained. The purpose of the review is to help us minimize the dogmatic nature of practice favouring one technique or the other.