A non-invasive off-line method of measuring cardiac output

The measurement of cardiac output has many clinical applications and the development of a reliable, non-invasive measurement technique would be of considerable value to clinicians, cardio-respiratory physiologists and cardiovascular pharmacologists. Currently-used methods of measuring cardiac output are either invasive, and therefore potentially dangerous, or require the use of expensive, sophisticated, complex equipment which often has to be kept exclusively for the purpose of measuring cardiac output. We describe a method based on the recently modified and validated acetylene rebreathing technique which avoids the necessity for on-line computer acquisition of data by employing semi-manual digitization of hard copy recordings. The method is non-invasive, accurate, sensitive and relatively inexpensive. In addition, the whole technique can be rapidly performed by minimally trained personnel.