Abstract: A method for the measurement of cardiac output in a patient in which the arterial blood pressure waveform of a patient from a blood pressure monitoring device over a period of time is subjected to various transformations and corrections, including a Fourier analysis in order to obtain the modulus of the first harmonic. The nominal stroke volume is then determined from the first harmonic and data relating to the arterial blood pressure and heart rate. The nominal cardiac output is then obtained from the nominal stroke volume.

Abstract: A method of analyzing a signal representing a physical parameter to obtain information from said signal and to extrapolate information contained in said signal and/or to ignore an interfering component in part of said signal, said signal representing either only a first portion of a skew distribution, or a first portion of a skew distribution and a second portion containing an interfering component, in which the area of a skew distribution, preferably a lognormal distribution is measured. The method is particularly applicable to the measurement of cardiac output. Apparatus for carrying out the method is also disclosed.

Abstract: A method for the measurement of cardiac output in a patient in which the arterial blood pressure waveform of a patient from a blood pressure monitoring device over a period of time is subjected to various transformations and corrections, including autocorrelation, whereby the pulsatility and heart rate of the patient are obtained. The nominal stroke volume is then calculated from the pulsatility and the nominal caridac output obtained by multiplying the stroke volume by the heart rate.

Abstract: A cation-sensitive electrode which comprises an internal reference electrode, an internal reference solution and a cation-responsive membrane, characterized in that the internal reference solution contains a saturated solution of a salt of a cation other than the cation for which the cation-responsive membrane is primarily selective, the internal reference solution being formed in situ by hydration of a combination of the salt of the cation with a hygroscopic material, bu absorption of water from the atmosphere and/or by hydration of the hygroscopic material when the electrode is put into use, thereby forming the internal reference solution.