1) What is Pulse Contour Method (PCM)?
PCM is a theory postulated by O.Frank in 1899 ; O.Frank first found that pressure rise during systole was related to systolic filling of aorta and proximal large arteries; many authors later confirmed this relation.
O.Frank perceived that SV was the result of the pulsatory systolic component of arterial wave divided by the impedance Z(t). With those days science findings, it was not possible to measure the dynamic Z(t) value. He resigned himself to proceed with some simplifications: PCM could lead only to an approximated SV. PRAM finally concretizes O.Frank first purpose.
2) How can MostCare calculate Stroke Volume (SV) without the need of an external calibration or preestimated data?
As we already know, SV is calculated dividing an area under the systolic phase of the pressure waveform (A) by an impedance Z(t) changing over time. The way in which P.R.A.M. method calculates the parameters A and Z(t) allows to avoid the use of a system calibration. In fact, differing from other pulse contour methods:
a) the area under the curve A is calculated considering not only the pulsatile component of the systolic phase, but also the continuous one.
b) the impedance Z(t) takes into account both the systolic and the diastolic phase in their pulsatile and continuous components. Pressure waveform is analyzed in a "perturbative" manner, meaning that all the active and/or purely resistive components that contribute to the heartbeat are considered. In this way, we calculate the specific impedance of the subject under osservation, real time and beat-to-beat.
All these calculations would not be possible without a sampling rate of 1000 Hz.
3) What does Z(t) mean and why it is so difficult to calculate it?
Z(t) represents the cardiovascular impedance; it comprehends heart contractility, arterial compliance, arterial impedance and peripheral vessel resistance. Graphically, Z(t) is expressed by an arterial curve profile. As too many factors simultaneously and continuously concur in determining Z(t), for years nobody found how to measure it.
The attempts to quantify Z(t) led to a determination of a Zfix: the only way to give Z a quantification was to "freeze" it and to consider it stable during time. This was done by PCM based devices via an external calibration (thermo or indicator dilution) or by in vivo/in vitro measurement of impedance.
4) What does CCE is descriptive of and what does it mean?
CCE stays for Cardiac Cycle Efficiency; it is a "stress index", describing the cardiac haemodynamic performance in terms of hemodynamic work performed and energetic expenditure. CCE indicates the efforts committed by the heart to maintain homeostasis. Different energetic expenditures can be spent by the heart to keep the cardiovascular system in some kind of balance; CCE physically represents the ratio between the shape of the pressure wave that patients should ideally have and the actually detected one. Expressed as a pure number, it ranges between +1 and -1. The more positive is CCE, the more is the heart efficiency.
5) Does CCE have any clinical evidence?
Yes! CCE has been compared with LV ejection fraction (EF%) by echocardiography before and after cardiopulmonary bypass . Overall, the correlation coefficient between LVEF% and CCE values was 0.82 (r2 =0.91, p<0.001), and the correlation coefficients at each time of the study ranged from 0.80 to 0.84, p<0.0015. Thus, PRAM seemed a reliable tool for detecting changes in cardiac cycle performance and for monitoring myocardial function and recovery during cardiac surgery. An inverse correlation has also been found between CCE and pro-BNP values . Pro-BNP has been shown to correlate with myocardial hypertrophy (MH) and dysfunction .
Frank O. Die Grundform des arteriellen Pulses. Z Biol. 1899; 37:483-526
 Scolletta S, Romano SM, Maglioni E, et al. Left ventricular performance by PRAM during cardiac surgery. Intensive Care Med 2005; 31(Suppl 1):S157
 Sabino Scolletta, Federico Franchi, Pierpaolo Giomarelli, Bonizella Biagioli. Asswssment of cardiac surgery patients: the coupling between pro-B-Type natriuretic peptide and arterial wave form analysis“. Cardiomyopathies: Causes, Effects and Treatment, Editors: Peter H. Bruno and Matthew T. Giordano – Nova Publishers – IN PRESS
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