Validation of the pulse decomposition analysis algorithm using central arterial blood pressure

Abstract

Background: There is a significant need for continuous noninvasive blood pressure (cNIBP) monitoring, especially for anesthetized surgery and ICU recovery. cNIBP systems could lower costs and expand the use of continuous blood pressure monitoring, lowering risk and improving outcomes.The test system examined here is the CareTaker® and a pulse contour analysis algorithm, Pulse Decomposition Analysis (PDA). PDA's premise is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses that are due to the left ventricular ejection and reflections and re-reflections from only two reflection sites within the central arteries.The hypothesis examined here is that the model's principal parameters P2P1 and T13 can be correlated with, respectively, systolic and pulse pressures.

Methods: Central arterial blood pressures of patients (38 m/25 f, mean age: 62.7 y, SD: 11.5 y, mean height: 172.3 cm, SD: 9.7 cm, mean weight: 86.8 kg, SD: 20.1 kg) undergoing cardiac catheterization were monitored using central line catheters while the PDA parameters were extracted from the arterial pulse signal obtained non-invasively using CareTaker system.

Results: Qualitative validation of the model was achieved with the direct observation of the five component pressure pulses in the central arteries using central line catheters. Statistically significant correlations between P2P1 and systole and T13 and pulse pressure were established (systole: R square: 0.92 (p < 0.0001), diastole: R square: 0.78 (p < 0.0001). Bland-Altman comparisons between blood pressures obtained through the conversion of PDA parameters to blood pressures of non-invasively obtained pulse signatures with catheter-obtained blood pressures fell within the trend guidelines of the Association for the Advancement of Medical Instrumentation SP-10 standard (standard deviation: 8 mmHg(systole: 5.87 mmHg, diastole: 5.69 mmHg)).

Conclusions: The results indicate that arterial blood pressure can be accurately measured and tracked noninvasively and continuously using the CareTaker system and the PDA algorithm. The results further support the physical model that all of the features of the pressure pulse envelope, whether in the central arteries or in the arterial periphery, can be explained by the interaction of the left ventricular ejection pressure pulse with two centrally located reflection sites.

Figure 1

Sketch of the aorta/arm complex arterial system and its effect on the arterial pressure pulse line shape that is observed at the radial/digital artery. Two reflection sites, one at the height of the renal arteries, the other one in the vicinity of the iliac bifurcation, give rise to the reflected pulse (gray) that trail the primary left ventricular ejection (black).

Figure 2

Different pressure pulse spectra of a 21-old male athlete. (A) Arterial pressure pulse obtained from digital integration of signal displayed in (B): derivative signal of arterial pressure pulse obtained with CareTaker physiological monitor (C); second derivative of arterial pressure pulse, obtained through differentiation of signal displayed in (B). Component pulses are identified with, respective, P1, P2, P3. Significance of arrows is explained in the text.

Figure 3

Different pressure pulse spectra of a 65-old male at two different blood pressures. (A) Arterial pressure pulses obtained from digital integration of signal displayed in (B): derivative signals of arterial pressure pulse obtained with CareTaker physiological monitor (C); second derivatives of arterial pressure pulse, obtained through differentiation of signal displayed in (B). Note the merging of P2 and P1 in the pulse envelopes (A) as well as the increase in the shoulder between data points 100 and 150 in the derivative signals (B). Significance of red arrow is explained in the text.

Figure 4

Overlap of raw and derived signals for patient 31. (A) Printout of the central line blood pressure data; (B) derivative signal of arterial pressure pulse obtained with CareTaker physiological monitor; (C) arterial pressure pulse obtained from digital integration of signal displayed in (B); (D) overlay of A-line systole, A-line pulse pressure, P2P1 ratio and T13 time interval.

Figure 5

Overlap of the inter-beat interval series obtained from central line catheter (red) and data obtained with the CareTaker physiological monitor (black) for patient 38.

Figure 6

Overlap of central systolic pressure (red) obtained from catheter signal and P2P1 ratio obtained from PDA analysis of non-invasively obtained arterial signal (black) for patient 38.

Figure 7

Overlap of central pulse pressure (red) obtained from catheter signal and T13 delay time obtained from PDA analysis of non-invasively obtained arterial signal (black) for patient 38.

Figure 8

Correlation of P2P1 parameter with central line systolic pressure, as shown in Figure 5, for patient 38.

Figure 9

Correlation of T13 parameter with central line pulse pressure, as shown if Figure 7, for patient 38.

Figure 10

Overall correlation of systolic blood pressures obtained through conversion of PDA parameters from non-invasively obtained arterial pulse signal, and central systole.

Figure 11

Overall correlation of diastolic blood pressures obtained through conversion of PDA parameters from non-invasively obtained arterial pulse signal, and central diastole.

Figure 12

Bland-Altman comparison of systolic pressure difference versus systolic pressure average. Standard deviation: 5.87 mmHg.

Figure 13

Bland-Altman comparison of diastolic pressure difference versus diastolic pressure average. Standard deviation: 5.69 mmHg.

Figure 14

Histogram distribution of the slope parameters of the linear conversions from P2P1 to systole. Blue marker is described in the text.

Figure 15

Histogram distribution of the slope parameters of the linear conversions from T13 to pulse pressure. Blue marker is described in the text.

Figure 16

Overlap of the central pressure pulse profiles collected with a catheter in a patient with left ventricular failure (#2) and normal heart function (#6). Due to the shortened LVET the individual component pulses are clearly resolved in the case of patient #2.

Figure 17

Central catheter pressure pulse profile for patient 38, where all of the component pulses (P1 through P5) are clearly resolved. Red vertical bars indicate positions of, respectively, P3, P4, P5.