A novel photoplethysmography technique to derive normalized arterial stiffness as a blood pressure independent measure in the finger vascular bed.

Stiffening of the small artery may be the earliest sign of arteriosclerosis. However, there is no adequate method for directly assessing small arterial stiffness. In this study, the finger arterial elasticity index (FEI) was defined as the parameter n which denotes the curvilinearity of an exponential model of pressure (P)-volume (V(a)) relationship (V(a) = a - b exp (-nP)). For the original estimation, the FEI was calculated from a compliance index from the finger photoplethysmogram whilst occluding the finger. A simple estimation of the FEI was devised by utilizing normalized pulse volume instead of the compliance index. Both estimations yielded close agreement with the exponential model in healthy young participants (study 1: n = 19). Since the FEI was dependent on finger mean blood pressure, normalized finger arterial stiffness index (FSI) was defined as standardized residual from their relationship: mean and standard deviation (SD) of the FSI were 50 ± 10 (study 2: n = 174). The mean coefficient of variation of the FSI for four measurements was 5.72% (study 3: n = 6). The mean and SD of the FSI in seven arteriosclerotic patients were 100.0 ± 13.5. In conclusion, the FEI and FSI by simple estimation are valid and useful for arteriosclerosis research.

How carryover has an effect on recovery measures related to the area under the curve: theoretical and experimental investigations using cardiovascular parameters.

This study examines cardiovascular recovery from mental stress. Investigating the absence or presence of carryover effect, the effect of the final reactivity observed at the end of stressful task on the successive recovery, was the major objective. A recently advocated recovery measure related to the area under the curve, mean recovery rate (MRR), was investigated, comparing with the two relatives of this type, total carryover (TCO) and literally area under the curve (AUC). At the onset, a detailed theoretical formulation of each measure was carried out, starting from its original definition. It was predicted that MRR, but not TCO or AUC, could be free from the carryover effect. Next, 88 male students underwent a 5-min mental arithmetic during which blood pressure and heart rate were measured. Nearly all the theoretical predictions (i.e., 5/6 for the three recovery measures by two cardiovascular parameters) were supported by experimental data. There was only one exception: for heart rate, there was a proportional relationship even for MRR versus the final reactivity. Vagal rebound in the recovery period was conceived as the main contributor of this contradiction. The implications of these results for the understanding of future directions in recovery studies are discussed.

[Cardiovascular responses during two kinds of mental arithmetic tasks].

Eighteen young females performed two kinds of mental tasks, an Internally-Generated Mental Arithmetic task (IGMA: serial subtraction) and an Externally-Presented Mental Arithmetic task (EPMA: continual subtraction). Both tasks were equal in establishing active coping, but EPMA made participants attend more to an external stimulus. The expected reaction patterns were vascular-dominant (blood pressure elevation mainly due to an increase in total peripheral resistance) for only EPMA, or cardiac-dominant (mainly due to an increase in cardiac output) for both IGMA and EPMA. The results showed that vascular-dominant patterns were evoked during EPMA, while mixed (moderate increases in both cardiac output and total peripheral resistance) reaction patterns were evoked during IGMA. Post-task questionnaires confirmed that attention to an external stimulus was required much more in EPMA than in IGMA. These results indicate that the vascular-dominant reaction pattern was evoked in the state where attention to an external stimulus was heightened. The implications of the present findings are discussed in term of how to interpret the hemodynamic reaction patterns during mental stress.

Attention-Affect Check List: A self-report measure of acute mental stress.

Given a hint from Lang, Bradley, and Cutbert's (1997) defense cascade, two cognitive processes, instead of passive versus active behavioral coping, which seem to have differential effects on the provocation of vascular- versus cardiac-dominant reaction pattern during mental stress were advocated: attention (Attent) versus unpleasant affect (UnplAff). Based on this notion the Attention-Affect Check List (AACL) was developed as a self-report measure. In addition, items on uncontrollability (Uncontr) were prepared for the purpose of checking whether heightened Attent and UnplAff are accompanied by alterations in Uncontr. Two hundred and eighty-four students underwent two kinds of mental stress, which seemed to specifically heighten Attent and UnplAff. Four factors with four items each were extracted from the AACL item pool: concentrated and allocated Attent, UnplAff, and pleasant affect. Also, one factor with four items was extracted from the Uncontr item pool. For both the mental stresses, each scale, although very brief, had quite reasonable alpha reliability. Accountability of each scale for the total variance was reasonably high. Some problems are discussed in relation to the validity of AACL.

[Application of finger arterial compliance-blood pressure function for an evaluation of the sympathetically mediated vascular tone].

Normalized pulse volume (NPV, Sawada, Tanaka, & Yamakoshi, 2001) was calculated on a beat-to-beat basis by dividing the ac component by the dc component in near-infrared finger photoplethysmogram. Finger arterial compliance index (CI) was obtained by dividing NPV by the respective pulse pressure. Twelve female subjects underwent immersions of the contralateral hand in water at two different temperatures (44 degrees C, 22 degrees C). During the last 3 min of each of the 8-min resting and immersion conditions, CI was measured for the finger position at heart level, 15 cm, and 30 cm below the heart for 1 min each. Results indicated that a negatively linear regression could be applied to the beat-to-beat data on log CI and mean blood pressure (MBP) over the three finger position (whole regression). CI calculated at 90 mmHg (CI 90) was arbitraily chosen as a reference point for comparing compliance among conditions. CI 90 decreased significantly during the 22 degrees C condition. In conclusion, CI seemed more valid as an index of the finger arterial vascular tone through the removal of MBP influence.

Examination of normalized pulse volume-blood volume relationship: toward a more valid estimation of the finger sympathetic tone.

The pulsatile ac component (DeltaI) superimposed on the transmitted dc components (I: tissue plus blood) are obtained from a near-infrared finger photoplethysmogram using a wavelength of 810 nm. Only the dc component is given in an ischaemic circulatory state (I(t): tissue only). Based on Lambert-Beer's law, normalized pulse volume (NPV; =DeltaI/I) and blood volume [BV; =ln(I(t)/I)] have recently been advocated as quantitative measures. In this study, the NPV-BV relationship was examined using the finger occlusion method during rest and mental arithmetic in 16 female undergraduates. Finger vascular tone during stress was evaluated by the distance of the linear and parallel NPV-BV regression lines (D(NB)) between rest and stress conditions. A reference standard was provided by the linear regression lines of compliance index (CI=NPV/pulse pressure) and BV to the transmural pressure. The estimates at 40 mmHg of transmural pressure, as an arbitrarily chosen reference point, were calculated (CI40 and BV40). D(NB) correlated well with them (r=0.81 and 0.94, respectively). The multiple regression with mean blood pressure indicated that the combination of D(NB) and the reactivities in heart period could explain approximately 50% of valiance in pressor response. In conclusion, D(NB) is easily obtainable from the NPV-BV function and seems to be more specific and valid than NPV as an index of finger sympathetic tone, since it adjusts the mechanical effect of arterial distending pressure.

Finger arterial compliance as determined by transmission of light during mental stress and reactive hyperaemia.

A near-infrared finger photoplethysmogram adopting a wavelength of 810 nm provides data pertaining to the pulsatile a.c. component of finger blood flow (delta I) superimposed on the transmitted d.c. components in a normal ( I: tissue plus blood) and an ischaemic circulatory state ( I(t): tissue only). Simultaneous recording of finger blood pressure provides data pertaining to the distending pulse (PP) and mean blood pressure. Based on the Lambert-Beer law, indices of the arterial compliance (CI=delta I/ I/PP) and distensibility [DI=delta I/ I/ln( I(t)/ I)/PP] are advocated for assessing finger vasculature. The functional relationships between transmural pressure and CI and DI were examined using finger occlusion while performing an arithmetic test (i.e. a mental stress) in 16 females, and during reactive hyperaemia in 5. Gradual occlusion of the finger was conducted at 20-s intervals and the beat-by-beat transmural pressure was determined by calculating mean blood pressure minus the occluding cuff pressure. Logarithmically transformed CI and DI data were linearly associated with the transmural pressure; thus, the estimates obtained at a transmural pressure of 40 mmHg were chosen as an arbitrary reference point (CI40 and DI40). The results indicated that CI40 and DI40 were reduced while performing an arithmetic test, and increased during reactive hyperaemia. Responses were larger for CI40 than for DI40. In conclusion, noninvasive finger occlusion allowed the measurement of the compliance/distending pressure relationship, and CI40 could be utilised to evaluate changes in finger vascular tone.