Photoelectric Plethysmography Research Articles

Wearable Photoelectric Fingertip Force Sensing System Based on Blood Volume Changes without Sensory Interference.

Monitoring the force of fingertip manipulation without disturbing the natural sense of touch is crucial for digitizing the skills of experienced craftsmen. However, conventional force sensors need to be put between the skin and the objects, which affects the natural sense of the skin. Here, we proposed a fingertip force sensing method based on changes of blood volume and designed a wearable photoelectric fingertip force sensing system (PFFS) for digitalization of traditional Chinese medicine (TCM) pulse diagnosis. The PFFS does not interfere with the fingertips' tactile sense while detecting fingertip force. This PFFS detects the change of blood volume in fingertip by photoelectric plethysmography and can obtain the change of output current under different fingertip forces. We also studied the effect of various factors on PFFS output signals, including emission lights of different wavelengths, ambient temperature, and the user's heartbeat artifact. We further established the relationship between the change of blood volume and fingertip force by combining experimental and theoretical methods. Moreover, we demonstrated the feasibility of the PFFS to detect fingertip forces under commonly used conditions in TCM pulse diagnosis without sensory interference. This PFFS also shows promise for perceiving the viscosity of objects and recognizing gestures in human-computer interaction. This work paves the way for the digitalization of fingertip forces during TCM pulse diagnosis and other fingertip forces under natural conditions.

Non-Contact Blood Pressure Measurement Based on IPPG

Blood pressure is an important physiological parameter to reflect human vital signs. In order to achieve the non-contact dynamic blood pressure acquisition based on ordinary optical camera, a theoretical understanding of the functional relationship between blood pressure and pulse wave signal conduction time. And through imaging photoelectric plethysmography (IPPG), pulse wave signal conduction time of forehead and hand was obtained with ordinary optical camera. First, the pulse wave conduction time was obtained by recording the video with an ordinary optical camera. Second, real-time blood pressure values were collected. Finally, based on the relationship between blood pressure and pulse wave conduction time, a non-contact blood pressure measurement prediction model was obtained through neural network fitting. So that noncontact blood pressure measurement with optical camera could be completed. The method in this paper has several advantages, such as low requirements on measuring equipment, low cost, and simple operation. It can let people get rid of the discomfort caused by measuring equipment such as cuff and can measure blood pressure at any time. The predicted blood pressure results were compared with an Omron wrist electronic sphygmomanometer. The calculated error of systolic blood pressure is –9.28%~3.16%, and the error of diastolic blood pressure is –9.84~4.35%.

Machine Learning Method for Continuous Noninvasive Blood Pressure Detection Based on Random Forest

In order to reduce the influence of differences in human characteristics on the blood pressure prediction model and further improve the accuracy of blood pressure prediction, this paper establishes support vector machine regression model and random forest regression model for accurate blood pressure measurement. First, the photoelectric method is used to obtain the photoelectric plethysmography signal (PPG) and ECG signals from people of different ages, and the blood pressure value is roughly estimated based on the high-quality physiological signals and the vascular elastic cavity model; then the human body characteristics are used as the input parameters of the blood pressure prediction model, and the model parameters are used to find the best parameter combination to improve the prediction performance of the model; finally, through a lot of training and learning, the best blood pressure prediction model is selected to achieve accurate measurement of blood pressure values. It has been verified by experiments that the average absolute error of diastolic and systolic blood pressure based on the random forest optimization model meets the standard of less than 5mmHg formulated by AAMI (American Medical Instrument Promotion Association), which is better consistent with the method of mercury sphygmomanometer, and has more excellent performance than support vector machine regression model under the same conditions.

Pharmacokinetics and pharmacodynamics of dexmedetomidine-induced vasoconstriction in healthy volunteers.

Alpha-2 agonists are direct peripheral vasoconstrictors, which achieve these effects by activating vascular smooth muscle alpha-2 adrenoceptors. The impact of this response during dexmedetomidine infusion remains poorly quantified. Our goal was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD, vasoconstriction) effects of a computer-controlled dexmedetomidine infusion in healthy volunteers. After local ethics committee approval, we studied 10 healthy volunteers. To study the peripheral vasoconstrictive effect of dexmedetomidine without concurrent sympatholytic effects, sympathetic fibres were blocked with a brachial plexus block. Volunteers received a dexmedetomidine target-controlled infusion for 15min, to a target concentration of 0.3ng ml-1 . Arterial blood samples were collected during and for 60min after dexmedetomidine infusion for PK analysis. Peripheral vasoconstriction (PD) was assessed using finger photoelectric plethysmography. PK/PD analysis was carried out using nonlinear mixed-effect models. We found that the computer-controlled infusion pump delivered mean concentrations greater than 0.3ng ml-1 over the 15-min infusion duration. The peripheral vasoconstrictive effect correlated with dexmedetomidine plasma concentrations during and after the infusion. A three-compartment model provided a better fit to the data than a two-compartment model. We found that dexmedetomidine-induced vasoconstriction is concentration dependent over time. Dexmedetomidine PK were best estimated by a three-compartment model with allometric scaling. Our results may contribute to future modelling of dexmedetomidine-induced haemodynamic effects.

Association between diabetic peripheral neuropathy and heart rate variability in subjects with type 2 diabetes

AimThis study evaluated the association of Heart rate variability (HRV) measurements with diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes. MethodsThis study included 102 Korean subjects with type 2 diabetes. The Michigan neuropathy screening instrument (MNSI) questionnaire score, the MNSI examination score (MNSIES) and the total symptom score were examined for DPN evaluation. Noninvasive HRV measurements were performed using photoelectric plethysmography. Patients with a MNSIES > 2 were considered to have DPN. ResultsThe MNSIES showed significant negative associations with the high frequency (HF) (r = −0.212, p = 0.033) and low frequency (LF) (r = −0.286, p = 0.004) powers. Multiple linear regression analysis revealed that only HF power maintained a significant negative association with the MNSIES (β = −0.184; 95% CI −0.365 to −0.003; p = 0.047), after controlling for significant related confounders, with HRV parameters in male patients with type 2 diabetes. The HF (p = 0.010) and LF (p = 0.025) powers differed significantly between male patients without and those with DPN according to the MNSIES. ConclusionsThis study revealed a negative association of DPN, as assessed by the MNSIES, with HF power in male patients with type 2 diabetes. DPN defined by foot examination was predictive of cardiac autonomic neuropathy.

Digital ischaemia during cooling is independently related to nailfold capillaroscopic pattern in patients with Raynaud's phenomenon.

The aim of the study was to assess the association between plethysmographically measured vasospasms during stepwise cooling and recovery, as an index for digital ischaemia, and nailfold capillaroscopic pattern (NCP) severity in patients with primary or secondary RP, including SSc. In 381 consecutive patients with suspected RP without a history of digital ulcers, NCP (assessed by widefield videocapillaroscopy), fingertip photoelectric plethysmography during cooling and recovery and clinical characteristics were analysed. NCPs were graded as follows: normal, non-specific, early and active. The mean ischaemic time was defined as the mean time of perfusion loss during cooling and recovery of five fingers. In the patients with loss of perfusion during cooling and recovery, the NCP was normal in 152, non-specific in 96, early in 61 and active in 39 patients. The mean ischaemic time was positively associated with the severity of NCP, with P < 0.05 for each two- or three-grade increase and independent of underlying SSc. The difference was most pronounced during recovery. We demonstrate that the degree of vasospasm and ischaemia provoked by stepwise cooling and recovery are positively associated with NCP in patients with RP of different aetiologies and without a history of digital ulcers.

Digital Photoplethysmography for Assessment of Arterial Stiffness: Repeatability and Comparison with Applanation Tonometry.

IntroductionArterial stiffness is an independent risk factor for cardiovascular morbidity and can be assessed by applanation tonometry by measuring pulse wave velocity (PWV) and augmentation index (AIX) by pressure pulse wave analysis (PWA). As an inexpensive and operator independent alternative, photoelectric plethysmography (PPG) has been introduced with analysis of the digital volume pulse wave (DPA) and its second derivatives of wave reflections.ObjectiveThe objective was to investigate the repeatability of arterial stiffness parameters measured by digital pulse wave analysis (DPA) and the associations to applanation tonometry parameters.Methods and Results112 pregnant and non-pregnant individuals of different ages and genders were examined with SphygmoCor arterial wall tonometry and Meridian DPA finger photoplethysmography. Coefficients of repeatability, Bland-Altman plots, intraclass correlation coefficients and correlations to heart rate (HR) and body height were calculated for DPA variables, and the DPA variables were compared to tonometry variables left ventricular ejection time (LVET), PWV and AIX. No DPA variable showed any systematic measurement error or excellent repeatability, but dicrotic index (DI), dicrotic dilatation index (DDI), cardiac ejection elasticity index (EEI), aging index (AI) and second derivatives of the crude pulse wave curve, b/a and e/a, showed good repeatability. Overall, the correlations to AIX were better than to PWV, with correlations coefficients >0.70 for EEI, AI and b/a. Considering the level of repeatability and the correlations to tonometry, the overall best DPA parameters were EEI, AI and b/a. The two pansystolic time parameters, ejection time compensated (ETc) by DPA and LVET by tonometry, showed a significant but weak correlation.ConclusionFor estimation of the LV function, ETc, EEI and b/a are suitable, for large artery stiffness EEI, and for small arteries DI and DDI. The only global parameter, AI, showed a high repeatability and the overall best correlations with AIX and PWV.

A Controlled Study of Alprostadil Liposomal Preparation in the Treatment of Blue Toe Syndrome.

The aim of this study is to examine the efficacy of alprostadil liposomal preparation in the treatment of blue toe syndrome. As many as 32 patients with blue toe syndrome were randomized into the test group and a control group. Patients out of the test group were treated with alprostadil liposomal preparation, while those out of the control group received placebo administration. Inter-group comparisons were conducted for the post-therapeutic changes of microcirculation and improvements of clinical symptoms. In the test group, there were eight subjects with marked response (50.0 %), six subjects with partial response (37.5 %), and two subjects with no response (12.5 %), with the overall response rate of 87.5 %. In the control group, there were three cases (18.8 %), one case (6.4 %), and 12 cases (75 %), respectively, with the overall response rate of 25.0 %. The inter-group difference of response was statistically significant (Χ (2) = 12.987, P = 0.002 < 0.05). In the test group, there was one case of administration site redness which could be resolved spontaneously. No other adverse drug reactions were reported. No any complaints were reported for the control group. The inter-group difference of nail-fold microcirculation was not statistically significant (P > 0.05). The post-therapeutic points of nail-fold microcirculation in the test group decreased significantly (P < 0.05), but no significant changes were observed for the control group (P > 0.05). The post-therapeutic waveform changes of photoelectric plethysmography were significant for the test group in comparison to the control. The safety and efficacy of alprostadil liposomal preparation have been demonstrated in the treatment of blue toe syndrome.

Transradial approach for challenging vascular access interventions.

Percutaneous interventional procedures for vascular access are usually performed using the draining cephalic or basilic vein. The transradial approach, which has been extensively investigated for coronary angiography and intervention, could be an attractive new technique for peri-anastomotic arteriovenous fistula stenosis. From June 2012 to February 2013, 30 patients with end-stage renal failure were evaluated for transradial vascular access intervention. A 4-French (Fr) micropuncture kit was used to access the radial artery and then subsequently upgraded to a 5-Fr sheath. Fourteen patients required an upgrade to a 6-Fr sheath for the final intervention. Primary technical success (residual stenosis <30%) was achieved in all cases where angioplasty was performed. Technical success regarding access was achieved in all patients. There were no peri-procedural complications. The post-interventional primary patency was calculated as 100%, 100%, 88.4% and 32.8% at 1, 6, 9 and 12 months, respectively. The post-interventional primary assisted patency was calculated as 100%, 100%, 100% and 63.3% at 1, 6, 9 and 12 months, respectively. Based on colour-coded Duplex scan and/or photoelectric plethysmography, all access-site arteries showed normal perfusion; however, the freedom from significant radial artery restenosis was 92.4% at 12-month follow-up. The transradial approach for vascular access endovascular interventions is technically feasible and safe. It allows simultaneous treatment of peri-anastomotic lesions in fistulas with complex venous anatomy as well as lesions in the arterial inflow and central outflow.

SAT0301 Vasospastic Severity and Digital Ischemia during Cooling is Related to Nail-Fold Capillaroscopic Pattern in Patients with Secondary Raynaud Phenomenon and Systemic Sclerosis

BackgroundMicroangiopathy, assessed as specific nail-fold capillaroscopic patterns (NCP), is a key feature and currently diagnostic criterion in the development of systemic sclerosis (SSc). In advanced SSc, NCP severity correlates clearly...

Real-Time Heart Rate Monitoring System based on Ring-Type Pulse Oximeter Sensor

With the continuous aging of the populations in developed countries, the medical requirements of the aged are expected to increase. In this paper, a ring-type pulse oximeter finger sensor and a 24-hour ambulatory heart rate monitoring system for the aged are presented. We also demonstrate the feasibility of extracting accurate heart rate variability measurements from photoelectric plethysmography signals gathered using a ring-type pulse oximeter sensor attached to the finger. We designed the heart rate sensor using a CPU with built-in ZigBee stack for simplicity and low power consumption. We also analyzed the various distorted signals caused by motion artifacts using a FFT, and designed an algorithm using a least squares estimator to calibrate the signals for better accuracy.

광전용적맥파를 이용한 요골동맥 산소포화도 측정 시스템의 연구

본 연구에서는 광전용적맥파를 이용하여 요골동맥에서 맥박 및 산소포화도를 검출하였다. 반사형으로 고안된 디바이스를 이용하여 요골동맥에서의 반사광은 수신부를 통해 측정되고, 이 측정된 신호는 스위칭을 통해 각각 625nm, 940nm의 파장대역의 신호로 분리된다. 분리된 신호는 각각의 맥박신호처리회로를 통해 맥박데이터로 구현된다. 본 연구에서는 반사 방식으로 손목부근의 요골동맥을 측정하였기에 투과방식이 아닌 반사방식의 산소포화도 측정에 적합한 방법을 적용하여 결과를 얻었다. 얻어진 결과는 약 97%정도의 정확도로 산소포화도를 검출할 수 있었다. 또한, 정확한 신호를 얻기 위해서 요골동맥에 센서가 장착된 밴드를 이용하여 측정 하였으며, 고정이 되도록 압박을 하였다. 결과로서 손목밴드의 장착을 통해 움직임에 의한 측정위치에러를 방지할 수 있었으며, 이에 따른 정확도를 높일 수 있었다. In this study, the pulse of radial artery and oxygen saturation are detected using photoelectric plethysmograph method. Using our device designed reflection type, we can detect the reflected light by radial artery and by switching circuit, we can also separate to 625nm band signal and 940nm band signals. The separated signals are converted as a pulse data by the pulse signal processing circuit. In this study, the reflection type of oxygen saturation calculation method is applied instead of the transmission type because of the reflection type sensor is used to measure the radial artery. As a result, we can detect about 97% accuracy of the oxygen saturation compare with the conventional method. For the accurate signals, the wrist band with sensor was designed and fixed on the radial artery. As a result, this wrist band type sensor was applicable to prevent position errors from motion artifact and could increase the accuracy during the measuring.

Input–output relationships of a somatosympathetic reflex in human spinal injury

Spinal cord injury results in loss of supraspinal control of sympathetic outflow, yet preservation of spinal reflexes. Given the importance of reflex activation of sympathetic vasoconstrictor neurones to the generation of autonomic dysreflexia, we assessed the input-output relationship of the spinal somatosympathetic reflex induced by electrical activation of cutaneous afferents over the lower abdominal wall. In 13 spinal cord-injured subjects (C4-T10) we tested the hypothesis that the magnitude and duration of the vasoconstriction is directly related to the magnitude and duration of the stimulus train. Cutaneous vasoconstriction was measured with photoelectric plethysmography over a finger and toe; continuous blood pressure was recorded by radial artery tonometry, heart rate by ECG chest electrodes and sweat release by skin conductance. Four sets of trains of cutaneous electrical stimuli (20 Hz 1 s, 20 Hz 20 s, 20 Hz 1 s alternating on-and-off for 20 s and 1 Hz 20 s) were applied to the abdominal wall (10 mA) at 2-min intervals. Nine subjects showed vasoconstrictor responses to the stimulus trains. On average, both the magnitude and duration of the responses were similar irrespective of the type of stimulus train. We conclude that there is a non-linear relationship between somatic inputs and sympathetic vasoconstrictor outputs, and argue that a sustained vasoconstriction need not imply continuous sensory input to the spinal cord.

Selective activation of muscle and skin nociceptors does not trigger exaggerated sympathetic responses in spinal-injured subjects

Measurement of sympathetic effector organ responses to selective activation of muscle and skin nociceptors below lesion in spinal cord-injured (SCI) subjects. To test whether selective noxious stimulation below lesion causes exaggerated sympathetic responses in human SCI. Prince of Wales Medical Research Institute, Australia. Twelve subjects (C5-T10, ASIA A-C), none of whom had sensation below the lesion, were included in the study. Selective stimulation of muscle or cutaneous nociceptors was produced by bolus injection of hypertonic (5%) saline into the tibialis anterior muscle or overlying skin and compared with non-noxious electrical stimulation of the abdominal wall. Cutaneous vasoconstrictor (photoelectric plethysmography) and sudomotor (skin conductance) responses, in addition to respiration, heart rate and continuous arterial pressure were monitored. Electrical stimulation of the abdominal wall caused a significant increase in arterial pressure (31.8+/-6.1%). Conversely, intramuscular or subcutaneous injection of hypertonic saline caused no significant changes in blood pressure (-3.0+/-2.4%; -1.4+/-3.4%) heart rate, skin blood flow or sweat release. While hypertonic saline injected into muscle or skin induces strong pain, cutaneous vasoconstriction and sweat release in able-bodied subjects, we saw no evidence of exaggerated sympathoexcitation when these same noxious stimuli were delivered below lesion in subjects with SCI. This suggests that certain types of somatic noxious input may not trigger autonomic dysreflexia, and questions the concept that any painful stimuli originating below lesion can reliably trigger dysreflexia.

Clinical effects of endovenous laser therapy plus transilluminated powered phlebectomy in treatment of primary varicose veins

To evaluate the clinical and cosmetic effects of endovenous laser therapy (EVLT) plus transilluminated powered phlebectomy (TIPP) in the treatment of primary varicose veins. The clinical effects of EVLT plus TIPP in treatment of 82 patients of primary varicose vein with 105 extremities were evaluated. The procedure-related parameters, clinical outcomes, and complications were recorded. The venous function was assessed by venous photoelectric plethysmography (VPPG). Aberdeen Varicose Veins Questionnaire (AVVQ) and Venous Clinical Severity Score (VCSS) surveys were used to appraise the quality of life and symptomatic alleviation. The successful rates of EVLT and TIPP was 98.1% (103/105) and 100% (105/105) respectively. The average operating time was 53.8 min (35 approximately 108 min). The average number of wounds was 4.4 (3 approximately 7). The postoperative hospitalization time was 4.8 d (2 approximately 6 d). The follow-up rates 3, 6, and 12 months after operation were 100%, 93.9%, and 35.4% respectively. Obvious symptom alleviation or entire disappearance was noticed in all the limbs 3 months after operation. The hemodynamic parameters, such as venous filling index (VFI), ejection fraction (EF), and residual volume fraction (RVF) were significantly ameliorated 1 month after the operation compared with those measured preoperatively (all P<0.01). No further improvements were noticed from then on (P>0.05). Disease specific quality of life was greatly improved after operation (P=0.000). 91.5% of the patients were satisfied with the postoperative appearance of the involved limbs. EVLT plus TIPP is an efficacious minimally invasive strategy for the treatment of primary varicose veins, resulting in approving cosmetic effect as well.

센서 네트워크 응용을 위한 반지형 맥박센서와 모니터링 시스템

블루투스, 지그비, RFID와 같은 저가의 저 전력 무선통신 기술의 실용화는 웰빙 바람과 함께 유비쿼터스 헬스케어에 대한 관심이 급격하게 증가하고 있으며 u-Health는 센서네트워크분야에서 가장 중요한 응용분야중 하나가 되고 있다. 특히 독거노인이나 실버타운의 노인을 위해 응급상황에 대한 대처가 가능한 의료서비스를 개발하는 것은 그 자체로 의미가 있으며 그 수요는 노령인구의 급속한 증가와 함께 지속적으로 늘어날 것으로 기대된다. 이에 본 논문은 일상생활에서 손가락에 착용한 반지모양의 pulse oximeter 센서에 의해 수집된 PPG 신호로부터 정확한 맥박 변화율을 이끌어내는 것에 대한 타당성을 보이고자 한다. 이를 위해 반사형과 투과형 2가지 종류의 반지센서를 제작하였으며 반지센서로부터 맥박데이터를 수집, 분석하고 응급상황에 대처할 수 있는 원격의 모니터링 시스템을 개발하였다. As low power, low cost wireless communication technology like Bluetooth, Zigbee, RFID has been put to practical use together with the wellbeing trend, the concern about ubiquitous health care has been greatly increased and u-Health is becoming one of the most important application in the sensor network field. Especially, development of the medical services to be able to cope with a state of emergency for solitary senior citizens and the aged in silver town is very meaningful itself and their needs are also expected to continuously increase with a rapid increase in an aging population. In this paper we demonstrate the feasibility of extracting accurate heart rate variability (HRV) measurements from photoelectric plethysmography(PPG) signals gathered by a ring type pulse oximeter sensor attached to the finger. For this, we made 2 types of ring sensor, that is reflective and pervious type, and developed the remote monitoring system which is able to collect HR data from ring sensor, analyze and cope with a state of emergency.

The Use of Joint Time Frequency Analysis to Quantify the Effect of Ventilation on the Pulse Oximeter Waveform

In the process of determining oxygen saturation, the pulse oximeter functions as a photoelectric plethysmograph. By analyzing how the frequency spectrum of the pulse oximeter waveform changes over time, new clinically relevant features can be extracted. Thirty patients undergoing general anesthesia for abdominal surgery had their pulse oximeter, airway pressure and CO(2) waveforms collected (50 Hz). The pulse oximeter waveform was analyzed with a short-time Fourier transform using a moving 4096 point Hann window of 82 seconds duration. The frequency signal created by positive pressure ventilation was extracted using a peak detection algorithm in the frequency range of ventilation (0.08-0.4 Hz = 5-24 breaths/minute). The respiratory rate derived in this manner was compared to the respiratory rate as determined by CO(2) detection. In total, 52 hours of telemetry data were analyzed. The respiratory rate measured from the pulse oximeter waveform was found to have a 0.89 linear correlation when compared to CO(2) detection and airway pressure change. the bias was 0.03 breath/min, SD was 0.557 breath/min and the upper and lower limits of agreement were 1.145 and -1.083 breath/min respectively. The presence of motion artifact proved to be the primary cause of failure of this technique. Joint time frequency analysis of the pulse oximeter waveform can be used to determine the respiratory rate of ventilated patients and to quantify the impact of ventilation on the waveform. In addition, when applied to the pulse oximeter waveform new clinically relevant features were observed.

Mechanisms of the cerebrovascular response to apnoea in humans

We measured ventilation, arterial O2 saturation, end‐tidal CO2 (PET,CO2), blood pressure (intra‐arterial catheter or photoelectric plethysmograph), and flow velocity in the middle cerebral artery (CFV) (pulsed Doppler ultrasound) in 17 healthy awake subjects while they performed 20 s breath holds under control conditions and during ganglionic blockade (intravenous trimethaphan, 4.4 ± 1.1 mg min−1 (mean ±s.d.)). Under control conditions, breath holding caused increases in PET,CO2 (7 ± 1 mmHg) and in mean arterial pressure (MAP) (15 ± 2 mmHg). A transient hyperventilation (PET,CO2−7 ± 1 mmHg vs. baseline) occurred post‐apnoea. CFV increased during apnoeas (by 42 ± 3 %) and decreased below baseline (by 20 ± 2 %) during post‐apnoea hyperventilation. In the post‐apnoea recovery period, CFV returned to baseline in 45 ± 4 s. The post‐apnoea decrease in CFV did not occur when hyperventilation was prevented. During ganglionic blockade, which abolished the increase in MAP, apnoea‐induced increases in CFV were partially attenuated (by 26 ± 2 %). Increases in PET,CO2 and decreases in oxyhaemoglobin saturation (Sa,O2) (by 2 ± 1 %) during breath holds were identical in the intact and blocked conditions. Ganglionic blockade had no effect on the slope of the CFV response to hypocapnia but it reduced the CFV response to hypercapnia (by 17 ± 5 %). We attribute this effect to abolition of the hypercapnia‐induced increase in MAP. Peak increases in CFV during 20 s Mueller manoeuvres (40 ± 3 %) were the same as control breath holds, despite a 15 mmHg initial, transient decrease in MAP. Hyperoxia also had no effect on the apnoea‐induced increase in CFV (40 ± 4 %). We conclude that apnoea‐induced fluctuations in CFV were caused primarily by increases and decreases in arterial partial pressure of CO2 (Pa,CO2) and that sympathetic nervous system activity was not required for either the initiation or the maintenance of the cerebrovascular response to hyper‐ and hypocapnia. Increased MAP or other unknown influences of autonomic activation on the cerebral circulation played a smaller but significant role in the apnoea‐induced increase in CFV; however, negative intrathoracic pressure and the small amount of oxyhaemoglobin desaturation caused by 20 s apnoea did not affect CFV.

Effect of radial artery harvest on collateral forearm blood flow and digital perfusion

Background: Changes describing digital and forearm circulation after radial artery harvest have been reported infrequently. Methods: This prospective study examined digital perfusion and forearm collateral circulation preoperatively and postoperatively in patients who underwent coronary artery bypass grafting with radial artery free grafts. Noninvasive evaluation was conducted with digital photoelectric plethysmography and color flow and pulsed Doppler studies. Results: Thumb perfusion index decreased from 1.25 to 0.84 (30%, P <.001) in the unoperated extremities and from 1.23 to 0.80 (36%) in the operated extremities (P <.001). Doppler studies in extremities after radial artery harvest demonstrated an increase in ulnar artery diameter from 3.87 to 4.66 mm (15.7%, P <.001) and a rise in ulnar blood flow velocity from 38.96 to 48.46 cm/s (17.4%) preoperatively to 8 weeks postoperatively (P <.001). No hand ischemia was noted. Conclusions: Our study identified a mild reduction in digital perfusion and an increase in ulnar artery flow velocity and diameter with no clinical sequelae or compromise in hand function after radial artery harvest in properly selected patients.J Thorac Cardiovasc Surg 2002;123:512-6

Base heart rate during sleep in hypertensive and normotensive subjects.

Many studies have reported that the resting heart rate (HR) is intimately related to the prognosis of cardiovascular disease. However, HR in the waking state is influenced by psychological and physical activity and has low reproducibility. To measure the base HR (minimum and stable HR during sleep) with ease, we developed a wristwatch-type HR recorder. We then investigated the pathophysiological significance of the base HR. The subjects were 158 patients (82 men and 76 women) with essential hypertension (HT) on no medication and 204 normotensive (NT) subjects (105 men and 99 women, matched for age). On the basis of pulse waves from the wristwatch-type photoelectric plethysmograph, using a blue sensor with a wavelength of 450 nm, HR was recorded easily minute by minute during sleep time. In addition, 40 (23 men and 17 women) of the HT patients were hospitalized. Their cardiac index (CI) and stroke volume index (SVI) were measured by means of the cuvette method during waking time and night-time deep sleep when their HR had reached a minimum level. Mean base HR (HRo) in NT subjects was 49+/-4 beats per minute (bpm) and tended to rise with increasing age (r = 0.51, P < 0.01). In HT patients, HR0 was significantly higher: 60+/-7 bpm (P < 0.01). CI of HT patients, measured during night-time deep sleep, maintained a stable value of 2.45+/-0.36 l/min per m2. SVI in patients whose HR0 was above 60 was significantly lower than that in patients whose HR0 was below 60 (37+/-4.5: 45+/-4.8 ml/m2, P < 0.01). Corresponding differences in mean HR and SVI during waking or night-time, became smaller. These findings suggest that there is a close relation between base HR and cardiac function caused by such conditions as age and hypertension. This relation became indistinct during waking time. Moreover, the wristwatch-type HR recorder appears to be a useful tool for measuring base HR.