Kenta Matsumura

Comparison between red, green and blue light reflection photoplethysmography for heart rate monitoring during motion

Reflection photoplethysmography (PPG) using 530 nm (green) wavelength light has the potential to be a superior method for monitoring heart rate (HR) during normal daily life due to its relative freedom from artifacts. However, little is known about the accuracy of pulse rate (PR) measured by 530 nm light PPG during motion. Therefore, we compared the HR measured by electrocadiography (ECG) as a reference with PR measured by 530, 645 (red), and 470 nm (blue) wavelength light PPG during baseline and while performing hand waving in 12 participants. In addition, we examined the change of signal-to-noise ratio (SNR) by motion for each of the three wavelengths used for the PPG. The results showed that the limit of agreement in Bland-Altman plots between the HR measured by ECG and PR measured by 530 nm light PPG (±0.61 bpm) was smaller than that achieved when using 645 and 470 nm light PPG (±3.20 bpm and ±2.23 bpm, respectively). The ΔSNR (the difference between baseline and task values) of 530 and 470nm light PPG was significantly smaller than ΔSNR for red light PPG. In conclusion, 530 nm light PPG could be a more suitable method than 645 and 470nm light PPG for monitoring HR in normal daily life.

iPhysioMeter: A new approach for measuring heart rate and normalized pulse volume using only a smartphone

Heart rate (HR) and normalized pulse volume (NPV) are physiological indices that have been used in a diversity of psychological studies. However, measuring these indices often requires laborious processes. We therefore developed a new smartphone program, named iPhysioMeter, that makes it possible to measure beat-by-beat HR and ln NPV using only a smartphone. We examined its accuracy against conventional laboratory measures. Mental stress tasks were used to alter HR and ln NPV in 12 participants. Bland–Altman analyses revealed negligible proportional bias for HR and ln NPV or for their change values, expressed as ΔHR and Δln NPV. However, a relatively large fixed bias did emerge for ln NPV, as well as a small one for Δln NPV, although both were within the limits of agreement. These findings suggest that iPhysioMeter can yield valid measures of the absolute level of HR and of relative changes in ln NPV.

iPhone 4s Photoplethysmography: Which Light Color Yields the Most Accurate Heart Rate and Normalized Pulse Volume Using the iPhysioMeter Application in the Presence of Motion Artifact?

Recent progress in information and communication technologies has made it possible to measure heart rate (HR) and normalized pulse volume (NPV), which are important physiological indices, using only a smartphone. This has been achieved with reflection mode photoplethysmography (PPG), by using a smartphone’s embedded flash as a light source and the camera as a light sensor. Despite its widespread use, the method of PPG is susceptible to motion artifacts as physical displacements influence photon propagation phenomena and, thereby, the effective optical path length. Further, it is known that the wavelength of light used for PPG influences the photon penetration depth and we therefore hypothesized that influences of motion artifact could be wavelength-dependant. To test this hypothesis, we made measurements in 12 healthy volunteers of HR and NPV derived from reflection mode plethysmograms recorded simultaneously at three different spectral regions (red, green and blue) at the same physical location with a smartphone. We then assessed the accuracy of the HR and NPV measurements under the influence of motion artifacts. The analyses revealed that the accuracy of HR was acceptably high with all three wavelengths (all rs > 0.996, fixed biases: −0.12 to 0.10 beats per minute, proportional biases: r = −0.29 to 0.03), but that of NPV was the best with green light (r = 0.791, fixed biases: −0.01 arbitrary units, proportional bias: r = 0.11). Moreover, the signal-to-noise ratio obtained with green and blue light PPG was higher than that of red light PPG. These findings suggest that green is the most suitable color for measuring HR and NPV from the reflection mode photoplethysmogram under motion artifact conditions. We conclude that the use of green light PPG could be of particular benefit in ambulatory monitoring where motion artifacts are a significant issue.

Physiological measurements and analyses in motor sports: a preliminary study in racing kart athletes

Abstract The aims of this study were to assess methods for performing physiological measurements in motor sports, and to carry out a preliminary study in athletes participating in kart racing. The measurement of physiological variables in motor sports is practically challenging, largely due to the restricted space available for sensors and instrumentation and to movement artefacts from drivers operations and car vibration, hence the paucity of publications. We performed a preliminary study of amateur racing kart athletes to assess the performance of basic measurement apparatus and to collect preliminary data on the possible influences of gravity on cardiovascular activity. We measured the vector magnitude of acceleration (G), instantaneous heart rate using electrocardiography, blood pressure with a wrist sphygmomanometer, eardrum temperature (taken as a measure of core body temperature) with a radiation thermometer, and lap time. The instrumentation functioned satisfactorily during karting on a racing circuit. In all participants during driving, heart rate was maintained at approximately 150 beats · min−1. Time-frequency analysis of all heart rate data was performed to evaluate cardiac control mechanisms and this suggested that the observed rise in heart rate could be due to sympathetic acceleration. Furthermore, while we do not have sufficient data to draw firm conclusions, it is suggested that the rise in heart rate could be related to the G stresses to which the drivers were subjected. Cross-correlation analysis of the G and heart rate signals was performed in one participant and this showed a statistically significant correlation. We also found a statistically significant decrease in blood pressure (P<0.01) and a rise in eardrum temperature (P<0.01) immediately after the driving period. We conclude that although current sensors and instrumentation can allow basic monitoring of physiological variables in motor sport athletes, further developments are needed to allow more detailed investigations to be performed. Cardiovascular activity in response to G stresses warrants particular detailed investigation.

Validation of normalized pulse volume in the outer ear as a simple measure of sympathetic activity using warm and cold pressor tests: towards applications in ambulatory monitoring

Normalized pulse volume (NPV) derived from the ear has the potential to be a practical index for monitoring daily life stress. However, ear NPV has not yet been validated. Therefore, we compared NPV derived from an index finger using transmission photoplethysmography as a reference, with NPV derived from a middle finger and four sites of the ear using reflection photoplethysmography during baseline and while performing cold and warm water immersion in ten young and six middle-aged subjects. The results showed that logarithmically-transformed NPV (lnNPV) during cold water immersion as compared with baseline values was significantly lower, only at the index finger, the middle finger and the bottom of the ear-canal. Furthermore, lnNPV reactivities (ΔlnNPV; the difference between baseline and test values) from an index finger were significantly related to ΔlnNPV from the middle finger and the bottom of the ear-canal (young: r = 0.90 and 0.62, middle-aged: r = 0.80 and 0.58, respectively). In conclusion, these findings show that reflection and transmission photoplethysmography are comparable methods to derive NPV in accordance with our theoretical prediction. NPV derived from the bottom of the ear-canal is a valid approach, which could be useful for evaluating daily life stress.

Docosahexaenoic acid for selective prevention of posttraumatic stress disorder among severely injured patients: a randomized, placebo-controlled trial

OBJECTIVE Docosahexaenoic acid (DHA) might help prevent or attenuate posttraumatic stress disorder (PTSD) symptoms. We examined the efficacy and safety of DHA for preventing PTSD (DSM-IV) after severe accidental injury. METHOD From December 2008 to August 2013, we conducted a randomized, double-blind, placebo-controlled trial of 110 accident-injured patients consecutively admitted to an intensive care unit of the National Disaster Medical Center in Tokyo, Japan. All patients were taught about their psychological reactions to accidental injury for 20 minutes and were randomly assigned to receive 1,470 mg/d of DHA plus 147 mg/d of eicosapentaenoic acid (EPA; n = 53) or placebo (n = 57) for 12 weeks. The primary outcome was total score on the Clinician-Administered PTSD Scale (CAPS) at 3-month follow-up. Secondary outcomes included PTSD diagnosis (full-blown or partial PTSD). Adherence to the interventions was assessed by erythrocyte fatty acid composition. RESULTS At 3 months, the CAPS total score revealed no differences between the 2 groups (10.78 in the DHA group vs 9.22 in the placebo group; n = 100; P = .572). We found that 11.1% of the DHA group and 5.5% of the placebo group developed PTSD. The erythrocyte level of DHA and EPA in the DHA group was significantly elevated compared to the placebo group (P < .01). CONCLUSIONS Docosahexaenoic acid supplementation was not superior to placebo for the secondary prevention of PTSD symptoms at 3 months after severe accidental injury. The efficacy of a different ratio of DHA and EPA and higher doses of omega-3 fatty acids as secondary prevention of PTSD remains to be determined. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT00671099.

Tachikawa project for prevention of posttraumatic stress disorder with polyunsaturated fatty acid (TPOP): study protocol for a randomized controlled trial

BackgroundPreclinical and clinical studies suggest that supplementation with omega-3 fatty acids after trauma might reduce subsequent posttraumatic stress disorder (PTSD). To date, we have shown in an open trial that PTSD symptoms in critically injured patients can be reduced by taking omega-3 fatty acids, hypothesized to stimulate hippocampal neurogenesis. The primary aim of the present randomized controlled trial is to examine the efficacy of omega-3 fatty acid supplementation in the secondary prevention of PTSD following accidental injury, as compared with placebo. This paper describes the rationale and protocol of this trial.Methods/designThe Tachikawa Project for Prevention of Posttraumatic Stress Disorder with Polyunsaturated Fatty Acid (TPOP) is a double-blinded, parallel group, randomized controlled trial to assess whether omega-3 fatty acid supplementation can prevent PTSD symptoms among accident-injured patients consecutively admitted to an intensive care unit. We plan to recruit accident-injured patients and follow them prospectively for 12 weeks. Enrolled patients will be randomized to either the omega-3 fatty acid supplement group (1,470 mg docosahexaenoic acid and 147 mg eicosapentaenoic acid daily) or placebo group. Primary outcome is score on the Clinician-Administered PTSD Scale (CAPS). We will need to randomize 140 injured patients to have 90% power to detect a 10-point difference in mean CAPS scores with omega-3 fatty acid supplementation compared with placebo. Secondary measures are diagnosis of PTSD and major depressive disorder, depressive symptoms, physiologic response in the experiment using script-driven imagery and acoustic stimulation, serum brain-derived neurotrophic factor, health-related quality of life, resilience, and aggression. Analyses will be by intent to treat. The trial was initiated on December 13 2008, with 104 subjects randomized by November 30 2012.DiscussionThis study promises to be the first trial to provide a novel prevention strategy for PTSD among traumatized people.Trial registrationClinicalTrials.gov Identifier NCT00671099

Fish consumption and cardiovascular response during mental stress

BackgroundFrequent fish consumption is related to a lower risk of coronary heart disease. However, the physiological mechanisms underlying this cardioprotective effect are as yet unknown. We therefore examined certain cardiovascular physiological variables of fish eaters during rest, whilst conducting mental arithmetic, and during recovery.FindingsThe participants were 12 fish eaters (eating baked fish more than 3–4 times/week) and 13 controls (eating fish less than 1–2 times/week). Analysis of the collected data revealed that heart rate, blood pressure, and pulse wave velocity were significantly lower and pre-ejection period and baroreflex sensitivity were significantly higher in the fish eaters than in the controls during both rest and mental arithmetic, and that systolic and mean blood pressure recovery from mental arithmetic were faster in the fish eaters than in the controls.ConclusionsThese findings suggest a possible physiological mechanism that may explain why frequent fish consumption reduces coronary heart disease risk.

Potential impact of propofol immediately after motor vehicle accident on later symptoms of posttraumatic stress disorder at 6-month follow up: a retrospective cohort study.

IntroductionCritically injured patients are at risk of developing posttraumatic stress disorder (PTSD). Propofol was recently reported to enhance fear memory consolidation retrospectively. Thus, we investigated here whether administration of propofol within 72 h of a motor vehicle accident (MVA) affects the subsequent development of PTSD symptoms.MethodsWe examined data obtained from a prospective cohort study of MVA-related injured patients, admitted to the intensive care unit of a general hospital. We investigated the effect of propofol administration within 72 h of MVA on outcome. Primary outcome was diagnosis of full or partial PTSD as determined by the Clinician-Administered PTSD Scale (CAPS) at 6 months. Secondary outcomes were diagnosis of full or partial PTSD at 1 month and CAPS score indicating PTSD at 1 and 6 months. Multivariate analysis was conducted adjusting for being female, age, injury severity score (ISS), and administration of ketamine or midazolam within 72 h of MVA.ResultsAmong 300 patients recruited (mean ISS, 8.0; median Glasgow Coma Scale (GCS) score, 15.0; age, 18 to 69 years), propofol administration showed a higher risk for full or partial PTSD as determined by CAPS at 6 months (odds ratio = 6.13, 95% confidence interval (CI): 1.57 to 23.85, P = 0.009) and at 1 month (odds ratio = 1.31, 95% CI: 0.41 to 4.23, P = 0.647) in the multivariate logistic regression. Multivariate regression analysis showed a trend toward adverse effects of propofol on PTSD symptom development at 6 months after MVA (β = 4.08, 95% CI: -0.49 to 8.64, P = 0.080), but not at 1 month after MVA (β = -0.42, 95% CI: -6.34 to 5.51, P = 0.890).ConclusionsThese findings suggest that using propofol in the acute phase after MVA might be associated with the development of PTSD symptoms 6 months later. However, since the design of this study was retrospective, these findings should be interpreted cautiously and further study is warranted.

Cardiovascular hemodynamic effects of Red Bull® Energy Drink during prolonged, simulated, monotonous driving.

PurposeThe purpose of this study was to investigate the cardiovascular hemodynamic effects of Red Bull® Energy Drink during prolonged, simulated, monotonous driving.MethodsThis was a double-blind, within-subjects-design, crossover study. Twelve healthy volunteers (21.7 ± 0.8 years old) experienced each of three conditions at various times: 1) consumption of Red Bull® Energy Drink; 2) consumption of placebo-controlled drink; and 3) no test drink. All subjects undertook 90-min periods of simulated monotonous driving, during which physiological measurements were made. The variables recorded were cardiovascular indices, i.e., mean blood pressure (MBP), cardiac output (CO), electrocardiogram RR interval (RR), total peripheral-vascular resistance (TPR: = MBP/CO), and normalized pulse volume (NPV). Additional parameters were the standard deviation of lateral position, i.e., the weaving of the car, and subjective rating of sleepiness.ResultsCO, RR, and TPR during the monotonous task were significantly different in those consuming the energy drink as compared with those receiving the placebo and as compared with no drink values. The energy drink elicited a cardiac-dominant reaction pattern, while the other conditions demonstrated the vascular-dominant reaction pattern typically observed in monotonous driving tasks. The observed differences indicate the cardiovascular system being more aroused with the energy drink.ConclusionThe effects of Red Bull® Energy Drink were reflected in cardiovascular hemodynamic phenomena especially to the heart function, and we conclude that consumption of this drink before long-distance driving in non-sleepy drivers could facilitate more physiologically active, and possibly safer, driving.