Acceleration Data Logger Research Articles

The secret lives of wedgefish: first insights into fine-scale behaviour and movement ecology of a globally imperilled ray

Wedgefishes have recently been recognised as one of the most imperilled marine fish families worldwide. However, many knowledge gaps about their biology and ecology hinder conservation efforts. Here we used a combination of acoustic telemetry and acceleration datalogger technology to gain fundamental insights into the fine-scale behaviour, habitat use, size of activity spaces, and residency of adult female bottlenose wedgefish (Rhynchobatus australiae) in the Ningaloo region of northwestern Australia. Acoustic tracking data over one year demonstrated that female bottlenose wedgefish continuously resided in a relatively small area of a productive coral reef lagoon. Acceleration data revealed that bottlenose wedgefish were nocturnal, with time of day having a greater influence on activity than tidal patterns. Bottlenose wedgefish also increased activity with seasonally increasing temperatures. We identified several discrete behavioural signatures in the acceleration data, inferred to correspond to chafing, settling/burying behaviour, foraging behaviour, and escape behaviour, based on their kinematics. Further observations are required to confirm these behaviours with certainty. Additionally, according to datalogger and acoustic data, tagged bottlenose wedgefish rarely inhabited areas greater than 2 m deep. Together, these first insights into behaviour and habitat use of adult female bottlenose wedgefish highlight the importance of nearshore habitats for this species and indicate that they may be highly resident to specific areas. Our findings provide important insight into the conservation of bottlenose wedgefish in northwestern Australia, including potential effectiveness of protected areas and interactions with specific anthropogenic threats such as shoreline development and recreational beach fishing.

Changes in courtship prior to oviposition in chum salmon (Oncorhynchus keta) and male preference for female body size

AbstractMale chum salmon display a courtship behaviour involving an actively “quivering” against female, which is essential for female orgasm. Because generally male prefer larger female, we determined whether the elements of quivering such as the number, the amplitude, and the distance are affected by female body size. Additionally, quivering changes towards oviposition; therefore, we also identified the essential time for the male to succeed in his courtship behaviour. We conducted two experiments to measure quivering parameters: (i) measuring the number and the amplitude of quivering by the acceleration data logger and (ii) measuring the distance between sexes during quivering by observation of recorded video. From the first experiment, there was no significant relationship between the ratio of female‐to‐male body lengths and the number and the amplitude of quivering, while an important relationship between the body length ratio and the distance between sexes from the second experiment. Therefore, we think the distance is more significant than the number or vigour of quivering for male choice, and males quiver more closely to a larger female to increase reproductive success. In addition, when the body length ratio of the sexes is 1.01, the distance during quivering is the shortest. So, there is a possibility that the reproduction of chum salmon is based on size‐assortative mating. And both experiments also showed that male quiver passively as spawning approaches. We suggest that males may not quiver actively for smooth mating as females spawning approaches.

Post-release mortality, recovery, and stress physiology of blacknose sharks, Carcharhinus acronotus, in the Southeast U.S. recreational shark fishery

The post-release mortality (PRM) rate of sharks can be an important factor in estimating overall mortality in stock assessments. However, the accuracy of PRM rates is dependent on our ability to evaluate mortality under realistic fishing practices and conditions. In the Southeast U.S. recreational rod-and-reel fishery, we worked directly with recreational fishing captains to investigate the PRM of blacknose sharks, Carcharhinus acronotus. These sharks are primarily discarded alive in this fishery, but as PRM for this species has yet to be investigated, it is challenging to address the impact of recreational fishing on blacknose shark populations and assess the effectiveness of management measures. We examined PRM by first capturing blacknose sharks (n = 63) with South Carolina and Florida charter captains. Blood samples were taken immediately after capture to evaluate blood-based indicators of capture stress, and sharks were fit with acceleration data logger tags (measuring tri-axial acceleration, depth, and water temperature) to monitor fine-scale behavior and mortality for up to 136 h post-release. Sharks captured in warmer water temperatures displayed increased lactate and decreased pH, the latter of which was more pronounced in females. Fine-scale behavior profiles revealed survivorship for most animals and impaired swimming and mortality in others. All mortality events were attributed to predation events, as evidenced by marked changes in movement that deviated from recorded blacknose shark swimming behavior. Our estimated PRM rates ranged from 3.7% to 41.5%, depending on the release condition of the animal (i.e., increasing level of swimming impairment). Handling duration negatively influenced release condition, indicating extended handling durations increased the probability of a shark showing impaired swimming. Fishery-scale PRM was estimated as 8.5% when considering the distribution of release conditions observed throughout the study. Tag data showed that surviving sharks took an average of 11.7 h to recover and resume normal swimming behavior, with recovery taking longer in warmer water. The overall post-release mortality rate in this fishery is relatively low but may still impact the stock if the total catch is high enough throughout the fishery. Findings from our study will enhance estimates of fishing mortality in future stock assessments and help formulate best practices to reduce the overall fishing mortality of blacknose sharks.

Triple apheresis platelet concentrate quality after pneumatic tube system, conveyor box, and courier transport: An observational study.

Background and AimsPlatelets are prone to activation from handling; they are therefore transported as gently as possible, most commonly by courier. Speedier methods like pneumatic tube system (PTS) transport could improve patient care but may subject platelets to mechanical stress. To test the impact of mechanical stress caused by transport, we compared a PTS with a conveyor box and courier transport on apheresis platelet function.MethodsFourteen apheresis platelet concentrate triple donations were analyzed by light transmission aggregometry (LTA), rotational thrombelastometry (ROTEM), and flow cytometry before and after indoor transport over 800 m by PTS, conveyor, and courier, respectively, while recording shocks and vibrations with a high‐frequency acceleration data logger. Shock index scores were calculated as shock intensity (g‐force) times frequency.ResultsThe shock index was 81 for courier, 6279 for conveyor, and 9075 for PTS. Flow cytometry revealed no significant difference in platelet surface expression of CD62p before (16%) and after transport via courier (15%), conveyor (14%), or PTS (16%). LTA with adenosine phosphate and thrombin receptor‐activating peptide‐6 resulted in comparable platelet aggregation for courier, conveyor, and PTS. ROTEM assays showed no relevant differences in coagulation time, clot formation time, and maximum clot firmness between transport modes.ConclusionThough the mechanical challenge was smallest with courier transport, there were no significant differences in platelet activation or aggregation between the three transport modes. These data contradict restrictions on the use of PTSs for platelet concentrate transport.

Monitoring tidal hydrology in coastal wetlands with the “Mini Buoy”: applications for mangrove restoration

Abstract. Acquiring in situ data of tidal flooding is key for the successful restoration planning of intertidal wetlands such as salt marshes and mangroves. However, monitoring spatially explicit inundation time series and tidal currents can be costly and technically challenging. With the increasing availability of low-cost sensors and data loggers, customized solutions can now be designed to monitor intertidal hydrodynamics with direct applications for restoration and management. In this study, we present the design, calibration, and application of the “Mini Buoy”, a low-cost underwater float containing an acceleration data logger for monitoring tidal inundation characteristics and current velocities derived from single-axis equilibrium acceleration (i.e. logger tilt). The acceleration output of the Mini Buoys was calibrated against water-level and current-velocity data in the hypertidal Bay of Fundy, Canada, and in a tidally reconnected former aquaculture pond complex in North Sumatra, Indonesia. Key parameters, such as submersion time and current velocities during submergence, can be determined over several months using the Mini Buoy. An open-source application was developed to generate ecologically meaningful hydrological information from the Mini Buoy data for mangrove restoration planning. We present this specific SE Asian mangrove restoration application alongside a flexible concept design for the Mini Buoy to be customized for research and management of intertidal wetlands worldwide.

An Analysis of Sheep Grazing and Ingredients of Grass in Pasturelands on the Island of Yagishirito with GPS and Acceleration Data Logger

An Analysis of Sheep Grazing and Ingredients of Grass in Pasturelands on the Island of Yagishirito with GPS and Acceleration Data Logger

Behavioural characteristics of loggerhead turtles (Caretta caretta) in a submerged bag net of a setnet observed in a bycatch simulation and the development of a turtle releasing device

Abstract A turtle releasing device (TRD) can reduce the mortality of bycatch in setnets. Turtles that have entered the submerged bag net of setnets repeatedly push their heads up against the ceiling net (referred to here as a push‐up) in an effort to ascend to breathe. To aid the successful escape of turtles from the setnet, it is essential to understand the turtle's push‐up behaviour, as they need to reach the TRD and open its flap door. The objectives of this study were to clarify when turtles start to perform push‐ups, how these push‐ups change, and what factors affect push‐ups under the simulated condition of bycatch. A depth, temperature, and tri‐axial acceleration data logger and a video camera were employed to determine vertical movement, ambient temperature, the level of activity, and flipper beat frequency (FBF) of the turtles. Ten trials of 10–30 minutes for five subadult loggerhead turtles (Caretta caretta) were conducted using a submerged bag net (30 × 10 × 10 m) of a setnet in Mie Prefecture, Japan. Turtles started to perform push‐ups 5.1 ± 3.3 minutes after the start of each trial. FBF increased as more time elapsed in 35% of ascent phases recorded, and the level of activity during the following push‐ups was significantly higher than during other push‐ups. The level of activity in each sequence of push‐ups increased as more time elapsed; however, it started to decrease from 9.8 minutes after the first push‐up at the earliest. Therefore, the TRD should be designed to enable turtles to escape within approximately 10 minutes. The number of push‐ups in a single sequence, the activity level, and FBF were affected by water temperature. Therefore, the closing force of the TRD flap door needs to be changed according to the different seasons and regions.

Road surface condition monitoring system utilizing motorcycle (ROCOM) – System development, validation and field test

Motorcycles are the riskiest mode of travel in Malaysia, however motorcycles are also very sensitive to the road surface condition. Thus, by taking advantage of this, a system of applications that analyses motorcycle motion and mapped out risky road sections was developed, i.e. ROCOM. The system consists of three major components, i.e. acceleration data logger smart phone app, risk mapping web-based app and a visual tracking app utilizing the phone. ROCOM is able to detect adverse acceleration (> 2g) on the road surface similar to the High Accuracy GPS Data Logging for Vehicle Testing (VBOX). Risk mapping validation along a section of the motorcycle lane along Federal Route 2 shows that ROCOM have the similar risk-mapping pattern, but superior tracking capability that the VBOX. The pilot and field test results showed that ROCOM works best when mounting the smartphone on the motorcycle handle bar or basket, and with successful detection rate of 62% of various road anomalies. In the future, once the system is fully developed, ROCOM intends to give road authorities cheaper and faster alternative to inspect road surface condition and also through crowdsourcing, motorcyclists can be warned of risky road condition ahead of their path.

Velocity optimization algorithm of 4-DOF robot end-effectors

To solve the problem velocity control for robot end-effectors trajectory planning in the Cartesian space, this paper studied the algorithm of the linear acceleration and deceleration. Moreover, it proposed a velocity optimization algorithm based on the displacement equivalent. Adjusting the speed size of the acceleration and deceleration, the algorithm reduced the velocity mutation due to the discretized interpolation equation. The algorithm then was applied to the linear and circular interpolation of 4-degree of freedom industrial robots, establishing the forward and inverse kinematics equation based on Denavit–Hartenberg (D–H) coordinate system with implementing the optimization algorithm in the motion control system. Next, the velocity of the end-effectors was tested using the acceleration sensor and data logger. The results of simulation and experiment showed that velocity optimization algorithm eliminated the acceleration point and decreased the deceleration point on the velocity mutation.

A miniaturized threshold-triggered acceleration data-logger for recording burst movements of aquatic animals.

Although animal-borne accelerometers are effective tools for quantifying the kinematics of animal behaviors, quantifying the burst movements of small and agile aquatic animals remains challenging. To capture the details of burst movements, accelerometers need to sample at a very high frequency, which will inevitably shorten the recording duration or increase the device size. To overcome this problem, we developed a high-frequency acceleration data-logger that can be triggered by a manually defined acceleration threshold, thus allowing the selective measurement of burst movements. We conducted experiments under laboratory and field conditions to examine the performance of the logger. The laboratory experiment using red seabream (Pagrus major) showed that the new logger could measure the kinematics of their escape behaviors. The field experiment using free-swimming yellowtail kingfish (Seriola lalandi) showed that the loggers trigger correctly. We suggest that this new logger can be applied to measure the burst movements of various small and agile animals.

Accuracy verification of tilt-angle estimation by split-beam echosounder: Comparison with acceleration data-logger data

Fish tilt-angle is one of the most important factors for fish target strength (TS) estimation, because the little change varies TS value dramatically. Split-beam echosounder collects a fish position with 3-D coordinates. Hence, if fish swim within acoustic beam continuously, the tilt-angle can be estimated from the gap between two positions easily. However, the accuracy of the estimation depends on performance of the echosounder. We verified accuracy of the estimated tilt-angle by comparing high-resolution angle from an acceleration data logger. Experiment was conducted at a large experimental tank (W:10m x D:5m x H:6m) in HRCFO. A 2-axis acceleration data logger (φ15 mm, L: 53 mm, M190L-D2GT, Little Leonardo, Inc.) was tethered into the tank, and towed at respective angle from -50 to 50 degree (1 degree pitch). Positions of the logger echos (from KCE300, Sonic Co., 120kHz) were exported by algorithms of Echoview7.1. After this process, the tilt-angles were calculated. 28 logger echos were identified from the acoustic data, and the estimated tilt-angles was from -45.59° to 32.87 °. Significant correlation of tilt-angles (logger vs. acoustic data) was found (p > 0.01, r2 = 0.90). This result shows high precision of the estimated tile angle from the split-beam echosounder data.

A validation of technologies monitoring dairy cow feeding, ruminating, and lying behaviors

The objective of this study was to evaluate commercially available precision dairy technologies against direct visual observations of feeding, rumination, and lying behaviors. Primiparous (n=24) and multiparous (n=24) lactating Holstein dairy cattle (mean ± standard deviation; 223.4±117.8 d in milk, producing 29.2±8.2kg of milk/d) were fitted with 6 different triaxial accelerometer technologies evaluating cow behaviors at or before freshening. The AfiAct Pedometer Plus (Afimilk, Kibbutz Afikim, Israel) was used to monitor lying time. The CowManager SensOor (Agis, Harmelen, Netherlands) monitored rumination and feeding time. The HOBO Data Logger (HOBO Pendant G Acceleration Data Logger, Onset Computer Corp., Pocasset, MA) monitored lying time. The CowAlert IceQube (IceRobotics Ltd., Edinburgh, Scotland) monitored lying time. The Smartbow (Smartbow GmbH, Jutogasse, Austria) monitored rumination time. The Track A Cow (ENGS, Rosh Pina, Israel) monitored lying time and time spent around feeding areas for the calculation of feeding time. Over 8 d, 6 cows per day were visually observed for feeding, rumination, and lying behaviors for 2 h after morning and evening milking. The time of day was recorded when each behavior began and ended. These times were used to generate the length of time behaviors were visually observed. Pearson correlations (r; calculated using the CORR procedure of SAS Version 9.3, SAS Institute Inc., Cary, NC), and concordance correlations (CCC; calculated using the epiR package of R version 3.1.0, R Foundation for Statistical Computing, Vienna, Austria) evaluated association between visual observations and technology-recorded behaviors. Visually recorded feeding behaviors were moderately correlated with the CowManager SensOor (r=0.88, CCC=0.82) and Track A Cow (r=0.93, CCC=0.79) monitors. Visually recorded rumination behaviors were strongly correlated with the Smartbow (r=0.97, CCC=0.96), and weakly correlated with the CowManager SensOor (r=0.69, CCC=0.59). Visually recorded lying behaviors were strongly correlated with the AfiAct Pedometer Plus (r >0.99, CCC >0.99), CowAlert IceQube (r >0.99, CCC >0.99), and Track A Cow (r >0.99, CCC >0.99). The HOBO Data Loggers were moderately correlated (r >0.83, CCC >0.81) with visual observations. Based on these results, the evaluated precision dairy monitoring technologies accurately monitored dairy cattle behavior.

The relationship between body angle and target strength of ribbonfish (Trichiurus japonicus) displaying a vertical swimming motion

AbstractDuring movement, the body angles of ribbonfish change, including a unique vertical swimming motion that influences their target strength (TS). In this study, we observed body angle changes in ribbonfish using an acceleration data logger and video recordings. Based on these data, variations in echo intensity in response to body angle changes were revealed using radiograph images of the swimbladder and the respective TS values. The frequency of a body angle >60° was 57.78% peak at 77°. The swimbladders were found to be slender ellipses inclined 3–4° upward from the body axis. The TS peaked (about −30 dB for the average pre-anal length of 223.9 ± 21.8 mm) when the body angle was horizontal or inclined 2–3° downward. The TS decreased substantially when the body angle was vertically inclined. From about 10° upward inclination to vertical, the TS fluctuated between −50 and −60 dB. In a comparison of the average TS values among body angle categories, the TS values for body angles grouped as ‘vertical’ (between 60° and 90°), showing static mode activity patterns in video recordings, were low (−55.7 ± 3.9 dB, Mean ± SD), whereas those for the horizontal body angle (between 0° and 30°) category, comprising the active mode, were high (−47.0 ± 8.7 dB) (P-value < 0.01). In the natural habitat, ribbonfish are known to gather at the sea floor during the daytime. In contrast, at night they disperse and move actively while foraging. Consequently, their echo intensities in natural habitats change substantially in response to their diel changes in behavioural ecology. Additional measurements or theoretical models considering the influence of ribbonfish behaviour should be undertaken as a result of this study.

Fat King Penguins Are Less Steady on Their Feet.

Returning to the shore after a feeding sojourn at sea, king penguins often undertake a relatively long terrestrial journey to the breeding colony carrying a heavy, mostly frontal, accumulation of fat along with food in the stomach for chick-provisioning. There they must survive a fasting period of up to a month in duration, during which their complete reliance on endogenous energy stores results in a dramatic loss in body mass. Our aim was to determine if the king penguin’s walking gait changes with variations in body mass. We investigated this by walking king penguins on a treadmill while instrumented with an acceleration data logger. The stride frequency, dynamic body acceleration (DBA) and posture of fat (pre-fasting; 13.2 kg) and slim (post fasting; 11 kg) king penguins were assessed while they walked at the same speed (1.4km/h) on a treadmill. Paired statistical tests indicated no evidence for a difference in dynamic body acceleration or stride frequency between the two body masses however there was substantially less variability in both leaning angle and the leaning amplitude of the body when the birds were slimmer. Furthermore, there was some evidence that the slimmer birds exhibited a decrease in waddling amplitude. We suggest the increase in variability of both leaning angle and amplitude, as well as a possibly greater variability in the waddling amplitude, is likely to result from the frontal fat accumulation when the birds are heavier, which may move the centre of mass anteriorly, resulting in a less stable upright posture. This study is the first to use accelerometry to better understand the gait of a species within a specific ecological context: the considerable body mass change exhibited by king penguins.

A float-release package for recovering data-loggers from wild sharks

The rapidly expanding use of high-resolution data-loggers to study marine vertebrates presents a wealth of new opportunities for understanding the behavior, physiology, and ecology of these animals in situ. It also presents a number of new logistical challenges, one of the biggest of which is the need to physically recover the tag in order to acquire data, thus, a novel data-logger release and recovery package was designed and tested. This package consisted of a microsphere-resin float, very high frequency (VHF) transmitter, and galvanic timed release (GTR) device which allowed acceleration data logger (ADL) tags to remain on free-living sharks for several days before detaching from the fin. Upon release, tags floated to the surface and were located using a VHF receiver and yagi antenna. This method has been used successfully on blacktip, bull, nurse, and white sharks to produce an overall recovery rate of 95.7% on 47 deployments over periods of 1–111h and shark displacement distances up to 35km. This represents a cost-effective method for recovering data-loggers from sharks and large teleosts.

Technical note: Evaluation of a system for monitoring individual feeding behavior and activity in beef cattle.

Behavioral observations are important to detect illness in beef cattle. However, traditional observation techniques are time and labor intensive and may be subjective. The objective was to validate a system for monitoring individual feeding behavior and activity in beef cattle (Fedometer [FEDO]; ENGS, Rosh Pina, Israel). Sixteen steers (initial BW ± SD = 326 ± 46 kg) were fitted with data loggers (FEDO) on their left front leg and housed in a pen with a feedbunk equipped with an antenna emitting an electromagnetic field that reached 30 ± 2 cm in front of the feedbunk. Feedbunk attendance (duration of visit and frequency of meals) measured by FEDO was compared with live observations (27 observational periods lasting between 72 and 240 min; mean 126 min). Lying time and frequency of lying bouts were compared with previously validated accelerometers fitted to the hind leg (10 steers equipped for 10 to 12 d; HOBO Pendant G Acceleration Data Logger [HOBO]; Onset Computer Corporation, Pocasset, MA). Step counts were compared with video recordings (15 observations for 6-min intervals in 6 steers). Concordance correlation coefficients (CCC), accounting for repeated measures, and limits of agreement were computed. Comparison between FEDO and observed time at the feedbunk yielded a CCC of 0.98 (95% confidence interval [CI] 0.97-0.99). All 68 meal events observed were recorded by FEDO. However, FEDO recorded 4 meal events during the 27 observational periods that were not observed. Lying time measured by HOBO and FEDO were highly correlated (CCC = 0.98; 95% CI 0.97-0.99). However, frequency of lying bouts measured by FEDO was only moderately correlated to HOBO (CCC = 0.71; 95% CI 0.63-0.77); FEDO underestimating the number of lying bouts (on average, 0.4 fewer bouts per 6 h). Step count by FEDO was moderately correlated to video observations (CCC = 0.75; 95% CI 0.49-0.89); FEDO overestimating the number of steps (on average, 5 more steps per 6 min). In conclusion, the FEDO system accurately measured duration of feedbunk attendance, frequency of meals, and lying time. However, it overestimated the number of steps and underestimated the frequency of lying bouts.

Flexible foraging behaviour in a marine predator, the Masked booby (Sula dactylatra), according to foraging locations and environmental conditions

Flexible foraging behaviour allows marine predators to exploit shifting prey diversity and adjust to spatio-temporal changes in the distribution of prey. In diving marine predators, the number of dives within a dive bout, distances between dives in a bout and distances between bouts have been related to prey patch size, density of prey patches and prey encounter rates, respectively. In addition, the predictability of prey encounters can be examined by studying individuals' foraging site fidelity. Based on this, we examined in chick-rearing Masked boobies (Sula dactylatra) from Phillip Island (South-west Pacific), Australia, using GPS and depth–acceleration data logger, how these parameters changed over time (two early breeding phases and one late phase over two years) and according to foraging locations and environmental conditions. Results revealed that birds foraged in two distinct areas: over a nearby shallow shelf (“local area”) and over distant deeper waters (“distant area”). Birds searched for prey in the distant area only during the two latest study periods, indicating less favourable foraging conditions within the local area during this time, although persistent higher chlorophyll-a concentrations in the local area were indicative of an upwelling. Our data suggest that birds experienced a trade-off between local and distant trips: although the strong foraging site fidelity within the local area suggests that prey encounters were predictable, smaller dive bouts indicated smaller prey patches, i.e. less prey nearby the colony during the two latest study periods. As a consequence, adults undertook distant trips to forage in larger prey patches, as inferred from larger dive bouts, but distances between these dive bouts were more variable and birds showed no foraging site fidelity, indicating less predictable prey encounters. Local trips presumably allow a high feeding frequency of the chick, while distant trips allow adults to replenish their own body reserves. Observed changes in foraging conditions, although the underlying causes were not determined, appear to be within the eco-physiological limitations of Masked boobies. However, further studies are required to determine the degree of this limitation, especially as changes in the spatio-temporal availability of prey can be expected to increase with global warming and changing oceanic processes.

Detection of Grooming Behaviours with an Acceleration Data Logger in a Captive Northern Fur Seal (Callorhinus ursinus)

Detection of Grooming Behaviours with an Acceleration Data Logger in a Captive Northern Fur Seal (Callorhinus ursinus)

Association between the impairment of skin temperature rhythm and hypertension

An increasing amount of bibliography relates hypertension to certain sleep disorders and reduced sleep quality. Wrist temperature (WT) circadian rhythm is related to autonomic balance, thermoregulation, sleep propensity and sleep wake cycle; hence, it has been proposed as possible screening technique to assess blood pressure (BP) dipping status. Thus, the aim of this work is to determine of hypertension is associated to changes in WT rhythm. 33 healthy subjects (21–63 years old) were monitoring for WT, Activity (A) and Position (P) by means of two data loggers, an Ibuttom device (ThermoChron®, Data loggers I- button) and a Hobo actimeter (Hobo® Pendant G, Acceleration Data Logger). Ambulatory BP was determined during 24 h using a BP monitor (Spacelabs® Medical), with a sampling rate of one measure every 20 min during day and every 40 min during night. An alertness variable (TAP) was calculated averaging normalized values for WT, A and P. Sleep time was considered when P < 30 o and A < 20 o /min. Hypertensive patients showed increased heart rate when were compared with normotensive patients (79.94 ± 2.76 bpm vs. 71.00 ± 1.84 bpm, p < 0.05) and a significant decrease in WT during sleep period (34.22 ± 0.14 o C vs. 34.63 ± 0.09 o C, p < 0.05) and lower position values during daytime (47.83 ± 1.97 o vs. 52.57 ± 1.23 o , p < 0.05) respect to normotensive subjects, while no differences were founded in activity and TAP. Hypertension is closely related to a significant impairment in WT circadian rhythm, allowing differentiating between normotensive and hypertensive patients. In fact, lower nighttime WT values are connected to sleep disorders such as insomnia or sleep disordered breathing, which are related to higher nighttime blood pressure probably due to the increase in nocturnal sympathetic activation in hypertensive patients. Study supported by RETICEF (RD12/0043/0011), MINECO (BFU2010–21945-C02–01), and INNPACTO (IPT-2011–0833-900000) with FEDER cofounding to JAM, and a research fellowship to Antonio Martinez-Nicolas (University of Murcia).

Non dipping blood pressure pattern is related to an increase in daytime distal skin temperature

Introduction The circadian pattern of blood pressure (BP) is closely associated to sleep-wake cycle, target organs damage and cardiovascular events. Thus, BP circadian pattern diagnosis should be based on an objective procedure to determine patient’s actual sleep and wake time instead of standard sleep schedules. Wrist temperature (WT) rhythm is subordinated to the master circadian clock and it is related to autonomic balance, thermoregulation, sleep propensity and sleep wake cycle and also responds to postural changes. Thus, the purpose of this research is to determine accurately the BP pattern using circadian ambulatory monitoring and the association between WT rhythm and the BP dipping status. Materials and methods WT, Activity (A) and Position (P) were recorded during five days in 33 healthy subjects, aging from 21 to 63 years old, by means of two data loggers, an Ibuttom device (ThermoChron®,) and a Hobo actimeter (Hobo® Pendant G, Acceleration Data Logger). Ambulatory BP was determined during 24 h using a BP monitor (Spacelabs® Medical) with a sampling rate of one measure every 20 min during day and every 40 min during night. An alertness variable (TAP) was calculated averaging normalized values for WT, A and P. Sleep time was automatically considered when P 30 o and A 25 o /min. Results Non-dipper subjects showed higher systolic BP during nighttime (124.62 ± 6.00 mmHg vs 112.36 ± 2.50 mmHg) as it was expected. In addition, we found a significant increase in WT during daytime (33.81 ± 0.18 o C vs 32.88 ± 0.19 o C), but not during nighttime, and higher TAP values during nighttime (0.19 ± 0.03 a.u. vs. 0.14 ± 0.01 a.u.) in non-dipper compared with dipper subjects, while no differences were found for activity and body position. Conclusion Considering individual sleep pattern when evaluating BP pattern provides a more accurate diagnosis of dipping pattern. The use of P, A and WT information might change the interpretation of ambulatory BP monitoring data and improve the diagnosis of circadian BP pattern. Furthermore, circadian monitoring could distinguish between dipper and non-dipper pattern using daytime WT values. Acknowledgements Study supported by RETICEF (RD12/0043/0011), MINECO (BFU2010–21945-C02–01), and INNPACTO (IPT-2011–0833-900000) with FEDER cofounding to JAM, and a research fellowship to Antonio Martinez-Nicolas (University of Murcia).