Measurement of Right Ventricular Blood Temperature During Exercise as a Means of Rate Control in Physiological Pacemakers

Several biological parameters have been suggested for rate control in physiological pacemakers in the past. Up to now, measurements of central venous blood temperature have been mostly done on dogs. We studied central venous blood temperature and heart rate in 14 healthy volunteers under conditions of treadmill and bicycle exercise with different workloads. A custom made 5F lead with a thermistor incorporated near the tip was placed at the right ventricle under fluoroscopic control. Temperature was recorded with an accuracy of 1/100°C on a digital memory device at a sampling rate of 5–10 s. We found the increase in blood temperature to be not only a function of absolute workloads but also a function of the individual's maximum exercise tolerance. Independent of the absolute increase in heart rate and temperature at a given workload, the individual's relation of increase in temperature and heart rate was found to be highly correlating (r = 0.9095). At a load of 100 W, we found a mean increase in heart rate of 52 beats and of temperature of 0.57°C, at 750 W of 74 beats/min and 0.84°C. During, as well as after, the exercise, heart rate and temperature have a parallel course. According to our data, control of physiological pacemakers by means of central venous blood temperature is possible.     

RECOVERY OF ARM FUNCTION DURING ACUTE TO CHRONIC STAGES OF STROKE QUANTIFIED BY KINEMATICS

ObjectiveTo quantify the longitudinal changes in upper limb kinematics within the first year after stroke and to identify the factors that are associated with these changes.MethodsA total of 66 individuals with stroke from the Stroke Arm Longitudinal Study at the University of Gothenburg (SALGOT) cohort were included if they were able to perform the target-to-target task. Data from a virtual reality haptic target-to-target task at 6 time-points between 3 days and 12 months after stroke were analysed by linear mixed models, while controlling for the impact of cofactors (stroke severity, age, type and side of stroke, sex and presence of diabetes).ResultsKinematic variables of movement time, mean velocity and number of velocity peaks improved over time and were positively associated with younger age, less severe stroke and ischaemic compared with haemorrhagic stroke. Most of the improvement occurred within 4 weeks after stroke, although movement time and number of velocity peaks also improved between 3 and 6 months after stroke.ConclusionKinematic variables of movement time, mean velocity and number of velocity peaks were effective in quantifying the longitudinal changes in upper limb kinematics within the first year after stroke.LAY ABSTRACTRecovery of arm function after stroke can be measured using virtual reality technology, which, in contrast to traditional clinical assessments, enables objective and highly precise measurement of different aspects of movement, such as speed and smoothness, termed kinematics. This study aimed to measure the recovery of arm movements between 3 days and 12 months after stroke using kinematic measures, and to identify factors that affect recovery. The results showed that movement time, mean velocity and smoothness improved with time after stroke. These data also suggest that younger stroke survivors, those with less severe stroke, and those with stroke caused by a clot, as opposed to a bleed, undergo greater improvements. Most of the improvement was seen early after stroke, within the first 4 weeks, but both movement time and smoothness also continued to improve between 3 and 6 months. The results show that kinematic analysis can effectively show the changes in arm movement within the first year after stroke.Key words: upper extremity, kinematics, outcome assessment, virtual reality, stroke recovery

Upper limb motor impairment occurs in approximately 50–80% of individuals in the acute stage of stroke (1–3) and continues in 40–50% in the chronic stage (2, 4). Approximately 65% of hospitalized individuals with initial motor deficits show some degree of motor recovery, while complete motor recovery occurs in less than 15% of individuals (5). Clinical recovery of upper limb motor function is most rapid during the first 4 weeks following stroke, and most recovery occurs during the first 3 months post-stroke (5, 6). Additional recovery has also been shown to occur after 3 months following stroke, usually in combination with intensive rehabilitation (5–7).The time course of functional recovery after stroke is dependent on several factors. There is a strong negative association of initial grade of stroke paresis and age with functional recovery after stroke (5, 8, 9). According to a retrospective observational study, individuals with haemorrhagic stroke had higher initial impairment compared with those with ischaemic stroke, as demonstrated by Fugl-Meyer Assessment of the Upper Extremity (FMA-UE) scores at admission (10). However, the haemorrhagic stroke group showed greater recovery in arm function and activity capacity, such that individuals in both groups had similar function at 3 months after stroke (11). It is not clear whether the same factors are reflected in the change in kinematic variables of arm function during the recovery of upper limb in individuals with stroke.Kinematic measurements of movement performance are recommended as core measures to be included in every stroke recovery trial (12). Kinematic assessment of upper limbs after stroke is often performed using optoelectronic cameras (13–15), robotic techniques (16) and virtual reality (VR) (17, 18). VR coupled with haptic devices can provide sensitive assessment of the kinematic function of the upper limb after stroke (19, 20). Haptic-enabled VR can measure end-point kinematics of common daily tasks, such as pointing, while allowing free arm movements in a 3D space (17). Despite VR systems being in use in stroke rehabilitation (21), there are sparse data from longitudinal studies, although some data on the responsiveness of upper limb kinematics are available from robotic studies (22–24). Haptic devices coupled with VR systems are suitable for use in the assessment and rehabilitation of post-stroke individuals, even in telemedicine settings (25).Longitudinal studies of upper limb recovery after stroke using optoelectronic cameras have shown that movement time and smoothness improved up to 3 months after stroke (14, 15, 26). Kinematic movement deficits observed at 3 months post-stroke remained unchanged at 12 months in individuals with mild stroke impairment (13). Thus, the recovery of kinematics seems to follow a similar recovery pattern as observed in clinical assessments, although the evidence in kinematics remains sparse and varies between studies. In addition, longitudinal changes in the kinematics of the upper limb after stroke have not been studied using the pointing task in 3D virtual space.The aims of this study were to quantify the longitudinal changes in upper limb kinematics between day 3 and month 12 after stroke, and to identify the factors that affect this change, using the target-to-target pointing task performed in VR.