Normalized pulse volume and blood volume as separate indices of finger arterial and venous vascular tone: Examination under propofol

Abstract: This study examined the newly proposed indices for estimating finger vascular tone, which can be obtained from near infrared transmittance photoplethysmographic recordings; normalized pulse volume (NPV) and blood volume (BV). They were recorded for seven male and two female students under continuous infusion of and recovery from propofol. Concomitant hemodynamic measurements were made with a non-invasive impedance cardiograph and a continuous blood pressure monitor. Normalized pulse volume showed no apparent dose-dependency and was negatively correlated with total peripheral resistance. In contrast, BV increased dose-dependently with propofol concentration and was negatively correlated with cardiac preload index (PLI) and with stroke volume (SV) at higher concentrations. The supplementary structural equation modeling procedure effectively illustrated causal relationships between BV, PLI and SV. In conclusion, the present data suggest that NPV and BV independently reflect arterial and venous tone in the finger tip, respectively. Although the underlying mechanisms remain unclear, BV is more sensitive to vascular dilation under propofol anesthesia.     

Perception and action in swimming: Effects of aquatic environment on upper limb inter-segmental coordination

This study assessed perception–action coupling in expert swimmers by focusing on their upper limb inter-segmental coordination in front crawl. To characterize this coupling, we manipulated the fluid flow and compared trials performed in a swimming pool and a swimming flume, both at a speed of 1.35 m s⁻¹. The temporal structure of the stroke cycle and the spatial coordination and its variability for both hand/lower arm and lower arm/upper arm couplings of the right body side were analyzed as a function of fluid flow using inertial sensors positioned on the corresponding segments. Swimmers’ perceptions in both environments were assessed using the Borg rating of perceived exertion scale. Results showed that manipulating the swimming environment impacts low-order (e.g., temporal, position, velocity or acceleration parameters) and high-order (i.e., spatial-temporal coordination) variables. The average stroke cycle duration and the relative duration of the catch and glide phases were reduced in the flume trial, which was perceived as very intense, whereas the pull and push phases were longer. Of the four coordination patterns (in-phase, anti-phase, proximal and distal: when the appropriate segment is leading the coordination of the other), flume swimming demonstrated more in-phase coordination for the catch and glide (between hand and lower arm) and recovery (hand/lower arm and lower arm/upper arm couplings). Conversely, the variability of the spatial coordination was not significantly different between the two environments, implying that expert swimmers maintain consistent and stable coordination despite constraints and whatever the swimming resistances. Investigations over a wider range of velocities are needed to better understand coordination dynamics when the aquatic environment is modified by a swimming flume. Since the design of flumes impacts significantly the hydrodynamics and turbulences of the fluid flow, previous results are mainly related to the characteristics of the flume used in the present study (or a similar one), and generalization is subject to additional investigations.     

支气管哮喘治疗重点的转移与“祛痰化瘀”的治则渊源

随着对支气管哮喘(哮喘)发病机制深入的研究,医学界将哮喘治疗的目标被定位于气道炎症的消除,但其治疗仍局限在气道局部炎症的控制,而对全身免疫功能紊乱束手无策。祖国医学讲究整体观念和治病求本,将气道炎症及与此相关的炎症介质和因子统归于痰瘀。气道炎症与痰瘀阻肺为不同医学体系对同一病症的诠释,二者殊途同归。祖国医学注重辩证施治、合理运用理法方药,疗效确实,副作用小,可以弥补糖皮质激素等药物的不足。     

Gender characteristics of cerebral hemodynamics during complex cognitive functioning

Functional Transcranial Doppler sonography (fTCD) has been applied to assess peak mean cerebral blood flow velocity (MFV) with a high temporal resolution during cognitive activation. Yet, little attention has been devoted to gender-related alterations of MFV, including spectral analysis. In healthy subjects, fTCD was used to investigate a series of cerebral hemodynamic parameters in the middle cerebral arteries (MCA) during the Trail Making Tests (TMT), a means of selective attention and complex cognitive functioning. In females, there was a frequency peak at 0.375 Hz in both MCA, and we observed a dynamic shift in hemispheric dominance during that condition. Further, after the start phase, there was an MFV decline during complex functioning for the entire sample. These novel results suggest condition-specific features of cerebral hemodynamics in females, and it adds to the notion that gender is a fundamental confounder of brain physiology.     

Balance of blood pressure equivalents as a new quantitative scale for identifying cardiac versus vascular reactor: Comparisons with Gregg, Matyas and James' (2002) hemodynamic profile scale

Abstract:  A quantitative scale for identifying cardiac versus vascular reactor, balance of blood pressure equivalents ( BE ), was newly advocated and compared with a very recently advocated one, hemodynamic profile ( HP ), by Gregg, Matyas and James (2002). BE was defined as " (Δ Q/Q ₀) P ₀'  − ( Δ R/R ₀ )P ₀." Here, P ₀ , Q ₀, and R ₀ were mean blood pressure ( P ), cardiac output ( Q ), and total peripheral resistance ( R ) during baseline, and Δ Q and Δ R were the difference scores of Q and R from baseline to stress, respectively. This was named as BE because the two terms in the formula indicated changes in Q and R in their blood pressure equivalents. Comparisons of the BE and HP scales were carried out, theoretically, in a newly introduced pressor space, on orthogonality with the extent of elevation of P (Δ P ); and then, practically, by using hypothetical data. In summary, it was shown that data points in the neighborhood in the pressor space can be judged as having not so different hemodynamic balance whether the BE or HP scale was used. As a merit, the BE scale seemed helpful to an intuitive understanding of the hemodynamics during stress. As a demerit, it cannot maintain the quasi-orthogonal relationship with Δ P when Q or R changes profoundly in the face of stress.     

The effects of sub-threshold vibratory noise on visuomotor entrainment during human walking and standing in a virtual reality environment

Humans will naturally synchronize their posture to the motion of a visual surround, but it is unclear if this visuomotor entrainment can be attenuated with an increased sensitivity to somatosensory information. Sub-threshold vibratory noise applied to the Achilles tendons has proven to enhance ankle proprioception through the phenomenon of stochastic resonance. Our purpose was to compare visuomotor entrainment during walking and standing, and to understand how this entrainment might be attenuated by applying sub-threshold vibratory noise over the Achilles tendons. We induced visuomotor entrainment during standing and treadmill walking for ten subjects (24.5 ± 2.9 years) using a speed-matched virtual hallway with continuous mediolateral perturbations at three different frequencies. Vibrotactile motors over the Achilles tendons provided noise (0–400 Hz) with an amplitude set to 90% of each participant’s sensory threshold. Mediolateral sacrum, C7, and head motion was greatly amplified (4–8× on average) at the perturbation frequencies during walking, but was much less pronounced during standing. During walking, individuals with greater mediolateral head motion at the fastest perturbation frequency saw the greatest attenuation of that motion with applied noise. Similarly, during standing, individuals who exhibited greater postural sway (as measured by the center of pressure) also saw the greatest reductions in sway with sub-threshold noise applied in three of our summary metrics. Our results suggest that, at least for healthy young adults, sub-threshold vibratory noise over the Achilles tendons can slightly improve postural control during disruptive mediolateral visual perturbations, but the applied noise does not substantially attenuate visuomotor entrainment during walking or standing.     

虚拟场景中的信息类型对路径整合效率的影响

空间巡航中常采用路径整合进行位置追踪及方向更新,本研究利用返回起点任务,通过对虚拟场景中不同信息类型的设置,探讨地标、纹理、双线索（地标+纹理）及纯色条件下路径整合效率的差异。结果发现,除角度误差外,双线索条件下路径整合效率显著较高,其次是地标条件,纹理条件次之,纯色条件下表现最差。结果表明,不同信息类型下路径整合效率存在显著差异,且双视觉信息较单一视觉信息条件下的整合效率更优。     

Differential Effect of Two Mental Stress Tasks on Arterial Stiffness

Acute mental stress is believed to induce transient arterial dysfunction, but relatively few data are available. We therefore examined the effect of mental stress tasks that could induce differential hemodynamic responses on arterial dysfunction. Forty‐eight participants conducted either a mental arithmetic (MA) task or a mirror‐tracing (MT) task. Cardiovascular indices and arterial stiffness were measured before, during, and after these tasks. Analysis revealed that increases in arterial stiffness during the task and during recovery were more pronounced for the MA than for the MT, and that evoked hemodynamic response was more myocardial for MA than for MT. These results clearly show that MA and MT tasks that induce differential hemodynamic responses have a differential effect on arterial stiffness. This finding sheds light on the underlying mechanism that may account for the relationship between cardiovascular reactivity and cardiovascular disease.     

Selling Yourself: Titmuss's Argument Against a Market in Blood

This article defends Richard Titmuss's argument, and PeterSinger's sympathetic support for it, against orthodoxphilosophical criticism. The article specifies thesense in which a market in blood is ``dehumanising' ashaving to do with a loss of ``imagined community' orsocial ``integration', and not with a loss of valued or``deeper' liberty. It separates two ``domino arguments'– the ``contamination of meaning' argument and the``erosion of motivation' argument which support, indifferent but interrelated ways, the claim that amarket in blood is ``imperialistic.' Concentrating onthe first domino argument the article considers theview that monetary and non-monetary meanings of thesame good can co-exist given the robustness of certainkinds of relationship and joint undertakings withinwhich gifts can figure. It argues that societalrelationships are vulnerable or permeable to theeffects of the market in a way that those constitutiveof the personal sphere are not.General, more broadly political questions remainunanswered but the core of Titmuss's original andchallenging argument remains and can be presented ina defensible form.     

The paradox of happiness: Why are we not doing what we know makes us happy?

Achieving and maintaining happiness can be difficult, especially when people are not engaging in the activities they know facilitate it. ‘Flow’ activities require clear rules, challenge, a high investment of energy, and have been shown to promote long-term happiness better than low investment, passive activities. Do people know this? In two studies, we found that, despite recognizing that flow activities are more likely to facilitate happiness, people nevertheless participated in passive leisure significantly more often in a typical week. Participants rated passive activities as being significantly more enjoyable, requiring less effort, and being less daunting to get started than flow activities. Participants’ engagement in flow activities was significantly predicted by how enjoyable the activities were perceived to be, whereas how daunting those activities were rated predicted non-engagement. Passive activity engagement was only significantly predicted by enjoyment. Suggestions for enabling people to rise above the barriers to flow activities are offered.