On the relation between cardiodynamics and heartbeat perception

The mediation of heartbeat perception by cardiodynamic parameters was investigated by experimentally introducing changes in heart performance. Twenty-five subjects (14 women 11 men) underwent bicycle ergometric exercises (0–75 W) at different tilt angles (90°-0°), After each of the 31 tilt/exercise phases, the following measures of cardiac performance were taken using impedance cardiography: stroke volume, Heather Index (as an indicator of contractile force), heart rate, and an estimate of the momentum of the ejected blood mass. Additionally, a heartbeat perception task was performed. The different tilt/exercise combinations induced profound changes in all cardiodynamic. measures, The correlation between heartbeat perception and cardiodynamic parameters was highest for “momentum”(r= 67) and for stroke volume (r= 59). From our data, we infer that intraindividually occurring changes in cardiac perception are mediated partially by characteristics of heart dynamics and that the source of these interoceptive signals lies in the heart or in its close vicinity.     

Oxygen Uptake to Work Rate Relation Throughout Peak Exercise in Normal Subjects: Relevance for Rate Adaptive Pacemaker Programming

The oxygen uptake to work rate (VO2/WR) relationship observed throughout peak exercise testing is already being applied for rate adaptive pacemaker programming. However, the detailed curve design of VO2/WR with respect to the anaerobic threshold (AT) has not yet been investigated. It was the purpose of this study to determine the VO2/WR slope below and above the AT in a healthy control group. Seventy-eight healthy control subjects (45.9 +/- 17.4 years; 34 women: 49.9 +/- 18.6 years 44 men: 43.6 +/- 16.6 years) were exercised on a treadmill with "breath-by-breath" gas exchange monitoring using the symptom limited "ramping incremental treadmill exercise" (RITE) protocol. The slope of the VO2/WR relationship from rest to peak exercise (r-p), rest to AT (slope A), and AT to peak exercise (slope B) in mL oxygen uptake per watt of external treadmill work was determined by linear regression analysis. [table: see text] The oxygen uptake to work rate relationship throughout peak exercise in the entire study group generated a significant slope change at the AT (31%, P < 0.0001) with a decreasing slope during higher work load intensities. Female subjects demonstrated a greater percentage of slope change at AT (43%), as compared to men (22%, P < 0.01). When using the oxygen uptake to work rate relationship for the programming of the pacemaker's rate response to exercise, the significant slope change at the AT should be considered to more appropriately pace during higher work intensities supported by anaerobic metabolism. Female pacemaker patients should be programmed to generate a steeper VO2/WR slope below AT with a greater slope change at AT, as compared to men. Abnormally high oxygen uptake to work rate ratios above the AT may be possibly used as an indicator of overpacing.     

Immunohistochemical identification of cells expressing ATP-gated cation channels (P2X receptors) in the adult rat thyroid

We carried out immunohistochemistry and western blotting of fresh frozen sections and crude extracts from adult rat thyroids. The histochemical and immunoblotting studies were performed with P2X receptor antibodies from 2 different sources. P2X-immunopositive cells were identified by fluorescence double labelling and confocal microscopy. Results of the western blotting experiments showed double bands of approximately 70 kDa and 140 kDa for all 7 P2X receptor subtypes with both sets of antibodies. Histochemical stains with antibodies from both sources also gave essentially identical results. P2X₁, P2X₂ and P2X₆ receptors were detected exclusively in vascular smooth muscle; P2X₅ and P2X₇ receptors were also present on vascular smooth muscle. Endothelial cells stained for P2X₃, P2X₄ and P2X₇ receptors. Thyroid follicular cells displayed immunoreactivity for P2X₃, P2X₄ and P2X₅ receptors. No immunostaining for P2X receptors was observed on C-cells. Possible roles for the broad expression of P2X receptor subtypes in the rat thyroid are discussed.     

Role of 'atypical pathogens' among adult hospitalized patients with community-acquired pneumonia

Background and objective: Agents such as Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophila are recognized as important causes of community‐acquired pneumonia (CAP) worldwide. This study examined the role of these ‘atypical pathogens’ (AP) among adult hospitalized patients with CAP. Methods: A prospective, observational study of consecutive adult CAP (clinico‐radiological diagnosis) patients hospitalized during 2004–2005 was conducted. Causal organisms were determined using cultures, antigen testing and paired serology. Clinical/laboratory/radiological variables and outcomes were compared between different aetiologies, and a clinical prediction rule for AP was constructed. Results: There were 1193 patients studied (mean age 70.8 ± 18.0 years, men 59.3%). Causal organisms were identified in 468 (39.2%) patients: ‘bacterial’ (48.7%), ‘viral’ (26.9%), ‘AP’ (28.6%). The AP infections comprised Mycoplasma or Chlamydophila pneumoniae (97.8%) and co‐infection with bacteria/virus (30.6%). The majority of AP infections involved elderly patients (63.4%) with comorbidities (41.8%), and more than one‐third of patients were classified as ‘intermediate’ or ‘high’ risk CAP on presentation (pneumonia severity index IV–V (35.1%); CURB‐65 2–5 (42.5%)). Patients with AP infections had disease severities and outcomes similar to patients with CAP due to other organisms (oxygen therapy 29.1% vs 29.8%; non‐invasive ventilation 3.7% vs 3.3%; admission to the intensive care unit 4.5% vs 2.7%; length of hospitalization 6 day vs 7 day; 30‐day mortality: 2.2% vs 6.0%; overall P > 0.05). Age <65 years, female gender, fever ≥38.0°C, respiratory rate <25/min, pulse rate <100/min, serum sodium >130 mmol/L, leucocyte count <11 × 10⁹/L and Hb < 11 g/dL were features associated with AP infection, but the derived prediction rule failed to reliably discriminate CAP caused by AP from bacterial CAP (area under the curve 0.75). Conclusions: M. pneumoniae and C. pneumoniae as single/co‐pathogens are important causes of severe pneumonia among older adults. No reliable clinical indicators exist, so empirical antibiotic coverage for hospitalized CAP patients may need to be considered.     

The effect of respiratory and metabolic acid-base changes on ionized calcium concentration: in vivo and in vitro experiments in man and rat

Abstract. Correlation of ionized calcium concentration, [Ca²⁺] and blood pH has long been recognized. So far no distinction of the acid-base changes, i.e. respiratory changes or metabolic changes seemed necessary. The present study, with the use of a recently developed system for in vivo analysis of [Ca²⁺], and with in vitro experiments reinvestigates this question.
In a first series respiratory and metabolic changes were induced in rats. Changes of [Ca²⁺] (Δ[Ca²⁺]) and of plasma pH (ΔpH) were recorded continuously in vivo , plasma bicarbonate, [HCO^-₃] was measured in vitro . In a second series respiratory and metabolic changes were induced in sixteen volunteers and, separately, in vitro in plasma and modified Ringer solution, and the same parameters were determined.
In all experiments Δ[Ca²⁺] correlates negatively with ΔpH. However, the correlation in respiratory changes was significantly less as compared to that in metabolic changes. As expected, Δ[HCO^-₃] correlates positively with pH in metabolic and negatively in respiratory changes. We conclude from these experiments that in metabolic changes the effects of calciumalbumin interaction and calcium complexation with bicarbonate are additive, whereas both effects oppose each other in respiratory changes. This might explain the blunted effect of pH changes on [Ca²⁺] in respiratory changes.     

医院投资中不断增长的挑战

全世界医保供应者都在面临着一系列的挑战,比如有限的资金来源、人口的变化、技术和医术的进步、透明度的上升和病人要求的增多,这些都会给医保市场带来很大压力。政府扶持的减少使这一状况变得更为严重。但是,提高经济实力、争取足够投资是未来医院成功的关键。因此,医院必须对新的资本分配方式进行评估。本文论述了使医疗设备适应投资需要和增强医院市场竞争力的五种选择。     

Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms

YANG, A., et al .: Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms. Pacing algorithms to prevent PAF are mainly based on the suppression of premature atrial complexes (PACs), which play an important role in its initiation. In contrast to 24-hour ambulatory electrocardiograms, advanced pacemaker (PM) diagnostic features are capable of recording AF episodes during long follow-up periods and of characterizing AF in a detailed fashion. For the specific use of these algorithms, a detailed characterization of AF was performed in 91 dual chamber PM recipients with histories of AF. Fifteen patients with episodes of oversensing due to far-field signals or frequent episodes of "2:1-undersensing" of atrial flutter were excluded. The remaining 76 patients had high recurrence rates of AF (median 0.8 episodes/day), however, the majority of episodes lasted <7 minutes. Despite frequent PACs (median 10.8/hour) during sinus rhythm, a median of 66.4% of the AF episodes were preceded by <2 PACs/min before onset. In conclusion, frequent, short-lived AF episodes seem best suited for AF preventive pacing therapies. However, the small number of PACs preceding many AF episodes may limit the efficacy of PAC suppressing algorithms. (PACE 2003; 26[Pt. II]:310–313)