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PubMed2002

The relationship of the heart rate deflection point to the ventilatory threshold in trained cyclists.

The purpose of this study was to assess the relationship of the heart rate deflection point (HRDP) to the ventilatory threshold (VT) in trained cyclists. Twenty-one endurance-trained cyclists (mean +/- SD: Vo(2)max = 67.6 +/- 4.7 ml x kg x min(-1)) completed a maximal cycle ergometer test of volitional fatigue using a ramped protocol. Ventilatory variables (Ve, Vo(2), Vco(2)) and power were measured online with averages reported every 20 seconds. Heart rate (HR) was recorded every 20 seconds using a Polar monitor. VT was calculated using the excess CO(2) elimination curve. The first derivative of a logistic growth curve fit to the HR-power data produced the HRDP. No significant differences (p > 0.01) existed between HR values at HRDP (171.7 +/- 9.6 b x min(-1)) and VT (169.8 +/- 9.9 b x min(-1)) or between Vo(2) values at HRDP (53.6 +/- 4.2 ml x kg x min(-1)) and VT (52.2 +/- 4.8 ml x kg x min(-1)). But power values at HRDP (318.7 +/- 30.7 W) were significantly different (p < 0.01) from those at VT (334.8 +/- 36.7 W). There were significant relationships between HRDP and VT for the physiological variables of HR (r = 0.92, p < 0.001), Vo(2) (r = 0.72, p < 0.001), and power (r = 0.77, p < 0.001). These findings indicate that HR and Vo(2) at HRDP are not significantly different from the values at VT in trained cyclists. HR values derived from HRDP may be used to set parameters for training intensity. Variability in the speed/power-HRDP relationship across detrained/trained states may be used to evaluate training programs.

Adult↗

PubMed2004

Training-induced changes in aerobic aptitudes of professional basketball players.

We investigated the effects of a training program on the aerobic aptitudes and the relevance of the instant of equality of pulmonary gas exchange (i. e., RER = 1.00) to assess these effects in professional basketball players. Eight athletes performed two incremental exercise tests on a cycloergometer separated by 4.7 +/- 0.7 months. Physiological variables recorded during these two tests (heart rate, oxygen uptake, carbon dioxide output, respiratory exchange ratio, power output) allowed to determine the first and second ventilatory thresholds and the instant of equality of pulmonary gas exchange. The training program induced significant variations of resting heart rate, oxygen uptake and power output measured for the instant of equality of pulmonary gas exchange. Moreover, the used fractions of heart rate, oxygen uptake and power reserves for the instant of equality of pulmonary gas exchange and the second ventilatory threshold increase significantly. Inversely, maximal oxygen uptake, maximal power reached and the used fractions of reserves for the first ventilatory threshold do not differ significantly. Professional basketball training is not focused on drills aiming to enhance both the aerobic power and aptitude, our results suggest that this training program induce the same physiological changes as a typical aerobic training. We also demonstrated that the instant of equality of pulmonary gas exchange is a powerful tool to quantify the changes in aerobic aptitudes during a sport season.

Adult↗

PubMed2005

Prediction of outcomes in trauma: anatomic or physiologic parameters?

BACKGROUND: Prediction of outcomes after injury has traditionally incorporated measures of injury severity, but recent studies suggest that including physiologic and shock measures can improve accuracy of anatomic-based models. A recent single-institution study described a mortality predictive equation [f(x) = 3.48 - .22 (GCS) - .08 (BE) + .08 (Tx) + .05 (ISS) + .04 (Age)], where GSC is Glasgow Coma Score, BE is base excess, Tx is transfusion requirement, and ISS is Injury Severity Score, which had 63% sensitivity, 94% specificity, (receiver operating characteristic [ROC] 0.96), but did not provide comparative data for other models. We have previously documented that the Physiologic Trauma Score, including only physiologic variables (systemic inflammatory response syndrome, Glasgow Coma Score, age) also accurately predicts mortality in trauma. The objective of this study was to compare the predictive abilities of these statistical models in trauma outcomes. METHODS: Area under the ROC curve of sensitivity versus 1-specificity was used to assess predictive ability and measured discrimination of the models. RESULTS: The study cohort consisted of 15,534 trauma patients (80% blunt mechanism) admitted to a Level I trauma center over a 3-year period (mean age 37 +/- 18 years; mean Injury Severity Score 10 +/- 10; mortality 4%). Sensitivity of the new predictive model was 45%, specificity was 96%, ROC was 0.91, validating this new trauma outcomes model in our institution. This was comparable with area under the ROC for Revised Trauma Score (ROC 0.88), Trauma and Injury Severity Score (ROC 0.97), and Physiologic Trauma Score (ROC 0.95), but superior compared with admission Glasgow Coma Score (ROC 0.79), Injury Severity Score (ROC 0.79), and age (ROC 0.60). CONCLUSIONS: The predictive ability of this new model is superior to anatomic-based models such as Injury Severity Score, but comparable with other physiologic-based models such as Revised Trauma Score, Physiologic Trauma Score and Trauma, and Injury Severity Score.

Adult↗

PubMed1998

Autonomic balance revisited: panic anxiety and heart rate variability.

The analysis of heart rate variability (HRV) is becoming widely used in clinical research to provide a window into autonomic control of HR. This technique has been valuable in elucidating the autonomic underpinnings of panic disorder (PD), a condition that is marked by reports of heart palpitations. A body of research has emerged that implicates a relative reduction in HRV and cardiac vagal tone in PD, as indicated by various HRV measures. These data are consistent with the cardiac symptoms of panic attacks, as well as with developmental evidence that links high vagal tone with enhanced attention, effective emotion regulation, and organismic responsivity. Implications of these findings for nosology and pathophysiology are discussed. Reports of reduced HRV in PD contrast with portrayals of excess autonomic lability in anxiety. This contradiction is addressed in the context of traditional homeostatic models versus a systems perspective that views physiologic variability as essential to overall stability.

Anxiety Disorders↗

PubMed2002

Amphetamine effects on prepulse inhibition across-species: replication and parametric extension.

Despite the similarities of prepulse inhibition (PPI) of the startle reflex and its apparent neural regulation in rodents and humans, it has been difficult to demonstrate cross-species homology in the sensitivity of PPI to pharmacologic challenges. PPI is disrupted in rats by the indirect dopamine (DA) agonist amphetamine, and while studies in humans have suggested similar effects of amphetamine, these effects have been limited to populations characterized by smoking status and specific personality features. In the context of a study assessing the time course of several DA agonist effects on physiological variables, we failed to detect PPI-disruptive effects of amphetamine in a small group of normal males. The present study was designed to reexamine this issue, using a larger sample and a paradigm that should be more sensitive for detecting drug effects. PPI in rats was shown to be disrupted by the highest dose of amphetamine (3.0 mg/kg) at relatively longer prepulse intervals (>30 ms). In humans, between-subject comparisons of placebo (n=15) vs 20 mg amphetamine (n=15) failed to detect significant PPI-disruptive effects of amphetamine, but significant PPI-disruptive effects at short (10-20 ms) prepulse intervals were detected using within-subject analyses of postdrug PPI levels relative to each subject's baseline PPI. Post hoc comparisons failed to detect greater sensitivity to amphetamine among subjects characterized by different personality and physiological traits. Bioactivity of amphetamine was verified by autonomic and subjective changes. These results provide modest support for cross-species homology in the PPI-disruptive effects of amphetamine, but suggest that these effects in humans at the present dose are subtle and may be best detected using within-subject designs and specific stimulus characteristics.

Acoustic Stimulation↗

PubMed1982

Variations in diurnal and nocturnal waking state in air traffic controllers.

Physiological variables of 22 air traffic controllers (ATCs), mean age 32, were continuously telemetrically recorded from 08:00 to 17:30 and on the following day from 19:00 to either 00:00 or 0.3:00. EEG (alpha and theta indices, slow delta waves), EOG (palpebral blinks), EMG (from the neck muscles) and EKG (HR) were recorded. Comparison between day and night shows an increase at night of HR and slow waves, particularly after midnight. These results were compared with similar ones obtained from two other populations of the same age having very different professional activities (university personnel and factory workers). The EEG indices and HR are higher in ATCs. The work load imposed by the need in air traffic control to maintain a high level of vigilance, especially difficult after midnight, is in great part responsible for the high values of physiological parameters observed in this study.

Adult↗

PubMed1993

[Neurolytic block of the lumbar sympathetic trunk in advanced stages of peripheral arterial occlusive disease].

UNLABELLED: Neurolytic blocks of the lumbar sympathetic trunk enable a less invasive sympathetic denervation if compared to standard surgical procedures. METHODS: 34 patients undergoing chemical lumbar sympathectomy (CLS) for advanced arterial occlusive disease were prospectively studied. An actual indication for reconstructive vascular surgical intervention had been excluded in all patients. The sympatholytic efficacy, different haemodynamic variables, the relief of rest pain and the effect on ischaemic ulcers were quantified before, 3 and 21 days after CLS. RESULTS: The mean intensity of rest pain, as assessed on a visual analogue scale (0-100 mm), significantly decreased from 60 mm to 31 and 34 mm, respectively. 9 of 12 patients with ischaemic ulcers showed partial or complete remission within the study period. Overall, in 88% of patients sympathetic denervation could be demonstrated by ablation of the sympatho-galvanic skin response. The mean difference in skin temperature between the treated and the untreated leg significantly increased from -0.73 degrees C to +0.34 and +0.39 degrees C, respectively. Doppler-sonographic measurements of the ankle-pressure-index showed a minor increase from 0.34 to 0.36 and 0.42; however, these changes did not reach significance. Neither changes of the different physiologic variables nor data of the patient history could predict the relief of rest pain after CLS. The only side effect of CLS was transient neuralgia of the genitofemoral nerve occurring in 19% of patients. CONCLUSION: Considering the relatively short follow-up period, the results of this study support evidence of the therapeutic efficacy of CLS for rest pain and ischaemic ulcers in patients with advanced arterial disease. The prognostic value of standard variables for estimation of sympathetic reactivity and skin blood flow, however, could not be confirmed.

Aged↗

PubMed1992

Continuous central venous oximetry and shock index in the emergency department: use in the evaluation of clinical shock.

Initial therapy of shock in the emergency department (ED) emphasizes the normalization of physiologic variables such as heart rate (HR), mean arterial pressure (MAP), and central venous pressure (CVP) rather than restoration of adequate tissue oxygenation. After hemodynamic stabilization of MAP, CVP, and HR, the authors examined tissue oxygenation as indicated by continuous central venous oximetry (SCVO2), lactic acid concentration, and shock index (SI). Sixteen consecutive nonrandomized patients presenting to the ED of a large urban hospital in shock (MAP < 60 mm Hg, HR > 120 beats/min, and altered sensorium) were initially resuscitated with fluid, blood, inotropes, and/or vasoactive drug therapy to normalize MAP, CVP, and HR. In addition, SCVO2, arterial lactate concentration, and SI were measured after completion of resuscitation in the ED. Eight patients (group no. 1) had inadequate tissue oxygenation reflected by low SCVO2 (less than 65%). Four patients in group no. 1 had elevated arterial lactic acid concentration. All group no. 1 patients had an elevated SI (> 0.7) suggesting persistent impairment of left ventricular stroke work. Eight patients (group no. 2) had normal or elevated SCVO2 (> 65%). In group no. 2, arterial lactic acid concentration was elevated in six and SI in seven patients. Normalization of hemodynamic variables does not adequately reflect the optimal endpoint of initial therapy in shock in the ED. Most (94%) of these patients continue to have significant global ischemia and cardiac dysfunction as indicated by reduced SCVO2 and elevated lactic acid concentration and SI. Systemic tissue oxygenation should be monitored and optimized in the ED in these critically ill patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

CoQ10 fails to protect brain against focal and global ischemia in rats.

OBJECTIVE: Release of oxygen free radicals occurs following cerebral ischemia. Studies show that oxygen free radicals mediate ischemic brain injury. CoQ10 is a potent free radical scavenger and may offset brain injury associated with reperfusion. We tested exogeneous CoQ10 as a neuroprotectant in rats following both global and focal ischemic insults. METHODS: Rats were subjected to either 4-vessel occlusion ischemia (4-VO, 10 min occlusion, 7-day survival) or middle cerebral artery occlusion (MCAO, 120 min-occlusion, 22.5 h survival). Regional cerebral blood flows (rCBF) and physiological variables such as blood pressure, pO2, pCO2, plasma glucose and hematocrit were monitored and measured in focal ischemia. The animals were randomized to receive treatments of either phosphate buffered saline (PBS) vehicle or CoQ10 following global or focal ischemia. Injection times were at the end of ischemia and 3 h later for both models of ischemia. Histological outcomes are expressed as a percentage of hippocampal CA(1) cell injury in global ischemia or percentage of cortical infarct over that of non-ischemic hemisphere in focal ischemia. RESULTS: In global ischemia, animals treated with PBS vehicle and CoQ10 had 86+/-5% (n=8) and 83+/-10% (n=8), respectively, of hippocampal CA(1) cell injury (P>0.05). The percentage of infarct volumes in animals following focal ischemia were 23+/-9% (control, n=10) and 25+/-9% (CoQ10, n=10). There were no temperature or physiological differences between the two treatment groups. CONCLUSION: Acute treatment with CoQ10 via intraperitoneal injection does not prevent neuronal injuries following global and focal ischemia.

Animals↗

PubMed1989

Heat stress in protective clothing. Interactions among physical and physiological factors.

Data from experiments on animals and humans have supported the development of computer models that predict human response to various combinations of the three main heat stress factors work, clothing, and environment. However, recent application of such models shows that the validity of their output is limited in part by the need to represent more faithfully the interactions among the primary heat stress factors and certain physiological variables. Examples of such interactions include the weight and stiffness of protective outfits increasing the metabolic cost of a task, profuse sweating that wets clothing and alters its heat transfer characteristics, task-related movements altering air exchange rates through clothing, individual aerobic capacity affecting thermoregulatory response to a given metabolic load, and sweat retention in clothing raising skin wettedness and possibly inducing sweat suppression. This paper reviews recent research in these areas and identifies certain areas where further data are needed.

Adaptation, Biological↗

PubMed1979

Adaptive changes in cerebral blood flow and oxygen consumption during ethanol intoxication in the rat..

Cerebral blood flow (CBF) and oxygen consumption (CMRO2) were measured during acute and long-term ethanol intoxication in the rat. The purpose was to investigate whether the adaptive changes (development of tolerance) occurring in the CNS during ethanol intoxication were associated with changes in CBF and/or CMRO2. Consistent with other studies we found that acute severe ethanol intoxication (median blood alcohol concentration (BAC = 5.4 mg/ml)) caused a significant decrease in CBF and CMRO2. After 3-4 days of severe intoxication (BAC of 6.6 mg/ml) these physiological variables were less affected indicating that functional tolerance had developed: CMRO2 and CBF during acute ethanol intoxication were 9.3 ml/100 g/min and 60 ml/100 g/min respectively; after the long term intoxication period these variables reached 11.2 ml/100 g/min and 78 ml/100 g/min respectively, i.e. values not significantly lower than those of the control group. After induction of hypercapnia (PaCO2 about 80 mmHg) CBF increased by 360% in the control group; in the acutely intoxicated group CBF increased by only 127% and in the long term intoxicated group by 203% indicating that the cerebrovascular CO2-reactivity had also adapted to the ethanol intoxication. It is concluded that adaptive changes of the CNS to chronic ethanol intoxication comprise alterations in CMRO2, CBF and cerebrovascular reactivity.

Adaptation, Physiological↗

PubMed1982

Biotelemetry, based on optical transmission.

Biotelemetry has developed as a reliable alternative to continuous monitoring of physiological variables under realistic circumstances of data assessment. For incorporation in clinical routine the lack of an adequate number of biotelemetry frequencies forms a severe disadvantage. This paper shows a way to circumvent the problem, namely by using infrared light as the carrier for the transmission system. Use of infrared light is limited to indoor applications, and a number of additional restrictions have to be accepted, but on the other hand infrared telemetry opens new possibilities not known to radiotelemetry, especially suited for clinical applications.

Biomedical Engineering↗

PubMed2006

If current inhibition: cellular basis and physiology.

The slow diastolic depolarization phase in cardiac pacemaker cells is the electrical basis of cardiac automaticity. The hyperpolarization-activated current (I(f)) is one of the key mechanisms underlying diastolic depolarization. Particularly, I(f) is unique in being activated on membrane hyperpolarization following the repolarization phase of the action potential. I(f) has adapted biophysical properties and voltage-dependent gating to initiate pacemaker activity. I(f) possibly constitutes the first voltage-dependent trigger of the diastolic depolarization. For these reasons, I(f) is a natural pharmacological target for controlling heart rate in cardiovascular disease. In this view, I(f) inhibitors have been developed in the past, yet the only molecule to have reached the clinical development is ivabradine. At the cellular level, the remarkable success of ivabradine is to be ascribed to its relatively high affinity for f-channels. Furthermore, ivabradine is the most I(f)-specific inhibitor known to date, since moderate inhibition of other voltage-dependent ionic currents involved in automaticity can be observed only at very high concentrations of ivabradine, more than one order of magnitude from that inhibiting I(f). Finally, the mechanism of block of f-channels by ivabradine has particularly favorable properties in light of controlling heart rate under variable physiological conditions. In this article, we will discuss how I(f) inhibition by ivabradine can lead to reduction of heart rate. To this aim, we will comment on the role of I(f) in cardiac automaticity and on the mechanism of action of ivabradine on f-channels. Some aspects of the cardiac pacemaker mechanism that improve the degree of security of ivabradine will also be highlighted.

Animals↗

PubMed2000

[Temporal inconsistency of neuromyography of the facial nerve in healthy probands].

Facial neuromyography is an objective electrophysiologic measurement used to assess prognosis for recovery from facial paralysis. In the present study variability over time of the amplitude ratio in healthy subjects was investigated. Twenty healthy subjects underwent four neuromyographic tests at intervals of one week. The study group consisted of 12 males and 8 females. Ages ranged from 23 to 36 years. The stimulation intensity required for supramaximal stimulation was 14.6 mA on average. The mean of the intra-individual side-to-side difference of the evoked compound action potential was 32.5%. Results of the four repeated tests ranged from no to 80% side-to-side differences in the same individual. The hypothesis of symmetrical evoked facial compound potentials was not supported by our data. As with previous investigators we found significant side-to-side differences in healthy subjects. Furthermore, we could also show for the first time that the amplitude ratio was not constant in every individual at repeated measurements. We conclude that there is a physiological variability that must be taken into account in the interpretation of facial nerve neuromyography.

Adult↗

PubMed1994

A four-parameter linear model for analysing cardiorespiratory data in post-operative cardiac patients.

This paper investigates the possibility of characterizing the differences between normal- and high-risk postoperative cardiac patients on the basis of four parameters related to a simple linear model of cardiorespiratory performances. The model comprises three subsystems representing cardiac, vascular and respiratory functions, respectively. These parameters, determined from physiological variables measured in the Intensive Care Unit, seem useful for clinical evaluation of patient status. In fact, their values quantify the improved cardiovascular and respiratory response that normal-risk patients exhibit to increasing metabolic needs after hypothermic treatment, with less utilization of blood oxygen reserve. In addition, a set of three parameters derived from the proposed four allows a prediction of patient class membership with an error lower than 7% when used with a Bayes quadratic classifier.

Cardiac Surgical Procedures↗

PubMed1983

Peripheral postcapillary venous pressure: a new, more sensitive monitor of effective blood volume during hemorrhagic shock and resuscitation.

Peripheral postcapillary venous pressure (PCVP) and mixed venous oxygen saturation (SvO2 or PASO2) have been shown to be sensitive indicators of volume status and appear to reflect the adequacy of peripheral perfusion during controlled bleeding. This study demonstrates that in an open-chest dog model with controlled venous return, PCVP is closely and linearly (r2 = 0.6) correlated with cardiac output (CO). Furthermore, oxygen saturation as measured in the central venous system (CVSO2) and peripheral vein PVSO2) were found to be closely and linearly related to PASO2 (r = 0.72 to 0.99 and 0.91 to 0.98, respectively). Thus PCVP, CVSO2, and PVSO2 represent easily and safely obtainable parameters that closely reflect major physiologic variables. During resuscitation after controlled hemorrhage, the PCVP and PVSO2 accurately reflected the restoration of blood volume and were as good as CO and central saturations. Central venous and pulmonary wedge pressures both poorly reflected the return to full volume repletion (P less than 0.01). Thus, PCVP and PVSO2 seem to be reliable indices of volume status and perfusion and do not require invasive, central monitoring.

Animals↗

PubMed1998

Psychosocial work environment and cardiovascular risk factors in an occupational cohort in France.

STUDY OBJECTIVE: Concordant results have been reported in several studies for the effects of job stress on cardiovascular disease, but the potential mechanisms of these effects have seldom been explored. The aim of this study was therefore to examine, in women and men, the cross sectional relations between psychosocial work variables (psychological demands, decision latitude, and social support) and cardiovascular risk factors (hypertension, hyperlipidaemia, diabetes, overweight, smoking, and alcohol consumption). PARTICIPANTS: The original cohort comprised 20,625 volunteers (men aged from 40 to 50 and women from 35 to 50) employed by the French Company Electricité De France-Gaz De France and followed up yearly since 1989. The study was restricted to the 13,226 volunteers in the cohort who were still working and answered a self administered questionnaire on psychosocial work factors in 1995. DESIGN: Data were based on replies to this questionnaire. Three psychosocial work environment exposure scores were used to assess psychological demands, decision latitude, and social support at work respectively. The main outcome measures were the prevalence of hypertension, hyperlipidaemia, and diabetes within the previous 12 months, overweight, smoking, and alcohol consumption. MAIN RESULTS: Psychosocial work factors were significantly associated with hypertension, hyperlipidaemia, overweight, smoking, and alcohol consumption, but not with diabetes. In men, low decision latitude was associated with hypertension, high decision latitude and high social support with overweight, low decision latitude with alcohol consumption. Moreover, the risk of hyperlipidaemia increased in men exposed to both high psychological demands and low social support. In women, low decision latitude was related to hyperlipidaemia, high psychological demands with overweight, high psychological demands and high decision latitude with smoking, and low social support with alcohol consumption. CONCLUSIONS: These cross sectional results underline the potential effects of psychosocial work characteristics on cardiovascular risk factors and the differences between the effects of job stress in men and women, and confirm the direct mechanisms (through physiological variables) and indirect mechanisms (through behavioural risk factors) potentially involved in the relation between psychosocial work characteristics and cardiovascular disease.

Adult↗

PubMed1999

Pharmacokinetics and pharmacologic effects of the S(-) isomer of bupivacaine after intravenous and epidural administration in dogs.

OBJECTIVE: To determine pharmacokinetic variables and pharmacologic effects of the S(-) isomer of bupivacaine (S[-]-BPV) in dogs. ANIMALS: 6 adult male Beagles. PROCEDURE: Dogs received S(-)-BPV (1 mg/kg of body weight) i.v., and 15 days later, the same dogs received 1.8 mg/kg epidurally. Pharmacokinetic variables and pharmacologic effects were determined for each route of administration. RESULTS: After i.v. administration, plasma concentration versus time curves were adjusted, using biexponential equations that indicated a rapid distribution phase followed by a slower elimination phase, with a mean +/- SD half-life of 33.5 +/- 17.0 minutes. Mean plasma clearance was 21.0 +/- 10.7 ml/min/kg, and mean volume of distribution at steady state was 0.8 +/- 0.2 L/kg. After i.v. administration, mean peak plasma concentration was 2.6 +/- 0.7 micrograms/ml; after epidural administration, it was 0.9 +/- 0.5 microgram/ml at approximately 3 minutes. Half-life after epidural administration was 5 times longer than that observed after i.v. administration. Motor block began immediately after the end of epidural administration and lasted for 3 to 4 hours. Changes in systolic blood pressure and heart rate after epidural administration were slight but occurred at the same time that plasma concentration peaked. After i.v. administration, motor block or variations in physiologic variables studied were not observed. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, the pharmacologic behavior of S(-)-BPV was similar to that of the bupivacaine racemate, but motor block attributable to S(-)-BPV lasted longer than that attributable to the racemate, with lower plasma concentrations observed at equivalent sample collection times.

Anesthetics, Local↗