Patterns and stability of cardiovascular responses to variations of the cold pressor test

Test-retest reliabilities and patterns of heart rate and blood pressure responses were examined using variations in the cold pressor test in 113 normotensive white college men. Comparisons were made of stimulus site (forehead vs. foot) and bodily posture (seated vs. supine) across four separate groups of men. The stability of cardiovascular responses was examined over a 2-week test-retest interval. Different cardiovascular response patterns emerged as a function of stimulation site and posture. Systolic and diastolic blood pressure increases were accompanied by bradycardia in the forehead cold pressor task but by tachycardia in the foot cold pressor task. Systolic blood pressure increases were larger for foot than for forehead stimulation. Heart rate increases were larger for supine than for seated men. Effects on response were independent of postural differences at baseline, and there were no stimulation site by posture interactions. The cardiovascular responses to stimulation did not attenuate across sessions in any experimental condition but were more reliable for foot than for forehead stimulation and for supine than for seated posture. Short-term stability for changes to the task approached that for baseline and task and was higher than has been reported elsewhere.     

Stimulus dimensions of the cold pressor test and the associated patterns of cardiovascular response

Hemodynamics of the cold pressor response in relation to its pain and nonpain stimulus components were investigated in normotensive college men using the foot and forehead cold pressor tasks. Mechanisms of pain- and non-pain-related increases in blood pressure were analyzed as residual effects of concurrent changes in total peripheral resistance and cardiac output. The identified partial relationships suggested that the response pattern associated with pain included positive change both in cardiac output and in total peripheral resistance, whereas the nonpain-related response was limited to an increase in total peripheral resistance. Analyses of individual differences in car-diovascular responses to pain further indicated that pain-related increments in blood pressure were mediated by a steeper rise in total peripheral resistance, an increase in heart rate, and an apparent increase in preload. At baseline, high reactors to pain manifested relatively elevated total perpheral resistance, diminished cardiac output, and an indication of a reduced inotropic state, suggesting that altered basal homeostasis may discriminate normotensive individuals displaying heightened cardiovascular reactivity to aversive cold stimulation.     

Cardiovascular changes during an isometric contraction combined to a cold pressor test

Fifteen normotensive male subjects (age, 27.9±1.3 years) performed isometric contractions (handgrip) at 15, 30 and 50% maximal voluntary contraction respectively for 7, 3 and 1 min. The contractions were sustained with or without a cold pressor test of the same duration (immersion of one foot in water of 5.2 ± 0.1^oC). At rest, under the influence of a cold pressor test for 3 min, the heart rate increased from 74.3 ± 2.2 to 83.3 ±2.1 beats min-1 (P < 0.001) in less than 10 s, and returned to the control value in 3 min; on the contrary, at the end of 3 min of cold pressor test, the systolic blood pressure was still above the control value (135.5 ± 4.2 and 121.0 ± 3.2 mmHg, P < 0.001). During the contractions, there was no significant difference between heart rate and systolic blood pressure values obtained with or without cold pressor test. Similarly, there was no significant change in the concentrations of plasma catecholamines. This absence of cardiovascular effect of cold pressor test associated with isometric contraction (for three relative force levels) is probably due to the increasing importance of sympathetic cardiac activation produced by the contraction with respect to that produced by the cold pressor test, the absence of supplementary changes in total peripheral resistance and a partial reciprocal inhibition of pain produced by the simultaneous performance of these two tests.     

Blood pressure and muscle sympathetic nerve activity during cold pressor stress: fitness and gender

We examined putative autonomic and hemodynamic mechanisms that might explain our prior finding that cardiorespiratory fitness mitigates blood pressure responses by normotensive women during the hand cold pressor test. We report that fitness level was inversely related to increases in systolic and diastolic blood pressures and muscle sympathetic nerve activity (MSNA) during the cold pressor among women but not men. The pattern of responses among fitter women was consistent with decreased central sympathetic outflow resulting in reduced stroke volume or dampened peripheral resistance in vascular beds other than calf skeletal muscle. Fitter men and women had slightly larger increases in blood pressure during mental arithmetic, but otherwise fitness was not directly related to stress responses. The results further encourage consideration of cardiorespiratory fitness as a modifying covariate when the hand cold pressor test is used as a predictor of future hypertension among women.     

Sympathetic activation during the cold pressor test: influence of stimulus area

The purpose of this study was to determine the effect of the size of the stimulus area on the muscle sympathetic nerve activity (MSNA), systolic arterial blood pressure (SAP), and heart rate responses to the cold pressor test. To accomplish this, these variables were measured before (control), during, and after 1.5 min of ice water immersion of either one or both hands in nine healthy subjects (aged 19-27 years). The cold stimulus elicited significant increases above control levels in all three variables under both conditions (P less than 0.05). Immersion of both hands produced a much greater increase in total MSNA (+366%) than immersion of a single hand (+187%) (P less than 0.05). However, the magnitudes of the increases in SAP and heart rate during two-hand immersion (29 +/- 6 mmHg and 10 +/- 2 beats min-1) were not significantly different from the responses during the one-hand trials (24 +/- 5 mmHg and 6 +/- 2 beats min-1, P greater than 0.05). There was a strong, direct relationship between total MSNA and SAP responses during one-hand immersion (r = 0.93, P less than 0.001) but not during immersion of both hands (r = 0.66, P = 0.08). These findings indicate that during the cold pressor test the magnitude of the increase in sympathetic discharge to skeletal muscle, but not the systolic blood pressure response, is influenced by the size of the tissue area exposed to the stimulus.     

A comparison of cardiovascular and autonomic adjustments to three types of cold stimulation tasks.

Two types of 'cold pressor' tasks are used frequently in research settings: immersing the hand or foot in ice water, and applying an icebag to the forehead. Both tasks have commonly been selected as 'alpha-adrenergic' tasks due to expected increases in blood pressure and peripheral resistance. However, the forehead cooling task has been used by others to produce increased vagal tone due to the elicitation of the 'diving reflex' and subsequent bradycardia. This differs from the prototypical increase in heart rate during hand immersion. The present study directly compared the cardiovascular adjustments of hand immersion and forehead stimulation. As stimulation of the trigeminal nerve is thought to increase vagal activity during forehead cooling, a third condition in which most of the face was covered with an icebag was included to ostensibly stimulate more of the trigeminal. 18 males had counterbalanced exposures to hand immersion, forehead cooling, and facial cooling for 90 s each. Cardiovascular variables derived from impedance cardiography and the ECG were measured. Respiration was paced at 14 breaths/min to facilitate comparisons of respiratory sinus arrhythmia across conditions. No differences among baseline or tasks were found for respiratory rate or cardiac output. The pattern of results for hand immersion was that of increased heart rate with moderate blood pressure increases. In contrast, the forehead and facial cooling tasks elicited small heart rate decreases with little change in blood pressure. Facial cooling elicited significantly more vagal activation than hand cooling as indexed by respiratory sinus arrhythmia. The patterns of response for facial and forehead cooling were almost identical. Probable reasons for the lack of significant blood pressure responses during the facial and forehead cooling are discussed.     

Flow-volume curves during hand immersion in water at 5 degrees C (the cold pressor test)

Seven healthy subjects immersed a hand for 2 min in cold water at 5 degrees C (the standard cold pressor test) with and without beta-adrenoceptor blockade. Control immersions in warm water were also performed. The maximal and partial flow-volume curves as well as the arterial blood pressure, heart rate and body and hand temperatures were recorded before, during and after the hand immersion. The blood pressure rose significantly during the cold pressor test, but the airflow variables did not change significantly, whether or not propranolol had been given. It is concluded that, even though the standard cold pressor test induces sympathetically-mediated cardiovascular responses, it does not produce a bronchodilatation.     

Hemodynamic profile of stress-induced anticipation and recovery.

Systolic and diastolic blood pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured in 100 healthy men and women with the aim of investigating hemodynamic profile during anticipation of, and recovery from, exposure to active and passive laboratory stressors. A 5-min anticipatory period preceded two tasks, both of which lasted 2.5 min. The tasks were mental arithmetic ('beta-adrenergic' stress) and the cold pressor test ('alpha-adrenergic' stress). Each task was followed by a 5-min recovery period. Blood pressure and heart rate were measured with a FinaPres 2300e, and stroke volume, cardiac output, and total peripheral resistance were computed from these parameters. Salivary cortisol was measured in relation to both tasks, and participants completed tests of state and trait anxiety, locus of control, and hostility. As expected, mental arithmetic and the cold pressor test elicited myocardial and vascular patterns of reactivity, respectively. However, contrary to expectations, anticipatory and recovery hemodynamic profile involved essentially vascular responding for both stressors. Salivary cortisol increased in response to both tasks but only weakly correlated with hemodynamic changes. None of the subjective measurements was a strong predictor of physiological reactivity. The findings suggest that stress-induced anticipatory and recovery reactivity may be generally vascular rather than myocardial. This could have important implications in light of suggestions that anticipatory and recovery responses may be better predictors of subsequent cardiovascular disease than direct stress-induced reactivity.     

The combined effect of the cold pressor test and isometric exercise on heart rate and blood pressure

Summary The purpose of this study was to determine if the cold pressor test during isometric knee extension [15% of maximal voluntary contraction (MVC)] could have an additive effect on cardiovascular responses. Systolic and diastolic blood pressures, heart rate and pressure rate product were measured in eight healthy male subjects. The subjects performed the cold pressor tests and isometric leg extensions singly and in combination. The increases of systolic and diastolic blood pressure during isometric exercise were of almost the same magnitude as those during the cold pressor test. The responses of arterial blood pressure, and heart rate to a combination of the cold pressor test and isometric knee extension were greater than for each test separately. It is suggested that this additional effect of cold immersion of one hand during isometric exercise may have been due to vasoconstriction effects in the contralateral unstressed limb. In summary, the circulatory effects of the local application of cold during static exercise at 15% MVC were additive.     

Influence of fitness and gender on blood pressure responses during active or passive stress

We examined hemodynamic and autonomic components of blood pressure responses during active and passive stressor tasks in a sample of young, normotensive men and women who were physically active but differed on fitness (i.e., VO2peak). During the hand cold pressor, increases in systolic blood pressure were inversely related to fitness among women but not men. Regardless of gender, fitter participants had a greater increase in cardiac pace during mental arithmetic, coherent with a decreased cardiac-vagal component of heart rate variability, and a greater compensatory reduction in stroke volume. Fitness was otherwise unrelated to changes in cardiac output and vascular resistance during the stressor tasks. Our findings suggest that cardiorespiratory fitness augments the cardiac-vagal withdrawal that is characteristic of mental arithmetic. The blunted systolic blood pressure response to the hand cold pressor among fitter women suggests that cardiorespiratory fitness should be considered as a covariate in studies that examine the hand cold pressor as a predictor of future hypertension among women.     

Evaluation of Myocardial and Peripheral Vascular Responses During Reaction Time, Mental Arithmetic, and Cold Pressor Tasks

The primary purpose of this study was to examine the covariation of cardiac output and forearm blood flow during reaction time, mental arithmetic, and cold pressor tasks. Cardiac output was indexed using impedance cardiography, whereas impedance venous occlusion plethysmography was used lo index forearm blood flow. Cardiac output increased significantly over resting values in all three tasks, hut the pattern of these increases differed. Large heart rate increases during mental arithmetic and cold pressor tasks more than offset stroke volume decreases; the increases in the reaction time task were due to relatively smaller heart rate increases with stroke volume augmentation. For forearm blood flow, all task levels were higher than resting levels, but only mental arithmetic levels were statistically higher. The correlation between cardiac output and forearm blood flow change was significant for the reaction time task, but not for the mental arithmetic or cold pressor tasks.     

Myocardial and Peripheral Vascular Responses to Behavioral Challenges and Their Stability in Black and White Americans

The purpose of this study was to assess the short term stability of myocardial and peripheral vascular responses to behavioral challenges, and to compare the response patterns of Black and White men. Blood pressure and heart rate, as well as stroke volume, cardiac output, total peripheral resistance, and systolic time interval measures derived from the impedance cardiogram were obtained in 12 Black and 12 White men. These measures were taken prior to and during an evaluative speech stressor, a mirror star tracing task, and a forehead cold pressor test presented during two laboratory sessions scheduled two weeks apart. In general, total peripheral resistance and impedance-derived baseline measures showed acceptable reproducibility (G greater than .85). With a few exceptions, adequate reliability was also demonstrated for change (delta) scores. All tasks raised blood pressure responses above resting levels. Blacks demonstrated significantly greater increases in total peripheral resistance responses across tasks. Whites but not Blacks also revealed increases above baseline in cardiac output and contractility as estimated by the Heather Index. These findings are consistent with the view that Blacks show greater vascular responsiveness than Whites across a variety of tasks, but reveal less myocardial responsiveness.     

Pressor response buffering by beta-adrenergic and cholinergic vasodilation in tranquilized dogs.

Buffering of alpha-receptor-mediated pressor responses by beta-adrenergic or cholinergic vasodilation in tranquilized, chronically instrumented gos was investigated. Increases in aortic pressure were produced in the same animal by intravenous injections of phenylephrine in the control state and in three successive experimental states by 1) pacing the heart to remove the reflex capability to lower heart rate, 2) pacing the heart and beta-blockade to remove beta-adrenergic vascular buffering, and 3) beta-blockade plus atropine to also remove cholinergic vascular buffering. The pressor response in each experimental state was greater than that in the state preceding it. With the combined beta-adrenergic and cholinergic blockade, the pressor response to an alpha-receptor stimulation was three times greater than that of the control state. From an analysis of the components of the pressor response, cardiac output, and peripheral resistance, it is suggested that normal buffering of an alpha-mediated pressor response may include beta-adrenergic and cholinergic vascular dilation in addition to a decrease in heart rate.     

Ten-year stability of cardiovascular responses to laboratory stressors

In this study we examined test-retest stability of cardiovascular stress responses over a decade of the life span. Participants were 55 male college undergraduates. 19 years of age at initial testing, and 29 years of age at follow-up testing Stressors were a foot cold pressor and an aversive reaction time task. Cardiovascular measures included systolic and diastolic blood pressure, heart rate, and preejection period. For cold pressor, the magnitude and pattern of cardiovascular responses remained unchanged at the 10-year follow-up. For the reaction time task, the characteristic cardiovascular response patterns was preserved but with significant attenuation of magnitude. The present findings are consistent with previous observations of temporal stability but over a substantially longer test-retest interval. The long-term stability of stress responses is discussed in the context of stress test methodology, behavioral response demands, and maturation of the physiological systems involved in cardiovascular response expression.     

Regulation of cardiac function during a cold pressor test in athletes and untrained subjects

By using (dP/dt)/P of carotid artery pulse, a non-invasive index of cardiac contractility, we examined the regulatory mechanism of cardiac function during a cold pressor test in athletes and untrained subjects. Twenty-four healthy subjects (9 athletes, 8 untrained subjects, and 7 hyperreactors of 4 athletes and 3 untrained subjects with a rise of 15 mmHg or greater in systolic and/or diastolic blood pressure) underwent the cold pressor test according to Hines and Brown (Am Heart J 11:1–9, 1936): immersion of the right hand in 4°C water for 1 min. Although mean blood pressure increased during the cold stress in all the groups, cardiac function differed. In athletes, heart rate and cardiac contractility caused cardiac output to increase while total peripheral resistance (TPR) did not change. In untrained subjects, however, heart rate and cardiac contractility tended to decrease cardiac output and thus TPR increased. In hyperreactors, heart rate and cardiac contractility increased during cold stress, and also TPR increased. After the end of the test, heart rate and cardiac contractility decreased only in untrained group. The findings that during a cold pressor test heart rate and cardiac contractility are enhanced in athletes but depressed in untrained subjects indicate that the state of physical training influences cardiac sympathetic neural reactivity to cold stress, except for hyperreactors.     

Evaluation of Beta-Adrenergic Influences on Cardiovascular and Metabolic Adjustments to Physical and Psychological Stress

This study was designed to examine the hypothesis that certain behavioral demands may tend to trigger sympathetic mechanisms which result in metabolically excessive cardiac output elevations. Oxygen consumption and cardiac output adjustments during a contrived reaction-time shock-avoidance task were compared to a cold pressor test in healthy young male adults. The linear cardiac output/oxygen consumption relationship generated by performance on a graded exercise task was used to assess the metabolic appropriateness of cardiac output adjustments to the reaction-time task and cold pressor. The reaction-time task was generally found to evoke metabolically excessive increases in cardiac output, while cardiac output adjustments to cold pressor were more consistent with changes in metabolic demands. However, the tasks were associated with similar heart rate responses, with a significant attenuation in stroke volume during cold pressor accounting for the differential alterations in cardiac output. This finding suggests a limited reliability for heart rate as an index of cardiac performance. The effects of propranolol, which was employed to evaluate the role of sympathetic influences, indicated that beta-adrenergic mechanisms were responsible for mediating the cardiac output response to the reaction-time task, but only partially contributed to the cold pressor response. Post-hoc analyses of individual differences in cardiovascular reactivity to the reaction-time task suggest that, for hyperreactive individuals, the coping responses evoked by this task may lead to tissue overperfusion with oxygen, thereby providing a stimulus for autoregulatory vascular reflexes which may be associated with the etiology of hypertensive disease.     

Cluster analyses of cardiovascular responsivity to three laboratory stressors

Seventy-three young normotensive male subjects were tested with an experimental protocol that included a reaction time, a mental arithmetic, and a cold pressor task. Physiological variables that were recorded included heart rate, stroke volume, pre-ejection period, blood pressure, total peripheral resistance, and respiratory sinus arrhythmia. In order to identify subgroups of subjects who differed in their pattern of autonomic responses to the tasks, the physiological change scores from baseline to the tasks for each subject were entered into a cluster analysis for each task. Ward's method was used as the clustering algorithm. The cluster analyses identified four clusters for the reaction time and mental arithmetic tasks, and five clusters for the cold pressor task. Although there was a wide range of patterns exhibited by cluster subgroups, most subjects who were reactive to the tasks showed response patterns that were qualitatively similar to the pattern of overall mean response by all subjects, albeit varying considerably in terms of quantitative response. Little evidence was generated for the consistency of extreme beta-adrenergic response from one task to another, although significant consistency was noted when milder beta-responders were included in the comparisons. Some consistency of alpha-adrenergic response noted across tasks, as well as significant consistency of being relatively nonreactive to the tasks.     

Population differences in cardiovascular reactivity to the cold pressor test

The interaction of race and climatic adaptation on patterns of cardiovascular reactivity among young adult males was examined. Malay and Chinese subjects living in a tropical climate in the Orient and Caucasians living in a sub-tropical climate in North America were investigated. The cold pressor test with hand immersion in cold water was used as the stressor. Systolic and diastolic blood pressures, cardiac frequency, cardiac output, and stroke volume were measured. The results provided limited evidence for absence of differences in cardiac reactivity among racial groups and for greater vascular reactivity in the Caucasians. Cold immersion also elicited differential responses which could be partially attributed to differences in acclimatizations status. © 1995 Wiley-Liss, Inc.     

Interactive effects of type A personality and psychological and physical stressors on human cardiovascular functions

The first part of this study examined the relationship(s) between Type A behavior scores and heart rate, blood pressure and impedance derived cardiovascular measures in response to discrete stressors during a standardized psychophysiological assessment. Expts. 2A and 2B considered cardiovascular responses to dynamic exercise stress alone and in combination with psychological and cold pressor tests. Gender and stroke volume changes during the psychological stress correlated 0.45 (P less than 0.02) with Type A score. Subscale scores of Job Involvement correlated 0.78 (P less than 0.02) with stroke volume, total systemic resistance and heart rate during the psychological stressor, and systolic blood pressure during the cold pressor task. The combined effects of psychological stress and dynamic exercise on systolic and diastolic blood pressure were significantly greater than the individual effects of these stressors. The use of impedance cardiography in measuring cardiovascular variables that correlate with Type A behavior, during psychophysiological assessments, may further elucidate our understanding of Type A behavior in addition to providing information about how stress interacts with aerobic exercise.     

Differential β- and α-adrenergic activation during psychological stress

The responsivity of several cardiovascular indices to a computerized mental arithmetic stress and a cold pressor stress were investigated in 22 healthy adult subjects. The major findings were that the largely β-adrenergically driven T-wave amplitude, pre-ejection period, R-wave to pulse interval, and left ventricular ejection time values responded only to mental arithmetic; a significant decrease in cardiac output and increase in peripheral resistance were elicited during the cold pressor test; inter-beat-interval and subjective stress ratings responded significantly to both stresses compared to baseline levels, but more intensely to mental arithmetic than the cold pressor test; blood pressure, stroke volume and the maximum of the first derivative of the raw impedance signal responded unspecifically to both stresses. These findings support the idea that cardiovascular responses to psychological challenge depend on the level of cognitive processing required for the task. In addition, the superfluity of multiple variable measurements to study cardiovascular reactivity in such situations is discussed.