The cold pressor test: Vascular and myocardial response patterns and their stability

The purposes of the present study were to compare the cardiovascular response patterns evoked by three versions of the cold pressor test (either forehead stimulation or hand or foot immersion) and to determine the reproducibility of the responses over a 2-week interval. Blood pressure, heart rate, stroke volume, cardiac output, total peripheral resistance, and systolic time intervals were obtained during rest and during the cold pressor test in 42 young men. Across conditions, the pressor response was supported by peripheral resistance increases with concomitant stroke volume decreases. Although the response panerns were generally similar across sites, exceptions were apparent for heart rate. Forehead stimulation was characterized by no significant change in heart rate, whereas limb (hand or foot) immersion was associated with significant heart rate acceleration. The responses elicited by the three cold pressor test conditions were reliable and showed little evidence of attenuation over the test-retest interval.     

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.     

Postural stability of hemodynamic responses during mental challenge

Laboratory stress testing is typically conducted while subjects are seated, whereas real-life stressors may often be encountered while standing. The present study of 20 healthy young men evaluated blood pressure and underlying hemodynamic adjustments to a standardized mental arithmetic task performed twice while seated and twice while standing. Blood pressure increased during mental arithmetic in both postures, but the underlying hemodynamic determinants of the pressor responses were different for the two postures. Augmented cardiac output was responsible for increasing blood pressure during seated task performance, whereas increased vascular resistance was the mechanism for the pressor response to the task performed while standing. Blood pressure and hemodynamic responses were reproducible subject characteristics for a given posture; test-retest correlations were significant for all cardiovascular measures. However, seated blood pressure responses were not significantly correlated with standing blood pressure responses. In contrast, significant between-posture correlations were found for cardiac output and vascular resistance responses. This preliminary evidence of postural stability of the hemodynamic determinants of blood pressure responses during stress is consistent with growing evidence that hemodynamic response tendencies are robust characteristics of reactivity. Ambulatory monitoring of hemodynamic response patterns during real-life stress may reveal more idiosyncratic profiles of stress reactivity than are displayed by blood pressure responses alone.     

Depressed mood is related to high-frequency heart rate variability during stressors

OBJECTIVE: The purpose of this study was to examine the relationships between depressed mood and parasympathetic control of the heart in healthy men and women at rest and during two stressors. METHODS: Fifty-three healthy college students completed a laboratory stress protocol that included a baseline resting period, a challenging speech task, and a forehead cold pressor task. Depressed mood was assessed using the Beck Depression Inventory (BDI). Parasympathetic cardiac control was measured as the high-frequency (0.12-0.40 Hz) component (HF) of heart rate variability using power spectrum analysis. Blood pressure, respiration rate, and respiration amplitude were measured simultaneously. RESULTS: Participants were categorized as having a high or low depressed mood on the basis of median splits of their BDI scores. Those in the high depressed mood group had significantly greater reductions in HF during the speech task and significantly smaller increases in HF during the forehead cold pressor task than those in the low depressed mood group. Women had significantly greater reductions in HF during the speech task and smaller increases in HF during the forehead cold pressor task than men. However, gender and depressed mood did not interact to predict changes in HF. CONCLUSIONS: Depressed mood is related to the magnitude of decrease in parasympathetic cardiac control during stressors in healthy men and women. These findings extend those of previous studies, in which a similar phenomenon was observed among patients with cardiac disease. Because the participants in this study were healthy, the relationship between depressed mood and parasympathetic cardiac control does not seem to be secondary to cardiovascular disease.     

Cardiovascular and perceptual effects of reporting pain during the foot and forehead cold pressor tests

In research involving the cold pressor test, a tacit presumption is often made that reporting pain during stimulation is not in itself reactive. This study examined whether, for the foot and forehead cold pressor tests, activities involved in reporting pain may affect (a) the evoked pattern of cardiovascular response, and (b) the magnitude of self-perceived pain. In 40 normotensive college men, increases in systolic blood pressure were greater during test sessions that included verbal ratings of pain, as compared to sessions in which pain was not reported. In contrast to its effect on physiological activation, reporting pain did not significantly alter the participant’s perception of the painfulness of the test, on recollection shortly after the test. We conclude, therefore, that reporting pain during the cold pressor test may impose significant additional demands on the cardiovascular system, but it docs not interfere significantly with the processing of nociceptive information. This research was supported by Grants HL 07426 and HL 36588 from the National Heart, Lung and Blood Institute of the National Institutes of Health     

Blood Pressure Reactivity and Perception of Pain During the Forehead Cold Pressor Test

The relationship between blood pressure reactivity and the perception of pain was examined during a series of three forehead cold pressor tests given every other day to a group of 18 male college students. Subjects classified as high reactors on the basis of peak increases in mean blood pressure during cold pressor tests perceived the cold pressor stimulus as more painful than subjects classified as low reactors. The propensity to rate the cold pressor stimulus as painful was positively correlated with the individual level of blood pressure reactivity (baseline-free partial r = .62). Intra-individual correlations between pain and blood pressure responses were unrelated to subjects' reactivity status. Across the 3-min test, correlations between pain and blood pressure reactivity (with the effects of baseline blood pressure levels partialled out) were significant only during periods when levels of responses were relatively high. The heart rate responses were unrelated to pain ratings. Generalizability theory was applied to the analysis of temporal stability of cold pressor reactions. Both blood pressure and pain responses were highly reproducible across three sessions, appearing to express stable individual differences. The efficacy of 800 mg oral ibuprofen in controlling the cold pressor pain was also tested. Analgesic activity of the drug during the cold pressor test could not be demonstrated.     

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.     

Hostility and sex differences in the magnitude, duration, and determinants of heart rate response to forehead cold pressor: Parasympathetic aspects of risk

Recent models hypothesize that hostility confers increased risk of CHD through weaker parasympathetic dampening of cardiovascular reactivity (CVR). We tested this possibility using the forehead cold pressor task, a common maneuver which elicits the “dive reflex” characterized by a reflexive decrease in HR presumably through cardiac-parasympathetic stimulation. Participants were initially chosen from the outer quartiles of a sample of 670 undergraduates screened using the hostility subscale of the Aggression Questionnaire ([Buss, A.H., Perry, M., 1992. The Aggression Questionnaire. Journal of Personality and Social Psychology, 63, 452-459.]). The final sample of 80 participants was evenly divided between men and women and high and low hostility. Following a 10-min baseline, participants underwent a 3-min forehead cold pressor task. The task evoked a significant HR deceleration that was mediated by PNS activation, as assessed by respiratory sinus arrhythmia (RSA). Replicating prior research, men displayed greater decrease in HR. More important, low hostiles maintained larger HR deceleration over time compared to high hostiles although the autonomic basis for this effect was unclear. The findings broaden understanding of hostility and sex-related cardiovascular functioning and support the task as a method for evoking PNS-cardiac stimulation.     

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.     

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.     

Mechanisms of hypotensive effects of a posture change from seated to supine in humans.

The hypothesis tested was that the hydrostatic stimulation of carotid baroreceptors is pivotal to decrease mean arterial pressure at heart level during a posture change from seated to supine. In eight males, the cardiovascular responses to a 15-min posture change from seated to supine were compared with those of water immersion to the xiphoid process and to the neck, respectively. Left atrial diameter and cardiac output (rebreathing) increased similarly during the posture change and water immersion to the xiphoid process and further so during neck immersion. Mean arterial pressure decreased by 12 +/- 2 mmHg during the posture change, by 5 +/- 1 mmHg during xiphoid immersion, and was unchanged during neck immersion. Arterial pulse pressure increased by 12 +/- 3 mmHg during the posture change (P < 0.05) and less during xiphoid and neck immersion by 7 +/- 3 mmHg (P < 0.05). Total peripheral vascular resistance decreased similarly during the posture change and neck immersion and slightly less during xiphoid immersion (P < 0.05). In conclusion, the hydrostatic stimulation of carotid baroreceptors combined with some additional increase in arterial pulse pressure, which also stimulates aortic baroreceptors, accounts for more than half of the hypotensive response at heart level to a posture change from seated to supine.     

Mechanisms of hypotensive effects of a posture change from seated to supine in humans

The hypothesis tested was that the hydrostatic stimulation of carotid baroreceptors is pivotal to decrease mean arterial pressure at heart level during a posture change from seated to supine. In eight males, the cardiovascular responses to a 15‐min posture change from seated to supine were compared with those of water immersion to the xiphoid process and to the neck, respectively. Left atrial diameter and cardiac output (rebreathing) increased similarly during the posture change and water immersion to the xiphoid process and further so during neck immersion. Mean arterial pressure decreased by 12 ± 2 mmHg during the posture change, by 5 ± 1 mmHg during xiphoid immersion, and was unchanged during neck immersion. Arterial pulse pressure increased by 12 ± 3 mmHg during the posture change (P < 0.05) and less during xiphoid and neck immersion by 7 ± 3 mmHg (P < 0.05). Total peripheral vascular resistance decreased similarly during the posture change and neck immersion and slightly less during xiphoid immersion (P < 0.05). In conclusion, the hydrostatic stimulation of carotid baroreceptors combined with some additional increase in arterial pulse pressure, which also stimulates aortic baroreceptors, accounts for more than half of the hypotensive response at heart level to a posture change from seated to supine.     

Cardiovascular reactivity to stress in black male offspring of hypertensive parents

The forearm blood flow (FABF) and other cardiovascular responses of 20 black men with a parental history of hypertension were compared with the responses of 18 black men without a parental history of hypertension. The results showed that sons of hypertensive parents had higher systolic (SBP) and diastolic (DBP) blood pressure than sons of normotensive parents during the initial assessment as well as significantly higher self-determined home SBP. Sons of hypertensive parents had higher SBP responses than sons of normotensive parents during mental challenge and the cold pressor, but there were no group differences in DBP, heart rate (HR), (FABF), or forearm vascular resistance (FAVR) responses to the stressors. Significant positive correlations between HR and FABF responses to the stressors were observed for sons of hypertensive parents. Finally, the results showed that the BP and FAVR responses to the cold pressor (a painful task that elicits alpha-adrenergic activity) were significantly higher than responses to mental challenge (a task that elicits beta-adrenergic activity) for both groups. The implications of these results are discussed in light of current research suggesting that blacks may have a greater tendency toward BP responses mediated by alpha-adrenergic increases in vascular resistance.     

Cardiovascular Responses to Stress: I. Measures of Myocardial Response and Relationship to High Resting Systolic Pressure and Parental Hypertension

A comparison of pre-ejection period (PEP), heart rate (HR), and systolic (SBP) and diastolk (DBP) blood pressure responses to the cold pressor test and a pseudo-shock avoidance reaction time task was performed in 183 young men. These tasks differ in the extent to which they evoke enhanced myocardial and vascular adrenergic activity. Decreases in PEP were more pronounced during the reaction time task, while DBP increased more during the cold pressor test. MR and SBP responses did not differentiate the two tasks. PEP decreases occurred in the absence of any apparent increase in cardiac preload or decrease in afterload. Parental hypertension as determined by physician reports was associated with higher SBP across all conditions. A subgroup of individuals (15%) showed SBP levels >140 mm Hg when typical clinical stethoscopic determinations were made, but less than half as many showed such elevations during a more extended resting baseline using remotely operated devices. High stethoscopic SBP was associated with greater cardiovascular responses to the stressors, while high SBP during the extended baseline was not.     

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.     

Cardiovascular Responses to Stress: II. Relationships to Aerobic Exercise Patterns

A sample of 174 men aged 18–22 years were divided into thirds based on self-reported levels of weekly aerobic exercise. Heart rate, systolic and diastolic blood pressure, and pre-ejection period responses of these low, moderate, and high exercise groups were compared during a pretask rest and a later acclimated rest, a bicycle exercise task, a purported shock-avoidance reaction time task, and the cold pressor test. The low exercise subjects showed higher heart rates and marginally higher diastolic blood pressures than the high exercise subjects at rest. The low exercise subjects also showed greater myocardial responses to the mild exercise task and the reaction time task than the high exercise subjects, as reflected by group differences in heart rate, systolic blood pressure, and pre ejection period measures after covariance adjustment for baseline differences. Group differences observed in response to the cold pressor test were smaller and generally nonsignificant. These results were interpreted as evidence that aerobic exercise training may decrease beta-adrenergic myocardial responses to physical and behavioral challenges.     

The ability of active versus passive coping tasks to predict future blood pressure levels in normotensive men and women

Casual blood pressure (BP) after a 2-year follow-up interval was determined in 40 normotensive men and women (20 Blacks and 20 Whites), who had been initially tested for cardiovascular responses to a variety of active and passive coping tasks, including active speech, passive speech, reaction time, and forehead cold pressor tasks. Stepwise multiple regression analyses were used to identify the best model for predicting follow-up BP. Average systolic blood pressure (SBP) level during cold pressor stress was the single most powerful predictor of casual SBP over 2 years even after controlling for initial resting SBP. Other predictors of follow-up SBP were initial SBP, parental history of hypertension, and heart rate and SBP during passive speech (final model R(2) = .78). For follow-up diastolic blood pressure (DBP), the only significant predictors were initial DBP and male gender. These results contribute to a growing body of literature that suggests that cardiovascular measures observed during stressors have predictive validity above and beyond that of traditional predictor variables.     

Generalization of cardiovascular response: supportive evidence for the reactivity hypothesis.

Cardiovascular responses were monitored while 36 subjects completed a battery of laboratory stressors comprising mental arithmetic, a reaction time task, a speech task, and the forehead cold pressor. Inter-task consistency was assessed for each of 6 physiological parameters for all task pairings. Considerable inter-task consistency for reactivity scores was seen among the psychological stressors for all variables. The question of such consistency between the cold pressor and the psychological tasks was then addressed. The pattern of consistency was not as clear-cut in this case. For systolic blood pressure and pre-ejection period, reactivity scores to the cold pressor did not correlate with those to any of the psychological tasks. In contrast, cardiac output and total peripheral resistance responses showed considerable consistency. The importance of determining the nature of the relationship between psychological and physical stressors is discussed.     

Physiological unloading of cardiopulmonary mechanoreceptors by posture changes does not influence the pressor response to isometric exercise in healthy humans

Summary In recent studies in humans the role of cardiopulmonary baroreflexes in modulating the cardiovascular responses to isometric exercise (somatic pressor reflex) has been investigated by performing static hand-grip exercise during deactivation of cardiopulmonary receptors produced by low levels of lower body negative pressure; however, findings from these studies have not been consistent. The purpose of this study was to investigate whether a more physiological unloading stimulus of cardiopulmonary baroreceptors, obtained by sequentially changing posture, could influence the pressor response to somatic afferent stimulation induced by isometric, exercise. To accomplish this, ten healthy subjects performed a 2-min isometric handgrip (IHG) at 30% maximal voluntary contraction after 10 min of supine rest and, in rapid sequence, after 10 min of sitting and 10 min of standing, at the time when, owing to their transitory nature, the cardiovascular effects, due to arterial baroreceptor intervention should have been minimal. During IHG arterial pressure (BP_a) was continuously and noninvasively measured to quantify accurately the blood pressure response to IHG both in magnitude and time course. Results showed that the pressor response to IHG was not significantly influenced by change in posture, either in magnitude or in time course. The mean arterial pressure increased by 17.4 (SEM 2.5), 18.6 (SEM 1.2) and 17.0 (SEM 1.3) mmHg in supine, sitting and standing [2.3 (SEM 0.3), 2.5 (SEM 0.2) and 2.3 (SEM 0.2) kPa] positions, respectively. Also the heart rate response to IHG was unaffected by change in posture. Most important, the sum of the separate BP_a responses induced by supine IHG and by posture change from supine to sitting (summation of reflexes) was not significantly different from the pressor response observed during sitting IHG (interaction of reflexes). Likewise, the sum of the separate BP_a. responses induced by sitting IHG and by changing postures from sitting to standing was not significantly different from the pressor response to standing IHG. These data indicate that, under physiological conditions, cardiopulmonary baroreflexes do not exert a significant role in modulating the reflex pressor drive from muscles during isometric exercise in healthy humans.     

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.