Controlled human exposure to methyl tertiary butyl ether in gasoline: symptoms, psychophysiologic and neurobehavioral responses of self-reported sensitive persons.

The 1990 Clean Air Act mandated oxygenation of gasoline in regions where carbon monoxide standards were not met. To achieve this standard, methyl tertiary butyl ether (MTBE) was increased to 15% by volume during winter months in many locations. Subsequent to the increase of MTBE in gasoline, commuters reported increases in symptoms such as headache, nausea, and eye, nose, and throat irritation. The present study compared 12 individuals selected based on self-report of symptoms (self-reported sensitives; SRSs) associated with MTBE to 19 controls without self-reported sensitivities. In a double-blind, repeated measures, controlled exposure, subjects were exposed for 15 min to clean air, gasoline, gasoline with 11% MTBE, and gasoline with 15% MTBE. Symptoms, odor ratings, neurobehavioral performance on a task of driving simulation, and psychophysiologic responses (heart and respiration rate, end-tidal CO(2), finger pulse volume, electromyograph, finger temperature) were measured before, during, and immediately after exposure. Relative to controls, SRSs reported significantly more total symptoms when exposed to gasoline with 15% MTBE than when exposed to gasoline with 11% MTBE or to clean air. However, these differences in symptoms were not accompanied by significant differences in neurobehavioral performance or psychophysiologic responses. No significant differences in symptoms or neurobehavioral or psychophysiologic responses were observed when exposure to gasoline with 11% MTBE was compared to clean air or to gasoline. Thus, the present study, although showing increased total symptoms among SRSs when exposed to gasoline with 15% MTBE, did not support a dose-response relationship for MTBE exposure nor the symptom specificity associated with MTBE in epidemiologic studies.

Respiratory sinus arrhythmia versus neck/trapezius EMG and incentive inspirometry biofeedback for asthma: a pilot study.

This pilot study compared biofeedback to increase respiratory sinus arrhythmia (RSA) with EMG and incentive inspirometry biofeedback in asthmatic adults. A three-group design (Waiting List Control n = 5, RSA biofeedback n = 6, and EMG biofeedback n = 6) was used. Six sessions of training were given in each of the biofeedback groups. In each of three testing sessions, five min. of respiratory resistance and EKG were obtained before and after a 20-min biofeedback session. Additional five-min epochs of data were collected at the beginning and end of the biofeedback period (or, in the control group, self-relaxation). Decreases in respiratory impedance occurred only in the RSA biofeedback group. Traub-Hering-Mayer (THM) waves (.03-.12 Hz) in heart period increased significantly in amplitude during RSA biofeedback. Subjects did not report significantly more relaxation during EMG or RSA biofeedback than during the control condition. However, decreases in pulmonary impedance, across groups, were associated with increases in relaxation. The results are consistent with Vaschillo's theory that RSA biofeedback exercises homeostatic autonomic reflex mechanisms through increasing the amplitude of cardiac oscillations. However, deep breathing during RSA biofeedback is a possible alternate explanation.

A plethysmographic method for demonstrating the response specificity of the oral vascular bed.

In this paper, we describe a new method for measuring the oral plethysmogram, and we assess its sensitivity and specificity under differing psychological stimulation. Finger and palate pulse amplitudes and blood pressure were monitored while individuals (N = 13) performed several tasks: mental arithmetic, nausea imagery, fear imagery, and anger imagery. Pulse pressure, having a major effect on pulse amplitude, was partialed out in analyses. Palate pulse amplitude increased significantly in response to the degree to which the individual felt irritated, judged, nauseated, or angry. In contrast, finger pulse amplitude changed significantly only in the arithmetic task and, unlike the palate, showed a decreased amplitude with increased irritation and being judged. Results indicate that the oral plethysmogram can serve as a reliable measure of oral mucosal vasomotor reactivity and that it has a different pattern of response specificity than does the finger.

Behavioral task-induced bronchodilation in asthma during active and passive tasks: a possible cholinergic link to psychologically induced airway changes.

This study investigated pulmonary and autonomic reactions to active and passive behavioral laboratory tasks among asthmatic subjects. It also examined the relationship between airway irritability, as measured by the methacholine challenge test (MCT), and autonomic activity and reactivity to these tasks. Fifty-one asthmatic and 37 nonasthmatic subjects were exposed to psychological laboratory tasks involving either active (mental arithmetic and reaction time) or passive (films depicting shop accidents and thoracic surgery) response. The MCT was given to asthmatics in a separate session. Active tasks reduced respiratory impedance, as measured by forced oscillation pneumography. They also increased heart rate and appeared to block vagal activity, as measured by respiratory sinus arrhythmia (RSA). Airway irritability as assessed by the MCT was positively related to amplitude of RSA and to skin conductance levels. Our data suggest that active and passive behavioral tasks may produce different pulmonary effects among both asthmatic and nonasthmatic individuals. Engaging in tasks requiring active responses may produce temporary improvements in pulmonary function. No autonomic differences were obtained between asthmatics and nonasthmatics in physiological response to stress, but greater cholinergic receptor sensitivity was suggested among high responders to methacholine.

Cardiac rhythm effects of .125-Hz paced breathing through a resistive load: implications for paced breathing therapy and the polyvagal theory.

This study examined the psychophysiological effects of slow-paced breathing while subjects breathed through external respiratory resistive loads. Twenty-four normal volunteers completed four 5-min trials of paced breathing (.125 Hz) through an inspiratory resistive wire mesh screen (0 to 25 cm H2O/L/s). Each trial was followed by a 5-min rest trial. There was evidence for hyperventilation and/or fatigue during paced breathing. Also, respiratory sinus arrhythmia (RSA) was elevated in the first minute of paced breathing, and then declined toward baseline. Heart period decreased during paced breathing trials, and fell significantly below baseline during rest periods. These data suggest decreased vagus nerve activity and/or sympathetic activation, following an initial increase in parasympathetic activity during paced breathing. They are not consistent with the use of .125-Hz paced breathing as a relaxation technique, particularly during respiratory resistive stress. Finally, although RSA and average heart period changed synchronously within paced breathing and rest conditions, they diverged in comparisons between pacing and rest. This dissociation suggests that different mechanisms mediate these two cardiac parameters. These data are consistent with Porges' theory that vagal influences on tonic heart rate are mediated by the combined effect of vagal projections from both the nucleus ambiguus and the dorsal motor nucleus, while RSA is mediated only through the nucleus ambiguus alone.

Suppressor effects in the relations of psychological variables to resting blood pressure.

The role of suppressor effects in obscuring the relation of psychological variables and blood pressure was studied. Forty-five nonmedicated patients in a family practice rated themselves relative to their peers on a series of characteristics. Two of these, trapped and lonely, exhibited marked suppressor effects in their relationship with each other and resting blood pressure. Self-ratings of lonely exhibited a moderately strong positive association with ratings of trapped (r = .63) while only ratings of lonely showed a significant correlation with resting systolic blood pressure (r = .31). Yet when the suppressor effects of the ratings on feeling lonely were removed in the regression analyses, the ratings on feeling trapped showed a significant positive association with resting systolic pressure (r = .42). Similarly, while neither ratings on feeling lonely or on feeling trapped showed separately a significant association with resting diastolic pressure, when suppressor effects were removed in the regression analyses, the ratings of trapped were significantly associated with diastolic pressure in a positive direction (r = .34) and ratings of lonely were significantly associated in a negative direction (r = .33). The significance of this specific suppressor effect and the implications of suppression for psychosomatic research are discussed.

Issues in biometrics: offset potentials and the electrical stability of Ag/AgCl electrodes.

There has been a continuing interest in many areas of psychophysiological research in the quantification of slow wave bioelectric potentials recorded from the surface of the skin. However, surprisingly little research has focused specifically on methods for stabilizing and minimizing the offset potentials of the sintermetallic Ag/AgCl surface electrodes commonly used in such noninvasive bioelectric measurement. To provide empirically based recommendations in this regard, we contrasted the effects of three common storage methods (air dry vs. saline vs. carbon rod) on the two distinct types of Ag/AgCl surface electrodes (sintermetallic vs. electrolytic) under simulated experimental conditions. The obtained results confirm that minimum offset potentials and maximum stability for electrolytic Ag/AgCl electrodes are obtained when they are stored in a 0.9% NaCl solution with their leads shorted together and connected in parallel to a carbon rod partially immersed in the solution (cf. Cooper, 1956). In addition, the pattern of results suggested that the inter-session unshorted storage of sintermetallic electrodes in a mild saline solution is to be recommended over either shorted saline storage in parallel with a carbon rod or unshorted dry storage.

The menopausal hot flush: symptom reports and concomitant physiological changes.

Hot flushes are the most frequently reported menopausal symptom. The primary study goal was to develop criteria for the identification of hot flushes that ultimately could be applied independent of symptom report. Twenty-one postmenopausal women each underwent psychophysiological monitoring. Physiological activity accompanying their 93 subjective flush reports was compared with activity during nonflush periods, and a discriminant function analysis was carried out. The Physiological Flush Profile (PFP), developed on the basis of these analyses, consists of peripheral vasodilation plus an increase in skin conductance (sternal and/or palmar), both of a specified magnitude. The PFP was shown to be both a specific and a sensitive measure of hot flushes. Notably, change in sternal skin conductance was highly positively correlated with subjective flush severity ratings. Potential applications of the PFP toward delineating the role of psychological factors in the reporting of menopausal symptomatology are discussed.

Impact of stress on objectively recorded menopausal hot flushes and on flush report bias.

The hot flush (or flash) is the most widely reported menopausal symptom. Anecdotal reports suggest that women experience more hot flushes when stressed. Although stress may actually trigger hot flushes, another possibility is that women under stress may be more aware of the physiological changes associated with flushes and, therefore, more likely to report them. The goal of this study was to test these hypotheses by investigating the association between stress and both objective (i.e., physiologically recorded) and subjective hot flushes. Twenty-one postmenopausal women who reported having frequent hot flushes each underwent psychophysiological monitoring during stressful and nonstressful laboratory sessions. Significantly more objective flushes were recorded during the stress session than during the nonstress session. The stress manipulation, however, did not affect subjects' propensity to report flushes. These results suggest that the observed association between reported hot flushes and stress is not due to changes in report bias. The physiological mechanisms through which stress may stimulate hot flushes are discussed.

Relationship of expressed anger to forearm muscle vascular resistance.

The relationship of style of anger expression to physiological reactivity was examined in 45 nonmedicated subjects during their performance of three tasks with contrasting response demands. The primary physiological focus was on forearm muscle vascular resistance (FMVR) with forearm muscle blood flow (FMBF), digital pulse volume (DPV), digital vascular resistance (DVR), heart rate (HR), diastolic blood pressure (DBP), systolic blood pressure (SBP), and electrodermal frequency (EF) monitored. Family Expressed Anger, i.e. the overtness of anger expression in the subject's family of origin, was related to FMVR such that the more anger was expressed in the family of origin, the greater the vasoconstriction during Mental Arithmetic and the less the vasoconstriction during Anger Imagery. Self Expressed Anger, i.e. the degree to which others were aware when the subject was feeling angry, was related to SBP and DBP during Vigilance with a lesser degree of anger expression going with greater blood pressure increases. The meaning of these findings in relation to task appraisal and task demand is discussed.

Relationship of resting blood pressure and heart rate to experienced anger and expressed anger.

Forty-five nonmedicated subjects rated on analog scales the anger they experienced at home and at work (Experienced Anger). They also rated the extent to which others were aware of their anger (Expressed Anger) and the extent to which anger had been expressed in their families or origin (Family Expressed Anger). They were then physiologically monitored during a 2-min relaxation period that followed habituation to the laboratory setting. For the group as a whole, Expressed Anger was inversely related to systolic (SBP) and diastolic (DBP) blood pressure while Family Expressed Anger was inversely related to SBP only. When the sample was divided into normotensive and hypertensive subgroups, the normotensives showed significant associations between Experienced Anger and SBP, Expressed Anger and DBP, and Family Expressed Anger and SBP. The hypertensive subgroup showed no significant associations. Both males and females showed a significant association between Expressed Anger and DBP, but only females showed this relationship with SBP. It is concluded that coping with anger by conscious inhibition of its expression is associated with increases in both systolic and diastolic blood pressure.

The skin conductance orienting response in neuroleptic-free schizophrenics: replication of the scoring criteria effect.

It has been suggested that the use of invalid scoring criteria might be responsible for the finding of excessive nonhabituation of the skin conductance orienting response (SCOR) in schizophrenia. Certain criteria may confuse SCOR and spontaneous SC activity in subjects with high rates of the latter (Levinson et al. 1984). To replicate this finding, data were reanalyzed from a study of 25 neuroleptic-free schizophrenic patients and 23 normal male subjects. Analysis of response latency and amplitude during a habituation paradigm of 11 78.5-dB tones confirmed the predictions. Broad scoring criteria (SCOR onset 1-5 sec poststimulus, and a three-no-response-trials habituation criterion) produced significantly different habituation scores than more restrictive criteria (1.6-3.0 sec latency window and a two-trials habituation criterion). Nonhabituation was scored in five patients and six normals by the former criteria, but in no patient and one normal by the latter. Nonhabituators, defined by using the broad criteria, had higher rates of spontaneous activity. The narrow latency window contained significantly more responses than could be explained by the spontaneous activity rate, but this was not true for the added time permitted by the broad window. It is concluded that the use of more restrictive scoring criteria may help to clarify the validity of SCOR nonresponse or hyporesponse as a marker for a type of schizophrenic illness.

The paradoxical relation between diastolic blood pressure change under stress and the H factor of the Jenkins Activity Survey.

This study examined the relation of the Type A scale and of the three factors of the Jenkins Activity Survey to the cardiovascular responses of twenty-six subjects during two stressful tasks. The two tasks were reaction time (RT) and paced arithmetic (PA) and the sample was drawn from a general medical practice. While heart rate correlated directly with the subject's score on the Hard Driving and Competitive Factor (H), diastolic blood pressure response to PA was inversely related to the subject's Type A and factor H scores. This paradoxical inverse relation remained highly significant when the diastolic pressure in the rest preceding PA was statistically controlled.

The orienting response in schizophrenia: proposed resolution of a controversy.

The habituation of the skin conductance orienting response ( SCOR ) was studied in 36 schizophrenic and 11 normal male subjects. Scoring criteria significantly influenced results: more inclusive criteria (used in most SCOR studies) scored 56% of patients as nonresponders and 19% as slow habituators . More restrictive criteria scored 75% of patients as nonresponders, and the remainder as faster habituators than normals. The faster habituation of patient responders could be explained by the effects of low response amplitude. Evidence is given for the greater validity of the restrictive scoring criteria; on this basis the schizophrenic patients in this study were SCOR nonresponders or fast habituators . The data suggest that the more inclusive scoring criteria can confuse spontaneous and orienting activity. Clinical and theoretical implications are discussed.

Psychological effects of dopamine beta-hydroxylase inhibition: a failure to replicate.

In a previous investigation of whether reduced dopamine-beta-hydroxylase (DBH) might play a role in schizophrenia, we studied the effects of DBH inhibition for a few hours in normal subjects. This initial study showed positive effects, i.e., unusual subjective psychological reports confirmed by psychiatric rating scales, in subjects given the DBH inhibitor fusaric acid. The present study attempted to replicate these findings using a more detailed battery of tests and an additional control situation. Each subject underwent the following four treatment conditions at 1-week intervals: fusaric acid plus L-dopa; L-dopa alone; d-amphetamine; placebo. The present results did not confirm those of the first study. A few interesting results were found that were chiefly attributable to amphetamine effects. No effect could be definitely attributed to fusaric acid.

Relation of electrical properties of skin to structure and physiologic state.

Interpretation of cutaneous electrical measurements in terms of structure or function requires special techniques for identifying the separate contributions of the various elements. Resistance measures have different implications depending upon whether the subject is sweating and whether the electrode preparation is wet or dry. Microelectrode measurement indicates that the stratum corneum and other epidermal layers represent a significant pathway for ion conductance. Impedance measurement allows estimation of skin capacitance and of the thickness of the capacitative element. When applied to data on excised stratum corneum, this analysis indicates the presence of a relatively impermeable layer less than 2 microns thick, a conclusion subject to some doubt because of uncertainty over the dielectric constant of wet keratin. The use of impedance measurement with closely spaced electrodes gives an indication of the hydration of the superficial horny layer and also demonstrates reabsorption of sweat from this region. Potential measurement at the surface reflects the relative internal resistance of two parallel sources, the sweat glands and an "epidermal generator."