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ORIGINAL ARTICLES |
From the Psychological Institute III, University of Hamburg, Germany (T.R., A.K.); the Department of Psychology, University of Basel, Basel, Switzerland (F.H.W.); the Department of Psychology, University of Münster, Münster, Germany (A.L.G.); and the Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California, and the VA Palo Alto Health Care System, Palo Alto, California (W.T.R.).
Address correspondence and reprint requests to Thomas Ritz, PhD, Psychological Institute III, University of Hamburg, Von-Melle-Park 5, D-20146 Hamburg, Germany. E-mail: thomas.ritz{at}uni-hamburg.de
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODRESULTSDISCUSSIONNOTESREFERENCES |
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Method: Ten film clips were shown, two in each of 5 categories: pleasant, unpleasant, neutral, BII-related (surgery), and asthma-related (portraying labored breathing). For each subject, two subsets were created, each containing one clip from each category. For one subset, the instruction was simply to view the film, and for the other subset, to view the film while tensing the leg muscles. PCO2, heart rate, blood pressure, and leg electromyogram were recorded continuously during viewing, and self-report of symptoms and emotion was collected after each film.
Results: Patients reported the greatest anxiety and disgust during surgery films. PCO2 was relatively stable throughout all categories except surgery films, during which minima were below 30 mm Hg, indicating significant hypocapnia. Cardiovascular variables suggested biphasic patterns in two patients with BII phobia. These patients, together with one additional patient and one control who were close to fainting after or during one surgery film, also showed a marked fall in pCO2. Leg muscle tension raised heart rate and systolic blood pressure for all films, but was not related to near-fainting or endurance in surgery film viewing.
Conclusion: Hyperventilation is part of the fear response of patients with BII phobia, but was transitory in experimental fear induction using surgery films. Its role in real-life exposure and fainting deserves further study.
Key Words: blood–injection–injury phobia • anxiety • respiration • hyperventilation • fainting • vasovagal response
Abbreviations: BII = blood, injection, and injury; HR = heart rate; SBP = systolic blood pressure; DBP = diastolic blood pressure; EMG = electromyogram; MFS = Medical Fear Survey.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONNOTESREFERENCES |
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Little is known about the role of hyperventilation in the physiological response pattern and the experienced distress of patients with BII. Hypocapnic hyperventilation, defined by subnormal arterial pCO2 levels (e.g., <30 mm Hg; (5)), can induce or aggravate anxiety, at least in patients with anxiety disorders (6,7). In healthy individuals, reductions in pCO2 are part of the fight–flight response and have been linked to states of emotional distress (8) or stronger workload (9). Experimental induction of vasovagal syncope by tilt-table testing has yielded evidence for increases in ventilation before onset of fainting responses (10,11). Steptoe and Wardle (12) observed initial increases in respiration rate in blood-sensitive students while watching an operation film, but pCO2 was not measured. Because cerebral vasoconstriction is part of the hypocapnic response pattern (13), it can be speculated that hyperventilation may ultimately promote the development of fainting responses in BII phobia. In orthostatic stress, hyperventilation has been shown to further increase reductions in cerebral blood flow (14). This motivated us to investigate end-tidal pCO2 levels in patients with BII phobia and nonanxious controls during experimental induction of disease-specific fears. To study the specificity of this fear state in eliciting hypocapnia, we compared patients’ responses to presentation of different disease-related films and films designed to induce positive or negative emotions.
Voluntary contraction of the skeletal muscles (applied tension) has been used in behavioral therapy of blood phobia as an easy maneuver for counteracting vasovagal dysregulation (1,15,16). To investigate effects of applied tension on pCO2, participants were instructed in one condition to tense leg muscles during viewing. Because pCO2 increases during muscle activity, applied tension could also counteract hypocapnia to a certain extent.
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METHOD |
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Participants were paid $60 for participation in this part of the study. The study was approved by local ethics committees, and informed consent was obtained from all participants.
Film Clips
We created ten film clips (between 150 to 300 s) from commercially available movies, medical education films, and libraries of emotion-producing films (19). Two films of each category were selected: unpleasant (bullying scene at school, boy who cries about the death of his father), neutral (economics lecture, screensaver), pleasant (scenes from a British comedy series, extract from an American comedy film), films with relevance to asthma (scene with an asthma attack, emotionally charged scenes with labored breathing and wheezing), and films with relevance to BII phobia. The two BII film clips were extracted from operation videos for education in surgical procedures, both of which included needle/injection images. The first clip showed scenes of cardiac surgery, including initial blood-taking with blood spilling, chest being opened with a saw, and surgical procedures on cardiac vessels (270 s); the second film showed scenes of a hip graft surgery with opening of the upper and lower leg, drilling a channel through the bloody tissue into the bone and application of a large caliber cannula by use of a hammer, extraction of dead bone marrow, and harvesting of a transplant from the lower leg (300 s).
One set of films with one from each category was shown with the instruction to simply view the entire film clip. The other similarly composed set with other clips was shown with the additional instruction to tense the leg muscles throughout viewing the film. The order of the two sets was counterbalanced between groups, and the order of the film clips within a set as well as the assignment of individual films to the two sets was randomized. Leg muscle tension was to be kept at a subjective level of approximately 30% to 50% of the individual’s maximum possible effort. In addition, the legs were to be crossed below the knees and pressed together at the same level of effort. Participants were advised that some of the material they were to view would be of a medical nature and would contain scenes with blood and wounds. Before the first film clip in the experimental protocol, this warning was repeated, and participants were reminded to try to view the clips for their entire length and not to close their eyes. They were allowed to stop if they felt they were not able to continue viewing the clip, in which case they would signal the experimenter by taking out the tube for respiration measurement and raising their right hand. However, it was stressed that the scientific value of the assessment would be greatest if they continued viewing for as long as possible. The experimenter confirmed that the patient’s eyes were open by closely observing participants through a one-way mirror during the surgery films.
Physiological Measurements
PCO2 in the expired breath was monitored with an infrared capnograph (Datex B; Puritan-Bennett Corp., San Ramon, CA). A plastic tube (1.2 mm diameter) sampled exhaled air continuously at a flow rate of 150 mL/min. It was connected to the distal end of a second flexible tube (approximately 80 cm length, 85 mL deadspace) through which participants breathed during the films for additional lung function measurements. As a result of a leak in the connecting tube, pCO2 was not recorded correctly for one additional patient. Because this measure is the focus of the present analysis, all of the data from this patient was excluded.
ECG was measured with three Ag-AgCl electrodes. One was placed on the sternum and one laterally on the left costal arch at the level of the 10th rib. A ground electrode was placed on the left clavicle. Measurements were lost for one patient with BII during one set of films as a result of a defective lead.
Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were monitored beat-to-beat with a Finapres model 2300 (Ohmeda, Madison, WI). The Finapres cuff was fitted to the middle phalanx of the middle finger of the left hand. As a result of connector problems, BP was not recorded for one patient during the first three films; however, the experimenter made notes of approximate average values after watching the numerical display of the equipment throughout the films. A second patient felt highly uncomfortable with the pulsing sensation of the cuff, and so the experimenter switched the Finapres device off to avoid contamination of all other measurements with the increased arousal and agitation that the cuff would cause. Finapres measurements were incomplete in three healthy participants because of reduced blood flow (cold fingers) or equipment malfunction.
Electromyographic (EMG) activity was recorded from the right leg to check for compliance with the leg muscle tension instructions. We used Ag-AgCl electrodes (5 mm inner diameter) positioned according to an approximate soleus placement (20). Data from one patient and 3 controls were uninterpretable as a result of defective leads.
All signals were amplified and sampled at 512 Hz using a Vitaport 2 digital recorder/analyzer with a 16-bit A/D converter (21) for storage on a IBM-compatible microcomputer (Intel Pentium II processor). For storage, sampling rate was reduced to 256 Hz for the plethysmographic pulse wave and 32 Hz for pCO2. Raw EMG was rectified and integrated with a time constant of 62.5 ms.
Psychological Measures
The Medical Fears Survey (MFS) (22) exploring fear of BII-related situations with subscales for "Injection & Blood Draws," "Blood," "Sharp Objects," "Mutilations," and "Examinations and Symptoms as Intimation of Illness" was filled out before the laboratory session along with other questionnaire measures. Questionnaire data from one patient and one control were incomplete. During the session, participants rated their experienced emotions and symptoms during each film on a list with 11-point rating scales (0 = "not at all," 10 = "extremely"). For the present analysis, ratings of anxiety, disgust, shortness of breath, lightheadedness, dizziness, nausea, feeling faint, and heart racing were analyzed. In addition, ratings of arousal and dominance from the Self Assessment Manikin (23) were analyzed. The scale was scored with 1 assigned to the "calm" and "being controlled" pole of the scale and 9 to the "excited" and "in-control" pole.
Procedure
Participants were invited for individual laboratory sessions between 2:00 pm and 7:00 pm. Patients with BII phobia were scheduled for an additional interview and a 12-lead ECG. The experimental session took place in a sound-attenuated chamber with two small rooms. In one room, the participant sat in a comfortable arm chair facing a TV screen (approximately 40 cm diagonal) positioned at a distance of approximately 1.5 m. The chair could be tilted backward to bring the participant toward a horizontal position if fainting should occur. During physiological measurements, the experimenter sat in the adjacent room, from where he was able to observe the participants through a one-way mirror and to communicate through an intercom. After sensors had been attached, initial test recordings were performed to familiarize the participants with the procedures. After brief calibration measurements, the experimenter explained the protocol again in detail, and the first series of five films was shown with the scheduled instruction (viewing only or viewing with muscle tension). After each film, the participants rated their emotional experience and symptoms. In addition, after each of the surgery films, the experimenter briefly inquired about the current mental state of the participants. If they felt dizzy or faint, the chair was brought into the horizontal position and cushions were placed to raise the legs above head level. After the last film, the participants were freed of the sensors and debriefed.
Data Reduction and Analysis
Data reduction procedures were executed using customized interactive programs for biosignal analysis. The end-tidal pCO2 for each breath was identified by raters who were blind to group assignment and experimental condition. Only breaths with a distinctive CO2 plateau were considered (24). For each film, the breath with the lowest end-tidal pCO2 was selected as an index of peak hyperventilation. In addition, an average end-tidal pCO2 score was calculated as an index of tonic hyperventilation, averaging the values for four breaths before and four breaths after the breath with lowest end-tidal level (for statistical independence, the breath with the lowest level was not included in the index of tonic hyperventilation). Heart rate (HR) was calculated from the time between successive R-waves of the ECG, and mean HR was then calculated across the entire film clip. In addition, to explore whether biphasic autonomic patterns had occurred, minimum and maximum HR, SBP, and DBP were identified from successive 10-s means. For a biphasic pattern, the highest HR, SBP, and DBP maxima followed by the lowest HR, SBP, and DBP minima (as a result of possible vasovagal responses) were expected in the BII patient group.
Three-way repeated-measures analyses of variance (ANOVAs) with two groups (controls versus patients) as the between-individual variable, and two tension conditions (viewing only versus film and tension) and five film categories (unpleasant, neutral, pleasant, surgery, and asthma) as within-individual variables were calculated with physiological measures as dependent variables. Greenhouse-Geisser corrected degrees of freedom were used when the sphericity assumption was violated. For multiple tests of the same physiological parameter, p values of reported ANOVA effects were Bonferroni-adjusted (mean and minimum pCO2, p < .025; mean, maximum, and minimum HR, SBP, and DBP, p < .0167). Specificity in responding of patients to the BII-relevant films would be demonstrated by significant group-by-film interactions. In addition, two a priori contrasts (overall significance level p < .05), one for each group, BII phobia and control, were calculated for mean and minimum of pCO2, minimum and maximum of HR, SBP, and DBP, and ratings of emotion and symptoms, in which the values of the surgery film were compared with the mean values of all other films for both groups. It was expected that only the former would be significant. For all other comparisons of means, the Tukey HSD test was used (significance level was set to p < .05). No hypothesis had been formulated for patterns of mean HR, SBP, and DBP changes. Between-individual correlations (Spearman’s rho, two-tailed) were calculated to examine the association of the MFS and rating scales with physiological parameters.
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RESULTS |
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Compliance With Film Viewing and Fainting Behavior
Three patients squinted and averted their eyes during surgery films. When asked about how much they had actually seen of the individual film, they estimated between 88% and 99%. One female patient closed her eyes completely 30 s before the end of one surgery film, and the experimenter terminated the presentation. Another female patient showed a vasovagal response after the second surgery film in the muscle tension condition. The film had been terminated earlier after 160 s by the experimenter when she showed signs of extreme distress, gulping, and retching. After the 1-minute recovery measurement, she became pallid and reported feeling faint. To reduce the possibility of a full syncope, the legs were elevated above head level. She rated both anxiety and disgust as the maximum of 10. Another female patient refused to watch either surgery films to the end and requested that the films be terminated after 32 s (viewing only) and 64 s (film and tension), respectively. Averaged across both films, she rated anxiety as 9 and disgust as 4. Two more female patients refused to continue to view the first surgery film. One stopped the film after 192 s (film and tension condition, ratings of 6 for both anxiety and disgust) and the other after 58 s (viewing only condition, ratings of 5 for both anxiety and disgust). Unexpectedly, one male control participant showed signs of a vasovagal response with a marked cardiac slowing and fall in BP toward the end of the film (viewing only condition), but he did not faint and recovered quickly after the clip ended. He reported having felt close to fainting toward the end of the clip, and rated 2 for anxiety and 7 for disgust.
Effects of Films on Physiological Measures
Physiological Measures During Neutral Film Viewing
There were no significant differences between patients and controls in mean levels of pCO2, HR, SBP, and DBP during viewing of the neutral film (Table 1). Patients with or without BII-related history of fainting were not significantly different from each other in these measures.
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End-Tidal pCO2
Patients with BII had lower minimum pCO2 during the surgery film than during other films and than nonanxious controls (F[4, 96] = 3.80, p = .014, 
= 0.78 for the group-by-film interaction). Minimum values of pCO2 fell below 30 mm Hg in patients with BII during the surgery film (Fig. 1). The a priori contrast was significant for patients (F[1, 24] = 11.62, p = .004), but not for controls (F[1, 24] < 1). Mean pCO2 levels reflected these effects (F[4, 96] = 8.41, p < .001, = 0.70 for the group-by-film interaction), but they remained well above 30 mm Hg.
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In terms of individual responses, 7 patients showed pCO2 minima below 30 mm Hg in the viewing only condition and 6 patients in the viewing with tension condition. The patient who almost fainted after recovery had a minimum pCO2 of 25.1 mm Hg during the surgery film, compared with 33.2 and 36.3 mm Hg during the unpleasant and neutral films, respectively. The healthy control who was close to fainting during one surgery film (viewing only) had a minimum pCO2 of 39.1 mm Hg, compared with 44.7 and 46.3 mm Hg during the respective unpleasant and neutral films. Two patients who showed biphasic response patterns (see subsequently) during the surgery film (viewing only) had pCO2 minima of 29.0 and 30.1 mm Hg, compared with 42.3 and 37.0 mm Hg during the unpleasant film and 43.0 and 39.9 mm Hg during the neutral film.
Cardiovascular Activity
A significant group-by-film interaction was also found for HR (F[4, 92] = 6.68, p < .001, = 0.64). HR was higher in patients during the surgery film than during the pleasant and neutral film, but not in controls. Maximum and minimum HR also yielded group-by-film interactions (F[4, 92] = 6.35 and 4.21, p = .003 and .012, = 0.66 and 0.72, respectively). A priori contrasts were substantial only for patients (F[1, 23] = 9.20 and 5.59, p = .012 and .054 for maximum and minimum HR, respectively), with higher values in patients during the surgery film compared with the other films, thus indicating no evidence for a biphasic pattern.
Maximum SBP was higher in patients during surgery films than other films and than control participants. The group-by-film interaction was not significant after Bonferroni correction (F[4, 80] = 2.43, p = .161, = 0.89), but the a priori contrast remained significant (F[1, 24] = 7.45, p = .026). Mean and minimum SBP were also higher during the surgery film, but not significantly. DBP showed no specific effects for patients in surgery clips.
Thus, on average, cardiovascular activity increased specifically during surgery films in patients without indication of a biphasic response pattern. Using the combined criteria of one) activation exceeding the unpleasant film and two) subsequent deactivation below the level of the neutral film, we found two patients with BII showing biphasic patterns in the viewing only condition, one in HR and SBP, and the other in HR, SBP, and DBP. The patient with BII phobia who almost fainted after the recovery period showed elevated HR and lowered SBP during the surgery film, but did not meet our criteria for a biphasic response during the measurement period. Nor did the control participant, who almost fainted; he showed his HR minimum during the surgery film before the HR maximum, and although SBP and DBP minima fell below the neutral film, maxima did not exceed the unpleasant film.
Mean Film Ratings of Emotion and Symptoms
Patients with blood phobia reported significantly more anxiety, disgust, and arousal and less dominance than nonanxious controls for the surgery film clips; the group-by-film interactions were F(4, 96) = 18.40, 17.33, 7.07, 5.96, p’s < .001, respectively. There was no group difference for other films, which had markedly lower anxiety, disgust, arousal, and dominance ratings (Table 2). A priori contrasts were significant in patients for anxiety, disgust, and dominance (F[1, 24] = 100.2, 63.41, and 27.42, p’s < .001, respectively), but not for controls. In terms of individual responses averaged across both conditions, viewing only and viewing with tension, 4 patients reported greater anxiety than disgust, 7 patients greater disgust, and 1 patient displayed similar values. For arousal, contrasts were significant in both groups, but the effect was much stronger for patients (F[1, 24] = 52.89, p < .001) than for controls (F[1, 24] = 5.58, p = .027). Post hoc tests revealed no significant differences in arousal among unpleasant, pleasant, and asthma-relevant films. Arousal was significantly lower for neutral compared with any other films.
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Because pleasant and neutral films often did not elicit any symptom ratings in participants, analysis was restricted to the comparison of the unpleasant, BII-relevant, and asthma-relevant films. Symptoms were particularly marked during the BII film for patients, with significant group-by-film interactions (F[2, 48] = 18.79, 7.74, 11.14, 5.46, and 6.96, p < .001, p = .007, 0.003, 0.024, and 0.008, = 0.94, 0.59, 0.52, 0.57, and 0.64) for short of breath, lightheaded, nauseated, feeling faint, and heart racing, respectively.
Effects of Leg Muscle Tension
Leg EMG was higher during the viewing with muscle tension than the viewing-only condition (F[1, 20] = 9.90, p = .005). Arousal ratings were also higher for tension than for viewing only (F[1, 24] = 6.65, p = .016). Mean pCO2 values were slightly higher during viewing with tension in patients, but the effect was not significant. Mean, minimum, and maximum HR were all higher during tension conditions (F[1, 23] = 23.54, 24.71, and 17.08, p’s < .001, respectively). Similarly, SBP was higher during muscle tension, but only mean SBP was significant after Bonferroni correction (F[1, 20] = 7.07, p = .045). Mean DBP showed a trend toward higher values during tension (F[1, 19] = 5.37, p = .093). Muscle tension of the legs did not systematically influence endurance in film viewing or fainting.
Association of Physiological Responses With Other Self-Report Measures
Patients with higher scores on the MFS Injection and Blood subscales showed lower pCO2 during the surgery films. Across conditions, correlations were consistent in their direction (Table 3).
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For both conditions, viewing only and viewing with tension, greater increases in anxiety and disgust from neutral to surgery films were significantly associated with greater falls in minimum and mean pCO2 and with greater increases in HR for the total sample. However, some variables showed evidence of bimodal distributions, which could bias the correlation coefficients. Only the negative correlation between changes in mean pCO2 and anxiety during the viewing with tension surgery film (r[26] = –0.47, p = .016) was unaffected by concerns over distribution.
For patients with BII alone, a greater increase in disgust was associated with a greater fall in mean pCO2 levels (r[12] = –0.57 and –0.62, p = .052 and .032 for viewing only and viewing with tension, respectively). Greater change in anxiety during viewing only was significantly associated with a greater change in SBP and DBP (r[11] = 0.62 and 0.73, p = .042 and .011).
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DISCUSSION |
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Interestingly, although some between-individual correlations suggested an association between situational anxiety and pCO2 across both groups, within the BII phobic group, pCO2 changes were associated only with trait scales for injection- and blood-related fear and with reports of situational disgust. In addition to anxiety, disgust has been identified as important in the emotional response to BII phobia stimuli (28–31). Indeed, although average ratings of anxiety and disgust did not significantly differ, patients generally reported stronger disgust than anxiety. Ratings of anxiety and disgust did not correlate significantly within the patient group. Thus, further psychophysiological studies with larger sample sizes might profit from subcategorization of patients by disgust versus anxiety proneness. There is currently no agreement about the relevance of disgust to actual fainting (27,28,30).
Although minima of pCO2 fell below levels typically used as criteria for normocapnia (30 mm Hg), average pCO2 levels did not remain in the hypocapnic range for the duration of the surgery films, although in real-life situations, the response might be prolonged. Our films produced too few cases of faintness to evaluate statistically the contribution of hypocapnia. However, we did observe a marked fall in minimum pCO2 values in both participants who were close to fainting and in two more patients who showed a biphasic cardiovascular response.
The diagnostic relevance of hypocapnia in patients with other anxiety disorders is a matter of some debate. Although some authors believed that hyperventilation is particularly important in panic patients (e.g., (6,32–34)), there is evidence that hyperventilation is a nonspecific response to stress (7) or to valence-nonspecific emotional arousal (35). Our study, which used a range of films with pleasant, unpleasant, and asthma-relevant content, did not demonstrate a nonspecific arousal effect on pCO2. This may be because our happiness induction film did not raise arousal as much as the desire imagery condition in the study cited (35). Also, contrary to findings of Van den Hout et al. (7), which suggest similar decreases in end-tidal pCO2 in panic patients, nonpanic anxiety patients, and healthy controls during emotional arousal, our comparison of BII phobics with nonanxious controls indicates a specificity of hyperventilation for phobics during surgery films.1Even if diagnostically nonspecific, the consequences of hyperventilation could very well be disease-specific: While in panic disorder, hyperventilation may trigger fear and catastrophizing thoughts (39) or conversely may help to avoid feelings of suffocation from a hypersensitive respiratory control system (40), in BII phobia, hypocapnic breathing could aggravate a tendency to faint. If hyperventilation was shown to play a role, breathing exercises targeted at reducing hypocapnia (41,42) could be of benefit for these patients.
We did not find evidence for biphasic response patterns in the majority of our patients with BII. In the one patient who reported beginning feelings of lightheadedness and nausea during recovery, HR, SBP, and DBP did not drop below levels of recovery from the neutral film. Evidence for a vasovagal response was observed in one control participant, who showed a fall in these physiological parameters well below levels of the neutral film. Maxima of cardiovascular activation during the surgery film did not suggest a substantial sympathetic activation preceding the vasovagal response. At study entry, he had reported having no problems with seeing blood and was surprised by his response. Indeed, a substantial number of individuals who faint when confronted with BII stimuli do not report being anxious (43). We do not know whether the three patients who refused to watch one or both surgery films to the end would have fainted. Two reported that there was no way they could bear looking at the scenes, whereas the third reported feeling "sick to the stomach" and being worried that she might vomit. Only the first two had a history of BII-related fainting.
In general, the observed patterns of respiratory and autonomic reactions suggested a predominance of the fight–flight response over vasovagal responses in patients with BII, which was most clearly observed in pCO2 decreases and HR increases.2At least one other study found evidence for only a fight–flight response to BII film stimuli (25), and the proportion of patients showing actual fainting responses to surgery films has also been low in other studies (12,16). Failure to observe vasovagal responses under experimental conditions may have to do with insufficient exposure or postexposure time. Emotion-induced fainting has been postulated to occur within a few minutes of confrontation with the threat (1), but longer exposures may be necessary in certain patients with BII. Öst et al. (15) using presentation times of up to 30 minutes induced fainting or near-fainting in 5 of 18 patients with BII. Notably, they observed the maximum vasovagal responses after 4 minutes of recovery. Fainting after removal of the threat has been discussed as a typical feature of BII-related distress (2,44). The one patient close to fainting in our study also developed the vasovagal response after the 1-minute recovery, although physiological values were still normal during recovery. Thus, a protocol with longer recovery periods might have detected more vasovagal reactions.
Our conservative criteria led to the identification of only a small number of biphasic response patterns. Currently, there is no consensus on criteria for a biphasic response in patients with BII. We required the maxima of cardiovascular activity to exceed those during an unpleasant film and subsequent minima to fall below those during the neutral film. The unpleasant film controlled for nonspecific arousal associated with negative valence, which BII-related fear should clearly exceed (45). The neutral film controlled for low emotional arousal with attentional engagement, which may reduce cardiovascular activity below baseline levels (46). Using these criteria, we identified biphasic response patterns in two patients with BII. It is conceivable that using these or similar more conservative criteria will lead to identification of few biphasic BII responses in future studies.
As expected, leg muscle tension increased HR and SBP, thus working against vasovagal fainting. However, the tension was probably too mild to increase pCO2 and DBP significantly. Typical maneuvers against BII- or blood donation-related syncope incorporate tension of a larger muscle mass by involving the arms, torso, and legs (15,16). Authors who have used maneuvers of leg crossing and tensing against orthostatic fainting have not reported detailed information on tension levels, but the instruction to press legs together "firmly" (48) probably implies stronger tension than the 30% to 50% of the individual force practiced in our study. Tensing the leg muscles in our study did not prevent the near-fainting response after recovery in one of our patients, during which muscles were relaxed. It may be useful to continue muscle tension well until after exposure to the BII phobic stimulus. It can be speculated that a rebound effect from tension will contribute to development from fainting (see 2). More research is needed on the right amount and timing of tension sequences to prevent vasovagal responses in BII phobia.
In conclusion, hypocapnia is an integral part of the fight–flight response in BII phobia during exposure to BII-relevant films. Mild to moderate tension of the leg muscles did not substantially alter this response. Hypocapnia was greater in patients who scored higher in injection- and blood-related fear, and who reported more disgust for the surgery film. We hope our findings encourage further research on the role of hyperventilation in BII phobia and its relationship to the development of fainting.
The authors thank Alicia Meuret for helpful suggestions; Tana Bliss, Mark Rothkopf, and Alysha Khavarian for their assistance in recruitment and data collection; and Nino Wessolowski for helping with the data reduction.
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2Only relatively weak increases were seen in systolic blood pressure (SBP). BP levels were relatively high, particularly in our patient group. Possible reasons for this high BP are that the Finapres method often overestimates BP; BP is typically higher in practice or hospital settings ("white-coat hypertension"); and basal values of patients may have been elevated in anticipation of seeing disturbing images of blood and medical procedures. Because film order was randomized, this anticipation would have been present for all films. We cannot rule out that weaker BP responses were the result of these elevated levels.
This research was supported by grants of the German Research Society (DFG, Project Ri 957/2-1); the National Institute of Mental Health (MH56094); the Palo Alto Research Institute (PAIRE); and the Department of Veterans Affairs.
DOI:10.1097/01.psy.0000170339.06281.07
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