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Source: Behaviour Research and Therapy Vol 45, #11, 2679-2690

November 2007

URL: _http://www.sciencedhttp://wwwhttp://www.scienhttp://w_

(http://www.sciencedirect.com/science/journal/00057967)

 

Hyperventilation in patients with chronic fatigue syndrome: The role

of coping strategies

-------------------------

Katleen Bogaerts(a), Morgane Hubin(b), Ilse Van Diest(a), Steven De

Peuter(a), Boudewijn Van Houdenhove(b)Peuter(a), Boudewijn Van Ho

Crombez©, Omer Van den Bergh(a,*)

 

a Research Group on Health Psychology, Department of Psychology, University

of Leuven, Tiensestraat 102, 3000 Leuven, Belgium

b University Hospital Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium c

Department of Psychology, Ghent University, Henri Dunantlaan 2, 9000 Ghent,

Belgium

* Corresponding author. Tel.: +32 16 32 60 58; fax: +32 0 16 32 61 44.

E-mail address: _omer.vandenbergh_

(omer.vandenbergh) (O. Van den Bergh).

 

Received 19 April 2007; received in revised form 8 July 2007; accepted

16 July 2007

 

Abstract

 

Hyperventilation has been suggested as a concomitant and possible

maintaining factor that may contribute to the symptom pattern of

chronic fatigue syndrome (CFS). Because patients accepting the illness

and trying to live with it seem to have a better prognosis than

patients chronically fighting it, we investigated breathing behavior

during different coping response sets towards the illness in patients

with CFS (N=30, CDC criteria). Patients imagined a relaxation script

(baseline), a script describing a coping response of hostile

resistance, and a script depicting acceptance of the illness and its

(future) consequences. During each imagery trial, end-tidal PCO_2

(Handheld Capnograph, Oridion) was measured. After each trial,

patients filled out a symptom checklist. Results showed low resting

values of PetCO_2 overall, while only imagery of hostile resistance

triggered a decrease and deficient recovery of PetCO_2. Also, more

hyperventilation complaints and complaints of other origin were

reported during hostile resistance imagery compared with acceptance

and relaxation. In conclusion, hostile resistance seems to trigger

both physiological and symptom perception processes contributing to

the clinical picture of CFS.

 

Keywords: Hyperventilation; Chronic fatigue syndrome; Imagery; Coping;

Acceptance; Interoception

 

Introduction

 

The chronic fatigue syndrome (CFS) is a condition characterized by

persistent medically unexplained fatigue, lasting for at least 6

months, the co-occurrence of several other unexplained symptoms, and

severe functional disability (Fukuda et al., 1994).

 

Hyperventilation is defined as a breathing pattern in excess of

metabolic needs (Gardner, 1996). Because more CO_2 is being exhaled

than is produced by the body, arterial partial CO_2 pressure

decreases. This state of hypocapnia induces an increased blood pH and

causes a wide range of bodily symptoms, largely overlapping with those

characterizing CFS (e.g. fatigue, feeling of exertion, muscle pain,

sore throat, headache, loss of concentration, etc.). This overlap has

led researchers to consider the role of hyperventilation in CFS. Yet,

the literature on this topic is limited and inconsistent. Some

researchers believe that hyperventilation is an epiphenomenon of CFS

(Bazelmans, Bleijenberg, Vercoulen, van der Meer, & Folgering, 1997;

Riley, O'Brien, McCluskey, Bell, & Nicholls, 1990; Saisch, Deale,

Gardner, & Wessely, 1994; Tweeddale, Rowbottom, & McHardy, 1994),

whereas others conceive of it as an important perpetuating factor

(Neerinckx, Lysens, Van Houdenhove, & Vertommen, 1999) or even as an

etiological factor (Rosen, King, Wilkinson, & Nixon, 1990; for

discussion, see Lavietes, Natelson, Cordero, Ellis, & Tapp, 1996). Due

to methodological differences, direct comparisons across studies are

difficult, but the best conclusion seems that hyperventilation occurs

in some CFS patients under some circumstances. The important question,

therefore, is which type of patient hyperventilates in which type of

situation.

 

The tendency to hyperventilate typically occurs during action

tendencies characterized by high arousal (Van Diest et al., 2001),

suggesting that specifically CFS patients who anticipate a distressing

and demanding activity may be vulnerable to disproportionate

breathing. Therefore, hyperventilation in CFS patients may only show

up in contexts evoking emotions relevant to them and may not appear as

a stable characteristic of patients across situations. This

perspective may explain the difference between literature suggesting a

limited or non-existing role for hyperventilation in CFS (Bazelmans et

al., 1997; Riley et al., 1990; Saisch et al., 1994; Tweeddale et al.,

1994) and the study of Neerinckx et al. (1999). Whereas the former

studies registered breathing behavior within an emotionally neutral

context, the patients in the study of Neerinckx were preparing for a

demanding exercise test. Hyperventilation was observed in 45% of the

patients. Hence, hyperventilation is not likely to be a causal factor

for CFS, but it might be an important perpetuating factor for some of

the patients.

 

It is known that strategies to cope with a chronic disease may

influence the clinical picture and ultimately the course of the

illness. For example, studies on chronic pain have demonstrated a

positive relationship between acceptance of the disease and lower

subjective pain intensity, less anxiety/depression, less avoidance of

activity, less impairment, more engagement with daily activities, less

attention to pain, fewer health-care visits for pain, and less

medication consumption (McCracken, 1998; McCracken & Eccleston, 2005;

Viane et al., 2003; Viane, Crombez, Eccleston, Devulder, & De Corte,

2004).

 

Research on the role of acceptance in CFS is at an early but promising

stage. For example, Van Damme, Crombez, Van Houdenhove, Mariman, and

Michielsen (2006) showed that acceptance was associated with better

quality of life in a CFS population, whereas it was negatively

correlated with fatigue, functional disability, and psychological

problems. In the present study, we used an imagery paradigm to compare

the breathing behavior during two different action sets, namely

acceptance vs. hostile resistance, towards the illness in CFS

patients. Script-driven imagery is considered a valid and generally

accepted tool to elicit emotions both in psychophysiological studies

(Lang, 1979; Van Diest et al., 2001) and in PET studies on the

neuroanatomy of emotions (Dougherty et al., 1999; Lane, Reiman, Ahern,

Schwartz, & Davidson, 1997). In accordance with definitions in the

area of pain, we defined acceptance of chronic fatigue as a

willingness to live with fatigue without reactance, disapproval, or

attempts to reduce or avoid it. Accepting CFS means giving up the

battle against the illness along with unproductive attempts to control

it, adopting a realistic approach towards the illness, learning to

live with it without losing engagement in positive everyday

activities, and not letting oneself be reduced to the patient's status

(Hayes, Jacobson, Follette, & Dougher, 1994; Risdon, Eccleston,

Crombez, & McCracken, 2003). Conversely, hostile resisting was defined

as fighting the illness and undertaking incessant attempts to control

it. Resisting patients want to become as healthy and energetic as

before, have difficulties with the chronic character of the disease,

and do not want to make any concession. Because the latter strategy is

more likely associated with the mobilization of action tendencies, we

expected to observe the tendency to hyperventilate particularly in the

mental set of hostile resistance towards one's own illness.

 

We also explored the role of worrying, as it is a maladaptive coping

strategy, implying attentional vigilance and exaggerated inference of

threat (MacLeod & Rutherford, 2004). Worrying has been defined as

repetitive thought activity, characterized by an automatic, negative,

and unrealistic interpretation of feared future events. Excessive

worry produces negative emotional states (Borkovec, Ray, & Stober,

1998) and is associated with increased pain reporting (Keefe et al.,

2001) and self-reported illness symptoms (Brosschot & van der Doef, 2006).

 

In the current study, each patient was presented auditorily with four

scripts (neutral, relaxation, hostile resistance, and acceptance),

which she had to imagine as vividly as possible. End-tidal PCO_2 was

measured continuously during imagery and subjective symptoms were

rated after each trial. Hyperventilation was operationalized as a

statistically significant decrease in PetCO_2 from baseline to

imagery. We hypothesized that imagery of the hostile resistance script

(1) would cause a statistically significant decrease in PetCO_2 from

baseline to imagery and (2) would produce more hyperventilation

complaints than imagery of the acceptance and relaxation script.

 

Methods

 

Participants

 

Thirty female participants (21 & shy;54 years) were recruited through a

systematic multidisciplinary screening of CFS patients at the general

internal medicine clinic of the university hospital. Patients

underwent an extensive somatic investigation, effort capacity

measurements, and a psychiatric in-depth interview. All patients met

CDC criteria for CFS (Fukuda et al., 1994). Patients with an

underlying organic disease or a psychiatric condition as possible

explanation of their fatigue were excluded from the sample, as well as

CFS patients with comorbid anxiety disorders. The study was approved

by the local medical ethics committee and all participants provided

written informed consent.

 

Scripts

 

Four scripts were used (Appendix). The neutral script was always

presented first, to familiarize the patients with the instructions and

the procedure of the experiment. Next, the patients imagined a

relaxation script ®, a script describing an action set of hostile

resistance (HR), and a script describing an action set of acceptance

of the illness and its consequences (ACC) in randomized order. We

created two versions of the HR and ACC scripts: one version described

the patient having unexpected visitors and the other version described

the patient waiting in line at a grocery store. Versions were

counterbalanced across patients: patients who imagined the

visit-version for the HR script, imagined the store-version for the

ACC script and vice versa.

 

The neutral script and the relaxation script have previously been used

by our group (Van Diest et al., 2001). The scenarios for the hostile

resistance and acceptance scripts were based on pilot interviews and

clinical observations and were judged as recognizable and familiar by

all CFS patients. No wordings referring to respiratory behavior were

used to avoid response-specific demand effects.

 

Subjective measures

 

Positive and Negative Affect Schedule (PANAS) The Dutch state version

of the PANAS consists of 10 positive (positive affectivity; PA) and 10

negative adjectives (negative affectivity; NA). Participants indicate

on a 5-point scale the extent to which the items apply to his/her

feeling right now. The reliability and construct validity of the PANAS

have been documented (Engelen, De Peuter, Victoir, Van Diest, & Van

den Bergh, 2006; Watson, Clark, & Tellegen, 1988).

 

Symptom checklist Subjective complaints were assessed by the checklist

for psychosomatic symptoms (Wientjes & Grossman, 1994; 39 items). This

questionnaire is an extension of the Nijmegen Questionnaire (16 items;

van Dixhoorn & Duivenvoorden, 1985), which tests hyperventilation.

Other symptoms were added to measure a variety of other symptoms that

frequently occur in psychosomatic patients (see Wientjes & Grossman,

1994, and Han, Schepers, Stegen, Van den Bergh, & Van de Woestijne,

2000 for components and reliability)2000 for components and reliabi

graded intensity response (not at all, a little bit, quite, rather

strongly, very strongly) was required to the question 'To what extent

do (did) you experience the following symptoms at this moment (during

the past imagery trial)?'. Two subscores were calculated and analyzed

separately: (a) hyperventilation complaints and (b) additional

complaints. The hyperventilation subscore was the sum of 14 items:

feeling tense, dizziness, faster or deeper breathing, shortness of

breath, discomfort in or around the chest, palpitations, anxious

feeling, unable to breathe deeply, confusion or feeling of losing

contact with surroundings, bloated abdomen, tingling fingers, chest

pain, stiff fingers or arms, and cold hands or feet. These 14 items

are the core of the Nijmegen Questionnaire and are considered

prototypical symptoms of hyperventilation. The remaining symptoms (25

items) were totalled to form a subset of additional complaints. These

symptoms were considered atypical for hyperventilation. Examples are

stuffed nose, feeling sleepy, low back pain, headache, and burning eyes.

 

Acceptance Chronic Fatigue Test (ACFT) The ACFT is the Dutch version

of the Chronic Pain Acceptance Questionnaire (CPAQ), adapted for

chronic fatigue (Crombez, Van Houdenhove, Mariman, & Michielsen,

2002). Participants indicate on a 6-point scale to what extent 24

statements are applicable to themselves. Following the scoring

procedure of Geiser (1992) a single total score is calculated (with

higher scores reflecting higher levels of acceptance). The original

CPAQ (34 items) is a reliable measure of the tendency to accept

chronic pain (Geiser, 1992). The present questionnaire has not been

validated for CFS. Data from this measure are presented for

exploratory purposes.

 

Penn-State Worry Questionnaire (PSWQ) The PSWQ is comprised of 16

items measuring the trait-like tendency to worry. Participants

indicate on a 5-point scale the extent to which the items characterize

them (1 = not at all to 5 = very characteristic)them (1 = not at

reflect higher levels of worry. The PSWQ has a high internal

consistency, high test-retest reliability, as well as favorable

convergent and discriminant validity (Meyer, Miller, Metzger, &

Borkovec, 1990). We used the Dutch version of the PSWQ, which has been

shown to be reliable and valid (van Rijsoort, Emmelkamp, & Vervaeke,

1999).

 

Self-assessment Manikin Experiences during the imagery trials were

judged on the affective dimensions of valence, arousal, and dominance

(Lang, Bradley, & Cuthbert, 1990; Mehrabian & Russell, 1974), using a

paper-and-pencil version of the 9-point Manikin rating system (Bradley

& Lang, 1994). In this system, values along each of the three

dimensions are portrayed on a continuous scale in a non-verbal,

pictorial way. For the valence dimension, values range from a smiling,

happy figure to a frowning, unhappy figure. The arousal dimension

ranges from an excited, wide-eyed figure to a relaxed, sleepy figure.

The scale ranges from a small figure (dominated) to a large figure (in

control) to represent the dominance dimension. The participant can

indicate any of the five figures comprising each scale, or any value

in between two figures, resulting in a 9-point rating scale for each

dimension. The Self-assessment Manikin has been proven to be a

reliable instrument (Bradley & Lang, 1994).

 

Physiological measures

 

Ventilatory parameters were measured continuously with the LifeShirt

System (VivoMetrics, Inc., Ventura, CA), implying inductive

plethysmography. End- tidal CO_2 was monitored using a nasal

CO_2-sampling cannula connected to the Oridion Microcap® Handheld

Capnograph, with a sampling flow rate of 50 ml/min. The monitor uses

Microstream non-dispersive infrared (NDIR) spectroscopy to

continuously measure the partial pressure of CO_2 (PetCO_2). We

focused on PetCO_2 because it is the most relevant indicator of

hyperventilation. Electrodes for ECG measurement were attached to

avoid demand effects (see Procedure).

 

Procedure

 

The patients were invited to participate in an experiment

investigating physiological changes during imagery. When they agreed,

they signed an informed consent. Next, they were asked to fill out the

PSWQ, the PANAS-state, and the Symptom Checklist, along with a 9-point

scale to indicate their degree of fatigue at that moment (1 = not at

all fatigued to 9 = very much fatigued).

 

Subsequently, the LifeShirt garment was put on and the ECG electrodes

were attached. We used a cover story to avoid drawing the patient's

attention to her breathing: the nose cannula for measuring PetCO_2 was

described to measure the expired air temperature. The electrodes were

explained to detect changes in posture and muscle tonus of the trunk.

 

The patient sat in a comfortable chair in a part of the room that was

separated from the experimenter'separated from the experimenter'<WBR>s

asked to lean back in the seat, to keep both feet on the floor, and to

place her hands on her legs. The experimenter checked whether she was

comfortable, and it was stressed that the patient should keep the same

position during the experiment.

 

The experimenter explained that four different imagery trials would

follow, each consisting of the same consecutive phases. First, during

a 1 min baseline period in which the lights were dimmed, the patient

had to close her eyes and listen to relaxing music that was presented

through headphones (Sarabande, Goldberg Suite, E. Grieg). During the

following minute, the script was presented and the patient had to

start imagery as soon as she heard the text. A 90 s silence period

followed during which the patient had to keep on imagining the scene

(after 60 s, a short low-level auditory signal, announced during the

instructions, was given as a reminder to continue the imagery as

vividly as possible). Finally, a 1 min recovery period followed in

which the patient had to stop the imagery and listened to relaxing

music (Gymnope´die no. 1, E. Satie), still with her eyes closed. At

the end of the recovery period the lights were turned on.

 

The patients were asked to breathe through the nose as soon as the

first imagery trial started. They were instructed to imagine the

scenes as vividly as possible, not only creating a detailed visual

picture of the scene, but also trying to experience the events as if

they were a real, active participant in the scene. The patients were

asked to specifically hold on to the feeling evoked by the last part

of the script.

 

After the first practice trial, the experimenter discussed with the

patient the extent to which she had succeeded in imagining the scene

as an active participant. After this trial - as after each imagery

trial - the patient rated the evoked images on the affective

dimensions of valence, arousal, and dominance (Manikin). The vividness

of the imagery, the ability to concentrate on the scripts, and the

similarity of the evoked feelings to feelings in daily life were

assessed by means of 9-point Likert scales. Then, the fatigue scale,

the Symptom Checklist, and the PANAS state were administered referring

to how the patient felt during the imagery period. It was explained

that the presentation of the remaining three scripts would proceed in

a similar fashion without any further intervention of the

experimenter. Finally, we presented the ACFT and asked whether the

patient had voluntarily controlled her breathing during one or more

imagery trials. Afterwards, participants were fully debriefed.

 

Data analysis

 

The data of the first practice trial (neutral script) were left out of

the analyses. Raw waveform signals for physiological data were stored

on a memory card and uploaded to a personal computer, calibrated, and

reduced (parameter extraction, trend generation) by the VivoLogic

software. This output was visually inspected before exporting the data

to spreadsheets for further statistical processing. Only expirations

with a clear alveolar plateau were used to determine PetCO_2 values.

 

Differences in fatigue scores between the different moments of

measurement were investigated using repeated- measures ANOVA (four

levels: baseline, relaxation script, acceptance script, and hostile

resistance script). We used repeated-measures ANOVAs with script

(three levels: R, ACC, and HR) as the within-subject variable for

hyperventilation complaints, additional complaints, NA and PA scores,

the subjective ratings of valence, arousal, dominance, imagery

vividness, ability to concentrate on the script, and similarity with

feelings in daily life.

 

For the physiological data, three phases were determined within each

imagery trial: baseline (60 s); imagery phase (the last 30 s of script

presentation and the 90 s of silence)^1; and the recovery phase (60

s). To check for baseline differences, mean baseline PetCO_2 was

analyzed in an ANOVA with script (R, ACC, and HR) as the

within-subject variable. Next, we calculated change scores by

subtracting the mean baseline PetCO_2 from the mean PetCO_2 of the

imagery phase. Subsequently, repeated-measures ANOVAs with script as

the within-subject factor were performed on the change scores of the

imagery phase. In addition, mean PetCO_2 of the R script, the ACC

script, and the HR script was analyzed separately in repeated-measures

ANOVAs including phase (three levels: baseline, imagery phase, and

recovery phase) as the within-subject variable.

 

To check for the effects of specific script content (visit vs. store),

script version was added as a between- subject variable to all

analyses. For exploratory reasons, the tendency to worry (median split

of PSWQ scores) and the attitude of (non)acceptance (median split of

the ACFT scores) were added as between-subject variables to all

analyses. Greenhouse-Geisser corrections were applied when appropriate

and corrected degrees of freedom are reported. Follow-up comparisons

between groups were made with either a priori tests or with Tukey HSD

a posteriori tests. Pearson product-moment correlations were computed

to further evaluate the relationships between the variables of

interest. The alpha for all analyses was set at .05.

 

Results

 

Manipulation checks

 

There were no significant effects of the script version (visit vs.

store), neither on the subjective data nor on PetCO_2. Consequently,

the two versions of the script were considered equivalent and script

version was omitted from all analyses. Because fatigue scores were not

significantly different across measurement moments, the mental load of

the experiment was no disturbing factor either. Analysis of the

Manikin scales indicated a successful manipulation of the script

content, in that patients felt less positive, more aroused, and less

in control when placed in the HR script compared with the ACC and the

R script. In addition, no significant differences between scripts were

found for imagery vividness, ability to concentrate, and similarity to

feelings in daily life (Table 1). None of the patients reported to

have voluntarily controlled her breathing during the imagery trials.

 

Subjective data

 

Type of script Imagining an action set of hostile resistance was

associated with the highest level of hyperventilation complaints

(Table 2). This level was significantly higher than when a state of

acceptance or relaxation was imagined. Also, acceptance was associated

with more hyperventilation complaints than relaxation. The additional

complaints showed the same pattern, except that imagining acceptance

did not produce more complaints than relaxation.

 

Comparable effects were obtained for NA. Imagining hostile resistance

produced a level of NA that was significantly higher than imagining

acceptance or relaxation. Acceptance also produced more NA than

relaxation. PA was lower during hostile resistance than during

acceptance or relaxation, whereas the latter did not differ (Table 2).

 

Tendency to worry Overall, high worriers reported more

hyperventilation complaints than low worriers (median split of PSWQ

scores) [main effect: F(1,27) = 7.62, p<.05], but this difference was

larger in the ACC and in the HR script compared with the R script,

F(1,27) = 7.02 and 8.55, p<05 and <.01, respectively [interaction

effect: F(1.77;47.72) = 4.07, p<.05]. Within the group of high

worriers, more hyperventilation complaints were reported during the HR

script than during the R and the ACC script, F(1,27) = 31.16 and 9.72,

respectively, p's<.01; and more hyperventilation complaints were

reported in the ACC than in the R script, F(1,27) = 7.07, p<.05.

Within the group of low worriers, more hyperventilation complaints

were reported in the HR compared with the R script, F(1,27) = 4.47,

p<.05, but not compared with the ACC script (ns). There were no

significant differences between the ACC script and the R script (ns)

in this group (Fig. 1).

 

High worriers reported overall more additional complaints, F(1,27) =

10.4, p<.01, had higher NA scores, F(1,28) = 10.53, p<.01, and lower

PA scores, F(1,28) = 6.48, p<.05, than low worriers.

 

Acceptance An accepting attitude towards CFS (based on a median split

of ACFT scores) had no effects on the reporting of complaints, nor on

the PANAS scores during the experiment.

 

Physiological data

 

Physiological data of four patients were lost because of equipment

failure. The PetCO_2 values of the remaining 26 patients were analyzed.

 

Baseline data Mean PetCO_2 at the start of the experiment was 33.47

mmHg (p/m 3.75). No significant baseline differences were found in

mean PetCO_2 among the three scripts.

 

Type of script Type of script influenced the change scores in mean

PetCO_2 of the imagery phase F(1.54;38.40) = 9.8, p<.01. During the HR

script mean PetCO_2 decreased significantly stronger compared with

baseline than during the R script, F(1,25) = 12.66, p<.01, and the ACC

script, F(1,25) = 14.04, p<.01. There were no significant differences

in change scores between the R script and the ACC script (ns).

 

The course of the mean PetCO_2 over the three consecutive phases of

each script showed an interesting pattern. In the R script, mean

PetCO_2 of patients increased from baseline to the imagery and the

recovery phase [main effect: F(1,68;42,01) = 6.94, p<.01; Tukey test

baseline to recovery: p<.05; imagery to recovery: ns]. In the ACC

script, mean PetCO_2 remained stable (no significant differences)script

contrast, in the HR script mean PetCO_2 was significantly lower during

the recovery than during baseline [main effect: F(1,26;31,52) ¼ 3.55;

p = .06; Tukey: p<.05] (Fig. 2).

 

Correlations

 

Significant positive correlations between the amount of reported

hyperventilation complaints and state NA were found in the ACC (r=.38,

p<.05), and the HR script (r=.74, p<.01), but not in the R script

(r=.27, ns). A significant negative correlation with state PA was

observed in the HR script (r ¼ .37, p ¼ .05). The correlation between

the amount of reported additional complaints and state NA was only

significant for the HR script (r=.53; p<.01). No significant

correlations were found between the amount of reported

hyperventilation or additional complaints and mean PetCO_2. For all

scripts, there was a significant positive correlation between the

score on the ACFT and mean PetCO_2. Finally, we found a significant

negative correlation between similarity with feelings in daily life

and mean PetCO_2 during the imagery phase of the HR script (r=.43; p<.05).

 

Discussion

 

We investigated the possible role of coping in the relationship

between hyperventilation and CFS, using an imagery paradigm. Imagery

of a hostile resistance action set caused a decrease in PetCO_2 as

well as deficient recovery of PetCO_2. Furthermore, more symptoms were

reported during hostile resistance compared with relaxation. In

contrast, fewer symptoms were reported during an action set of

acceptance and the tendency to accept chronic fatigue was positively

related to mean PetCO_2. Although a positive impact of acceptance on

subjective quality of life has been reported earlier (Viane et al.,

2003; Van Damme et al., 2006), the present study is the first to show

a significant positive relationship between acceptance and an

objective physiological response parameter.

 

Overall, our patient group tended to have low resting values of

PetCO_2, which makes them more vulnerable to developing complaints of

hyperventilation. However, despite the script-related differences in

both PetCO_2 and self-reported hyperventilation complaints, it is

unlikely that hyperventilation was the actual cause of the complaints.

First, the maximal difference in PetCO_2 was only about 1 mmHg.

Although statistically significant, it is not clinically significant

as it is not large enough to explain the differences in symptom

reporting between scripts. Second, the changes between scripts were

not confined to hyperventilation complaints, but also concerned

additional complaints, which are not typically related to reduced

PetCO_2. Finally, there was no significant negative correlation

between the amount of reported hyperventilation complaints and mean

PetCO_2 during imagery.

 

In addition, script-related differences in complaints mirrored

differences in state NA perfectly, suggesting that our findings are an

exemplar of the general finding that persons with high negative

affectivity - a tendency to experience negative emotional states -

report more medically unexplained symptoms (Watson & Pennebaker,

1989). The link between NA and elevated symptom reports most likely

reflects the effect of schema-driven processing of interoceptive

information in which affective rather than somatic cues are used to

determine the subjective somatic state. It has been shown that

affective cues, previously associated with symptom episodes, may

automatically trigger elevated symptom reports upon subsequent

confrontations with these cues as a result of learning (Van den Bergh,

Stegen, & Van de Woestijne, 1997, 1998). This leads to reduced

interoceptive accuracy (Bogaerts et al., 2005). Furthermore, the

relation between negative affect and subjective symptoms may be

related to partly shared or overlapping brain areas, subserving

emotional and visceral interoception (Critchley, Mathias, & Dolan, 2001).

 

Our results suggest that occasional hyperventilation may occur in CFS

patients, especially in conditions of hostile resistance. Subsequent

engagement in this type of action set may provide affective cues

triggering a subjective experience of hyperventilation complaints as a

learned response in the absence of hypocapnia. Given the similarity

between hyperventilation and CFS complaints, these elevated symptom

episodes may be experienced by the patient as additional evidence for

the poor prognosis and stimulate related illness behavior, such as

prolonged inactivity leading to physical deconditioning (Sharpe,

Hawton, Seagroatt, & Pasvol, 1992).

 

Another interesting finding was that, for the relaxation and the

acceptance script, PetCO_2 tended to return to baseline level after

imagery, whereas for the hostile resistance script, a further decrease

in PetCO_2 occurred. This deficient recovery of PetCO_2 after imagery

of hostile resistance in CFS patients is quite remarkable, because

previous imagery studies in our group, using relaxation and

fear-inducing scripts, found normal recovery of PetCO_2 to baseline

level in normals, even after a significant decrease in PetCO_2 during

imagery of the fear script (Van Diest et al., 2001). Delayed recovery

of PCO_2 has previously been found after voluntary hyperventilation

induction in patients with chronic hyperventilation syndrome and panic

disorder patients (Han et al., 1997; Wilhelm, Gerlach, & Roth, 2001).

Their slow recovery was not specific to the respiratory system, but

also applied to autonomic and self-report measures. Our findings add

to this that the deficient recovery of PetCO_2 in CFS patients occurs

when breathing spontaneously, without a mouthpiece and without

preceding forced changes in the breathing pattern, and it only

occurred in specific conditions, namely when imagery induced major

increases in negative affect.

 

It is currently not clear how to account for this observation in CFS

patients. It either points to breathing regulation problems in CFS,

comparable to those found in panic and hyperventilation patients, or

it points to the role of cognitive processes prolonging the effects of

imagining the hostile resistance script. For example, CFS patients

have been shown to have a strong focus on internal states (Wood,

Bentall, Gopfert, & Edwards, 1991). Previous research has also shown

an association between NA and a decreased ability to shift to a new

focus (Compton, 2000). The deficient recovery in the hostile

resistance script might suggest that CFS patients have more difficulty

disengaging attention from minor bodily sensations, resulting in a

less adaptive response to stress (Hoehn-Saric & McLeod, 2000).

 

The tendency to worry had a negative moderating influence on symptom

reporting. Our findings endorse research with chronic pain patients

providing evidence that worrying has a negative impact on complaints

and experienced pain (Aldrich, Eccleston, & Crombez, 2000).

 

This study has some limitations. First, our sample was confined to

women only. Despite CFS being more prevalent in women than in men

(Jason et al., 1999), it would be interesting to know whether our

findings generalize to men. Gender-related differences exist in

symptom reporting (Gijsbers van Wijk, Huisman, & Kolk, 1999), symptom

perception processes (Roberts & Pennebaker, 1995), and in stress

physiology (Taylor et al., 2000). Secondly, our patient group was

treatment-seeking and had not yet received behavioral interventions.

Results from these patients may not generalize to

non-treatment-non-treatment-<WBR>seekers, or patients at post- treatment

experiment no independent control group was used. However, one of the

problems in research comparing acceptance as a general attitude

between different groups is that it may covary with, e.g.,

self-efficacy or a wide range of other patient characteristics that

are hard to control. The strength of the present study design is that

scripts were used that were emotionally relevant to CFS patients to

induce different attitudes within one and the same person. Finally,

both action sets of 'acceptance' and 'hostile resistance' may be

correlated with a whole range of other psychological processes, such

as positive, or negative/hostile thinking, respectively. Defining more

precisely which psychological processes during both attitudinal sets

are exactly responsible for the observed effects is an important focus

for future research.

 

In summary, CFS patients adopting an action set of hostile resistance

towards their illness report more negative affect, more subjective

complaints, and tend to hyperventilate, which may last and aggravate

beyond the duration of actively adopting this action set. Conversely,

adopting an action set of acceptance is associated with less negative

affect, less subjective complaints, and no hyperventilation. Our

results suggest that the promotion of acceptance as a coping strategy

may have good additive value to the existing revalidation program,

which currently consists of traditional cognitive behavioral therapy

and graded exercises.

 

Acknowledgment

 

The first author is supported by the Research Foundation - Flanders

(FWO-Vlaanderen)(

 

Note

 

1 The first 30 s of the scripts contained a description of the

situation (visit vs. store), whereas the last 30 s focused explicitly

on the coping style (HR vs. ACC).

 

Figure captions

 

Fig. 1.

Effect of worrying on the reporting of hyperventilation complaints.

 

Fig. 2.

Mean PetCO_2 in the different phases of each script.

 

Tables

 

Table 1. Mean and SD for valence, arousal, dominance, vividness,

ability to

concentrate, and similarity to feelings in daily life (N=30)

-------------------------

R Acc HR

-------------------------

Valence

M 2.8^a 5.17^b 7.10^c

SD 1.92 2.2 1.47

Arousal

M 7.53^a 6.5^b 4.77^c

SD 1.74 1.91 2.01

Dominance

M 7.17^a 5.87^b 4.60^c

SD 2.09 2.69 2.06

Vividness

M 6.47^a 6.63^a 6.57^a

SD 1.96 1.61 1.52

Concentration

M 63.30^a 65.67^a 65.17^a

SD 23.96 22.08 23.02

Similarity

M 6.03^a 5.97^a 6.3a

SD 1.9 1.79 1.93

-------------------------

Notes: R = relaxation; Acc = acceptance; and HR = hostile resistance.

Low values represent imageries with positive valence, high arousal, low

dominance, low vividness, low ability to concentrate on the script, and

little similarity to feelings in daily life.

Means with the same superscripts are not significantly different (p<.05).

 

Table 2. Mean and SD for hyperventilation complaints, additional

complaints,

NA, and PA (N=30)

-------------------------

R Acc HR (F,df)

-------------------------

Hyperventilation complaints

M 19.03^a 21.07^b 23.93^c

SD 6.01 6.39 9.48

(13.39;1.73)(1

Additional complaints

M 36.28^a 37.03^a 39.00^b

SD 11.25 11.11 12.98 (3.42;1.95)*

NA

M 12.57^a 17.27^b 20.80^c

SD 4.99 7.04 8.09

(28.81;1.92)(2

PA

M 20.17^a 19.97^a 17.23^b

SD 5.27 5.56 4.35 (6.43;1.72)*S

-------------------------

Notes: R = relaxation; Acc = acceptance; and HR = hostile resistance.

Means with different superscripts are significantly different at p<.05.

*p<.05; **p<.01.

 

Appendix A. Supplementary materials

 

Supplementary data associated with this article can be found in the online

version at doi:10.1016/version at version

 

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