The experience of psychosomatic symptoms in the hyperventilation provocation test and in non-hyperventilation tasks

Learning to have psychosomatic complaints: conditioning of respiratory behavior and somatic complaints in psychosomatic patients

OBJECTIVE

Assuming a subjective similarity between the experience of a hyperventilation episode and inhaling CO2-enriched air, we tested whether a respiratory challenge in association with a particular stimulus could result in altered respiratory behavior and associated somatic complaints upon presenting the stimulus only.

METHOD

Psychosomatic patients (N = 28) reporting hyperventilation complaints participated in a differential conditioning paradigm using odors with a positive or negative valence as conditioned stimuli (CS+ or CS-) and 7.4% CO2-enriched air as the unconditioned stimulus (US). Three CS+ and three CS-acquisition trials were run. During the test phase, two CS(+)- and two CS(-)-only trials were run, followed by two new test odors (with a positive or negative valence). Respiratory frequency, tidal volume, end-tidal fractional concentration of CO2, and heart rate were measured throughout the experiment. Somatic complaints were registered after each trial.

RESULTS

We observed a) increased respiratory frequency and an elevated level of somatic complaints upon presenting the CS+ only; b) a selective association effect: conditioning was only apparent with the negatively valenced CS+ odor; (c) no generalization of respiratory responses and complaints to the new odors; (d) no conditioning effect on dummy complaints that are usually not reported when inhaling CO2; (e) in exploratory comparisons with normal subjects, stronger conditioning effects on typical hyperventilation complaints in patients, and, in female subjects, on respiratory frequency.

CONCLUSION

Respiratory responses and psychosomatic complaints can be elicited by conditioned stimuli in a highly specific way. The findings are relevant for disorders in which respiratory abnormalities and/or psychosomatic complaints may play a role and for multiple chemical sensitivity.

The low specificity of the Hyperventilation Provocation Test

The Hyperventilation Provocation Test (HVPT) has become a routine procedure in the diagnosis of hyperventilation syndrome (HVS). During an HVPT the patient voluntarily overbreathes for several minutes to produce hypocapnia. The test is considered positive if the induced symptoms are recognized by the patient as similar to those experienced in daily life. The present study tests the assumption that hypocapnia is the primary trigger for symptoms during an HVPT. In a randomized double-blind crossover design. 115 patients suspected of HVS and 40 healthy controls performed an HVPT and a placebo test (PT, isocapnic overbreathing). The HVPT induced more symptoms than the PT, especially more neuromuscular symptoms, cerebral symptoms, paresthesias, and temperature sensations. However, the absolute difference between the number of symptoms induced by the HVPT and PT was small. In patients, the PT induced 66% of symptoms induced by the HVPT. In the control group this percentage was 60%. The low specificity of the HVPT implies that symptom recognition during the HVPT is invalid as a diagnostic criterion for HVS.

Double-blind placebo-controlled study of the hyperventilation provocation test and the validity of the hyperventilation syndrome

BACKGROUND

Hyperventilation syndrome (HVS) describes a set of somatic and psychological symptoms thought to result from episodic or chronic hyperventilation. Recognition of symptoms during the hyperventilation provocation test (HVPT) is the most widely used criterion for diagnosis of HVS. We have investigated the validity of the HVPT and of the concept of HVS.

METHODS

In a randomised, double-blind, crossover design, the ability of 115 patients with suspected HVS to recognise symptoms during the HVPT was compared with the ability to recognise symptoms during a placebo test (isocapnic overbreathing, with carbon dioxide levels maintained by manual titration). 30 patients who had positive results on the HVPT underwent ambulatory transcutaneous monitoring of pCO2 to ascertain whether they hyperventilated during spontaneous symptom attacks.

FINDINGS

Of the 115 patients who underwent the HVPT and the placebo test, 85 (74%) reported symptom recognition during the HVPT (positive diagnosis HVS). Of that subset, 56 were also positive on the placebo test (false-positive), and 29 were negative on the placebo test (true-positive). False-positive and true-positive patients did not differ in symptom profile or in physiological variables. During ambulatory monitoring (15 true-positive, 15 false-positive) 22 attacks were registered. Transcutaneous end-tidal, pCO2 decreased during only seven. The decreases were slight and apparently followed the onset of the attack, which suggests that hyperventilation is a consequence rather than a cause of the attack. There were no apparent differences between false-positive and true-positive patients.

INTERPRETATION

The HVPT is invalid as a diagnostic test for HVS. Hyperventilation seems a negligible factor in the experience of spontaneous symptoms. The term HVS should be avoided.

Voluntary hyperventilation: the influence of duration and depth on the development of symptoms

Hyperventilation is considered an important factor in the development of somatic symptoms or even panic attacks, though its role has recently been disputed. Arguments are often based on findings from the so-called Hyperventilation Provocation Test (HVPT), which is a procedure consisting of voluntarily overbreathing. The HVPT has been widely used for diagnosing Hyperventilation Syndrome and for experimentally eliciting panic attacks. Almost no attention, however, has been paid to standardizing the test and determining critical values with respect to depth and duration of hyperventilation. In the present study, symptom development was examined in 16 healthy subjects who underwent four HVPTs that differed in depth of hyperventilation (end-tidal PCO2 < 2.4 kPa or < 1.9 kPa), as well as duration of hyperventilation (2 or 5 min). Both depth and duration appeared to have an independent effect on the development of symptoms. In the 5-min condition, symptoms appeared mainly within the first 3 min. To be sure that the HVPT is long enough and deep enough to elicit symptoms in most people, a minimum duration of 3 min is advised, with end-tidal PCO2 decreasing to at least 1.9 kPa or dropping well over 50% of baseline.

Effects of high and low anxiety provoking instructions on the responses to the hyperventilation provocation test

This study examined the effect of high and low anxiety provoking instructions in subjects submitted to a Hyperventilation Provocation Test (HVPT). Subjects were 43 out-patients referred to our clinic for a diagnostic examination of Hyperventilation Syndrome (HVS). Results showed that anxiety levels were affected by the instruction manipulation, but the magnitude of this effect was less than expected and the instruction manipulation had no effect on intensity arid type of reproduced symptoms, nor on symptom recognition. Subjects who met Diagnostic and Statistical manual of Mental Disorders (3rd ed., rev,; American Psychiatric Association, 1987) criteria for Panic Disorder (PD) were not more responsive to the instruction manipulation than non-PD patients. It is argued that the small effect of the manipulation is probably not due to the solidity of the HVPT but to the pervasiveness of pretest cognitions and expectations. In line with this, the report of HVS symptoms appeared highly related to psychological trait measures like anxiety, fear of bodily sensations, and a general tendency to report somatic symptoms.

Respiration in psychophysiology: methods and applications

With the use of advanced equipment, respiratory measures can unobtrusively and reliably be assessed in a variety of psychophysiological research settings. New computerized analysis techniques can break down respiration into a number of components that provide valid estimates of variations in respiratory control mechanisms in the brain stem. Thus analysed, respiratory responses may vary in at least two dimensions: (A) with regard to drive and timing aspects, and (B) with regard to the metabolic appropriateness of the respiratory response. Assessment of respiratory responses may be relevant for a broad variety of research areas, including studies of the physiological effects of mental load and stress, investigations of physiological correlates of emotions and affect, and research linking physiological responses to subjective distress and psychosomatic disorders.

Symptom reporting during voluntary hyperventilation and mental load: implications for diagnosing hyperventilation syndrome

Hyperventilation is considered an important factor in the production of a variety of somatic symptoms. This complex of symptoms is called the Hyperventilation Syndrome (HVS). Recognition of symptoms during the hyperventilation provocation test (HVPT) is a widely used criterion for diagnosing HVS. The validity of this criterion is tested in the present study. Twenty-three patients suspected of HVS performed a HVPT (hyperventilation during 3 min) and a mental load task (Stroop Color Word Test; CWT). It appeared that about the same number of patients (61%) recognized symptoms during the HVPT as during the CWT (52%), despite severe hypocapnia in the first test and normocapnia in the second. Reporting of symptoms was significantly related to psychological state and trait measures (SCL-90 and STAI scores) and unrelated to the degree of hypocapnia. These data have far reaching consequences, as they not only undermine the validity of the HVPT, but also question the tenability of the concept of HVS.

The role of psychopathology and gender in respiratory self-regulation

A group of 12 male and 12 female psychiatric patients were recruited among an anxiety-disordered population, and their performance on a respiratory modulation test was compared with that of a matched non-patient sample. Inferior performance was expected in the patient group, and males were expected to show better respiratory modulation than females. Results supported the conclusion that females were less able than males in modulating respiratory muscle behaviour according to requested patterns, and female psychiatric patients showed a relative lack of flexibility in the thorax or abdomen regions or in both trunk levels.

Serious-mindedness and the effect of self-induced respiratory changes upon parietal EEG

The role of serious-mindedness (so-called telic dominance) in regulation of parietal cortex EEG was investigated. Ten telic (serious-minded) and 10 paratelic (playful state-dominant) individuals were selected on the basis of their responses to the Telic Dominance Scale. They all performed instructed breathholding (hypopnea) and excessive breathing (hyperpnea) in counterbalanced order. The paratelic individuals yielded relatively high scores of integral EEG power; theta power was markedly increased in the left hemisphere during hyperpnea, and reduced in the right hemisphere during hypopnea. Both hyperpnea and hypopnea were reported to be more aversive to the paratelic than to the telic subjects, but no group difference in respiratory activity was found. The electrocortical and hedonic tone differences between the groups are discussed in relation to the distinction between the prefrontal (dopamine) activation pathway and frontoparietal (noradrenalin) arousal pathway, as well as in relation to changes in cortical blood flow and proprioceptive feedback.