CO2 inhalation in the treatment of panic attacks

Interoceptive pathways to understand and treat mental health conditions

An increasing recognition that brain and body are dynamically coupled has enriched our scientific understanding of mental health conditions. Peripheral signals interact centrally to influence how we think and feel, generating our sense of the internal condition of the body, a process known as interoception. Disruptions to this interoceptive system may contribute to clinical conditions, including anxiety, depression, and psychosis. After reviewing the nature of interoceptive disturbances in mental health conditions, this review focuses on interoceptive pathways of existing and putative mental health treatments. Emerging clinical interventions may target novel peripheral treatment mechanisms. Future treatment development requires forward- and back-translation to uncover and target specific interoceptive processes in mental health to elucidate their efficacy relative to interventions targeting other factors.

The Implications of the Diving Response in Reducing Panic Symptoms

Increased CO₂ sensitivity is common in panic disorder (PD) patients. Free divers who are known for their exceptional breathing control have lower CO₂ sensitivity due to training effects. This study aimed to investigate the immediate effects of cold facial immersion (CFI), breath holding and CO₂ challenges on panic symptoms. Healthy participants and patients with PD were subjected to four experimental conditions in a randomly assigned order. The four conditions were (a) breath-holding (BH), (b) CFI for 30 s, (c) CO₂ challenge, and (d) CO₂ challenge followed by CFI. Participants completed a battery of psychological measures, and physiological data (heart rate and respiration rate) were collected following each experimental condition. Participants with PD were unable to hold their breath for as long as normal controls; however, this finding was not significant, potentially due to a small sample size. Significant reductions in both physiological and cognitive symptoms of panic were noted in the clinical group following the CFI task. As hypothesized, the CFI task exerted demonstrable anxiolytic effects in the clinical group in this study by reducing heart rate significantly and lessening self-reported symptoms of anxiety and panic. This outcome demonstrates the promise of the CFI task for clinical applications.

Origins and outlook of interoceptive exposure

BACKGROUND AND OBJECTIVES

Interoceptive exposure (IE) is a behavioral intervention that reduces anxiety sensitivity and distress associated with somatic sensations. In this discussion, we describe the history, current applications and additional clinical potential of IE.

METHOD

We review the origins of IE and its historical application to panic disorder, as well as the accumulating evidence for transdiagnostic application to other disorders including post-traumatic stress disorder, social anxiety disorder, specific phobias and physical disorders. Then, we discuss ways in which IE could contribute to the treatment of additional disorders.

RESULTS

IE is well-established in the treatment of panic disorder and increasingly used to target anxiety-provoking physical sensations in other disorders. Research and clinical evidence suggests that anxiety sensitivity is present across a range of disorders, and may actually be one variation on a broader phenomenon of interoceptive sensitivity, or anxiety focused on physical sensations that have been conditioned to unpleasant emotional states. Moreover, somatic symptoms are central to the experience of most emotions and may contribute to avoidant coping, a maintenance factor for disorders of emotion. IE has potential as a transdiagnostic intervention targeting interoceptive sensitivity in disorders such as depression and eating disorders. Nevertheless, IE is underutilized by clinicians in practice. Recent research in inhibitory learning and extinction suggests strategies for maximizing the effectiveness of IE.

LIMITATIONS

This review is not exhaustive in nature, and systematic research on transdiagnostic applications of IE remains scarce.

CONCLUSIONS

IE is a potentially powerful yet understudied transdiagnostic intervention.

Evidence for distinct genetic effects associated with response to 35% CO₂

BACKGROUND

Carbon dioxide (CO2 ) hypersensitivity represents an individual difference response to breathing CO2 enriched air. People with a history of panic attacks or panic disorder are particularly prone to anxious response, suggesting that CO2 hypersensitivity is a robust risk marker of panic spectrum vulnerability.

METHODS

Twin pairs (n = 346) from the general population-based Norwegian NIPH Mental Health Study completed a measure of anxiety before and after vital capacity inhalation of 35% CO2 air and before and after inhalation of regular air. Three hypotheses regarding genetic factors for CO2 hypersensitivity were examined: (1) a single set of genetic risk factors impacts anxiety before exposure to CO2 and these same genes constitute the only genetic influences on anxiety in response to CO2 , (2) the genetic effects on pre-CO2 anxiety are entirely different from the genetic effects on anxiety in response to exposure to CO2 (i.e., new genetic effects), and (3) pre-CO2 anxiety influences anxiety in response to CO2 as well as unique genetic factors that become activated by respiratory stimulation.

RESULTS

Our results support the latter hypothesis for response to 35% CO2 , with additive genetic and unique environmental factors best fitting the data. Evidence of new genetic effects was observed, accounting for 20% unique variance in post 35% CO2 anxiety response. New genetic effects were not observed for anxiety ratings made post regular air where only preregular air anxiety ratings explained significant variance in this outcome.

CONCLUSIONS

These data suggest that there are distinct genetic factors associated with responsivity to respiratory stimulation via 35% CO2 .

Sex differences in salivary cortisol in response to acute stressors among healthy participants, in recreational or pathological gamblers, and in those with posttraumatic stress disorder

Sex differences in incidence and severity of some stress-related, neuropsychiatric disorders are often reported to favor men, suggesting that women may be more vulnerable to aberrant hypothalamic-pituitary-adrenal (HPA) axis responses to stress. In this review, we discuss several investigations that we, and others, have conducted assessing salivary cortisol as a measure of HPA function. We have examined basal cortisol among healthy men and women and also following acute exposure to stressors. Among healthy participants, men had higher basal cortisol levels than did women. In response to acute stressors, such as carbon dioxide or noise, respectively, cortisol levels were comparable between men and women or higher among women. We have also examined cortisol levels among those with problem eating, gambling, or posttraumatic stress disorder (PTSD). Women with restrained eating habits have higher basal cortisol levels than do women without restrained eating habits. Pathological gamblers have more aberrant stress response to gambling stimuli than do recreational gamblers, and these effects are more prominent among men than women. Men who have motor vehicle accident related PTSD, demonstrate more aberrant cortisol function, than do their female counterparts. Although these sex differences in cortisol seem to vary with type of stress exposure and/or pathophysiological status of the individual, other hormones may influence cortisol response. To address this, cortisol levels among boys and girls with different stress-related experiences, will be the subject of future investigation.

Mechanisms of change in cognitive therapy for panic disorder with agoraphobia

The purpose of this study was to test the predictions of an integrated cognitive and behavioral model of agoraphobic avoidance in patients with chronic panic disorder and agoraphobia during the process of observed therapeutic change. Treatment was residential with the majority (n=165, 88%) receiving cognitive therapy, while the remaining 23 (12%) received guided mastery therapy. The results of latent variable path modeling of the changes occurring over the course of this treatment suggested that the anxiety elicited by bodily sensations influenced catastrophic beliefs, which, in turn, increased avoidance. Avoidance increased the anxiety elicited by bodily sensations.

A genetic study of the acute anxious response to carbon dioxide stimulation in man

People with panic disorder-agoraphobia and their relatives often react anxiously to CO(2)-enriched gas mixtures. Available data are not suited to disentangle genetic from common environmental causes of familial aggregation of CO(2) reactivity, nor provide quantitative estimations of the sources of trait variation. Three-hundred-forty-six twin pairs belonging to the general population-based Norwegian NIPH Mental Health Study underwent self-assessments of anxiety and of DSM-IV panic symptoms after inhalation of a 35%CO(2)-65%O(2) mixture. Two thresholds were employed - at sample's 75th and 90th percentiles of responses - to define provoked panic attacks and to calculate polychoric correlations. Variance components were estimated by structural equation modelling (SEM). For definitions of responses based on the sum of all 13 panic symptoms, SEM could not discriminate between shared environmental versus genetic causes of familial resemblance for provoked attacks. For definitions of responses based on global anxiety, or on the sums of those symptoms (dyspnea, dizziness, palpitations) with highest variance post-CO(2), the best-fitting models indicated additive genetic factors as the sole causes for within-family resemblance. Best-fit heritability estimates ranged from 0.42 to 0.57. Genetic and idiosyncratic environmental factors explain most of individual differences in reactivity to hypercapnia. Within-family similarities for this trait are largely explained by genetic determinants.

Anxiety and panic: from human studies to animal research and back

The role of learning and conditioning varies across human anxiety disorders, and distinguishing between fear and panic is important to guide investigation in panic disorder. By reminding that some psychological and psychobiological theories view panic attacks as false alarms of unconditioned biological origin, we suggest that employing endophenotypes of biological and evolutionary relevance--such as the respiratory responses to suffocative stimuli--can be fruitful for both human research and animal models of panic, and can help keeping unconditioned components of the clinical picture separate from the conditioned components in the experimental setting. We present a review of a model of panic disorder by which idiosyncratic environmental adverse events can promote unconditioned and unexpected spells of physical alarm. Along the proposed causal pathway the alternative splicing expression of polymorphic genes of the cholinergic system play an important role. The overproduction of the Acetylcholinesterase readthrough splice variant after minor stress can promote passive avoidance and learning through action at the level of the corticolimbic circuitries, as well as heightened sensitivity to suffocative stimuli by action upon the cholinergic components of chemoception. When a component of anticipatory anxiety complicates the clinical picture of recurrent panic attacks, and the HPA becomes activated, the glucocorticoid response element 17 kb upstream of the Acetylcholinesterase gene transcription initiation site may sustain sensitivity to suffocative stimuli for prolonged time. Finally, we review how animal models of human panic based on unconditioned provocation of alarm reactions by the same respiratory panicogens that are employed in man are viable and promising.

The effects of anxious responding on mental arithmetic and lexical decision task performance

Anxiety-related responding and skill deficits historically are associated with performance-based problems such as mathematics anxiety, yet the relative contribution of these variables to substandard performance remains poorly understood. Utilizing a 7% carbon dioxide (CO2) gas to induce anxiety, the present study examined the impact of anxious responding on two performance tasks, mental arithmetic and lexical decision. Independent variables included math anxiety group, gender, and gas condition. Dependent variables included task performance and physiological and self-report indices of anxiety. A total of 64 university undergraduate students participated. Physiological and verbal-report measures of anxiety supported the utility of 7% carbon dioxide-enriched air as an anxiety-inducing stimulus. Behavioral disruption on performance tasks, however, did not differ as a function of carbon dioxide inhalation. Performance did differ as a function of math anxiety. High math anxious individuals generally exhibited higher error rates on mathematical tasks, particularly on tasks designed to measure advanced math skill and those requiring working memory resources. These findings are discussed with reference to processing efficiency theory, discordance among anxiety response systems, and the intricacies associated with skill measurement.

Beyond the usual suspects: a cholinergic route for panic attacks

For unknown reasons and through poorly understood mechanisms, people at risk of panic attacks are hypersensitive to suffocative stimuli and experience hyperventilation and anxiety after exposure to heightened concentrations of carbon dioxide. Similarly to the physiological reflex response to hypercapnia in animals and man, the anxious response to carbon dioxide in people with panic disorder is at least partially controlled by the central muscarinic receptors. It is suggested here that some modifications of the cholinergic functions could underlie human individual differences in carbon dioxide sensitivity and proneness to experience panic attacks. The hypothesis is based upon experimental evidence that stressful and potentially harmful stimuli prime relatively long-lasting changes in cholinergic genes expression and cholinergic receptors' regulation. The adaptive sequels of these modifications include protection of the brain from overstimulation, and, at the level of the corticolimbic circuitries, promotion of passive avoidance and learning after stress. The extension of the same modifications to the cholinergic receptors involved in chemoception, however, could lower the threshold for reaction to suffocative stimuli, including carbon dioxide. The exaggerated sensitivity to carbon dioxide observed in humans suffering from panic attacks could then be thought of as an evolutionary cost of the involvement of the cholinergic system in shaping otherwise adaptive responses to stress and threatening stimuli.

Influence of the serotonin antagonist, metergoline, on the anxiogenic effects of carbon dioxide, and on heart rate and neuroendocrine measures, in healthy volunteers

The mechanism of action of carbon dioxide (CO(2)) angiogenesis is unknown; only recently have possible serotonergic (5-HT) influences begun to be studied. In separate double-blind challenges 1 week apart, 14 healthy volunteers received two vital capacity inhalations each of 35% CO(2) and of air, once after a single capsule of placebo and once after a single capsule containing 4 mg of the 5-HT antagonist metergoline in a randomized crossover design. The inhalations were repeated 1 and 2 days after the ingestion of capsules, to investigate possible delayed effects of metergoline, and possible tolerance to repeated CO(2) after placebo. We observed increased anxiety, and a trend for increased plasma noradrenaline (NA), after CO(2). CO(2) anxiogenesis was significantly enhanced by metergoline. Heart rate increased after both gas mixtures following metergoline administration. Plasma prolactin levels were lower after metergoline. Responses to CO(2) did not differ between the day of placebo administration and the two subsequent days; on the days following metergoline administration there were almost no delayed effects. We hypothesize that 5-HT may function as an inhibitor of CO(2) anxiogenesis, and that this is opposed by the 5-HT antagonist, metergoline. Absence of tolerance after repeated CO(2) argues against psychological explanations of tolerance after other panicogens. Copyright 2001 John Wiley & Sons, Ltd.

Anxiogenic effects of repeated administrations of 20% CO2-enriched air: stability within sessions and habituation across time

Increasingly carbon dioxide-enriched air is being used as an aversive unconditioned stimulus in laboratory examinations of anxiety. Yet, little is known about the stability of the autonomic and subjective effects of this stimulus across repeated inhalations and sessions. We examined whether repeated administrations of high concentrations of CO2-enriched air produced either habituation, stability, or sensitization across several autonomic and self-report indices within one session (Experiment 1) and then several sessions (Experiment 2) of exposure. Results suggest that non-clinical participants do not habituate to CO2 within sessions, but do show habituation on cardiac and subjective report of anxiety across sessions. Individual difference factors such as anxiety sensitivity and suffocation fear seem to moderate some of these effects, including self-reported distress and anxiety in response to the challenge. These results support the use of CO2 as a panicogenic aversive stimulus in laboratory models of fear onset and in clinical settings for interoceptive exposure treatments of panic.

The 35% CO2 inhalation procedure: test-retest reliability

The subjective response to a single-breath, 35% carbon dioxide challenge test shows promise as a tool for the study of panic disorder and may comprise a trait marker for that disorder. Little has been done to measure the reliability of test results, however. Subjects took a single breath at 35% CO2 and completed a self-rating of anxiety symptoms immediately thereafter. This procedure was repeated after a mean interval of 29 days. One group, considered at high risk for panic disorder, consisted of well, first-degree relatives of individuals treated for panic disorder. The control group included well subjects at high risk for affective disorder and subjects who had family histories negative for both affective disorder and panic disorder. On both testing occasions, subjects at high risk for panic disorder had symptom scores that were significantly higher than those of control subjects. Group differences in the portions who experienced a panic attack were dependent on the symptom threshold used to define an attack. A lower threshold was optimal with the second testing and a single, positive test result appeared to be more meaningful than a single negative result. The majority of individual symptom ratings were highly correlated across tests. Ratings for "smothering sensations," in particular, correlated highly across tests and consistently discriminated high-risk from control subjects. The sources of test result variability are unclear and warrant more investigation before the tests can be clinically useful. Research efforts should seek optimal thresholds to define positive test results within given data sets.

How does interoceptive exposure for panic disorder work? An uncontrolled case study

To examine the influence of interoceptive exposure (IE) when used alone in the treatment of Panic Disorder (PD), 17 PD patients were presented with six IE sessions, using 35% CO2 as the exposure medium. The data indicate that IE alone is effective in reducing panic, panic-related fears, and general anxiety. However, the positive effects of IE do not appear to extend to agoraphobia, related fears, or depressed mood. Two distinct within-session patterns of fear response to IE were noted, one indicating habituation and the other indicating a lack of fear reduction. Although both patterns were associated with reductions in panic and anxiety following IE, the Habituators appeared to have a more positive outcome, which occurred more rapidly. These data suggest that IE may operate via two different pathways. Implications for understanding fear reduction are discussed, along with directions for future study.

Hypersensitivity to carbon dioxide as a disease-specific trait marker

There is now substantial evidence that an abnormal threshold for suffocation alarm underlies panic disorder. Because this disorder is highly familial, evidence of an abnormal suffocation threshold may be apparent in high-risk individuals before they develop clinical illness. To explore this possibility, we used a single inhalation of 35% CO2 vs. air to evaluate 11 subjects who had at least one first-degree relative with DSM-III-R panic disorder, 13 who had at least two relatives treated for mania or for depression (HR-AD), and 15 low-risk controls who had no family history of panic disorder, affective disorder, or alcoholism (LR-C). All were aged 18-34 and had no history of panics or of any Research Diagnostic Criteria disorder. Five (45.5%) of the subjects at high risk for panic disorder, but none of the LR-C subjects (p = .007), nor any of the HR-AD subjects (p = .011), developed a panic attack following inhalation of the CO2 mixture.

Daily administration of m-chlorophenylpiperazine to healthy human volunteers rapidly attenuates many of its behavioral, hormonal, cardiovascular and temperature effects

The serotonergic agent meta-chlorophenylpiperazine (m-CPP) increases temperature and plasma ACTH and other hormones and decreases social interaction, locomotor activity and food intake in rats, most likely via stimulation of 5-HT2C receptors. Repeated daily administration of m-CPP to rats induces rapid tolerance to these effects of m-CPP. As m-CPP has been used in challenge tests and in preliminary treatment trials in humans, we evaluated the possible development of tolerance to m-CPP in ten healthy human volunteers using a double-blind, random assignment crossover study of placebo versus daily m-CPP infusions. Psychological and physical symptoms of anxiety, temperature, pupil size, diastolic blood pressure, and plasma ACTH, cortisol, and prolactin concentrations were increased by the first administration of m-CPP (0.08 mg/kg) compared to placebo. All of these responses were attenuated on m-CPP days 2 and 3. Plasma m-CPP levels did not differ across the 3 m-CPP days. Repeated m-CPP administration thus appears to induce rapid tolerance to its behavioral and physiological effects in humans. Further investigations of the mechanisms involved in the development of subsensitivity to m-CPP may contribute to increased understanding of the regulation of serotonin-mediated functions and of anxiety disorders.

Fearful responding to repeated CO2 inhalation: a preliminary investigation

In an effort to explore factors which maintain fear of physical sensations, repeated administration of 35% CO2 was used with college students scoring high and low on the Anxiety Sensitivity Index. Half of each group was administered 12 CO2 trials, while the other half received 9 CO2 trials, followed by a dishabituation trial (Trial 10) and 2 more CO2 administrations (Trials 11 and 12). Measures included subjective anxiety, heart rate, skin conductance, and number of panic symptoms reported. Results indicated a nonsignificant trend for the High ASI group to show increased pre-inhalation anxiety across trials, while the Low ASI group showed a rapid reduction in pre-inhalation anxiety. Post-inhalation skin conductance mirrored this pattern, although rapid reduction in post-inhalation heart rate was observed. Overall, the High ASI participants showed a notable lack of fear reduction across trials. Results are discussed in light of sensitization as a factor contributing to anticipatory anxiety, with implications for understanding the etiology and maintenance of Panic Disorder.

Exposure versus cognitive restructuring in the treatment of panic disorder with agoraphobia

The aim of this study was to assess the rate of change on clinical, behavioral and cognitive variables during exposure therapy and cognitive restructuring in the treatment of panic disorder with agoraphobia. A total of 28 Ss who received a diagnosis of panic disorder with agoraphobia were randomly assigned to either of two treatment conditions: exposure therapy or cognitive restructuring. Treatment conditions were kept as distinct as possible from each other. Subjects were assessed on five occasions: pretreatment, after 5, 10, and 15 (posttreatment) sessions of treatment and at a 6-month follow-up. Analyses of outcome data revealed strong and significant time effects on all measures. However, no group x time interaction reached statistical significance, suggesting that both strategies operate at the same pace. Furthermore, power analyses suggest that any difference that might exist in the rate of improvement between exposure and cognitive restructuring in the treatment of panic disorder with agoraphobia is marginal.

A breathing-retraining procedure in treatment of sleep-onset insomnia: theoretical basis and experimental findings

Increase in CO2 has a sedative effect upon the central nervous system, and the beginning of sleep coincides with modifications in breathing, decrease in ventilation, and in pCO2 increase. In this paper is described a technique of breathing that is useful in producing drowsiness in a very short time. 46 insomniacs were randomly allocated to either a treatment or control condition. In the former, patients were trained in the breathing process. The control group was taught no breathing process. Latencies to sleep for the insomniacs confirmed that the breathing process was useful in producing drowsiness. Theoretical bases are discussed.

Applied relaxation vs cognitive behavior therapy in the treatment of panic disorder

The present study investigated the efficacy of a coping-technique, applied relaxation (AR) and cognitive behavior therapy (CBT), in the treatment of panic disorder. Thirty-eight outpatients fulfilling the DSM-III-R criteria for panic disorder with no (n = 30) or mild (n = 8) avoidance were assessed with independent assessor ratings, self-report scales and self-observation of panic attacks before and after treatment, and at a 1-yr follow-up. The patients were treated individually for 12 weekly sessions. The results showed that both treatments yielded very large improvements, which were maintained, or furthered at follow-up. There was no difference between AR and CBT on any measure. The proportion of panic-free patients were 65 and 74% at post-treatment, and 82 and 89% at follow-up, for AR and CBT, respectively. There were no relapses at follow-up, on the contrary 55% of the patients who still had panic attacks at post-treatment were panic-free at follow-up. Besides affecting panic attacks the treatments also yielded marked and lasting changes on generalized anxiety, depression and cognitive misinterpretations. The conclusion that can be drawn is that both AR and CBT are effective treatments for panic disorder without avoidance.

Remedying the Achilles heel of behavior research and therapy: prescriptive matching of intervention and psychopathology

Recent calls for eclecticism in clinical practice have been fueled by the putative limitations of behavioral techniques in treating a variety of psychological problems. However, calls for such integration do not appear to be justified for two related reasons. First, the precise conditions under which behavioral interventions are and are not effective have not yet been adequately delineated. Consequently, rejection of behavioral interventions in favor of relatively indiscriminate application of cognitive strategies is premature. Second, behavior therapy has as its hallmark a thorough grounding in inductive empiricism, while cognitive/dynamic theories are wholly based in deductive rationalism. As a result, wholesale acceptance of alternative theories and techniques by behaviorists is both inconsistent and retrogressive. Cognitive interventions have their place, but only when cognitive distortions have been specifically identified. Therefore, refinement of behavioral treatments into prescriptive interventions is warranted. The parameters of prescriptive behavior therapy are described in this paper.

Situational exposure treatment versus panic control treatment for agoraphobia. A case study

Situational in vivo exposure has been widely used in the treatment of agoraphobia. However, only a low to moderate proportion of individuals treated with this approach have shown a high level of therapeutic gain. The recent recognition of panic as central to the development and maintenance of a great many cases of agoraphobic avoidance suggests that treatments focused directly on panic may contribute to a more comprehensive approach to agoraphobia. The present single case demonstrates that whereas two modes of situational exposure produced only limited improvement an approach focused directly on panic had greater effectiveness. The specific effects of the treatment components within the panic control package are analyzed in detail.

Hyperventilation and panic attacks

The role of hyperventilation in the aetiology of panic attacks is still unclear. This paper briefly reviews the role of hyperventilation and abnormal respiration to panic attacks and examines the experimental evidence. Evidence has been found that physiological variables such as paCO2 and pH are involved in the aetiology of panic attacks and panic disorder but the extent and the nature of the involvement of cognitive variables is undetermined. Based on current evidence, there is a need to integrate cognitive variables with the physiological framework proposed by the hyperventilation theory. Until clear experimental evidence is produced about the relationships between cognitive and physiological factors, the applicability of hyperventilation in the aetiology and treatment of panic attacks remains in question.

A 6-year follow-up of the effectiveness of respiratory retraining, in-situ isometric relaxation, and cognitive modification in the treatment of agoraphobia

A multiple baseline design across behaviors was used with 8 agoraphobics to evaluate respiratory retraining (RR), in-situ isometric relaxation (I IR), cognitive modification (CM), and a placebo treatment, imaginal rehearsal (IR). As hypothesized, RR significantly reduced psychophysiological accomplements of panic, I IR reduced anxiety, and CM reduced cognitive distress. The placebo treatment IR had a moderate but transitory effect. RR was the most effective component, and also reduced panic frequency, catastrophic cognitions. anticipatory anxiety, and behavioral avoidance. I IR also reduced panic frequency. The combined treatment components produced dramatic reductions in situational avoidance and anxiety, free-floating anxiety, panic frequency, and SCL-90R scores. All behavioral measures improved, as did work adjustment and marital satisfaction. These gains were maintained over the 6-year follow-up; however, 7 partial but temporary relapses occurred. The implications of these relapses for both theory and treatment are discussed, together with the role of exposure and anxiety management.

The hyperventilation syndrome in panic disorder, agoraphobia and generalized anxiety disorder

The symptom complex of panic disorder and generalized anxiety disorder suggests an etiological role for hyperventilation. The present study investigates the overlap between DSM-III-R panic disorder, panic disorder with agoraphobia and generalized anxiety disorder with hyperventilation syndrome (HVS). The anxiety disorder diagnoses were based on a structured interview, and HVS syndrome (HVS). The anxiety disorder diagnoses were based on a structured interview, and HVS determined by the so-called hyperventilation provocation test (a brief period of voluntary hyperventilation with recognition of symptoms). The overlap rates with HVS were: 48% for panic disorder, 83% for panic disorder with agoraphobia and 82% for generalized anxiety disorder. However, a pilot study on transcutaneous monitoring of carbon dioxide tension leads us to question the validity of the voluntary hyperventilation method that we used to determine HVS-status. It is unclear whether hyperventilation plays an important role in panic and general anxiety, as our overlap findings suggest. For patients who recognize the symptoms induced by voluntary hyperventilation, the hyperventilation provocation procedure provides a therapeutic means of exposure to feared bodily sensations.

Breathing retraining, exposure and a combination of both, in the treatment of panic disorder with agoraphobia

The present study investigates the differential effectiveness of three treatment packages for agoraphobia. Patients suffering from panic disorder with agoraphobia (DSM-III-R) received one of three treatments: Breathing Retraining with Cognitive Restructuring (BRCR), graded self-exposure in vivo (EXP), or a combination of BRCR and EXP. Treatments consisted of 8 sessions. Assessment consisted of self-report measures for panic, phobic anxiety and avoidance, depression, general anxiety, somatic complaints and fear of body sensations, and of two respiratory measures (respiratory rate and alveolar pCO2). The treatments resulted in a reduction in symptomatology on all self-report measures, except panic frequency, and in a decrease in respiratory rate. There was no evidence for a differential efficacy for any of the treatments on any of the variables. Contrary to expectation, and at odds with findings from earlier studies, BRCR had no significant effect on panic frequency. A detailed comparison of sample characteristics of patients in our study and previous studies, did not yield insight into possible causes for the failure to replicate earlier results. The limited effectiveness of breathing retraining in reducing panic, as observed in the present study, leads us to conclude that the role of hyperventilation in panic is less important than previously thought.

Guided imaginal coping: an integrative treatment for panic disorder

Contemporary models suggest that persons with panic disorder inaccurately attribute somatic anxiety symptoms to catastrophic causes. This consequently exacerbates their physiological symptoms, triggering full-blown panic attacks. Researchers have modified catastrophic thinking using cognitive therapy, but typically have not employed these techniques during actual episodes of heightened arousal. Thus, reported cognitive changes may not generalize to naturalistic situations involving hyperreactivity. This study describes use of an intervention which simultaneously combines symptom exposure and cognitive therapy techniques. The client treated here experienced reductions in panic attack frequency as well as duration and became less depressed as therapy progressed. Discussion addresses potential causal mechanisms and directions for future research.

Effects of laboratory-induced panic-anxiety on subsequent provocative infusions

The effects of infusion-induced panic-anxiety on subsequent pre-infusion anxiety ratings and infusion-induced panic attacks were studied in 64 panic disorder patients, in a double-blind randomized study using sodium lactate, isoproterenol, and placebo infusions. While there was a decrease of preinfusion anxiety from one infusion to the next infusion both for panickers and nonpanickers, there was no evidence of either a significant decrease or an increase in the frequency of subsequent panic attacks. These results suggest that there is neither a desensitizing nor a sensitizing effect of pharmacologically induced panic attacks on subsequent infusions in a serial three-infusion design.

Panic disorder and agoraphobia: fear of fear or fear of the symptoms produced by hyperventilation?

Two versions of the fear-of-fear hypothesis of panic disorder are discussed. The fear-of-the-somatic-effects-of-fear version, which is distinguished from the classical conditioning version, is compared with the hyperventilation theory of panic disorder and agoraphobia. The fear-of-the-somatic-effects-of-fear hypothesis is criticized on the basis of its inability to explain adequately (a) the initiation of panic attacks, (b) the growth in intensity of panic attacks, and (c) the termination of panic attacks. The tenability of the hyperventilation theory is supported by evidence from programs of treatment derived from the basic assumptions of the theory.

Pulmonary carbon dioxide and panic-arousing sensations after 35% carbon dioxide inhalation: hypercapnia/hyperoxia versus hypercapnia/normoxia

Experimental research has demonstrated that CO2 inhalation provides a valid laboratory model for acute panic. Earlier studies employed CO2/O2 mixtures that were not only hypercapnic but also hyperoxic, raising the question of the relative contribution of the hyperoxidity. A comparison between a hypercapnic/hyperoxic mixture (35% CO2/65% O2) and a hypercapnic/normoxic mixture (35% CO2/20% O2/45% N2) revealed no differences on self-reported panic symptoms or end tidal pCO2. It is concluded that findings from previous CO2/O2 inhalation studies should be attributed to the hypercapnic, rather than to the hyperoxic, nature of the mixtures.

CO2 vulnerability in panic disorder

The immediate effects of a single inhalation of a 35% CO2 mixture in oxygen were examined in 12 patients with panic disorders and 11 normal control subjects. Compared to a placebo air inhalation, the CO2 inhalation provoked short-lived autonomic panic symptoms in both patients and normals; it also elicited high subjective anxiety in patients with panic disorders. The latter rated the overall CO2-induced state as very similar to a real-life panic attack.