Language of dyspnea in panic disorder

Panic disorder respiratory subtype: psychopathology and challenge tests - an update

Panic disorder (PD) pathophysiology is very heterogeneous, and the discrimination of distinct subtypes could be very useful. A subtype based on respiratory symptoms is known to constitute a specific subgroup. However, evidence to support the respiratory subtype (RS) as a distinct subgroup of PD with a well-defined phenotype remains controversial. Studies have focused on characterization of the RS based on symptoms and response to CO2. In this line, we described clinical and biological aspects focused on symptomatology and CO2 challenge tests in PD RS. The main symptoms that characterize RS are dyspnea (shortness of breath) and a choking sensation. Moreover, patients with the RS tended to be more responsive to CO2 challenge tests, which triggered more panic attacks in this subgroup. Future studies should focus on discriminating respiratory-related clusters and exploring psychophysiological and neuroimaging outcomes in order to provide robust evidence to confirm RS as a distinct subtype of PD.

Systemic corticosteroids for the management of cancer-related breathlessness (dyspnoea) in adults

BACKGROUND

Dyspnoea is a common symptom in advanced cancer, with a prevalence of up to 70% among patients at end of life. The cause of dyspnoea is often multifactorial, and may cause considerable psychological distress and suffering. Dyspnoea is often undertreated and good symptom control is less frequently achieved in people with dyspnoea than in people with other symptoms of advanced cancer, such as pain and nausea. The exact mechanism of action of corticosteroids in managing dyspnoea is unclear, yet corticosteroids are commonly used in palliative care for a variety of non-specific indications, including pain, nausea, anorexia, fatigue and low mood, despite being associated with a wide range of adverse effects. In view of their widespread use, it is important to seek evidence of the effects of corticosteroids for the management of cancer-related dyspnoea.

OBJECTIVES

To assess the effects of systemic corticosteroids for the management of cancer-related breathlessness (dyspnoea) in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, Science Citation Index Web of Science, Latin America and Caribbean Health Sciences (LILACS) and clinical trial registries, from inception to 25 January 2018.

SELECTION CRITERIA

We included randomised controlled trials that included adults aged 18 years and above. We included participants with cancer-related dyspnoea when randomised to systemic corticosteroids (at any dose) administered for the relief of cancer-related dyspnoea or any other indication, compared to placebo, standard or alternative treatment.

DATA COLLECTION AND ANALYSIS

Five review authors independently assessed trial quality and three extracted data. We used means and standard deviations for each outcome to report the mean difference (MD) with 95% confidence interval (CI). We assessed the risk of bias and quality of evidence using GRADE. We extracted primary outcomes of sensory-perceptual experience of dyspnoea (intensity of dyspnoea), affective distress (quality of dyspnoea) and symptom impact (burden of dyspnoea or impact on function) and secondary outcomes of serious adverse events, participant satisfaction with treatment and participant withdrawal from trial.

MAIN RESULTS

Two studies met the inclusion criteria, enrolling 157 participants (37 participants in one study and 120 in the other study), of whom 114 were included in the analyses. The studies compared oral dexamethasone to placebo, followed by an open-label phase in one study. One study lasted seven days, and the duration of the other study was 15 days.We were unable to conduct many of our predetermined analyses due to different agents, dosages, comparators and outcome measures, routes of drug delivery, measurement scales and time points. Subgroup analysis according to type of cancer was not possible.Primary outcomesWe included two studies (114 participants) with data at one week in the meta-analysis for change in dyspnoea intensity/dyspnoea relief from baseline. Corticosteroid therapy with dexamethasone resulted in an MD of lower dyspnoea intensity compared to placebo at one week (MD -0.85 lower dyspnoea (scale 0-10; lower score = less breathlessness), 95% CI -1.73 to 0.03; very low-quality evidence), although we were uncertain as to whether corticosteroids had an important effect on dyspnoea as results were imprecise. We downgraded the quality of evidence by three levels from high to very low due to very serious study limitations and imprecision.One study measured affective distress (quality of dyspnoea) and results were similar between groups (29 participants; very low-quality evidence). We downgraded the quality of the evidence three times for imprecision, inconsistency, and serious study limitations.Both studies assessed symptom impact (burden of dyspnoea or impact on function) (113 participants; very low-quality evidence). In one study, it was unclear whether dexamethasone had an effect on dyspnoea as results were imprecise. The second study showed more improvement for physical well-being scores at days eight and 15 in the dexamethasone group compared with the control group, but there was no evidence of a difference for FACIT social/family, emotional or functional scales. We downgraded the quality of the evidence three times for imprecision, inconsistency, and serious study limitations.Secondary outcomesDue to the lack of homogenous outcome measures and inconsistency in reporting, we could not perform quantitative analysis for any secondary outcomes. In both studies, the frequency of adverse events was similar between groups, and corticosteroids were generally well tolerated. The withdrawal rates for the two studies were 15% and 36%. Reasons for withdrawal included lost to follow-up, participant or carer (or both) refusal, and death due to disease progression. We downgraded the quality of evidence for these secondary outcomes by three levels from high to very low due to serious study limitations, inconsistency and imprecision.Neither study examined participant satisfaction with treatment.

AUTHORS' CONCLUSIONS

There are few studies assessing the effects of systemic corticosteroids on cancer-related dyspnoea in adults with cancer. We judged the evidence to be of very low quality that neither supported nor refuted corticosteroid use in this population. Further high-quality studies are needed to determine if corticosteroids are efficacious in this setting.

Confounders of severe asthma: diagnoses to consider when asthma symptoms persist despite optimal therapy

Asthma can often be challenging to diagnose especially when patients present with atypical symptoms. Therefore, it is important to have a broad differential diagnosis for asthma to ensure that other conditions are not missed. Clinicians must maintain a high index of suspicion for asthma mimickers, especially when patients fail to respond to conventional therapy. The purpose of this review is to briefly review some of the more common causes of asthma mimickers that clinicians should consider when the diagnosis of asthma is unclear.

The time-course of cortico-limbic neural responses to air hunger

Several studies have mapped brain regions associated with acute dyspnea perception. However, the time-course of brain activity during sustained dyspnea is unknown. Our objective was to determine the time-course of neural activity when dyspnea is sustained. Eight healthy subjects underwent brain blood oxygen level dependent functional magnetic imaging (BOLD-fMRI) during mechanical ventilation with constant mild hypercapnia (∼ 45 mm Hg). Subjects rated dyspnea (air hunger) via visual analog scale (VAS). Tidal volume (V(T)) was alternated every 90 s between high VT (0.96 ± 0.23 L) that provided respiratory comfort (12 ± 6% full scale) and low V(T) (0.48 ± 0.08 L) which evoked air hunger (56 ± 11% full scale). BOLD signal was extracted from a priori brain regions and combined with VAS data to determine air hunger related neural time-course. Air hunger onset was associated with BOLD signal increases that followed two distinct temporal profiles within sub-regions of the anterior insula, anterior cingulate and prefrontal cortices (cortico-limbic circuitry): (1) fast, BOLD signal peak <30s and (2) slow, BOLD signal peak >40s. BOLD signal during air hunger offset followed fast and slow temporal profiles symmetrical, but inverse (signal decreases) to the time-courses of air hunger onset. We conclude that differential cortico-limbic circuit elements have unique contributions to dyspnea sensation over time. We suggest that previously unidentified sub-regions are responsible for either the acute awareness or maintenance of dyspnea. These data enhance interpretation of previous studies and inform hypotheses for future dyspnea research.

Brainstem response to hypercapnia: a symptom provocation study into the pathophysiology of panic disorder

BACKGROUND

The biological basis of uncued panic attacks is not yet understood. An important theory concerning the nature and cause of panic disorder is the 'suffocation false alarm theory'. This alarm is supposed to be over-sensitive in panic disorder patients and can be triggered by CO2. No neurobiological substrate has been identified for such an alarm. The present study investigates differences in brain activation in panic patients, healthy individuals and experienced divers in response to CO2, representing three groups with descending sensitivity to CO2.

METHOD

Brain activation was measured with functional magnetic resonance imaging. Subjects breathed through a mouthpiece delivering a continuous flow of 100% oxygen for two minutes, followed by a hypercapnic gas mixture (7% CO2) for the next two minutes. Statistical analysis was performed using SPM8.

RESULTS

There was a significant main effect of group in response to the CO2. Patients show increased brainstem activation in response to hypercapnia compared to controls and divers. Subjective feelings of breathing discomfort were positively correlated with brain activation in the anterior insula in all groups.

CONCLUSION

This is the first study showing that the behavioural response to CO2 that characterises panic disorder patients is likely due to increased neural sensitivity to CO2 at brainstem level.

Respiratory muscle tension as symptom generator in individuals with high anxiety sensitivity

OBJECTIVE

Anxiety and panic are associated with the experience of a range of bodily symptoms, in particular unpleasant breathing sensations (dyspnea). Respiratory theories of panic disorder have focused on disturbances in blood gas regulation, but respiratory muscle tension as a source of dyspnea has not been considered. We therefore examined the potential of intercostal muscle tension to elicit dyspnea in individuals with high anxiety sensitivity, a risk factor for developing panic disorder.

METHODS

Individuals high and low in anxiety sensitivity (total N=62) completed four tasks: electromyogram biofeedback for tensing intercostal muscle, electromyogram biofeedback for tensing leg muscles, paced breathing at three different speeds, and a fine motor task. Global dyspnea, individual respiratory sensations, nonrespiratory sensations, and discomfort were assessed after each task, whereas respiratory pattern (respiratory inductance plethysmography) and end-tidal carbon dioxide (capnography) were measured continuously.

RESULTS

In individuals with high compared to low anxiety sensitivity, intercostal muscle tension elicited a particularly strong report of obstruction (M=5.1, SD=3.6 versus M=2.5, SD=3.0), air hunger (M=1.9, SD=2.1 versus M=0.4, SD=0.8), hyperventilation symptoms (M=0.6, SD=0.6 versus M=0.1, SD=0.1), and discomfort (M=5.1, SD=3.2 versus M=2.2, SD=2.1) (all p values<.05). This effect was not explained by site-unspecific muscle tension, voluntary manipulation of respiration, or sustained task-related attention. Nonrespiratory control sensations were not significantly affected by tasks (F<1), and respiratory variables did not reflect any specific responding of high-Anxiety Sensitivity Index participants to intercostal muscle tension.

CONCLUSIONS

Respiratory muscle tension may contribute to the respiratory sensations experienced by panic-prone individuals. Theories and treatments for panic disorder should consider this potential source of symptoms.

Panic disorder and the respiratory system: clinical subtype and challenge tests

INTRODUCTION

Respiratory changes are associated with anxiety disorders, particularly panic disorder (PD). The stimulation of respiration in PD patients during panic attacks is well documented in the literature, and a number of abnormalities in respiration, such as enhanced CO2 sensitivity, have been detected in PD patients. Investigators hypothesized that there is a fundamental abnormality in the physiological mechanisms that control breathing in PD.

METHODS

The authors searched for articles regarding the connection between the respiratory system and PD, more specifically papers on respiratory challenges, respiratory subtype, and current mechanistic concepts.

CONCLUSIONS

Recent evidences support the presence of subclinical changes in respiration and other functions related to body homeostasis in PD patients. The fear network, comprising the hippocampus, medial prefrontal cortex, amygdala and its brainstem projections, may be abnormally sensitive in PD patients, and respiratory stimulants like CO2 may trigger panic attacks. Studies indicate that PD patients with dominant respiratory symptoms are particularly sensitive to respiratory tests compared to those who do not manifest dominant respiratory symptoms, representing a distinct subtype. The evidence of changes in several neurochemical systems might be the expression of the complex interaction among brain circuits.

Cardiorespiratory response to physical exercise and psychological variables in panic disorder

OBJECTIVE

To investigate the possible influence of psychological variables on cardiorespiratory responses and perceived exertion of patients with Panic Disorder (PD) during a submaximal exercise test.

METHOD

Ten outpatients with PD and 10 matched healthy subjects walked up on a treadmill slope at a speed of 4 km/h in order to reach 65% of their maximum heart rate. Cardiorespiratory variables were continuously recorded. Before the exercise, the state and trait anxiety (State-Trait Anxiety Inventory scores), fear of physical sensations (Body Sensation Questionnaire scores), and fear of autonomic arousal (Anxiety Sensitivity Index scores) were assessed; during the exercise, levels of anxiety (VAS-A) and exertion (Borg Scale CR 10) were measured.

RESULTS

Compared to controls, patients reached earlier the target HR and the ventilatory threshold, showed lower oxygen consumption, higher HR and lower within-subject standard deviations of HR (a measure of cardiac variability). Exertion was also higher, and there was a significant correlation between breathing frequency, tidal volume and HR. No significant associations were found between cardiorespiratory response, perceived exertion, and psychological variables in patients with PD.

CONCLUSION

Although patients with PD presented poor cardiorespiratory fitness and were required to spend more effort during physical exercise, this did not appear to be related to the psychological variables considered. Further studies with larger groups are warranted.

Hypersensitivity to hypercapnia: definition/(s)

Empirical evidence indicates that panic disorder (PD) patients experience hypersensitivity to hypercapnia, a condition in which the blood level of carbon dioxide exceeds the normal value. The importance of this research line is substantial and indeed, hypercapnic hypersensitivity has been advanced as a possible endophenotype of panic. Definitions of "hypersensitivity," however, have varied. The purpose of this brief review is to delineate and critique different definitions of hypercapnic hypersensitivity. Several definitions - panic attack rate, panic symptoms including dyspnea, subjective anxiety, and respiratory disturbance - are explored. The review concludes that although no ideal definition has emerged, marked anxiety post-hypercapnia has substantial support as a putative trait marker of PD. The term "subjective hypersensitivity" (Coryell et al., 2001) is re-introduced to denote pronounced anxiety post-hypercapnia and recommended for use along with its previous definition: increased self-reported anxiety measured on a continuous visual analog scale, already widely in use. Due to the well-established link between panic and respiration, definitional candidates focusing on aberrant respiratory response - less investigated as trait markers of PD in high risk studies - warrant scrutiny as well. Several reasons why definitional clarity might be beneficial are presented, along with ideas for future research.

An official American Thoracic Society statement: update on the mechanisms, assessment, and management of dyspnea

BACKGROUND

Dyspnea is a common, distressing symptom of cardiopulmonary and neuromuscular diseases. Since the ATS published a consensus statement on dyspnea in 1999, there has been enormous growth in knowledge about the neurophysiology of dyspnea and increasing interest in dyspnea as a patient-reported outcome.

PURPOSE

The purpose of this document is to update the 1999 ATS Consensus Statement on dyspnea.

METHODS

An interdisciplinary committee of experts representing ATS assemblies on Nursing, Clinical Problems, Sleep and Respiratory Neurobiology, Pulmonary Rehabilitation, and Behavioral Science determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant expertise. The final content of this statement was agreed upon by all members.

RESULTS

Progress has been made in clarifying mechanisms underlying several qualitatively and mechanistically distinct breathing sensations. Brain imaging studies have consistently shown dyspnea stimuli to be correlated with activation of cortico-limbic areas involved with interoception and nociception. Endogenous and exogenous opioids may modulate perception of dyspnea. Instruments for measuring dyspnea are often poorly characterized; a framework is proposed for more consistent identification of measurement domains.

CONCLUSIONS

Progress in treatment of dyspnea has not matched progress in elucidating underlying mechanisms. There is a critical need for interdisciplinary translational research to connect dyspnea mechanisms with clinical treatment and to validate dyspnea measures as patient-reported outcomes for clinical trials.

An official American Thoracic Society statement: update on the mechanisms, assessment, and management of dyspnea

BACKGROUND

Dyspnea is a common, distressing symptom of cardiopulmonary and neuromuscular diseases. Since the ATS published a consensus statement on dyspnea in 1999, there has been enormous growth in knowledge about the neurophysiology of dyspnea and increasing interest in dyspnea as a patient-reported outcome.

PURPOSE

The purpose of this document is to update the 1999 ATS Consensus Statement on dyspnea.

METHODS

An interdisciplinary committee of experts representing ATS assemblies on Nursing, Clinical Problems, Sleep and Respiratory Neurobiology, Pulmonary Rehabilitation, and Behavioral Science determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant expertise. The final content of this statement was agreed upon by all members.

RESULTS

Progress has been made in clarifying mechanisms underlying several qualitatively and mechanistically distinct breathing sensations. Brain imaging studies have consistently shown dyspnea stimuli to be correlated with activation of cortico-limbic areas involved with interoception and nociception. Endogenous and exogenous opioids may modulate perception of dyspnea. Instruments for measuring dyspnea are often poorly characterized; a framework is proposed for more consistent identification of measurement domains.

CONCLUSIONS

Progress in treatment of dyspnea has not matched progress in elucidating underlying mechanisms. There is a critical need for interdisciplinary translational research to connect dyspnea mechanisms with clinical treatment and to validate dyspnea measures as patient-reported outcomes for clinical trials.

History of suffocation, state-trait anxiety, and anxiety sensitivity in predicting 35% carbon dioxide-induced panic

The aim of this study was to examine the effects of history of suffocation, state-trait anxiety, and anxiety sensitivity on response to a 35% carbon dioxide (CO₂) challenge in panic disorder patients, their healthy first-degree relatives and healthy comparisons. Thirty-two patients with panic disorder, 32 first-degree relatives, and 34 healthy volunteers underwent the 35% CO₂ challenge. We assessed baseline anxiety with the Anxiety Sensitivity Index (ASI) and State-Trait Anxiety Inventory (STAI1), and panic symptoms with the Panic Symptom List (PSL III-R). A history of suffocation was associated with greater risk of CO₂ reactivity in the combined sample. Patients had more anxiety sensitivity and state and trait anxiety than relatives and healthy comparisons; the difference between relatives and healthy comparisons was not significant. In female patients, trait anxiety predicted CO₂-induced panic. Having a CO₂-sensitive panic disorder patient as a first-degree relative did not predict CO₂-induced panic in a healthy relative. History of suffocation may be an important predictor of CO₂-induced panic. Trait anxiety may have a gender-specific relation to CO₂ reactivity.

Panic disorder respiratory subtype: psychopathology, laboratory challenge tests, and response to treatment

OBJECTIVE

Our objective is to summarize the new findings concerning the respiratory subtype (RS) of panic disorder (PD) since its first description.

METHODS

Two searches were made in the Institute for Scientific Information Web of Science: with the keywords "panic disorder" and "respiratory symptoms," and all articles that cited Briggs and colleagues' 1993 article "Subtyping of Panic Disorder by Symptom Profile" (Br J Psychiatry 1993;163:201-9). Altogether, 133 articles were reviewed.

RESULTS

We describe and discuss RS epidemiology, genetics, psychopathology, demographic features, clinical features, correlations with the respiratory system, traumatic suffocation history, provocative tests, and nocturnal panic. Compared to patients with the nonrespiratory subtype (non-RS), the RS patients had higher familial history of PD, lower comorbidity with depression, longer duration of illness, lower neuroticism scores, and higher scores in severity scales, such as the Panic and Agoraphobia Scale, Panic-Agoraphobia Spectrum scale and the Clinical Global Impression scale. Tests to induce panic attacks, such as those with CO(2), hyperventilation, and caffeine, produce panic attacks in a higher proportion of RS patients than non-RS patients. Differences in the subtypes' improvement with the pharmacologic treatment were found. There are also some controversial findings regarding the RS, including the age of onset of PD, and alcohol and tobacco use in RS patients.

CONCLUSIONS

Some characteristics, such as the increased sensitivity to CO(2) and the higher familial history of PD, clearly distinguish the RS from the non-RS. Nevertheless, there are also controversial findings. More studies are needed to determine the validity of the RS subtype.

The impact of panic disorder on interoception and dyspnea reports in chronic obstructive pulmonary disease

The prevalence of panic disorder (PD) in patients with chronic obstructive pulmonary disease (COPD) is significantly higher than that in the general population. Comorbid anxiety disorders in COPD are associated with a number of worse outcomes, however little is known about the mechanisms by which PD affects patients with COPD. We hypothesized that patients with COPD and PD would have greater dyspnea severity, but not greater somatosensory sensitivity, to dyspneic stimuli. We studied 10 patients with COPD and PD, 9 patients with COPD without PD, and 9 healthy, matched controls. Participants were administered the Anxiety Sensitivity Index-3. We tested interoceptive sensitivity using a respiratory load detection protocol and dyspnea ratings in response to inspiratory resistive loads. Participants with COPD and PD had higher anxiety sensitivity scores and reported greater dyspnea in response to resistive loads. However no group differences were found in resistive load detection threshold. Anxiety sensitivity scores accounted for a significant amount of the variance in the group difference in dyspnea ratings. Patients with COPD and PD do not show heightened interoceptive sensitivity, but report greater dyspnea to inspiratory resistive loads. Emotional responses to dyspneic sensations may account for higher dyspnea ratings in patients with PD and COPD.

Caffeine challenge in patients with panic disorder: baseline differences between those who panic and those who do not

A proportion of patients with panic disorder (PD) display an increased sensitivity to the anxiogenic/panicogenic properties of caffeine. The aim of this study is to identify probable baseline differences between PD patients who panic and those who do not, after caffeine administration. In a randomized, double-blind, cross-over experiment performed in two occasions 3-7 days apart, 200 and 400 mg of caffeine, respectively, were administered in a coffee form to 23 patients with PD with or without Agoraphobia. Evaluations included the State-Trait Anxiety Inventory, the DSM-IV 'panic attack' symptoms (visual analogue scale form), the Symptom Checklist-90-Revised (SCL-90-R), as well as breath-holding (BH) duration, heartbeat perception accuracy and heart rate. Only those patients who did not present a panic attack after both challenges ('no panic group', N=14, 66.7%), and those who presented a panic attack after at least one challenge ('panic group', n=7, 33.3%) were included in the analysis. The panickers, compared to the non-panickers, presented at baseline: significantly higher total score of the SCL-90-R; significantly higher scores on all the SCL-90-R clusters of symptoms, except that of 'paranoid ideation'; significantly lower BH duration. The present preliminary findings indicate that PD patients who panic after a 200 mg or a 400 mg caffeine challenge, compared to the PD patients who do not panic after both of these challenges, may present at baseline significantly higher non-specific general psychopathology--as reflected in the SCL-90-R--and significantly shorter BH duration.

Caffeine and 35% carbon dioxide challenge tests in panic disorder

Our aim was to compare the demographic and clinical features of panic disorder (PD) patients with agoraphobia-DSM-IV-who had a panic attack after both an oral caffeine and the 35% carbon dioxide (CO2) challenge tests (responsive group) and compare them with PD patients who did not have a panic attack after both tests (non-responsive group). We examined 83 PD patients submitted to a 35% CO2 test and to an oral caffeine (480 mg) intake within 1 week interval. A panic attack was induced in 51 (61.4%) patients during the CO2 test (chi2=31.67, df=1, p<0.001) and in 38 (45.8%) patients during the caffeine test (chi2=18.28, df=1, p=0.023). All patients who had a panic attack during the caffeine test also had a panic attack during the CO2 test (n=38)-responsive group. The responsive had more (chi2=24.55, df=1, p=0.008) respiratory PD subtype, disorder started earlier (Mann-Whitney, p<0.001) had a higher familial prevalence of PD (chi2=20.34, df=1, p=0.019), less previous alcohol abuse (chi2=23.42, df=1, p<0.001), and had more previous depressive episodes (chi2=27.35, df=1, p<0.001). Our data suggest that there is an association between respiratory PD subtype and hyperreactivity to challenge tests: CO2 and oral caffeine.

Verbal descriptors of dyspnea in patients with COPD at different intensity levels of dyspnea

BACKGROUND

Verbal descriptors of dyspnea are important in understanding the underlying mechanisms, but little is known about the language of dyspnea in COPD. We examined the language of dyspnea in COPD at different intensity levels of dyspnea.

METHODS

Verbal descriptors of dyspnea were assessed in 64 patients with moderate-to-severe COPD (mean age, 62 years; mean percentage of predicted FEV(1) [FEV(1)%pred], 54.1%) during slight dyspnea at rest (mean Borg score, 1.8), moderate dyspnea during cycle ergometer exercise (mean Borg score, 3.1) and somewhat severe dyspnea during a 6-min walking test before (mean Borg score, 4.2), and after pulmonary rehabilitation (PR) [mean Borg score, 3.5]. Furthermore, the influence of age, gender, baseline lung function (FEV(1)%pred), and PR on the verbal descriptors were studied.

RESULTS

A cluster analysis showed that patients differentiated between five clusters of verbal descriptors of dyspnea: heavy/fast breathing, shallow breathing, obstruction, work/effort, and suffocation. These were related to the intensity level of dyspnea but not to age, gender, baseline lung function, or PR. While shallow breathing was predominant only during slight dyspnea at rest, heavy/fast breathing and to a lesser extent work/effort became more important during moderate and somewhat severe dyspnea during exercise. The clusters heavy/fast breathing and work/effort demonstrated the highest sensitivity in discriminating between different intensity levels of dyspnea and in characterizing the positive effects of PR.

CONCLUSIONS

Verbal descriptors of dyspnea in COPD are related to the intensity level of dyspnea. The clusters heavy/fast breathing and work/effort seem to be particularly sensitive descriptors of dyspnea during exercise in COPD.

35% Carbon dioxide and breath-holding challenge tests in panic disorder: a comparison with spontaneous panic attacks

Respiration and its control mechanisms may represent an important system involved in abnormal anxiety. Our aim was to compare the demographic and clinical features of patients with panic disorder (PD) with agoraphobia (DSM-IV) who had a panic attack after both the 35% carbon dioxide (CO(2)) test and the breath-holding test (CPA group), and compare them with PD patients who did not have a panic attack after both tests (NPA group). We examined 76 patients with PD who were administered a 35% CO(2)test and a breath-holding test within a 1-week interval. Anxiety scales were applied before and after each test. A panic attack was induced in 50 (65.8%) patients during the CO(2)test (chi(2) = 28.44, df = 1, P<.001) and in 40 (52.6%) patients during the breath-holding test (chi(2) = 15.35, df = 1, P = .036). All patients who had a panic attack during the breath-holding test also had a panic attack during the CO(2)test (n = 40; CPA group). Twenty-six (34.2%) patients with PD did not have a panic attack after both respiratory tests (NPA group). The CPA group had more (chi(2) = 21.67, df = 1, P = .011) respiratory PD subtype. In the CPA group, the disorder started earlier (Mann-Whitney, P<.001), had a higher familial prevalence of PD (chi(2) = 18.34, df = 1, P = .028), and had more previous depressive episodes (chi(2) = 23.59, df = 1, P<.001). Our data suggest that there is an association between respiratory PD subtype and the response to respiratory challenge tests: CO(2)and breath-holding. The CPA may be confirmed as a subgroup of respiratory PD subtype.

Evaluation of a Respiratory Muscle Biofeedback Procedure–Effects on Heart Rate and Dyspnea

Patients with respiratory diseases or anxiety frequently complain about dyspnea, which may be partly related to chronic tension of respiratory muscles and/or dynamic hyperinflation. In two experiments we tested a biofeedback technique that recorded electromyographic (EMG) activity from a bipolar surface electrode placement over the right external intercostal muscles with visual signal feedback. Healthy participants were tested in their ability to alter the signal. Heart rate was measured continuously throughout training trials. In the second experiment, dyspnea was rated on a modified Borg scale after each trial. Participants were able to increase their EMG activity considerably while heart rate and dyspnea increased substantially. Changes in EMG activity were achieved mostly by manipulating accessory muscle tension and/or altering breathing pattern. Thus, the technique is capable of altering respiratory muscle tension and associated dyspnea. Further studies may test the procedure as a relaxation technique in patients with respiratory disease or anxiety.

Panic attack symptom dimensions and their relationship to illness characteristics in panic disorder

Subtyping panic disorder by predominant symptom constellations, such as cognitive or respiratory, has been done for some time, but criteria have varied considerably between studies. We sought to identify statistically symptom dimensions from intensity ratings of 13 DSM-IV panic symptoms in 343 panic patients interviewed with the Anxiety Disorders Interview Schedule for DSM-IV Lifetime Version. We then explored the relation of symptom dimensions to selected illness characteristics. Ratings were submitted to exploratory maximum likelihood factor analysis with a Promax rotation. A three-factor solution was found to account best for the variance. Symptoms loading highest on the first factor were palpitations, shortness of breath, choking, chest pain, and numbness, which define a cardio-respiratory type (with fear of dying). Symptoms loading highest on the second factor were sweating, trembling, nausea, chills/hot flashes, and dizziness, which defines a mixed somatic subtype. Symptoms loading highest on the third factor were feeling of unreality, fear of going crazy, and fear of losing control, which defines a cognitive subtype. Subscales based on these factors showed moderate intercorrelations. In a series of hierarchical multiple regression analyses, the cardio-respiratory subscale was a strong predictor of panic severity, frequency of panic attacks, and agoraphobic avoidance, while the cognitive subscale mostly predicted worry due to panic. In addition, patients with comorbid asthma had higher scores on the cardio-respiratory subscale. We conclude that partly independent panic symptom dimensions can be identified that have different implications for severity and control of panic disorder.

Characterization of a 7% carbon dioxide (CO2) inhalation paradigm to evoke anxiety symptoms in healthy subjects

The present study is aimed at characterizing the carbon dioxide (CO2) procedure in healthy subjects to achieve reliable provocation of anxiety symptoms. Thirty healthy subjects inhaled in single-blind both compressed air and 7% CO2 mixture. Panic Symptom List (PSLIII-R), Visual Analogue Scale-Anxiety (VAS-A), State Anxiety Inventory (STAI-Y/1), respiratory parameters and skin conductance were measured. 'Responders' were classified depending on PSLIII-R scores after CO2. Twelve out of the 21 'responders' performed a second test to assess test-retest repeatability. In 21 subjects Delta%VAS-A (45.4 +/- 32.1) and PSLIII-R (pre-test 2.3 +/-2.1, post-test 17.5 +/- 8.2) but not STAI-Y/1, significantly increased during CO2 inhalation. Respiratory Rate, Minute Volume, end-Tidal CO2 and skin conductance rose in 'responders'. Repeatability was studied with Bland-Altman plots, revealing mean difference between tests close to 0 for both Delta%VAS-A and PSLIII-R. Among physiologic parameters, end-Tidal CO2 and Respiratory Rate showed good repeatability, with a within-subject CV of 9.2% and 6%, respectively. The challenge produced measurable response in healthy subjects. Good test-retest repeatability was observed in 'responders'. These data indicate that the test can be suitable for testing putative anti-panic or anxiolytic drugs in clinical studies using a within subject, crossover design.