When dyspnea gets worse: Suffocation fear and the dynamics of defensive respiratory responses to increasing interoceptive threat

Interoceptive technologies for psychiatric interventions: From diagnosis to clinical applications

Interoception-the perception of internal bodily signals-has emerged as an area of interest due to its implications in emotion and the prevalence of dysfunctional interoceptive processes across psychopathological conditions. Despite the importance of interoception in cognitive neuroscience and psychiatry, its experimental manipulation remains technically challenging. This is due to the invasive nature of existing methods, the limitation of self-report and unimodal measures of interoception, and the absence of standardized approaches across disparate fields. This article integrates diverse research efforts from psychology, physiology, psychiatry, and engineering to address this oversight. Following a general introduction to the neurophysiology of interoception as hierarchical predictive processing, we review the existing paradigms for manipulating interoception (e.g., interoceptive modulation), their underlying mechanisms (e.g., interoceptive conditioning), and clinical applications (e.g., interoceptive exposure). We suggest a classification for interoceptive technologies and discuss their potential for diagnosing and treating mental health disorders. Despite promising results, considerable work is still needed to develop standardized, validated measures of interoceptive function across domains and before these technologies can translate safely and effectively to clinical settings.

The Role of Illness Perceptions in Dyspnoea-Related Fear in Chronic Obstructive Pulmonary Disease

Dyspnoea is often the most distressing symptom described by people with a chronic respiratory condition. The traditional biomedical model of neuromechanical uncoupling that explains the physiological basis for dyspnoea is well accepted. However, in people with chronic obstructive pulmonary disease (COPD), measures that are linked with neuromechanical uncoupling are poorly related to the restriction in activity during daily life attributed to dyspnoea. This suggests that activity restriction that results from dyspnoea is influenced by factors other than expiratory airflow limitation and dynamic pulmonary hyperinflation, such as the ways people perceive, interpret and respond to this sensation. This review introduces the common-sense model as a framework to understand the way an individual's lay beliefs surrounding sensations can lead to these sensations being perceived as a health threat and how this impacts their emotional and behavioural responses. The aim is to provide insight into the nuances that can shape an individual's personal construct of dyspnoea and offer practical suggestions to challenge unhelpful beliefs and facilitate cognitive re-structuring as a pathway to reduce distress and optimise health behaviours and outcomes.

Understanding anxiety symptoms as aberrant defensive responding along the threat imminence continuum

Threat-anticipatory defensive responses have evolved to promote survival in a dynamic world. While inherently adaptive, aberrant expression of defensive responses to potential threat could manifest as pathological anxiety, which is prevalent, impairing, and associated with adverse outcomes. Extensive translational neuroscience research indicates that normative defensive responses are organized by threat imminence, such that distinct response patterns are observed in each phase of threat encounter and orchestrated by partially conserved neural circuitry. Anxiety symptoms, such as excessive and pervasive worry, physiological arousal, and avoidance behavior, may reflect aberrant expression of otherwise normative defensive responses, and therefore follow the same imminence-based organization. Here, empirical evidence linking aberrant expression of specific, imminence-dependent defensive responding to distinct anxiety symptoms is reviewed, and plausible contributing neural circuitry is highlighted. Drawing from translational and clinical research, the proposed framework informs our understanding of pathological anxiety by grounding anxiety symptoms in conserved psychobiological mechanisms. Potential implications for research and treatment are discussed.

Psychological Morbidity After COVID-19 Critical Illness

Survivors of ICU hospitalizations often experience severe and debilitating symptoms long after critical illness has resolved. Many patients experience notable psychiatric sequelae such as depression, anxiety, and posttraumatic stress disorder (PTSD) that may persist for months to years after discharge. The COVID-19 pandemic has produced large numbers of critical illness survivors, warranting deeper understanding of psychological morbidity after COVID-19 critical illness. Many patients with critical illness caused by COVID-19 experience substantial post-ICU psychological sequelae mediated by specific pathophysiologic, iatrogenic, and situational risk factors. Existing and novel interventions focused on minimizing psychiatric morbidity need to be further investigated to improve critical care survivorship after COVID-19 illness. This review proposes a framework to conceptualize three domains of risk factors (pathophysiologic, iatrogenic, and situational) associated with psychological morbidity caused by COVID-19 critical illness: (1) direct and indirect effects of the COVID-19 virus in the brain; (2) iatrogenic complications of ICU care that may disproportionately affect patients with COVID-19; and (3) social isolation that may worsen psychological morbidity. In addition, we review current interventions to minimize psychological complications after critical illness.

Recent insights into respiratory modulation of brain activity offer new perspectives on cognition and emotion

Over the past six years, a rapidly growing number of studies have shown that respiration exerts a significant influence on sensory, affective, and cognitive processes. At the same time, an increasing amount of experimental evidence indicates that this influence occurs via modulation of neural oscillations and their synchronization between brain areas. In this article, we review the relevant findings and discuss whether they might inform our understanding of a variety of disorders that have been associated with abnormal patterns of respiration. We review literature on the role of respiration in chronic obstructive pulmonary disease (COPD), anxiety (panic attacks), and autism spectrum disorder (ASD), and we conclude that the new insights into respiratory modulation of neuronal activity may help understand the relationship between respiratory abnormalities and cognitive and affective deficits.

Hold your breath: Voluntary breath-holding time predicts defensive activation to approaching internal threat

Bodily disturbances, like dyspnea, elicit responses to regain homeostasis and ensure survival. However, this life-saving function can become hyperreactive, which may lead to the emergence of psychopathology. This study investigated whether maximal voluntary breath-holding time (mvBHT), a biobehavioral marker that characterizes sensitivity to respiratory stimulation, predicts defensive mobilization to cues signaling the proximity of a mild electric shock vs. a respiratory threat (shortness of breath elicited by forced breath-holding) and the opportunity to avoid threat delivery in 60 healthy participants. While the startle reflex, a measure of defensive mobilization, generally increased with the proximity of an inevitable threat, shorter breath-holding time was specifically associated with greater startle potentiation when anticipating a respiratory threat but not an electric shock. In contrast, when both threats were avoidable, the startle reflex was comparably inhibited, irrespective of mvBHT. This study suggests that mvBHT specifically predicts hypersensitive responding to an anticipated inevitable respiratory threat.

Vagal control of the heart decreases during increasing imminence of interoceptive threat in patients with panic disorder and agoraphobia

Theoretically, panic disorder and agoraphobia pathology can be conceptualized as a cascade of dynamically changing defensive responses to threat cues from inside the body. Guided by this trans-diagnostic model we tested the interaction between defensive activation and vagal control as a marker of prefrontal inhibition of subcortical defensive activation. We investigated ultra-short-term changes of vagally controlled high frequency heart rate variability (HRV) during a standardized threat challenge (entrapment) in n = 232 patients with panic disorder and agoraphobia, and its interaction with various indices of defensive activation. We found a strong inverse relationship between HRV and heart rate during threat, which was stronger at the beginning of exposure. Patients with a strong increase in heart rate showed a deactivation of prefrontal vagal control while patients showing less heart rate acceleration showed an increase in vagal control. Moreover, vagal control collapsed in case of imminent threat, i.e., when body symptoms increase and seem to get out of control. In these cases of defensive action patients either fled from the situation or experienced a panic attack. Active avoidance, panic attacks, and increased sympathetic arousal are associated with an inability to maintain vagal control over the heart suggesting that teaching such regulation strategies during exposure treatment might be helpful to keep prefrontal control, particularly during the transition zone from post-encounter to circa strike defense.

Trial Registration Number: ISRCTN80046034.

The impact of unpredictability of dyspnea offset on dyspnea perception, fear, and respiratory neural gating

Dyspnea is a debilitating and threatening symptom in various diseases. Affected patients often report the unpredictability of dyspnea episodes being particularly anxiety-provoking and amplifying the perception of dyspnea. Experimental studies testing dyspnea unpredictability together with related neural processes, physiological fear responses, and dyspnea-related personality traits are sparse. Therefore, we investigated the impact of unpredictability of dyspnea offset on dyspnea perception and fear ratings, respiratory neural gating and physiological fear indices, as well as the influence of interindividual differences in fear of suffocation (FoS). Forty healthy participants underwent a task manipulating the offset predictability of resistive load-induced dyspnea including one unloaded safety condition. Respiratory variables, self-reports of dyspnea intensity, dyspnea unpleasantness, and fear were recorded. Moreover, respiratory neural gating was measured in a paired inspiratory occlusion paradigm using electroencephalography, while electrodermal activity, startle eyeblink, and startle probe N100 were assessed as physiological fear indices. Participants reported higher dyspnea unpleasantness and fear when dyspnea offset was unpredictable compared to being predictable. Individuals with high levels of FoS showed the greatest increase in fear and overall higher levels of fear and physiological arousal across all conditions. Respiratory neural gating, startle eyeblink, and startle probe N100 showed general reductions during dyspnea conditions but no difference between unpredictable and predictable dyspnea conditions. Together, the current results suggest that the unpredictable offset of dyspnea amplifies dyspnea perception and fear, especially in individuals with high levels of FoS. These effects were unrelated to respiratory neural gating or physiological fear responses, requiring future studies on underlying mechanisms.

Panic and pandemic: Narrative review of the literature on the links and risks of panic disorder as a consequence of the SARS-CoV-2 pandemic

Although the “panic” word has been abundantly linked to the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic in the press, in the scientific literature very few studies have considered whether the current epidemic could predispose to the onset or the aggravation of panic attacks or panic disorder. Indeed, most studies thus far have focused on the risk of increase and aggravation of other psychiatric disorders as a consequence of the SARS-CoV-2 epidemic, such as obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and generalized anxiety disorder (GAD). Yet, risk of onset or aggravation of panic disorder, especially the subtype with prominent respiratory symptoms, which is characterized by a fear response conditioning to interoceptive sensations (e.g., respiratory), and hypervigilance to these interoceptive signals, could be expected in the current situation. Indeed, respiratory symptoms, such as coughs and dyspnea, are among the most commonly associated with the SARS-CoV-2 (59–82% and 31–55%, respectively), and respiratory symptoms are associated with a poor illness prognosis. Hence, given that some etiological and maintenance factors associated with panic disorder – i.e., fear conditioning to abnormal breathing patterns attributable or not to the COVID-19 (coronavirus disease 2019), as well as hypervigilance towards breathing abnormalities – are supposedly more prevalent, one could expect an increased risk of panic disorder onset or aggravation following the COVID-19 pandemic in people who were affected by the virus, but also those who were not. In people with the comorbidity (i.e., panic disorder or panic attacks and the COVID-19), it is particularly important to be aware of the risk of hypokalemia in specific at-risk situations or prescriptions. For instance, in the case of salbutamol prescription, which might be overly used in patients with anxiety disorders and COVID-19, or in patients presenting with diarrhea and vomiting. Hypokalemia is associated with an increased risk of torsade de pointe; thus, caution is required when prescribing specific psychotropic drugs, such as the antidepressants citalopram and escitalopram, which are first-line treatments for panic disorder, but also hydroxyzine, aiming at anxiety relief. The results reviewed here highlight the importance of considering and further investigating the impact of the current pandemic on the diagnosis and treatment of panic disorder (alone or comorbid with the COVID-19).

[Panic and pandemic: Review of the literature on the links between panic disorder and the SARS-CoV-2 epidemic]

Although the "panic" word has been abundantly linked to the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic in the press, in the scientific literature very few studies have considered whether the current epidemic could predispose to the onset or the aggravation of panic attacks or panic disorder. Indeed, most studies thus far have focused on the risk of increase and aggravation of other psychiatric disorders as a consequence of the SARS-CoV-2 epidemic, such as obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and generalized anxiety disorder (GAD). Yet, risk of onset or aggravation of panic disorder, especially the subtype with prominent respiratory symptoms, which is characterized by a fear response conditioning to interoceptive sensations (e.g., respiratory), and hypervigilance to these interoceptive signals, could be expected in the current situation. Indeed, respiratory symptoms, such as coughs and dyspnea, are among the most commonly associated with the SARS-CoV-2 (59-82% and 31-55%, respectively), and respiratory symptoms are associated with a poor illness prognosis. Hence given that some etiological and maintenance factors associated with panic disorder - i.e., fear conditioning to abnormal breathing patterns attributable or not to the COVID-19 (coronavirus disease 2019), as well as hypervigilance towards breathing abnormalities - are supposedly more prevalent, one could expect an increased risk of panic disorder onset or aggravation following the COVID-19 epidemic in people who were affected by the virus, but also those who were not. In people with the comorbidity (i.e., panic disorder or panic attacks and the COVID-19), it is particularly important to be aware of the risk of hypokalemia in specific at-risk situations or prescriptions. For instance, in the case of salbutamol prescription, which might be overly used in patients with anxiety disorders and COVID-19, or in patients presenting with diarrhea and vomiting. Hypokalemia is associated with an increased risk of torsade de pointe, thus caution is required when prescribing specific psychotropic drugs, such as the antidepressants citalopram and escitalopram, which are first-line treatments for panic disorder, but also hydroxyzine, aiming at anxiety reduction. The results reviewed here highlight the importance of considering and further investigating the impact of the current pandemic on the diagnosis and treatment of panic disorder (alone or comorbid with the COVID-19).

Psychological Mediation of Dysfunction and Hyperfunction of Respiratory Regulation

This research investigates the continuum between the dysfunction and the hyperfunction of breath regulation and presents the psychological mediation that supports or disrupts this regulation. The pilot study compared breathing regulation in patients with hyperventilation syndrome (HVS), free divers, and healthy volunteers. To examine the ability of voluntary respiration regulation, breath holding involving "easy-going" and "struggling" phases was used. Psychological mediation was assessed through (a) respiratory experience interviews, (b) anxiety levels, and (c) psycho-semantic techniques. Free divers have a bigger "positive breathing vocabulary" and can endure the conflict between the physiological need to inhale and the voluntary motivation to hold their breath for longer. The connection between emotions and negative breathing experience in patients with HVS leads to less breathing control.

The Effects of Repeated Dyspnea Exposure on Response Inhibition

In order to treat dyspnea (=breathlessness) successfully, response inhibition (RI) as a major form of self-regulation is a premise. This is supported by research showing that self-regulation is associated with beneficial behavioral changes supporting treatment success in patients. Recent research showed that dyspnea has an impairing effect on RI, but the effects of repeated dyspnea exposure on RI remain unknown. Therefore, the present study tested the effects of repeated resistive load-induced dyspnea on RI over a 5-day period. Healthy volunteers (n = 34) performed the standard version of the Stroop task during baseline and dyspnea conditions on the first and fifth testing day and underwent an additional dyspnea exposure phase on each testing day. Variables of interest to investigate RI were reaction time, accuracy as well as the event-related potentials late positive complex (LPC) and N400 in the electroencephalogram. Reduced accuracy for incongruent compared to congruent stimuli during the dyspnea condition on the first testing day were found (p < 0.001). This was paralleled by a reduced LPC and an increased N400 for incongruent stimuli during the induction of dyspnea (p < 0.05). After undergoing dyspnea exposure, habituation of dyspnea intensity was evident. Importantly, on the fifth testing day, no differences between baseline, and dyspnea conditions were found for behavioral and electrophysiological measures of RI. These findings demonstrate that the impairing effect of dyspnea on RI disappeared after repeated dyspnea exposure in healthy participants. Translated to a clinical sample, it might cautiously be suggested that dyspnea exposure such as dyspnea perceived during physical exercise could reduce the impairing effect of dyspnea on RI which might have the potential to help increase self-regulation abilities and subsequent treatment efforts in dyspneic patients.

Fine particulate matter exposure and medication dispensing during and after a coal mine fire: A time series analysis from the Hazelwood Health Study

Limited research has examined the impacts of coal mine fire smoke on human health. The aim of this study was to assess the association between prolonged smoke PM_2.5 exposure from a brown coal mine fire that burned over a seven week period in 2014 and medications dispensed across five localities in South-eastern Victoria, Australia. Spatially resolved PM_2.5 concentrations were retrospectively estimated using a dispersion model coupled with a chemical transport model. Data on medications dispensed were collected from the national Pharmaceutical Benefits Schedule database for 2013-2016. Poisson distributed lag time series analysis was used to examine associations between daily mine fire-related PM_2.5 concentrations and daily counts of medications dispensed for respiratory, cardiovascular or psychiatric conditions. Factors controlled for included: seasonality, long-term trend, day of the week, maximum ambient temperature and public holidays. Positive associations were found between mine fire-related PM_2.5 and increased risks of medications dispensed for respiratory, cardiovascular and psychiatric conditions, over a lag range of 3-7 days. A 10 μg/m³ increase in coal mine fire-related PM_2.5 was associated with a 25% (95%CI 19-32%) increase in respiratory medications, a 10% (95%CI 7-13%) increase in cardiovascular medications and a 12% (95%CI 8-16%) increase in psychiatric medications dispensed. These findings have the potential to better prepare for and develop more appropriate public health responses in the event of future coal mine fires.

The impact of dyspnea and threat of dyspnea on error processing

Dyspnea (breathlessness) is a threatening and aversive bodily sensation and a major symptom of various diseases. It has been suggested to impair several aspects of functioning in affected patients, but experimental proof for this assumption is widely absent. Error processing is an important domain of functioning and has intensively been studied using electrophysiological measures. Specifically, the error-related negativity (ERN) has been suggested to reflect early performance monitoring and error detection, while the error positivity (Pe) has been linked to subsequent error awareness. So far, little is known about the effects of anticipated or perceived dyspnea on error processing. Therefore, in 49 healthy participants, we studied the effects of experimentally induced dyspnea and threat of dyspnea on the ERN/Pe and behavioral task performance. Participants performed the arrowhead version of the flanker task during three experimental conditions: an unloaded baseline condition, a dyspnea condition, and a threat of dyspnea condition. Dyspnea was induced by breathing through inspiratory resistive loads, while high-density EEG was continuously measured. No differences in task performance (reaction times, error rates) and ERN mean amplitudes were found between conditions. However, mean amplitudes for the Pe differed between conditions with smaller Pe amplitudes during threat of dyspnea compared to baseline and dyspnea conditions, with the latter two conditions showing no difference. These results may suggest that threat of dyspnea, but not dyspnea itself, reduces error awareness, while both seem to have no impact on early error processing and related behavioral performance.

Hypoventilation Therapy Alleviates Panic by Repeated Induction of Dyspnea

BACKGROUND

Previous research has shown that hypoventilation therapy reduces panic symptoms in part by increasing basal partial pressure of carbon dioxide (PCO₂) levels. We tested an additional pathway by which hypoventilation therapy could exert its therapeutic effects: through repeated interoceptive exposure to sensations of dyspnea.

METHODS

A total of 35 patients with panic disorder were trained to perform exercises to raise their end-tidal PCO₂ levels using a portable capnometry device. Anxiety, dyspnea, end-tidal PCO₂, and respiratory rate were assessed during each exercise across 4 weeks of training. Mixed-model analysis examined whether within-exercise levels of dyspnea were predictive of reduction of panicogenic cognitions.

RESULTS

As expected, within-exercise anxiety and respiratory rate decreased over time. Unexpectedly, PCO₂ dropped significantly from the beginning to the end of exercise, with these drops becoming progressively smaller across weeks. Dyspnea increased and remained consistently above basal levels across weeks. As hypothesized, greater dyspnea was related to significantly lower panicogenic cognitions over time even after controlling for anxiety and PCO₂. Additional exploratory analyses showed that within-exercise increases in dyspnea were related to within-exercise increases in anxiety but were not related to within-exercise increases in PCO₂.

CONCLUSIONS

In support of the interoceptive exposure model, we found that greater dyspnea during hypoventilation exercises resulted in lower panicogenic cognitions even after the effect of PCO₂ was taken into account. The findings offer an additional important target in panic treatment.