Challenging anxiety: a focus on the specificity of respiratory symptoms

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).

Mouse strain-specific acute respiratory effects of nicotine unrelated to nicotine metabolism

Plethysmograph measurement of respiratory phenotypes provides a highly sensitive means to study nicotine response in experimental model animals. We measured average respiratory frequency, tidal volume, minute volume and inspiratory time in C3H/HeJ and C57BL/6J mice subcutaneously administered 0.35 and 0.70 mg/kg nicotine. Both mouse strains showed significantly altered respiratory and locomotion phenotypes relative to saline-injected controls when administered the higher dose, but only C57BL/6J responded to the lower nicotine dose. Respiratory and locomotion phenotypes rarely differed significantly by sex. To investigate whether the strain-specific differences in nicotine sensitivity were related to differences in clearance, we followed up by measuring nicotine clearance in C3H/HeJ and C57BL/6J mice (0.35 mg/kg subcutaneous) and found sex differences in both strains, but no difference between strains.

Automated analysis of breathing waveforms using BreathMetrics: a respiratory signal processing toolbox

Nasal inhalation is the basis of olfactory perception and drives neural activity in olfactory and limbic brain regions. Therefore, our ability to investigate the neural underpinnings of olfaction and respiration can only be as good as our ability to characterize features of respiratory behavior. However, recordings of natural breathing are inherently nonstationary, nonsinusoidal, and idiosyncratic making feature extraction difficult to automate. The absence of a freely available computational tool for characterizing respiratory behavior is a hindrance to many facets of olfactory and respiratory neuroscience. To solve this problem, we developed BreathMetrics, an open-source tool that automatically extracts the full set of features embedded in human nasal airflow recordings. Here, we rigorously validate BreathMetrics' feature estimation accuracy on multiple nasal airflow datasets, intracranial electrophysiological recordings of human olfactory cortex, and computational simulations of breathing signals. We hope this tool will allow researchers to ask new questions about how respiration relates to body, brain, and behavior.

The breathing conundrum-interoceptive sensitivity and anxiety

Cognitive and affective processing has been the central focus of brain-related functions in psychology and psychiatry for many years. Much less attention has been paid to what could be considered the primary function of the brain, to regulate the function of the body. Recent developments, which include the conceptualization of interoception as a process consisting of integrating the information coming from the inside of the body in the central nervous system and the appreciation that complex emotional processes are fundamentally affected by the processing and regulation of somatic states, have profoundly changed the view of the function and dysfunction of the brain. This review focuses on the relationship between breathing and anxiety. Several anxiety disorders have been associated with altered breathing, perception of breathing, and response to manipulations of breathing. Both clinical and experimental research studies are reviewed that relate breathing dysfunctions to anxiety. Altered breathing may be useful as a physiological marker of anxiety as well as a treatment target using interoceptive interventions.