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

Conditioned fear selectively increases the perception and neural processing of respiratory stimuli relative to somatosensory stimuli

Interoception is crucial to the experience of bodily complaints in chronic conditions. Fear can distort the perception of sensations like breathlessness and pain, yet few studies investigated the effects of conditioned fear on both self-report and neural processing of these sensations. In the current study, we conditioned fear of neutral female faces in healthy adults, pairing certain faces (CS+) with an aversive scream. In Experiment 1, we delivered paired inspiratory occlusions during the viewing of the faces. We collected self-reported intensity and unpleasantness of occlusions, and measured N1 and P2 amplitudes of the respiratory-related evoked potential (RREP) in the electroencephalogram, as well as neural gating (the ratio of N1 response to the second over the first occlusion, S2/S1). Skin conductance and self-reported fear increased in response to CS+ faces, and perception of occlusions increased during fear conditioning (FC) relative to baseline, with higher unpleasantness and RREP amplitudes during CS+ relative to CS- trials. We found no effects on neural gating. In Experiment 2, we used the same FC protocol, and delivered paired electrocutaneous pulses during the viewing of the faces. We measured intensity/unpleasantness, fear, N1/P2 amplitudes of the somatosensory evoked potential (SEP), and neural gating. While skin conductance and fear increased, no perceptual effects were found. Unexpectedly, SEP amplitudes decreased and neural gating increased during FC, likely due to habituation. The current results indicate that FC increases the perception and neural processing of respiratory stimuli specifically, consistent with previous literature on respiratory psychophysiology and fearful states.

Learned Symptom-Specific Fear Toward a Visceral Sensation and Its Impact on Perceptual Habituation

OBJECTIVE

Impaired habituation of bodily sensations has been suggested as a contributing factor to chronic pain. We examined in healthy volunteers the influence of fear learning toward a nonpainful sensation in the esophagus on the perceptual habituation of this sensation.

METHODS

In a homoreflexive fear learning paradigm, nonpainful electrical sensations in the esophagus were used as a conditioned stimulus (CS). This sensation was presented 42 times before, during, and after fear learning. In the fear learning group ( n = 41), the CS was paired with a painful electrical sensation in the esophagus (unconditioned stimulus [US]). In the control group ( n = 41), the CS was not paired with the US. Ratings for CS intensity, US expectancy, startle electromyogram (EMG), skin conductance responses (SCR), and event-related potentials (ERPs) to the CS were assessed.

RESULTS

Compared to the control group, fear learning was observed in the fear learning group as evidenced by potentiated startle responses after the CS relative to ITI ( t (1327) = 3.231, p = .001) and higher US expectancy ratings ( t (196) = 3.17, p = .002). SCRs did not differ between groups ( F1,817 = 1.241, p = .33). Despite successful fear learning, the fear learning group did not show a distinct pattern of habituation to the visceral CS relative to the control group (intensity ratings: F1,77.731 = 0.532, p = .47; ERPs: F1,520.78 = 0.059, p = .94).

CONCLUSION

Acquired fear to nonpainful esophageal sensations does not affect their perceptual habituation patterns.

Descriptive Study on the Relationship between Dyspnea, Physical Performance, and Functionality in Oncology Patients

BACKGROUND

Cancer is a leading cause of morbidity and mortality globally. Dyspnea, affecting up to 60% of cancer patients, exacerbates physical and psychological distress, reducing quality of life. This study aims to explore the relationship between dyspnea and factors such as age, sex, clinical diagnosis, and treatment lines in cancer patients, with the goal of improving understanding and management of this debilitating symptom to enhance patient care and quality of life.

METHODS

This study employed an observational, cross-sectional, and descriptive approach to investigate patients with oncological disease at the University Hospital of Salamanca between March 2021 and April 2024. A convenience sample was selected, including patients over 18 years old with a pathological diagnosis of cancer, experiencing any degree of dyspnea, and who consented to participate by signing the informed consent. Exclusion criteria included lack of consent and clinical conditions that prevented an interview. The studied variables encompass sociodemographic (age, gender, diagnosis, tumor stage, number of treatment lines) and clinical aspects (daily activities, degree of dyspnea, functional capacity, physical performance), evaluated using the Barthel Index, the mMRC Dyspnea Scale, the ECOG Scale, and the Short Physical Performance Battery (SPPB). Data were collected through semistructured interviews and medical records, and analyzed using specialized software. This research has ethical approval CEiM Code 2023 12 1472, Reference 2024/01.

RESULTS

The mean age was 66.82 years. Lung cancer was predominant (60.2%), with most patients in stage 3 (65.7%) and receiving three treatment lines (68.7%). Higher age, advanced disease stage, and more treatment lines correlated with lower Barthel and SPPB scores, and higher ECOG and mMRC scores, indicating worse functionality, physical performance, and greater dyspnea. No significant correlations were found between gender or pathological diagnosis and the studied variables.

CONCLUSIONS

Advanced age, higher disease stage, and more treatment lines are associated with decreased functionality, poorer physical performance, and increased dyspnea in cancer patients. Gender and specific cancer diagnosis do not significantly affect these relationships. Addressing dyspnea is crucial to improving the quality of life and physical performance in this population. Future studies should explore additional factors like treatment types and nutritional status.

The effect of unpredictability on the perception of breathlessness: a narrative review

Breathlessness is an aversive bodily sensation impacting millions of people worldwide. It is often highly detrimental for patients and can lead to profound distress and suffering. Notably, unpredictable breathlessness episodes are often reported as being more severe and unpleasant than predictable episodes, but the underlying reasons have not yet been firmly established in experimental studies. This review aimed to summarize the available empirical evidence about the perception of unpredictable breathlessness in the adult population. Specifically, we examined: (1) effects of unpredictable relative to predictable episodes of breathlessness on their perceived intensity and unpleasantness, (2) potentially associated neural and psychophysiological correlates, (3) potentially related factors such as state and trait negative affectivity. Nine studies were identified and integrated in this review, all of them conducted in healthy adult participants. The main finding across studies suggested that unpredictable compared to predictable, breathlessness elicits more frequently states of high fear and distress, which may contribute to amplify the perception of unpredictable breathlessness, especially its unpleasantness. Trait negative affectivity did not seem to directly affect the perception of unpredictable breathlessness. However, it seemed to reinforce state fear and anxiety, hence possible indirect modulatory pathways through these affective states. Studies investigating neural correlates of breathlessness perception and psychophysiological measures did not show clear associations with unpredictability. We discuss the implication of these results for future research and clinical applications, which necessitate further investigations, especially in clinical samples suffering from breathlessness.

Lung and diaphragm protective ventilation: a synthesis of recent data

INTRODUCTION

: To adhere to the Hippocratic Oath, to "first, do no harm", we need to make every effort to minimize the adverse effects of mechanical ventilation. Our understanding of the mechanisms of ventilator-induced lung injury (VILI) and ventilator-induced diaphragm dysfunction (VIDD) has increased in recent years. Research focuses now on methods to monitor lung stress and inhomogeneity and targets we should aim for when setting the ventilator. In parallel, efforts to promote early assisted ventilation to prevent VIDD have revealed new challenges, such as titrating inspiratory effort and synchronizing the mechanical with the patients' spontaneous breaths, while at the same time adhering to lung-protective targets.

AREAS COVERED

This is a narrative review of the key mechanisms contributing to VILI and VIDD and the methods currently available to evaluate and mitigate the risk of lung and diaphragm injury.

EXPERT OPINION

Implementing lung and diaphragm protective ventilation requires individualizing the ventilator settings, and this can only be accomplished by exploiting in everyday clinical practice the tools available to monitor lung stress and inhomogeneity, inspiratory effort, and patient-ventilator interaction.