Cortical Sources of Respiratory Mechanosensation, Laterality, and Emotion: An MEG Study

Patient-reported respiratory symptoms and relevant factors in patients with pulmonary nodules

Background

Pulmonary nodules (PNs) are commonly considered too small to cause respiratory symptoms. However, many PN patients present with respiratory symptoms of unknown origin. This study aims to explore these symptoms and identify the associated factors.

Methods

Demographic and clinical information were retrospectively collected from 1,633 patients with incidental PNs who visited the thoracic outpatient clinic of Guangdong Provincial People's Hospital. Hospital Anxiety and Depression Scale was used to assess their anxiety and depression level. Logistic regression analyzes were employed to assess the independent risk factors for respiratory symptoms and the psychological impact on patients.

Results

Among the 1,633 patients, 37.2% reported at least one respiratory symptom. The most common symptoms in patients with PNs were cough (23.6%), followed by chest pain (14.0%), expectoration (13.8%) and hemoptysis (1.3%). Patients with large PNs (>20 mm) showed significantly higher odds of having cough [odds ratio (OR) =2.5; P=0.011] and expectoration (OR =3.6; P=0.001). Patients with multiple PNs were more susceptible to chest pain compared to those with solitary PNs (OR =1.5; P=0.007). Environmental factors such as passive smoking, kitchen fume pollution, environmental dust were the consistent risk contributors to the presence of these respiratory symptoms. Comparable findings were observed among the subgroup of individuals who undergo chest computed tomography scans as a part of their routine health check-up. Presence of respiratory symptoms, especially chest pain, was associated with increased the odds of anxiety (OR =2.2; P<0.001) and depression (OR =2.5; P<0.001) in patients.

Conclusions

Respiratory symptoms are common in PN patients, exhibiting a higher prevalence in patients with larger and multiple PNs and there is a strong association with exposure to environmental risk factors. These symptoms might exacerbate the anxiety and depression level in patients.

Effects of emotional contexts on respiratory attention task performance

Negative emotions have been found associated with high prevalence of respiratory disease and increased subjective feelings of dyspnea, while positive emotional stimulus has been suggested to alleviate dyspneic feelings. However, the extent to which different emotional contexts affect individuals' respiratory interoceptive attention was not clear. Therefore, the purpose of this study was to investigate the influences of emotional contexts on respiratory interoceptive accuracy, and the relationships between respiratory interoceptive accuracy and negative emotions as well as respiratory symptoms. Fifty-six healthy participants completed the self-reported questionnaires of depression, anxiety, and respiratory symptoms. During the experiment, the participants were instructed to watch one neutral and one positive affective picture series and mentally count the number of perceived occlusions (reported at the end of the trials). The Wilcoxon Signed-Rank test and Spearman's correlations were used to examine the effect of the emotional pictures and to explore the relationships between the level of emotional status or respiratory symptoms and respiratory interoceptive task performance. The significance level was set at p < 0.05. Our results did not show a significant difference in participants' occlusion counting task performance between the neutral and positive emotional context. However, Spearman's Rho correlation analysis revealed that depression level was negatively correlated with accuracy of the task performance in the neutral emotional context, and this relationship diminished in the positive emotional context. In summary, our study demonstrated that negative emotional status, especially depression, may lead to decreased respiratory interoceptive accuracy. Future studies are recommended to test the effect of positive emotional context on respiratory interoceptive task performance in individuals with clinical depression and anxiety.

The impact of emotional context on neural substrates of respiratory sensory gating

Psychological challenges have been found to impact respiratory symptom perception in healthy individuals as well as in patients with various neurological disorders. Human respiratory sensory gating is an objective measure to examine respiratory sensory information processing of repetitive respiratory mechanical stimuli in the central nervous system. With this electrophysiological method, patients with higher anxiety levels showed reduced respiratory sensory gating function in the cortex, and increased symptom perception. In addition, positive emotional contexts were found to increase the respiratory sensory gating function using RREPs. However, neural substrates related to emotional impacts on respiratory sensory gating remain still unclear. In the present study, we examined the emotion processing of respiratory sensory gating using functional magnetic resonance imaging. We hypothesized that positive compared with neutral stimuli would result in reduced brain activations in cortical areas with the paired occlusion paradigm. Thirty-five healthy adults participated in this event-designed fMRI experiment. Paired inspiratory occlusions (two transient occlusions with a 500 ms inter-stimulus-interval are delivered during one inspiration) were provided using an external trigger outside of the scanner. At least 40 paired inspiratory occlusions were collected for each trial. The experiment contained three runs during which participants underwent 12 min for the paired inspiratory occlusion paradigm while watching a fixation cross (the control condition), neutral and positive emotional picture series. The order of emotional picture series was randomized across the participants. Our results revealed an overall trend of reduction of brain activity from the neutral (minus fixation) condition, to the pleasant (minus fixation) condition. For bilateral thalamus and primary visual cortices, there was no significant difference in neural activation between the two contrasts of pleasant (Contrast_P–F) and neutral condition (Contrast_N–F). The activation of the mid-cingulate and the orbitofrontal cortex was lower in Contrast_P–F compared to Contrast_N–F. In conclusion, our results suggest that emotional context, especially positive valence, modulates neural correlates in middle cingulate cortex and orbitofrontal cortex in terms of respiratory sensory gating. Future studies are recommended to test emotional impacts on respiratory sensations in patients with neurological disorders.