Acquired lightheadedness in response to odors after hyperventilation

Respiratory dysfunction in persistent somatic symptoms: A systematic review of observational studies

OBJECTIVE

This systematic review aims to analyze the existing literature investigating respiratory functioning in people with Persistent Somatic Symptoms (PSS) compared to healthy controls, to identify patterns of respiratory disturbances by symptom or syndrome, and describe any respiratory outcomes consistent across diagnoses.

METHODS

A systematic review following PRISMA guidelines was conducted. A comprehensive search was carried out across five databases (PubMed (NCBI), PsycArticles (Ovid), Web of Science (Core Collection), Embase, and Scopus) using two customised search strings for persistent somatic symptoms and objective respiratory parameters. Title/abstract screening and data extraction were carried out independently by two reviewers. The modified Newcastle-Ottawa Scale was used for quality assessment of the studies. Studies investigating baseline respiratory functioning in adult patients with PSS compared to healthy controls, using at least one objective respiratory were included.

RESULTS

18 studies met the inclusion criteria for the review, with a pooled sample size of n = 3245. Chronic pain conditions were found to be the most prevalent subset of diagnoses of interest, comprising six of the studies. 10 studies included measures of lung capacity, flow and/or volume, nine studies reported measures of ventilation, and four studies investigated respiratory muscle functioning. 13 of the included studies reported significant differences in at least one objective respiratory measure between groups (at rest). Scores on self-reported measures of dysnpea and breathlessness were higher in patients compared to healthy controls, while objective respiratory outcomes were varied.

CONCLUSION

The current systematic review is consistent with previous literature suggesting more pronounced experiences of breathlessness in patients with PSS, and significant disparities between reported dyspnea and objective respiratory outcomes. Research investigating the uncoupling between subjective and objective respiratory outcomes is needed to understand the mechanisms behind breathing disturbances in PSS.

Respiratory psychophysiology and COVID-19: A research agenda

After multiple waves of the COVID-19 pandemic, it has become clear that the impact of SARS-CoV-2 will carry on for years to come. Acutely infected patients show a broad range of disease severity, depending on virus variant, vaccination status, age and the presence of underlying medical and physical conditions, including obesity. Additionally, a large number of patients who have been infected with the virus present with post-COVID syndrome. In September 2020, the International Society for the Advancement of Respiratory Psychophysiology organized a virtual interest meeting on 'Respiratory research in the age of COVID-19', which aimed to discuss how research in respiratory psychophysiology could contribute to a better understanding of psychophysiological interactions in COVID-19. In the resulting current paper, we propose an interdisciplinary research agenda discussing selected research questions on acute and long-term neurobiological, physiological and psychological outcomes and mechanisms related to respiration and the airways in COVID-19, as well as research questions on comorbidity and potential treatment options, such as physical rehabilitation.

Treating breathlessness via the brain: changes in brain activity over a course of pulmonary rehabilitation

Breathlessness in chronic obstructive pulmonary disease (COPD) is often discordant with airway pathophysiology ("over-perception"). Pulmonary rehabilitation profoundly affects breathlessness, without influencing lung function. Learned associations influence brain mechanisms of sensory perception. We hypothesised that improvements in breathlessness with pulmonary rehabilitation may be explained by changing neural representations of learned associations.In 31 patients with COPD, we tested how pulmonary rehabilitation altered the relationship between brain activity during a breathlessness-related word-cue task (using functional magnetic resonance imaging), and clinical and psychological measures of breathlessness.Changes in ratings of breathlessness word cues positively correlated with changes in activity in the insula and anterior cingulate cortex. Changes in ratings of breathlessness-anxiety negatively correlated with activations in attention regulation and motor networks. Baseline activity in the insula, anterior cingulate cortex and prefrontal cortex correlated with improvements in breathlessness and breathlessness-anxiety.Pulmonary rehabilitation is associated with altered neural responses related to learned breathlessness associations, which can ultimately influence breathlessness perception. These findings highlight the importance of targeting learned associations within treatments for COPD, demonstrating how neuroimaging may contribute to patient stratification and more successful personalised therapy.

Medical and Psychiatric Causes of Episodic Vestibular Symptoms

Dizziness and vertigo are among the most common presenting patient complaints in ambulatory settings. Specific vestibular causes are often not immediately identifiable. The first task of the clinician is to attempt to rule in specific vestibular disorders, such as benign paroxysmal positional vertigo through physical examination, diagnostic testing, and history taking. A large proportion of patients with dizziness and vertigo will not be easily classified or confirmed as having a specific vestibular cause. As with any undifferentiated patient, the focus in this setting is to attempt to exclude serious or threatening causes.

Negative mood and alcohol problems are related to respiratory dynamics in young adults

This study examined the relationship of negative affect and alcohol use behaviors to baseline respiration and respiratory response to emotional challenge in young adults (N = 138, 48 % women). Thoracic-to-abdominal ratio, respiratory frequency and variability, and minute volume ventilation were measured during a low-demand baseline task, and emotional challenge (viewing emotionally-valenced, emotionally-neutral, and alcohol-related pictures). Negative mood and alcohol problems principal components were generated from self-report measures of negative affect and mood, alcohol use, and use-related problems. The negative mood component was positively related to a thoracic bias when measured throughout the study (including baseline and picture exposure). There was generally greater respiratory activity in response to the picture cues, although not specifically in response to the content (emotional or alcohol-related) of the picture cues. The alcohol problems component was positively associated with respiratory reactivity to picture cues, when baseline breathing patterns were controlled. Self-report arousal data indicated that higher levels of negative mood, but not alcohol problems, were associated with greater arousal ratings overall. However, those with alcohol problems reported greater arousal to alcohol cues, compared to emotionally neutral cues. These results are consistent with theories relating negative affect and mood to breathing patterns as well as the relationship between alcohol problems and negative emotions, suggesting that the use of respiratory interventions may hold promise for treating problems involving negative affect and mood, as well as drinking problems.

Feeling lightheaded: the role of cerebral blood flow

OBJECTIVE

The main aims of this study were a) to investigate the relationship between lightheadedness and cerebral blood flow velocity (CBFv) during hyperventilation-induced hypocapnia, and b) to investigate whether and why the relationship between lightheadedness and CBFv may change after several episodes of this sensation.

METHODS

Three hypocapnic and three normocapnic overbreathing trials were administered in a semirandomized order to healthy participants (N = 33). Each type of breathing trial was consistently paired with one odor. Afterward, participants were presented each odor once in two spontaneous breathing and in two normocapnic overbreathing trials. CBFv in the right middle cerebral artery was measured by transcranial Doppler ultrasonography (TCD). Also breathing behavior and self-reported lightheadedness were measured continuously. Each trial was followed by a symptom checklist.

RESULTS

Self-reported lightheadedness was closely related to changes in CBFv in the hypocapnic overbreathing trials. During the subsequent normocapnic trials, however, participants experienced more lightheadedness and "feeling unreal" to the odor that had previously been paired with hyperventilation-induced hypocapnia. These complaints were not accompanied by changes in end-tidal CO(2) nor in CBFv.

CONCLUSIONS

The results show that lightheadedness is associated with changes in CBFv but that after a few episodes, the underlying mechanism for this symptom may shift to perceptual-cognitive processes. These findings may help to understand why lightheadedness occurs during emotional distress and panic. In addition, altered cerebral blood flow is unlikely to play a primary precipitating role in recurrent symptoms of lightheadedness.

Respiratory, autonomic, and experiential responses to repeated inhalations of 20% CO₂ enriched air in panic disorder, social phobia, and healthy controls

Inhalation of carbon dioxide (CO₂) enriched air triggers anxiety in panic disorder (PD) patients, which is often interpreted as a sign of biological vulnerability. However, most studies have not measured respiration in these tasks. We compared patients with PD (n=20) and social phobia (SP, n=19) to healthy controls (n=18) during eight inhalations of 20% CO₂, preceded and followed by two inhalations of room air, while continuously measuring subjective anxiety and dyspnea as well as autonomic and respiratory variables. PD patients showed increased reactivity and delayed recovery during CO₂ inhalations for most measures. Unlike both other groups, the PD group's tidal volume responses did not habituate across CO₂ inhalations. However, PD patients did not differ from SP patients on most other measures, supporting a continuum model of CO₂ sensitivity across anxiety disorders. Both patient groups showed continued reactivity during the last air inhalations, which is unlikely to be due to a biological sensitivity.

Resistance to extinction in an odor-20% CO2 inhalation paradigm: further evidence for a symptom learning account of multiple chemical sensitivity

OBJECTIVE

Multiple chemical sensitivity (MCS) is characterized by a variety of symptoms in response to nontoxic concentrations of chemicals. To further test a laboratory model of MCS based on symptom learning, we used a stronger respiratory challenge in this study than in previous studies to induce symptoms (20% CO(2)-enriched air, unconditioned stimulus). Additionally, extinction of learned symptoms was investigated.

METHODS

Diluted ammonia (AM) and butyric acid (BA) served as conditioned (odor) stimuli (CSs). In a learning phase, healthy participants received three breathing trials of BA mixed with CO(2) and three trials of AM mixed with regular air, or the reversed combination. In a test phase, the same trials were administered without CO(2). Immediately after odor onset, participants rated their anxiety and expectancy to experience symptoms during that trial. Self-reported symptoms were assessed after each trial; respiratory behavior was measured throughout the experiment.

RESULTS

Only participants who learned to correctly anticipate symptoms (learning phase) reported elevated symptoms in response to the CS+ odor (test phase). Anticipation was more likely correct and learned symptoms were more elevated when BA had been previously associated with CO(2). Across test trials, anticipatory anxiety diminished, but learned symptoms did not. Participants failing to learn the prearranged contingencies reported overall more symptoms and anxiety.

CONCLUSIONS

Strong respiratory challenges impede extinction of learned symptoms. Conscious expectancy, which may be modulated by odor quality, determines whether learned symptoms develop in response to a specific odor or to the general context. The results further support a symptom learning account of MCS.

Evidence for a specific link between the personality trait of absorption and idiopathic environmental intolerance

Absorption as a personality trait refers to the predisposition to get deeply immersed in sensory (e.g., smells, sounds, pictures) or mystical experiences, that is, to experience altered states of consciousness. Absorption is markedly related to constructs openness to experiences, hypnotic suggestibility, imagination, and dissociation. Although absorption was hypothesized to be a risk factor for medically unexplained symptoms (MUS), the construct has yet not been investigated in individually suffering from idiopathic environmental intolerance (IEI), formerly better known as multiple chemical sensitivity (MCS). IEI is a complex condition marked by MUS, which patients attribute to various chemical substances that are typically detectable by their odor (e.g., exhaust emissions, cigarette smoke). The current study investigated whether IEI was related to the personality trait of absorption. In a longitudinal study, 54 subjects with IEI were compared to 44 subjects with a somatoform disorder (SFD), but without IEI, and 54 subjects with neither SFD nor IEI (control group, CG). Self-report measures of somatic symptoms, severity of IEI, and level of absorption were collected both at a first examination and 32 mo later. On both assessments, subjects with IEI and individuals with SFD reported similar highly elevated levels of MUS, compared to CG. In contrast to SFD, IEI was specifically related to elevated absorption scores. IEI was specifically associated with a tendency to experience self-altering states of consciousness. Since absorption is related to both openness to unusual experiences and elevated imaginative involvement, absorption might contribute to IEI via two routes by (1) enhancing the susceptibility for IEI-specific convictions and (2) fostering classical conditioning processes of MUS via enhanced cognitive-imaginative representations of assumed IEI triggers.

Trauma experience in individuals with idiopathic environmental intolerance and individuals with somatoform disorders

OBJECTIVE

Results from previous studies suggest that past trauma experience increases the risk for medically unexplained somatic symptoms and somatoform disorders (SFD). This cross-sectional study examined the link between various lifetime traumas, idiopathic environmental intolerance (IEI), and SFD.

METHODS

Two clinical groups of 54 subjects with IEI and 44 subjects with SFD were compared to 54 subjects (comparison group, CG) free from both IEI and SFD regarding self-reported traumas. The subjects were mainly recruited via advertisements in local newspapers. From 970 individuals screened for IEI and multiple somatic symptoms, 152 were included through a two-step selection procedure consisting of screening questionnaires, a medical examination, and structured interviews for IEI and mental disorders.

RESULTS

In all three groups at least one potential traumatic event was reported rather frequently (CG: 70%; IEI: 82%; SFD: 73%). But contrary to our expectation, significant group differences were neither found in regard to the proportion of subjects with any trauma, nor traumas fulfilling DSM-IV criteria (CG: 41%; IEI: 48%; SFD: 59%), nor multiple traumas (CG: 43%, IEI: 56%, SFD: 39%). Only two trauma categories were endorsed more frequently by the two clinical groups than by the CG: the unspecified 'other' category (IEI, SFD>CG) and 'life-threatening illness' (IEI>CG).

CONCLUSION

No clear evidence was found for increased rates of trauma experience in IEI and SFD. However, the results of this exploratory study should be considered as preliminary. Comparing larger IEI and SFD groups with a representative population-based sample may yield different results.

Multiple chemical sensitivities: review

PURPOSE OF REVIEW

There have been a number of recent studies examining behavioural and social factors in the potential cause of Multiple Chemical Sensitivities, or Idiopathic Environmental Intolerance. The current review will draw together recent research and suggest directions for future investigation.

RECENT FINDINGS

Recent studies have implicated a number of different perspectives which may be helpful in understanding the cause of chemical sensitivities. A multifactorial model incorporating behavioural, physiological and sociological approaches may be useful. Cultural and historical factors, alongside individual expectations and beliefs, as well as maladaptive learning and conditioning processes, may be important in the specific cause of chemical sensitivities. Iatrogenesis, through the promise of unproven 'therapies', may perpetuate reported symptoms further. Although there are many recent experiments implicating potential behavioural or psychological causes for Multiple Chemical Sensitivities, there remains a paucity of treatment trials for this condition.

SUMMARY

Good-quality treatment trials examining psychological/behavioural approaches in the management of Multiple Chemical Sensitivities are urgently needed.