Respiratory sensations in asthma: physiological and clinical implications

Age-related changes in the neural gating of respiratory sensations in humans

Background

Neural gating of respiratory sensations (NGRS) characterises the brain's ability to filter out repetitive respiratory sensory stimuli. This mechanism plays a crucial role in the neural processing of respiratory stimuli. However, whether ageing affects NGRS in healthy adults is still unclear. Therefore, we aimed to measure the effect of age on NGRS as well as the corresponding S1 and S2 components of the respiratory-related evoked potentials (RREPs).

Methods

Three age groups of healthy adults participated in this study: a young group (YG; age 20-39 years), a middle-aged group (MG; age 40-59 years) and an old group (OG; age ≥60 years). NGRS was measured by the RREPs in the electroencephalogram in response to short-paired respiratory occlusion stimuli (S1 and S2). The S2/S1 ratio of the RREP N1 amplitude (the negative deflection of the RREP at ∼85-135 ms) was used to characterise NGRS.

Results

The results showed a significantly smaller N1 S2/S1 ratio in the YG than in the MG (p=0.01) and OG (p=0.03). Further analysis showed that the S1 N1 amplitude was larger for the YG compared with the MG (p=0.03) and OG (p=0.007). Moreover, age was significantly correlated with the N1 S2/S1 ratio (r=0.43), with higher age relating to higher N1 S2/S1 ratios.

Conclusions

The greater N1 S2/S1 ratios observed in older adults suggest that ageing has a negative impact on the NGRS. This might contribute to increased experiences of respiratory sensations such as dyspnoea in ageing adults.

Associations of symptoms of anxiety and depression with health-status, asthma control, dyspnoea, dysfunction breathing and obesity in people with severe asthma

BACKGROUND

Anxiety and depression are comorbidities of severe asthma. However, clinical characteristics associated with coexisting severe asthma and anxiety/depression are poorly understood. The study objective is to determine clinical characteristics associated with anxiety and depressive symptoms in severe asthma.

METHODS

Severe asthma participants (N = 140) underwent a multidimensional assessment. Categorization of symptoms of anxiety and depression were based on HADS scale sub-scores and divided into four groups (< 8 on both subscales; ≥ 8 on one subscale; ≥ 8 on both subscales). Clinical characteristics were compared between subgroups. Multivariate logistic regression determined associations of clinical characteristics and anxiety and/or depressive symptoms in people with severe asthma.

RESULTS

Participants were (mean ± SD) 59.3 ± 14.7 years old, and 62% female. There were 74 (53%) severe asthma participants without symptoms of anxiety/depression, 11 (7%) with symptoms of anxiety, 37 (26%) with symptoms of depression and 18 (13%) with symptoms of anxiety and depression. Quality of life impairment was greater in participants with symptoms of depression (4.4 ± 1.2) and combined symptoms of anxiety and depression (4.4 ± 1.1). Asthma control was worse in those with symptoms of depression (2.9 ± 1.1) and combined anxiety and depression (2.6 ± 1.0). In multivariate models, dysfunctional breathing was associated with symptoms of anxiety (OR = 1.24 [1.01, 1.53]). Dyspnoea was associated with symptoms of depression (OR = 1.90 [1.10, 3.25]). Dysfunctional breathing (OR 1.16 [1.04, 1.23]) and obesity (OR 1.17 [1.00, 1.35]) were associated with combined symptoms of anxiety and depression.

CONCLUSION

People with severe asthma and anxiety and/or depressive symptoms have poorer QoL and asthma control. Dyspnoea, dysfunctional breathing and obesity are associated with these symptoms. These key clinical characteristics should be targeted in severe asthma management.

Dyspnea

The clinical term dyspnea (a.k.a. breathlessness or shortness of breath) encompasses at least three qualitatively distinct sensations that warn of threats to breathing: air hunger, effort to breathe, and chest tightness. Air hunger is a primal homeostatic warning signal of insufficient alveolar ventilation that can produce fear and anxiety and severely impacts the lives of patients with cardiopulmonary, neuromuscular, psychological, and end-stage disease. The sense of effort to breathe informs of increased respiratory muscle activity and warns of potential impediments to breathing. Most frequently associated with bronchoconstriction, chest tightness may warn of airway inflammation and constriction through activation of airway sensory nerves. This chapter reviews human and functional brain imaging studies with comparison to pertinent neurorespiratory studies in animals to propose the interoceptive networks underlying each sensation. The neural origins of their distinct sensory and affective dimensions are discussed, and areas for future research are proposed. Despite dyspnea's clinical prevalence and impact, management of dyspnea languishes decades behind the treatment of pain. The neurophysiological bases of current therapeutic approaches are reviewed; however, a better understanding of the neural mechanisms of dyspnea may lead to development of novel therapies and improved patient care.

Insights into how Malaysian adults with limited health literacy self-manage and live with asthma: A Photovoice qualitative study

BACKGROUND

Adjusting to life with a chronic condition is challenging, especially for people with limited health literacy, which is associated with low compliance with self-management activities and poor clinical outcomes.

OBJECTIVE

We explored how people with limited health literacy understand asthma and undertake self-management practices.

DESIGN

We adapted the arts-based qualitative methodology Photovoice.

SETTING AND PARTICIPANTS

We sampled ethnically diverse adults with asthma and limited health literacy from four primary healthcare clinics in Malaysia. After a semistructured in-depth interview, a subset of participants took part in the Photovoice component in which participants undertook a 2-week photo-taking activity and subsequent photo-interview. Interviews, conducted in participants' preferred language, were audio-recorded, transcribed verbatim, translated and analysed thematically. We used the Sorensen's framework (Domains: access, understand, appraise, apply) to describe participants' experience of living with asthma, what they understood about asthma and how they decided on self-management practices.

RESULTS

Twenty-six participants provided interviews; eight completed the Photovoice activities. Participants with limited health literacy used various sources to access information about asthma and self-management. Doctor-patient communication had a pivotal role in helping patients understand asthma. The lack of appraisal skills was significant and experiential knowledge influenced how they applied information. Self-management decisions were influenced by sociocultural norms/practices, stigmatizing experiences, and available social support.

CONCLUSION

Locally tailored multilevel interventions (interpersonal, health system, community and policy) will be needed to support people with limited health literacy to live optimally with their asthma in an ethnically diverse population.

PATIENT/PUBLIC CONTRIBUTION

Patients were involved in the study design, recruitment, analysis and dissemination.

Non-Contact Driver Respiration Rate Detection Technology Based on Suppression of Multipath Interference with Directional Antenna

Non-contact driver respiration rate detection is a challenging problem in the Internet of Vehicles, because the automobile environment is much narrower, and thus the multipath effect is greater. To overcome these challenges, a 2.4 GHz continuous wave forward-scattering radar respiratory detection system is proposed based on the theory that the radar cross-section (RCS) of the human body changes with human breathing. We also analyze the impact of the multipath effect in the vehicle on the received radar signal and compare the output signal captured by a directional antenna with that captured by an omnidirectional antenna in the proposed system. In addition, the mean value of the received signal’s envelope is used to judge whether the driver’s posture is reasonable. Finally, compared with the existing contact respiratory detection system, the actual test results demonstrate the effectiveness of the proposed FSR system, and the driver respiration rates obtained by the proposed system are consistent with those obtained by the contact respiratory detection system.

Heterogeneity of perception of symptoms in patients with asthma

Background

Cough-dominant or cough-variant asthma is common in Japan. However, it is unclear whether cough and dyspnea, the cardinal symptoms of bronchial asthma, are similarly perceived, and whether these symptoms are linked to pulmonary function tests.

Methods

The subjects were 548 physician-diagnosed naive patients with asthma. Visual analogue scale (VAS) scores were determined and spirometry was performed before and after 1-month inhaled corticosteroid/long-acting beta2 agonist therapy.

Results

The patients were divided into those with a significant bronchodilating response and an increase in FEV₁ (>12% and >200 mL) after treatment (n=146); and nonresponders without this response (n=402). Cough was more dominant than dyspnea in both groups at the initial evaluation. Both symptoms were diminished after treatment, but scores for cough remained significantly higher than those for dyspnea in nonresponders. VAS scores for dyspnea at both time points differed in responders and nonresponders, and changes of cough and dyspnea scores were larger in responders. In responders, peak expiratory flow (PEF) (absolute, %predicted) for cough and FEV₁ (%predicted), VC (%predicted) and PEF (absolute) for dyspnea were correlated at both time points, but in nonresponders, neither cough nor dyspnea was related to a common spirometric parameter at both time points. Changes in cough and dyspnea scores were correlated with changes of FEV₁ (absolute, %predicted) and FEF_25-75 (absolute) for responders, while only PEF (%predicted) was correlated with these changes in nonresponders. Calculated slopes (ΔVAS score/ΔFEV₁) suggested that responders were more sensitive to dyspnea than nonresponders.

Conclusions

Perception of cough and dyspnea were similar, but not identical, for bronchodilating responders and nonresponders among patients with bronchial asthma. Linkage of pulmonary function parameters with perceptions of cough and dyspnea also differed between the responders and nonresponders.

Still Fighting for Breath: a patient survey of the challenges and impact of severe asthma

We conducted a large global survey, Still Fighting for Breath, in patients with severe persistent asthma, 10 years after the Fighting for Breath survey to assess the impact of disease on patients' lives and to determine if control and management have changed in recent years.

Data were collected from 1333 adults (aged >18 years) and caregivers of children (aged 6–17 years) with severe persistent asthma from nine countries through an online survey conducted in 2016 by GfK.

A decade after the first survey, our results showed that the impact of severe asthma has not changed significantly and a high proportion of patients with severe asthma remain inadequately controlled. A large discrepancy was observed between the proportion of patients who perceived their asthma to be well controlled (42%) and the proportion of patients who reported to be well controlled as per the Global Initiative for Asthma (GINA) assessment (6%). Although most patients perceived their asthma to be controlled, many experienced frequent symptoms that affected their daily lives.

Thus, there is a need for improved management (support and strategies) of patients with severe persistent asthma and improved coordination of efforts that would enable these patients to achieve better disease control.

There is a need for improved management of patients with severe persistent asthma to achieve better disease controlhttp://ow.ly/rv5K30mQdGG

Chronic obstructive lung disease "expert system": validation of a predictive tool for assisting diagnosis

Purpose

The purposes of this study were development and validation of an expert system (ES) aimed at supporting the diagnosis of chronic obstructive lung disease (COLD).

Methods

A questionnaire and a WebFlex code were developed and validated in silico. An expert panel pilot validation on 60 cases and a clinical validation on 241 cases were performed.

Results

The developed questionnaire and code validated in silico resulted in a suitable tool to support the medical diagnosis. The clinical validation of the ES was performed in an academic setting that included six different reference centers for respiratory diseases. The results of the ES expressed as a score associated with the risk of suffering from COLD were matched and compared with the final clinical diagnoses. A set of 60 patients were evaluated by a pilot expert panel validation with the aim of calculating the sample size for the clinical validation study. The concordance analysis between these preliminary ES scores and diagnoses performed by the experts indicated that the accuracy was 94.7% when both experts and the system confirmed the COLD diagnosis and 86.3% when COLD was excluded. Based on these results, the sample size of the validation set was established in 240 patients. The clinical validation, performed on 241 patients, resulted in ES accuracy of 97.5%, with confirmed COLD diagnosis in 53.6% of the cases and excluded COLD diagnosis in 32% of the cases. In 11.2% of cases, a diagnosis of COLD was made by the experts, although the imaging results showed a potential concomitant disorder.

Conclusion

The ES presented here (COLD_ES) is a safe and robust supporting tool for COLD diagnosis in primary care settings.

Illness Experience, Self-Determination, and Recreational Activities in Pediatric Asthma

Although asthma self-management depends on ongoing and accurate self-assessment by the patient, pediatric asthma patients have weak skills in the area of symptom perception. Before developing an asthma game targeted to improving asthma self-management and improved symptom awareness, we sought to identify gaps in existing games. To clarify the role of relatedness and autonomy in asthma health game design, we investigated symptom awareness, vocabulary, and self-determination through a series of semi-structured interviews with children suffering from asthma. Using self-determination theory as a framework, interviews were oriented to patients' illness experience and vocabulary related to symptomatology, as well as to recreational activities. Formative analysis of the interviews reveals attitudes, perceptions, and motivational factors arising in the context of childhood asthma, and it elucidates the images and vocabulary associated with both illness experience and recreational activities. Qualitative assessment of patient perspectives leads to specific recommendations for game design ideas that will support market entry of a spirometer-controlled game for children with asthma.

Diagnosis of asthma - new theories

INTRODUCTION

Recent studies have shown a remarkably high frequency of poorly controlled asthma. Several reasons for this treatment failure have been discussed, however, the basic question of whether the diagnosis is always correct has not been considered. Follow-up studies have shown that in many patients asthma cannot be verified despite ongoing symptoms. Mechanisms other than bronchial obstruction may therefore be responsible. The current definition of asthma may also include symptoms that are related to mechanisms other than bronchial obstruction, the clinical hallmark of asthma.

AIM

Based on a review of the four cornerstones of asthma - inflammation, hyperresponsiveness, bronchial obstruction and symptoms - the aim was to present some new aspects and suggestions related to the diagnosis of adult non-allergic asthma.

CONCLUSION

Recent studies have indicated that "classic" asthma may sometimes be confused with asthma-like disorders such as airway sensory hyperreactivity, small airways disease, dysfunctional breathing, non-obstructive dyspnea, hyperventilation and vocal cord dysfunction. This confusion may be one explanation for the high proportion of misdiagnosis and treatment failure. The current diagnosis, focusing on bronchial obstruction, may be too "narrow". As there may be common mechanisms a broadening to include also non-obstructive disorders, forming an asthma syndrome, is suggested. Such broadening requires additional diagnostic steps, such as qualitative studies with analysis of reported symptoms, non-effort demanding methods for determining lung function, capsaicin test for revealing airway sensory hyperreactivity, careful evaluation of the therapeutic as well as diagnostic effect of corticosteroids and testing of suggested theories.

Reliability and predictors of resistive load detection in children with persistent asthma: a multivariate approach

OBJECTIVE

Resistive load detection tasks enable analysis of individual differences in psychophysical outcomes. The purpose of this study was to determine both the reliability and predictors of resistive load detection in children with persistent asthma who completed multiple testing sessions.

METHODS

Both University of North Carolina (UNC) Charlotte and Ohio University institutional review boards approved the research protocol. The detection of inspiratory resistive loads was evaluated in 75 children with asthma between 8 and 15 years of age. Each child participated in four experimental sessions that occurred approximately once every 2 weeks. Multivariate analyses were used to delineate predictors of task performance.

RESULTS

Reliability of resistive load detection was determined for each child, and predictors of load detection outcomes were investigated in two groups of children: those who performed reliably in all four sessions (n = 31) and those who performed reliably in three or fewer sessions (n = 44). Three factors (development, symptoms, and compliance) accounted for 66.3% of the variance among variables that predicted 38.7% of the variance in load detection outcomes (Multiple R = 0.62, p = 0.004) and correctly classified performance as reliable or less reliable in 80.6% of the children, χ(2)(12) = 28.88, p = 0.004.

CONCLUSIONS

Cognitive and physical development, appraisal of symptom experiences, and adherence-related behaviors (1) account for a significant proportion of the interrelationships among variables that affect perception of airflow obstruction in children with asthma and (2) differentiate between children who perform more or less reliably in a resistive load detection task.

Effects of feedback on the perception of inspiratory resistance in children with persistent asthma: a signal detection approach

OBJECTIVE

Accurate perception of asthma episodes increases the likelihood that they will be managed effectively. The purpose of the study was to examine the effect of feedback in a signal detection task on perception of increased airflow obstruction in children with persistent asthma.

METHODS

The effect of feedback training on the perception of resistive loads was evaluated in 155 children with persistent asthma between 8 and 15 years of age. Each child participated in four experimental sessions that occurred approximately once every 2 weeks, an initial session followed by three training sessions. During the initial session, the threshold resistance to breathing was determined for each child. Subsequently, each child was randomly assigned to one of two resistive load training conditions in a signal detection paradigm: training with immediate performance feedback or training with no performance feedback.

RESULTS

The threshold resistance to breathing, determined in the initial session, was equivalent between groups. Children in the feedback condition discriminated more accurately between both the presence and the absence of increases in the resistance to breathing (206 [48] versus 180 [39] correct responses, p < .001), and differences over time between groups increased reliably as a function of training (165 [40] versus 145 [32] correct responses, p < .001). Response times and confidence ratings were equivalent between groups, and no differences in breathing patterns were observed between conditions.

CONCLUSIONS

Feedback training results in improved perception of respiratory sensations in children with asthma, a finding with implications for strategies of asthma self-management.

Respiratory muscle tension as symptom generator in individuals with high anxiety sensitivity

OBJECTIVE

Anxiety and panic are associated with the experience of a range of bodily symptoms, in particular unpleasant breathing sensations (dyspnea). Respiratory theories of panic disorder have focused on disturbances in blood gas regulation, but respiratory muscle tension as a source of dyspnea has not been considered. We therefore examined the potential of intercostal muscle tension to elicit dyspnea in individuals with high anxiety sensitivity, a risk factor for developing panic disorder.

METHODS

Individuals high and low in anxiety sensitivity (total N=62) completed four tasks: electromyogram biofeedback for tensing intercostal muscle, electromyogram biofeedback for tensing leg muscles, paced breathing at three different speeds, and a fine motor task. Global dyspnea, individual respiratory sensations, nonrespiratory sensations, and discomfort were assessed after each task, whereas respiratory pattern (respiratory inductance plethysmography) and end-tidal carbon dioxide (capnography) were measured continuously.

RESULTS

In individuals with high compared to low anxiety sensitivity, intercostal muscle tension elicited a particularly strong report of obstruction (M=5.1, SD=3.6 versus M=2.5, SD=3.0), air hunger (M=1.9, SD=2.1 versus M=0.4, SD=0.8), hyperventilation symptoms (M=0.6, SD=0.6 versus M=0.1, SD=0.1), and discomfort (M=5.1, SD=3.2 versus M=2.2, SD=2.1) (all p values<.05). This effect was not explained by site-unspecific muscle tension, voluntary manipulation of respiration, or sustained task-related attention. Nonrespiratory control sensations were not significantly affected by tasks (F<1), and respiratory variables did not reflect any specific responding of high-Anxiety Sensitivity Index participants to intercostal muscle tension.

CONCLUSIONS

Respiratory muscle tension may contribute to the respiratory sensations experienced by panic-prone individuals. Theories and treatments for panic disorder should consider this potential source of symptoms.

Diagnosis of asthma - a new approach

Current definition of asthma involves four cornerstones: inflammation, hyperresponsiveness, bronchoconstriction, and symptoms. In research, the symptoms have had the slightest attention. According to international guidelines, the asthma symptoms are episodic breathlessness, wheeze, cough, tightness of the chest, and shortness of breath. As there are several symptoms, a primary question is how they are related to bronchoconstriction, the main clinical feature of asthma. Symptoms and lung function tests are regularly used for the evaluation of clinical health status and effect of treatment. However, there is no or poor correlation between these two variables, which means that they represent different mechanisms. Reduced lung function, such as a low FEV(1) , represents bronchial constriction, what do the symptoms represent? Some symptoms such as breathlessness and shortness of breath seem not to be evidence-based asthma symptoms. Focusing on bronchial obstruction is important in view of the potential risk of asthma attacks, but nonobstructive symptoms occur frequently and may also cause severe discomfort and poor quality of life. Interpreting all symptoms as signs of bronchoconstriction (asthma) may lead to misinterpretation when assessing health status and effect of treatment. Although a 'soft' variable, the strength of symptoms is that they are representing various mechanisms. The physiological preconditions for control and defense of respiration must be considered in the diagnostic process, regardless of inflammation, allergy, psychology, or other etiological factors. Based on studies on dyspnea in cardiopulmonary diseases, including asthma and asthma-like disorders, there seems to be a continuous spectrum of symptoms and mechanisms integrated in a single asthma syndrome.

Descriptors of dyspnea in obstructive lung diseases

In obstructive lung diseases such as asthma and COPD dyspnea is a common respiratory symptom with different characteristics given the different pathogenic mechanisms: in COPD initially it can occur during exertion but then it increases progressively along with the airflow obstruction, whereas in asthma it occurs episodically and is caused by transient bronchoconstriction.The language of dyspnea includes a large range of clinical descriptors which have been evaluated for their correlation (of one or several descriptors) with underlying physiologic/physiopathologic mechanisms. These studies were done in asthma rather than in COPD, and dyspnea descriptors were found to be useful in identifying patients with life-threatening asthma. However further studies are needed to further explore such descriptors and their clinical utility.This review discusses dyspnea mechanisms in various obstructive lung disease subsets as well as the descriptors of dyspnea and their utility in clinical practice.

Perception of breathlessness by a 3-minute respiratory exerciser test predicts asthma exacerbations: a prospective cohort study

We prospectively evaluated the use of a simple 3-Minute Respiratory Exerciser Test (3MRET) that estimates perception of dyspnea to identify patients at risk of asthma exacerbations. A total of 146 stable asthmatics (42 under-perceivers, 69 normal perceivers, and 35 over-perceivers) received follow-up for 12 months. The mean (SD) unscheduled visits to doctors among under-, normal, and over-perceivers were 1.8 (1.2), 2.2 (1.8), and 3.1 (2.3), respectively (p = 0.008). The mean (SD) hospital admissions among the groups were 1.3 (0.5), 1.2 (0.6), and 1.7 (1.3), respectively (p = 0.026). Compared to normal perceivers, over-perceivers had increased risks of unscheduled visits (OD: 5.12; 95% CI = 1.59 to 16.47) and hospital admissions (OD: 0.31; 95% CI = 0.23 to 0.41), defined as > or =2 events in 12 months. The association between over-perceiver and unscheduled visits remained significant after adjusting for forced expiratory volume in 1 second (FEV(1)). Sensitivity and specificity of over-perceivers are 77% and 47%, respectively, for unscheduled visits and 37% and 78%, respectively, for hospital admissions, with significantly better area under ROC for unscheduled visits (0.67 [95% CI = 0.56 to 0.77]; p = 0.003) than for hospital admissions (0.58 [0.471 to 0.70]; p = 0.127). We conclude that the 3MRET may have a role in identifying asthmatic patients with over-perception of dyspnea at risk of clinically important asthma exacerbations.

Perception of dyspnea during acetylcholine-induced bronchoconstriction in asthmatic children

BACKGROUND

Few studies have examined the relationship between dyspnea perception and bronchial hyperresponsiveness (BHR) in asthmatic children.

OBJECTIVE

To test the hypothesis that severe BHR is associated with poor perception of the severity of airway obstruction.

METHODS

One hundred one asthmatic children (mean [SD] age, 11.1 [2.3] years) were evaluated using acetylcholine chloride (Ach) challenge. The BHR was assessed as the provocative concentration of Ach causing a 20% decrease in forced expiratory volume in 1 second (FEV1) (PC20). Perception of dyspnea was scored using a modified Borg scale after each dose of Ach and bronchodilator. The dyspnea threshold was defined as the point at which the Borg scale score became higher than 0. We evaluated the dyspnea perception score at a 20% decrease in FEV1 relative to baseline (PS20) and after bronchodilator administration (PS(BD)).

RESULTS

The mean (SD) PS20 and PS(BD) were significantly lower in the severe vs the mild BHR group (PS20: 2.1 [1.9] vs 4.2 [2.4], P < .001; PS(BD): 0.5 [1.0] vs 1.0 [1.3], P = .048). The mean (SD) % decrease in FEV1 at the dyspnea threshold was significantly greater in the severe vs the mild BHR group (14.1% [11%] vs 5.4% [11%], P < .001). The PS20 was correlated positively with the PC20 (r2 = 0.25, P < .001), and the decrease in FEV1 at the dyspnea threshold was correlated negatively with the PC20 (r2 = 0.18, P < .001).

CONCLUSIONS

Moderate to severe asthmatic children with severe BHR perceive dyspnea only after the stage of mild bronchoconstriction has passed. This relative insensitivity to dyspnea in asthmatic children with severe BHR may lead to undertreatment of asthma.

Descriptors and perception of dyspnea in African-American asthmatics

OBJECTIVE

This study explores self-reported perception of asthma symptoms in African-Americans.

METHODS

Qualitative methodology was used to analyze the responses from African-Americans within focus groups from Nashville, Tennessee.

RESULTS

Common symptoms were chest tightness, "breathing problems," and wheeze. Less commonly reported symptoms included cough, chest pain, dizziness, sweating, and "short of breath." A single participant reported nocturnal wheezing.

CONCLUSIONS

This study provides insight into the descriptors and perception of asthma symptoms in African-Americans. Understanding the descriptors of symptoms and disease severity in African-American patients may lead to more accurate diagnosis, treatment, and reduced mortality within this high-risk population.

Adrenergic responsiveness: FEV1 and symptom differences in Whites and African Americans with mild asthma

Decision-making about inhaler use is, in part, determined by the ability of asthmatic patients to compare their symptoms over time and to recall the previous response to the bronchodilator during an episode of asthma. The perception of airway symptoms across varied ethnic and cultural groups are poorly understood. Study purpose was (1) to determine if African Americans and Whites with mild asthma could accurately perceive bronchodilation and (2) to identify the word descriptors they used to describe their breathing. Sixteen African American and 16 White patients (34.5 +/- 9.7 years old, mean+/-SD) with mild atopic asthma (FEV1 > or =70% predicted normal) were given increasing doses of an inhaled bronchodilator (Albuterol) after a methacholine challenge. Albuterol (180 microg) was given, by spacer, at 15 min intervals until the FEV1 increased < 5%. Borg, VAS, and Word Descriptors were collected at baseline and after each dose of Albuterol. Baseline FEV1 after Methacholine provocation was 1.94 +/- .39 L for African Americans and 2.13 +/- .70 L for Whites. After 180 microg and again after 360 microg Albuterol, FEV1 increased to 2.88 +/- 0.48 L for African Americans and 3.37 +/- 0.91 L for Whites. But after 540 microg Albuterol, FEV1 decreased significantly (16%) to 2.42 +/- 1.19 L for African Americans while increasing only slightly to 3.47 +/- 0.95 L for Whites. After this dose, 10/16 African Americans felt "tight at the base of throat" (p < 0.01); 7/16 felt "speech-voice-tight" (p < 0.03) suggesting persistent airway discomfort despite marked improvement in FEV1, Borg and VAS scores compared with baseline values. Word descriptors by African Americans' are a more reliable measure of airway symptoms compared to FEV1, Borg or VAS.

Acute severe asthma

Acute severe asthma remains a major economic and health burden. The natural history of acute decompensations is one of resolution and only about 0.4% of patients succumb overall. Mortality in medical intensive care units is higher but is less than 3% of hospital admissions. "Near-fatal" episodes may be more frequent, but precise figures are lacking. However, about 30% of medical intensive care unit admissions require intubation and mechanical ventilation with mortality of 8%. Morbidity and mortality increase with socioeconomic deprivation and ethnicity. Seventy to 80% of patients in emergency departments clear within 2 hours with standardized care. The relapse rate varies between 7 and 15%, depending on how aggressively the patient is treated. The airway obstruction in the 20-30% of people resistant to adrenergic agonists in the emergency department slowly reverses over 36-48 hours but requires intense treatment to do so. Current therapeutic options for this group consist of ipratropium and corticosteroids in combination with beta2 selective drugs. Even so, such regimens are not optimal and better approaches are needed. The long-term prognosis after a near-fatal episode is poor and mortality may approach 10%.

Verbal descriptors of dyspnea in patients with COPD at different intensity levels of dyspnea

BACKGROUND

Verbal descriptors of dyspnea are important in understanding the underlying mechanisms, but little is known about the language of dyspnea in COPD. We examined the language of dyspnea in COPD at different intensity levels of dyspnea.

METHODS

Verbal descriptors of dyspnea were assessed in 64 patients with moderate-to-severe COPD (mean age, 62 years; mean percentage of predicted FEV(1) [FEV(1)%pred], 54.1%) during slight dyspnea at rest (mean Borg score, 1.8), moderate dyspnea during cycle ergometer exercise (mean Borg score, 3.1) and somewhat severe dyspnea during a 6-min walking test before (mean Borg score, 4.2), and after pulmonary rehabilitation (PR) [mean Borg score, 3.5]. Furthermore, the influence of age, gender, baseline lung function (FEV(1)%pred), and PR on the verbal descriptors were studied.

RESULTS

A cluster analysis showed that patients differentiated between five clusters of verbal descriptors of dyspnea: heavy/fast breathing, shallow breathing, obstruction, work/effort, and suffocation. These were related to the intensity level of dyspnea but not to age, gender, baseline lung function, or PR. While shallow breathing was predominant only during slight dyspnea at rest, heavy/fast breathing and to a lesser extent work/effort became more important during moderate and somewhat severe dyspnea during exercise. The clusters heavy/fast breathing and work/effort demonstrated the highest sensitivity in discriminating between different intensity levels of dyspnea and in characterizing the positive effects of PR.

CONCLUSIONS

Verbal descriptors of dyspnea in COPD are related to the intensity level of dyspnea. The clusters heavy/fast breathing and work/effort seem to be particularly sensitive descriptors of dyspnea during exercise in COPD.

Evidence for placebo effects on physical but not on biochemical outcome parameters: a review of clinical trials

BACKGROUND

Recent reviews on placebo effects in clinical trials suggest that objective changes following placebo treatments may not exist or, at least, have been considerably overestimated. However, the possibility that yet unidentified subsets of parameters are responsive to placebo treatments has not been taken into account. Therefore, the aim of the present study is to examine the effects of placebo treatments on objectively measured outcome parameters by specifically focusing on peripheral disease processes.

METHODS

An initial dataset was collected from a MEDLINE search for placebo-controlled, randomized clinical trials. Trials with stable disease conditions were identified, and the effects of placebo treatments on peripheral outcome parameters were estimated by the changes from baseline in the placebo groups. An explorative data analysis was conducted in order to identify parameter classes with differential responsiveness to placebo treatments. A subgroup meta-analysis of a second dataset was performed to test whether the preliminary classification would also apply to placebo effects derived from the comparison of placebo groups with untreated control groups.

RESULTS

The explorative analysis of outcome parameters and strength of placebo effects yielded a classification into responsive "physical" versus non-responsive "biochemical" parameters. In total, 50% of trials measuring physical parameters showed significant placebo effects, compared with 6% of trials measuring biochemical parameters. A subgroup meta-analysis substantiated the differential response (physical parameters: n = 14, Hedges' pooled effect size g = 0.34, 95% CI 0.22 to 0.46; biochemical parameters: n = 15, g = 0.03, 95% CI -0.04 to 0.10). The subanalysis of the second dataset supported the classification and revealed a significant improvement for physical parameters (n = 20, g = 0.22, 95% CI 0.07 to 0.36) and a deterioration for biochemical parameters (n = 6, g = -0.17, 95% CI -0.31 to -0.02).

CONCLUSION

The results suggest that placebo interventions can improve physical disease processes of peripheral organs more easily and effectively than biochemical processes. This differential response offers a good starting point for theoretical considerations on possible mediating mechanisms, and for future investigations in this field.

The influence of corticosteroids on the perception of dyspnea in asthma

Corticosteroids are effective anti-inflammatory medications that are recommended for the control of persistent asthma. Little, however, is known about their influence on the perception of dyspnea, which, in turn, is important to the successful self-management of asthma. This paper provides a synopsis of available studies examining the impact of corticosteroids on the sensitivity to perceive dyspnea and presents possible mechanisms underlying this relationship. The results of these investigations are conflicting with some studies showing improved perception and other studies showing worsened perception of dyspnea after corticosteroid treatment. Thus, firm conclusions cannot be derived from the currently available data. Implications for future research, which is required to increase our understanding of potential influences of corticosteroids on the perception of dyspnea, are provided.

Evaluation of a Respiratory Muscle Biofeedback Procedure–Effects on Heart Rate and Dyspnea

Patients with respiratory diseases or anxiety frequently complain about dyspnea, which may be partly related to chronic tension of respiratory muscles and/or dynamic hyperinflation. In two experiments we tested a biofeedback technique that recorded electromyographic (EMG) activity from a bipolar surface electrode placement over the right external intercostal muscles with visual signal feedback. Healthy participants were tested in their ability to alter the signal. Heart rate was measured continuously throughout training trials. In the second experiment, dyspnea was rated on a modified Borg scale after each trial. Participants were able to increase their EMG activity considerably while heart rate and dyspnea increased substantially. Changes in EMG activity were achieved mostly by manipulating accessory muscle tension and/or altering breathing pattern. Thus, the technique is capable of altering respiratory muscle tension and associated dyspnea. Further studies may test the procedure as a relaxation technique in patients with respiratory disease or anxiety.

Psychological aspects in the perception of dyspnea in obstructive pulmonary diseases

Dyspnea is an impairing symptom in obstructive pulmonary diseases. Besides multiple physiological pathways contributing to this sensation recent research has demonstrated an important role of psychological factors in the perception of dyspnea. The present review article synthesizes the research literature with regard to psychological aspects of the perception of dyspnea as well as other dyspnea-related issues such as course of disease, neuropsychological correlates and interventions that focus on psychological or behavioural changes. The available data show that inaccurate perception of dyspnea is related to poorer treatment outcome in obstructive pulmonary diseases and is impacted upon by emotional, attentional and learning processes. Neuropsychological deficits might further contribute to this association. Different psychological and behavioural interventions might reduce comorbid psychological disorders and thus improve the perception of dyspnea. However, future research is clearly required to substantiate current findings.

Disability and breathlessness in asthmatic patients--a scoring method by repetitive inspiratory effort

Measurement of disability and breathlessness in asthma is important to guide treatment. Using an incentive spirometer, Triflo II (Tyco Healthcare, Mansfield, MA, USA), we developed a three-minute respiratory exercise test (3-MRET) to score the maximal breathing capacity (MBC) and perception of dyspnea (POD) index by means of repetitive inspiratory efforts achieved within 3 minutes. POD index was calculated based on the ratio of breathlessness on visual analogue scale over MBC score. In 175 normal healthy subjects and 158 asthmatic patients of mild (n = 26), moderate (n = 78), and severe (n = 54), severity, the mean (95% CI) MBC scores in mild, moderate, and severe asthma patients were 168 (145-192), 153 (136-169), and 125 (109-142) respectively, and 202 (191-214) in normal subjects (p < 0.001). The mean POD index in mild, moderate, and severe asthma patients was 16 (9-23), 25 (14-37), and 57 (14-100), respectively, and 6 (4-7) in normal subjects (p < 0.001). Intraclass correlation coefficients for MBC score and POD index in 17 asthmatic and 20 normal subjects were high. In 14 asthmatic patients randomized to receiving nebulized beta2-agonist or saline in a cross-over, double-blind study, % forced expiratory volume in one second (FEV1) change correlated with % change in MBC score [r(s) = 0.49, p < 0.01] and POD index [r(s)-0.46, p = 0.012]. In 21 asthmatic and 26 normal subjects, the MBC score and POD index correlated with the walking distance and walking POD index of the six-minute walking test (6MWT). We conclude that 3MRET is discriminative between asthmatic patients of varying severity and normal subjects, is reproducible, is responsive to bronchodilator effect, and is comparable with 6MWT. Taken together, it has the potential to score disability and POD in asthma simply and effectively.

Cortical substrates for the perception of dyspnea

Dyspnea is a common, unpleasant, and impairing symptom in various respiratory diseases and other diseases. Despite growing understanding of the multiple peripheral mechanisms giving rise to dyspnea, little is known about the cortical mechanisms underlying its perception. The results of neuroimaging studies have shown that distinct brain areas process the dyspneic sensation, among which the anterior insular seems to be the most important. Based on the findings of the first relevant neuroimaging studies, this review describes the cortical structures associated with the perception of dyspnea. Moreover, similarities to the perception of pain are discussed, and implications for future research are provided.

Psychological implications of respiratory health and disease

The possibility that a subject's psychological status may influence respiratory sensations and that chronic respiratory disease may have psychological consequences has sparked great interest among clinicians and researchers. This paper reviews the existing research on the association between respiratory symptom perception and the psychological status and between chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease, and psychological disturbances. Moreover, it focuses on the role of stressful events in determining asthma exacerbations. The recent literature suggests that in patients with chronic respiratory diseases, the evaluation of breathlessness perception, psychological disturbances and the recording of any stressful events should be considered as relevant as the physical and functional assessment of respiration.

Severe exacerbations of asthma

All asthmatics regardless of their perceived severity, are at risk of exacerbation, particularly if they are suboptimally treated in the outpatient arena. Fortunately most patients recover after administration of bronchodilators and anti-inflammatory medications, but preventable deaths continue to occur and refractory cases result in hospitalization and need for mechanical ventilation. We begin this article by reviewing the pathophysiology of acute exacerbations to build a foundation for the assessment of clinical status and to provide the rationale for a carefully contemplated and evidence-based therapeutic approach. We end this article with an in-depth examination of the particular problems that are encountered during mechanical ventilation and offer a strategy that helps minimize complications. In the final analysis, however, the greatest gains in the field of acute asthma will come not from its treatment but from its prevention by enhanced educational and environmental efforts and by the delivery of optimal medications at home.

Symptom perception and respiratory sensation: clinical applications

This article has described symptom perception and its relation to asthma management. Underestimation of airway obstruction in persons with asthma is a common and serious problem that is linked to fatalities in persons with asthma. Strategies to identify and manage the poor perceiver have been suggested.

Assessment of breathlessness perception by Borg scale in asthmatic patients: reproducibility and applicability to different stimuli

In asthmatics, the score of bronchoconstriction-associated breathlessness at 20% fall in forced expiratory volume at first second (FEV1) evaluated on a Borg scale (PS20) is a tool successfully used to measure the perception of symptoms. This prospective laboratory study evaluated the applicability of PS20 to assess the breathlessness induced by ultrasonically nebulized distilled water (UNDW) and methacholine (M) and its reproducibility. Twenty-two mild and clinically stable asthmatic patients performed UNDW and M challenge tests. The PS20 was calculated by linear interpolation of the last two points of the perception/fall in FEV1 curve of the UNDW and M tests. The reproducibility of PS20 M was assessed by repeating measurements on 2 separate days by 3 weeks. PS20 UNDW and PS20 M did not differ and were respectively 1.82 +/- 1.85 and 2.03 +/- 1.86. They were significantly related (rs=0.63; p<0.01) and the bias between PS20 UNDW and PS20 M was -0.21 with the limits of agreement ranging from -3.2 to 3.6. The intraclass correlation coefficient for repeated measurement of PS20 M was 0.82; the bias between the two measurements was 0.2 with the limits of agreement ranging from -2.8 to 3.2. All patients had a measurable breathlessness perception degree on a Borg scale during both distilled water challenges and methacholine. Asthmatic patients with normal, exaggerated or poor breathlessness perception were also similar for both stimuli. In addition, PS20 showed a good reproducibility and this allows the serial evaluation of patient's breathlessness perception by this technique in clinical settings and in the physiology laboratory.

Respiratory sensation and ventilatory mechanics during induced bronchoconstriction in spontaneously breathing low cervical quadriplegia

Intensity of dyspnea during induced bronchoconstriction in asthma is strongly related to the reduction in inspiratory capacity (IC) as a result of dynamic hyperinflation. To determine the role of rib cage and intercostal muscle afferents in symptom perception during bronchoconstriction, we measured the relationship between dyspnea intensity and IC during induced bronchoconstriction in six subjects with complete C4-C7 quadriplegia who did not require assisted ventilation. Spirometry, lung volumes, breathing pattern, esophageal pressure (Pes), and dyspnea intensity (Borg Scale) were measured during high-dose methacholine bronchoprovocation up to 256 mg/ml or a maximum change (Delta) in FEV(1) of 50%. Contemporaneous control data from subjects with asthma (n = 12) who had completed the same protocol were used for comparison. At maximum response in quadriplegia, FEV(1) decreased by 1.42 +/- 0.18 L (62 +/- 4%predicted) (mean +/- SEM), and IC decreased by 0.89 +/- 0.12 L (30 +/- 4%predicted). Dyspnea at maximum response was rated "moderate" to "severe": Borg 3.6 +/- 0.3. The predominant qualitative respiratory sensations were inspiratory difficulty and unsatisfied inspiration. The best correlate of dyspnea (Borg) was DeltaIC(%predicted) (p < 0.0005), whereas changes in FEV(1), Pes-derived measurements and breathing pattern did not contribute further to the strength of this relationship. Dyspnea intensity, quality, and changes in spirometry and lung volumes at maximum response were similar to those reported previously in asthma. The relationship between dyspnea intensity and DeltaIC(%predicted) was linear and consistent across groups. We conclude that the quality and intensity of dyspnea during methacholine-induced bronchoconstriction and dynamic hyperinflation was not altered by extensive chest wall deafferentation.