Experimental pain augments experimental dyspnea, but not vice versa in human volunteers

Acupuncture for dyspnea and breathing physiology in chronic respiratory diseases: A systematic review and meta-analysis of randomized controlled trials

Background

Dyspnea, a common symptom of chronic respiratory diseases (CRDs), is closely linked to higher levels of functional impairment and death, leading to significant societal and financial challenges. Despite numerous clinical trials and systematic reviews suggested the potential benefits of acupuncture for chronic obstructive pulmonary disease (COPD) and lung cancer, there is currently insufficient evidence to conclusively prove its effectiveness in alleviating dyspnea in patients with CRDs.

Methods

To compile and evaluate the existing data on the effectiveness and safety of acupuncture for managing dyspnea in CRDs. Randomized controlled trials investigating acupuncture for the treatment of dyspnea in patients with CRDs, such as COPD, lung cancer, asthma, bronchiectasis, interstitial lung disease, chronic pulmonary heart disease and bronchitis, were searched and retrieved from five electronic databases in English or Chinese.

Results

A total of 23 studies meeting the inclusion criteria were found in databases, covering various CRDs such as COPD, lung cancer, and asthma. A meta-analysis that compared acupuncture to a control group (which included no acupuncture and sham acupuncture) found significant advantages for acupuncture in reducing dyspnea severity (P = 0.0003), increasing 6MWD (P < 0.00001), improving quality of life measured by St. George's Respiratory Questionnaire (P = 0.03) and karnofsky performance status score (P < 0.00001). No significance was found in breathing physiology represented by FEV1 (P = 0.34) and FVC (P = 0.15). There was a comparable incidence of negative outcomes in both groups (P = 0.07). Results were consistent when compared to sham acupuncture. In addition, subgroup analyses were also consistent when different diseases or types of acupuncture were analyzed.

Conclusions

Acupuncture may be an effective and safe non-pharmacological complementary intervention to relief dyspnea for patients with CRDs. Nevertheless, research with high quality and large sample sizes is needed for further investigation.

Comparing multimodal physiological responses to social and physical pain in healthy participants

Background

Previous physiology-driven pain studies focused on examining the presence or intensity of physical pain. However, people experience various types of pain, including social pain, which induces negative mood; emotional distress; and neural activities associated with physical pain. In particular, comparison of autonomic nervous system (ANS) responses between social and physical pain in healthy adults has not been well demonstrated.

Methods

We explored the ANS responses induced by two types of pain-social pain, associated with a loss of social ties; and physical pain, caused by a pressure cuff-based on multimodal physiological signals. Seventy-three healthy individuals (46 women; mean age = 20.67 ± 3.27 years) participated. Behavioral responses were assessed to determine their sensitivity to pain stimuli. Electrocardiogram, electrodermal activity, photoplethysmogram, respiration, and finger temperature (FT) were measured, and 12 features were extracted from these signals.

Results

Social pain induced increased heart rate (HR) and skin conductance (SC) and decreased blood volume pulse (BVP), pulse transit time (PTT), respiration rate (RR), and FT, suggesting a heterogeneous pattern of sympathetic-parasympathetic coactivation. Moreover, physical pain induced increased heart rate variability (HRV) and SC, decreased BVP and PTT, and resulted in no change in FT, indicating sympathetic-adrenal-medullary activation and peripheral vasoconstriction.

Conclusion

These results suggest that changes in HR, HRV indices, RR, and FT can serve as markers for differentiating physiological responses to social and physical pain stimuli.

Potential Explanatory Factors for the Concurrent Experience of Dyspnea and Pain in Patients with COPD

Previous research has identified unexpectedly strong associations between dyspnea and pain, but the reasons remain unclear. Ascertaining the underlying biological and psychological mechanisms might enhance the understanding of the experience of both conditions, and suggest novel treatments. We sought to elucidate whether demographic factors, disease severity, psychological symptoms and biomarkers might account for the association between pain and dyspnea in individuals with COPD. We analyzed data from 301 patients with COPD who were followed in a prospective longitudinal observational study over 2 years. Measures included self-reported dyspnea and pain, pulmonary function tests, serum levels of inflammatory cytokines, measures of physical deconditioning, and scales for depression and anxiety. Analyses involved cross-sectional and longitudinal linear regression models. Pain and dyspnea were strongly correlated cross-sectionally (r = 0.77, 95% CI 0.72-0.82) and simultaneously across time (r = 0.42, 95% CI 0.28-0.56). Accounting for any of the other health factors only slightly mitigated the associations. Symptoms of pain and dyspnea thus may be fundamentally linked in COPD, rather than being mediated by common biological, psychological, or functional factors. From the patient's perspective, pain and dyspnea may be part of the same essential experience. It is possible that treatments for one condition would improve the other.

Predictive Factors for the Development of Dyspnea Within 7 Days After Admission Among Terminally Ill Cancer Patients

BACKGROUND

Predictive factors for the development of dyspnea have not been reported among terminally ill cancer patients.

OBJECTIVE

This current study aimed to identify the predictive factors attributed to the development of dyspnea within 7 days after admission among patients with cancer.

METHODS

This was a secondary analysis of a multicenter prospective observational study on the dying process among patients admitted in inpatient hospices/palliative care units. Patients were divided into 2 groups: those who developed dyspnea (development group) and those who did not (non-development group). To determine independent predictive factors, univariate and multivariate analyses using the logistic regression model were performed.

RESULTS

From January 2017 to December 2017, 1159 patients were included in this analysis. Univariate analysis showed that male participants, those with primary lung cancer, ascites, and Karnofsky Performance Status score (KPS) of ≤40, smokers, and benzodiazepine users were significantly higher in the development group. Multivariate analysis revealed that primary lung cancer (odds ratio [OR]: 2.80, 95% confidence interval [95% CI]: 1.47-5.31; p = 0.002), KPS score (≤40) (OR: 1.84, 95% CI: 1.02-3.31; p = 0.044), and presence of ascites (OR: 2.34, 95% CI: 1.36-4.02; p = 0.002) were independent predictive factors for the development of dyspnea.

CONCLUSIONS

Lung cancer, poor performance status, and ascites may be predictive factors for the development of dyspnea among terminally ill cancer patients. However, further studies should be performed to validate these findings.

Behavioral and Regional Brain Responses to Inhalation of Capsaicin Modified by Painful Conditioning in Humans

BACKGROUND

Cough is a defense mechanism that protects the airways and lungs in response to airway irritation. The sensory neurons involved in detecting airway irritants and the neural pathways mediating cough share similarities with those that encode pain from the body. Painful conditioning stimuli applied to one body site are known to reduce the perception of pain at another. However, whether the neural regulation of cough is influenced by painful stimuli is not known.

RESEARCH QUESTION

What are the behavioral and neural outcomes of painful conditioning stimuli on urge-to-cough (UTC) and cough evoked by inhaled capsaicin?

STUDY DESIGN AND METHODS

Sixteen healthy participants underwent psychophysical testing and functional MRI while completing a series of capsaicin inhalations to induce UTC and cough. The responses associated with capsaicin inhalation without pain were compared with those after the application of painful conditioning stimuli.

RESULTS

Significant decreases were seen behaviorally of 18.7% ± 17.3% (P < .001) and 47.0% ± 30.8% (P < .001) in participants' UTC ratings and cough frequencies, respectively, during the application of pain. UTC ratings were reduced by 24.2% ± 36.5% (P < .005) and increased by 67% ± 40% (P < .001) for capsaicin and saline inhalation, respectively, during the scanning session. Painful conditioning stimuli were associated with widespread decreases in regional brain responses to capsaicin inhalation (P < .001). Several brain regions showed levels of reduced activation attributable to painful conditioning that correlated with related changes in behavioral responses during scanning (R² = 0.53).

INTERPRETATION

Pain-related decreases of cough and UTC are accompanied by widespread changes in brain activity during capsaicin inhalation, suggesting that pain can modify the central processing of inputs arising from the airways. A mechanistic understanding of how cough and pain processing interact within the brain may help develop more effective therapies to reduce unwanted coughing.

Motivational Non-directive Resonance Breathing as a Treatment for Chronic Widespread Pain

Chronic widespread pain (CWP) is one of the most difficult pain conditions to treat due to an unknown etiology and a lack of innovative treatment design and effectiveness. Based upon preliminary findings within the fields of motivational psychology, integrative neuroscience, diaphragmatic breathing, and vagal nerve stimulation, we propose a new treatment intervention, motivational non-directive (ND) resonance breathing, as a means of reducing pain and suffering in patients with CWP. Motivational ND resonance breathing provides patients with a noninvasive means of potentially modulating five psychophysiological mechanisms imperative for endogenously treating pain and increasing overall quality of life.

Predicting opioid dependence from electronic health records with machine learning

BACKGROUND

The opioid epidemic in the United States is averaging over 100 deaths per day due to overdose. The effectiveness of opioids as pain treatments, and the drug-seeking behavior of opioid addicts, leads physicians in the United States to issue over 200 million opioid prescriptions every year. To better understand the biomedical profile of opioid-dependent patients, we analyzed information from electronic health records (EHR) including lab tests, vital signs, medical procedures, prescriptions, and other data from millions of patients to predict opioid substance dependence.

RESULTS

We trained a machine learning model to classify patients by likelihood of having a diagnosis of substance dependence using EHR data from patients diagnosed with substance dependence, along with control patients with no history of substance-related conditions, matched by age, gender, and status of HIV, hepatitis C, and sickle cell disease. The top machine learning classifier using all features achieved a mean area under the receiver operating characteristic (AUROC) curve of ~ 92%, and analysis of the model uncovered associations between basic clinical factors and substance dependence. Additionally, diagnoses, prescriptions, and procedures prior to the diagnoses of substance dependence were analyzed to elucidate the clinical profile of substance-dependent patients, relative to controls.

CONCLUSIONS

The predictive model may hold utility for identifying patients at risk of developing dependence, risk of overdose, and opioid-seeking patients that report other symptoms in their visits to the emergency room.

Effects of morphine on respiratory load detection, load magnitude perception, and tactile sensation in obstructive sleep apnea

Pharyngeal and respiratory sensation is impaired in obstructive sleep apnea (OSA). Opioids may further diminish respiratory sensation. Thus protective pharyngeal neuromuscular and arousal responses to airway occlusion that rely on respiratory sensation could be impaired with opioids to worsen OSA severity. However, little is known about the effects of opioids on upper airway and respiratory sensation in people with OSA. This study was designed to determine the effects of 40 mg of MS-Contin on tactile sensation, respiratory load detection, and respiratory magnitude perception in people with OSA during wakefulness. A double-blind, randomized, crossover design (1 wk washout) was used. Twenty-one men with untreated OSA (apnea/hypopnea index = 26 ± 17 events/h) recruited from a larger clinical study completed the protocol. Tactile sensation using von Frey filaments on the back of the hand, internal mucosa of the cheek, uvula, and posterior pharyngeal wall were not different between placebo and morphine [e.g., median (interquartile range) posterior wall = 0.16 (0.16, 0.4) vs. 0.4 (0.14, 1.8) g, P = 0.261]. Similarly, compared with placebo, morphine did not alter respiratory load detection thresholds for nadir mask pressure detected = −2.05 (−3.37, −1.55) vs. −2.19 (−3.36, −1.41) cmH2O, P = 0.767], or respiratory load magnitude perception [mean ± SD Borg scores during a 5 resistive load (range: 5–126 cmH2O·l−1·s−1) protocol = 4.5 ± 1.6 vs. 4.2 ± 1.2, P = 0.347] but did reduce minute ventilation during quiet breathing (11.4 ± 3.3 vs. 10.7 ± 2.6 l/min, P < 0.01). These findings indicate that 40 mg of MS-Contin does not systematically impair tactile or respiratory sensation in men with mild to moderate, untreated OSA. This suggests that altered respiratory sensation to acute mechanical stimuli is not likely to be a mechanism that contributes to worsening of OSA with a moderate dose of morphine.

NEW & NOTEWORTHY Forty milligrams of MS-Contin does not alter upper airway tactile sensation, respiratory load detection thresholds, or respiratory load magnitude perception in people with obstructive sleep apnea but does decrease breathing compared with placebo during wakefulness. Despite increasing concerns of harm with opioids, the current findings suggest that impaired respiratory sensation to acute mechanical stimuli with this dose of MS-Contin is unlikely to be a direct mechanism contributing to worsening sleep apnea severity in people with mild-to-moderate disease.

Pain and respiration: a systematic review

Breathing techniques are commonly used to alleviate pain. Despite their frequent use, surprisingly little is known about their efficacy as well as their underlying physiological mechanisms. The purpose of this systematic review is to summarize and critically appraise the results of existing studies on the association between respiration and pain, and to highlight a potential physiological mechanism underlying the respiration-pain connection. A total of 31 publications from between 1984 and 2015 were retrieved and analyzed. These articles were classified into 4 groups: experimental and clinical studies of the effect of pain on respiration, clinical studies of the effects of breathing techniques on pain, and experimental studies of the influence of various forms of respiration on laboratory-induced pain. The findings suggest that pain influences respiration by increasing its flow, frequency, and volume. Furthermore, paced slow breathing is associated with pain reduction in some of the studies, but evidence elucidating the underlying physiological mechanisms of this effect is lacking. Here, we focus on the potential role of the cardiovascular system on the respiratory modulation of pain. Further research is definitely warranted.

[Pulmonary causes of chest pain]

Chest pain represents one of the most frequent symptoms of pulmonary diseases, in addition to dyspnea and cough. The broad differential diagnostics include the intensely painful but prognostically benign acute pleurisy as well as potentially life-threatening events, such as acute pulmonary embolism or malignant chest diseases. Primary spontaneous pneumothorax is characterized by acute chest pain. Pain associated with a respiratory infection, such as pneumonia rarely poses a difficult diagnostic problem. Painful diseases of the lungs can be differentiated in an initial approach by asking the patient if the pain is related to breathing, which is characteristic of pleuritic chest diseases. Pulmonary hypertension, lung cancer and mesothelioma show more constant pain unrelated to respiratory movements. It is most important to differentiate pain associated with acute exacerbation of chronic obstructive pulmonary disease (COPD), whereby a possible cardiac comorbidity, such as acute coronary syndrome (ACS) should always be considered.

Shrinking lung syndrome in systemic lupus erythematosus: A case series and review of the literature

Shrinking lung syndrome (SLS) is a rare and less known complication mainly associated with systemic lupus erythematosus (SLE). In this study, we analyze the clinical features, investigation findings, approaches to management, and outcome in a case series of 9 adult patients with SLE and SLS diagnosed during a 35-year period in 3 referral tertiary care hospitals in Spain. Additionally, we reviewed 80 additional cases previously reported (PubMed 1965-2015). These 80 cases, together with our 9 patients, form the basis of the present analysis.The overall SLS prevalence in our SLE population was 1.1% (9/829). SLS may complicate SLE at any time over its course, and it usually occurs in patients without previous or concomitant major organ involvement. More than half of the patients had inactive lupus according to SELENA-systemic lupus erythematosus disease activity index (SLEDAI) scores. Typically, it presents with progressive exertional dyspnea of variable severity, accompanied by pleuritic chest pain in 76% of the cases.An important diagnostic delay is common. The diagnostic tools that showed better yield for SLS detection are the imaging techniques (chest x-ray and high-resolution computed tomography) along with pulmonary and diaphragmatic function tests. Evaluation of diaphragm dome motion by M-mode ultrasonography and phrenic nerve conduction studies are less useful.There are no standardized guidelines for the treatment of SLS in SLE. The majority of patients were treated with medium or high doses of glucocorticoids. Several immunosuppressive agents have been used in conjunction with steroids either if the patient fails to improve or since the beginning of the treatment. Theophylline and beta-agonists, alone or in combination with glucocorticoids, have been suggested with the intent to increase diaphragmatic strength.The overall long-term prognosis was good. The great majority of patients had significant clinical improvement and stabilization, or mild to moderate improvement on pulmonary function tests. The mortality rate was very low.

Dyspnea and pain frequently co-occur among Medicare managed care recipients

RATIONALE

Experimental and neuroimaging studies have suggested strong associations between dyspnea and pain. The co-occurrence of these symptoms has not been examined in community samples.

OBJECTIVES

We sought to ascertain the co-occurrence of pain and dyspnea by self-report in a large cohort of Medicare recipients.

METHODS

We analyzed data from 266,000 Medicare Managed Care recipients surveyed in 2010 and 2012. Dyspnea was defined by aggregating three questions about shortness of breath (at rest, while walking one block, and while climbing stairs). Pain was measured by four questions about pain interference, chest pain, back pain, and arthritis pain. All measures were dichotomized as high or low/none. We calculated the co-occurrence of pain and dyspnea at baseline, and generated logistic regression models to find the adjusted relative risk (RR) of their co-occurrence, adjusting for patient-level factors and three potential medical causes of dyspnea (chronic obstructive pulmonary disease/emphysema/asthma, congestive heart failure, and obesity). We modeled the simultaneous development and the simultaneous resolution of dyspnea and pain between baseline and 2 years.

MEASUREMENTS AND MAIN RESULTS

Participants with dyspnea had considerably higher prevalence of pain than those without (64 vs. 18%). In fully adjusted models, participants with any of the types of pain were substantially more likely to report dyspnea than those without these types of pain (high pain interference: relative risk [RR], 1.99; 95% confidence interval [CI], 1.92-2.07; chest pain: RR, 2.11; 95% CI, 2.04-2.18; back pain: RR, 1.76; 95% CI, 1.71-1.82; and arthritis pain: RR, 1.49; 95% CI, 1.44-1.54). The relative risks of dyspnea developing or resolving at 2 years were greatly increased (RRs of 1.5 - 4) if pain also developed or resolved.

CONCLUSIONS

Pain and dyspnea commonly occurred, developed, and resolved together. Most older adults with dyspnea also reported pain. Medical conditions typically assumed to cause dyspnea did not account for this association. The most plausible explanation for the co-occurrence is physical deconditioning.

[Heart and lungs : cardinal symptom dyspnea]

Dyspnea is one of the major clinical symptoms which patients report to general practitioners, internists, cardiologists and hospitals. In this review article we discuss the evidence of medical history, laboratory procedures and diagnostic investigations to approach patients with acute or chronic dyspnea and try to structure this complex symptom dyspnea to reach the etiology of the underlying disease.

Neuromodulation and Palliative Medicine

The palliative care population is generally vulnerable to experiencing medication-induced adverse effects and drug–drug interactions. Neuromodulation may offer particular advantages over systemic medications in this population. Spinal cord stimulation and peripheral nerve stimulation have long been utilized in efforts to provide analgesia for various painful conditions. More recently, deep brain stimulation/motor cortex stimulation has anecdotally been utilized for certain intractable pain states. Although brain electrical stimulation has not been adequately trialed or in some cases even tried at all for management of a variety of symptoms, it is conceivable that in the future it may be a potential therapeutic option in efforts to palliate various severe refractory symptoms (eg, intractable pain, nausea, dyspnea, delirium).

[Problems for assessing the newborns' pain in palliative care]

Several pain scales are available for newborns, but the assessment of pain in these preverbal beings, who are in continuing neurological development, remains challenging for healthcare teams. Although neonates at the end of life are particularly vulnerable to pain and discomfort, no assessment tool has been validated in this specific population. The difficulties for assessing pain in this context are copies of those potentially encountered in other situations. Questions arise about the limits of the available scales, about possible alterations of responses to a noxious stimulus in particular contexts (extreme immaturity, brain lesions), about possibly painful situations in palliative care, about the nature of scales to choose. Data show a perception of pain at a cortical level by extremely immature infants and the ability for neonates with significant neurological injury to express pain behaviours. For some potentially painful situations (dyspnoea, gasps, hunger) neonatal data are virtually nonexistent. Fundamental scientific data and clinical data from adults and children can give some answers. One will choose scales for which the staff is trained, easily usable (preference for behavioural scales), validated for all gestational ages, reliable in the event of neurological impairment or sedation. An assessment of prolonged pain (EDIN scale or COMFORT Behaviour scale) combined with measures of acute pain (DAN or NFCS scales) is recommended. These scales should be better validated for populations of newborns and situations that are specific to palliative care. A better assessment of the parental perception and of their distress about the discomfort or pain of their child is warranted.

Effect of limb muscle fatigue on perception of respiratory effort in healthy subjects

The role of nonrespiratory peripheral afferents in dyspnea perception has not been fully elucidated yet. Our hypothesis is that fatigue-induced activation of limb muscle metaboreceptors served by group IV fine afferent fibers may impact on respiratory effort perception. We studied 12 healthy subjects breathing against progressive inspiratory resistive loads (10, 18, 30, 40, and 90 cmH2O·l−1·s) before and after inducing low-frequency fatigue of quadriceps muscle by repeating sustained contractions at ≥80% of maximal voluntary contraction. Subjects also underwent a sham protocol while performing two loaded breathing runs without muscle fatigue in between. During the loaded breathing, while subjects mimicked the quiet breathing pattern using a visual feedback, ventilation, tidal volume, respiratory frequency, pleural pressure swings, arterial oxygen saturation, end-tidal partial pressure of CO2, and dyspnea by a Borg scale were recorded. Compared with prefatigue, limb muscle fatigue resulted in a higher increase in respiratory effort perception for any given ventilation, tidal volume, respiratory frequency, pleural pressure swings, end-tidal partial pressure of CO2, and arterial oxygen saturation. No difference between the two runs was observed with the sham protocol. The present data support the hypothesis that fatigue of limb muscles increases respiratory effort perception associated with loaded breathing, likely by the activation of limb muscle metaboreceptors.

Characteristics and correlates of dyspnea in patients with advanced cancer

BACKGROUND

Dyspnea is a very distressing symptom present in the vast majority of patients with advanced cancer. There are limited data on the characteristics and correlates of dyspnea in this population. The purpose of this study was to characterize dyspnea, explore the differences between breakthrough and continuous presentations, and to determine factors associated with its intensity.

METHODS

Prospective observational study among 70 patients with dyspnea referred to a palliative care service. Dyspnea was assessed using the Edmonton Symptom Assessment System (ESAS, 0-10) and the Oxygen Cost Diagram (OCD). Oximetry, pulmonary function tests, Hospital Anxiety and Depression Scale (HADS), and a detailed systematic evaluation of daily characteristics of dyspnea were performed. Other symptoms were recorded using the ESAS.

RESULTS

Of 30 patients, 70 (43%) were female, median age was 58 (range, 28-87), and the most frequent cancer diagnosis were lung (31/70; 44%) and urologic (15/70; 21%). Constant dyspnea occurred in 27 of 70 (39%) patients, with 14 of 70 (20%) presenting breakthrough episodes. Breakthrough-only dyspnea occurred in 43 of 70 (61%). The majority of patients with breakthrough episodes (39/57; 68%) presented fewer than 5 episodes daily, most frequently lasting for less than 10 minutes (50/57; 88%). In univariate analyses ESAS dyspnea was associated with fatigue (p < 0.0001), sleep (p = 0.002), anxiety (p = 0.006), depression (p = 0.01), sensation of well-being (p = 0.03), and with OCD (p = 0.001). In multivariate analysis, ESAS dyspnea was associated with fatigue (p = 0.001), forced expiratory volume (p = 0.004), pain (p = 0.01), and depression (p = 0.03). Dyspnea intensity significantly interfered with activities (general activity, p = 0.01, mood, p = 0.02, walking ability, p = 0.04, normal work p = 0.04, and enjoyment of life, p = 0.01).

CONCLUSION

Dyspnea in patients with advanced cancer more frequently had breakthrough characteristics, was of very short duration, and interfered with daily activities.

Respiratory Dysfunction in Chronic Neck Pain Patients. A Pilot Study

The aim of this pilot study was to add weight to a hypothesis according to which patients presenting with chronic neck pain could have a predisposition towards respiratory dysfunction. Twelve patients with chronic neck pain and 12 matched controls participated in this study. Spirometric values, maximal static pressures, forward head posture and functional tests were examined in all subjects. According to the results, chronic neck patients presented with a statistically significant decreased maximal voluntary ventilation ( P = 0.042) and respiratory muscle strength (Pimax and Pemax), ( P = 0.001 and P = 0.002, respectively). Furthermore, the current study demonstrated a strong association between an increased forward head posture and decreased respiratory muscle strength in neck pateits. The connection of neck pain and respiratory function could be an important consideration in relation to patient assessment, rehabilitation and consumption of pharmacological agents.

Reduced perception of dyspnea and pain after right insular cortex lesions

RATIONALE

The perception of dyspnea and pain show many similarities. Initial imaging studies suggested an important role of the insular cortex for the perception of both sensations. However, little is known about the cortical processing of dyspnea.

OBJECTIVES

This study investigated the influence of lesions of the insular cortex on the perception of dyspnea and pain.

METHODS

Dyspnea was induced by resistive loaded breathing in four patients with right-hemispheric insular cortex lesions, as assessed with computer tomography or magnetic resonance imaging, and four matched healthy control subjects. Pain was induced by a cold-pressor test. Perceived intensity and unpleasantness of both sensations were rated on visual analog scales.

MEASUREMENTS AND MAIN RESULTS

In contrast to healthy control subjects, patients with lesions demonstrated reduced perceptual sensitivity for dyspnea, in particular for the unpleasantness of dyspnea (P < 0.05). This was paralleled by reduced sensitivity for pain in patients with lesions, as reflected by smaller ratings of intensity and unpleasantness, higher sensory pain-thresholds, and, in particular, higher affect-related pain tolerance times (P < 0.05).

CONCLUSIONS

The results suggest that lesions of the right insular cortex are associated with reduced sensitivity for the perception of dyspnea and pain, in particular for their perceived unpleasantness. This underlines the importance of the insular cortex for the perception of both sensations.

Association of the shrinking lung syndrome in systemic lupus erythematosus with pleurisy: a systematic review

OBJECTIVES

To report 2 patients with systemic lupus erythematosus and typical shrinking lung syndrome (SLS) in which pleuritic chest pain was the predominant symptom. In addition, to record the prevalence of pleuritic chest pain in all reported cases of patients with SLS and diaphragmatic dysfunction.

METHODS

We conducted a comprehensive search of the English literature to record the association of pleurisy and SLS in all reported cases using the MEDLINE database from 1965 to present.

RESULTS

Of the 77 patients with SLS reported in the literature, 50 (65%) patients had pleuritic chest pain at the time of evaluation. Treatment with anti-inflammatory agents improved symptoms in the majority of cases.

CONCLUSIONS

Pleuritic inflammation and pain may have an important role in the pathogenesis of SLS. A possible mechanism linking pleural inflammation and diaphragm dysfunction may be via a reflex inhibition of diaphragmatic activation.

Experimental comparison of dyspnea and pain

Dyspnea and pain are similarly unpleasant, alarming physical sensations, but studies examining both sensations in combination are lacking. In the present study, dyspnea was induced in 7 healthy volunteers by breathing through inspiratory resistive loads and the effects were compared with those of a heat pain stimulus. End-tidal partial pressures of carbon dioxide (PET(CO2)), inspiratory time (Ti), breathing frequency (f), experienced unpleasantness, and intensity were measured. No difference was observed between dyspnea and pain in experienced intensity and unpleasantness (p > .05). During dyspneic stimulation, slightly higher Ti was found than for pain (p < .08). PET(CO2) showed slight increases during the dyspneic versus the baseline and painful conditions (deltaPET(CO2) = 1.5 and 1.3 mmHg, respectively; p < .01 andp < .05). This study shows that the effects of dyspnea and heat pain can be compared within one experiment; both stimuli can be presented with similar intensity and unpleasantness, which is a prerequisite for comparing responses to them. The changes in PET(CO2) between our conditions were minimal, allowing an application of the present design to future fMRI studies.

Attentional distraction reduces the affective but not the sensory dimension of perceived dyspnea

The perception of dyspnea shows many similarities to the perception of pain. Both are multidimensional processes, which are not only influenced by sensory input but also by nonsensory factors like attention. Recent research has suggested that attentional distraction might reduce the perception of dyspnea but results are conflicting. Furthermore, the specific impact of attentional distraction on the distinct dimensions of perceived dyspnea has not been studied yet. Therefore, the present study examined the specific impact of changes in the attentional focus on the sensory and affective dimension of perceived dyspnea. Dyspnea was induced in forty-four healthy volunteers (mean age: 27.7 years, range: 18-47 years) by breathing through an inspiratory resistive load (3.57 kPa/L/s), while attention was directed either to breathing or distracted by reading texts. Inspiratory time (T(i)) and breathing frequency (f) were measured continuously. After each condition the experienced intensity (i.e., sensory dimension) and unpleasantness (i.e., affective dimension) of dyspnea were rated on separate visual analog scales (VAS), presented in randomized order. ANOVAs showed that attentional distraction during loaded breathing reduced the perceived unpleasantness of dyspnea (P<0.05), while the perceived intensity of dyspnea as well as T(i) and f remained unchanged. The results show that attentional distraction reduces the affective, but not the sensory dimension of induced dyspnea in healthy volunteers. Future studies are needed to clarify whether attentional distraction can effectively be used as intervention technique for reducing the unpleasant aspects of dyspnea in different patients groups.

A Controlled Trial of the Effects of Leg Training on Breathing Pattern and Dynamic Hyperinflation in Severe COPD

The effects of training on dynamic hyperinflation in stable chronic obstructive pulmonary disease (COPD) were investigated by using a controlled study of 28 subjects with FEV(1) = 42.5 (8.3 SD)%pred and 20 matched controls [FEV(1) = 44.9 (10.4)%pred]. Training consisted of spending 45 min/day, 4 days/week on a cycle-ergometer for six weeks. Maximal inspiratory and expiratory pressures (MIP and MEP), lung volumes, and two constant-work-rate (CWR) exercise tests (low- and high-intensity) were performed. Significant (p < 0.0l) improvements in the training group were observed in MIP [+8 (12) cmH(2)O], MEP [+18 (20) cmH(2)O], and endurance to high-intensity CWR [+7(5) min], and there were significant decreases in respiratory rate and end-expiratory lung volume (EELV) during both exercise tests. At 5 min, EELV decreased 0.1(0.08) L and 0.31(0.13) L and at end of exercise, EELV decreased by 0.09(0.07) L and 0.15(0.11) L respectively, for the moderate- and high-intensity tests. Dyspnea also decreased significantly at both exercise intensities. No changes were observed in the control group. Increased endurance showed independent significant (p < 0.05) correlation with changes in EELV, leg fatigue, and MEP. EELV changes showed a significant negative correlation with resting inspiratory capacity. We conclude that exercise training has beneficial effects on respiratory pattern and dynamic hyperinflation that may partially explain the reduction in dyspnea and the improvement in exercise tolerance.

Unique, common, and interacting cortical correlates of thirst and pain

This study used positron-emission tomography to establish the patterns of brain activity involved in the isolated and concurrent experiences of thirst and pain. Ten subjects were scanned while experiencing pain evoked with noxious pressure, while experiencing thirst after the infusion of hypertonic saline, and while experiencing pain when thirsty. After the onset of thirst, noxious pressure evoked more intense sensations of pain. Noxious pressure did not change subjective ratings of thirst. Thirst caused activation in the anterior cingulate (Brodmann area 32) and the insula. Enhanced pain responses were associated with increased activity in cortical regions that are known to correlate with pain intensity, and also with unique activity in the pregenual anterior cingulate and ventral orbitofrontal cortex. These findings suggest a role for limbic and prefrontal cortices in the modulation of pain during the experience of thirst.

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.

Dyspnea, Ventilatory Pattern, and Changes in Dynamic Hyperinflation Related to the Intensity of Constant Work Rate Exercise in COPD

STUDY OBJECTIVE

We undertook the present study to investigate the perception of dyspnea (with respect to changes in end-inspiratory and end-expiratory lung volumes), during four different levels of high-intensity constant work rate exercise (CWRE) in patients with severe COPD.

DESIGN

Crossover descriptive study with consecutively recruited subjects.

SETTING

Tertiary university hospital.

PATIENTS

Twenty-seven subjects with severe COPD (mean [+/- SD] age, 65 +/- 5 years of age; mean FEV1, 43 +/- 8% predicted; and mean inspiratory capacity [IC]; 74 +/- 14% predicted).

MEASUREMENTS AND RESULTS

Subjects randomly performed four high-intensity CWRE tests (conducted at 65%, 75%, 85%, and 95% of their symptom-limited peak work rate). Dyspnea, leg fatigue, and IC were determined every 2 min during exercise with breath-by-breath gas exchange and ventilatory measurements. There was a good correlation between the resting IC percent predicted and the oxygen uptake (V(O2)) peak (r = 0.64 to 0.69 between the IC percent predicted and V(O2) peak at the four work rates). There were significant differences (p < 0.01) in mean respiratory rate (33 +/- 6, 35 +/- 6, 37 +/- 6, and 38 +/- 6 min), peak dyspnea score (5.9 +/- 1.3, 6.3 +/- 1.4, 6.8 +/- 1.2, and 6.9 +/- 1.6), minute ventilation (45.0 +/- 8.7, 43.8 +/- 7.7, 43.1 +/- 8.7, and 42.8 +/- 8.0 L/min), leg fatigue (4.8 +/- 1.3, 5.1 +/- 1.3, 5.7 +/- 1.4, and 5.8 +/- 1.4), and end-tidal carbon dioxide partial pressure (4.41 +/- 0.36, 4.53 +/- 0.33, 4.66 +/- 0.31, and 4.76 +/- 0.24 kPa), respectively, for tests conducted at 65%, 75%, 85%, and 95% of their symptom-limited peak work rate, and in mean end-expiratory lung volume ([EELV] 4.55 +/- 0.44, 4.69 +/- 0.43, and 4.79 +/- 0.43 L), respectively, for tests conducted at 65%, 75%, and 85% of their symptom-limited peak work rate. In multivariable analysis, the factors that were independently correlated with dyspnea (p < 0.05) were EELV, peak inspiratory flow, and leg fatigue/discomfort.

CONCLUSION

In COPD subjects with flow limitation at rest, the perception of dyspnea increased nonlinearly with the magnitude of high-intensity CWRE in association with a faster respiratory pattern and an increase in EELV. At the highest work rates, it appeared that a reduction in tidal volume and ventilation peak may have limited the tolerance to exercise.

Origin of symptoms in patients with cachexia with special reference to weakness and shortness of breath

Cachexia is a complication of many disorders. It is associated with an extremely poor prognosis and many symptoms. The wasting process affects particularly skeletal muscle causing extreme fatigue and weakness. In many underlying conditions associated with cachexia, the patient also suffers an often unexplained severe dyspnoea along with weakness, asthenia and exhaustion. There appears to be marked similarities in the cause of dyspnoea and fatigue between different cachectic conditions. Using the example of cardiac cachexia, this article reviews the evidence linking skeletal muscle reflex inputs to ventilatory control and exaggerated chemoreflex responses as candidates for the heightened perception of dyspnoea which cannot be explained by heart or lung dysfunction in many patients. Evidence is reviewed that similar processes may occur in other cachexias, especially those complicating cancer, AIDS, chronic liver disease, and chronic lung disease. Potential novel therapeutic strategies to combat these cachexia symptoms are reviewed.

Predictive factors for suicidal ideation in patients with unresectable lung carcinoma

BACKGROUND

Despite serious concern over the suicidality of cancer patients in clinical oncology practice, few studies have addressed this issue. The purpose of the current study was to investigate the prevalence and predictive factors of suicidal ideation in patients with unresectable lung carcinoma in a follow-up setting.

METHODS

Patients with newly diagnosed unresectable nonsmall cell lung carcinoma participated in this study. Their suicidal ideation was assessed 6 months after disclosure of the cancer diagnosis. Predictive factors for suicidal ideation were investigated by assessing a broad range of biomedical and psychosocial factors between the time of disclosure and start of cancer therapy (baseline) and 6 months after disclosure of the cancer diagnosis (follow-up).

RESULTS

Although strong suicidal ideation was rare in this population, 13 (15%) of the 89 subjects who completed the baseline and follow-up ratings had some degree of suicidal ideation 6 months after disclosure of the cancer diagnosis. Univariate analysis revealed that significant predictive factors for suicidal ideation were pain at baseline, declining physical function, and the development of a depressive disorder. Multivariate analysis indicated that pain at baseline (odds ratio [OR] = 3.72, 95% confidence interval [CI] = 1.12-14.69, P = 0.04) and the development of a depressive disorder (OR =27.97, 95% CI = 5.18-214.14, P = 0.0003) were the final significant predictive factors.

CONCLUSIONS

Suicidal ideation among unresectable lung carcinoma patients should not be neglected because it is not rare. Comprehensive care consisting of at least earlier pain management and appropriate psychiatric intervention is indispensable to prevent subsequent suicidal ideation.

Factors correlated with dyspnea in advanced lung cancer patients: organic causes and what else?

This study aimed to investigate factors correlated with dyspnea in cancer patients among a broad range of medico-psycho-social factors. A total of 171 consecutive outpatients with advanced lung cancer were recruited. Dyspnea was evaluated by using the Cancer Dyspnea Scale, a valid, reliable 12-item self-rating scale developed to assess the multidimensional nature of dyspnea in cancer patients. Possible correlates, including 1) medical (clinical stage, Performance Status, SpO(2), organic causes of dyspnea, other symptoms, such as cough and pain, etc.), 2) psychological (anxiety and depression), and 3) social (education, marital status, existence of confidants, etc.), factors were collected from medical charts, interviews, and self-rating questionnaires. Multiple regression analysis revealed that psychological distress, presence of organic causes, cough, and pain were significantly correlated with dyspnea (P < 0.05, multiple R(2) = 0.303). The present study confirms that dyspnea is multifactorial and that a beneficial therapeutic strategy might include intervention for psychological distress and pain.

Respiratory dysregulation in anxiety, functional cardiac, and pain disorders. Assessment, phenomenology, and treatment

Respiration is a complex physiological system affecting a variety of physical processes that can act as a critical link between mind and body. This review discusses the evidence for dysregulated breathing playing a role in three clinical syndromes: panic disorder, functional cardiac disorder, and chronic pain. Recent technological advances allowing the ambulatory assessment of endtidal partial pressure of CO2 (PCO2) and respiratory patterns have opened up new avenues for investigation and treatment of these disorders. The latest evidence from laboratories indicates that subtle disturbances of breathing, such as tidal volume instability and sighing, contribute to the chronic hypocapnia often found in panic patients. Hypocapnia is also common in functional cardiac and chronic pain disorders, and studies indicate that it mediates some of their symptomatology. Consistent with the role of respiratory dysregulation in these disorders, initial evidence indicates efficacy of respiration-focused treatment.