Effect of increased blood levels of β-endorphin on perception of breathlessness

[Appropriate use of strong opioids in medical units: Recommendations and action to be taken in daily practice]

The use of strong opioids in medical units is recurrent, mainly for analgesic purposes. The risk of occurrence of an overdose or an opioid use disorders causes very legitimate concerns for the physician, which may limit the use of opioid treatment or the adaptation of the doses necessary to relieve the patient. We provide a summary of the literature aimed at defining the indications, the adverse effects and the risks involved, the prescribing methods in order to reassure professionals and promote the safe use of these molecules.

Nalmefene combined noninvasive positive-pressure ventilation in Chinese patients with chronic obstructive pulmonary disease coupled with type II respiratory failure: A meta-analysis

BACKGROUND

Nalmefene is an opioid system modulator with antagonist activity at the μ and δ receptors and partial agonist activity at the κ receptor. Previous studies have suggested that nalmefene could improve respiratory function in patients with chronic obstructive pulmonary disease (COPD). However, there is no comprehensive systematic review published regarding the clinical efficacy of nalmefene.

METHODS

We explored the following electronic bibliographic databases: EMBASE, Web of Science, PubMed, Wanfang, and Chinese national knowledge infrastructure. To collect data from randomized controlled trials on the therapy of COPD coupled with type II respiratory failure and nalmefene + noninvasive ventilator treatment. The retrieved articles were screened to determine the final inclusion criteria and to extract relevant data, such as the clinical efficacy rate, pulmonary function, blood gas analysis, and adverse reactions. In our study, we used relative risk and weighted mean deviation, as well as a 95% confidence interval for describing nalmefene effectiveness and safety while treating COPD with type II respiratory failure.

RESULTS

The outcomes of the meta-analysis demonstrated that the clinical efficacy rate of the nalmefene + noninvasive ventilation group was higher than that of the naloxone + noninvasive ventilation and noninvasive ventilation groups. Moreover, the improvement indices of pH value, partial pressure and saturation of blood oxygen, partial pressure of carbon dioxide, and pulmonary function of the nalmefene + noninvasive ventilation group were better than those of the noninvasive ventilation group, and there was no increase in the occurrence of adverse drug reactions.

CONCLUSION

Nalmefene combined with noninvasive ventilation can significantly improve the blood gas index and lung function in patients with COPD combined with type II respiratory failure.

Modified-release morphine or placebo for chronic breathlessness: the MABEL trial protocol

Chronic breathlessness, a persistent and disabling symptom despite optimal treatment of underlying causes, is a frightening symptom with serious and widespread impact on patients and their carers. Clinical guidelines support the use of morphine for the relief of chronic breathlessness in common long-term conditions, but questions remain around clinical effectiveness, safety and longer term (>7 days) administration. This trial will evaluate the effectiveness of low-dose oral modified-release morphine in chronic breathlessness. This is a multicentre, parallel group, double-blind, randomised, placebo-controlled trial. Participants (n=158) will be opioid-naïve with chronic breathlessness due to heart or lung disease, cancer or post-coronavirus disease 2019. Participants will be randomised 1:1 to 5 mg oral modified-release morphine/placebo twice daily and docusate/placebo 100 mg twice daily for 56 days. Non-responders at Day 7 will dose escalate to 10 mg morphine/placebo twice daily at Day 15. The primary end-point (Day 28) measure will be worst breathlessness severity (previous 24 h). Secondary outcome measures include worst cough, distress, pain, functional status, physical activity, quality of life, and early identification and management of morphine-related side-effects. At Day 56, participants may opt to take open-label, oral modified-release morphine as part of usual care and complete quarterly breathlessness and toxicity questionnaires. The study is powered to be able to reject the null hypothesis and an embedded normalisation process theory-informed qualitative substudy will explore the adoption of morphine as a first-line pharmacological treatment for chronic breathlessness in clinical practice if effective.

Current pharmacological strategies for symptomatic reduction of persistent breathlessness - a literature review

INTRODUCTION

Persistent breathlessness is a debilitating symptom that is prevalent in the community, particularly in people with chronic and life-limiting illnesses. Treatment includes different steps, including pharmacological treatment aiming to improve the symptom and optimize people's wellbeing.

AREAS COVERED

PubMed and Google Scholar were screened using 'chronic breathlessness' OR 'persistent breathlessness,' AND 'pharmacological treatment,' OR 'opioids.' This review focuses on pharmacological treatments to reduce persistent breathlessness and discusses possible mechanisms involved in the process of breathlessness reduction through pharmacotherapy. Research gaps in the field of persistent breathlessness research are outlined, and future research directions are suggested.

EXPERT OPINION

Regular, low-dose (≤30 mg/day), sustained-release morphine is recommended as the first-line pharmacological treatment for persistent breathlessness. Inter-individual variation in response needs to be investigated in future studies in order to optimize clinical outcomes. This includes 1) better understanding the centrally mediated mechanisms associated with persisting breathlessness and response to pharmacological therapies, 2) understanding benefit from the perspective of people experiencing persistent breathlessness, small and meaningful gains in physical activity.

Consistency Evaluation of Two Loading Devices in Measuring the Perception of Dyspnea

Purpose

This study aimed to assess the consistency of hand-held electronic incremental threshold loading device (I-TLD) and traditional constant threshold loading device (C-TLD) in measuring the perception of dyspnea (POD) in humans.

Patients and methods

Thirty-eight patients with stable chronic obstructive pulmonary disease (COPD) and 41 non-COPD subjects were recruited for the study, all of whom were subjected to an external loading breathing test by gradually increasing the inspiratory load starting from 0 to 5, 10, 20, and 30 cmH₂O oral pressure using I-TLD and C-TLD. The Borg score measurement was performed immediately after the loading breath of each level. The linear regression slope a of Borg scores vs percentage of oral pressure from the patients’ maximum represented patients’ POD. The consistency of POD measured by the two devices was analyzed by two Related Samples Wilcoxon test, Spearman correlation analysis, and Bland-Altman analysis.

Results

There was no significant difference in slope a measured by the two devices in all subjects. The Spearman correlation analysis revealed that the slope a measured by the two devices in the inspiratory loading breath test had a significant correlation: in COPD patients, r = 0.678, (p < 0.001) and in non-COPD subjects, r = 0.603, (p < 0.001). For the results of the Bland-Altman analysis of the whole subjects, 3.8% (3/79) points were outside of the 95% LoA confidence interval (CI) (−10.380, 9.457), and the LoA CI was acceptable, which depicted that the two devices were consistent in their estimation.

Conclusion

I-TLD was consistent with C-TLD in measuring POD in COPD patients and non-COPD subjects. I-TLD may be used as an alternative method to replace C-TLD to measure POD in COPD patients and non-COPD subjects.

Interventions for palliative symptom control in COVID-19 patients

BACKGROUND

Individuals dying of coronavirus disease 2019 (COVID-19) may experience distressing symptoms such as breathlessness or delirium. Palliative symptom management can alleviate symptoms and improve the quality of life of patients. Various treatment options such as opioids or breathing techniques have been discussed for use in COVID-19 patients. However, guidance on symptom management of COVID-19 patients in palliative care has often been derived from clinical experiences and guidelines for the treatment of patients with other illnesses. An understanding of the effectiveness of pharmacological and non-pharmacological palliative interventions to manage specific symptoms of COVID-19 patients is required.

OBJECTIVES

To assess the efficacy and safety of pharmacological and non-pharmacological interventions for palliative symptom control in individuals with COVID-19.

SEARCH METHODS

We searched the Cochrane COVID-19 Study Register (including Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (PubMed), Embase, ClinicalTrials.gov, World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), medRxiv); Web of Science Core Collection (Science Citation Index Expanded, Emerging Sources); CINAHL; WHO COVID-19 Global literature on coronavirus disease; and COAP Living Evidence on COVID-19 to identify completed and ongoing studies without language restrictions until 23 March 2021. We screened the reference lists of relevant review articles and current treatment guidelines for further literature.

SELECTION CRITERIA

We followed standard Cochrane methodology as outlined in the Cochrane Handbook for Systematic Reviews of Interventions. We included studies evaluating palliative symptom management for individuals with a confirmed diagnosis of COVID-19 receiving interventions for palliative symptom control, with no restrictions regarding comorbidities, age, gender, or ethnicity. Interventions comprised pharmacological as well as non-pharmacological treatment (e.g. acupressure, physical therapy, relaxation, or breathing techniques). We searched for the following types of studies: randomized controlled trials (RCT), quasi-RCTs, controlled clinical trials, controlled before-after studies, interrupted time series (with comparison group), prospective cohort studies, retrospective cohort studies, (nested) case-control studies, and cross-sectional studies. We searched for studies comparing pharmacological and non-pharmacological interventions for palliative symptom control with standard care. We excluded studies evaluating palliative interventions for symptoms caused by other terminal illnesses. If studies enrolled populations with or exposed to multiple diseases, we would only include these if the authors provided subgroup data for individuals with COVID-19. We excluded studies investigating interventions for symptom control in a curative setting, for example patients receiving life-prolonging therapies such as invasive ventilation.  DATA COLLECTION AND ANALYSIS: We used a modified version of the Newcastle Ottawa Scale for non-randomized studies of interventions (NRSIs) to assess bias in the included studies. We included the following outcomes: symptom relief (primary outcome); quality of life; symptom burden; satisfaction of patients, caregivers, and relatives; serious adverse events; and grade 3 to 4 adverse events. We rated the certainty of evidence using the GRADE approach.  As meta-analysis was not possible, we used tabulation to synthesize the studies and histograms to display the outcomes.  MAIN RESULTS: Overall, we identified four uncontrolled retrospective cohort studies investigating pharmacological interventions for palliative symptom control in hospitalized patients and patients in nursing homes. None of the studies included a comparator. We rated the risk of bias high across all studies. We rated the certainty of the evidence as very low for the primary outcome symptom relief, downgrading mainly for high risk of bias due to confounding and unblinded outcome assessors. Pharmacological interventions for palliative symptom control We identified four uncontrolled retrospective cohort studies (five references) investigating pharmacological interventions for palliative symptom control. Two references used the same register to form their cohorts, and study investigators confirmed a partial overlap of participants. We therefore do not know the exact number of participants, but individual reports included 61 to 2105 participants. Participants received multimodal pharmacological interventions: opioids, neuroleptics, anticholinergics, and benzodiazepines for relieving dyspnea (breathlessness), delirium, anxiety, pain, audible upper airway secretions, respiratory secretions, nausea, cough, and unspecified symptoms.  Primary outcome: symptom relief All identified studies reported this outcome. For all symptoms (dyspnea, delirium, anxiety, pain, audible upper airway secretions, respiratory secretions, nausea, cough, and unspecified symptoms), a majority of interventions were rated as completely or partially effective by outcome assessors (treating clinicians or nursing staff). Interventions used in the studies were opioids, neuroleptics, anticholinergics, and benzodiazepines.  We are very uncertain about the effect of pharmacological interventions on symptom relief (very low-certainty evidence). The initial rating of the certainty of evidence was low since we only identified uncontrolled NRSIs. Our main reason for downgrading the certainty of evidence was high risk of bias due to confounding and unblinded outcome assessors. We therefore did not find evidence to confidently support or refute whether pharmacological interventions may be effective for palliative symptom relief in COVID-19 patients. Secondary outcomes We planned to include the following outcomes: quality of life; symptom burden; satisfaction of patients, caregivers, and relatives; serious adverse events; and grade 3 to 4 adverse events. We did not find any data for these outcomes, or any other information on the efficacy and safety of used interventions. Non-pharmacological interventions for palliative symptom control None of the identified studies used non-pharmacological interventions for palliative symptom control.

AUTHORS' CONCLUSIONS

We found very low certainty evidence for the efficacy of pharmacological interventions for palliative symptom relief in COVID-19 patients. We found no evidence on the safety of pharmacological interventions or efficacy and safety of non-pharmacological interventions for palliative symptom control in COVID-19 patients. The evidence presented here has no specific implications for palliative symptom control in COVID-19 patients because we cannot draw any conclusions about the effectiveness or safety based on the identified evidence. More evidence is needed to guide clinicians, nursing staff, and caregivers when treating symptoms of COVID-19 patients at the end of life. Specifically, future studies ought to investigate palliative symptom control in prospectively registered studies, using an active-controlled setting, assess patient-reported outcomes, and clearly define interventions. The publication of the results of ongoing studies will necessitate an update of this review. The conclusions of an updated review could differ from those of the present review and may allow for a better judgement regarding pharmacological and non-pharmacological interventions for palliative symptom control in COVID-19 patients.

High-Flow Nasal Cannula Therapy for Exertional Dyspnea in Patients with Cancer: A Pilot Randomized Clinical Trial

BACKGROUND

Exertional dyspnea is common in patients with cancer and limits their function. The impact of high-flow nasal cannula on exertional dyspnea in nonhypoxemic patients is unclear. In this double-blind, parallel-group, randomized trial, we assessed the effect of flow rate (high vs. low) and gas (oxygen vs. air) on exertional dyspnea in nonhypoxemic patients with cancer.

PATIENTS AND METHODS

Patients with cancer with oxygen saturation >90% at rest and exertion completed incremental and constant work (80% maximal) cycle ergometry while breathing low-flow air at 2 L/minute. They were then randomized to receive high-flow oxygen, high-flow air, low-flow oxygen, or low-flow air while performing symptom-limited endurance cycle ergometry at 80% maximal. The primary outcome was modified 0-10 Borg dyspnea intensity scale at isotime. Secondary outcomes included dyspnea unpleasantness, exercise time, and adverse events.

RESULTS

Seventy-four patients were enrolled, and 44 completed the study (mean age 63; 41% female). Compared with low-flow air at baseline, dyspnea intensity was significantly lower at isotime with high-flow oxygen (mean change, -1.1; 95% confidence interval [CI], -2.1, -0.12) and low-flow oxygen (-1.83; 95% CI, -2.7, -0.9), but not high-flow air (-0.2; 95% CI, -0.97, 0.6) or low-flow air (-0.5; 95% CI, -1.3, 0.4). Compared with low-flow air, high-flow oxygen also resulted in significantly longer exercise time (difference + 2.5 minutes, p = .009), but not low-flow oxygen (+0.39 minutes, p = .65) or high-flow air (+0.63 minutes, p = .48). The interventions were well tolerated without significant adverse effects.

CONCLUSION

Our preliminary findings support that high-flow oxygen improved both exertional dyspnea and exercise duration in nonhypoxemic patients with cancer. (ClinicalTrials.gov ID: NCT02357134).

IMPLICATIONS FOR PRACTICE

In this four-arm, double-blind, randomized clinical trial examining the role of high-flow nasal cannula on exertional dyspnea in patients with cancer without hypoxemia, high-flow oxygen, but not high-flow air, resulted in significantly lower dyspnea scores and longer exercise time. High-flow oxygen delivered by high-flow nasal cannula devices may improve clinically relevant outcomes even in patients without hypoxemia.

High-Flow Oxygen and High-Flow Air for Dyspnea in Hospitalized Patients with Cancer: A Pilot Crossover Randomized Clinical Trial

BACKGROUND

The effect of high-flow oxygen (HFOx) and high-flow air (HFAir) on dyspnea in nonhypoxemic patients is not known. We assessed the effect of HFOx, HFAir, low-flow oxygen (LFOx), and low-flow air (LFAir) on dyspnea.

SUBJECTS, MATERIALS, AND METHODS

This double-blind, 4×4 crossover clinical trial enrolled hospitalized patients with cancer who were dyspneic at rest and nonhypoxemic (oxygen saturation >90% on room air). Patients were randomized to 10 minutes of HFOx, HFAir, LFOx, and LFAir in different orders. The flow rate was titrated between 20-60 L/minute in the high-flow interventions and 2 L/minute in the low-flow interventions. The primary outcome was dyspnea numeric rating scale (NRS) "now" where 0 = none and 10 = worst.

RESULTS

Seventeen patients (mean age 51 years, 58% female) completed 55 interventions in a random order. The absolute change of dyspnea NRS between 0 and 10 minutes was -1.8 (SD 1.7) for HFOx, -1.8 (2.0) for HFAir, -0.5 (0.8) for LFOx, and - 0.6 (1.2) for LFAir. In mixed model analysis, HFOx provided greater dyspnea relief than LFOx (mean difference [95% confidence interval] -0.80 [-1.45, -0.15]; p = .02) and LFAir (-1.24 [-1.90, -0.57]; p < .001). HFAir also provided significantly greater dyspnea relief than LFOx (-0.95 [-1.61, -0.30]; p = .005) and LFAir (-1.39 [-2.05, -0.73]; p < .001). HFOx was well tolerated. Seven (54%) patients who tried all interventions blindly preferred HFOx and four (31%) preferred HFAir.

CONCLUSION

We found that HFOx and HFAir provided a rapid and clinically significant reduction of dyspnea at rest in hospitalized nonhypoxemic patients with cancer. Larger studies are needed to confirm these findings (Clinicaltrials.gov: NCT02932332).

IMPLICATIONS FOR PRACTICE

This double-blind, 4×4 crossover trial examined the effect of oxygen or air delivered at high- or low-flow rates on dyspnea in hospitalized nonhypoxemic patients with cancer. High-flow oxygen and high-flow air were significantly better at reducing dyspnea than low-flow oxygen/air, supporting a role for palliation beyond oxygenation.

Opioids for breathlessness: a narrative review

Chronic breathlessness is a disabling and distressing condition for which there is a growing evidence base for a range of interventions. Non-pharmacological interventions are the mainstay of management and should be optimised prior to use of opioid medication. Opioids are being implemented variably in practice for chronic breathlessness. This narrative review summarises the evidence defining current opioids for breathlessness best practice and identifies remaining research gaps. There is level 1a evidence to support the use of opioids for breathlessness. The best evidence is for 10–30 mg daily de novo low-dose oral sustained-release morphine in opioid-naïve patients. This should be considered the current standard of care following independent, regulatory scrutiny by one of the world’s therapeutics regulatory bodies. Optimal benefits are seen in steady state; however, there are few published data about longer term benefits or harms. Morphine-related adverse events are common but mostly mild and self-limiting on withdrawal of drug. Early and meticulous management of constipation, nausea and vomiting is needed particularly in the first week of administration. Serious adverse events are no more common than placebo in clinical studies. Observational studies in severe chronic lung disease do not show excess mortality or hospital admission in those taking opioids. We have no long-term data on immune or endocrine function. There are promising data regarding prophylaxis for exertion-related breathlessness, but given the risks associated with transmucosal fentanyl, caution is needed with regard to clinical use pending longer term, robust safety data.

Isolating peripheral effects of endogenous opioids in modulating exertional breathlessness in people with moderate or severe COPD: a randomised controlled trial

Question addressed by the study

Endogenous opioids (endorphins) have been reported to modulate exercise-induced breathlessness, but the relative contribution of peripheral opioid receptors has not been tested.

Materials, participants and methods

This was a double-blind, randomised, three-arm, cross-over trial in outpatients with spirometry-verified moderate to severe chronic obstructive pulmonary disease. Participants undertook an incremental symptom-limited treadmill test followed by five endurance treadmill tests at 75% of their maximal work rate; two tests for familiarisation and three tests 30 min after intravenous injection of either methylnaltrexone 0.3 mg·kg⁻¹ (blocking peripheral opioid receptors only) or naloxone 0.1 mg·kg⁻¹ (blocking both central and peripheral opioid receptors) or normal saline, in randomised order. The primary end-point was the regression slope between breathlessness intensity (0–10 numerical rating scale) and oxygen consumption (V′_O2) during the walk tests, comparing methylnaltrexone and placebo using a paired t-test.

Results

17 participants completed the trial: median (range) 66 (55–82) years; 15 males; mean±sd forced expiratory volume (FEV₁) 53.8±17.6% predicted; FEV₁/forced vital capacity ratio 0.55±15.9. There was no statistically or clinically significant difference in the primary end-point (regression slope of breathlessness intensity and V′_O2) for methylnaltrexone (p=0.498) or naloxone (p=0.804), compared to placebo. Secondary outcomes were similar between the three treatment groups, including peak and mean breathlessness intensity and unpleasantness, exercise capacity, endurance time and leg fatigue.

Answer to the question

Blocking peripheral opioid receptors (methylnaltrexone) or peripheral and central opioid receptors (naloxone) did not appear to modulate breathlessness intensity nor exercise capacity when compared with placebo (no blockade).

A double-blind, placebo controlled, randomised, cross-over study using methylnaltrexone found no evidence for a contribution of peripheral opioid receptors to the modulation of breathlessness by endogenous endorphins.http://bit.ly/32DZv3I

Evaluation of Dyspnea in the Elderly

Dyspnea is due to an imbalance between the demand to breathe and the ability to breathe. The prevalence is ∼30% for those 65 years or older with walking on a level surface or up an incline. Dyspnea is a strong predictor of mortality in elderly individuals. Anemia, cardiovascular disease, deconditioning, psychological disorders, and respiratory diseases are common causes of dyspnea. Initial treatments to relieve breathing discomfort should be directed toward improving the pathophysiology of the underlying disease. Simple and inexpensive strategies to relieve dyspnea are available. This article provides an update on the evaluation of chronic dyspnea in elderly individuals.

Pharmacological management of breathlessness in COPD: recent advances and hopes for the future

INTRODUCTION

Activity-related breathlessness is often the dominant symptom in patients with chronic obstructive pulmonary disease (COPD) and usually persists despite optimal medical therapy. Currently, our inability to meaningfully alter the pathophysiology of the underlying disease means that we must focus our attention on relieving this distressing symptom so as to improve exercise tolerance and quality of life.

AREAS COVERED

The current review examines the neurobiology of breathlessness and constructs a solid physiological rationale for amelioration of this distressing symptom. We will examine the efficacy of interventions which: 1) reduce the increased central drive to breathe (opioids); 2) improve the respiratory system's ability to appropriately respond to this increased demand (bronchodilators); and 3) address the important affective dimension of breathlessness (anxiolytics). Expert commentary: Advances in our understanding of the mechanisms of activity-related breathlessness in COPD, and its measurement in the clinical domain, now set the stage for the development of effective management strategies on an individual patient basis.

Blinded Patient Preference for Morphine Compared to Placebo in the Setting of Chronic Refractory Breathlessness--An Exploratory Study

CONTEXT

Patients' preference for morphine therapy has received little attention in the setting of chronic refractory breathlessness. However, this is one important factor in considering longer term therapy.

OBJECTIVES

The aim of this secondary analysis was to explore blinded patient preference of morphine compared to placebo for this indication and to define any predictors of preference.

METHODS

Data were pooled from three randomized, double-blind, crossover, placebo-controlled studies of morphine (four days each) in chronic refractory breathlessness. Blinded patient preferences were chosen at the end of each study. A multivariable regression model was used to establish patient predictors of preference.

RESULTS

Sixty-five participants provided sufficient data (60 men; median age 74 years; heart failure 55%, chronic obstructive pulmonary disease 45%; median Eastern Cooperative Oncology Group performance status 2). Forty-three percent of participants preferred morphine (32% placebo and 25% no preference). Morphine preference and younger age were strongly associated: odds ratio = 0.85, 95% confidence interval 0.78-0.93; P < 0.001). There was also an inverse association between morphine preference and sedation (odds ratio = 0.77, 95% confidence interval 0.60-0.99; P < 0.05). An inverse association was also seen between nausea and morphine preference in the univariate model only (P < 0.05). No association was seen between morphine preference and breathlessness intensity, either at baseline or change from baseline.

CONCLUSION

Participants preferred morphine over placebo for the relief of chronic refractory breathlessness. Morphine offers clinically important improvement, but net benefit can be easily outweighed by side effects, reducing net benefits. Side effects require aggressive management to allow more patients to realize benefits.

Recent advances in dyspnea

Dyspnea is the most prevalent symptom among patients with cardiac and respiratory diseases. It is an independent predictor of mortality in patients with heart disease, COPD, and the elderly. Studies using naloxone to block opioid-receptor signaling demonstrate that endogenous opioids modulate dyspnea in patients with COPD. Neuroimaging studies support a cortical-limbic network for dyspnea perception. A 2012 American Thoracic Society statement recommended that dyspnea be considered across three different constructs: sensory (intensity), affective (distress), and impact on daily activities. The 2013 GOLD (Global Initiative for Chronic Obstructive Lung Disease) executive summary recommended a treatment paradigm for patients with COPD based on the modified Medical Research Council dyspnea score. The intensity and quality of dyspnea during exercise in patients with COPD is influenced by the time to onset of critical mechanical volume constraints that are ultimately dictated by the magnitude of resting inspiratory capacity. Long-acting bronchodilators, either singly or in combination, provide sustained bronchodilation and lung deflation that contribute to relief of dyspnea in those with COPD. Opioid medications reduce breathing discomfort by decreasing respiratory drive (and associated corollary discharge), altering central perception, and/or decreasing anxiety. For individuals suffering from refractory dyspnea, a low dose of an opioid is recommended initially, and then titrated to achieve the lowest effective dose based on patient ratings. Acupuncture, bronchoscopic volume reduction, and noninvasive open ventilation are experimental approaches shown to ameliorate dyspnea in patients with COPD, but require confirmatory evidence before clinical use.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.