Inhaled furosemide greatly alleviates the sensation of experimentally induced dyspnea

Nebulised furosemide for the treatment of patients with obstructive lung disease: a systematic review protocol

INTRODUCTION

Obstructive lung diseases (OLDs) such as asthma and chronic obstructive pulmonary disease are major global sources of morbidity and mortality. Current treatments broadly include bronchodilators such as beta agonists/antimuscarinics and anti-inflammatory agents such as steroids. Despite therapy patients still experience exacerbations of their diseases and overall decline over time. Nebulised furosemide may have a novel use in the treatment of OLD. Multiple small studies have shown improvement in pulmonary function as well as dyspnoea. This systematic review will aim to summarise and analyse the existing literature on nebulised furosemide use in OLD to guide treatment and future studies.

METHODS AND ANALYSIS

We will identify all experimental studies using nebulised/inhaled furosemide in patients with asthma or chronic obstructive pulmonary disease that report any outcome. Databases will include EMBASE, MEDLINE, Cochrane Database of Systematic Reviews, ACP Journal Club, Database of Abstracts of Reviews of Effects, Cochrane Clinical Answers, Cochrane Central Register of Controlled Trials, Cochrane Methodology Register, Health Technology Assessment and the NHS Economic Evaluation Database (1995-2015). We will also search ClinicalTrials.gov and the WHO-International Clinical Trials Registry Platform. Two reviewers will independently determine trial eligibility. For each included trial, we will perform duplicate independent data extraction, risk of bias assessment and evaluation of the quality of evidence using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

ETHICS AND DISSEMINATION

Ethical approval will not be applicable to this systematic review. The results of the study will be communicated through publication in peer-reviewed journals.

PROSPERO REGISTRATION NUMBER

CRD42021284680.

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.

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.

Inhalation Delivery for the Treatment and Prevention of COVID-19 Infection

Coronavirus disease-2019 (COVID-19) is caused by coronavirus-2 (SARS-CoV-2) and has produced a global pandemic. As of 22 June 2021, 178 million people have been affected worldwide, and 3.87 million people have died from COVID-19. According to the Centers for Disease Control and Prevention (CDC) of the United States, COVID-19 virus is primarily transmitted between people through respiratory droplets and contact routes. Since the location of initial infection and disease progression is primarily through the lungs, the inhalation delivery of drugs directly to the lungs may be the most appropriate route of administration for treating COVID-19. This review article aims to present possible inhalation therapeutics and vaccines for the treatment of COVID-19 symptoms. This review covers the comparison between SARS-CoV-2 and other coronaviruses such as SARS-CoV/MERS, inhalation therapeutics for the treatment of COVID-19 symptoms, and vaccines for preventing infection, as well as the current clinical status of inhaled therapeutics and vaccines.

Air Hunger: A Primal Sensation and a Primary Element of Dyspnea

The sensation that develops as a long breath hold continues is what this article is about. We term this sensation of an urge to breathe "air hunger." Air hunger, a primal sensation, alerts us to a failure to meet an urgent homeostatic need maintaining gas exchange. Anxiety, frustration, and fear evoked by air hunger motivate behavioral actions to address the failure. The unpleasantness and emotional consequences of air hunger make it the most debilitating component of clinical dyspnea, a symptom associated with respiratory, cardiovascular, and metabolic diseases. In most clinical populations studied, air hunger is the predominant form of dyspnea (colloquially, shortness of breath). Most experimental subjects can reliably quantify air hunger using rating scales, that is, there is a consistent relationship between stimulus and rating. Stimuli that increase air hunger include hypercapnia, hypoxia, exercise, and acidosis; tidal expansion of the lungs reduces air hunger. Thus, the defining experimental paradigm to evoke air hunger is to elevate the drive to breathe while mechanically restricting ventilation. Functional brain imaging studies have shown that air hunger activates the insular cortex (an integration center for perceptions related to homeostasis, including pain, food hunger, and thirst), as well as limbic structures involved with anxiety and fear. Although much has been learned about air hunger in the past few decades, much remains to be discovered, such as an accepted method to quantify air hunger in nonhuman animals, fundamental questions about neural mechanisms, and adequate and safe methods to mitigate air hunger in clinical situations. © 2021 American Physiological Society. Compr Physiol 11:1449-1483, 2021.

Mechanisms underlying the sensation of dyspnea

Dyspnea is defined as a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. It is a common symptom among patients with respiratory diseases that reduces daily activities, induces deconditioning, and is self-perpetuating. Although clinical interventions are needed to reduce dyspnea, its underlying mechanism is poorly understood depending on the intertwined peripheral and central neural mechanisms as well as emotional factors. Nonetheless, experimental and clinical observations suggest that dyspnea results from dissociation or a mismatch between the intended respiratory motor output set caused by the respiratory neuronal network in the lower brainstem and the ventilatory output accomplished. The brain regions responsible for detecting the mismatch between the two are not established. The mechanism underlying the transmission of neural signals for dyspnea to higher sensory brain centers is not known. Further, information from central and peripheral chemoreceptors that control the milieu of body fluids is summated at higher brain centers, which modify dyspneic sensations. The mental status also affects the sensitivity to and the threshold of dyspnea perception. The currently used methods for relieving dyspnea are not necessarily fully effective. The search for more effective therapy requires further insights into the pathophysiology of dyspnea.

Combination adjunctive nebulized furosemide and salbutamol versus single agent therapy in COPD patients: A randomized controlled trial

Background

COPD patients often require multiple therapies to enhance their lung function and reduce their symptoms in exacerbations. This study aimed to investigate the relative effects of combination adjunctive nebulized furosemide and salbutamol therapy versus single agent treatment in COPD patients.

Methods

Sixty-nine COPD patients were randomly divided into two groups. The first group (G1, 34 cases) received salbutamol in their first episode. The second group (G2, 35 cases) received furosemide in their first episode. Spirometry indices (FEV1, FVC, and FEV1/FVC), mMRC and BORG (COPD assessment) were assessed and recorded for all patients.To study the efficacy of combination adjunctive therapy, in 2nd episodes, the nebulized furosemide was added to nebulized salbutamol in the G1, and nebulized salbutamol was added to nebulized furosemide in G2. The aforementioned indices were then re-assessed.

Results

The mean age was (64.92 ± 11.71 years, 55% males. The use of nebulized furosemide and salbutamol as single agents slightly improved the spirometeric parameters, but it was not noteworthy compared to the significant improvement of the FEV1, FVC, FEV1/FVC, mMRC, and Borg parameters with combination therapy (p-value< 0.001). In the first episode, there was no difference in spirometeric indices, between groups (p-value > 0.1), so furosemide is considered as effective as nebulized salbutamol. Also, the results of sequential drugs administration, in the two groups was similar.

Conclusion

Conjunction of nebulized furosemide and salbutamol is more effective than single therapy and can be considered as preferred drug regimen without any reported side effect in the treatment of COPD.

Is Inhaled Furosemide a Potential Therapeutic for COVID-19?

The potentially lethal infection caused by the novel Severe Acute Respiratory Disease Coronavirus-2 (SARS-CoV-2) has evolved into a global crisis. Following the initial viral infection is the host inflammatory response that frequently results in excessive secretion of inflammatory cytokines (e.g., IL-6 and TNFα), developing into a self-targeting, toxic "cytokine storm" causing critical pulmonary tissue damage. The need for a therapeutic that is available immediately is growing daily but the de novo development of a vaccine may take years. Therefore, repurposing of approved drugs offers a promising approach to address this urgent need. Inhaled furosemide, a small molecule capable of inhibiting IL-6 and TNFα, may be an agent capable of treating the Coronavirus Disease 2019 cytokine storm in both resource-rich and developing countries. Furosemide is a "repurpose-able" small molecule therapeutics, that is safe, easily synthesized, handled, and stored, and is available in reasonable quantities worldwide.

Controlled Delivery of 80 mg Aerosol Furosemide Does Not Achieve Consistent Dyspnea Relief in Patients

PURPOSE

Aerosol furosemide may be an option to treat refractory dyspnea, though doses, methods of delivery, and outcomes have been variable. We hypothesized that controlled delivery of high dose aerosol furosemide would reduce variability of dyspnea relief in patients with underlying pulmonary disease.

METHODS

Seventeen patients with chronic exertional dyspnea were recruited. Patients rated recently recalled breathing discomfort on a numerical rating scale (NRS) and the multidimensional dyspnea profile (MDP). They then performed graded exercise using an arm-ergometer. The NRS was completed following each exercise grade, and the MDP was repeated after a pre-defined dyspnea threshold was reached. During separate visits, patients received either aerosol saline or 80 mg of aerosol furosemide in a randomized, double-blind, crossover design. After treatment, graded exercise to the pre-treatment level was repeated, followed by completion of the NRS and MDP. Treatment effect was defined as the difference between pre- and post-treatment NRS at end exercise, expressed in absolute terms as % Full Scale. "Responders" were defined as those showing treatment effect ≥ 20% of full scale.

RESULTS

Final analysis included 15 patients. Neither treatment produced a statistically significant change in NRS and there was no significant difference between treatments (p = 0.45). There were four "responders" and one patient whose dyspnea worsened with furosemide; two patients were responders with saline, of whom one also responded to furosemide. No adverse events were reported.

CONCLUSIONS

High dose controlled delivery aerosol furosemide was not statistically different from saline placebo at reducing exercise-induced dyspnea. However, a clinically meaningful improvement was noted in some patients.

Updates in opioid and nonopioid treatment for chronic breathlessness

PURPOSE OF REVIEW

Chronic breathlessness is a troublesome symptom experienced by people with advanced malignant and nonmalignant disease. Disease-directed therapies are often insufficient in the management of chronic breathlessness. Therefore, pharmacological and nonpharmacological breathlessness-specific interventions should be considered for select patients.

RECENT FINDINGS

There is some evidence to support the use of low-dose opioids (≤30 mg morphine equivalents per day) for the relief of breathlessness in the short term. However, additional studies are needed to understand the efficacy of opioids for chronic breathlessness in the long term.Nonopioid therapies, including inspiratory muscle training, fan-to-face therapy, L-menthol and inhaled nebulized furosemide show some promise for the relief of breathlessness in advanced disease. There is insufficient evidence to support the use of anxiolytics and benzodiazepines and cannabis for chronic breathlessness.

SUMMARY

More research is needed to identify therapies for the management of chronic breathlessness.

Inhaled furosemide for relief of air hunger versus sense of breathing effort: a randomized controlled trial

Background

Inhaled furosemide offers a potentially novel treatment for dyspnoea, which may reflect modulation of pulmonary stretch receptor feedback to the brain. Specificity of relief is unclear because different neural pathways may account for different components of clinical dyspnoea. Our objective was to evaluate if inhaled furosemide relieves the air hunger component (uncomfortable urge to breathe) but not the sense of breathing work/effort of dyspnoea.

Methods

A randomised, double blind, placebo-controlled crossover trial in 16 healthy volunteers studied in a university research laboratory. Each participant received 3 mist inhalations (either 40 mg furosemide or 4 ml saline) separated by 30–60 min on 2 test days. Each participant was randomised to mist order ‘furosemide-saline-furosemide’ (n- = 8) or ‘saline-furosemide-saline’ (n = 8) on both days. One day involved hypercapnic air hunger tests (mean ± SD PCO₂ = 50 ± 3.7 mmHg; constrained ventilation = 9 ± 1.5 L/min), the other involved work/effort tests with targeted ventilation (17 ± 3.1 L/min) and external resistive load (20cmH₂O/L/s). Primary outcome was ratings of air hunger or work/effort every 15 s on a visual analogue scale. During saline inhalations, 1.5 mg furosemide was infused intravenously to match the expected systemic absorption from the lungs when furosemide is inhaled. Corresponding infusions of saline during furosemide inhalations maintained procedural blinding. Average visual analogue scale ratings (%full scale) during the last minute of air hunger or work/effort stimuli were analysed using Linear Mixed Methods.

Results

Data from all 16 participants were analysed. Inhaled furosemide relative to inhaled saline significantly improved visual analogues scale ratings of air hunger (Least Squares Mean ± SE − 9.7 ± 2%; p = 0.0015) but not work/effort (+ 1.6 ± 2%; p = 0.903). There were no significant adverse events.

Conclusions

Inhaled furosemide was effective at relieving laboratory induced air hunger but not work/effort in healthy adults; this is consistent with the notion that modulation of pulmonary stretch receptor feedback by inhaled furosemide leads to dyspnoea relief that is specific to air hunger, the most unpleasant quality of dyspnoea.

Funding

Oxford Brookes University Central Research Fund.

Trial registration

ClinicalTrials.gov Identifier: NCT02881866. Retrospectively registered on 29th August 2018.

Effect of Inhaled Nebulized Furosemide (40 and 120 mg) on Breathlessness during Exercise in the Presence of External Thoracic Restriction in Healthy Men

Inhalation of nebulized furosemide has been shown to alleviate breathlessness provoked experimentally in health and disease; however, it remains unclear whether the efficacy of nebulized furosemide on breathlessness is dose-dependent. We tested the hypothesis that inhaled nebulized furosemide would be associated with a dose-dependent relief of breathlessness during exercise testing in the setting of abnormal restrictive constraints on tidal volume (V_T) expansion. In a randomized, double-blind, crossover study, 24 healthy men aged 25.3 ± 1.2 years (mean ± SE) completed a symptom-limited constant-load cycle endurance exercise test in the setting of external thoracic restriction via chest wall strapping to reduce vital capacity by ~20% following single-dose inhalation nebulized furosemide (40 and 120 mg) and 0.9% saline. Compared with 0.9% saline, neither 40 nor 120 mg of inhaled nebulized furosemide had an effect on ratings of perceived breathlessness during exercise or an effect on cardiometabolic, ventilatory, breathing pattern, or dynamic operating lung volume responses during exercise. Urine production rate, the percentage of participants reporting an "urge to urinate" and the intensity of perceived "urge to urinate" were all significantly greater after inhaling the 120 mg furosemide solution compared with both 0.9% saline and 40 mg furosemide solutions. We concluded that, under the experimental conditions of this study, inhalation of nebulized furosemide at doses of 40 and 120 mg did not alleviate breathlessness during exercise in healthy men.

Aerosol furosemide for dyspnea: Controlled delivery does not improve effectiveness

Aerosolized furosemide has been shown to relieve dyspnea; nevertheless, all published studies have shown great variability in response. This dyspnea relief is thought to result from the stimulation of slowly adapting pulmonary stretch receptors simulating larger tidal volume. We hypothesized that better control over aerosol administration would produce more consistent dyspnea relief; we used a clinical ventilator to control inspiratory flow and tidal volume. Twelve healthy volunteers inhaled furosemide (40mg) or placebo in a double blind, randomized, crossover study. Breathing Discomfort was induced by hypercapnia during constrained ventilation before and after treatment. Both treatments reduced breathing discomfort by 20% full scale. Effectiveness of aerosol furosemide treatment was weakly correlated with larger tidal volume. Response to inhaled furosemide was inversely correlated to furosemide blood level, suggesting that variation among subjects in the fate of deposited drug may determine effectiveness. We conclude that control of aerosol delivery conditions does not improve consistency of treatment effect; we cannot, however, rule out placebo effect.

Aerosol furosemide for dyspnea: High-dose controlled delivery does not improve effectiveness

Published studies have shown great variability in response when aerosolized furosemide has been tested as a palliative treatment for dyspnea. We hypothesized that a higher furosemide dose with controlled aerosol administration would produce consistent dyspnea relief. We optimized deposition by controlling inspiratory flow (300-500mL/s) and tidal volume (15% predicted vital capacity) while delivering 3.4μm aerosol from either saline or 80mg of furosemide. We induced dyspnea in healthy subjects by varying inspired PCO₂ while restricting minute ventilation. Subjects rated "Breathing Discomfort" on a Visual Analog Scale (BDVAS, 100% Full Scale≡intolerable). At the PET_CO2 producing 60% BDVAS pre-treatment, furosemide produced a clinically meaningful reduction of BDVAS (i.e., >20% FS) in 5/11 subjects; saline reduced dyspnea in 3/11 subjects; neither treatment worsened dyspnea in any subject. Furosemide and saline treatment effects were not statistically different. There were no significant adverse events. Higher furosemide dose and controlled delivery did not improve consistency of treatment effect compared with prior studies.

Fooling the brain to alleviate dyspnoea

Dyspnoea affects a multitude of patients with a multitude of diseases, and therefore concerns a multitude of physicians and other healthcare professionals. In view of the physical and psychological distress associated with dyspnoea, and in view of the pervasive impact of dyspnoea on the patient's psychological state and social life [1, 2], relieving dyspnoea should constitute a leading and universal clinical goal. Some have even proposed that failing to provide a patient with dyspnoea with “state of the art” management of this symptom would constitute an infringement of human rights [3, 4].

The application of a stream of air onto the face by a hand-held fan has a real place in the treatment of dyspnoea http://ow.ly/tKJk30dJ5Pv

Vagal Afferent Innervation of the Airways in Health and Disease

Vagal sensory neurons constitute the major afferent supply to the airways and lungs. Subsets of afferents are defined by their embryological origin, molecular profile, neurochemistry, functionality, and anatomical organization, and collectively these nerves are essential for the regulation of respiratory physiology and pulmonary defense through local responses and centrally mediated neural pathways. Mechanical and chemical activation of airway afferents depends on a myriad of ionic and receptor-mediated signaling, much of which has yet to be fully explored. Alterations in the sensitivity and neurochemical phenotype of vagal afferent nerves and/or the neural pathways that they innervate occur in a wide variety of pulmonary diseases, and as such, understanding the mechanisms of vagal sensory function and dysfunction may reveal novel therapeutic targets. In this comprehensive review we discuss historical and state-of-the-art concepts in airway sensory neurobiology and explore mechanisms underlying how vagal sensory pathways become dysfunctional in pathological conditions.

Non-opioid medications for the relief of chronic breathlessness: current evidence

INTRODUCTION

To evaluate systematically randomised clinical trials investigating non-opioid medications for the management and treatment of chronic breathlessness. Areas covered: The evidence for the role of benzodiazepines, anxiolytics, selective serotonin re-uptake inhibitors (SSRIs), tricyclic antidepressants, antihistamines, cannabinoids, nebulized furosemide and herbal-based treatments were critically reviewed. Search of the Clinical Trials Registry (Clinicaltrial.gov) identified ongoing studies expected to generate new data in the near future in several classes of non-opioid medications for their net effect on chronic breathlessness. Expert commentary: Morphine still has the best level of evidence for the symptomatic treatment of chronic breathlessness. Non-opioid treatments for chronic breathlessness are less studied than morphine and morphine-related medications although evidence is emerging in relation to some options. Currently, there is insufficient evidence to recommend non-opioids in the routine treatment of chronic breathlessness. There is a need to find agents, new as well as re-purposed, that can be used as alternative therapies to opioids for chronic breathlessness for people who are unable to tolerate morphine.

The Effect of Aerosol Saline on Laboratory-Induced Dyspnea

PURPOSE

In the 'placebo arm' of a recent study, we found that aerosol saline (sham treatment) produced substantial relief of laboratory-induced dyspnea (Breathing discomfort-BD) in nearly half the subjects. The sham intervention included a physiological change, and instructions to subjects could have produced expectation of dyspnea relief. In the present study, we attempted to discover whether the response to sham aerosol was driven by behavioral or physiological aspects of the intervention.

METHODS

Dyspnea (air hunger) was evoked by constraining tidal volume during graded hypercapnia. We measured [Formula: see text] versus BD relationship before and after aerosol saline. To minimize subjects' expectations of dyspnea relief, participants were clearly instructed that we would only deliver saline aerosol. In Protocol 1, we delivered aerosol saline with a ventilator (mimicking our prior study); in Protocol 2, we delivered aerosol without a ventilator.

RESULTS

Administration of aerosol saline had little effect on BD in this group of subjects with one exception: one subject experienced appreciable reduction in BD in Protocol 1. This treatment effect was less in Protocol 2. The two most likely explanations are (a) that procedures surrounding ventilator administration of aerosol produced a psychological placebo treatment effect even though the subject knew a drug was not given; (b) there were behavioral changes in breathing undetected by our measurements of respiratory flow and volume that altered the subjects comfort.

CONCLUSION

When the expectation of treatment effect is minimized, a significant reduction in dyspnea in response to saline placebo is uncommon but not impossible.

Pharmacological treatment optimization for stable chronic obstructive pulmonary disease. Proposals from the Société de Pneumologie de Langue Française

The Société de Pneumologie de Langue Française proposes a decision algorithm on long-term pharmacological COPD treatment. A working group reviewed the literature published between January 2009 and May 2016. This document lays out proposals and not guidelines. It only focuses on pharmacological treatments except vaccinations, smoking cessation treatments and oxygen therapy. Any COPD diagnosis, based on pulmonary function tests, should lead to recommend smoking cessation, vaccinations, physical activity, pulmonary rehabilitation in case of activity limitation, and short-acting bronchodilators. Symptoms like dyspnea and exacerbations determine the therapeutic choices. In case of daily dyspnea and/or exacerbations, a long-acting bronchodilator should be suggested (beta-2 agonist, LABA or anticholinergics, LAMA). A clinical and lung function reevaluation is suggested 1 to 3 months after any treatment modification and every 3-12 months according to the severity of the disease. In case of persisting dyspnea, a fixed dose LABA+LAMA combination improves pulmonary function (FEV1), quality of life, dyspnea and decreases exacerbations without increasing side effects. In case of frequent exacerbations and a FEV1≤70%, a fixed dose long-acting bronchodilator combination or a LABA+ inhaled corticosteroids (ICS) combination can be proposed. A triple combination (LABA+LAMA+ICS) is indicated when exacerbations persist despite one of these combinations. Dyspnea in spite of a bronchodilator combination or exacerbations in spite of a triple combination should lead to consider other pharmacological treatments (theophylline if dyspnea, macrolides if exacerbations, low-dose opioids if refractory dyspnea).

Association of Descriptors of Breathlessness With Diagnosis and Self-Reported Severity of Breathlessness in Patients With Advanced Chronic Obstructive Pulmonary Disease or Cancer

CONTEXT

Verbal descriptors are important in understanding patients' experience of breathlessness.

OBJECTIVES

The aim of this study was to examine the association between selection of breathlessness descriptors, diagnosis, self-reported severity of breathlessness and self-reported distress due to breathlessness.

METHODS

We studied 132 patients grouped according to their diagnosis of advanced chronic obstructive pulmonary disease (n = 69) or advanced cancer (n = 63), self-reported severity of breathlessness as mild breathlessness (Numerical Rating Scale [NRS] ≤ 3, n = 53), moderate breathlessness (4 ≤ NRS ≥ 6, n = 59) or severe breathlessness (NRS ≥ 7, n = 20), and distress due to breathlessness as mild distress (NRS ≤ 3, n = 31), moderate distress (4 ≤ NRS ≥ 6, n = 44), or severe distress (NRS ≥ 7, n = 57). Patients selected three breathlessness descriptors. The relationship between descriptors selected and patient groups was evaluated by cluster analysis.

RESULTS

Different combinations of clusters were associated with each diagnostic group; the cluster chest tightness was associated with cancer patients. The association of clusters with patient groups differed depending on their severity of breathlessness and their distress due to breathlessness. The air hunger cluster was associated with patients with moderate or severe breathlessness, and the chest tightness cluster was associated with patients with mild breathlessness. The air hunger cluster was associated with patients with severe distress due to breathlessness.

CONCLUSION

The relationship between clusters and diagnosis is not robust enough to use the descriptors to identify the primary cause of breathlessness. Further work exploring how use of breathlessness descriptors reflects the severity of breathlessness and distress due to breathlessness could enable the descriptors to evaluate patient status and target interventions.

Furosemide

Therapeutic Reviews aim to provide essential independent information for health professionals about drugs used in palliative and hospice care. Additional content is available on www.palliativedrugs.com. Country-specific books (Hospice and Palliative Care Formulary USA, and Palliative Care Formulary, British and Canadian editions) are also available and can be ordered from www.palliativedrugs.com. The series editors welcome feedback on the articles (hq@palliativedrugs.com).

Multidimensional Dyspnea Profile: an instrument for clinical and laboratory research

There is growing awareness that dyspnoea, like pain, is a multidimensional experience, but measurement instruments have not kept pace. The Multidimensional Dyspnea Profile (MDP) assesses overall breathing discomfort, sensory qualities, and emotional responses in laboratory and clinical settings. Here we provide the MDP, review published evidence regarding its measurement properties and discuss its use and interpretation. The MDP assesses dyspnoea during a specific time or a particular activity (focus period) and is designed to examine individual items that are theoretically aligned with separate mechanisms. In contrast, other multidimensional dyspnoea scales assess recalled recent dyspnoea over a period of days using aggregate scores.

Previous psychophysical and psychometric studies using the MDP show that: 1) subjects exposed to different laboratory stimuli could discriminate between air hunger and work/effort sensation, and found air hunger more unpleasant; 2) the MDP immediate unpleasantness scale (A₁) was convergent with common dyspnoea scales; 3) in emergency department patients, two domains were distinguished (immediate perception, emotional response); 4) test–retest reliability over hours was high; 5) the instrument responded to opioid treatment of experimental dyspnoea and to clinical improvement; 6) convergent validity with common instruments was good; and 7) items responded differently from one another as predicted for multiple dimensions.

The Multidimensional Dyspnea Profile provides a unified, reliable instrument for both clinical and laboratory researchhttp://ow.ly/Ix8ic

The efficacy of nebulized furosemide and salbutamol compared with salbutamol alone in reactive airway disease: a double blind randomized, clinical trial

We undertook this randomized clinical trial to investigate whether adding furosemide to salbutamol could improve the peak expiratory flow rate (PEFR) and clinical signs of reactive airway disease (RAD) patients. Eligible 18- to 55-year-old patients were randomly divided into intervention and control groups. Patients received 5 mg of nebulized salbutamol and 40 mg of nebulized furosemide in the intervention group and 5 mg of nebulized salbutamol alone in the control group. Patients in both groups received 100 mg of methylprednisolone intravenously stat. Severity of the RAD was estimated before and 45 minutes after treatment in both groups. PEFR was estimated before treatment and at 15, 30, and 45 minutes later. Ninety patients were enrolled, 45 in each group. There were no significant differences between two groups regarding gender, mean age, and normalized PEFR. The baseline mean PEFR was not significantly different between groups (P = 0.58). A repeated measure analysis of variance revealed that the differences between the two treatments was significant (P = 0.0001) and the behavior of two treatments was not similar across the time (P = 0.001). Comparison of clinical severity of acute RAD revealed no significant differences between groups at the end of the trial (0.06). This study showed that adding nebulized furosemide to salbutamol in RAD patients improved PEFR.

Inspiratory high frequency airway oscillation attenuates resistive loaded dyspnea and modulates respiratory function in young healthy individuals

Direct chest-wall percussion can reduce breathlessness in Chronic Obstructive Pulmonary Disease and respiratory function may be improved, in health and disease, by respiratory muscle training (RMT). We tested whether high-frequency airway oscillation (HFAO), a novel form of airflow oscillation generation can modulate induced dyspnoea and respiratory strength and/or patterns following 5 weeks of HFAO training (n = 20) compared to a SHAM-RMT (conventional flow-resistive RMT) device (n = 15) in healthy volunteers (13 males; aged 20–36 yrs). HFAO causes oscillations with peak-to-peak amplitude of 1 cm H₂O, whereas the SHAM-RMT device was identical but created no pressure oscillation. Respiratory function, dyspnoea and ventilation during 3 minutes of spontaneous resting ventilation, 1 minute of maximal voluntary hyperventilation and 1 minute breathing against a moderate inspiratory resistance, were compared PRE and POST 5-weeks of training (2×30 breaths at 70% peak flow, 5 days a week). Training significantly reduced NRS dyspnoea scores during resistive loaded ventilation, both in the HFAO (p = 0.003) and SHAM-RMT (p = 0.005) groups. Maximum inspiratory static pressure (cm H₂O) was significantly increased by HFAO training (vs. PRE; p<0.001). Maximum inspiratory dynamic pressure was increased by training in both the HFAO (vs. PRE; p<0.001) and SHAM-RMT (vs. PRE; p = 0.021) groups. Peak inspiratory flow rate (L.s⁻¹) achieved during the maximum inspiratory dynamic pressure manoeuvre increased significantly POST (vs. PRE; p = 0.001) in the HFAO group only. HFAO reduced inspiratory resistive loading–induced dyspnoea and augments static and dynamic maximal respiratory manoeuvre performance in excess of flow-resistive IMT (SHAM-RMT) in healthy individuals without the respiratory discomfort associated with RMT.

Physiological mechanisms of dyspnea during exercise with external thoracic restriction: role of increased neural respiratory drive

We tested the hypothesis that neuromechanical uncoupling of the respiratory system forms the mechanistic basis of dyspnea during exercise in the setting of "abnormal" restrictive constraints on ventilation (VE). To this end, we examined the effect of chest wall strapping (CWS) sufficient to mimic a "mild" restrictive lung deficit on the interrelationships between VE, breathing pattern, dynamic operating lung volumes, esophageal electrode-balloon catheter-derived measures of the diaphragm electromyogram (EMGdi) and the transdiaphragmatic pressure time product (PTPdi), and sensory intensity and unpleasantness ratings of dyspnea during exercise. Twenty healthy men aged 25.7 ± 1.1 years (means ± SE) completed symptom-limited incremental cycle exercise tests under two randomized conditions: unrestricted control and CWS to reduce vital capacity (VC) by 21.6 ± 0.5%. Compared with control, exercise with CWS was associated with 1) an exaggerated EMGdi and PTPdi response; 2) no change in the relationship between EMGdi and each of tidal volume (expressed as a percentage of VC), inspiratory reserve volume, and PTPdi, thus indicating relative preservation of neuromechanical coupling; 3) increased sensory intensity and unpleasantness ratings of dyspnea; and 4) no change in the relationship between increasing EMGdi and each of the intensity and unpleasantness of dyspnea. In conclusion, the increased intensity and unpleasantness of dyspnea during exercise with CWS could not be readily explained by increased neuromechanical uncoupling but likely reflected the awareness of increased neural respiratory drive (EMGdi) needed to achieve any given VE during exercise in the setting of "abnormal" restrictive constraints on tidal volume expansion.

An official American Thoracic Society statement: update on the mechanisms, assessment, and management of dyspnea

BACKGROUND

Dyspnea is a common, distressing symptom of cardiopulmonary and neuromuscular diseases. Since the ATS published a consensus statement on dyspnea in 1999, there has been enormous growth in knowledge about the neurophysiology of dyspnea and increasing interest in dyspnea as a patient-reported outcome.

PURPOSE

The purpose of this document is to update the 1999 ATS Consensus Statement on dyspnea.

METHODS

An interdisciplinary committee of experts representing ATS assemblies on Nursing, Clinical Problems, Sleep and Respiratory Neurobiology, Pulmonary Rehabilitation, and Behavioral Science determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant expertise. The final content of this statement was agreed upon by all members.

RESULTS

Progress has been made in clarifying mechanisms underlying several qualitatively and mechanistically distinct breathing sensations. Brain imaging studies have consistently shown dyspnea stimuli to be correlated with activation of cortico-limbic areas involved with interoception and nociception. Endogenous and exogenous opioids may modulate perception of dyspnea. Instruments for measuring dyspnea are often poorly characterized; a framework is proposed for more consistent identification of measurement domains.

CONCLUSIONS

Progress in treatment of dyspnea has not matched progress in elucidating underlying mechanisms. There is a critical need for interdisciplinary translational research to connect dyspnea mechanisms with clinical treatment and to validate dyspnea measures as patient-reported outcomes for clinical trials.

An official American Thoracic Society statement: update on the mechanisms, assessment, and management of dyspnea

BACKGROUND

Dyspnea is a common, distressing symptom of cardiopulmonary and neuromuscular diseases. Since the ATS published a consensus statement on dyspnea in 1999, there has been enormous growth in knowledge about the neurophysiology of dyspnea and increasing interest in dyspnea as a patient-reported outcome.

PURPOSE

The purpose of this document is to update the 1999 ATS Consensus Statement on dyspnea.

METHODS

An interdisciplinary committee of experts representing ATS assemblies on Nursing, Clinical Problems, Sleep and Respiratory Neurobiology, Pulmonary Rehabilitation, and Behavioral Science determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant expertise. The final content of this statement was agreed upon by all members.

RESULTS

Progress has been made in clarifying mechanisms underlying several qualitatively and mechanistically distinct breathing sensations. Brain imaging studies have consistently shown dyspnea stimuli to be correlated with activation of cortico-limbic areas involved with interoception and nociception. Endogenous and exogenous opioids may modulate perception of dyspnea. Instruments for measuring dyspnea are often poorly characterized; a framework is proposed for more consistent identification of measurement domains.

CONCLUSIONS

Progress in treatment of dyspnea has not matched progress in elucidating underlying mechanisms. There is a critical need for interdisciplinary translational research to connect dyspnea mechanisms with clinical treatment and to validate dyspnea measures as patient-reported outcomes for clinical trials.

Dyspnea review for the palliative care professional: treatment goals and therapeutic options

Although dyspnea is frequently encountered in the palliative care setting, its optimal management remains uncertain. Clinical approaches begin with accurate assessment, as delineated in part one of this two-part series. Comprehensive dyspnea assessment, which encompasses the physical, emotional, social, and spiritual aspects of this complex symptom, guide the clinician in choosing therapeutic approaches herein presented as part two. Global management of dyspnea is appropriate both as complementary to disease-targeted treatments that target the underlying etiology, and as the sole focus when the symptom has become intractable, disease is maximally treated, and goals of care shift to comfort and quality of life. In this setting, current evidence supports the use of oral or parenteral opioids as the mainstay of dyspnea management, and of inhaled furosemide and anxiolytics as adjuncts. Nonpharmacologic interventions such as acupuncture and pulmonary rehabilitation have potential effectiveness, although further research is needed, and use of a simple fan warrants consideration given its potential benefit and minimal burden and cost.

Using laboratory models to test treatment: morphine reduces dyspnea and hypercapnic ventilatory response

RATIONALE

Opioids are commonly used to relieve dyspnea, but clinical data are mixed and practice varies widely.

OBJECTIVES

Evaluate the effect of morphine on dyspnea and ventilatory drive under well-controlled laboratory conditions.

METHODS

Six healthy volunteers received morphine (0.07 mg/kg) and placebo intravenously on separate days (randomized, blinded). We measured two responses to a CO(2) stimulus: (1) perceptual response (breathing discomfort; described by subjects as "air hunger") induced by increasing partial pressure of end-tidal carbon dioxide (Pet(CO2)) during restricted ventilation, measured with a visual analog scale (range, "neutral" to "intolerable"); and (2) ventilatory response, measured in separate trials during unrestricted breathing.

MEASUREMENTS AND MAIN RESULTS

We determined the Pet(CO2) that produced a 60% breathing discomfort rating in each subject before morphine (median, 8.5 mm Hg above resting Pet(CO2)). At the same Pet(CO2) after morphine administration, median breathing discomfort was reduced by 65% of its pretreatment value; P < 0.001. Ventilation fell 28% at the same Pet(CO2); P < 0.01. The effect of morphine on breathing discomfort was not significantly correlated with the effect on ventilatory response. Placebo had no effect.

CONCLUSIONS

(1) A moderate morphine dose produced substantial relief of laboratory dyspnea, with a smaller reduction of ventilation. (2) In contrast to an earlier laboratory model of breathing effort, this laboratory model of air hunger established a highly significant treatment effect consistent in magnitude with clinical studies of opioids. Laboratory studies require fewer subjects and enable physiological measurements that are difficult to make in a clinical setting. Within-subject comparison of the response to carefully controlled laboratory stimuli can be an efficient means to optimize treatments before clinical trials.

Management of dyspnea in patients with chronic obstructive pulmonary disease

A progressive and debilitating illness, chronic obstructive pulmonary disease (COPD) has major worldwide impact. In addition to the care for underlying causes of disease, COPD treatment involves palliative intervention to address associated symptoms; in later stages of disease, when the underlying disease has been maximally treated, symptom management assumes primacy as the goal of care. Dyspnea is the most distressing symptom experienced by COPD patients. When dyspnea cannot be relieved by traditional COPD management strategies (i.e., "refractory dyspnea"), the goal of care shifts from prolonged survival to minimized symptoms, improved function, and enhanced quality of life. Numerous pharmacologic and non-pharmacologic interventions are available to achieve these goals, but supporting evidence is variable. This review summarizes options for managing refractory dyspnea in COPD patients, referring to the available evidence and highlighting areas for further investigation. Topics include oxygen, opioids, psychotropic drugs, inhaled frusemide, Heliox28, nutrition, psychosocial support, and breathing techniques.

Airway nerves and dyspnea associated with inflammatory airway disease

The neurobiology of dyspnea is varied and complex, but there is little doubt that vagal nerves within the airways are capable of causing or modulating some dyspneic sensations, especially those associated with inflammatory airway diseases. A major contributor to the dyspnea associated with inflammatory airway disease is explained by airway narrowing and increases in the resistance to airflow. The autonomic (parasympathetic) airway nerves directly contribute to this by regulating bronchial smooth muscle tone and mucus secretion. In addition, a component of the information reaching the brainstem via airway mechanosensing and nociceptive afferent nerves likely contributes to the overall sensations of breathing. The airway narrowing can lead to activation of low threshold mechanosensitive stretch receptors, and vagal and spinal C-fibers as well as some rapidly adapting stretch receptor in the airways that are directly activated by various aspects of the inflammatory response. Inflammatory mediators can induce long lasting changes in afferent nerve activity by modulating the expression of key genes. The net effect of the increase in afferent traffic to the brainstem modulates synaptic efficacy at the second-order neurons via various mechanisms collectively referred to as central sensitization. Many studies have shown that stimuli that activate bronchopulmonary afferent nerves can lead to dyspnea in healthy subjects. A logical extension of the basic research on inflammation and sensory nerve function is that the role of vagal sensory nerve in causing or shaping dyspneic sensations will be exaggerated in those suffering from inflammatory airway disease.

Dyspnoea in children. Does development alter the perception of breathlessness?

Dyspnoea, the perception of an unpleasant and/or uncomfortable sensation of breathlessness, offers several physiological, anatomical and teleological analogies with pain. Pain perception has been shown to exist in the newborn, suggesting that dyspnoea may also occur from birth onwards. The perception of breathlessness will be subservient to developmental changes in the behaviour of sensors and lung and muscular receptors implicated in dyspnoea, some of which are known to be active at time of birth. For example, perinatal resetting of the arterial chemoreceptor could lead to transient depression of the dyspnoeic response to hypoxia. However, though early evoked ventilatory responses and peripheral receptor maturation do exist, dyspnoea will only occur if the corresponding central neural circuitry undergoes parallel maturation. Our knowledge of dyspnoea in later childhood is based on a small number of clinical or psychophysical studies, predominantly dealing with asthma and exercise. There is a thus a clear need for systematic assessment of the existence and severity of dyspnoea sensing in younger children that takes into account its role as an alarm mechanism for triggering adaptive and/or protective responses.