Does nebulized fentanyl relieve dyspnea during exercise in healthy man?

Nebulized fentanyl does not improve exercise capacity or dyspnoea in fibrosing interstitial lung disease

Exercise intolerance and exertional dyspnoea are hallmarks of fibrosing interstitial lung disease (FILD) and are associated with worse prognosis and quality of life. Activation of pulmonary vagal afferents influences the ventilatory pattern and contributes to the sensation of dyspnoea. We tested the hypothesis that nebulized fentanyl, which might attenuate aberrant pulmonary afferent activity in FILD, reduces ventilation and dyspnoea while extending exercise endurance time (EET). In this randomized, single-blind, placebo-controlled study, eight FILD patients (two males, 71 ± 6 years of age) performed incremental cardiopulmonary cycle exercise tests following nebulization of either fentanyl citrate (100 µg) or 0.9% saline. Previous work indicated that this dose was unlikely to produce central effects. Comparisons between treatment conditions at rest were undertaken using Student's paired t-test, and exercise data were evaluated with two-way ANOVA with repeated measures. Dyspnoea was assessed using the Borg dyspnoea scale. Resting respiratory variables were not different following treatment with fentanyl and saline; however, resting heart rate was lower following fentanyl (P = 0.002) and remained lower throughout exercise compared with placebo (P = 0.008). Fentanyl did not increase EET (placebo 334 ± 117 s vs. fentanyl 348 ± 126 s, P = 0.250) although overall minute ventilation was reduced slightly (mean difference: -0.97 L/min, P = 0.022). There were no differences in ratings of dyspnoea intensity or unpleasantness between the conditions either at rest or at end-exercise. Nebulized fentanyl did not improve EET or exercise dyspnoea but did decrease minute ventilation during exercise, although the extent of this reduction appears clinically insignificant. These findings suggest that nebulized fentanyl is unlikely to offer significant benefits for enhancing exercise capacity in FILD.

Physiological Factors Associated with Unsatisfied Inspiration at Peak Exercise in Healthy Adults

INTRODUCTION

Contrary to common belief, a growing body of evidence suggests that unsatisfied inspiration (UI), an inherently uncomfortable quality of dyspnea, is experienced by ostensibly healthy adults during high-intensity exercise. Based on our understanding of the mechanisms of UI among people with chronic respiratory conditions, this analysis tested the hypothesis that the experience of UI at peak exercise in young, healthy adults reflects the combination of high ventilatory demand and critical inspiratory constraints.

METHODS

In a retrospective analysis design, data included 321 healthy individuals (129 females) aged 25 ± 5 yr. Data were collected during one visit to the laboratory, which included anthropometrics, spirometry, and an incremental cardiopulmonary cycling test to exhaustion. Metabolic and cardiorespiratory variables were measured at peak exercise, and qualitative descriptors of dyspnea at peak exercise were assessed using a list of 15 descriptor phrases.

RESULTS

Thirty-four percent of participants ( n = 109) reported sensations of UI at peak exercise. Compared with the non-UI group, the UI group achieved a significantly higher peak work rate (243 ± 77 vs 235 ± 69 W, P = 0.016, d = 0.10), rate of O 2 consumption (3.32 ± 1.02 vs 3.27 ± 0.96 L·min -1 , P = 0.018, d = 0.05), minute ventilation (120 ± 38 vs 116 ± 35 L·min -1 , P = 0.047, d = 0.11), and breathing frequency (50 ± 9 vs 47 ± 9 breaths per minute, P = 0.014, d = 0.33), while having a lower exercise-induced change (peak-baseline) in inspiratory capacity (0.07 ± 0.41 vs 0.20 ± 0.49 L, P = 0.023, d = 0.29). The inspiratory reserve volume to minute ventilation ratio at peak exercise was also lower in the UI versus non-UI group. Dyspnea intensity and unpleasantness ratings were significantly higher in the UI versus non-UI group at peak exercise (both P < 0.001).

CONCLUSIONS

Healthy individuals reporting UI at peak exercise have relatively greater inspiratory constraints compared with those who do not select UI.

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.

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.

Prophylactic Fentanyl Sublingual Spray for Episodic Exertional Dyspnea in Cancer Patients: A Pilot Double-Blind Randomized Controlled Trial

CONTEXT

The optimal dose of fentanyl sublingual spray (FSS) for exertional dyspnea has not been determined.

OBJECTIVES

We examined the effect of two doses of prophylactic FSS on exertional dyspnea.

METHODS

In this parallel, dose-finding, double-blind randomized clinical trial, opioid-tolerant cancer patients completed a shuttle walk test at baseline. Patients completed a second shuttle walk test 10 minutes after a single dose of FSS equivalent to either 35%-45% (high dose) or 15%-25% (low dose) of the total daily opioid dose. The primary outcome was change in modified dyspnea Borg scale (0-10) between the first and second shuttle walk tests. Secondary outcomes included adverse events as well as changes in walk distance, vital signs, and neurocognitive function.

RESULTS

Thirty of the 50 enrolled patients completed the study. High-dose FSS (n = 13) resulted in significantly lower dyspnea (mean change -1.42; 95% CI -2.37, -0.48; P = 0.007) and greater walk distance (mean change 44 m; P = 0.001) compared to baseline. Low-dose FSS (n = 17) resulted in a nonsignificant reduction in dyspnea (mean change -0.47; 95% CI -1.26, 0.32; P = 0.24) and significant increase in walk distance (mean change 24 m; P = 0.01) compared to baseline. Global evaluation showed high-dose group was more likely to report at least somewhat better improvement (64% vs. 24%; P = 0.06). No significant adverse events or detriment to vital signs or neurocognitive function was detected.

CONCLUSION

Prophylactic FSS was well tolerated and demonstrated a dose-response relationship in improving both dyspnea and walk distance. High-dose FSS should be tested in confirmatory trials.

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.

Effect of Prophylactic Fentanyl Buccal Tablet on Episodic Exertional Dyspnea: A Pilot Double-Blind Randomized Controlled Trial

CONTEXT

Episodic dyspnea is one of the most common, debilitating, and difficult-to-treat symptoms.

OBJECTIVE

We conducted a pilot study to examine the effect of prophylactic fentanyl buccal tablet (FBT) on exercise-induced dyspnea.

METHODS

In this parallel, double-blind randomized placebo-controlled trial, opioid-tolerant patients were asked to complete a six-minute walk test (6MWT) at baseline and then a second 6MWT 30 minutes after a single dose of FBT (equivalent to 20-50% of their total opioid dose) or matching placebo. We compared dyspnea Numeric Rating Scale (NRS, 0-10, primary outcome), walk distance, vital signs, neurocognitive function, and adverse events between the two 6MWTs.

RESULTS

Among 22 patients enrolled, 20 (91%) completed the study. FBT was associated with a significant within-arm reduction in dyspnea NRS between 0 and six minutes (mean change -2.4, 95% CI -3.5, -1.3) and respiratory rate (mean change -2.6, 95% CI -4.7, -0.4). Placebo was also associated with a nonstatistically significant decrease in dyspnea (mean change -1.1). Between-arm comparison of dyspnea scores in the second 6MWT favored FBT, albeit not statistically significant (estimate -0.25, P = 0.068). Global impression revealed more patients in the FBT group than placebo group reporting their dyspnea was at least "somewhat better" in the second 6MWT (4 of 9 vs. 0 of 11, P = 0.03). The other secondary outcomes did not differ significantly between arms.

CONCLUSIONS

This study supports that prophylactic FBT was associated with a reduction of exertional dyspnea and was well tolerated. Our findings support the need for larger trials to confirm the therapeutic potential of rapid-onset opioids.

Exertional dyspnea associated with chest wall strapping is reduced when external dead space substitutes for part of the exercise stimulus to ventilation

Chest wall strapping has been used to assess mechanisms of dyspnea with restrictive lung disease. This study examined the hypothesis that dyspnea with restriction depends principally on the degree of reflex ventilatory stimulation. We compared dyspnea at the same (iso)ventilation when added dead space provided a component of the ventilatory stimulus during exercise. Eleven healthy men undertook a randomized controlled crossover trial that compared four constant work exercise conditions: 1) control (CTRL): unrestricted breathing at 90% gas exchange threshold (GET); 2) CTRL+dead space (DS): unrestricted breathing with 0.6-l dead space, at isoventilation to CTRL due to reduced exercise intensity; 3) CWS: chest wall strapping at 90% GET; and 4) CWS+DS: chest strapping with 0.6-l dead space, at isoventilation to CWS with reduced exercise intensity. Chest strapping reduced forced vital capacity by 30.4 ± 2.2% (mean ± SE). Dyspnea at isoventilation was unchanged with CTRL+DS compared with CTRL (1.93 ± 0.49 and 2.17 ± 0.43, 0–10 numeric rating scale, respectively; P = 0.244). Dyspnea was lower with CWS+DS compared with CWS (3.40 ± 0.52 and 4.51 ± 0.53, respectively; P = 0.003). Perceived leg fatigue was reduced with CTRL+DS compared with CTRL (2.36 ± 0.48 and 2.86 ± 0.59, respectively; P = 0.049) and lower with CWS+DS compared with CWS (1.86 ± 0.30 and 4.00 ± 0.79, respectively; P = 0.006). With unrestricted breathing, dead space did not change dyspnea at isoventilation, suggesting that dyspnea does not depend on the mode of reflex ventilatory stimulation in healthy individuals. With chest strapping, dead space presented a less potent stimulus to dyspnea, raising the possibility that leg muscle work contributes to dyspnea perception independent of the ventilatory stimulus.

NEW & NOTEWORTHY Chest wall strapping was applied to healthy humans to simulate restrictive lung disease. With chest wall strapping, dyspnea was reduced when dead space substituted for part of a constant exercise stimulus to ventilation. Dyspnea associated with chest wall strapping depended on the contribution of leg muscle work to ventilatory stimulation. Chest wall strapping might not be a clinically relevant model to determine whether an alternative reflex ventilatory stimulus mimics the intensity of exertional dyspnea.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 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, drug abuse and alcohol, 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.

EffenDys-Fentanyl Buccal Tablet for the Relief of Episodic Breathlessness in Patients With Advanced Cancer: A Multicenter, Open-Label, Randomized, Morphine-Controlled, Crossover, Phase II Trial

CONTEXT

Episodic breathlessness is a frequent and burdensome symptom in cancer patients but pharmacological treatment is limited.

OBJECTIVES

To determine time to onset, efficacy, feasibility, and safety of transmucosal fentanyl in comparison to immediate-release morphine for the relief of episodic breathlessness.

METHODS

Phase II, investigator-initiated, multicenter, open-label, randomized, morphine-controlled, crossover trial with open-label titration of fentanyl buccal tablet (FBT) in inpatients with incurable cancer. The primary outcome was time to onset of meaningful breathlessness relief. Secondary outcomes were efficacy (breathlessness intensity difference at 10 and 30 minutes; sum of breathlessness intensity difference at 15 and 60 minutes), feasibility, and safety. Study was approved by local ethics committees.

RESULTS

Twenty-five of 1341 patients were eligible, 10 patients agreed to participate (four female, mean age 58 ± 11, mean Karnofsky score 67 ± 11). Two patients died before final visits and two patients dropped-out because of disease progression leaving six patients for analysis with 61 episodes of breathlessness. Mean time to onset was for FBT 12.7 ± 10.0 and for immediate-release morphine 23.6 ± 15.1 minutes with a mean difference of -10.9 minutes (95% CI = -24.5 to 2.7, P = 0.094). Efficacy measures were predominately in favor for FBT. Both interventions were safe. Feasibility failed because of too much study demands for a very ill patient group.

CONCLUSION

The description of a faster and greater relief of episodic breathlessness by transmucosal fentanyl versus morphine justifies further evaluation by a full-powered trial.

Impact of Prophylactic Fentanyl Pectin Nasal Spray on Exercise-Induced Episodic Dyspnea in Cancer Patients: A Double-Blind, Randomized Controlled Trial

CONTEXT

Episodic breathlessness is common and debilitating in cancer patients.

OBJECTIVES

In this pilot study, we examined the effect of prophylactic fentanyl pectin nasal spray (FPNS) on exercise-induced dyspnea, physiologic function, and adverse events.

METHODS

In this parallel, double-blind randomized placebo-controlled trial, opioid-tolerant patients performed three six-minute walk tests (6MWTs) to induce dyspnea. They were randomized to receive either FPNS (15%-25% of total daily opioid dose each time) or placebo 20 minutes before the second and third 6MWTs. We compared dyspnea Numeric Rating Scale (NRS, 0-10, primary outcome), walk distance, vital signs, neurocognitive function, and adverse events between the first and second 6MWTs (T2-T1) and between the first and third 6MWTs (T3-T1).

RESULTS

Twenty-four patients enrolled, with 96% completion. FPNS was associated with significant within-arm reduction in dyspnea NRS at rest (T2-T1: -0.9 [95% CI -1.7, -0.1]; T3-T1: -1.3 [95% CI -2.0, -0.5]) and at the end of a 6MWT (T2-T1: -2.0 [95% CI -3.5, -0.6]; T3-T1: -2.3 [95% CI -4.0, -0.7]), and longer walk distance (T2-T1 +23.8 m [95% CI +1.3, +46.2 m]; T3-T1: +23.3 m [95% CI -1.7, +48.2]). In the placebo arm, we observed no significant change in walk distance nor dyspnea NRS at rest, but significant reduction in dyspnea NRS at six minutes (T2-T1: -1.7 [95% CI -3.3, -0.1]; T3-T1: -2.5 [95% CI -4.2, -0.9]). Vital signs, neurocognitive function, and adverse effects did not differ significantly.

CONCLUSION

FPNS was safe, reduced dyspnea at rest, and increased walk distance in before-after comparison. The placebo effect was substantial, which needs to be factored in future study designs.

TRIAL REGISTRATION

ClinicalTrials.govNCT01832402.