Methods to assess breathlessness in healthy subjects: a critical evaluation and application to analyse the acute effects of diazepam and promethazine on breathlessness induced by exercise or by exposure to raised levels of carbon dioxide

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.

Benzodiazepines for the relief of breathlessness in advanced malignant and non-malignant diseases in adults

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 1, 2010, on 'Benzodiazepines for the relief of breathlessness in advanced malignant and non-malignant diseases in adults'. Breathlessness is one of the most common symptoms experienced in the advanced stages of malignant and non-malignant disease. Benzodiazepines are widely used for the relief of breathlessness in advanced diseases and are regularly recommended in the literature. At the time of the previously published Cochrane review, there was no evidence for a beneficial effect of benzodiazepines for the relief of breathlessness in people with advanced cancer and chronic obstructive pulmonary disease (COPD).

OBJECTIVES

The primary objective of this review was to determine the efficacy of benzodiazepines for the relief of breathlessness in people with advanced disease. Secondary objectives were to determine the efficacy of different benzodiazepines, different doses of benzodiazepines, different routes of application, adverse effects of benzodiazepines, and the efficacy in different disease groups.

SEARCH METHODS

This is an update of a review published in 2010. We searched 14 electronic databases up to September 2009 for the original review. We checked the reference lists of all relevant studies, key textbooks, reviews, and websites. For the update, we searched CENTRAL, MEDLINE, and EMBASE and registers of clinical trials for further ongoing or unpublished studies, up to August 2016. We contacted study investigators and experts in the field of palliative care asking for further studies, unpublished data, or study details when necessary.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and controlled clinical trials (CCTs) assessing the effect of benzodiazepines compared with placebo or active control in relieving breathlessness in people with advanced stages of cancer, chronic obstructive pulmonary disease (COPD), chronic heart failure (CHF), motor neurone disease (MND), and idiopathic pulmonary fibrosis (IPF).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed identified titles and abstracts. Three review authors independently performed assessment of all potentially relevant studies (full text), data extraction, and assessment of methodological quality. We carried out meta-analysis where appropriate.

MAIN RESULTS

Overall, we identified eight studies for inclusion: seven in the previous review and an additional study for this update. We also identified two studies awaiting classification in this update. The studies were small (a maximum number of 101 participants) and comprised data from a total of 214 participants with advanced cancer or COPD, which we analysed. There was only one study of low risk of bias. Most of the studies had an unclear risk of bias due to lack of information on random sequence generation, concealment, and attrition. Analysis of all studies did not show a beneficial effect of benzodiazepines for the relief of breathlessness (the primary outcome) in people with advanced cancer and COPD (8 studies, 214 participants) compared to placebo, midazolam, morphine, or promethazine. Furthermore, we observed no statistically significant effect in the prevention of episodic breathlessness (breakthrough dyspnoea) in people with cancer (after 48 hours: risk ratio of 0.76 (95% CI 0.53 to 1.09; 2 studies, 108 participants)) compared to morphine. Sensitivity analyses demonstrated no statistically significant differences regarding type of benzodiazepine, dose, route and frequency of delivery, duration of treatment, or type of control. Benzodiazepines caused statistically significantly more adverse events, particularly drowsiness and somnolence, when compared to placebo (risk difference 0.74 (95% CI 0.37, 1.11); 3 studies, 38 participants). In contrast, two studies reported that morphine caused more adverse events than midazolam (RD -0.18 (95% CI -0.31, -0.04); 194 participants).

AUTHORS' CONCLUSIONS

Since the last version of this review, we have identified one new study for inclusion, but the conclusions remain unchanged. There is no evidence for or against benzodiazepines for the relief of breathlessness in people with advanced cancer and COPD. Benzodiazepines caused more drowsiness as an adverse effect compared to placebo, but less compared to morphine. Benzodiazepines may be considered as a second- or third-line treatment, when opioids and non-pharmacological measures have failed to control breathlessness. There is a need for well-conducted and adequately powered studies.

Time to Loss of Consciousness and Its Relation to Behavior in Slaughter Pigs during Stunning with 80 or 95% Carbon Dioxide

Exposure to CO₂ at high concentration is a much debated stunning method in pigs. Pigs respond aversively to high concentrations of CO₂, and there is uncertainty about what behaviors occur before and after loss of consciousness. The aim was to assess timing of unconsciousness in pigs during exposure to high concentrations of CO₂ based on changes in electroencephalogram (EEG) activity and the relation with the behaviors sniffing, retreat and escape attempts, lateral head movements, jumping, muscular contractions, loss of posture, and gasping. Pigs (108 ± 9 kg) were randomly assigned to 80% CO₂ (80C, n = 24) or 95% CO₂ (95C, n = 24). The time at which the gondola started descending into the well pre-filled with 80C or 95C was marked as T = 0. The CO₂ exposure lasted 346 s after which the corneal reflex and breathing were assessed for 1 min. Visual assessment of changes in the amplitude and frequency of EEG traces after T = 0 was used to determine loss of consciousness. Time to loss of consciousness was longer in 80C pigs (47 ± 6 s) than in 95C pigs (33 ± 7 s). Time to an iso-electric EEG was similar in 80C pigs (75 ± 23 s) and 95C pigs (64 ± 32 s). When pigs descended into the well, the earlier entry of 95C pigs into high CO₂ atmosphere rather than the concentration of CO₂ by itself affected the latency of behavioral responses and decreasing brain activity. During exposure to the gas, 80C and 95C pigs exhibited sniffing, retreat attempts, lateral head movements, jumping, and gasping before loss of consciousness. 95C pigs exhibited all these behaviors on average earlier than 80C pigs after T = 0. But the interval between onset of these behaviors and loss of consciousness and the duration of these behaviors, except gasping, was similar for both treatments. Loss of posture was on average observed in both groups 10 s before EEG-based loss of consciousness. Furthermore, 88% of 80C pigs and 94% of 95C pigs demonstrated muscular contractions before loss of consciousness. The findings provide little reason to conclude on a behavioral basis that these atmospheres are greatly different in their impact on pig welfare.

Repeatability of the evaluation of perception of dyspnea in normal subjects assessed through inspiratory resistive loads

Purpose:

Study the repeatability of the evaluation of the perception of dyspnea using an inspiratory resistive loading system in healthy subjects.

Methods:

We designed a cross sectional study conducted in individuals aged 18 years and older. Perception of dyspnea was assessed using an inspiratory resistive load system. Dyspnea was assessed during ventilation at rest and at increasing resistive loads (0.6, 6.7, 15, 25, 46.7, 67, 78 and returning to 0.6 cm H2O/L/s). After breathing in at each level of resistive load for two minutes, the subject rated the dyspnea using the Borg scale. Subjects were tested twice (intervals from 2 to 7 days).

Results:

Testing included 16 Caucasian individuals (8 male and 8 female, mean age: 36 years). The median scores for dyspnea rating in the first test were 0 at resting ventilation and 0, 2, 3, 4, 5, 7, 7 and 1 point, respectively, with increasing loads. The median scores in the second test were 0 at resting and 0, 0, 2, 2, 3, 4, 4 and 0.5 points, respectively. The intra-class correlation coefficient was 0.57, 0.80, 0.74, 0.80, 0.83, 0.86, 0.91, and 0.92 for each resistive load, respectively. In a generalized linear model analysis, there was a statistically significant difference between the levels of resistive loads (p<0.001) and between tests (p=0.003). Dyspnea scores were significantly lower in the second test.

Conclusion:

The agreement between the two tests of the perception of dyspnea was only moderate and dyspnea scores were lower in the second test. These findings suggest a learning effect or an effect that could be at least partly attributed to desensitization of dyspnea sensation in the brain.

WITHDRAWN: Opioids for the palliation of breathlessness in advanced disease and terminal illness

BACKGROUND

Breathlessness is a common symptom in people with advanced disease. The most effective treatments are aimed at treating the underlying cause of the breathlessness but this may not be possible and symptomatic treatment is often necessary. Strategies for the symptomatic treatment of breathlessness have never been systematically evaluated. Opioids are commonly used to treat breathlessness: the mechanisms underlying their effectiveness are not completely clear and there have been few good-sized trials in this area.

OBJECTIVES

To determine the effectiveness of opioid drugs given by any route in relieving the symptom of breathlessness in patients who are being treated palliatively.

SEARCH METHODS

An electronic search was carried out of Medline, Embase, CINAHL, T he Cochrane L ibrary, Dissertation Abstracts, Cancercd and SIGLE. Review articles and reference lists of retrieved articles were hand searched. Date of most recent search: May 1999.

SELECTION CRITERIA

Randomised double-blind, controlled trials comparing the use of any opioid drug against placebo for the relief of breathlessness were included. Patients with any illness suffering from breathlessness were included and the intervention was any opioid, given by any route, in any dose.

DATA COLLECTION AND ANALYSIS

Studies identified by the search were imported into a reference manager database. The full texts of the relevant studies were retrieved and data were independently extracted by two review authors. Studies were quality scored according to the Oxford Quality scale. The primary outcome measure used was breathlessness and the secondary outcome measure was exercise tolerance. Studies were divided into non-nebulised and nebulised and were analysed both separately and together. A qualitative analysis was carried out of adverse effects of opioids. Where appropriate, meta-analysis was carried out.

MAIN RESULTS

Eighteen studies were identified of which nine involved the non-nebulised route of administration and nine the nebulised route. A small but statistically significant positive effect of opioids was seen on breathlessness in the analysis of studies using non-nebulised opioids. There was no statistically significant positive effect seen for exercise tolerance in either group of studies or for breathlessness in the studies using nebulised opioids.

AUTHORS' CONCLUSIONS

There is evidence to support the use of oral or parenteral opioids to palliate breathlessness although numbers of patients involved in the studies were small. No evidence was found to support the use of nebulised opioids. Further research with larger numbers of patients, using standardised protocols and with quality of life measures is needed.

A simple, cost-effective and flexible method for processing of snap-frozen tissue to prepare large amounts of intact RNA using laser microdissection

Understanding the molecular basis of disease requires gene expression profiling of normal and pathological tissue. Although the advent of laser microdissection (LMD) has greatly facilitated the procurement of specific cell populations, often only small amounts of low quality RNA is recovered. This precludes the use of global approaches of gene expression profiling which require sizable amounts of high quality RNA. Here we report a method for processing of snap-frozen tissue to prepare large amounts of intact RNA using LMD. Portions of small intestine from piglets (n = 6) were snap-frozen in Optimum Cutting Temperature compound (experimental) and in RNAlater (control). A randomly selected sample was laser microdissected using the developed protocol in multiple sessions totalling 4 h each day on four consecutive days. RNAs were extracted from these samples and its control and their quality (RIN) determined. RINs of the experimental samples were independent of time (p = 0.12) and day (p = 0.56) of the microdissection thereby suggesting that their RNA quality remained unaltered. These samples exhibited high quality (RIN ≥ 8) with good recovery (81.2%) and excellent yield (1539 ng/1.2 × 10(7) μm(2)). Their overall RIN, 8.029 ± 0.116, was not significantly different from 8.2 (p = 0.123), the value obtained from the control, non-laser microdissected, sample. This indicated that the RNA quality from the laser microdissected and non-microdissected samples was comparable. The method allowed LMD for up to 4 h each day for a total of four days. The microdissected samples can be pooled thereby increasing amount of RNA at least by ten-fold. The procedure did not require any expensive limited-shelf life RNase inhibitors, RNA protectors, staining kits or toxic chemicals. Furthermore, it was flexible and enabled the processing without affecting routine laboratory workflow. The method developed was simple, inexpensive and provided substantial amounts of high quality RNA suitable for gene expression profiling and other cellular and molecular analyses for biology and molecular medicine.

Palliative care concepts in respiratory disease

Many respiratory diseases besides lung cancer are still not curable. There is an unmet need for palliative care, especially in non-malignant conditions. In this article we focus on symptomatic treatment of typical symptoms in respiratory disease beyond causal treatment.

The impact of human pregnancy on perceptual responses to chemoreflex vs. exercise stimulation of ventilation: a retrospective analysis

We examined the impact of human pregnancy on breathlessness intensity at matched levels of ventilation (V˙E) during isoxic hyperoxic CO₂ rebreathing and incremental cycle exercise tests in 21 healthy women in the third trimester (TM₃) and again ∼5 months post-partum (PP). Pregnancy had no significant (P > 0.05) effect on the slope or threshold of the breathlessness intensity-V˙E relationship during both exercise and rebreathing. By contrast, the slope of the breathlessness intensity-V˙E relationship was significantly higher, while the threshold of this relationship was consistently lower during rebreathing vs. exercise (both P < 0.05), regardless of pregnancy status (P > 0.05). As a result, breathlessness intensity was markedly higher at any given V˙E (e.g., by ∼4 Borg units at 40 L/min) during rebreathing vs. exercise, regardless of pregnancy status. Inter-subject variation in breathlessness intensity-V˙E slopes during exercise was not associated with inter-subject variation in breathlessness intensity-V˙E slopes during rebreathing or with increased central chemoreflex responsiveness during pregnancy (both P > 0.05). In conclusion, the intensity of perceived breathlessness for a given V˙E depends, at least in part, on the nature and source of increased central respiratory motor command output, independent of pregnancy status; and pregnancy-induced increases in activity-related breathlessness cannot be easily explained by increased central chemoreflex responsiveness.

Benzodiazepines for the relief of breathlessness in advanced malignant and non-malignant diseases in adults

BACKGROUND

Breathlessness is one of the most common symptoms experienced in the advanced stages of malignant and non-malignant disease. Benzodiazepines are widely used for the relief of breathlessness in advanced diseases and are regularly recommended in the literature. However, the evidence for their use for this symptom is unclear.

OBJECTIVES

To determine the efficacy of benzodiazepines for the relief of breathlessness in patients with advanced disease.

SEARCH STRATEGY

We searched 14 electronic databases up to September 2009. We checked the reference lists of all relevant studies, key textbooks, reviews, and websites. We contacted investigators and specialists in palliative care for unpublished data.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and controlled clinical trials (CCTs) assessing the effect of benzodiazepines in relieving breathlessness in patients with advanced stages of cancer, chronic obstructive pulmonary disease (COPD), chronic heart failure (CHF), motor neurone disease (MND), and idiopathic pulmonary fibrosis (IPF).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed identified titles and abstracts. Three independent review authors performed assessment of all potentially relevant studies (full text), data extraction, and assessment of methodological quality. We carried out meta-analysis where appropriate.

MAIN RESULTS

Seven studies were identified, including 200 analysed participants with advanced cancer and COPD. Analysis of all seven studies (including a meta-analysis of six out of seven studies) did not show a beneficial effect of benzodiazepines for the relief of breathlessness in patients with advanced cancer and COPD. Furthermore, no significant effect could be observed in the prevention of breakthrough dyspnoea in cancer patients. Sensitivity analysis demonstrated no significant differences regarding type of benzodiazepine, dose, route and frequency of delivery, duration of treatment, or type of control.

AUTHORS' CONCLUSIONS

There is no evidence for a beneficial effect of benzodiazepines for the relief of breathlessness in patients with advanced cancer and COPD. There is a slight but non-significant trend towards a beneficial effect but the overall effect size is small. Benzodiazepines caused more drowsiness as an adverse effect compared to placebo, but less compared to morphine. These results justify considering benzodiazepines as a second or third-line treatment within an individual therapeutic trial, when opioids and non-pharmacological measures have failed to control breathlessness. Although a few good quality studies were included in this review, there is still a further need for well-conducted and adequately powered studies.

Comprehensive Symptom Management in Patients with Advanced-Stage Non–Small-Cell Lung Cancer

Although we have made steady improvements in the survival rates of patients with advanced-stage lung cancer, the majority of patients still experience distress and suffering. Although the symptom burden is greatest in patients in the end stages of life, many patients living with lung cancer suffer from troubling symptoms and side effects of therapy. Even long-term survivors with early-stage non-small-cell lung cancer (NSCLC) often experience respiratory symptoms, such as dyspnea and cough. Because of the high prevalence of NSCLC and the frequency with which it presents in an incurable stage, symptom management is a large component of the care of these patients. Dyspnea, cough, fatigue, anorexia/cachexia, and pain are the most common symptoms in patients with advanced-stage NSCLC. Cancer-directed therapy can improve some of these symptoms but often incompletely and temporarily. Therefore, comprehensive care of patients with advanced-stage NSCLC must include therapies targeted at these difficult and distressing symptoms.

Management of dyspnea

Patients with cancer frequently report dyspnea, the uncomfortable awareness of breathing. Lung involvement with cancer does not predict its occurrence. Patients describe it as one of the most frightening and distressing symptoms, and patient self-report is the only reliable measure. Measurements of respiratory rate, oxygen saturation, and arterial blood gases do not measure dyspnea. Opioids in modest doses have been demonstrated to give effective relief of dyspnea, whether or not identifiable reversible causes exist. Medical management of dyspnea can be directed at the underlying cause when the potential benefits outweigh the burdens of such treatment. In rare cases where symptomatic treatment is unable to control dyspnea to the patient's satisfaction, sedation is an effective, ethical option.

Clinical management of dyspnoea

Dyspnoea, defined as a sensation of an uncomfortable awareness of breathing, is one of the most frightening and distressing symptoms for patients with cancer. It is very common in cancer patients with and without direct lung involvement. The gold standard of diagnosis and assessment is the patient's self-report. Measurements of respiratory rate, oxygen saturation, and arterial blood gases do not measure dyspnoea. Fast, safe, and effective relief of the symptom is possible whether or not identifiable reversible causes exist. Opioids are the first line of therapy for such relief. Medical management can be directed at the underlying cause when the potential benefits outweigh the burdens of such treatment. In rare cases for which symptomatic treatment does not control dyspnoea to the patient's satisfaction, sedation is an effective, ethical option.

Opioids for the palliation of breathlessness in terminal illness

BACKGROUND

Breathlessness is a common symptom in people with advanced disease. The most effective treatments are aimed at treating the underlying cause of the breathlessness but this may not be possible and symptomatic treatment is often necessary. Strategies for the symptomatic treatment of breathlessness have never been systematically evaluated. Opioids are commonly used to treat breathlessness: the mechanisms underlying their effectiveness are not completely clear and there have been few good-sized trials in this area.

OBJECTIVES

To determine the effectiveness of opioid drugs given by any route in relieving the symptom of breathlessness in patients who are being treated palliatively.

SEARCH STRATEGY

An electronic search was carried out of Medline, Embase, Cinahl, the Cochrane library, Dissertation Abstracts, Cancercd and SIGLE. Review articles and reference lists of retrieved articles were hand searched. Date of most recent search: May 1999

SELECTION CRITERIA

Randomised double-blind, controlled trials comparing the use of any opioid drug against placebo for the relief of breathlessness were included. Patients with any illness suffering from breathlessness were included and the intervention was any opioid, given by any route, in any dose.

DATA COLLECTION AND ANALYSIS

Studies identified by the search were imported into a reference manager database. The full texts of the relevant studies were retrieved and data were independently extracted by two reviewers. Studies were quality scored according to the Jadad scale. The primary outcome measure used was breathlessness and the secondary outcome measure was exercise tolerance. Studies were divided into non-nebulised and nebulised and were analysed both separately and together. A qualitative analysis was carried out of adverse effects of opioids. Where appropriate, meta-analysis was carried out.

MAIN RESULTS

Eighteen studies were identified of which nine involved the non-nebulised route of administration and nine the nebulised route. A small but statistically significant positive effect of opioids was seen on breathlessness in the analysis of studies using non-nebulised opioids. There was no statistically significant positive effect seen for exercise tolerance in either group of studies or for breathlessness in the studies using nebulised opioids.

REVIEWER'S CONCLUSIONS

There is evidence to support the use of oral or parenteral opioids to palliate breathlessness although numbers of patients involved in the studies were small. No evidence was found to support the use of nebulised opioids. Further research with larger numbers of patients, using standardised protocols and with quality of life measures is needed.

A comparison of the reproducibility and the sensitivity to change of visual analogue scales, Borg scales, and Likert scales in normal subjects during submaximal exercise

OBJECTIVE

To assess which subjective scale, the visual analogue scale (VAS), the Borg CR10 (Borg) scale, or the Likert scale (LS), if any, is decidedly more reproducible and sensitive to change in the assessment of symptoms.

DESIGN

Prospective clinical study.

SETTING

Exercise laboratory.

PARTICIPANTS

Twenty-three physically active male subjects (mean +/- SD age of 30 +/- 4 years old) were recruited.

INTERVENTION

Each subject attended the exercise laboratory on four occasions at intervals of 1 week. Three subjective scales were used: (1) the VAS (continuous scale); (2) the Borg scale (12 fixed points); and (3) the Likert scale (LS; 5 fixed points). Four identical submaximal tests were given (2 min at 60% maximum oxygen uptake [VO(2)max] and 6 min at 70% VO(2)max). Two tests were undertaken to assess the reproducibility of scores that were obtained with each subjective scale. Two other tests were undertaken to assess the sensitivity of each scale to a change in symptom perception: a double-blind treatment with propranolol, 80 mg, (ie, active therapy; to increase the sensation of breathlessness and general fatigue during exercise) or matching placebo. The subjective scale scores were measured at 1 min 30 s, 5 min 30 s, and 7 min 15 s of exercise. Reproducibility was defined as the proportion of total variance (ie, between-subject plus within-subject variance) explained by the between-subject variance given as a percentage. Sensitivity was defined as the effect of the active drug therapy over the variation within subjects.

RESULTS

Overall, the VAS performed best in terms of reproducibility for breathlessness and general fatigue, with reproducibility coefficients as high as 78%. For sensitivity, the VAS was best for breathlessness (ratio, 2.7) and the Borg scale was most sensitive for general fatigue (ratio, 3.0). The relationships between the respective psychological and physiologic variables were reasonably stable throughout the testing procedure, with overall typical correlations of 0.73 to 0.82

CONCLUSION

This study suggests that subjective scales can reproducibly measure symptoms during steady-state exercise and can detect the effect of a drug intervention. The VAS and Borg scales appear to be the best subjective scales for this purpose.

Ventilatory drive at rest and perception of exertional dyspnea in severe COPD

BACKGROUND

The reasons for exertional dyspnea in severe COPD are not well established, but they are not solely related to the mechanical load. We tested the hypothesis that breathlessness may be determined, in part, by the response of an individual's central output.

METHODS

In 26 patients with severe COPD (FEV1 < 50% predicted) and 22 matched control subjects, we assessed at rest the ventilatory and mouth occlusion pressure (P0.1) response to hyperoxic progressive hypercapnia. At rest and during a symptom-limited exercise test, routine cardiopulmonary variables were measured, and respiratory muscle function was evaluated using esophageal and gastric pressure. Dyspnea was assessed with a visual analog scale.

RESULTS

Dyspnea with or without leg discomfort limited exercise in 73% of patients. Peak exercise dyspnea correlated only with dyspnea at rest (r = 0.5, p < 0.008) and P0.1 response to CO2 (deltaP0.1/delta[end-tidal PCO2]PETCO2) (r = 0.48, p = 0.02). Multiple regression analysis including resting and exercise data as independent variables revealed that 47% of the variance for dyspnea at peak exercise was explained by a model including dyspnea at rest and deltaP0.1/deltaPETCO2. Again, deltaP0.1/deltaPETCO2 was the only predictor for the change in dyspnea from rest to peak exercise (delta Dyspnea, r2 = 0.28, p = 0.005). There was no correlation between exercise dyspnea and any metabolic variable, pulmonary function, or respiratory muscle function test.

CONCLUSION

In severe COPD, exertional dyspnea is not simply related to respiratory muscle load or mechanical impairment, but also to an individual's central motoneural output to the respiratory system.

Respiratory sensations during heavy exercise in subjects without respiratory chemosensitivity

Breathlessness arises from increased medullary respiratory center activity projecting to the forebrain (respiratory corollary discharge hypothesis). Subjects with congenital central hypoventilation syndrome (CCHS) lack the normal hyperpnea and breathlessness during hypercapnia. The corollary discharge hypothesis predicts that if CCHS subjects have normal hyperpnea during exercise, they will experience normal breathlessness during exercise. To test this, we studied four CCHS subjects and six matched controls during an exhausting constant-load cycling test requiring substantial anaerobiosis. CCHS subjects rated significantly less breathlessness at the end of the test than controls, but ventilation (index of respiratory corollary discharge) was also somewhat lower in CCHS (not significant). In both groups, breathlessness increased disproportionately more than ventilation towards the end of exercise. These data failed to disprove the corollary discharge hypothesis of breathlessness, but do suggest that the relationship between ventilation and breathlessness is non-linear and/or that projections of chemoreceptor afferents to the forebrain (presumed lacking in CCHS) is one source of breathlessness in normals.

The reproducibility of symptoms during a submaximal exercise test in chronic heart failure

AIMS

The aim of this study was to evaluate the use of a submaximal test with a symptom limited endpoint and to measure the reproducibility of symptoms in patients with CHF.

METHODS

Ten patients with chronic heart failure were studied. Based on two maximal treadmill tests an individual protocol using a constant work rate at a submaximal intensity was derived. The projected maximum treadmill time for the constant workrate was between 8 and 17 min. Tests were carried out 1, 2, 4 and 6 weeks after the maximum tests. Every 2.5 min during the submaximal test patients recorded their symptoms of breathlessness and fatigue using computer automated visual analogue (VAS) and Borg CR10 scales. The measure of reproducibility used was the proportion of total variability explained by the between subject variability.

RESULTS

Using the VAS scale, general fatigue was reasonably reproducible ranging from 77-86%. For VAS breathlessness reproducibility ranged from 66% to 83%. Reproducibility for breathlessness and fatigue for the Borg CR10 scale was much lower than the VAS scale. Reproducibility for the treadmill times was 51% but increased to 76% if one test of one subject was excluded.

CONCLUSIONS

The use of the VAS during submaximal exercise offers a useful means of evaluating symptoms in CHF and potentially their response to treatment. These findings show that individual submaximal protocols can be easily prescribed for CHF patients. Using such an approach, clinically desirable tests lasting around 12 min can be developed. These tests are reasonably reproducible and may provide a useful means of assessing patient disability and the impact of treatment.

Welfare implications of gas stunning pigs: 3. The time to loss of somatosensory evoked potentials and spontaneous electrocorticogram of pigs during exposure to gases

Changes in the spontaneous electrocorticogram (ECoG) and somatosensory evoked potentials (SEPs) were recorded in 12 pigs in each of three gas killing treatments. The treatments were 90% argon in air with 2% residual oxygen; a mixture of 30% carbon dioxide and 60% argon in air with 2% residual oxygen; or 80-90% carbon dioxide in air. The mean times to loss of SEPs were 15, 17 and 21 s, respectively. The mean time to loss of SEPs recorded during killing with a high concentration of carbon dioxide was significantly longer than those recorded for the other two gas killing treatments (P < 0.05). Slow waves (high amplitude and low frequency) appeared on average 15 s after exposure to argon. In some pigs killed with the carbon dioxide-argon mixture, a decrease in the frequency of electrical activity was apparent, although slow waves did not appear during killing with a higher concentration of carbon dioxide. A suppressed ECoG (reduction in amplitude of signals) was recorded at 22 and 20 s respectively, during exposure to the carbon dioxide-argon mixture and 80-90% carbon dioxide in air, but the onset of ECoG suppression could not be determined exactly during exposure to 90% argon in air. The time to onset of an isoelectric ECoG was 54, 39d and 32 s after exposure to argon, carbon dioxide-argon mixture and a high concentration of carbon dioxide, respectively. The mean time to the onset of an isoelectric ECoG during exposure to argon was significantly longer than that recorded for the other two gas killing treatments (P < 0.05). Based on the time to loss of SEPs, it is concluded that during killing with a high concentration of carbon dioxide, pigs would have to endure a moderate to severe respiratory distress induced with this gas for a considerable period of time prior to the loss of brain responsiveness. Argon-induced anoxia appears to be the first choice from a welfare point of view for killing pigs, based on its lack of aversive properties and its effectiveness in rapidly abolishing brain responsiveness. A mixture of 30% carbon dioxide and 60% argon in air is considered to be more humane than using a high concentration of carbon dioxide, as the time to loss of brain responsiveness is similar to that using 90% argon in air.

Dyspnea: pathophysiology and assessment

Dyspnea is frequently a multicausal and devastating symptom among advanced cancer patients. It occurs in 21%-78.6% of patients days or weeks before death and is often difficult to control. The genesis and pathophysiology of dyspnea as a symptom still has not been well understood. Dyspnea is frequently associated with abnormalities in the mechanisms that regulate normal breathing; however, the actual expression of dyspnea by a patient results from a complex interaction between the abnormalities in breathing and the perception of those abnormalities in the central nervous system. The production of dyspnea has to be related to the activation of mechanoreceptors both in the respiratory muscles and in the lung, even in the absence of increased muscle respiratory activity. Respiratory muscle weakness appears to be an important cause of dyspnea in malnourished, asthenic, and cachectic cancer patients. This might also explain why about 24% of dyspneic cancer patients do not present cardiac/pulmonary disease. In addition, two other possible mechanisms of dyspnea have been proposed: chemoreceptor stimulation and efferent activity from the respiratory center by direct ascending stimulation. These factors and the assessment tools used in patients with chronic dyspnea are summarized in this review.

Individual differences in breathlessness during exercise, as related to ventilatory chemosensitivities in humans

1. The present study attempted to test the hypothesis that breathlessness associated with exercise hyperpnoea is greater in subjects with greater activities of the central and peripheral chemoreceptors during exercise. The chemoreceptor activities were assessed by resting estimates of hypercapnic ventilatory response (delta VE/delta PCO2, HCVR) and hypoxic ventilatory response (delta VE/-delta SO2, HVR), respectively, where VE is minute ventilation and SO2 is oxygen saturation. 2. Nine female and nine male subjects performed a 1 min incremental exercise test until exhaustion, during which breathlessness intensity (BS), assessed by a Borg category scale, and VE were measured every minute. The maximum O2 uptake (VO2,max) was also determined. 3. Using a stepwise multiple linear regression analysis, the relative contributions of not only VE, HCVR and HVR, but also VO2,max and a predicted maximum voluntary ventilation (MVVp) of the individuals to BS, were examined. 4. The analysis showed that BS = 0.1VE + 4.9HVR - 0.03MVVp + 0.55 (r2 = 0.71), indicating that VE accounted for 44% of the variance of BS, HVR for 12% and MVVp for 15%. No significant relation of HCVR and VO2,max to BS was found. 5. These results suggest a contribution of peripheral chemoreceptors to the generation of exertional breathlessness.

Exercise training decreases dyspnea and the distress and anxiety associated with it. Monitoring alone may be as effective as coaching

STUDY OBJECTIVE

To determine whether exercise training with coaching is more effective than exercise training alone in reducing dyspnea and the anxiety and distress associated with it and improving exercise performance, self-efficacy for walking, and dyspnea with activities of daily living.

DESIGN

Randomized clinical trial of 51 dyspnea-limited patients with COPD assigned to monitored (n = 27) or coached (n = 24) exercise groups.

SETTING

Outpatient area of university teaching hospital.

INTERVENTION

Both groups completed 12 supervised treadmill training sessions (phase 1) over 4 weeks followed by 8 weeks of home walking (phase 2). The CE group also received coaching during training.

MEASUREMENTS

Perceived work of breathing, dyspnea intensity, distress associated with dyspnea, and anxiety associated with dyspnea were rated on a visual analog scale during incremental treadmill testing and after 6-min walks before and after phase 1. Dyspnea with activities of daily living, self-efficacy for walking, state anxiety, and 6-min walks were measured before and after both phases.

RESULTS

Dyspnea and the associated distress and anxiety improved significantly for both groups relative to work performed and in relation to ventilation (p < 0.05). There were no significant differences between groups in any outcomes. The phase 1 improvement in laboratory dyspnea was accompanied by improvements in dyspnea with activities of daily living (p < 0.01) and self-efficacy for home walking (p < 0.01) that were sustained during the home phase.

CONCLUSIONS

Coaching with exercise training was no more effective than exercise training alone in improving exercise performance, dyspnea, and the anxiety and distress associated with it, dyspnea with activities, and self-efficacy for walking.

Effect of inhaled morphine on the development of breathlessness during exercise in patients with chronic lung disease

BACKGROUND

Inhaled morphine has previously been shown to increase exercise endurance in patients with chronic lung disease. A similar study was performed to determine whether inhaled morphine reduces the sensation of breathlessness in this group of patients.

METHODS

A randomised double blind study on the effect of nebulised morphine on both exercise induced breathlessness and maximum achievable power output using isotonic saline as a control was performed in 10 patients with stable chronic lung disease. Each subject performed a progressive exercise test (Jones' stage I) on an electrically braked cycle ergometer. The work load was increased by 10 watts per minute and subjects exercised to exhaustion. At the end of each minute of exercise patients were asked to rate their degree of breathlessness according to a modified Borg scale. All subjects were randomised to receive either inhaled morphine sulphate 1 mg/ml (5 ml) or isotonic saline (5 ml) by wet nebulisation. The effect of morphine and saline on the achieved exercise capacity and the development of breathlessness during exercise was tested on separate days.

RESULTS

The mean dose of morphine inhaled was 1.24 mg. There was no difference in maximum power output achieved, minute ventilation at maximum power output, nor the degree of breathlessness at maximum power output between the groups treated with morphine and placebo. The degree of breathlessness was related to the power output achieved during exercise by a power function relationship (mean r: morphine = 0.86, saline = 0.87). However, there was a wide variation in the sensation for any given power output in both groups. There was no difference in the group mean slopes (morphine = 1.15, saline = 1.00) or intercepts (morphine = 0.07, saline = 0.15) in this relationship between the morphine and saline treatment groups.

CONCLUSIONS

In patients with severe chronic lung disease inhaled morphine in the doses used in this study does not relieve exercise induced breathlessness nor does it increase maximum power output achieved during progressive exercise.

Effect of 30 mg of morphine alone or with promethazine or prochlorperazine on the exercise capacity of patients with COPD

OBJECTIVE

We have shown that the administration of 0.8 mg/kg of morphine (M) to patients with COPD resulted in a 20% increase in the maximum oxygen consumption (Vo2max), but was associated with significant drowsiness and euphoria. The objective of the present study was to ascertain whether lower doses of M alone or in combination with prochlorperazine (PC) or promethazine (P) could elicit significant increases in exercise tolerance.

DESIGN

The exercise capacity, psychological status, and reaction times were assessed before and 60 min after the patients received placebo (PLAC), 30 mg M orally, 30 mg M plus 10 mg PC (M-PC), or 30 mg M plus 25 mg P (M-P) in a randomized double-blind crossover study. In a secondary study, nine patients were tested on three separate days before and after receiving PLAC, 25 mg P, or 30 mg M plus 25 mg P.

PATIENTS

Seven COPD patients (FEV1=0.99 +/- 0.30 L, Vo2max=990 +/- 315 mL/min) who were ventilatory-limited.

SETTING

Veterans Affairs medical center.

RESULTS

After the patients ingested M-P, the increase in the Vo2max (129.0 +/- 104 mL/min), the workload (10.0 +/- 6.5 W) and the maximum minute ventilation (4.0 +/- 3.9 L/min) were significantly greater (p<0.05) than after PLAC ingestion (-4.8 +/- 79 mL/min, 1.4 +/- 6.9 W, and -1.6 +/- 2.4 L/min, respectively). Changes after the ingestion of M, P, o r M-PC were intermediate. The M-PC combination adversely affected the patient's reported mental status (Bond visual analog scale) more than the M-P or M regimens. No regimen significantly affected the reaction time.

CONCLUSIONS

We conclude that the administration of 30 mg of M plus 25 mg of P significantly improves the exercise tolerance of patients with COPD, without significantly impairing the mental capabilities of the subjects. The utility of this regimen over longer time periods needs to be evaluated.

Symptom assessment

Medical intervention aims to eliminate disease, to mitigate disease effect, and maximize quality of life. Throughout the course of illness, accurate symptom assessment is imperative if these goals are to be achieved. Symptom scales may facilitate this process in the clinical setting. Many valid scales are available for research, and investigators must be familiar with a methodology that can quantify the impact of therapies on symptoms, symptom distress, and overall QOL.

Measurement of dyspnoea in chronic obstructive pulmonary disease

This paper reviews the assessment of shortness of breath in chronic obstructive pulmonary disease (COPD). The validity criteria for evaluating measures of dyspnoea are discussed and a description and critique of current measures of shortness of breath are offered. Across studies, dyspnoea measures are moderately correlated with pulmonary function (e.g. FEV1.0 and FVC), psychological function, and walking tests (6 min walk). In addition, dyspnoea measures tend to be correlated with one another. The need for standardisation of dyspnoea measures for research and clinical practice is identified as an important objective for future work.

Ventilatory and P0.1 response to hypercapnia in quadriplegia

Unlike individuals with comparable degrees of respiratory muscle weakness from other causes, quadriplegic patients have a blunted ventilatory and P0.1 response to hypercapnia. This suggests that the diminished response in quadriplegia is due, in part, to an alteration in respiratory drive. We measured the hypercapnic response in 9 subjects with chronic quadriplegia (Q) and 8 normal controls (N). Ventilatory muscle strength, maximum voluntary ventilation (MVV), and lung volumes were measured in all subjects. The ventilatory response (HCVR) in Q was significantly less than in N (0.73 +/- 0.37 vs 2.95 +/- 0.4 L.min-1.mmHg-1; P less than 0.001), even when normalized for indices of respiratory muscle performance (e.g., vital capacity, MVV). There was no significant change in the HCVR in Q after the administration of naloxone. We also serially studied 2 subjects with acute quadriplegia, and found that despite progressive improvement in respiratory muscle performance, there was no accompanying increase in the response to hypercapnia. These data suggest that muscle weakness alone cannot explain the blunted hypercapnic response in quadriplegia, and are consistent with the hypothesis that these subjects have a reduced ventilatory drive.

Dyspnoea assessed by visual analogue scale in patients with chronic obstructive lung disease during progressive and high intensity exercise

BACKGROUND

A study was carried out to determine whether rating of dyspnoea by means of a visual analogue scale during a progressive exercise test is affected by the subject's awareness of the progressive nature of the protocol.

METHODS

Nineteen patients with chronic obstructive lung disease (FEV1 mean (SE) 1.06 (0.07) 1) were studied. A preliminary incremental test was carried out with a work rate increasing by 10 watts every minute until the subject could no longer exercise, to determine the maximum work load (Wmax) and to anchor the upper end of the visual analogue scale. This was followed by two exercise tests performed one day apart in randomised sequence, with two different protocols. One was a 12 minute protocol that included two sudden bursts of three minute high intensity exercise, up to the subject's Wmax, each preceded by three minutes of low level exercise. The other test was a conventional three minute incremental test lasting 12 minutes. On both study days the only information given to the subject about the temporal profile of load was that a change would be made every three minutes. The relation between dyspnoea, as assessed by the visual analogue scale, and ventilation, measured during high intensity or progressive exercise, was studied.

RESULTS

The mean (SE) rates of increase of dyspnoea with increasing ventilation (% of line length 1(-1) min) obtained by linear regression analysis were similar for the two tests (2.86 (0.20) for progressive exercise and 2.87 (0.25) for high intensity exercise); it was 2.59 (0.25) for the initial burst of high intensity exercise when the data on this were analysed separately. In six subjects with stable disease studied again two months later the reproducibility of the rating of dyspnoea was reasonably good for both protocols.

CONCLUSION

The results suggest that in most patients with chronic obstructive lung disease the assessment of exercise induced dyspnoea by means of a visual analogue scale during a progressive exercise test is not affected by the subject's awareness of the progressive increase in work intensity.

Measurement of breathlessness during exercise in asthmatics. Predictor variables, reliability, and responsiveness

The purpose of this study was to determine the predictor variables for breathlessness and to investigate the criteria of reliability and responsiveness for measuring breathlessness during progressive, incremental exercise on the cycle ergometer. We studied a heterogeneous group of patients with stable asthma (mean +/- SEM age, 46 +/- 4 yr) for four visits at weekly intervals. Predictor variables were determined at the first visit. Nine independent physiologic variables were obtained at each minute during exercise; the Borg rating of breathlessness (range 0 to 10) was used as the dependent variable. The regression model relating the physiologic parameters to the Borg rating of breathlessness was highly significant (model F = 43.4; p = 0.0001). Backward elimination selected the strongest predictors of the Borg rating: peak inspiratory flow (VI); tidal volume (VT)/FVC; frequency of respiration (f); and peak inspiratory mouth pressures (Pm). These four variables explained 63% of the variance in the rating of dyspnea. Each of the four variables exhibited a linear relationship with the Borg rating. Test-retest reliability was assessed by comparing results at the first and second visits. Individual slopes (except for VT/FVC) and intercepts for the four predictor variables versus Borg ratings were highly reliable. The slope for work intensity (watts) and Borg ratings, but not the intercept, was highly reliable. Responsiveness was evaluated by randomly administering inhaled methacholine or inhaled metaproterenol, alternately, at the third and fourth visits to induce acute changes in lung function before exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensation and control of breathing: a dynamic model

A dynamic model of the CO2 respiratory control system is proposed, which can provide a qualitative basis for predicting breathing sensations. The discomfort index, which represents breathing sensations, is assumed to be composed of two sources: the arterial CO2 level and the respiratory motor command. The respiratory controller receives inhibitory neuromechanical and excitatory CO2 signals from the plant. The CO2 signal is enhanced by exercise stimuli. This dynamic multiplicative-type controller is used in simulations of key experiments: exercise and CO2 rebreathing with and without resistive loading. The dynamics of the discomfort index, the respiratory motor command, ventilation, and arterial CO2 concentration conform to the experimental data. The perceptual sensitivity to CO2 relative to respiratory effort is significantly correlated with the slope of hypercapnic ventilatory response. This result shows a clear linkage between ventilatory response and breathing sensations. Although it is shown that the automatic controller effectively minimizes the discomfort index for perturbations about an operating point under certain conditions, the discomfort index itself does not seem to be an underlying control principle of the proposed automatic controller model. Rather, breathing sensations may influence ventilatory responses by modifying the output of the automatic controller.

Variability of breathlessness measurement in patients with chronic obstructive pulmonary disease

The purpose of our study was to evaluate the reproducibility of a Borg rating of dyspnea in patients with COPD. We examined nine patients with COPD who performed a SST on four separate days within a ten-day period. The patients walked on a treadmill for 6 min. At the end of each minute, patients matched a Borg rating to the intensity of their breathlessness. We measured the HR, VE, VO2, VT and f at the end of each minute. While the mean VO2, VE, HR, VT and f stabilized after one or two attempts, the Borg ratings decreased with successive tests. We conclude that the Borg scale for measuring breathlessness shows progressive decreases with repetition whereas VO2, VE, HR, VT and f stabilize after one or two practice attempts. This suggests that desensitization to dyspnea may play a role in the improvement of patients after exercise.

Dyspnea: a sensory experience

Dyspnea--an unpleasant or uncomfortable awareness of breathing or need to breathe--is a common symptom of patients with cardiopulmonary disease. Although often thought of as a single symptom, dyspnea probably subsumes many sensations. Experimental conditions used to induce dyspnea are characterized by discrete groups or clusters of descriptive phrases. Similarly, as the language of dyspnea is refined further, different disease states may be distinguishable by the nuances of breathlessness described by patients. Evidence is gathering that the sensations of dyspnea are modified by information from a variety of receptors throughout the respiratory system. The sense of effort, although still important in the breathlessness associated with mechanical loads, is insufficient to explain the dyspnea arising from a number of experimental and clinical conditions. As our understanding of the interactions between effort and afferent information from the respiratory system grows, new therapeutic interventions to alleviate dyspnea are likely to follow.

Long-term management of respiratory symptoms in advanced cancer

Respiratory symptoms are a common cause of distress in patients with advanced cancer. Optimal palliative therapy requires careful assessment and the appropriate use of symptomatic measures in conjunction with specific antitumor treatments. The etiology and management of the three major respiratory symptoms, dyspnea, cough and hemoptysis, are described. The indications for antitumor treatments and surgical procedures are briefly outlined, and symptomatic treatments, including drug and nondrug measures, are discussed in detail.

The effects of hypoxia and hypercapnia on perceived breathlessness during exercise in humans

1. The sensation of breathlessness increases when ventilation is reflexly stimulated but it is not clear whether different stimuli have specific effects in the genesis of this sensation. 2. Our aim was to compare subjective assessments of the intensity of breathlessness at the same levels of ventilation induced by different combinations of reflex ventilatory stimuli. 3. Against a background of progressive exercise (maximum workload 170 W) in 'blinded' normal naive subjects, normoxic hypercapnia (maximum end-tidal CO2, PET, CO2, 56 mmHg) or isocapnic hypoxia (minimum O2 saturation 88%) was induced to achieve levels of ventilation (maximum 60 l min-1) 'matched' with those resulting from a higher intensity of exercise alone. Subjective breathlessness was rated with a visual analogue scale. 4. For a given ventilation, compared with exercise alone, breathlessness scores were similar during hypercapnia and were lower during hypoxia. 5. These results do not support the idea that during exercise, hypercapnia or hypoxia has a specific role in the genesis of the sensation of breathlessness. 6. The findings are consistent with the hypothesis that the degree of reflex ventilatory activation, however achieved, is an important determinant of the intensity of perceived breathlessness in healthy humans.