Effect of experimental modulation of mood on exertional dyspnoea in chronic obstructive pulmonary disease.

BACKGROUND AND OBJECTIVE: Dyspnoea is a debilitating symptom in individuals with chronic obstructive pulmonary disease (COPD) and a range of other chronic cardiopulmonary diseases and is often associated with anxiety and depression. The present study examined the effect of visually-induced mood shifts on exertional dyspnoea in individuals with COPD. METHODS: Following familiarization, 20 participants with mild to severe COPD (age 57-79 years) attended three experimental sessions on separate days, performing two 5-min treadmill exercise tests separated by a 30-min interval on each day. During each exercise test, participants viewed either a positive, negative or neutral set of images sourced from the International Affective Picture System (IAPS) and rated dyspnoea or leg fatigue (0-10). Heart rate (HR) and peripheral oxygen saturation (SpO2 ) were measured at 1-min intervals during each test. Mood valence ratings were obtained using Self-Assessment Manikin (SAM) scale (1-9). RESULTS: Mood valence ratings were significantly higher when viewing positive (end-exercise mean ± SEM = 7.6 ± 0.3) compared to negative IAPS images (2.4 ± 0.3, p < 0.001). Dyspnoea intensity (mean ± SEM = 5.8 ± 0.4) and dyspnoea unpleasantness (5.6 ± 0.3) when viewing negative images were significantly higher compared to positive images (4.2 ± 0.4, p = 0.004 and 3.4 ± 0.5, p = 0.003). Eighty-five percent of participants (n = 17) met the minimal clinically important difference (MCID) criteria for both dyspnoea intensity and unpleasantness. HR, SpO2 and leg fatigue did not differ significantly between conditions. CONCLUSION: These findings indicate that the negative affective state worsens dyspnoea in COPD, thereby suggesting strategies aimed at reducing the likelihood of negative mood or improving the mood may be effective in managing morbidity associated with dyspnoea in COPD.

Reproducibility and responsiveness of airway impedance measures derived from the forced oscillation technique across different operating lung volumes.

BACKGROUND: The forced oscillation technique (FOT) enables non-invasive measurement of respiratory system impedance. Limited data exists on how changes in operating lung volume (OLV) impact FOT-derived measures of airway resistance (Rrs) and reactance (Xrs). OBJECTIVES: This study examined the reproducibility and responsiveness of FOT-derived measures of Rrs and Xrs during simulated changes in OLV. METHODS: Participants simulated breathing at six OLVs: total lung capacity (TLC), ∼50% of inspiratory reserve volume (IRV50), ∼two-times tidal volume (VT2), tidal volume (VT), ∼50% of expiratory reserve volume (ERV50), and residual volume (RV), on a commercially available FOT device. Each simulated OLV manuever was performed in triplicate and in random order. Total Rrs and Xrs were recorded at 5, 11, and 19 Hz. RESULTS: Twelve healthy participants (2 female) completed the study (weight: 76.5 ± 13.6 kg, height: 178.6 ± 9.7 cm, body mass index: 23.9 ± 3.1 kg/m2). Reproducibility of Rrs and Xrs at VT, VT2 and IRV50 was good to excellent (Range: ICC: 0.89-0.98, 95% confidence interval (CI): 0.70-0.98), while reproducibility at TLC, RV, and ERV50 was poor to excellent (Range: ICC: 0.60-0.98, 95% CI: 0.36-0.97). Rrs and Xrs were not different between VT and VT2 at any frequency (P > .05). With lung hyperinflation from VT to TLC, Rrs and Xrs decreased at all three frequencies (e.g., At 5 Hz Rrs: mean difference (MD): - 0.89, 95%CI: - 0.03 to - 1.75, P = .04; Xrs: MD: - 0.56, 95%CI: - 0.25 to - 0.86, P < .01). With lung hypoinflated from VT to RV, Rrs increased, and Xrs decreased for all frequencies (e.g., MD at 5 Hz, Rrs: MD: 2.31, 95%CI: 0.94-3.67, P < .01; Xrs: MD: -2.53, 95%CI: -4.02 to -1.04, P < .01). CONCLUSION: FOT-derived measures of airway Rrs and Xrs are reproducible across a range of OLV's, and are responsive to hyper- and hypo-inflation of the lung. To further understand the impact of lung hyper- and hypo-inflation on FOT-derived airway impedance additional study is required in individuals with pathological variations in operating lung volume.

Fixed-intensity exercise tests to measure exertional dyspnoea in chronic heart and lung populations: a systematic review.

INTRODUCTION: Exertional dyspnoea is the primary diagnostic symptom for chronic cardiopulmonary disease populations. Whilst a number of exercise tests are used, there remains no gold standard clinical measure of exertional dyspnoea. The aim of this review was to comprehensively describe and evaluate all types of fixed-intensity exercise tests used to assess exertional dyspnoea in chronic cardiopulmonary populations and, where possible, report the reliability and responsiveness of the tests. METHODS: A systematic search of five electronic databases identified papers that examined 1) fixed-intensity exercise tests and measured exertional dyspnoea, 2) chronic cardiopulmonary populations, 3) exertional dyspnoea reported at isotime or upon completion of fixed-duration exercise tests, and 4) published in English. RESULTS: Searches identified 8785 papers. 123 papers were included, covering exercise tests using a variety of fixed-intensity protocols. Three modes were identified, as follows: 1) cycling (n=87), 2) walking (n=31) and 3) other (step test (n=8) and arm exercise (n=2)). Most studies (98%) were performed on chronic respiratory disease patients. Nearly all studies (88%) used an incremental exercise test. 34% of studies used a fixed duration for the exercise test, with the remaining 66% using an exhaustion protocol recording exertional dyspnoea at isotime. Exertional dyspnoea was measured using the Borg scale (89%). 7% of studies reported reliability. Most studies (72%) examined the change in exertional dyspnoea in response to different interventions. CONCLUSION: Considerable methodological variety of fixed-intensity exercise tests exists to assess exertional dyspnoea and most test protocols require incremental exercise tests. There does not appear to be a simple, universal test for measuring exertional dyspnoea in the clinical setting.

Exertional dyspnea responses to the Dyspnea Challenge in heart failure: Comparison to chronic obstructive pulmonary disease.

BACKGROUND: In heart failure (HF), exertional dyspnea is a common symptom, but validated field-based tests for its measurement are limited. The Dyspnea Challenge is a two-minute uphill treadmill walk designed to measure exertional dyspnea in cardiopulmonary disease. OBJECTIVES: The purpose of this study was to establish the test-retest reliability of the Dyspnea Challenge in HF and to compare the exercise responses to a group with chronic obstructive pulmonary disease (COPD). METHODS: The study was an experimental, single-blind, randomized, multi-site project that recruited individuals with HF (New York Heart Association I-III) and COPD (Global Initiative for Chronic Obstructive Lung Disease II-IV). Participants completed two visits. On the first visit, participants performed two six-minute walk tests (6MWT), followed by two to three Dyspnea Challenges to calculate treadmill speed and gradient. At Visit Two, participants performed two separate Dyspnea Challenges, with one including measures of pulmonary gas exchange and central hemodynamics. RESULTS: Twenty-one individuals with HF (10 female; 66±11years; ejection fraction:45.3 ± 6.1%; six-minute distance(6MWD) 520 ± 97 m), and 25 COPD (11 female; 68 ± 10 yr; forced expiratory volume in 1 s:47.6 ± 11.5%; 6MWD: 430 ± 101 m). Intraclass correlation coefficients demonstrated excellent test-retest reliability for HF (0.94, P<.01) and COPD (0.95, P<.01). While achieving similar end-exercise exertional dyspnea intensities (P=.60), the HF group walked at a higher average speed (4.2 ± 0.8 vs. 3.5 ± 0.8km·h-1) and gradient (10.3 ± 2.8 vs. 9.6 ± 2.8%) and a greater oxygen uptake (P<.01) and ventilation (P<.01) than those with COPD. While achieving similar cardiac outputs (P=.98), stroke volumes (P=.97), and heart rates (P=.83), those with HF displayed a larger arteriovenous oxygen difference (P<.01), while those with COPD exhibited greater decreases in inspiratory capacity (P=.03), arterial oxygen saturation (P=.02), and breathing reserve (P<.01). CONCLUSIONS: The Dyspnea Challenge is a reliable test-retest measure of exertional dyspnea in HF. Typical to their pathologies, HF seemed limited by an inadequate modulation of cardiac output, while ventilatory constraints hampered those with COPD.

Exertional Dyspnoea responses reported in the Dyspnoea Challenge and measures of disease severity in COPD.

BACKGROUND: The Dyspnoea Challenge has been developed to facilitate the field-based measure of exertional dyspnoea(ED). To further validate the test, we aimed to; investigate the relationship between end-exercise ED, generated by a fixed-intensity Dyspnoea Challenge(DCFIX), and measures of disease severity (Forced expiratory volume in 1 s(FEV1), six-minute walk distance(6MWD), breathing reserve(V̇E/MVV), modified medical research council dyspnoea scale (mMRC), Body-mass index, airflow Obstruction, Dyspnoea, and Exercise (BODE index) and compare the physiological response of the DCFIX to a six-minute walk test(6MWT). METHODS: Thirty-two individuals (15 female) with COPD (GOLD II-IV) (age: 69.7 ± 9.4 yrs; FEV1: 49.1 ± 18.2 %) performed 2×6MWT and 2xDCFIX at a treadmill speed of 3 km h-1 and gradient of 4 %. The intensity of ED was measured using the modified Borg dyspnoea scale at baseline and end-exercise with heart rate (HR) and oxygen saturation (SpO2) monitored continuously. During 1×6MWT and 1xDCFIX pulmonary gas exchange, cardiac output (Q̇) and dynamic hyperinflation were measured. RESULTS: End-exercise ED measured during the DCFIX was not correlated to FEV1, but moderately correlated to; 6MWD(rs = -0.54, P < .01), V̇E/MVV (rs = 0.46, P = .02), mMRC(rs = 0.45, P = .01), and the BODE index(rs = 0.53, P < .01). When comparing the DCFIX and 6MWT, participants walked to comparable levels of oxygen consumption(P = .38), ventilation(P = .37), Q̇(P = .20), V̇E/MVV(P = .83), maximum HR percentages(P = .67) and dynamically hyperinflated to a similar degree(P = .37). CONCLUSIONS: The Dyspnoea Challenge is correlated to different parameters of disease severity and produces a similar physiological and ED response to that of the 6MWT with the added benefit of being appropriate for longitudinal assessment of ED.

Optimising the Dyspnoea Challenge: exertional dyspnoea responses to changing treadmill gradients.

BACKGROUND: The Dyspnoea Challenge is a two-minute treadmill walk designed to measure exertional dyspnoea(ED). To efficiently individualise workload, we aimed to assess; 1) whether the Dyspnoea Challenge is responsive to 1% changes in treadmill gradient and 2) the minimum gradient variation necessary to generate a clinically meaningful change in ED (≥1 modified Borg scale). METHODS: Thirty individuals with COPD(GOLD II-IV) (age: 69.2 ± 9.2 years; FEV1: 49.3 ± 19.1%) completed six Dyspnoea Challenges at a fixed treadmill speed of 3 km·h-1 and at a gradient of between 3% and 8%, performed in random order. ED intensity and leg fatigue were measured using the 0-10 modified Borg scale. Heart rate(HR) and oxygen saturation(SpO2) were monitored continuously. A multidimensional dyspnoea profile(MDP) was used to quantify the discomfort, physical, e.g., work/effort and breathing frequency, and emotional components of ED. RESULTS: Higher treadmill gradients generated stronger intensities of ED (3%:2.6 ± 1.8; 4%:2.8 ± 2.2; 5%:3.2 ± 2.2; 6%:3.4 ± 2.2; 7%:3.7 ± 1.8; 8%:4.0 ± 2.1units). Statistical changes were observed in ED(e.g.,3 vs. 5%: P = .03) and the MDP discomfort data(e.g.,4 vs. 6%: P = .04) at ≥ a 2% variation in treadmill gradient. Linear regression found a 4% variation in treadmill gradient corresponded to a rise in ED ≥ 1unit. Increases in ED intensity corresponded to heightened sensations of work/effort(P < .01) and breathing frequency(P < .01). There were no changes in emotional constructs(P = .27). While there was an increase in HR with increasing gradient(P < .01), no differences were observed in end-exercise SpO2(P = .79) or leg fatigue(P = .06). CONCLUSION: To significantly change ED, the treadmill gradient must be manipulated by ≥ 2%, with a ≥ 4% change in gradient required to induce a clinically meaningful change in ED.

Examining the repeatability of a novel test to measure exertional dyspnoea in chronic obstructive pulmonary disease.

BACKGROUND: Exertional dyspnoea(ED) is a hallmark of chronic obstructive pulmonary disease(COPD). We examined the repeatability and face validity of the end-exercise ED(EDend) response during the Dyspnoea Challenge and compared those to the six-minute walk test (6MWT) in COPD. METHODS: Twenty-six individuals with COPD(13 Females, age:69 ± 5.5yrs, FEV1:63.4 ± 11.9 %) completed 2 × 6MWTs and 4 x Dyspnoea Challenges on three occasions. The challenge consisted of a two-minute treadmill walk at 80 % of 6MWT speed(3.9 ± 0.5 km·hr-1) at either a low(LIDC:5.3 ± 2%) or high angle of incline(HIDC:9.5 ± 3%). Dyspnoea(0-10 scale), heart rate(HR) and oxygen saturation(SpO2) were monitored continuously. RESULTS: Mean 6MWT distance was 488 ± 58 m. End-exercise ED and HR were higher in the HIDC(EDend 6.2 ± 2.0; HR: 123 ± 17beats·min-1) compared to the LIDC(EDend 4.2 ± 2.0; HR: 119 ± 15beats·min-1) and the 6MWT(EDend 4.3 ± 2.0; HR: 115 ± 16beats·min-1)(P < 0.01). SpO2 was not different between 6MWT, LIDC or HIDC(P = 0.34). The intraclass correlation coefficient(ICC) for each intensity was excellent (HIDC, ICC = 0.88, LIDC, ICC = 0.93, P < 0.001) with neither reporting bias(HIDC, P = 0.63; LIDC, P = 0.94). CONCLUSIONS: The Dyspnoea Challenge is a simple measure of ED that appears to have both repeatability and face validity. With further optimisation, this test may enhance the field-based clinical assessment of ED.