Prediction of maximal oxygen uptake and power during cycle ergometry in subjects older than 55 years of age

Cardiorespiratory fitness components in relation to clinical characteristics, disease state and medication intake: A patient registry study

BACKGROUND

Interpretation of cardiopulmonary exercise testing (CPET) results requires thorough understanding of test confounders such as anthropometrics, comorbidities and medication. Here, we comprehensively assessed the clinical determinants of cardiorespiratory fitness and its components in a heterogeneous patient sample.

METHODS

We retrospectively collected medical and CPET data from 2320 patients (48.2% females) referred for cycle ergometry at the University Hospital Leuven, Belgium. We assessed clinical determinants of peak CPET indexes of cardiorespiratory fitness (CRF) and its hemodynamic and ventilatory components using stepwise regression and quantified multivariable-adjusted differences in indexes between cases and references.

RESULTS

Lower peak load and peak O2 uptake were related to: higher age, female sex, lower body height and weight, and higher heart rate; to the intake of beta blockers, analgesics, thyroid hormone replacement and benzodiazepines; and to diabetes mellitus, chronic kidney disease, non-ST elevation myocardial infarction and atrial fibrillation (p < 0.05 for all). Lower peak load also correlated with obstructive pulmonary diseases. Stepwise regression revealed associations of hemodynamic and ventilatory indexes (including heart rate, O2 pulse, systolic blood pressure and ventilation at peak exercise and ventilatory efficiency) with age, sex, body composition and aforementioned diseases and medications. Multivariable-adjusted differences in CPET metrics between cases and controls confirmed the associations observed.

CONCLUSION

We described known and novel associations of CRF components with demographics, anthropometrics, cardiometabolic and pulmonary diseases and medication intake in a large patient sample. The clinical implications of long-term noncardiovascular drug intake for CPET results require further investigation.

Normative cardiopulmonary exercise data for endurance athletes: the Cardiopulmonary Health and Endurance Exercise Registry (CHEER)

AIMS

Accurate interpretation of cardiopulmonary exercise testing (CPET) relies on age, gender, and exercise modality-specific reference values. To date, clinically applicable CPET reference values derived from a source population of endurance athletes (EAs) have been lacking. The purpose of this study was to generate CPET reference values for use in the clinical assessment of EA.

METHODS AND RESULTS

Prospective data accrued during the clinical care of healthy EA were used to derive CPET reference values and to develop novel equations for V˙O2peak. The performance of these equations was compared to the contemporary standard of care equations and assessed in a discrete EA validation cohort. A total of 272 EA (age = 42 ± 15 years, female = 31%, V˙O2peak = 3.6 ± 0.83 L/min) met inclusion criteria and comprised the derivation cohort. V˙O2peak prediction equations derived from general population cohorts described a modest amount of V˙O2peak variability [R2 = 0.58-0.70, root mean square error (RMSE) = 0.46-0.54 L/min] but were mis-calibrated (calibration-in-the-large = 0.45-1.18 L/min) among EA leading to significant V˙O2peak underestimation. Newly derived, externally validated V˙O2peak prediction equations for EA that included age, sex, and height for both treadmill (R2 = 0.74, RMSE = 0.42 L/min) and cycle ergometer CPET (Cycle: R2 = 0.69, RMSE = 0.42 L/min) demonstrated improved accuracy.

CONCLUSION

Commonly used V˙O2peak prediction equations derived from general population cohorts perform poorly among competitive EA. Newly derived CPET reference values including novel V˙O2peak prediction equations may improve the clinical utility of CPET in this rapidly growing patient population.

High-intensity exercise impairs extradiaphragmatic respiratory muscle perfusion in patients with COPD

The study investigated whether high-intensity exercise impairs inspiratory and expiratory muscle perfusion in patients with chronic obstructive pulmonary disease (COPD). We compared respiratory local muscle perfusion between constant-load cycling[sustained at 80% peak work rate (WRpeak)] and voluntary normocapnic hyperpnea reproducing similar work of breathing (WoB) in 18 patients [forced expiratory volume in the first second (FEV₁): 58 ± 24% predicted]. Local muscle blood flow index (BFI), using indocyanine green dye, and fractional oxygen saturation (%StiO₂) were simultaneously assessed by near-infrared spectroscopy (NIRS) over the intercostal, scalene, rectus abdominis, and vastus lateralis muscles. Cardiac output (impedance cardiography), WoB (esophageal/gastric balloon catheter), and diaphragmatic and extradiaphragmatic respiratory muscle electromyographic activity (EMG) were also assessed throughout cycling and hyperpnea. Minute ventilation, breathing pattern, WoB, and respiratory muscle EMG were comparable between cycling and hyperpnea. During cycling, cardiac output and vastus lateralis BFI were significantly greater compared with hyperpnea [by +4.2 (2.6-5.9) L/min and +4.9 (2.2-7.8) nmol/s, respectively] (P < 0.01). Muscle BFI and %StiO₂ were, respectively, lower during cycling compared with hyperpnea in scalene [by -3.8 (-6.4 to -1.2) nmol/s and -6.6 (-8.2 to -5.1)%], intercostal [by -1.4 (-2.4 to -0.4) nmol/s and -6.0 (-8.6 to -3.3)%], and abdominal muscles [by -1.9 (-2.9 to -0.8) nmol/s and -6.3 (-9.1 to -3.4)%] (P < 0.001). The difference in respiratory (scalene and intercostal) muscle BFI between cycling and hyperpnea was associated with greater dyspnea (Borg CR10) scores (r = -0.54 and r = -0.49, respectively, P < 0.05). These results suggest that in patients with COPD, 1) locomotor muscle work during high-intensity exercise impairs extradiaphragmatic respiratory muscle perfusion and 2) insufficient adjustment in extradiaphragmatic respiratory muscle perfusion during high-intensity exercise may partly explain the increased sensations of dyspnea.NEW & NOTEWORTHY We simultaneously assessed the blood flow index (BFI) in three respiratory muscles during hyperpnea and high-intensity constant-load cycling sustained at comparable levels of work of breathing and respiratory neural drive in patients with COPD. We demonstrated that high-intensity exercise impairs respiratory muscle perfusion, as intercostal, scalene, and abdominal BFI increased during hyperpnea but not during cycling. Insufficient adjustment in respiratory muscle perfusion during exercise was associated with greater dyspnea sensations in patients with COPD.

Greater exercise tolerance in COPD during acute interval, compared to equivalent constant-load, cycle exercise: physiological mechanisms

KEY POINTS

Exercise intolerance is common in chronic obstructive pulmonary disease (COPD) patients. In patients with COPD, we compared an interval exercise (IE) protocol (alternating 30 s at 100% peak work rate (WR_peak ) with 30 s at 50% WR_peak ) with moderate-intensity constant-load exercise (CLE) at 75% WR_peak , which yielded the same work rate. Exercise endurance time and total work output were almost twice as high for IE than CLE. At exercise isotime (when work completed was the same between IE and CLE), IE was associated with less dynamic hyperinflation, lower blood lactate concentration, and greater respiratory and locomotor muscle oxygenation, but there were no differences in ventilation or cardiac output. However, at the limit of tolerance for each modality, dynamic hyperinflation was not different between IE and CLE, while blood lactate remained lower and muscle oxygenation higher with IE. Taken together, these findings suggest that dynamic hyperinflation and not muscle-based factors dictate the limits of tolerance in these COPD patients.

ABSTRACT

The relative importance of ventilatory, circulatory and peripheral muscle factors in determining tolerance to exercise in patients with chronic obstructive pulmonary disease (COPD) is not known. In 12 COPD patients (forced expiratory volume in one second: 58 ± 17%pred.) we measured ventilation, cardiac output, dynamic hyperinflation, local muscle oxygenation, blood lactate and time to exhaustion during (a) interval exercise (IE) consisting of 30 s at 100% peak work rate alternating with 30 s at 50%, and (b) constant-load exercise (CLE) at 75% peak work rate, designed to produce the same average work rate. Exercise time was substantially longer during IE than CLE (19.5 ± 4.8 versus 11.4 ± 2.1 min, p = 0.0001). Total work output was therefore greater during IE than CLE (81.3 ± 27.7 versus 48.9 ± 23.8 kJ, p = 0.0001). Dynamic hyperinflation (assessed by changes from baseline in inspiratory capacity, ΔIC) was less during IE than CLE at CLE exhaustion time (isotime, p = 0.009), but was similar at exhaustion (ΔIC_CLE : -0.38 ± 0.10 versus ΔIC_IE : -0.33 ± 0.12 l, p = 0.102). In contrast, at isotime, minute ventilation, cardiac output and systemic oxygen delivery did not differ between protocols (P > 0.05). At exhaustion in both protocols, the vastus lateralis and intercostal muscle oxygen saturation were higher in IE than CLE (p = 0.014 and p = 0.0002, respectively) and blood lactate concentrations were lower (4.9 ± 2.4 mmol l^-1 versus 6.4 ± 2.2 mmol l^-1 , p = 0.039). These results suggest that (1) exercise tolerance with COPD is limited by dynamic hyperinflation; and (2) cyclically lower (50%) effort intervals in IE help to preserve muscle oxygenation and reduce metabolic acidosis compared with CLE at the same average work rate; but these factors do not appear to determine time to exhaustion.

Assessing the effects of inspiratory muscle training in a patient with unilateral diaphragm dysfunction

A 55-year-old man was referred to the outpatient pulmonary department of our hospital because of dyspnoea during exertion and when bending forward, which had been present for at least 6 months. He reported experiencing severe symptoms of breathlessness and many of his daily activities had to be adapted or interrupt due to symptoms (as documented by the Baseline Dyspnea Index (BDI)) (table 1). Recent infectious episodes or episodes of neck or shoulder pain were absent. His medical history included systemic arterial hypertension, obesity (body mass index (BMI) 36 kg·m⁻²), and obstructive sleep apnoea for which he was treated with night-time continuous positive airway pressure therapy (8 cmH₂O). He was a former smoker (18 pack-years) who quit smoking 15 years ago. 8 months ago, he underwent abdominal surgery (transabdominal epigastric hernia repair). The presence of cardiopulmonary disease and other aetiologies, such as neuromuscular disease, was excluded. Chest radiograph showed an elevated left hemidiaphragm and impaired left phrenic nerve conduction (i.e. increased latency and compound muscle action potential (CMAP) duration) after electrical stimulation (table 1) [1].

Patients with diaphragm dysfunction experience exertional dyspnoea. Respiratory muscle function assessments can identify breathing abnormalities and IMT might help to reduce symptoms (mostly via improvements in non-diaphragmatic muscles).http://bit.ly/2QdxNFP

Manipulation of mechanical ventilatory constraint during moderate intensity exercise does not influence dyspnoea in healthy older men and women

KEY POINTS

The perceived intensity of exertional breathlessness (i.e. dyspnoea) is higher in older women than in older men, possibly as a result of sex-differences in respiratory system morphology. During exercise at a given absolute intensity or minute ventilation, older women have a greater degree of mechanical ventilatory constraint (i.e. work of breathing and expiratory flow limitation) than their male counterparts, which may lead to a greater perceived intensity of dyspnoea. Using a single-blind randomized study design, we experimentally manipulated the magnitude of mechanical ventilatory constraint during moderate-intensity exercise at ventilatory threshold in healthy older men and women. We found that changes in the magnitude of mechanical ventilatory constraint within the physiological range had no effect on dyspnoea in healthy older adults. When older men and women perform moderate intensity exercise, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea.

ABSTRACT

We aimed to determine the effect of manipulating mechanical ventilatory constraint during submaximal exercise on dyspnoea in older men and women. Eighteen healthy subjects (aged 60-80 years; nine men and nine women) completed two days of testing. On day 1, subjects were assessed for pulmonary function and performed a maximal incremental cycle exercise test. On day 2, subjects performed three 6-min bouts of cycling at ventilatory threshold, in a single-blind randomized manner, while breathing: (i) normoxic helium-oxygen (HEL) to reduce the work of breathing (W_b ) and alleviate expiratory flow limitation (EFL); (ii) through an inspiratory resistance (RES) of ∼5 cmH₂ O L^-1  s^-1 to increase W_b ; and (iii) ambient air as a control (CON). Oesophageal pressure, diaphragm electromyography, and sensory responses (category-ratio 10 Borg scale) were monitored throughout exercise. During the HEL condition, there was a significant decrease in W_b (men: -21 ± 6%, women: -17 ± 10%) relative to CON (both P < 0.01). Moreover, if EFL was present during CON (four men and five women), it was alleviated during HEL. Conversely, during the RES condition, W_b (men: 42 ± 19%, women: 50 ± 16%) significantly increased relative to CON (both P < 0.01). There was no main effect of sex on W_b (P = 0.59). Across conditions, women reported significantly higher dyspnoea intensity than men (2.9 ± 0.9 vs. 1.9 ± 0.8 Borg scale units, P < 0.05). Despite significant differences in the degree of mechanical ventilatory constraint between conditions, the intensity of dyspnoea was unaffected, independent of sex (P = 0.46). When older men and women perform moderate intensity exercise, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea.

Inspiratory muscle training reduces diaphragm activation and dyspnea during exercise in COPD

Among patients with chronic obstructive pulmonary disease (COPD), those with the lowest maximal inspiratory pressures experience greater breathing discomfort (dyspnea) during exercise. In such individuals, inspiratory muscle training (IMT) may be associated with improvement of dyspnea, but the mechanisms for this are poorly understood. Therefore, we aimed to identify physiological mechanisms of improvement in dyspnea and exercise endurance following inspiratory muscle training (IMT) in patients with COPD and low maximal inspiratory pressure (Pi_max). The effects of 8 wk of controlled IMT on respiratory muscle function, dyspnea, respiratory mechanics, and diaphragm electromyography (EMGdi) during constant work rate cycle exercise were evaluated in patients with activity-related dyspnea (baseline dyspnea index <9). Subjects were randomized to either IMT or a sham training control group ( n = 10 each). Twenty subjects (FEV₁ = 47 ± 19% predicted; Pi_max  = -59 ± 14 cmH₂O; cycle ergometer peak work rate = 47 ± 21% predicted) completed the study; groups had comparable baseline lung function, respiratory muscle strength, activity-related dyspnea, and exercise capacity. IMT, compared with control, was associated with greater increases in inspiratory muscle strength and endurance, with attendant improvements in exertional dyspnea and exercise endurance time (all P < 0.05). After IMT, EMGdi expressed relative to its maximum (EMGdi/EMGdi_max) decreased ( P < 0.05) with no significant change in ventilation, tidal inspiratory pressures, breathing pattern, or operating lung volumes during exercise. In conclusion, IMT improved inspiratory muscle strength and endurance in mechanically compromised patients with COPD and low Pi_max. The attendant reduction in EMGdi/EMGdi_max helped explain the decrease in perceived respiratory discomfort despite sustained high ventilation and intrinsic mechanical loading over a longer exercise duration. NEW & NOTEWORTHY In patients with COPD and low maximal inspiratory pressures, inspiratory muscle training (IMT) may be associated with improvement of dyspnea, but the mechanisms for this are poorly understood. This study showed that 8 wk of home-based, partially supervised IMT improved respiratory muscle strength and endurance, dyspnea, and exercise endurance. Dyspnea relief occurred in conjunction with a reduced activation of the diaphragm relative to maximum in the absence of significant changes in ventilation, breathing pattern, and operating lung volumes.

Neurophysiological mechanisms of exertional dyspnoea in fibrotic interstitial lung disease

Our understanding of the mechanisms of dyspnoea in fibrotic interstitial lung disease (ILD) is incomplete. The aims of this study were two-fold: 1) to determine whether dyspnoea intensity is better predicted by neural respiratory drive (NRD) or neuromechanical uncoupling (NMU) of the respiratory system in fibrotic ILD, and 2) to examine the effect of breathing 60% oxygen on NRD, NMU and dyspnoea ratings.Fourteen patients with fibrotic ILD were included. Visit 1 comprised a familiarisation incremental cycle exercise test, Visit 2 comprised a normoxic incremental cycling test to address Aim 1, and Visits 3 and 4 consisted of constant-load cycling while breathing room air or 60% oxygen to address Aim 2. Diaphragmatic electromyography (EMGdi) was used as a surrogate of NRD. NMU was calculated as the ratio between EMGdi (%max) and tidal volume (%vital capacity).On adjusted analysis, NMU and its constituents were all significantly associated with dyspnoea ratings during incremental cycling, with EMGdi having the strongest correlation. The between-treatment change in dyspnoea ratings during constant load cycling was only correlated with change in exercise endurance time and NMU.Dyspnoea more strongly reflected the level of EMGdi than NMU in fibrotic ILD. However, the improvement in dyspnoea with 60% oxygen was better predicted by improvements in NMU.

Exercise training for people following curative intent treatment for non-small cell lung cancer: a randomized controlled trial

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Lung resection for lung cancer is associated with marked reductions in exercise capacity.

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Exercise training increased exercise capacity in people with non-small cell lung cancer.

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Exercise training did not improve other outcomes.

Objective

In people following curative intent treatment for non-small cell lung cancer, to investigate the effects of supervised exercise training on exercise capacity, physical activity and sedentary behavior, peripheral muscle force, health-related quality of life, fatigue, feelings of anxiety and depression, and lung function.

Method

This pilot randomized controlled trial included participants 6–10 weeks after lobectomy for non-small cell lung cancer or, for those who required adjuvant chemotherapy, 4–8 weeks after their last cycle. Participants were randomized to either 8 weeks of supervised exercise training (exercise group) or 8 weeks of usual care (control group). Prior to and following the intervention period, both groups completed measurements of exercise capacity, physical activity and sedentary behavior, quadriceps and handgrip force, HRQoL, fatigue, feelings of anxiety and depression, and lung function. Intention-to-treat analysis was undertaken.

Results

Seventeen participants (mean age 67, SD = 9 years; 12 females) were included. Nine and eight participants were randomized to the exercise and control groups, respectively. Four participants (44%) adhered to exercise training. Compared with any change seen in the control group, those in the exercise group demonstrated greater gains in the peak rate of oxygen consumption (mean difference, 95% confidence interval for between-group difference: 0.19 [0.04–0.33] L min⁻¹) and 6-minute walk distance (52 [12–93] m). No other between-group differences were demonstrated.

Conclusions

In people following curative intent treatment for non-small cell lung cancer, 8 weeks of supervised exercise training improved exercise capacity, measured by both laboratory- and field-based exercise tests. These results suggest that this clinical population may benefit from attending exercise training programs.

Maximal aerobic capacity in ageing subjects: actual measurements versus predicted values

We evaluated the impact of selection of reference values on the categorisation of measured maximal oxygen consumption (V′_O2peak) as “normal” or “abnormal” in an ageing population.

We compared measured V′_O2peak with predicted values and the lower limit of normal (LLN) calculated with five equations. 99 (58 males and 41 females) disease-free subjects aged ≥70 years completed an incremental maximal exercise test on a cycle ergometer.

Mean V′_O2peak was 1.88 L·min⁻¹ in men and 1.26 L·min⁻¹ in women. V′_O2peak ranged from 89% to 108% of predicted in men, and from 88% to 164% of predicted in women, depending on the reference equation used. The proportion of subjects below the LLN ranged from 5% to 14% in men and 0–22% in women, depending on the reference equation. The LLN was lacking in one study, and was unsuitable for women in another. Most LLNs ranged between 53% and 73% of predicted. Therefore, choosing an 80% cut-off leads to overestimation of the proportion of “abnormal” subjects.

To conclude, the proportion of subjects aged ≥70 years with a “low” V′_O2peak differs markedly according to the chosen reference equations. In clinical practice, it is still relevant to test a sample of healthy volunteers and select the reference equations that better characterise this sample.

As V′_O2peak% pred differs markedly with the reference value, reference equation choice is critical in the elderlyhttp://ow.ly/YsXHD

Respiratory Factors Contributing to Exercise Intolerance in Breast Cancer Survivors: A Case-Control Study

CONTEXT

Breast cancer survivors often experience activity-related dyspnea and exercise intolerance, but the underlying mechanisms remain unknown.

OBJECTIVES

We evaluated physiological contributors to reduced peak oxygen uptake (VO2), with particular attention to the role of respiratory impairment.

METHODS

We compared symptom assessments, respiratory and peripheral muscle strength, pulmonary function, and ventilatory responses to symptom-limited incremental treadmill exercise in 29 women who had survived breast cancer and 29 age-matched healthy controls.

RESULTS

Peak VO2 was reduced more than 20%, on average, in the cancer group compared with controls (P < 0.001). Slopes of dyspnea intensity ratings over ventilation or VO2 were >50% greater in the cancer group compared to controls (P < 0.05). Women with breast cancer had lower lung diffusing capacity for carbon monoxide (DLCO), respiratory and limb muscle strength, and ventilatory thresholds during exercise compared with controls (all P < 0.05). During exercise, indices of ventilatory efficiency were similar to controls, but inspiratory capacity (IC) was lower and breathing pattern was more rapid and shallow in the cancer group (P < 0.05). The lower peak VO2 in the cancer group was associated with greater dyspnea intensity, and lower DLCO, IC and ventilatory threshold (all P < 0.05).

CONCLUSION

Breast cancer survivors had greater peripheral and respiratory muscle weakness, greater reduction of IC, impaired lung diffusion, and evidence of deconditioning compared with controls. Exercise intolerance was multifactorial and correlated well with the combination of these factors as well as with exertional dyspnea. Individualized physiological testing in breast cancer survivors can identify important contributors to exercise intolerance which can be targeted for treatment.

Comparison of the six-minute walk test with a cycle-based cardiopulmonary exercise test in people following curative intent treatment for non-small cell lung cancer

This study is aimed to (i) compare both the magnitude of impairment in exercise capacity and exercise responses measured during the six-minute walk test (6MWT) and the cardiopulmonary exercise test (CPET) and (ii) investigate the effect of test repetition on six-minute walk distance (6MWD) in people following curative intent treatment for non-small cell lung cancer (NSCLC). Twenty participants (67 ± 10 years; 14 females), 6-10 weeks following lobectomy, underwent a CPET and two 6MWTs. Peak exercise responses, dyspnoea and leg fatigue, as well as heart rate (HR) and oxygen saturation (SpO2) during the 6MWT, were compared to those during the CPET. Compared with exercise capacity when expressed as peak rate of oxygen consumption (%pred) measured during the CPET, exercise capacity when expressed as 6MWD (%pred) was less impaired (81 ± 10 vs. 63 ± 15 %pred; p < 0.001). Compared with the CPET, the 6MWT elicited lower peak HR (119 ± 15 vs. 128 ± 18 beats minute(-1); p = 0.02), lower SpO2 (93 ± 2 vs. 95 ± 3%; p < 0.05), less dyspnoea (3.1 ± 1.6 vs. 6.9 ± 2.6; p < 0.01) and less leg fatigue (2.0 ± 1.9 vs. 6.8 ± 2.4; p < 0.01). The 6MWD increased 19 ± 19 metre (4 ± 4%) with test repetition (p < 0.001). In people following curative intent treatment for NSCLC, the 6MWT appears to elicit sub-maximal exercise responses when compared with the CPET. There is a significant effect of test repetition on 6MWD.

Failed upregulation of TFAM protein and mitochondrial DNA in oxidatively deficient fibers of chronic obstructive pulmonary disease locomotor muscle

Background

Low mitochondrial content and oxidative capacity are well-established features of locomotor muscle dysfunction, a prevalent and debilitating systemic occurrence in patients with chronic obstructive pulmonary disease (COPD). Although the exact cause is not firmly established, physical inactivity and oxidative stress are among the proposed underlying mechanisms. Here, we assess the impact of COPD pathophysiology on mitochondrial DNA (mtDNA) integrity, biogenesis, and cellular oxidative capacity in locomotor muscle of COPD patients and healthy controls. We hypothesized that the high oxidative stress environment of COPD muscle would yield a higher presence of deletion-containing mtDNA and oxidative-deficient fibers and impaired capacity for mitochondrial biogenesis.

Methods

Vastus lateralis biopsies were analyzed from 29 COPD patients and 19 healthy age-matched controls for the presence of mtDNA deletions, levels of oxidatively damaged DNA, mtDNA copy number, and regulators of mitochondrial biogenesis as well the proportion of oxidative-deficient fibers (detected histologically as cytochrome c oxidase-deficient, succinate dehydrogenase positive (COX⁻/SDH⁺ )). Additionally, mtDNA copy number and mitochondrial transcription factor A (TFAM) content were measured in laser captured COX⁻SDH⁺ and normal single fibers of both COPD and controls.

Results

Compared to controls, COPD muscle exhibited significantly higher levels of oxidatively damaged DNA (8-hydroxy-2-deoxyguanosine (8-OHdG) levels = 387 ± 41 vs. 258 ± 21 pg/mL) and higher prevalence of mtDNA deletions (74 vs. 15 % of subjects in each group), which was accompanied by a higher abundance of oxidative-deficient fibers (8.0 ± 2.1 vs. 1.5 ± 0.4 %). Interestingly, COPD patients with mtDNA deletions had higher levels of 8-OHdG (457 ± 46 pg/mL) and longer smoking history (66.3 ± 7.5 years) than patients without deletions (197 ± 29 pg/mL; 38.0 ± 7.3 years). Transcript levels of regulators of mitochondrial biogenesis and oxidative metabolism were upregulated in COPD compared to controls. However, single fiber analyses of COX⁻/SDH⁺ and normal fibers exposed an impairment in mitochondrial biogenesis in COPD; in healthy controls, we detected a marked upregulation of mtDNA copy number and TFAM protein in COX⁻/SDH⁺ compared to normal fibers, reflecting the expected compensatory attempt by the oxidative-deficient cells to increase energy levels; in contrast, they were similar between COX⁻/SDH⁺ and normal fibers in COPD patients. Taken together, these findings suggest that although the signaling factors regulating mitochondrial biogenesis are increased in COPD muscle, impairment in the translation of these signals prevents the restoration of normal oxidative capacity.

Conclusions

Single fiber analyses provide the first substantive evidence that low muscle oxidative capacity in COPD cannot be explained by physical inactivity alone and is likely driven by the disease pathophysiology.

Effective Bronchoscopic Lung Volume Reduction Accelerates Exercise Oxygen Uptake Kinetics in Emphysema

BACKGROUND

The impact of bronchoscopic lung volume reduction (BLVR) on physiologic responses to exercise in patients with advanced emphysema remains incompletely understood. We hypothesized that effective BLVR (e-BLVR), defined as a reduction in residual volume > 350 mL, would improve cardiovascular responses to exercise and accelerate oxygen uptake (Vo₂) kinetics.

METHODS

Thirty-one patients (FEV1, 36% ± 9% predicted; residual volume, 219% ± 57% predicted) underwent a constant intensity exercise test at 70% peak work rate to the limit of tolerance before and after treatment bronchoscopy (n = 24) or sham bronchoscopy (n = 7). Physiologic responses in patients who had e-BLVR (n = 16) were compared with control subjects (ineffective BLVR or sham bronchoscopy; n = 15).

RESULTS

e-BLVR reduced residual volume (-1.1 ± 0.5 L, P = .001), improved lung diffusing capacity by 12% ± 13% (P = .001), and increased exercise tolerance by 181 ± 214 s (P = .004). Vo₂ kinetics were accelerated in the e-BLVR group but remained unchanged in control subjects (Δ mean response time, -20% ± 29% vs 1% ± 25%, P = .04). Acceleration of Vo₂ kinetics was associated with reductions in heart rate and oxygen pulse response half-times by 8% (84 ± 14 to 76 ± 15 s, P = .04) and 20% (49 ± 16 to 34 ± 16 s, P = .01), respectively. There were also increases in heart rate and oxygen pulse amplitudes during the cardiodynamic phase post e-BLVR. Faster Vo₂ kinetics in the e-BLVR group were significantly correlated with reductions in residual volume (r = 0.66, P = .005) and improvements in inspiratory reserve volume (r = 0.56, P = .024) and exercise tolerance (r = 0.63, P = .008).

CONCLUSIONS

Lung deflation induced by e-BLVR accelerated exercise Vo₂ kinetics in patients with emphysema. This beneficial effect appears to be related mechanistically to an enhanced cardiovascular response to exercise, which may contribute to improved functional capacity.

Multivariate Criteria Most Accurately Distinguish Cardiac from Noncardiac Causes of Dyspnea

Cardiopulmonary exercise testing provides oxygen pulse as a continuous measure of stroke volume, which is superior to other stress-testing methods in which systolic function is measured at baseline and at peak stress. However, the optimal peak oxygen pulse criterion for distinguishing cardiac from noncardiac causes of exercise limitation is unknown. In comparing several peak oxygen pulse criteria against the clinical standard of cardiopulmonary exercise testing, we retrospectively studied 54 consecutive patients referred for cardiopulmonary exercise testing. These exercise tests included measurement of oxygen consumption, carbon dioxide production, breathing reserve, arterial blood gases at baseline and at peak stress, exercise electrocardiogram, heart rate, and blood pressure response. Results were blindly interpreted and patients were categorized as members either of our Cardiac Group (abnormal result secondary to cardiac causes of exercise limitation) or of our Noncardiac Group (normal or abnormal result secondary to any noncardiac cause of exercise limitation). The accuracy of the peak oxygen pulse criteria ranged from 50% for univariate criterion (≤15 mL/beat), to 61% for oxygen pulse curve pattern, to 63% for bivariate criterion (≤15 mL/beat for men, ≤10 mL/beat for women), to as high as 81% for a multivariate criterion. All multivariate criteria outperformed oxygen pulse curve pattern, univariate, and bivariate criteria. This is the first study to evaluate the optimal peak oxygen pulse criterion for differentiating cardiac from noncardiac causes of exercise limitation. Multivariate criteria (especially a criterion incorporating age, sex, height, and weight) should be used preferentially, as opposed to the commonly used univariate and bivariate criteria.

Inhaled fentanyl citrate improves exercise endurance during high-intensity constant work rate cycle exercise in chronic obstructive pulmonary disease

CONTEXT

Activity limitation and dyspnea are the dominant symptoms of chronic obstructive pulmonary disease (COPD). Traditionally, efforts to alleviate these symptoms have focused on improving ventilatory mechanics, reducing ventilatory demand, or both of these in combination. Nevertheless, many patients with COPD remain incapacitated by dyspnea and exercise intolerance despite optimal therapy.

OBJECTIVES

To determine the effect of single-dose inhalation of nebulized fentanyl citrate (a μ-opioid agonist drug) on exercise tolerance and dyspnea in COPD.

METHODS

In a randomized, double-blind, placebo-controlled, crossover study, 12 stable patients with COPD (mean ± standard error of the mean post-β(2)-agonist forced expiratory volume in one second [FEV(1)] and FEV(1) to forced vital capacity ratio of 69% ± 4% predicted and 49% ± 3%, respectively) received either nebulized fentanyl citrate (50 mcg) or placebo on two separate days. After each treatment, patients performed pulmonary function tests and a symptom-limited constant work rate cycle exercise test at 75% of their maximum incremental work rate.

RESULTS

There were no significant postdose differences in spirometric parameters or plethysmographic lung volumes. Neither the intensity nor the unpleasantness of perceived dyspnea was, on average, significantly different at isotime (5.0 ± 0.6 minutes) or at peak exercise after treatment with fentanyl citrate vs. placebo. Compared with placebo, fentanyl citrate was associated with 1) increased exercise endurance time by 1.30 ± 0.43 minutes or 25% ± 8% (P=0.01); 2) small but consistent increases in dynamic inspiratory capacity by ∼0.10 L at isotime and at peak exercise (both P≤0.03); and 3) no concomitant change in ventilatory demand, breathing pattern, pulmonary gas exchange, and/or cardiometabolic function during exercise. The mean rate of increase in dyspnea intensity (1.2 ± 0.3 vs. 2.9 ± 0.8 Borg units/minute, P=0.03) and unpleasantness ratings (0.5 ± 0.2 vs. 2.9 ± 1.3 Borg units/minute, P=0.06) between isotime and peak exercise was less after treatment with fentanyl citrate vs. placebo.

CONCLUSION

Single-dose inhalation of fentanyl citrate was associated with significant and potentially clinically important improvements in exercise tolerance in COPD. These improvements were accompanied by a delay in the onset of intolerable dyspnea during exercise near the limits of tolerance.

Bronchodilation improves endurance but not muscular efficiency in chronic obstructive pulmonary disease

We hypothesized that bronchodilator treatment not only improves hyperinflation and endurance capacity but also muscular efficiency in stable chronic obstructive pulmonary disease (COPD). We aimed to demonstrate that tiotropium and salmeterol improve muscular efficiency compared with placebo. Twenty-five COPD patients were studied, including 20 males of mean (standard deviation) age 62 years (7 years) with baseline forced expiratory volume in 1 second of 41% (10%) predicted, and maximal workload of 101 Watt (36 Watt). Subjects were randomized for 6-week treatment with tiotropium 18 μg once daily, salmeterol 50 μg twice daily, or placebo using a double-blind, crossover design. Muscular efficiency and endurance time were measured during cycling at 50% of maximal work load. Resting energy expenditure was measured using a ventilated hood. Muscular efficiency after tiotropium, salmeterol, and placebo treatment was 14.6%, 14.4%, and 14.4%, respectively (P > 0.05), and resting energy expenditure was 1485 kcal/24 hours, 1709 kcal/24 hours, and 1472 kcal/24 hours (P > 0.05), respectively. Endurance time after tiotropium treatment was significantly higher than that after placebo (27.0 minutes versus 19.3 minutes [P = 0.02]), whereas endurance time after salmeterol treatment was not higher than that after placebo (23.3 minutes [P = 0.22]). In this small study, we were not able to demonstrate that bronchodilator therapy improved muscular efficiency. Apparently, reduced costs of breathing relative to total energy expenditure were too small to be detected.

Creatine kinase isoforms as circulating markers of deterioration in idiopathic dilated cardiomyopathy

BACKGROUND

A proportion of patients with dilated cardiomyopathy (DCM) may have ongoing myocardial damage secondary to viral or immune mediated myocardial inflammation.

HYPOTHESIS

The prognostic determinants identify patients with decreased survival but do not provide a measure of myocardial damage. To obtain an objective assessment of myocardial damage in DCM, we measured plasma levels of creatine kinase (CK), its isoenzymes (CK-MM and CK-MB), and separated the isoforms of CK-MM and CK-MB.

METHODS

The cohort consisted of 77 consecutive patients (61 men, 16 women) with DCM (World Health Organization criteria), aged 49 +/- 14 years (range 19-60). Patients had been symptomatic for 29 +/- 38 months (range 0.5-200 months) with 48 in New York Heart Association class I/II and 29 in class III/IV at the time of diagnosis. During median follow-up of 27 months from diagnosis (range 0.6-165), 50 patients remained clinically stable and 27 had deteriorated.

RESULTS

A significantly higher proportion of patients with DCM had abnormal MB2/MB1 ratio compared with normal volunteers (11, 14% vs. 1,1%, p = 0.003). Patients who deteriorated had higher MB2/MB1 ratio, (1.22 +/- 0.62 vs. 0.85 +/- 0.56; p = 0.01), and more frequently had abnormal MB2/ MB1 ratio (8, 30% vs. 3, 6%; p = 0.004) and CK and CK-MM activities (5, 19% vs. 2, 4%; p = 0.03) than those who remained stable. Patients with DCM with high CK-MB activity had 3.13-fold increased odds of sudden death or need for cardiac transplantation (95% confidence interval 1.53-6.40, p = 0.008). Thus, CK measurements, in particular CK-MB isoforms, are markers of myocardial damage in a subset of patients with DCM and could be useful in investigating the possibility of persistent myocardial damage in these patients.

Sex differences in the perceived intensity of breathlessness during exercise with advancing age

The prevalence of activity-related breathlessness increases with age, particularly in women, but the specific underlying mechanisms have not been studied. This novel cross-sectional study was undertaken to examine the effects of age and sex, and their interaction, on the perceptual and ventilatory responses to incremental treadmill exercise in 73 healthy participants (age range 40–80 yr old) with normal pulmonary function. Age-related changes at a standardized oxygen uptake (V̇o2) during exercise included significant increases in breathlessness ratings (Borg scale), ventilation (V̇e), ventilatory equivalent for carbon dioxide, and the ratio of tidal volume (Vt) to dynamic inspiratory capacity (IC) (all P < 0.05). These changes were quantitatively similar in women ( n = 39) and in men ( n = 34). For the group as a whole, exertional breathlessness ratings increased as resting static inspiratory muscle strength diminished ( P = 0.05), as exercise ventilation increased relative to capacity ( P = 0.013) and as the Vt/IC ratio increased ( P = 0.003) during exercise. Older women (60–80 yr old, n = 23) reported greater ( P < 0.05) intensity of exertional breathlessness at a standardized V̇o2 and V̇e than age-matched men ( n = 16), despite similar age-related changes in ventilatory demand and dynamic ventilatory mechanics. These increases in breathlessness ratings in older women disappeared when sex differences in baseline maximal ventilatory capacity were accounted for. In conclusion, although increased exertional breathlessness with advancing age is multifactorial, contributory factors included higher ventilatory requirements during exercise, progressive inspiratory muscle weakness, and restrictive mechanical constraints on Vt expansion related to reduced IC. The sensory consequences of this age-related respiratory impairment were more pronounced in women, who, by nature, have relatively reduced maximal ventilatory reserve.

Mechanisms of dyspnea during cycle exercise in symptomatic patients with GOLD stage I chronic obstructive pulmonary disease

RATIONALE

Smokers with a relatively preserved FEV(1) may experience dyspnea and activity limitation but little is known about underlying mechanisms.

OBJECTIVES

To examine ventilatory constraints during exercise in symptomatic smokers with GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage I chronic obstructive lung disease (COPD) so as to uncover potential mechanisms of dyspnea and exercise curtailment.

METHODS

We compared resting pulmonary function and ventilatory responses (breathing pattern, operating lung volumes, pulmonary gas exchange) with incremental cycle exercise as well as Borg scale ratings of dyspnea intensity in 21 patients (post-bronchodilator FEV(1), 91 +/- 7% predicted, and FEV(1)/FVC, 60 +/- 6%; mean +/- SD) with significant breathlessness and 21 healthy age- and sex-matched control subjects with normal spirometry.

MEASUREMENTS AND MAIN RESULTS

In patients with COPD compared with control subjects, peak oxygen consumption and power output were significantly reduced by more than 20% and dyspnea ratings were higher for a given work rate and ventilation (P < 0.05). Compared with the control group, the COPD group had evidence of extensive small airway dysfunction with increased ventilatory requirements during exercise, likely on the basis of greater ventilation/perfusion abnormalities. Changes in end-expiratory lung volume during exercise were greater in COPD than in health (0.54 +/- 0.34 vs. 0.06 +/- 0.32 L, respectively; P < 0.05) and breathing pattern was correspondingly more shallow and rapid. Across groups, dyspnea intensity increased as ventilation expressed as a percentage of capacity increased (P < 0.0005) and as inspiratory reserve volume decreased (P < 0.0005).

CONCLUSIONS

Exertional dyspnea in symptomatic patients with mild COPD is associated with the combined deleterious effects of higher ventilatory demand and abnormal dynamic ventilatory mechanics, both of which are potentially amenable to treatment.

Depression decreases cardiorespiratory fitness in older women

BACKGROUND

Depression is associated with decreased physical functioning and increased morbidity and mortality from cardiovascular disease and cancer. Whereas physical fitness delays all-cause mortality, little is known of the exercise capacity of depressed women.

METHOD

SPPARCS is a community-based longitudinal study of physical activity and fitness in people > or =55 years. Of 1,246 women, 663 were free of known cardiac and cerebrovascular disease, and performed treadmill exercise. Most (71%) were interviewed and retested 2 years and 4 years later (55%). Two indicators of depression were used: (a) Center for Epidemiologic Studies-Depression Scale (CES-D) > or =16; (b) use of antidepressant medication.

RESULTS

By CES-D score, 8.4% had depressive symptoms (first round). Depressed women showed lower levels of all markers of treadmill exercise [exercise duration, peak VO2, Oxygen Uptake Efficiency Slope (OUES)].

CONCLUSIONS

Depression is associated with impaired physical fitness and treadmill exercise performance in older women.

Radiographic (ILO) readings predict arterial oxygen desaturation during exercise in subjects with asbestosis

BACKGROUND

Exercise impairment is common in subjects with asbestosis. Arterial oxygen desaturation during exercise is an important contributor to exercise limitation. The International Labour Office (ILO) classification of plain chest radiographs correlates with resting pulmonary function, but its value in predicting abnormal ventilatory responses to exercise, including desaturation, has not been explored.

AIMS

To determine in subjects with asbestosis (1) if radiographic profusion scores and the extent of small irregular shadows on plain chest radiographs correlate with resting lung function and abnormal ventilatory responses to exercise; and (2) if radiographic scores add value to resting lung function tests in predicting abnormal ventilatory responses to exercise.

METHODS

Thirty eight male subjects with asbestosis were included. Plain chest radiographs were read according to the ILO classification independently by three observers. All subjects underwent assessment of lung function and an incremental exercise test.

RESULTS

Profusion scores and number of affected zones correlated significantly with the percentage predicted values of single breath diffusing capacity (DLCO), forced vital capacity (FVC), and total lung capacity (TLC). Arterial oxygen desaturation occurred in 29% of the subjects. The severity of desaturation correlated significantly with profusion and the number of affected zones. The combined use of number of affected zones, FEV(1)/FVC ratio and DLCO predicted desaturation during exercise with an explained variance of 41%. VO(2)max was significantly related only to DLCO but was not predicted by the ILO score.

CONCLUSION

Arterial oxygen desaturation correlated with the profusion and extent of parenchymal abnormality on chest radiographs. The addition of morphological indices to physiological measurements is valuable for predicting oxygen desaturation during exercise but not for VO(2)max. Refinement of the radiographic scoring system and the addition of more sophisticated imaging techniques may further improve the predictive power.

Maximal Workload and Oxygen Uptake during Exercise after Aortic-Valve Replacement

Context:

It is more feasible to assess functional capacity with an exercise test than to measure peak-exercise VO2.

Objective:

To assess whether maximal workload reliably predicts peak VO2.

Patients:

Thirty-six patients after aortic-valve replacement during routine follow-up.

Design:

Incremental symptom-limited cycle exercise test in the upright position with increments of 20 W/min.

Setting:

Out-clinic patients, university hospital.

Main Outcome Measures:

Maximal workload, ventilatory threshold, and peak VO2.

Results:

Maximal workload was 151 ± 39 W, and peak VO2, 1649 ± 486 ml/min. The correlation coefficient between maximal workload and peak VO2wasr= .92 (P< .0001). The regression equation for the estimation of peak VO2wasy= 11.7 (maximal workload in watts) – 110.7. Peak VO2calculated with this equation was 1657 ± 451 ml/min.

Conclusions:

Maximal workload during ergometry in the upright position reliably predicted peak VO2.

Standardized submaximal exercise testing in never smokers: a normative study

In a population survey on the south-western coast of Norway, 373 never smokers aged 18-73 years (230 women) without respiratory symptoms performed a standardized, progressive, incremental submaximal bicycle exercise test. All individuals were able to do an exercise involving oxygen uptake of 1.0 l min(-1), 80% of the subjects reached 1.5 l min(-1) and 50% of the subjects reached 2.0 l min(-1). The respiratory frequency (RF), ventilation (VE) and heart rate (HR) for a given oxygen uptake were all higher in women than in men. Significant predictors of failure to reach oxygen uptake of 1.5 and 2.0 l min(-1) were sex, age, body height and weight. Prediction equations are given for respiratory frequency, heart rate and ventilation for an oxygen uptake of 1.0 l min(-1) in women and 1.5 l min(-1) in men; and body height is a strong predictor for all dependent variables. A multiple linear regression analysis in women showed that age was a significant predictor of respiratory frequency (P<0.05), ventilation (P<0.001) and heart rate (P<0.001), while in men age was a significant predictor only of ventilation (P<0.001) during the bicycle exercise protocol.

Effect of asbestos-related pleural fibrosis on excursion of the lower chest wall and diaphragm

To examine mechanisms responsible for reduced lung volumes (restriction) in asbestos-related pleural fibrosis (APF), we studied diaphragm function and lower rib-cage excursion in 26 subjects with previous asbestos exposure and no evidence of asbestosis. Using posteroanterior (PA) and lateral chest radiographs taken at residual volume and at 25%, 70%, and 100% vital capacity (VC) during a slow inspiratory maneuver, we measured fractional expansion of the lower rib cage (FErc), fractional shortening of the diaphragm (FSdi), and changes (Delta) in diaphragm dome height (Hdo) and subphrenic volume (Vdi). Vdi was estimated by measuring the major and minor axes of the subphrenic space at 1-cm intervals, assuming an elliptical cross-sectional shape, and correcting for the volume of spinal and paraspinal tissues. Seven subjects had no evidence of APF (control), 12 had pleural plaques (PP), and seven had diffuse pleural thickening with costophrenic obliteration (DPT). Over the range of VC, results (mean +/- SEM, normalized for height) in control subjects were VC = 101.2 +/- 4.0 % predicted and DeltaVdi = 326 +/- 8 ml/m(3), and for the right hemithorax and hemidiaphragm on the PA film, FErc = 0.07 +/- 0.02, FSdi = 0.32 +/- 0.02 and DeltaHdo = 0.8 +/- 0.2 cm/m. Relative to controls: DPT subjects had reduced VC (77.4 +/- 4.9%, p < 0.01), DeltaVdi (256 +/- 2 ml/m(3), p < 0.01), FErc (0.01 +/- 0.02, p < 0.01), FSdi (0.24 +/- 0.01, p < 0.001), and DeltaHdo (-0.9 +/- 0.06 cm/m, p < 0.01); PP subjects had reduced FSdi (0.25 +/- 0.01, p < 0.001) and DeltaVdi (233 +/- 47 ml/m(3), p < 0.01), and no difference in FErc, DeltaHdo, or VC. We conclude that restriction in DPT is due to obliteration of the zone of apposition, and that by limiting separation of the diaphragm from the rib cage during inspiration, this reduces volume contributed by motion of the diaphragm and lower rib cage. Reduction in the latter contribution was the main cause of restriction, because the reduction in volume contributed by the diaphragm was partly compensated by flattening of its dome.

Familial dilated cardiomyopathy: cardiac abnormalities are common in asymptomatic relatives and may represent early disease

OBJECTIVES

This study sought to determine whether early disease is identifiable in asymptomatic relatives of patients with dilated cardiomyopathy (DCM) by means of noninvasive cardiologic assessment.

BACKGROUND

DCM is diagnosed on the basis of advanced heart failure, where cardiac dilation and impaired contractility are recognized in the absence of a recognized etiology (World Health Organization criteria). However, initial clinical presentation may be with severe complications: thromboembolism, arrhythmia or sudden death. DCM has recently been recognized to be familial, with autosomal dominant inheritance in many cases. Familial disease is present in 9% to 20% of patients with DCM, and the ability to identify early disease in such people may improve patient management and aid in the understanding of pathogenesis.

METHOD

We prospectively assessed 408 asymptomatic relatives (mean [+/-SD] age 35 +/- 15 years, 193 men) of 110 consecutive patients with DCM by means of history and physical examination, two-dimensional echocardiography, 12-lead and signal-averaged electrocardiography and metabolic exercise testing. We hypothesized that signs of lesser cardiac dysfunction in such relatives might indicate early disease.

RESULTS

Twenty-nine percent of relatives had abnormal results on the echocardiogram. Twenty percent (n = 45) had left ventricular enlargement (LVE), defined as LV end-diastolic diameter (LVEDD) > or = 112% predicted; 6% (n = 13) had depressed fractional shortening (dFS), defined as FS < or = 25%; and 3% (n = 7) had frank DCM, defined as LV dilation, impaired contractile performance and LVEDD > or = 112% plus FS < or = 25%. Other abnormalities of cardiac function were identified in relatives with LVE or dFS: A greater number with LVE had an abnormal metabolic exercise test result than normal relatives (9% vs. 1%, p < 0.05). Relatives with LVE and abnormal maximal oxygen consumption (VO2max) (defined as VO2max < 80% predicted) had a lower absolute VO2max than normal relatives (30 +/- 8 vs. 43 +/- 9 ml/min per kg, p = 0.01). The QRS duration (at the 25-Hz filter) on the signal-averaged electrocardiogram was prolonged in relatives with LVE (103 +/- 13 ms) and dFS (102 +/- 12 ms) compared with that of normal relatives (97 +/- 12 ms, p < 0.05). Over a mean 39-month follow-up period, 12 relatives with LVE (27%) and none with dFS developed symptomatic DCM (p < 0.0001). One relative with LVE died suddenly, and another underwent heart transplantation.

CONCLUSIONS

Nearly one-third of asymptomatic relatives (29%) have echocardiographic abnormalities, and 27% of such relatives progress to development of overt DCM. Early identification of such people would permit appropriate intervention that might influence the serious complications and mortality of this disease.

Analysis of the metabolic and ventilatory response to self-paced 12-minute treadmill walking in patients with severe chronic obstructive pulmonary disease

BACKGROUND

The 12-minute walking test is frequently used to measure exercise capacity in patients with severe chronic obstructive pulmonary disease. However, the physiological response to this test has been the subject of limited investigation.

METHODS

In this study, the metabolic and ventilatory consequences of a self-paced 12-minute treadmill walking test (WT) were measured in 17 patients with severe chronic obstructive pulmonary disease (FEV1: 40 +/- 9%) and evaluated using the physiological response to symptom-limited cycle ergometry (CE). During exercise testing, heart rate, transcutaneous oxygen saturation, and lactate concentration were measured, and oxygen consumption, carbon dioxide production, tidal volume, and breathing frequency were recorded breath by breath.

RESULTS

After 4 minutes walking, the peak oxygen consumption (VO2) was already 99 +/- 11% of last-minute walking VO2. Walking speed was chosen within 2 minutes and remained stable throughout the test. The WT and CE showed similar (end-) test results for all measurements, except for a higher carbon dioxide production, venous lactate concentration, and respiratory quotient after CE. However, lactate concentration was also significantly increased after WT. Severe and prolonged desaturation was shown during walking in most patients.

CONCLUSIONS

The physiological stress evoked during the WT is close to the stress developed at an incremental symptom-limited test and the relatively high metabolic and ventilatory stress is sustained from at least 4 to 12 minutes during the WT. This study has shown that anaerobic metabolism not only occurs during incremental cycle ergometry, but also during the WT.

Decreased mechanical efficiency in clinically stable patients with COPD

BACKGROUND

It has recently been reported that total daily energy expenditure (TDE) is increased in patients with chronic obstructive pulmonary disease (COPD) and it was hypothesised that these patients may have a decreased mechanical efficiency during activities. The purpose of the present study was to measure the mechanical efficiency of submaximal leg exercise, and to characterise patients with a potentially low efficiency in terms of body composition, resting energy expenditure, lung function, and symptom limited exercise performance.

METHODS

Metabolic and ventilatory variables were measured breath by breath during submaximal cycle ergometry exercise performed at 50% of symptom limited achieved maximal load in 33 clinically stable patients with COPD (23 men) with forced expiratory volume in one second (FEV1) of 40 (12)% predicted. Net mechanical efficiency was calculated adjusting for resting energy expenditure (REE).

RESULTS

Median mechanical efficiency was 15.5% and ranged from 8.5% to 22.7%. Patients with an extremely low mechanical efficiency (< 17%, n = 21) demonstrated an increased VO2/VE compared with those with a normal efficiency (median difference 4.7 ml/l, p = 0.005) during submaximal exercise. There was no difference between the groups differentiated by mechanical efficiency in blood gas tensions at rest, airflow obstruction, respiratory muscle strength, hyperinflation at rest, resting energy expenditure or body composition. There was a significant difference in total airways resistance (92% predicted, p = 0.03) between the groups differentiated by mechanical efficiency.

CONCLUSIONS

It is concluded that many patients with severe COPD have decreased mechanical efficiency. Furthermore, based on the results of this study it is hypothesised that an increased oxygen cost of breathing during exercise contributes to the decreased mechanical efficiency.

Cardiac autoantibodies in dilated cardiomyopathy become undetectable with disease progression

OBJECTIVE

To determine the relation of cardiac autoantibody and disease status in a consecutive series of patients with dilated cardiomyopathy by prospective antibody testing at diagnosis and at follow up.

METHODS

Antibody status was assessed by indirect immunofluorescence in 110 patients with dilated cardiomyopathy (85 male, mean (SD) age 44 (13) years) at diagnosis and at follow up (mean (SD) 14 (12) months); in 57 of them cardiac specific anti-alpha myosin antibody titres were also measured by an enzyme-linked immunosorbent assay (ELISA). Patients underwent complete evaluation at diagnosis and clinical and non-invasive assessment at follow up, including exercise testing with maximal oxygen consumption measurements.

RESULTS

The frequency of cardiac specific antibodies by immunofluorescence was lower at follow up than at diagnosis (28 (25%) v 11 (10%), P = 0.002). Mean (SEM) anti-alpha myosin antibody titres at follow up were also lower than at diagnosis (0.24 (0.02) v 0.30 (0.02), P = 0.038); 24% of patients at diagnosis and 14% at follow up had an abnormal ELISA result. None of the patients who were negative by immunofluorescence or ELISA at diagnosis became positive at follow up. Presence of antibody at diagnosis was associated with milder symptoms and greater exercise capacity at follow up and persistence of antibody at follow up was associated with stable disease and milder symptoms at diagnosis.

CONCLUSIONS

Cardiac specific autoantibodies in dilated cardiomyopathy become undetectable with disease progression; this is a recognised feature of other autoimmune conditions, such as type 1 diabetes. Detection of these antibodies at diagnosis and at follow up may provide a non-invasive marker of early dilated cardiomyopathy.

Decreased heart rate variability in patients with congestive heart failure and chronotropic incompetence

Heart rate variability was studied in 41 patients (aged 48 +/- 12 years) with congestive heart failure secondary to idiopathic dilated cardiomyopathy. All patients underwent a treadmill exercise test and 24-hour Holter ECG monitoring. Chronotropic incompetence was defined as the failure to achieve > or = 80% of the predicted maximal heart rate response given by 220--age (years) at peak exercise. Spectral heart rate variability was analyzed from 24-hour Holter ECGs and was expressed as total (0.01-1.00 Hz), low (0.04-0.15 Hz), and high (0.15-0.40 Hz) frequency components. The standard deviation of all normal RR intervals (SDNN) was also computed. Chronotropic incompetence was observed in ten patients. Peak oxygen consumption was significantly lower in patients with chronotropic incompetence compared with those without chronotropic incompetence. The total (5.11 +/- 1.26 ln [ms2] vs 6.41 +/- 0.92 ln [ms2]; P = 0.009) and low (3.38 +/- 1.65 ln [ms2] vs 5.45 +/- 1.34 ln [ms2]; P = 0.003), but not the high (3.42 +/- 1.04 ln [ms2] vs 4.00 +/- 1.12 ln [ms2]; P = 0.249) frequency components of heart rate variability were significantly lower in patients with chronotropic incompetence, although there was no significant difference in mean heart rate (88 +/- 20 beats/min vs 86 +/- 15 beats/min; P = 0.831) or left ventricular ejection fraction (22% +/- 10% vs 24% +/- 10%; P = 0.619). SDNN was also significantly lower in patients with chronotropic incompetence compared with those without chronotropic incompetence (64 +/- 34 ms vs 102 +/- 37 ms; P = 0.030).

CONCLUSIONS

The observation that heart rate variability is significantly decreased in patients with congestive heart failure who have chronotropic incompetence suggests that chronotropic incompetence may relate to an abnormal autonomic influence on the heart in these patients.

Abnormal cytokine profiles in patients with idiopathic dilated cardiomyopathy and their asymptomatic relatives

OBJECTIVES

Immunological abnormalities in idiopathic dilated cardiomyopathy (DCM) include an increase in soluble interleukin (IL)-2 receptor, disease specific cardiac autoantibodies, an HLA-DR4 association, and familial aggregation of disease; however, cytokine profiles have not been defined. Serum concentrations of IL-2, IL-4, IL-10, and IL-12 were measured in patients with DCM (WHO criteria), relatives with asymptomatic left ventricular enlargement (LVE), patients with ischaemic heart failure (IHD), and healthy controls.

DESIGN

Serum from 20 individuals from each of the four groups was assayed for cytokine concentrations by a commercial enzyme linked immunosorbent assay.

RESULTS

IL-2 concentrations were abnormally increased in DCM patients and relatives with LVE. Concentrations of IL-10 were increased in DCM patients. Concentrations of IL-4 and IL-12 were not increased in any of the groups.

CONCLUSION

These abnormalities may reflect defective/inappropriate T cell function in patients with DCM and in their relatives with LVE.

Autoimmunity to alpha myosin in a subset of patients with idiopathic dilated cardiomyopathy

OBJECTIVE

To use an enzyme linked immunoassay (ELISA) technique to assess frequency and disease specificity of anti-alpha-myosin antibodies in patients with dilated cardiomyopathy and their relatives.

METHODS

Evaluation was performed on sera (dilution 1/320) from 123 consecutive patients with dilated cardiomyopathy (WHO criteria) (age 42 (SD 14) years), 252 of their relatives (35 (17) years), 203 healthy controls (45 (16) years), and 92 patients with ischaemic heart disease (63 (11) years).

RESULTS

Abnormal antibody levels were commoner in patients with dilated cardiomyopathy (25, 20%) than in ischaemic heart disease (4, 4%), or normal controls (4, 2%, P = 0.001). Forty one (16%) of the relatives had abnormal results compared to the controls (4, 2%, P < 0.001) and antibodies were detected in 20 (38%) of pedigrees. Relatives from non-familial kindreds had higher antibody levels than those with familial disease (P << 0.001), and higher antibody levels were identified in 53 relatives of probands who had abnormal results compared to 116 relatives for whom the proband had a normal result (0.37 (SEM 0.02) v 0.22 (0.01); P < 0.001).

CONCLUSIONS

The finding of anti-alpha-myosin antibodies in 20% of patients with dilated cardiomyopathy, in 16% of their asymptomatic relatives, and in 38% of families (particularly those with non-familial disease and where proband also had an abnormal result) provides additional evidence for autoimmunity against alpha myosin in a subset of patients.