Dynamic hyperinflation is associated with a poor cardiovascular response to exercise in COPD patients

<p>Abstract</p> <p>Background</p> <p>Pulmonary hyperinflation has the potential for significant adverse effects on cardiovascular function in COPD. The aim of this study was to investigate the relationship between dynamic hyperinflation and cardiovascular response to maximal exercise in COPD patients.</p> <p>Methods</p> <p>We studied 48 patients (16F; age 68 yrs ± 8; BMI 26 ± 4) with COPD. All patients performed spirometry, plethysmography, lung diffusion capacity for carbon monoxide (TLco) measurement, and symptom-limited cardiopulmonary exercise test (CPET). The end-expiratory lung volume (EELV) was evaluated during the CPET. Cardiovascular response was assessed by change during exercise in oxygen pulse (ΔO₂Pulse) and double product, i.e. the product of systolic blood pressure and heart rate (DP reserve), and by the oxygen uptake efficiency slope (OUES), i.e. the relation between oxygen uptake and ventilation.</p> <p>Results</p> <p>Patients with a peak exercise EELV (%TLC) ≥ 75% had a significantly lower resting FEV₁/VC, FEF₅₀/FIF₅₀ratio and IC/TLC ratio, when compared to patients with a peak exercise EELV (%TLC) < 75%. Dynamic hyperinflation was strictly associated to a poor cardiovascular response to exercise: EELV (%TLC) showed a negative correlation with ΔO₂Pulse (<it>r = - 0.476, p = 0.001</it>), OUES (<it>r = - 0.452, p = 0.001</it>) and DP reserve (<it>r = - 0.425, p = 0.004</it>). Furthermore, according to the ROC curve method, ΔO₂Pulse and DP reserve cut-off points which maximized sensitivity and specificity, with respect to a EELV (% TLC) value ≥ 75% as a threshold value, were ≤ 5.5 mL/bpm (0.640 sensitivity and 0.696 specificity) and ≤ 10,000 Hg · bpm (0.720 sensitivity and 0.783 specificity), respectively.</p> <p>Conclusion</p> <p>The present study shows that COPD patients with dynamic hyperinflation have a poor cardiovascular response to exercise. This finding supports the view that in COPD patients, dynamic hyperinflation may affect exercise performance not only by affecting ventilation, but also cardiac function.</p

Vagal determinants of exercise capacity

British Heart Foundation (A.V.G., G.L.A.; Ref: RG/14/4/30736), The Wellcome Trust (A.V.G.; Refs 095064 and 200893), Medical Research Council (S.K.; Ref: MR/L020661/1), Academy of Medical Sciences/Health Foundation Clinician Scientist Fellowship (G.L.A.), and Royal College of Anaesthetists/British Journal of Anaesthesia Basic Science Career Development Award (G.L.A.). MB PhD funding for A.M. was provided by the Medical Research Council and The Rosetrees Trust. A.V.G. is a Wellcome Trust Senior Research Fellow

Criteria for Selection of Surrogates Used To Study the Fate and Control of Pathogens in the Environment

This article defines the term surrogate as an organism, particle, or substance used to study the fate of a pathogen in a specific environment. Pathogenic organisms, nonpathogenic organisms, and innocuous particles have been used as surrogates for a variety of purposes, including studies on survival and transport as well as for method development and as “indicators” of certain conditions. This article develops a qualitative surrogate attribute prioritization process and allows investigators to select a surrogate by systematically detailing the experimental process and prioritizing attributes. The results are described through the use of case studies of various laboratories that have used this process. This article also discusses the history of surrogate and microbial indicator use and outlines the method by which surrogates can be used when conducting a quantitative microbial risk assessment. The ultimate goal of selecting a sufficiently representative surrogate is to improve public health through a health-based risk assessment framework. Under- or overestimating the resistance, inactivation, or movement may negatively impact risk assessments that, in turn, will impact health assessments and estimated safety levels. Reducing uncertainty in a risk assessment is one of the objectives of using surrogates and the ultimate motive for any experiment investigating potential exposure of a pathogen