Patterns of Oxygen Pulse Curve in Response to Incremental Exercise in Patients with Chronic Obstructive Pulmonary Disease - An Observational Study

Inter- and intra-observer reliability and agreement of O2Pulse inflection during cardiopulmonary exercise testing: A comparison of subjective and novel objective methodology

Cardiopulmonary exercise testing (CPET) is the 'gold standard' method for evaluating functional capacity, with oxygen pulse (O2Pulse) inflections serving as a potential indicator of myocardial ischaemia. However, the reliability and agreement of identifying these inflections have not been thoroughly investigated. This study aimed to assess the inter- and intra-observer reliability and agreement of a subjective quantification method for identifying O2Pulse inflections during CPET, and to propose a more robust and objective novel algorithm as an alternative methodology. A retrospective analysis was conducted using baseline data from the HIIT or MISS UK trial. The O2Pulse curves were visually inspected by two independent examiners, and compared against an objective algorithm. Fleiss' Kappa was used to determine the reliability of agreement between the three groups of observations. The results showed almost perfect agreement between the algorithm and both examiners, with a Fleiss' Kappa statistic of 0.89. The algorithm also demonstrated excellent inter-rater reliability (ICC) when compared to both examiners (0.92-0.98). However, a significant level (P ≤0.05) of systematic bias was observed in Bland-Altman analysis for comparisons involving the novice examiner. In conclusion, this study provides evidence for the reliability of both subjective and novel objective methods for identifying inflections in O2Pulse during CPET. These findings suggest that further research into the clinical significance of O2Pulse inflections is warranted, and that the adoption of a novel objective means of quantification may be preferable to ensure equality of outcome for patients.

Utility of Cardiopulmonary Exercise Testing in Chronic Obstructive Pulmonary Disease: A Review

Chronic obstructive pulmonary disease (COPD) is a disease defined by airflow obstruction with a high morbidity and mortality and significant economic burden. Although pulmonary function testing is the cornerstone in diagnosis of COPD, it cannot fully characterize disease severity or cause of dyspnea because of disease heterogeneity and variable related and comorbid conditions affecting cardiac, vascular, and musculoskeletal systems. Cardiopulmonary exercise testing (CPET) is a valuable tool for assessing physical function in a wide range of clinical conditions, including COPD. Familiarity with measurements made during CPET and its potential to aid in clinical decision-making related to COPD can thus be useful to clinicians caring for this population. This review highlights pulmonary and extrapulmonary impairments that can contribute to exercise limitation in COPD. Key elements of CPET are identified with an emphasis on measurements most relevant to COPD. Finally, clinical applications of CPET demonstrated to be of value in the COPD setting are identified. These include quantifying functional capacity, differentiating among potential causes of symptoms and limitation, prognostication and risk assessment for operative procedures, and guiding exercise prescription.

The concept of detection of dynamic lung hyperinflation using cardiopulmonary exercise testing

Dynamic lung hyperinflation (DLH) caused by air trapping, which increases residual air volume, is a common cause of shortness of breath on exertion in chronic obstructive pulmonary disease (COPD). DLH is commonly evaluated by measuring the decrease in maximal inspiratory volume during exercise, or using the hyperventilation method. However, only few facilities perform these methods, and testing opportunities are limited. Therefore, we investigated the possibility of visually and qualitatively detecting DLH using data from a cardiopulmonary exercise test (CPET). Four men who underwent symptom-limiting CPET were included in this study, including a male patient in his 60s with confirmed COPD, a 50s male long-term smoker, and 2 healthy men in their 20s and 70s, respectively. We calculated the difference between the inspiratory tidal volume (TV I) and expiratory tidal volume (TV E) per breath (TV E-I) from the breath-by-breath data of each CPET and plotted it against the time axis. No decrease in TV E-I was observed in either of the healthy men. However, in the patient with COPD and long-term smoker, TV E-I began to decrease immediately after the initiation of exercise. These results indicate that DLH can be visually detected using CPET data. However, this study was a validation of a limited number of cases, and a comparison with existing evaluation methods and verification of disease specificity are required.

Cardiopulmonary exercise testing and efficacy of percutaneous coronary intervention: a substudy of the ORBITA trial

AIMS

Oxygen-pulse morphology and gas exchange analysis measured during cardiopulmonary exercise testing (CPET) has been associated with myocardial ischaemia. The aim of this analysis was to examine the relationship between CPET parameters, myocardial ischaemia and anginal symptoms in patients with chronic coronary syndrome and to determine the ability of these parameters to predict the placebo-controlled response to percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Patients with severe single-vessel coronary artery disease (CAD) were randomized 1:1 to PCI or placebo in the ORBITA trial. Subjects underwent pre-randomization treadmill CPET, dobutamine stress echocardiography (DSE) and symptom assessment. These assessments were repeated at the end of a 6-week blinded follow-up period.A total of 195 patients with CPET data were randomized (102 PCI, 93 placebo). Patients in whom an oxygen-pulse plateau was observed during CPET had higher (more ischaemic) DSE score [+0.82 segments; 95% confidence interval (CI): 0.40 to 1.25, P = 0.0068] and lower fractional flow reserve (-0.07; 95% CI: -0.12 to -0.02, P = 0.011) compared with those without. At lower (more abnormal) oxygen-pulse slopes, there was a larger improvement of the placebo-controlled effect of PCI on DSE score [oxygen-pulse plateau presence (Pinteraction = 0.026) and oxygen-pulse gradient (Pinteraction = 0.023)] and Seattle angina physical-limitation score [oxygen-pulse plateau presence (Pinteraction = 0.037)]. Impaired peak VO2, VE/VCO2 slope, peak oxygen-pulse, and oxygen uptake efficacy slope was significantly associated with higher symptom burden but did not relate to severity of ischaemia or predict response to PCI.

CONCLUSION

Although selected CPET parameters relate to severity of angina symptoms and quality of life, only an oxygen-pulse plateau detects the severity of myocardial ischaemia and predicts the placebo-controlled efficacy of PCI in patients with single-vessel CAD.

Using Machine Learning to Identify Organ System Specific Limitations to Exercise via Cardiopulmonary Exercise Testing

Cardiopulmonary Exer cise Testing (CPET) is a unique physiologic medical test used to evaluate human response to progressive maximal exercise stress. Depending on the degree and type of deviation from the normal physiologic response, CPET can help identify a patient's specific limitations to exercise to guide clinical care without the need for other expensive and invasive diagnostic tests. However, given the amount and complexity of data obtained from CPET, interpretation and visualization of test results is challenging. CPET data currently require dedicated training and significant experience for proper clinician interpretation. To make CPET more accessible to clinicians, we investigated a simplified data interpretation and visualization tool using machine learning algorithms. The visualization shows three types of limitations (cardiac, pulmonary and others); values are defined based on the results of three independent random forest classifiers. To display the models' scores and make them interpretable to the clinicians, an interactive dashboard with the scores and interpretability plots was developed. This machine learning platform has the potential to augment existing diagnostic procedures and provide a tool to make CPET more accessible to clinicians.

The Impact of Oxygen Pulse and Its Curve Patterns on Male Patients with Heart Failure, Chronic Obstructive Pulmonary Disease, and Healthy Controls-Ejection Fractions, Related Factors and Outcomes

Oxygen pulse (O2P) is a function of stroke volume and cellular oxygen extraction and O2P curve pattern (O2PCP) can provide continuous measurements of O2P. However, measurements of these two components are difficult during incremental maximum exercise. As cardiac function is evaluated using ejection fraction (EF) according to the guidelines and EF can be obtained using first-pass radionuclide ventriculography, the aim of this study was to investigate associations of O2P%predicted and O2PCP with EF in patients with heart failure with reduced or mildly reduced ejection fraction (HFrEF/HFmrEF) and chronic obstructive pulmonary disease (COPD), and also in normal controls. This was a prospective observational cross-sectional study. Correlations of resting left ventricular EF, dynamic right and left ventricular EFs and outcomes with O2P% and O2PCP across the three participant groups were analyzed. A total of 237 male subjects were screened and 90 were enrolled (27 with HFrEF/HFmrEF, 30 with COPD and 33 normal controls). O2P% and the proportions of the three types of O2PCP were similar across the three groups. O2P% reflected dynamic right and left ventricular EFs in the control and HFrEF/HFmrEF groups, but did not reflect resting left ventricular EF in all participants. O2PCP did not reflect resting or dynamic ventricular EFs in any of the subjects. A decrease in O2PCP was significantly related to nonfatal cardiac events in the HFrEF/HFmrEF group (log rank test, p = 0.01), whereas O2P% and O2PCP did not predict severe acute exacerbations of COPD. The findings of this study may clarify the utility of O2P and O2PCP, and may contribute to the currently used interpretation algorithm and the strategy for managing patients, especially those with HFrEF/HFmrEF. (Trial registration number NCT05189301.).

Prediction and types of dead-space fraction during exercise in male chronic obstructive pulmonary disease patients

A high dead space (VD) to tidal volume (VT) ratio during peak exercise (VD/VTpeak) is a sensitive and consistent marker of gas exchange abnormalities; therefore, it is important in patients with chronic obstructive pulmonary disease (COPD). However, it is necessary to use invasive methods to obtain VD/VTpeak, as noninvasive methods, such as end-tidal PCO2 (PETCO2peak) and PETCO2 adjusted with Jones' equation (PJCO2peak) at peak exercise, have been reported to be inconsistent with arterial PCO2 at peak exercise (PaCO2peak). Hence, this study aimed to generate prediction equations for VD/VTpeak using statistical techniques, and to use PETCO2peak and PJCO2peak to calculate the corresponding VD/VTpeaks (i.e., VD/VTpeakETVD/VTpeakJ).A total of 46 male subjects diagnosed with COPD who underwent incremental cardiopulmonary exercise tests with PaCO2 measured via arterial catheterization were enrolled. Demographic data, blood laboratory tests, functional daily activities, chest radiography, two-dimensional echocardiography, and lung function tests were assessed.In multivariate analysis, diffusing capacity, vital capacity, mean inspiratory tidal flow, heart rate, and oxygen pulse at peak exercise were selected with a predictive power of 0.74. There were no significant differences in the PCO2peak values and the corresponding VD/VTpeak values across the three types (both p = NS).In subjects with COPD, VD/VTpeak can be estimated using statistical methods and the PETCO2peak and PJCO2peak. These methods may have similar predictive power and thus can be used in clinical practice.

Combining Dynamic Hyperinflation with Dead Space Volume during Maximal Exercise in Patients with Chronic Obstructive Pulmonary Disease

Physiological dead space volume (VD) and dynamic hyperinflation (DH) are two different types of abnormal pulmonary physiology. Although they both involve lung volume, their combination has never been advocated, and thus their effect and implication are unclear. This study aimed (1) to combine VD and DH, and (2) investigate their relationship and clinical significance during exercise, as well as (3) identify a noninvasive variable to represent the VD fraction of tidal volume (VD/VT). Forty-six male subjects with chronic obstructive pulmonary disease (COPD) and 34 healthy male subjects matched for age and height were enrolled. Demographic data, lung function, and maximal exercise were investigated. End-expiratory lung volume (EELV) was measured for the control group and estimated for the study group using the formulae reported in our previous study. The VD/VT ratio was measured for the study group, and reference values of VD/VT were used for the control group. In the COPD group, the DHpeak/total lung capacity (TLC, DHpeak%) was 7% and the EELVpeak% was 70%. After adding the VDpeak% (8%), the VDDHpeak% was 15% and the VDEELVpeak% was 78%. Both were higher than those of the healthy controls. In the COPD group, the VDDHpeak% and VDEELVpeak% were more correlated with dyspnea score and exercise capacity than that of the DHpeak% and EELV%, and had a similar strength of correlation with minute ventilation. The VTpeak/TLC (VTpeak%), an inverse marker of DH, was inversely correlated with VD/VT (R2 ≈ 0.50). Therefore, we recommend that VD should be added to DH and EELV, as they are physiologically meaningful and VTpeak% represents not only DH but also dead space ventilation. To obtain VD, the VD/VT must be measured. Because obtaining VD/VT requires invasive arterial blood gases, further studies on noninvasive predicting VD/VT is warranted.

Does oxygen pulse trajectory during incremental exercise discriminate impaired oxygen delivery from poor muscle oxygen utilisation?

Cardiopulmonary exercise testing (CPET) is often helpful to shed light on the mechanisms of exercise intolerance in different clinical populations. Although specific response patterns are rarely pathognomonic, an integrative approach considering metabolic and mechanical–ventilatory responses in addition to limiting symptoms has been valuable to guide further investigations [1].

A flattened or decreasing O₂ pulse trajectory during incremental CPET is commonly found in patents with low exercise stroke volume but not in those with severely impaired muscle O₂ utilisation. This finding should prompt additional cardiovascular work-up.http://bit.ly/2HRE739

Exercise testing in heart failure: a contemporary discussion in an era of novel diagnostic techniques and biomarkers

PURPOSE OF REVIEW

The purpose of this review is to highlight recent advances in the field of exercise testing for patients with heart failure.

RECENT FINDINGS

The importance of assessment of cardiorespiratory fitness (CRF) and exercise testing in heart failure is highlighted in the consensus recommendation of the American Heart Association. Contemporary studies have validated the independent and incremental strength of CRF metrics in patients with heart failure and coronary artery disease. The use of respiratory gas analysis and imaging or hemodynamics during physical exercise is feasible and results in high prognostic utility across the continuum of heart failure. Understanding how CRF metrics complement existing and novel biomarkers and risk scores is an emerging subject of scientific inquiry.

SUMMARY

In the current era of personalized medicine, integrating CRF, imaging and circulating biomarkers will allow us to further develop individualized strategies for improving outcome in patients with heart failure.