A case for assessment of oscillatory breathing during cardiopulmonary exercise test in risk stratification of elderly patients with chronic heart failure

Beyond exercise oscillatory ventilations: the prognostic impact of loop gain in heart failure

Exercise oscillatory ventilation (EOV) is a strong prognostic marker in patients with heart failure (HF) and left ventricular (LV) dysfunction. This phenomenon can be explained through a single quantitative measurement of ventilatory instability, the loop gain. Therefore, we aimed to evaluate whether loop gain could be a better tool than subjective EOV evaluation to identify HF patients with a higher risk of major cardiovascular complications. This was a single-center retrospective study that included patients with left ventricular ejection fraction (LVEF) ≤ 50% consecutively referred for cardiopulmonary exercise testing (CPET) from 2016-2020. Loop gain was measured through computational evaluation of the minute ventilation graph. Of the 250 patients included, the 66 that presented EOV also had higher values of loop gain, when compared to patients without EOV. Those with both EOV and higher loop gain had more severe HF, with higher NT-proBNP and VE/VCO2 slope as well as lower peak VO2 and LVEF. On multivariable analysis, loop gain was strongly correlated with the composite endpoint of cardiovascular death, urgent heart transplantation, urgent left ventricular assist device implantation or HF hospitalization, even after correcting for peak VO2, LVEF, VE/VCO2 slope and NT-proBNP. Presence of EOV was not prognostically significant in this analysis. Loop gain is an objective parameter that quantifies ventilatory instability and showed to have a strong prognostic value in a cohort of patients with HF and LVEF ≤ 50%, outperforming the classification of EOV.

[Evaluation of respiratory parameters in patients with chronic obstructive lung disease during physical exercises]

AIM

To study the relationship between the indicators of dynamic capnography and pulse oximetry with the indicators of the 6-minute walk test (6MWT) in patients with chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

67 patients of both sexes were examined: 45 patients with COPD (age 60.02.74 years) and 25 patients of the control group (age 47.603.46 years). The study of the functional capabilities of the patients respiratory system was carried out before, during and after the 6MWT on the equipment LifeSense LS1-9R capnograph-pulse oximeter (MedAir AB).

RESULTS AND DISCUSSION

In the comparison group, the parameters of dyspnea at rest were higher than the control group (p0.05), the spirometry indices were significantly lower (p0.05). Shortness of breath as a reason for stopping/slowing down the pace during the 6MWT was noted by patients of both groups (p0.05). When analyzing the PETCO2 trend graphs, periodic breathing (PВ) was revealed. In the group of patients with COPD, signs of PВ in the analysis of the PETCO2 trend were found in 80.95% (p0.05). Regression analysis of Cox proportional risks of mortality in patients with COPD revealed the prognostic value of the following parameters of a comprehensive assessment of the patient: body mass index (BMI), BODE index, dyspnea index on the mMRS scale, Borg, forced expiratory volume in 1 second (FEV1), index Tiffno, signs of PВ, distance 6MWT, signs of PВ and desaturation during 6MWT. At the same time, the total contribution of these indicators to the risk of a lethal event was assessed (p=0.003).

CONCLUSION

When analyzing the correlation dependence, it was revealed that the presence of PВ was a prognostically unfavorable sign in patients with COPD. Predictors of an unfavorable course of COPD were BMI (23.0 kg/m2), BODE index, dyspnea indices on the mMRS, Borg, FEV1 scales, Tiffnos index, signs of PH, distance 6MST, signs of PD and desaturation during 6MST (reliability of the model coefficient p=0.003) in terms of forecast.

Alterations of the respiratory system in heart failure

The review discusses mechanisms for the development of the pathology of the respiratory system in patients with CHF, such as various types of periodic respiration, pulmonary hypertension due to the pathology of the left chambers of the heart, and remodeling of the respiratory musculature. The role of chemo- and baroreceptors of the carotid zone, as well as the hyperactivation of the respiratory muscle metaboreflex in the development of the pathology of the respiratory system, and the mediated exacerbation of CHF are discussed.

Periodic Breathing during Incremental Exercise

Periodic breathing during incremental cardiopulmonary exercise testing is a regularly recurring waxing and waning of tidal volume due to oscillations in central respiratory drive. Periodic breathing is a sign of respiratory control system instability, which may occur at rest or during exercise. The possible mechanisms responsible for exertional periodic breathing might be related to any instability of the ventilatory regulation caused by: (1) increased circulatory delay (i.e., circulation time from the lung to the brain and chemoreceptors due to reduced cardiac index leading to delay in information transfer), (2) increase in controller gain (i.e., increased central and peripheral chemoreceptor sensitivity to arterial partial pressure of oxygen and of carbon dioxide), or (3) reduction in system damping (i.e., baroreflex impairment). Periodic breathing during exercise is observed in several cardiovascular disease populations, but it is a particularly frequent phenomenon in heart failure due to systolic dysfunction. The detection of exertional periodic breathing is linked to outcome and heralds worse prognosis in heart failure, independently of the criteria adopted for its definition. In small heart failure cohorts, exertional periodic breathing has been abolished with several dedicated interventions, but results have not yet been confirmed. Accordingly, further studies are needed to define the role of visceral feedbacks in determining periodic breathing during exercise as well as to look for specific tools for preventing/treating its occurrence in heart failure.

Exercise oscillatory ventilation: Mechanisms and prognostic significance

Alteration in breathing patterns characterized by cyclic variation of ventilation during rest and during exercise has been recognized in patients with advanced heart failure (HF) for nearly two centuries. Periodic breathing (PB) during exercise is known as exercise oscillatory ventilation (EOV) and is characterized by the periods of hyperpnea and hypopnea without interposed apnea. EOV is a non-invasive parameter detected during submaximal cardiopulmonary exercise testing. Presence of EOV during exercise in HF patients indicates significant impairment in resting and exercise hemodynamic parameters. EOV is also an independent risk factor for poor prognosis in HF patients both with reduced and preserved ejection fraction irrespective of other gas exchange variables. Circulatory delay, increased chemosensitivity, pulmonary congestion and increased ergoreflex signaling have been proposed as the mechanisms underlying the generation of EOV in HF patients. There is no proven treatment of EOV but its reversal has been noted with phosphodiesterase inhibitors, exercise training and acetazolamide in relatively small studies. In this review, we discuss the mechanistic basis of PB during exercise and the clinical implications of recognizing PB patterns in patients with HF.

Comprehensive analysis of cardiopulmonary exercise testing and mortality in patients with systolic heart failure: the Henry Ford Hospital cardiopulmonary exercise testing (FIT-CPX) project

BACKGROUND

Many studies have shown a strong association between numerous variables from a cardiopulmonary exercise (CPX) test and prognosis in patients with heart failure with reduced ejection fraction (HFrEF). However, few studies have compared the prognostic value of a majority of these variables simultaneously, so controversy remains regarding optimal interpretation.

METHODS AND RESULTS

This was a retrospective analysis of patients with HFrEF (n = 1,201; age = 55 ± 13 y; 33% female) and a CPX test from 1997 to 2010. Thirty variables from a CPX test were considered in separate adjusted Cox regression analyses to describe the strength of the relation of each to a composite end point of all-cause mortality, left ventricular assist device implantation, or heart transplantation. During a median follow-up of 3.8 years, there were 577 (48.0%) events. The majority of variables were highly significant (P < .001). Among these, percentage of predicted maximum V˙O2 (ppMV˙O2; Wald = 203; P < .001; C-index = 0.73) was similar to VE-VCO2 slope (Wald = 201; P < .001; C = 0.72) and peak V˙O2 (Wald = 161; P < .001; C = 0.72). In addition, there was no significant interaction observed for peak respiratory exchange ratio <1 vs ≥1.

CONCLUSIONS

Consistent with prior studies, many CPX test variables were strongly associated with prognosis in patients with HFrEF. The choice of which variable to use is up to the clinician. Renewed attention should be given to ppMV˙O2, which appears to be highly predictive of survival in these patients.

An overview of the applied definitions and diagnostic methods to assess exercise oscillatory ventilation--a systematic review

The variable "exercise oscillatory ventilation" (EOV), assessed during cardiopulmonary exercise test (CPET), recently became a fundamental prognostic parameter in patients with heart failure. In literature, various definitions are suggested, but an uniformly accepted description to identify EOV still lacks. We performed a systematic review of the literature in order to determine the different definitions and diagnostic techniques to assess EOV. A systematic search strategy was established and executed in seven databases (PubMed, Google Scholar, Cochrane Clinical Trials, Science Direct, Pedro, Web Of Science library and Medline (Ovid)) resulting in 605 citations after de-duplication. Full-text articles (n=124) were assessed for eligibility, resulting in 75 citations. The review accounted 17,440 patients of whom 4,638 subjects presented EOV. Seven studies described EOV in a non-heart failure population accounting 168 EOV subjects. The definitions could be categorized in nine subdivisions of which four (n=43) referred to an original description. The other subdivisions were combinations of the original definitions (n=11), quantifications (n=4), computational (n=3), vaguely described (n=8) or not defined (n=6). Symptom limited maximal exercise tests were conducted to assess EOV, however the modes, protocols, software and data sampling were divers. Heterogeneity in the numerous definitions to identify EOV and the vaguely described assessment methods are hindering the evolution to a standardized uniformly accepted definition and technique to identify this abnormal breathing pattern. Unity in definition and international adopted assessment is warranted to strengthen its validity as a prognostic marker and could promote communication. It may facilitate clinical trials on pathophysiology and origin of EOV.

Prevalence and characterization of exercise oscillatory ventilation in apparently healthy individuals at variable risk for cardiovascular disease: A subanalysis of the EURO-EX trial

INTRODUCTION

There has been a greater appreciation of several variables obtained by cardiopulmonary exercise testing (CPX). Exercise oscillatory ventilation (EOV) is a CPX pattern that has gained recognition as an ominous marker of poor prognosis in cardiac patients. The purpose of the present study is to characterize whether such an abnormal ventilatory pattern may also be detected in apparently healthy subjects and determine its clinical significance.

METHODS

The study involved 510 subjects (mean age 60 ± 14 years; 49% male) with a broad cardiovascular (CV) risk factor profile who underwent CPX.

RESULTS

The population was divided into two groups according to the presence (17%) or absence of EOV. Subjects with EOV were significantly older and a higher percentage was female. Risk factor profile and medication use was significantly different between subgroups, indicating subjects with EOV had a worse CV risk factor profile and were prescribed CV-focused preventive medications at a significantly higher frequency. Subjects with EOV had comparatively poorer CPX performance and gas exchange phenotype. Multivariate binary logistic regression analysis found being female was the strongest predictor of EOV (odds ratio: 2.77, 95% confidence interval (CI): 1.66-4.61, p < 0.001). A diagnosis of diabetes (odds ratio: 2.40, 95% CI: 1.34-4.15.2, p < 0.001) added significant value for predicting EOV and was retained in the regression. The likelihood for EOV for subjects who were female and diagnosed with diabetes was 3.71 (95% CI 1.88-7.30, p < 0.001).

CONCLUSIONS

This is the first study to examine EOV prevalence and characterization in apparently healthy persons with results supporting an in-depth definition of abnormal exercise phenotypes.