Comparison of cardiac output determined by different rebreathing methods at rest and at peak exercise

Jakovljevic, Djordje G.; Nunan, David; Hodges, Lynette; Sandercock, Gavin; Brodie, David A.

doi:10.1007/s00421-007-0631-4

Cited by 43 publications

(32 citation statements)

References 27 publications

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“…This system was also used to measure CO during the final 7 min of exercise at each intensity on testing day 3, but at 2 time-points only (30 s and 240 s). CO was measured using an inert gas rebreathing technique as previously used during similar exercise testing procedures (Jakovljevic et al 2008;MacAnaney et al 2011a). Stroke volume was calculated as CO/HR.…”

Section: Measurementsmentioning

confidence: 99%

Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

Ananey

O’Shea

Warmington

et al. 2012

Appl. Physiol. Nutr. Metab.

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Supervised exercise (SE) in patients with type 2 diabetes improves oxygen uptake kinetics at the onset of exercise. Maintenance of these improvements, however, has not been examined when supervision is removed. We explored if potential improvements in oxygen uptake kinetics following a 12-week SE that combined aerobic and resistance training were maintained after a subsequent 12-week unsupervised exercise (UE). The involvement of cardiac output (CO) in these improvements was also tested. Nineteen volunteers with type 2 diabetes were recruited. Oxygen uptake kinetics and CO (inert gas rebreathing) responses to constant-load cycling at 50% ventilatory threshold (VT), 80% VT, and mid-point between VT and peak workload (50% Δ) were examined at baseline (on 2 occasions) and following each 12-week training period. Participants decided to exercise at a local gymnasium during the UE. Thirteen subjects completed all the interventions. The time constant of phase 2 of oxygen uptake was significantly faster (p < 0.05) post-SE and post-UE compared with baseline at 50% VT (17.3 ± 10.7 s and 17.5 ± 5.9 s vs. 29.9 ± 10.7 s), 80% VT (18.9 ± 4.7 and 20.9 ± 8.4 vs. 34.3 ± 12.7s), and 50% Δ (20.4 ± 8.2 s and 20.2 ± 6.0 s vs. 27.6 ± 3.7 s). SE also induced faster heart rate kinetics at all 3 intensities and a larger increase in CO at 30 s in relation to 240 s at 80% VT; and these responses were maintained post-UE. Unsupervised exercise maintained benefits in oxygen uptake kinetics obtained during a supervised exercise in subjects with diabetes, and these benefits were associated with a faster dynamic response of heart rate after training.

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Section: Measurementsmentioning

confidence: 99%

Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

Ananey

O’Shea

Warmington

et al. 2012

Appl. Physiol. Nutr. Metab.

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“…A number of non-invasive techniques have therefore been evaluated in this setting and include methods employing gas rebreathing (Jakovljevic et al 2008), the modelflow method (Sugawara et al 2003) and bioimpedance cardiography (Richard et al 2001). The latter is based upon the principle that assessment of electrical conductance properties across the thorax can be used to calculate aortic blood flow (Kubicek et al 1966).…”

Section: Introductionmentioning

confidence: 99%

Application of bioreactance for cardiac output assessment during exercise in healthy individuals

Elliott

Hull²,

Nunan

et al. 2010

Eur J Appl Physiol

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In patients with cardiac failure, bioreactance-based cardiac output (CO) monitoring provides a valid non-invasive method for assessing cardiac performance during exercise. The purpose of this study was to evaluate the efficacy of this technique during strenuous exercise in healthy, trained individuals. Fourteen recreational cyclists, mean (SD) age of 34 (8) years and relative peak oxygen uptake of (VO(2)) 56 (6) ml kg(-1) min(-1), underwent incremental maximal exercise testing, whilst CO was recorded continuously using a novel bioreactance-based device (CO(bio)). The CO(bio) was evaluated against relationship with VO(2), theoretical calculation of arterial-venous oxygen difference (C(a - v) O(2)) and level of agreement with an inert gas rebreathing method (CO(rb)) using a Bland-Altman plot. Bioreactance-based CO measurement was practical and straightforward in application, although there was intermittent loss of electrocardiograph signal at high-intensity exercise. At rest and during exercise, CO(bio) was strongly correlated with VO(2) (r = 0.84; P < 0.001), however, there was evidence of systematic bias with CO(bio) providing lower values than CO(rb); mean bias (limits of agreement) -19% (14.6 to -53%). Likewise, calculated (C(a - v) O(2)) was greater when determined using CO(bio) than CO(rb) (P < 0.001), although both devices provided values in excess of those reported in invasive studies. Bioreactance-based determination of CO provides a pragmatic approach to the continuous assessment of cardiac performance during strenuous exercise in trained individuals. Our findings, however, suggest that further work is needed to refine the key measurement determinants of CO using this device to improve measurement accuracy in this setting.

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“…5 Alternatively, non-invasive techniques such as carbon dioxide or inert gas rebreathing can be used to measure cardiac function. Innocor (Innovision, Odense, Denmark), a system using inert gas rebreathing, proved to be a reliable noninvasive tool to measure CO at rest [6][7][8] and during exercise in AB, 8 and showed consistency with gold standard methods. [9][10][11] In addition, the Innocor device can estimate pulmonary shunts and evaluate the degree of gas mixing.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, CO might be more precisely assessed by this method than by carbon dioxide rebreathing. 6 Despite being a simple and comfortable measurement procedure, a critical requirement to obtain valid measurements has been reported as being the ability to rebreathe 40% of the predicted vital capacity during four consecutive breaths within 20 s to assure complete alveolar mixing of the test gases. 12 As TP is associated with a number of pulmonaryrelated impairments, including compromised lung function, resulting partly from the low active respiratory muscle mass, 13 feasibility of CO measurement with Innocor needs to be evaluated in TP.…”

Section: Introductionmentioning

confidence: 99%

Reliability of non-invasive cardiac output measurement in individuals with tetraplegia

et al. 2010

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Study design: The study is conducted on the basis of comparative-repeated measures. Objectives: The objective of this study is to assess the reliability of non-invasive cardiac output (CO) measurements in individuals with tetraplegia (TP) at rest and during exercise using Innocor, and to test the hypothesis that CO measurements are less reliable in TP than in able-bodied (AB) individuals. Setting: Ambulatory volunteers, Switzerland. Methods: Nine male motor-complete TP (C5-C7) and nine pair-matched AB performed repeated CO measurements at rest and during submaximal arm-crank and wheelchair exercises in four different test sessions. Within-and between-day reliabilities were compared between TP and AB. Results: Mean differences between measurements at rest (TP vs AB, within-day: 0.1±0.5 vs 0.2 ± 0.6 l min À1 , between-day: À0.7 ± 0.6 vs À0.1 ± 0.8 l min À1 ), during arm-crank (TP vs AB, withinday: 0.1±0.9 vs 0.5±0.7 l min À1 , between-day: À0.3±1.1 vs 0.0±1.1 l min À1 ) and wheelchair exercises (TP vs AB, within-day: 0.3 ± 1.2 vs -0.1 ± 0.8 l min À1 , between-day: 0.1 ± 1.1 vs 0.5±0.9 l min À1 ) were not significantly different between TP and AB (all P40.05). Coefficients of variation in TP (within-day, rest: 6.8%, arm-crank: 9.6% and wheelchair: 10.8%; between-day, rest: 11.9%, arm-crank: 11.2% and wheelchair: 10.3%) and in AB (within-day, rest: 7.7%, arm crank: 6.8% and wheelchair: 6.0%; between-day, rest: 9.2%, arm crank: 8.5% and wheelchair: 8.0%) indicated acceptable reliability. Conclusion: In contrast to our hypothesis, we found non-invasive CO measurements using Innocor to be as reliable in TP as they are in AB. Consequently, Innocor can be recommended for repeated assessments of CO in TP within routine diagnostics or for evaluation of training progress.

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Comparison of cardiac output determined by different rebreathing methods at rest and at peak exercise

Cited by 43 publications

References 27 publications

Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

Application of bioreactance for cardiac output assessment during exercise in healthy individuals

Reliability of non-invasive cardiac output measurement in individuals with tetraplegia

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