Comparison of Two Rebreathing Methods for the Determination of Mixed Venous Partial Pressure of Carbon Dioxide during Exercise

Heigenhauser, George J. F.; Jones, Norman L.

doi:10.1042/cs0560433

Cited by 19 publications

(7 citation statements)

References 18 publications

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“…This is similar to what has been described in adults. 6,13,20 This suggests that in children, as in adults, either the equilibrium method with downstream correction or the exponential method can be used when calculating Pv CO 2 .…”

Section: Discussionmentioning

confidence: 99%

“…6 In a later study from the same group, 20 values fell closer to the line of identity, with a slope of 0.975 and an intercept of 1.46. Their data encompassed a much broader range than did ours, and our values can be superimposed on their concordance plot.…”

Section: Pv Comentioning

confidence: 99%

“…5 However, this correction does not appear to be necessary using the exponential method. 6 The reason for this downstream correction with the equilibrium method remains unclear, but it is likely related to the absence of outward movement of CO 2 from the blood to the rebreathing bag during this method. 6 In children, there has been some controversy over whether downstream correction is necessary when using the equilibrium method to determine Q .…”

mentioning

confidence: 99%

“…6 The reason for this downstream correction with the equilibrium method remains unclear, but it is likely related to the absence of outward movement of CO 2 from the blood to the rebreathing bag during this method. 6 In children, there has been some controversy over whether downstream correction is necessary when using the equilibrium method to determine Q . Godfrey and coworkers 7 found that the overestimation of Pv CO 2 that had been seen in adults 4,8,9 was also present in children, 7 but Godfrey 10 suggests that the use of the downstream correction in children gives an overly high estimate of Q , so that the uncorrected plateau value for Pv CO 2 should be used.…”

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confidence: 99%

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Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children

Jacob¹,

Hornby

Lands

1997

Chest

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Study objectives: Cardiac output (Q ) can be estimated noninvasively during exercise by employing CO 2 -rebreathing techniques (equilibrium and exponential) to estimate the oxygenated mixed venous PCO 2 (Pv CO 2 ). It has been found in adults and children that the equilibrium method underestimates Q as a result of overestimation of Pv CO 2 , unless Pv CO 2 is "downstream corrected." In adults, it has been found that the exponential method does not require downstream correction and yields values similar to those obtained by the equilibrium method with downstream correction. The objectives of this study were as follows: to test whether the exponential method gives similar results to the equilibrium method with downstream correction in children; to verify that downstream correction is required in children; and to test whether a single equation could be used in adults and children to predict Q from oxygen consumption (V O 2 ). Design: Descriptive. Setting: Exercise laboratory of a university hospital. Participants: 23 children (16 boys, 7 girls) with a mean age of 11.0؎1.9 years (7.1 to 13.9 years), and 12 adults (7 men, 5 women) with a mean age of 33.6؎7.2 years (24 to 48 years). Interventions: While performing steady-state exercise on an ergometer, Pv CO 2 was determined in 14 children using both the equilibrium and exponential methods, and in all other subjects using the equilibrium method alone. Measurements and results: For the 14 children who underwent testing by both the equilibrium and exponential methods, the uncorrected equilibrium Pv CO 2 was significantly different from both the corrected Pv CO 2 and the exponential Pv CO 2 . We found a strong relationship between Q (L/min), calculated using the downstream corrected values of Pv CO 2 , and V O 2 (L/min) (r 2 ‫,)59.0؍‬ and this relationship was similar to that obtained by dye dilution in other studies. When weight was included, it was determined that one equation could be used for children and adults: Q (L/min)‫؍‬ 1.42؉5.80 • V O 2 (L/min)؉0.06 • wt (kg), r 2 ‫,79.0؍‬ SEY‫.76.0؍‬ Conclusions: CO 2 -rebreathing techniques can be used to determine Q in children; the exponential method gives values that are similar to the equilibrium method with the downstream correction; and one prediction can be used for Q in adults and children.(CHEST 1997; 111:474-80)Key words: equilibrium rebreathing method; exercise; exponential rebreathing method Abbreviations: Pe qCO 2 ϭend-tidal Pco 2 at equilibrium; PetCO 2 ϭend-tidal Pco 2 ; Pv CO 2 ϭoxygenated mixed venous Pco 2 ; Pv co 2 eq,corrϭcorrected equilibrium Pv CO 2 ; Pv CO 2 expϭexponential Pv CO 2 ; Q ϭcardiac output; SEϭstandard error; V co 2 ϭcarbon dioxide production; V o 2 ϭoxygen consumption

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Section: Discussionmentioning

confidence: 99%

Section: Pv Comentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children

Jacob¹,

Hornby

Lands

1997

Chest

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“…The alternative, equilibrium method, has been thought to be more reliable than the exponential method [9], but recently the application of computer analysis to the exponential method has im proved its precision [13]. A number of methods have been proposed for the derivation of the asymptote of the exponential rise in PCO2 in the rebreathing system.…”

Section: Methodsmentioning

confidence: 99%

Estimation of Cardiac Output by C0(2) Rebreathing during Incremental Exercise in Patients with Coronary Artery Disease

Campbell¹,

Mckelvie²,

Heigenhauser³

et al. 1989

Am J Noninvas Cardiol

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In 9 patients with stable coronary artery disease, measurements were made during a progressive incremental maximum exercise test of O(2) intake (VO(2)), CO(2) output (VCO(2)), mixed venous PCO(2) by an exponential rebreathing method, and end-tidal PCO(2) (PETCO(2)) to estimate arterial PCO(2) (PaCO(2)). By applying the Fick principle to CO2, these measurements were used to derive cardiac output at several incremental work loads. Each subject underwent two incremental exercise studies to establish the reproducibility of the technique, and also a steady state exercise study to compare steady state responses with unsteady state incremental exercise. The results were also compared to those previously obtained in healthy subjects. PvCO(2) showed a curvilinear increase with increasing VCO(2) with only a small intersubject variation. Cardiac output-oxygen uptake relationships (Q/VO(2)) were similar in the two incremental studies (intercepts 6.27 and 6.641/min; slopes 4.82 and 4.58 1/min), and also similar to that obtained previously in healthy subjects (intercept 6.441/min; slope 4.71 1/min). Low calculated values for cardiac output were obtained at high exercise levels during the incremental test in those subjects in whom PETCO(2) fell at the highest work loads. This effect could be corrected for by using a PETCO(2) obtained 1 min prior to rebreathing, suggesting that the low values of Q were an artifact due to a transient decrease in PaCO(2) secondary to hyperventilation. At any given VO(2) or VCO2, PvCO(2) and Q were the same in both steady state and unsteady state incremental exercise. The exponential CO(2) rebreathing method may be reliably applied to incremental exercise testing to evaluate the cardiac output responses to exercise in patients with cardiac disease.

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Cardiac effects of short term arm crank training in paraplegics: echocardiographic evidence

Davis

Shephard

Leenen

1987

Europ. J. Appl. Physiol.

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The cardiac responses of male paraplegics to upper-body endurance training have been studied by M-mode echocardiography and CO2-rebreathing determination of cardiac output. Data for nine exercised subjects are compared with 5 controls. After 16 weeks of arm ergometer exercise, heart rates of trained individuals were 9 bt X min-1 lower during isometric handgrip effort (30% of MVC for 3 min), with a substantial decrease of rate pressure product (20%; p less than 0.05). In contrast (possibly because of greater anticipation) the control subjects developed a larger rate-pressure product with repetition of the standard isometric effort. Despite a significant increase of VO2 peak (19% and 31% after 8 and 16 weeks, respectively; p less than 0.05), echocardiographic LV mass, dimensions and indices of LV performance were unchanged by training, either at rest or during the isometric handgrip. Stroke volumes were significantly increased by 12-16% after training, both in isometric and in rhythmic work; at the highest intensity of arm ergometry, there was also a suggestion of increased cardiac output. We conclude that a short period of arm training is insufficient to induce cardiac hypertrophy, an increase of stroke volume with a decreased rate-pressure product but no change in echocardiographic indices of LV performance implies an improved myocardial efficiency. Possible explanations are a greater strength of the trained arms, and some increase of pre-loading (due to an increase of venous tone and more effective operation of the muscle pump after training).

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Comparison of Two Rebreathing Methods for the Determination of Mixed Venous Partial Pressure of Carbon Dioxide during Exercise

Cited by 19 publications

References 18 publications

Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children

Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children

Estimation of Cardiac Output by C0(2) Rebreathing during Incremental Exercise in Patients with Coronary Artery Disease

Cardiac effects of short term arm crank training in paraplegics: echocardiographic evidence

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