Cardiac output during rest and exercise in desert heat

1. This study was undertaken to determine the accuracy of a modification of a single breath method for estimation of cardiac output. The technique incorporated a single rebreathing stage followed by a prolonged expiration. Cardiac output was determined from the O2 uptake and the instantaneous changes in O2 and CO2 in the expired gas during the prolonged expiration. 2. The mean values and the random errors (determined from the differences between pairs of estimates) of cardiac outputs in normal subjects at rest and exercise were 5.42 and ± 0.60 litres/min (2 sd, 60 pairs) and 14.1 and ±1.8 litres/min (40 pairs). 3. Larger random errors were obtained in a group of cardiac patients but, except in hypoxic patients, the mean values obtained by the single breath and the direct (Fick) methods were almost identical. 4. We conclude that our modification of the single breath method is simple to use and sufficiently reliable for use in humans both at rest and during steady states of light exercise.

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After effects of chronic hypoxia on cardiac output and muscle blood flow at rest and exercise

European Journal of Applied Physiology and Occupational Physiology ◽

10.1007/bf00422569 ◽

1984 ◽

Vol 53 (2) ◽

pp. 92-96 ◽

Cited By ~ 11

Author(s):

P. Cerretelli ◽

C. Marconi ◽

O. D�riaz ◽

D. Giezendanner

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Chronic Hypoxia ◽

Muscle Blood Flow ◽

After Effects ◽

Rest And Exercise

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Simultaneous Measurements of Cardiac Output during Rest and Exercise Using the Doppler and Nitrous Oxide Rebreathing Techniques

Clinical Science ◽

10.1042/cs065053pa ◽

1983 ◽

Vol 65 (3) ◽

pp. 53P-53P ◽

Cited By ~ 1

Author(s):

V.I. Iyawe ◽

N. Mehta ◽

A.R.C. Cummin ◽

K.B. Saunders

Keyword(s):

Nitrous Oxide ◽

Cardiac Output ◽

Simultaneous Measurements ◽

Rest And Exercise

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An open-circuit method for determining lung diffusing capacity during exercise: comparison to rebreathe

Journal of Applied Physiology ◽

10.1152/japplphysiol.00348.2005 ◽

2005 ◽

Vol 99 (5) ◽

pp. 1985-1991 ◽

Cited By ~ 26

Author(s):

Eric M. Snyder ◽

Bruce D. Johnson ◽

Kenneth C. Beck

Keyword(s):

Cardiac Output ◽

Breathing Pattern ◽

Open Circuit ◽

Diffusing Capacity ◽

External Work ◽

Capillary Recruitment ◽

Single Breath ◽

Circuit Technique ◽

Alveolar Capillary ◽

Rest And Exercise

To avoid limitations associated with the use of single-breath and rebreathe methods for assessing the lung diffusing capacity for carbon monoxide (DlCO) during exercise, we developed an open-circuit technique. This method does not require rebreathing or alterations in breathing pattern and can be performed with little cognition on the part of the patient. To determine how this technique compared with the traditional rebreathe (DlCO,RB) method, we performed both the open-circuit (DlCO,OC) and the DlCO,RB methods at rest and during exercise (25, 50, and 75% of peak work) in 11 healthy subjects [mean age = 34 yr (SD 11)]. Both DlCO,OC and DlCO,RB increased linearly with cardiac output and external work. There was a good correlation between DlCO,OC and DlCO,RB for rest and exercise (mean of individual r2 = 0.88, overall r2 = 0.69, slope = 0.97). DlCO,OC and DlCO,RB were similar at rest and during exercise [e.g., rest = 27.2 (SD 5.8) vs. 29.3 (SD 5.2), and 75% peak work = 44.0 (SD 7.0) vs. 41.2 ml·min−1·mmHg−1 (SD 6.7) for DlCO,OC vs. DlCO,RB]. The coefficient of variation for repeat measurements of DlCO,OC was 7.9% at rest and averaged 3.9% during exercise. These data suggest that the DlCO,OC method is a reproducible, well-tolerated alternative for determining DlCO, particularly during exercise. The method is linearly associated with cardiac output, suggesting increased alveolar-capillary recruitment, and values were similar to the traditional rebreathe method.

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Haemodynamic Variables during Repeated Exercise in Chronic Lung Disease

Clinical Science ◽

10.1042/cs0550485 ◽

1978 ◽

Vol 55 (5) ◽

pp. 485-490

Author(s):

F. Schrijen ◽

V. Ježek

Keyword(s):

Cardiac Output ◽

Arterial Pressure ◽

Right Ventricular ◽

Lung Disease ◽

Chronic Lung Disease ◽

Systemic Arterial Pressure ◽

Blood Gas ◽

Repeated Exercise ◽

Pulmonary Arterial ◽

Rest And Exercise

1. Pulmonary and systemic haemodynamics during repeated exercise were studied in 28 patients with chronic lung disease of various etiology, 16 of whom suffered from chronic bronchitis. They performed a moderate exercise repeated after a 20 min rest period. Ventilatory variables, blood gas tensions, cardiac output and vascular pressures (right ventricular end-diastolic, pulmonary arterial, wedge and systemic arterial) were measured at rest, during exercise and again at rest and during the same exercise. 2. Ventilation and blood gas tensions were similar during the two rest and exercise periods; there was, however, a slightly significant difference in oxygen consumption and hydrogen ion concentration between the first and the second exercise period. Pulmonary arterial and wedge pressures were lower during the second rest and exercise, right ventricular filling pressure was lower at rest, and systemic arterial pressure during the second exercise. Cardiac output and pulmonary vascular resistance were unchanged. 3. Changes in systemic arterial pressure were significantly different in a group of patients with arterial oxygen desaturation or perfusion defects, compared with those patients without such impairment.

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Rest and Exercise Cardiac Output and Diffusing Capacity Assessed By a Single Slow Exhalation of Methane, Acetylene, and Carbon Monoxide

CHEST Journal ◽

10.1378/chest.92.1.44 ◽

1987 ◽

Vol 92 (1) ◽

pp. 44-50 ◽

Cited By ~ 21

Author(s):

James E. Ramage ◽

R. Edward Coleman ◽

Neil R. MacIntyre

Keyword(s):

Carbon Monoxide ◽

Cardiac Output ◽

Diffusing Capacity ◽

Rest And Exercise

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An automated, indirect assessment of cardiac output during rest and exercise

Journal of Applied Physiology ◽

10.1152/jappl.1982.52.6.1493 ◽

1982 ◽

Vol 52 (6) ◽

pp. 1493-1497 ◽

Cited By ~ 31

Author(s):

J. H. Wilmore ◽

P. A. Farrell ◽

A. C. Norton ◽

R. W. Cote ◽

E. F. Coyle ◽

...

Keyword(s):

Cardiac Output ◽

Heart Catheterization ◽

Co2 Rebreathing ◽

Thermodilution Method ◽

Left Heart Catheterization ◽

Metabolic Measurement ◽

Artery Disease ◽

Power Outputs ◽

Clinical Exercise Testing ◽

Rest And Exercise

The present study describes a modification of the equilibration CO2-rebreathing technique for determining cardiac output (Q), utilizing the Beckman Metabolic Measurement Cart (MMC) to provide partial automation of the procedures described by Jones et al. (Clinical Exercise Testing. Philadelphia, PA: Saunders, 1975). Q was determined in six normal healthy males to establish the reliability of the technique at rest, and during exercise at power outputs of 49 and 98 W, or 300 and 600 kpm/min. An additional 11 patients, who were symptomatic for coronary artery disease and scheduled for right and left heart catheterization, were used in validating these procedures against Q determined by the thermodilution method. The automated CO2-rebreathing procedure was found to be reliable at rest and during exercise, and demonstrated a direct linear relationship with VO2 (r = 0.90). Also, this procedure correlated (r = 0.87) with the thermodilution method during supine rest, and both methods were quite consistent between trials within the same subject. It was concluded that the CO2-rebreathing procedure used in this study, as interfaced with the Beckman MMC, provides reasonable estimates of Q, both in patients during supine rest, and in normal healthy subjects at rest and during low to moderate levels of exercise.

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Determination of cardiac output using ensemble-averaged impedance cardiograms

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.1.200 ◽

1985 ◽

Vol 58 (1) ◽

pp. 200-205 ◽

Cited By ~ 94

Author(s):

M. Muzi ◽

T. J. Ebert ◽

F. E. Tristani ◽

D. C. Jeutter ◽

J. A. Barney ◽

...

Keyword(s):

Cardiac Output ◽

Intensive Care ◽

Stroke Volume ◽

Volume Index ◽

Breath Hold ◽

Ensemble Averaging ◽

Intensive Care Patients ◽

Impedance Data ◽

R Value ◽

Rest And Exercise

Although impedance cardiography provides safe and reliable noninvasive estimates of stroke volume in humans, its usefulness is limited by the necessity for subjects to be apneic and motionless. In an effort to circumvent this restriction we studied the validity of ensemble-averaging of impedance data in exercising normal subjects and in intensive-care patients. The correlation coefficient (r value) between 128 ensemble-averaged and standard hand-digitized determinations of stroke volume index from the same records taken during rest and exercise in six normal male subjects was +0.97 (P less than 0.001). The r value for ensemble-averaged stroke volume indices during free breathing and breath hold in the same subjects was +0.92 (P less than 0.001), suggesting that breath hold did not significantly affect the stroke volume estimation. In 14 freely breathing hospital intensive-care patients the r value between simultaneous thermodilution cardiac output readings and ensemble-averaged impedance determinations was +0.87 (P less than 0.01). The results indicate that ensemble-averaging of transthoracic impedance data provides waveforms from which reliable estimates of cardiac output can be made during normal respiration in healthy human subjects at rest and exercise and in critically ill patients.

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