Errors of measurement for blood volume parameters: a meta-analysis

The volume of red blood cells (V(RBC)) is used routinely in the diagnostic workup of polycythemia, in assessing the efficacy of erythropoietin administration, and to study factors affecting oxygen transport. However, errors of various methods of measurement of V(RBC) and related parameters are not well characterized. We meta-analyzed 346 estimates of error of measurement of V(RBC) for techniques based on Evans blue (V(RBC,Evans)), 51chromium-labeled red blood cells (V(RBC,51Cr)), and carbon monoxide (CO) rebreathing (V(RBC,CO)), as well as hemoglobin mass with the carbon-monoxide method (M(Hb,CO)), in athletes and active and inactive subjects undergoing various experimental and control treatments lasting minutes to months. Subject characteristics and experimental treatments had little effect on error of measurement, but measures with the smallest error showed some increase in error with increasing time between trials. Adjusted to 1 day between trials and expressed as coefficients of variation, mean errors for M(Hb,CO) (2.2%; 90% confidence interval 1.4-3.5%) and V(RBC,51Cr) (2.8%; 2.4-3.2%) were much less than those for V(RBC,Evans) (6.7%; 4.9-9.4%) and V(RBC,CO) (6.7%; 3.4-14%). Most of the error of V(RBC,Evans) was due to error in measurement of volume of plasma via Evans blue dye (6.0%; 4.5-7.8%), which is the basis of V(RBC,Evans). Most of the error in V(RBC,CO) was due to estimates from laboratories with a relatively large error in M(Hb,CO), the basis of V(RBC,CO). V(RBC,51Cr) and M(Hb,CO) are the best measures for research on blood-related changes in oxygen transport. With care, V(RBC,Evans) is suitable for clinical applications of blood-volume measurement.

Physiological and performance responses to tournament wrestling

PURPOSE

The purpose of this study was to investigate the physiological and performance responses to a simulated freestyle wrestling tournament after typical weight loss techniques used by amateur wrestlers.

METHODS

Twelve Division I collegiate wrestlers (mean +/- SD;19.33 +/- 1.16 yr) lost 6% of total body weight during the week before a simulated, 2-d freestyle wrestling tournament. A battery of tests was performed at baseline and before and immediately after each individual match of the tournament. The test battery included assessment for body composition, reaction/movement time, lower and upper body power and isokinetic strength, and a venous blood sample.

RESULTS

Lower body power and upper body isometric strength were significantly reduced as the tournament progressed (P < or = 0.05). Significant elevations in testosterone, cortisol, and lactate were observed after each match (P < or = 0.05). However, there was a significant reduction (P < or = 0.05) in resting testosterone values in the later matches. Norepinephrine increased significantly (P < or = 0.05) after each match, whereas epinephrine increased significantly (P < or = 0.05) after each match except the last match of each day. Plasma osmolality was consistently higher than normal values at all times including baseline, with significant increases observed after each match (P < or = 0.05).

CONCLUSIONS

Tournament wrestling augments the physiological and performance decrements of weight loss and its impact is progressive over 2 d of competition. The combined effects of these stresses may ultimately be reflected in a wrestler's ability to maintain physical performance throughout a tournament.

Van Beaumont's formula is valid during haemodialysis. Spectrophotometric determination of body circulating haemoglobin

Van Beaumont's formula is a convenient method to calculate changes in plasma volume from changes in haematocrit. The calculation is based on the assumption of a constant body red-cell volume. In order to evaluate the validity of this assumption during isovolaemic haemodialysis, we measured body circulating haemoglobin, blood volume and plasma volume by carbon monoxide dilution. No change in body circulating haemoglobin or plasma volume occurred by either method. Therefore, we conclude that van Beaumont's formula is valid during isovolaemic haemodialysis.

Effect of changes in cardiac autonomic balance on blood pressure regulation in man

The role of cardiac autonomic balance in fitness-related differences in blood pressure regulation was evaluated by comparing the cardiovascular responses to lower body negative pressure (LBNP) in 10 trained and 10 untrained men. Cardiac autonomic balance was quantified as the ratio of resting heart rate to intrinsic heart rate, and was significantly lower in the trained subjects (0.68 +/- 0.03) than the untrained subjects (0.81 +/- 0.03) indicating a greater parasympathetic dominance at rest in the trained subjects. Arterial pressure decreased significantly more during LBNP in the trained subjects and was due to lower chronotropic and vasoconstrictor responses in these trained subjects. 'Cardiac autonomic balance' was equilibrated between the groups by partial parasympathetic blockade with atropine sulfate in the trained subjects and partial sympathetic blockade with metoprolol tartrate in the untrained subjects. Equilibration of cardiac autonomic balance eliminated the group differences in blood pressure maintenance, and chronotropic and vasoconstrictor responsiveness during LBNP. It was hypothesized that the elevated tone of parasympathetic control of the heart rate of the trained subjects resulted in an attenuation of blood pressure regulation.

Sustained visual attention and carbon monoxide: elimination of adaptation effects

Eighteen subjects performed a 1-h visual vigilance task, once during a control condition (filtered air) and once during an experimental condition (CO). The COHb level was elevated to 5% utilizing a bolus maintenance technique which raised the COHb level rapidly so that there would be no possibility of an adaptation occurring prior to vigilance testing. Physiological measurements included heart rate, blood pressure, and ventilation. Neither vigilance performance nor the physiological variables was statistically affected by the 5% COHb level. Subjects identified a significantly (p> 0.05) higher percentage of signals with the high frequency of signal presentation as compared to the low frequency under both filtered air and the 5% COHb level. Signal detection improved in 12 subjects during minutes 0-15, while 10 subjects showed improvement during minutes 31-45 with an elevated COHb level. The subjective questionnaire indicated that CO significantly (p < 0.01) decreased the subjects' confidence concerning their performance on the vigilance task, as well as causing significant (p < 0.05) irritation of the eyes and throat.

Blood biochemical alterations during recovery from competitive marathon running

The occurrence of possible prolonged alterations in plasma levels of cortisol, epinephrine, norepinephrine, selected energy metabolites, and water and electrolyte balance was assessed in six highly trained male marathon runners by measuring blood biochemical constituents on the 10th day before and for the three days following the running of a marathon. Post-race changes in hemoglobin, hematocrit, and protein levels indicated that a hemodilution had occurred, possibly as a result of elevated sodium levels. Epinephrine remained elevated until the second day. Cortisol was depressed on the first and third post-race days while variable levels were observed on the second day. No prolonged alterations were noted in norepinephrine, FFA, glycerol, triglycerides, glucose, lactate, and pyruvate.

Acute blood biochemical alterations in response to marathon running

Adrenal-sympathico function, blood carbohydrates and lipids, and water and electrolyte balance were studied in six highly trained male marathon runners prior to and after running a marathon (26.2 miles; 42.2 km) and on control days corresponding to the above times. Fluid intake was not sufficient to maintain body weight, the runners losing approximately 2.8 kg. Estimated plasma volume losses (161 ml, 4.4%) indicated that most of the fluid loss was extravascular. Tre rose an average 2.4 degrees C and a significant negative correlation between running time and rise in Tre was observed. Glucose, fatty acids, glycerol, hemoglobin, and plasma proteins were significantly elevated after the race. Small but statistically significant increments in lactate and pyruvate were also observed. Alterations in adrenal-sympathico function were indicated by increased levels of cortisol, epinephrine, and norepinephrine.