Spurious Hb mass increases following exercise

The effect of posture and exercise on blood CO kinetics during the optimized carbon monoxide rebreathing procedure

An indispensable precondition for the determination of hemoglobin mass (Hbmass) and blood volume by CO rebreathing is complete mixing of CO in the blood. The aim of this study was to demonstrate the kinetics of CO in capillary and venous blood in different body positions and during moderate exercise. Six young subjects (4 male, 2 female) performed three 2-min CO rebreathing tests in seated (SEA) & supine (SUP) positions as well as during moderate exercise (EX) on a bicycle ergometer. Before, during, and until 15 min after CO rebreathing cubital venous and capillary blood samples were collected simultaneously and COHb% was determined. COHb% kinetics were significantly slower in SEA than in SUP or EX. Identical COHb% in capillary and venous blood were reached in SEA after 5.0 ± 2.3 min, in SUP after 3.2 ± 1.3 min and in EX after 1.9 ± 1.2 min (EX vs. SEA p < .01, SUP vs. SEA p < .05). After 7th min, Hbmass did not differ between the resting positions (capillary: SEA 766 ± 217 g, SUP 761 ± 227 g; venous: SEA 759 ± 224 g, SUP 744 ± 207 g). Under exercise, however, a higher Hbmass (p < .05) was determined (capillary: 823 ± 221 g, venous: 804 ± 226 g). In blood, the CO mixing time in the supine position is significantly shorter than in the seated position. By the 6th minute complete mixing is achieved in either position giving similar Hbmass determinations. CO-rebreathing under exercise conditions, however, leads to ∼7% higher Hbmass values.

Epidemiological, biological and clinical update on exercise-induced hemolysis

Exercise-induced hemolysis can be conventionally defined as rupture and destruction of erythrocytes during physical exercise. The currently available epidemiologic information attests that a substantial degree of exercise-induced hemolysis is commonplace after short-, medium-, long- and ultra-long distance running, as reflected by significant decrease of serum or plasma haptoglobin and significant increase of plasma concentration (or overall blood content) of free hemoglobin. This paraphysiological intravascular hemolysis is typically mild (average variations of hemolysis biomarkers are usually comprised between 1.2- and 1.8-fold), almost self-limiting (completely resolving within 24-48 hours), with severity depending on athlete population, analytical technique used for detecting intravascular hemolysis, as well as on number, frequency and intensity of ground contacts, but not on running technique. Additional lines of evidence support the notion that both osmotic fragility and membrane structure of erythrocytes are considerably modified during endurance exercise. This fact goes hand in hand with findings that erythrocyte lifespan in runners is approximately 40% shorter than in sedentary controls. Direct mechanical injury caused by forceful ground contacts, repeated muscle contractile activity or vasoconstriction in internal organs are three potential sources of exercise-induced hemolysis, whilst metabolic abnormalities developing while exercising (e.g., hyperthermia, dehydration, hypotonic shock, hypoxia, lactic acidosis, shear stress, oxidative damage, proteolysis, increased concentration of catecholamines and lysolecithin) may actively contribute to trigger, accelerate or amplify this phenomenon. Although no systematic evidence is available, it seems also reasonable to hypothesize that patients bearing erythrocyte disorders may be particularly vulnerable to developing exercise-induced hemolysis.

Haemoglobin mass alterations in healthy humans following four-day head-down tilt bed rest

NEW FINDINGS

What is the central question of this study? Is haemoglobin mass (Hbmass) decreased following 4 days of head-down tilt bed rest (HDTBR), and does increased red blood cell (RBC) destruction mediate this adaptation? What is the main finding and its importance? Haemoglobin mass was increased immediately following HDTBR, before decreasing below baseline 5 days after return to normal living conditions. The transient increase in Hbmass might be the result of decreased RBC destruction, but it is also possible that spleen contraction after HDTBR contributed to this adaptation. Our data suggest that the decreased Hbmass 5 days following HDTBR resulted from decreased RBC production, not increased RBC destruction. Rapid decreases in haemoglobin mass (Hbmass) have been reported in healthy humans following spaceflight and descent from high altitude. It has been proposed that a selective increase in the destruction of young red blood cells (RBCs) mediates these decreases, but conclusive evidence demonstrating neocytolysis in humans is lacking. Based on the proposed triggers and time course of adaptation during spaceflight, we hypothesized that Hbmass would be reduced after 4 days of -6 deg head-down tilt bed rest (HDTBR) and that this would be associated with evidence for increased RBC destruction. We assessed Hbmass in seven healthy, recreationally active men before (PRE), 5 h after (POST) and 5 days after (POST5) 4 days of HDTBR. The concentration of erythropoietin decreased from 7.1 ± 1.8 mIU ml(-1) at PRE to 5.2 ± 2.8 mIU ml(-1) at POST (mean ± SD; P = 0.028). Contrary to our hypothesis, Hbmass was increased from 817 ± 135 g at PRE to 849 ± 141 g at POST (P = 0.014) before decreasing below PRE to 789 ± 139 g at POST5 (P = 0.027). From PRE to POST, the concentration of haptoglobin increased from 0.54 ± 0.32 to 0.68 ± 0.28 g l(-1) (P = 0.013) and the concentration of bilirubin decreased from 0.50 ± 0.24 to 0.32 ± 0.11 mg dl(-1) (P = 0.054), suggesting that decreased RBC destruction might have contributed to the increased Hbmass. However, it is possible that spleen contraction following HDTBR also played a role in the increase in Hbmass at POST, but as the transient increase in Hbmass was unexpected, we did not collect data that would provide direct evidence for or against spleen contraction. From PRE to POST5, the concentration of soluble transferrin receptor decreased from 20.7 ± 3.9 to 17.1 ± 3.3 nmol l(-1) (P = 0.018) but the concentrations of ferritin, haptoglobin and bilirubin were not significantly altered, suggesting that the decrease in Hbmass was mediated by decreased RBC production rather than increased RBC destruction. Peak oxygen uptake decreased by 0.31 ± 0.16 l min(-1) from PRE to POST (P = 2 × 10(-4) ) but was not significantly altered at POST5 compared with PRE. Overall, these findings indicate that 4 days of HDTBR does not increase RBC destruction and that re-examination of the time course and mechanisms of Hbmass alterations following short-term spaceflight and simulated microgravity is warranted.

'Blood doping' from Armstrong to prehabilitation: manipulation of blood to improve performance in athletes and physiological reserve in patients

Haemoglobin is the blood’s oxygen carrying pigment and is encapsulated in red blood corpuscles. The concentration of haemoglobin in blood is dependent on both its total mass in the circulation (tHb-mass) and the total plasma volume in which it is suspended. Aerobic capacity is defined as the maximum amount of oxygen that can be consumed by the body per unit time and is one measure of physical fitness. Observations in athletes who have undergone blood doping or manipulation have revealed a closer relationship between physical fitness (aerobic capacity) and total haemoglobin mass (tHb-mass) than with haemoglobin concentration ([Hb]). Anaemia is defined by the World Health Organisation (WHO) as a haemoglobin concentration of <130 g/L for men and <120 g/L for women. Perioperative anaemia is a common problem and is associated with increased mortality and morbidity following surgery. Aerobic capacity is also associated with outcome following major surgery, with less fit patients having a higher incidence of mortality and morbidity after surgery. Taken together, these observations suggest that targeted preoperative elevation of tHb-mass may raise aerobic capacity both directly and indirectly (by augmenting preoperative exercise initiatives- ‘prehabilitation’) and thus improve postoperative outcome. This notion in turn raises a number of questions. Which measure ([Hb] or tHb-mass) has the most value for the description of oxygen carrying capacity? Which measure has the most utility for targeting therapies to manipulate haemoglobin levels? Do the newer agents being used for blood manipulation (to increase tHb-mass) in elite sport have utility in the clinical environment? This review explores the literature relating to blood manipulation in elite sport as well as the relationship between perioperative anaemia, physical fitness and outcome following surgery, and suggests some avenues for exploring this area further.

The impact of triathlon training and racing on athletes' general health

Although the sport of triathlon provides an opportunity to research the effect of multi-disciplinary exercise on health across the lifespan, much remains to be done. The literature has failed to consistently or adequately report subject age group, sex, ability level, and/or event-distance specialization. The demands of training and racing are relatively unquantified. Multiple definitions and reporting methods for injury and illness have been implemented. In general, risk factors for maladaptation have not been well-described. The data thus far collected indicate that the sport of triathlon is relatively safe for the well-prepared, well-supplied athlete. Most injuries 'causing cessation or reduction of training or seeking of medical aid' are not serious. However, as the extent to which they recur may be high and is undocumented, injury outcome is unclear. The sudden death rate for competition is 1.5 (0.9-2.5) [mostly swim-related] occurrences for every 100,000 participations. The sudden death rate is unknown for training, although stroke risk may be increased, in the long-term, in genetically susceptible athletes. During heavy training and up to 5 days post-competition, host protection against pathogens may also be compromised. The incidence of illness seems low, but its outcome is unclear. More prospective investigation of the immunological, oxidative stress-related and cardiovascular effects of triathlon training and competition is warranted. Training diaries may prove to be a promising method of monitoring negative adaptation and its potential risk factors. More longitudinal, medical-tent-based studies of the aetiology and treatment demands of race-related injury and illness are needed.

The carbon monoxide re-breathing method can underestimate Hbmass due to incomplete blood mixing

PURPOSE

Hemoglobin mass (Hbmass) is commonly assessed using the CO re-breathing method with the subject in the seated position. This may lead to an underestimation of Hbmass as blood in lower extremity veins while seated may not be tagged with carbon monoxide (CO) during the re-breathing period.

METHODS

To test this hypothesis, CO re-breathing was performed on four occasions in nine male subjects, twice in the seated position and twice in combination with light cycle ergometer exercise (1 W/kg body-weight) intending to accelerate blood circulation and thereby potentially allowing for a better distribution of CO throughout the circulation as compared to in the seated position. Blood samples were drawn from an antecubital vein and the saphenous magna vein following the re-breathing procedure.

RESULTS

In the seated position, CO re-breathing increased the percent carboxyhemoglobin (%HbCO) in the antecubital vein to 8.9 % (7.8-10.7) [median (min-max)], but less (P = 0.017) in the saphenous magna vein [7.8 % (5.0-9.9)]. With exercise, no differences in %HbCO were observed between sampling sites. As a result, CO re-breathing in combination with exercise revealed a ~3 % higher (P = 0.008) Hbmass, i.e., 936 g (757-1,018) as compared to 908 g (718-940) at seated rest.

CONCLUSION

This study suggests an uneven distribution of CO in the circulation if the CO re-breathing procedure is performed at rest in the seated position and therefore can underestimate Hbmass.