Prevalence of sickle cell trait in athletic West African population.
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Africa, Western↗
Biomedical subjects
R J Zeballos
Publications and source records attributed to R J Zeballos.
Exercise and hypoxia increase sickling in venous blood from an exercising limb in individuals with sickle cell trait.
PURPOSE: The association between sickle cell trait (SCT) and complications related to exercise may be explained if exercise-induced sickling interferes with capillary blood flow and causes tissue ischemia and functional abnormalities. To test this hypothesis, we measured sickling and blood gas values in venous and arterial blood of an exercising limb in subjects with SCT and in controls. SUBJECTS AND METHODS: The study consisted of 15 subjects with hemoglobin AS (SCT group) and 15 subjects with hemoglobin AA (control group). Each performed two maximal arm crank exercise tests, one at 1,270 meters and one at simulated 4,000 meters. RESULTS: At 1,270 meters, axillary venous sickling increased significantly (p less than 0.05) from (mean +/- SD) 1.0 +/- 1.0% at rest to 2.3 +/- 2.6% during peak exercise. At simulated 4,000 meters, sickling increased significantly (p less than 0.001) from 1.5 +/- 1.2% to 8.5 +/- 7.1%. A wide range of sickling during peak exercise was observed (1% to 25%). One minute after exercise at simulated 4,000 meters, venous sickling remained elevated (7.2 +/- 7.8%) despite high levels of oxygen saturation. Arterial sickling (less than 1%) was present in only two subjects. There was no significant difference in oxygen consumption (29.4 +/- 3 versus 30.7 +/- 4 mL/kg/minute) between the subjects with SCT and the controls, nor was there a correlation between exercise performance and sickling (r less than 0.2). CONCLUSION: We conclude that exercise at 1,270 meters slightly, albeit significantly, increased sickling in blood from an exercising limb and that simulated 4,000 meters dramatically potentiated this effect. Sickling in the effluent blood of an exercising limb does not appear to measurably affect overall maximal arm crank exercise performance.
Adult↗
Cardiopulmonary and gas exchange responses to acute strenuous exercise at 1,270 meters in sickle cell trait.
The impact of strenuous exercise and environmental hypoxia on sickle cell trait (SCT) remains controversial. To determine if these factors induce cardiopulmonary and gas exchange abnormalities in SCT, healthy, young black male volunteers, 25 with SCT (HbAS) and 16 control subjects (HbAA), were evaluated during incremental and steady-state exercise tests using a cycle ergometer at 1,270 meters and 24 degrees C. Peak incremental exercise values for power (242 +/- 7 versus 253 +/- 10 watts), oxygen consumption (3.08 +/- 0.1 versus 3.26 +/- 0.14 liters/minute), heart rate (188 +/- 2 versus 189 +/- 3 beats/minute), minute ventilation (129 +/- 4.6 versus 144 +/- 7.7 liters/minute), oxygen pulse (16.4 +/- 0.5 versus 17.3 +/- 0.8 ml/beat), and respiratory exchange ratio (1.31 +/- 0.01 versus 1.33 +/- 0.02) revealed no significant differences (p less than 0.05) between the SCT and control groups, respectively. Peak incremental exercise values for arterial oxygen tension (82 +/- 1.7 versus 82 +/- 2.2 mm Hg), arterial carbon dioxide tension (32 +/- 0.7 versus 31 +/- 0.9 mm Hg), and alveolar-arterial oxygen pressure differences (19 +/- 1.4 versus 21 +/- 1.9 mm Hg) were similar for the SCT and control groups, respectively. Steady-state exercise results corroborate incremental exercise findings. It is concluded that cardiopulmonary and gas exchange responses to a brief period of strenuous exercise performed at low altitude at 24 degrees C in a well-characterized SCT sample of recruits were within normal limits and comparable to those of a carefully selected control sample.
Adult↗
Effect of moderate inspiratory hypoxia on exercise performance in sickle cell trait.
In previous work (Weisman IM, Zeballos RJ, Johnson BD: Cardiopulmonary and gas exchange responses to acute strenuous exercise at 1,270 meters in sickle cell trait. Am J Med 1988; 84: 377-383), no significant differences in cardiopulmonary and gas exchange responses to acute, strenuous exercise were observed between volunteers with sickle cell trait (SCT) and control subjects at an altitude of 1,270 meters. The current study was designed to evaluate the effect of a greater hypoxic stimulus on the response of healthy, black male basic recruits, 11 with SCT (HbAS) and 11 control subjects, to acute strenuous exercise. Simulated 2,300-meter and simulated sea-level conditions were achieved by adjustment of the fraction of inspired oxygen (simulated condition of 2,300 meters equal to 18 percent; simulated sea-level condition equal to 24 percent) at the same barometric pressure (656 mm Hg). For each simulated condition, the subjects performed an incremental exercise test to exhaustion on a cycle ergometer. One steady-state exercise test with radial arterial access for arterial blood gases was performed under each condition on Day 2. Peak incremental exercise values for oxygen consumption (2.9 versus 2.81 liters/minute), heart rate (189 versus 187 beats/minute), oxygen pulse (15.4 versus 15.1 ml/beat), and anaerobic threshold (1.59 versus 1.62 liters/minute), at the simulated 2,300-meter height revealed no significant differences between men with SCT and control subjects, respectively. A 5 to 9 percent decrement in exercise performance at the simulated 2,300-meter level compared with exercise performance at the simulated sea-level condition was noted for both groups. Steady-state exercise values for arterial oxygen tension (64 versus 65 mm Hg), arterial oxygen saturation (90 versus 90 percent), alveolar-arterial oxygen pressure difference (22 versus 21 mm Hg), and physiologic dead space to tidal volume ratio (12 versus 11) at the simulated condition of 2,300 meters were similar for the SCT and control groups, respectively. It is concluded that in a moderate hypoxic environment, the cardiopulmonary and gas exchange responses of persons with SCT during brief episodes of exhaustive exercise were comparable to those of control subjects.
Adult↗
Effect of Army basic training in sickle-cell trait.
In order to determine if sickle-cell trait (SCT) represents an inherent adverse effect on response to training, we objectively evaluated exercise performance in 22 healthy, black men with SCT (hemoglobin AS) and 15 controls (hemoglobin AA) before and after seven weeks of army basic training at an altitude of 1270 m. An incremental exercise test to exhaustion on a cycle ergometer was used. Before basic training, peak exercise measurements did not reveal significant differences between groups other than a slightly lower, albeit significant, value for oxygen uptake (VO2) per kilogram (42 +/- 1 vs 45 +/- 1.4 mL/min per kilogram) for the SCT group. Both groups experienced modest overall cardiovascular improvement reflected in both peak and submaximal exercise responses. No statistically significant difference was observed between the SCT and the control groups at the end of basic training for any of the measured variables at peak exercise, including power (258 +/- 6 vs 266 +/- 9W), VO2 (3.24 +/- .06 vs 3.36 +/- .16 L/min), VO2 per kilogram (46 +/- 0.7 vs 46 +/- 1.2), minute ventilation (138 +/- 4 vs 147 +/- 8 L/min), heart rate (185 +/- 2 vs 184 +/- 3 beats per minute), oxygen pulse (17.6 +/- .3 vs 18.4 +/- 1 mL/min per beat), as well as anaerobic threshold (1.81 +/- .04 vs 1.80 +/- .06 L/min), respectively. No medical problems directly attributed to SCT were reported; it remains uncertain, however, whether a seizure experienced by one of the other SCT basic trainees after a two-mile run was SCT related. The results of this study would, therefore, suggest that for the majority of individuals who possess SCT, the response to the moderate training regimen provided by army basic training is not impaired.
Adult↗
Analysis of hyperventilation response in asthmatics.
We have tested seven young adult asthmatics (17-35 years) with two different tests of airway reactivity, i.e., treadmill exercise test and isocapnic hyperventilation test. To estimate the level of respiratory heat loss we standardized environmental conditions so that during these tests patients inhaled compressed air of 23 degrees and 0% of R.H. The level of ventilation during these tests thus determined the respiratory heat loss. It was found that five out of seven tested patients showed dose-response-like relationships between a change in FEF 25-75% (or FEV1) and minute ventilation as measured during exercise or voluntary hyperventilation (r = -.80 to -.97). However, in two patients this relationship could not be established. These two patients had the lowest baseline pulmonary function of the whole group, and by definition they had the most hyperreactive airways. When the change in pulmonary function observed after three to six minutes of isocapnic hyperventilation (both at the same level of minute ventilation) were compared it was found that the six minute test caused only slightly greater changes (P less than 0.01) than the three minute test. It is concluded that in asthmatics the relationship between a decrease in pulmonary function and respiratory heat loss varies among patients.
Adolescent↗
Two types of responses to exercise and isocapnic hyperventilation in asthmatics.
Seven young adult asthmatics (17-35 years old) with an established diagnosis of mild to severe bronchial asthma were tested twice per day on six different days. On these days, all of the subjects undertook the treadmill exercise test of varying intensity for a duration of 6 minutes. Four hours later a voluntary isocapnic hyperventilation challenge of 6 minutes duration was done with essentially the same level of minute ventilation as achieved during and immediately after the exercise. During exercise and voluntary isocapnic hyperventilation tested patients inhaled dry compressed air of 23 degrees C. Heart rate, minute ventilation and end tidal pCO2 were monitored before, during and after each test. Pulmonary functions were measured before and after each procedure including: spirometry, measurement of airway resistance (Raw) and thoracic gas volume (Tgv). We found that five out of seven patients showed a dose-response-like relationship between a change in pulmonary function (FEF25-75% and FEV1) and total ventilation as measured during treadmill exercise or isocapnic hyperventilation challenge. In two patients we failed to establish this relationship. In these two patients different levels of ventilation (as measured during exercise or isocapnic hyperventilation) induced a similar degree of bronchoconstriction. These two patients had the lowest baseline pulmonary function of the whole group and by definition they had the most reactive airways.
Adolescent↗
The beneficial effect of nasal breathing on exercise-induced bronchoconstriction.
In the first step of a study of the relation of nasal and oral breathing during moderate treadmill exercise to the onset of bronchoconstriction in young patients with perennial bronchial asthma, it was observed that most subjects spontaneously breathed with their mouths open when instructed to breathe "naturally." Subsequently, when they were required to breathe only through the nose during the exercise, an almost complete inhibition of the postexercise bronchoconstrictive airway response was demonstrated. When instructed to breathe only through the mouth during exercise, an increased bronchoconstrictive airway response occurred, as measured by spirometry, flow-volume relationships, and body plethysmography. These findings suggest that the nasopharynx and the oropharynx play important roles in the phenomenon of exercise-induced bronchoconstriction.
Adolescent↗
The role of hyperventilation in exercise-induced bronchoconstriction.
Significant bronchoconstriction, comparable in severity to that observed after moderate treadmill exercise, was induced in asthmatic children by voluntary isocapnic hyperventilation of 3-min and 10-min duration. In both hyperventilation and exercise, nasal breathing inhibited the bronchoconstrictive responses, whereas mouth breathing potentiated the bronchoconstrictive response. In the asthmatic children, 10 min of voluntary isocapnic hyperventilation did not represent a greater bronchoconstrictive stimulus than did 10 min of exercise or 3 min of isocapnic hyperventilation. This study also showed that in normal children there was no measurable airway response after either voluntary isocapnic hyperventilation or moderate exercise. Finally, this study indicates that it is the stimulation of upper airway receptors by relatively cold and dry air, rather than hyperventilation per se, that provokes exercise-induced bronchoconstriction.
Adolescent↗
[Racial influence on the ventilatory response to hypoxia and hypercapnia (author's transl)].
The ventilatory response to hypoxia isocapnic test and to CO2 stimulation in normoxic conditions was measured at rest in 42 sea level subjects. They were classified according to their ancestry in four racial groups: Caucasian, Negro, Mongolian and Mestizo. There was no difference in the response of ventilation to CO2 between the groups. However the response of ventilation to hypoxia was statistically significant, lower in the Mongolian and Mestizo groups than in the Caucasian and Negro ones. All the variables measured were similar in the Mongolian and Mestizo groups. Caucasians showed the lowest resting ventilation and Negroes showed the lowest resting heart rate. Statistically, each of these parameters was significantly different from the other groups. It is concluded that the ventilatory differences observed reflect differences in their peripheral chemoreceptor sensitivity to hypoxia, and they may explain the large variation of ventilatory responses to hypoxia found by different investigators. The similar values found in all parameters measured in the Mongolian and Mestizo groups are explained by the ancestral link between these races.
Asian People↗