Ear oximetry during combined hypoxia and exercise.
ABSTRACT Ear oximetry is widely used to detect arterial O2 desaturation during exercise in patients with cardiopulmonary disease. Although oximeters have been evaluated for accuracy, response time, and the influence of skin pigmentation, tests of their reliability have not been reported during strenuous exercise. Accordingly, we compared arterial O2 saturation (Sao2) measurements obtained by Hewlett-Packard (HP, model 47201A) and Biox II oximeters with those determined directly from arterial blood in six healthy volunteers during progressive exercise while rebreathing hypoxic gas mixtures. The relationship between the HP oximeter value and blood Sao2 was described by the equation: HP = 0.93 (Sao2) + 5.37 and for the Biox II: Biox = 0.55 (Sao2) + 38.97. With these equations, at a blood Sao2 value of 90%, the underestimation by both oximeters was less than 2%. At a blood value of 70%, the HP oximeter overestimated blood Sao2 by 0.7%, whereas the Biox II showed an overestimation of 10.7%. Below blood Sao2 of 83%, the Biox II tended to overestimate blood Sao2 by an amount greater than the error of the instrument, whereas the HP estimations were within the error of the instrument over all levels of blood Sao2 studied. We conclude that the HP oximeter provides valid estimates of Sao2 during exercise but that the Biox II oximeter, although reflecting qualitative changes in oxygenation that occur during exercise, does not provide accurate records of the degree of desaturation.
- [Show abstract] [Hide abstract]
ABSTRACT: To determine the effect of exercise mode on ventilatory patterns, 22 trained men performed two maximal graded exercise tests; one running on a treadmill and one cycling on an ergometer. Tidal flow-volume (FV) loops were recorded during each minute of exercise with maximal loops measured pre and post exercise. Running resulted in a greater VO2peak than cycling (62.7±7.6 vs. 58.1±7.2 mL·kg(-1)·min(-1)). Although maximal ventilation (VEmax) did not differ between modes, ventilatory equivalents for O2 and CO2 were significantly larger during maximal cycling. Arterial oxygen saturation (estimated via ear oximeter) was also greater during maximal cycling, as were end-expiratory (EELV; 3.40±0.54 vs. 3.21±0.55L) and end-inspiratory lung volumes, (EILV; 6.24±0.88 vs. 5.90±0.74L). Based on these results we conclude that ventilatory patterns differ as a function of exercise mode and these observed differences are likely due to the differences in posture adopted during exercise in these modes.Respiratory Physiology & Neurobiology 11/2013; · 2.05 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Extrapolation from post-exercise measurements has been used to estimate respiratory and blood gas parameters during exercise. This may not be accurate in exercise with reduced breathing frequency (RBF), since spontaneous breathing usually follows exercise. This study was performed to ascertain whether measurement of oxygen saturation and blood gases immediately after exercise accurately reflected their values during exercise with RBF. Eight healthy male subjects performed an incremental cycling test with RBF at 10 breaths per minute. A constant load test with RBF (B10) was then performed to exhaustion at the peak power output obtained during the incremental test. Finally, the subjects repeated the constant load test with spontaneous breathing (SB) using the same protocol as B10. Pulmonary ventilation (VE), end-tidal oxygen (PETO2), and carbon dioxide pressures (PETCO2) and oxygen saturation (SaO2) were measured during both constant load tests. The partial pressures of oxygen (PO2) and carbon dioxide (PCO2) in capillary blood were measured during the last minute of exercise, immediately following exercise and during the third minute of recovery. At the end of exercise RBF resulted in lower PETO2, SaO2 and PO2, and higher PETCO2 and PCO2 when compared to spontaneous breathing during exercise. Lower SaO2 and PETO2 were detected only for the first 16s and 20s of recovery after B10 compared to the corresponding period in SB. There were no significant differences in PO2 between SB and B10 measured immediately after the exercise. During recovery from exercise, PETCO2 remained elevated for the first 120s in the B10 trial. There were also significant differences between SB and B10 in PCO2 immediately after exercise. We conclude that RBF during high intensity exercise results in hypoxia; however, due to post-exercise hyperpnoea, measurements of blood gas parameters taken 15s after cessation of exercise did not reflect the changes in PO2 and SaO2 seen during exercise. Key pointsIn some sports, the environment is inappropriate for direct measurement of respiratory and blood gas parameters during exercise. To overcome this problem, extrapolation from post-exercise measurements has often been used to estimate changes in respiratory and blood gas parameters during exercise.The possibility of hypoxia and hypercapnia during exercise with reduced breathing frequency has been tested by measuring capillary blood sampled after the exercise.Reduced breathing frequency during high intensity exercise results in hypoxia; however, due to marked post-exercise hyperventilation, measurements of blood gas parameters taken 15 s after the cessation of exercise did not yield any changes in these parameters.Despite hyperventilation during recovery, hypercapnia could be detected by measuring blood gas parameters within 15 s after the exercise with reduced breathing frequency.Journal of sports science & medicine 01/2009; 8(3):452-457. · 0.89 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The purpose of this study was to examine the physiological responses to treadmill and cycle cardiopulmonary exercise testing (CPET) in male and female COPD patients. Fifty five patients [28 males (FEV1=58.2±19.5% predicted), and 27 females (FEV1=65.3±16.6% predicted)] completed a treadmill and a cycle CPET in random order on two separate days. Respiratory and cardiovascular data were obtained. Compared to the cycle CPET, the treadmill elicited greater peak power output and peak oxygen uptake, while arterial saturation at peak exercise was lower with the treadmill; however, there were no differences between the responses in men and women. No differences were observed in heart rate, ventilation, tidal volume/breathing frequency, inspiratory capacity, or dyspnea responses between modalities or sex. The physiological responses between treadmill and cycle CPET protocols are largely similar for both men and women with COPD, indicating that either modality can be used in mild/moderate COPD patients.Respiratory Physiology & Neurobiology 12/2013; · 2.05 Impact Factor