Adv Exp Med Biol
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Tissue oxygenation during exercise measured with NIRS: reproducibility and influence of wavelengths.
Near-infrared spectroscopy (NIRS) is widely used for the measurement of skeletal muscle oxygenation during exercise as it reflects muscle metabolism, and most studies report a large variability between subjects. Here we assess the data quality of tissue oxygen saturation (SO2) and oxygenated (oxyHb) and deoxygenated (deoxyHb) haemoglobin concentrations recorded during an incremental cycling protocol in nine healthy volunteers. ⋯ We found that the inter-subject variation in SO2 (standard deviation ≈ 6 %) was considerably larger than the reproducibility (≈ 1.5 %) both for the same-day and different-day tests. The reproducibility of changes in SO2 was better than 1 %.
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Jørgensen and Dau (J Acoust Soc Am 130:1475-1487, 2011) proposed the speech-based envelope power spectrum model (sEPSM) in an attempt to overcome the limitations of the classical speech transmission index (STI) and speech intelligibility index (SII) in conditions with nonlinearly processed speech. Instead of considering the reduction of the temporal modulation energy as the intelligibility metric, as assumed in the STI, the sEPSM applies the signal-to-noise ratio in the envelope domain (SNRenv). This metric was shown to be the key for predicting the intelligibility of reverberant speech as well as noisy speech processed by spectral subtraction. ⋯ However, since the STMI applies the same decision metric as the STI, it fails to account for spectral subtraction. The results from this study suggest that the SNRenv might reflect a powerful decision metric, while some explicit across-frequency analysis seems crucial in some conditions. How such across-frequency analysis is "realized" in the auditory system remains unresolved.
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Portable near-infrared spectroscopy (NIRS) has been shown to be a useful and reliable tool for monitoring muscle oxygenation and blood volume changes during dynamic exercise in elite athletes. The wearable nature of such technology permits the measurement of specific muscles/muscle groups during realistic sport-specific exercise tasks in an outdoor environment. The aim of this case study was to observe the effect on arm and leg muscle oxygenation of roller skiing over a typical outdoor racing course. ⋯ During the steep uphill section of the course, arm and leg TSI decreased equally in one subject (ΔTSI = -10 %), whereas there was a difference between the two muscle groups in the other subject (ΔTSIquadriceps = -2 %; ΔTSItriceps = -7 %). A difference was also seen between subjects during the downhill section of the course. This study presents the first example of the use of portable NIRS to assess oxygenation and blood volume changes in multiple muscle groups during roller skiing in a realistic, outdoor setting.
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Phosphodiesterases (PDEs) are enzymes responsible for degradation of cAMP and cGMP in cells. Thus, PDE inhibitors may have significant clinical benefit in respiratory diseases associated with inflammation. The aim of the present study was to evaluate the effects of selective PDE4 (rolipram, ROL) and PDE7 inhibitors (BRL50481, BRL) on citric acid-induced cough, in vivo and in vitro airway smooth muscle reactivity in both healthy and ovalbumin sensitized guinea pigs. ⋯ In healthy guinea pigs, the only significant relaxation was observed after ROL in ACH-induced contractions in vitro and the effect on cough was negligible. In ovalbumin-sensitized animals, more pronounced in vitro relaxing effects of BRL in HIS-induced contractions and of combination (ROL+BRL) in ACH-induced contractions were observed, with similar results in vivo, and no significant change in the number of cough efforts was observed in any of the groups tested. The results suggest that PDE4 and PDE7 inhibitors have stronger anti-inflammatory effects compared with direct effects on smooth muscle and cough, with a potential benefit of their concomitant administration.
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We describe the extension of a computational model of blood flow and metabolism in the piglet brain to investigate changes in neonatal intracellular brain pH during hypoxia-ischemia (HI). The model is able to simulate near-infrared spectroscopy (NIRS) and magnetic resonance spectroscopy (MRS) measurements obtained from HI experiments conducted in piglets. We adopt a method of using (31)P-MRS data to estimate of intracellular pH and compare measured pH and oxygenation with their modelled counterparts. We show that both NIRS and MRS measurements are predicted well in the new version of the model.