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583 results on '"Ferretti, Guido"'

28. A revision of maximal oxygen consumption and exercise capacity at altitude 70 years after the first climb of Mount Everest.

Author

Ferretti, Guido and Strapazzon, Giacomo

Subjects
*AEROBIC capacity, *EXERCISE, *ANNIVERSARIES, *BRAIN injuries, *HUMAN physiology, *HYPOXEMIA
Abstract

On the 70th anniversary of the first climb of Mount Everest by Edmund Hillary and Tensing Norgay, we discuss the physiological bases of climbing Everest with or without supplementary oxygen. After summarizing the data of the 1953 expedition and the effects of oxygen administration, we analyse the reasons why Reinhold Messner and Peter Habeler succeeded without supplementary oxygen in 1978. The consequences of this climb for physiology are briefly discussed. An overall analysis of maximal oxygen consumption (V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$) at altitude follows. In this section, we discuss the reasons for the non‐linear fall of V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ at altitude, we support the statement that it is a mirror image of the oxygen equilibrium curve, and we propose an analogue of Hill's model of the oxygen equilibrium curve to analyse the V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ fall. In the following section, we discuss the role of the ventilatory and pulmonary resistances to oxygen flow in limiting V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$, which becomes progressively greater while moving toward higher altitudes. On top of Everest, these resistances provide most of the V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ limitation, and the oxygen equilibrium curve and the respiratory system provide linear responses. This phenomenon is more accentuated in athletes with elevated V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$, due to exercise‐induced arterial hypoxaemia. The large differences in V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ that we observe at sea level disappear at altitude. There is no need for a very high V̇O2max${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ at sea level to climb the highest peaks on Earth. [ABSTRACT FROM AUTHOR]

Published
2024
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32. Optimization of the image contrast in SPECT-CT bremsstrahlung imaging for Selective Internal Radiation Therapy of liver malignancies with Y-90 microspheres

Author

Bonutti, Faustino, Avolio, Matteo, Magro, Giuseppe, Cecotti, Andrea, Della Schiava, Emanuele, Del Dò, Elena, Longo, Francesco, Herassi, Yassine, Bentayeb, Farida, Rossi, Marina, Ferretti, Guido, Geatti, Onelio, and Padovani, Renato

Subjects
Physics - Medical Physics
Abstract

The quality of SPECT Bremsstrahlung images of patients treated with Y-90 is poor, mainly because of scattered radiation and collimator septa penetration. To minimize the latter effect, High Energy (HE) or Medium Energy (ME) collimators can be used. Scatter correction is not possible through the methods commonly used for the diagnostic radionuclides (Tc-99m, etc.) because the Bremsstrahlung radiation does not have distinct photopeaks, but a broad spectrum of energies ranging from zero to the maximum one detectable by the gamma-camera crystal is registered. Scatter radiation and collimator septa penetration affect the Contrast and the Contrast Recovery Coefficient (CRC) : our research focused on finding the best energy position for the acquisition window in order to maximize these parameters. To be guided in this finding, we first made a Monte Carlo (MC) simulation of a SPECT acquisition of a Y-90 cylindrical phantom and then we measured at different energies the Line Spread Function (LSF) of a linear Y-90 source inserted in a scatter medium. Finally we acquired the NEMA IEC Body phantom filled with Y-90 chloride at different energies and using different setups in order to measure the Contrast and the CRC in different conditions with the purpose of optimizing the clinical SPECT acquisition procedures. The final results showed that Contrast and CRC are higher for HE collimators compared to ME collimators and they have a maximum for the larger spheres at 110 - 135 keV., Comment: 13 pages, 9 figures

Published
2015

50. Functional Threshold Power Field Test Exceeds Laboratory Performance in Junior Road Cyclists

Author

Vinetti, Giovanni, Rossi, Huber, Bruseghini, Paolo, Corti, Marco, Ferretti, Guido, Piva, Simone, Taboni, Anna, Fagoni, Nazzareno, Bruseghini, Paolo (ORCID:0000-0003-0285-5443), Vinetti, Giovanni, Rossi, Huber, Bruseghini, Paolo, Corti, Marco, Ferretti, Guido, Piva, Simone, Taboni, Anna, Fagoni, Nazzareno, and Bruseghini, Paolo (ORCID:0000-0003-0285-5443)

Abstract

The functional threshold power (FTP) field test is appealing for junior cyclists, but it was never investigated in this age category, and even in adults, there are few data on FTP collected in field conditions. Nine male junior road cyclists (16.9 ± 0.8 years) performed laboratory determination of maximal aerobic power (MAP), 4-mM lactate threshold (P4mM), critical power (CP), and the curvature constant (W′), plus a field determination of FTP as 95% of the average power output during a 20-minute time trial in an uphill road. The level of significance was set at p < 0.05. Outdoor FTP (269 ± 34 W) was significantly higher than CP (236 ± 24 W) and P4mM (233 ± 23 W). The VO2peak of the field FTP test (66.9 ± 4.4 ml·kg−1·min−1) was significantly higher than the VO2peak assessed in the laboratory (62.7 ± 3.7 ml·kg−1·min−1). Functional threshold power was correlated, in descending order, with MAP (r = 0.95), P4mM (r = 0.94), outdoor and indoor VO2 peak (r = 0.93 and 0.93, respectively), CP (r = 0.84), and W′ (r = 0.66). It follows that in junior road cyclists, the FTP field test was feasible and related primarily to aerobic endurance parameters and secondarily, but notably, to W′. However, the FTP field test significantly exceeded all laboratory performance tests. When translating laboratory results to outdoor uphill conditions, coaches and sport scientists should consider this discrepancy, which may be particularly enhanced in this cycling age category.

Published
2023

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