China
Africa
Explore chapters and articles related to this topic
Biological Imaging and Radiobiological Modeling for Treatment Planning and Response Assessment in Radiation Therapy
Published in Siyong Kim, John Wong, Advanced and Emerging Technologies in Radiation Oncology Physics, 2018
Vitali Moiseenko, Stephen R. Bowen, John P. Kirkpatrick, Robert Jeraj, Lawrence B. Marks
Pulmonary ventilation imaging spans multiple modalities, each with clear trade-offs in clinical utility: [99mTc]DTPA and [99mTc]Technegas SPECT, respiratory-correlated 4DCT (Nyeng et al., 2011; Yamamoto et al., 2014), hyperpolarized 3He MRI (Lipson et al., 2002; Bauman et al., 2013; Ireland et al., 2010), and [68Ga]Galligas PET (Siva et al., 2015). The spatial resolution with 4DCT, MRI, and PET is thought to be better than with SPECT. However, none of these pulmonary ventilation image parameters have been as strongly associated with pulmonary toxicity incidence as perfusion image parameters, and it is not clear if there is an incremental benefit of adding ventilation (e.g., ventilation plus perfusion) to perfusion assessments alone. One physiologic rationale derives from normal pulmonary vessel constriction in the presence of hypoxia (i.e., poor ventilation) that therefore reduces perfusion in unventilated regions. Conversely, the airways are less able to respond to poor perfusion; thus, observations of ventilation in unperfused regions are much more common, as is the case with a pulmonary embolus. Thus, imaging of perfusion is more sensitive than imaging of ventilation in areas of poor function defined by ventilation/perfusion mismatch.
Acceleration
Published in David G. Newman, Flying Fast Jets, 2014
The applied +Gz causes an increased perfusion gradient down the lungs, with more blood going to the bases and less to the apices. At +4 to +5 Gz the upper half of the lungs is effectively not perfused. The combination of these ventilation and perfusion changes under +Gz leads to a considerable ventilation-perfusion mismatch. This can lead to a reduction in arterial oxyhaemoglobin saturation, which is approximately 85 per cent at +5 Gz (compared with the normal 98 per cent at +1 Gz. This effect can be offset by the pilot breathing a higher oxygen concentration (up to 100 per cent).
Cardiovascular system
Published in David A Lisle, Imaging for Students, 2012
The diagnostic hallmark of PE is one or more regions of ventilation/perfusion mismatch, i.e. a region of lung where perfusion is reduced or absent and ventilation is preserved. After correlation with an accompanying CXR, lung scans are graded as low, intermediate or high probability of PE. High probability scan is an accurate predictor of PE. Low probability scan accurately excludes the diagnosis. Unfortunately, a large proportion of patients (up to 75 per cent in some series) have an intermediate probability scan.
Abnormal exercise adaptation after varying severities of COVID-19: A controlled cross-sectional analysis of 392 survivors
Published in European Journal of Sport Science, 2023
Fabrício Braga, Fernanda Domecg, Marcelo Kalichsztein, Gustavo Nobre, José Kezen, Gabriel Espinosa, Christiane Prado, Marcelo Facio, Gabriel Moraes, Ilan Gottlieb, Ronaldo L. Lima, Alfred Danielian, Michael S. Emery
Our data suggest that SC-CoV patients have a worse physiological response to exercise than N-CoV and M-CoV patients. SC-CoV showed not only a higher prevalence of LAC but also an earlier contribution of anaerobic metabolism (lower relative VO2 at VT1), worse ventilatory adaptation (higher VE/VCO2 at VT1 and slope), and a higher frequency of ventilation-perfusion mismatch and/or pulmonary vasculopathy (lower ETCO2 at VT1). Although it is reasonable to infer that COVID-19 itself is responsible for these differences, an older age, worse body morphology (higher weight and percentage body fat) and physical activity profile, and higher prevalence of CAD and diabetes certainly also contributed to an impaired exercise response.
Oxygen: a new look at an old therapy
Published in Journal of the Royal Society of New Zealand, 2019
Richard Beasley, Diane Mackle, Paul Young
Since this report, studies have shown similar physiological responses of an increase in PaCO2 with high flow oxygen therapy across a range of other acute respiratory conditions including asthma (Rodrigo et al. 2003; Perrin et al. 2011) and pneumonia (Wijesinghe et al. 2012) and chronic respiratory conditions such as obesity hyperventilation syndrome (Wijesinghe et al. 2011). In these studies, high flow oxygen increased the PaCO2, compared with breathing room air or titrated oxygen therapy to within a target SpO2 range, suggesting that conservative oxygen administration across all acute and chronic respiratory conditions in which hypoxaemia may be present and oxygen therapy is prescribed may reduce harm. The likely mechanisms for this physiological effect are likely to be worsening ventilation/perfusion mismatch as a result of release of hypoxic pulmonary vasoconstriction, and a reduction in ventilatory drive, both of which will reduce alveolar ventilation, which leads to an increase in PaCO2 (Aubier et al. 1980; Robinson et al. 2000).