China
Africa
Explore chapters and articles related to this topic
Altitude, temperature, circadian rhythms and exercise
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Henning Wackerhage, Kenneth A. Dyar, Martin Schönfelder
At high altitude, people are exposed to chronic hypoxia. For example, if the barometric pressure at sea level is 760 mmHg then the inspired partial pressure of oxygen (PIO2) will be 149 mmHg, 101 mmHg in a settlement at 3,000 m, 89 mmHg at 4,000 m and 78 mmHg at 5,000 m. Such hypoxia is a great challenge to the human body and of the more than 140 million people that live above 250 m, 5–10% are at risk of developing chronic mountain sickness. Chronic mountain sickness is a major health problem which is associated with a high haemoglobin concentration and haematocrit, a reduced oxygen saturation and often a high blood pressure in the lung circuit, termed pulmonary hypertension (22). Thus, the questions are: Are populations that live permanently at high altitudes genetically adapted to chronic hypoxia? Do they carry DNA sequence variants such as those possessed by a Finnish family, where a heterozygous EPO receptor gene (EPOR) mutation increased haematocrit (23)?
Measuring and monitoring vital signs
Published in Nicola Neale, Joanne Sale, Developing Practical Nursing Skills, 2022
Oxygen saturation should be checked by pulse oximetry for everyone as part of their vital signs monitoring and is an inexpensive and non-invasive method of assessing this. Pulse oximetry should be available wherever emergency oxygen is used. Hypoxaemia can rapidly lead to tissue damage however assessing through observation is notoriously inaccurate and unreliable. The brain is very sensitive to oxygen depletion, and visual and cognitive changes can occur when oxygen saturation falls to 80–85%. Other signs of hypoxaemia include restlessness, agitation, hypotension and tachycardia. However, all these signs can be missed or wrongly interpreted.
Radiobiology of Tumours
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Gordon Steel, Catharine West, Alan Nahum
During the 1960s and 1970s, tumour hypoxia was perceived to be one of the principal causes of failure in radiation therapy, and much research effort was directed at developing ways of selectively killing hypoxic cells: high-linear energy transfer (LET) radiations (see Section 6.11.5), hyperbaric oxygen, chemical radiosensitisers, etc. Although the results of individual studies were equivocal, meta-analyses showed that hypoxia modification of radiotherapy worked (Overgaard 1994, 2011). The most recent randomised trials confirmed that targeting hypoxia improves radiotherapy outcomes in head and neck (Overgaard et al. 1998; Janssens et al. 2012) and bladder (Hoskin et al. 2010) cancers. There is also a large body of evidence indicating that hypoxia is an adverse prognostic factor. For example, studies using Eppendorf pO2 microelectrodes showed that hypoxia identified prior to the start of radiotherapy is associated with the treatment failure of cervical (Hockel et al. 1996), head and neck (Nordsmark et al. 2005) and prostate (Movsas et al. 2002; Milosevic et al. 2012) carcinomas and of sarcomas (Nordsmark et al. 2001). There is also good evidence that patients with the most hypoxic tumours benefit most from the addition of hypoxia-modifying agents (e.g. Toustrup et al. 2012; Eustace et al. 2013).
Hypoxemia and not hyperoxemia predicts worse outcome in severe COPD exacerbations - an observational study
Published in European Clinical Respiratory Journal, 2023
Charlotte Sandau, Ejvind Frausing Hansen, Lars Pedersen, Jens Ulrik Stæhr Jensen
Thus, our data does not confirm the high risk of hyperoxemia described by most literature, but underlines the high risks associated with hypoxemia in admitted patients with AECOPD. This especially so, since most of the patients who experienced hypoxemia, only experienced a single episode. Moreover, based on explorative analysis, it seemed that the number of hypoxemic episodes could be of essence for the prognosis rather than the degree of hypoxemia. Our results pinpoint the need for interventional studies on the correct oxygen target among admitted patients with COPD exacerbation, and they raise considerable doubt on whether results from pre-hospital settings can be extrapolated into hospital settings. This is a serious concern, since oxygen saturation targets of 88%-92% have been adapted in hospital-settings, despite them being based on pre-hospital studies.
Critical Care Flight Nurses' role within secondary aeromedical services and the inter-hospital transfer of patients with acute spinal cord impairment
Published in Contemporary Nurse, 2023
Hypoxia is defined as oxygen deficiency in body tissues sufficient to cause impairment of aerobic metabolism and normal physiological cell function (Blumen et al., 2015). Hypoxemia is defined as a reduced content of oxygen in arterial blood (Pa02) and is a major cause of hypoxia (Holleran et al., 2018). Hypoxemia can occur due to mismatching of V/Q however, the most common cause of hypoxemia in the aeromedical environment is hypobaric hypoxic hypoxia (O'Driscoll et al., 2017). Hypobaric hypoxic hypoxia is explained by Dalton’s law, which describes how the partial pressure of a gas decreases with increasing altitude due to reduced barometric pressure (Blumen et al., 2015). This will result in a reduced Alveolar Partial Pressure of Oxygen (PA02). The significance of this to hypoxia is described by Fick’s law which explains that diffusion of oxygen occurs from a high to low partial pressure and that the rate of diffusion is proportional to the concentration gradient (Lumb, 2021). Consequently, an adequate PA02 is essential for oxygen to diffuse from alveoli, to pulmonary capillaries, arterial blood and ultimately body tissues. Hypobaric hypoxic hypoxia can be prevented through the administration of supplemental oxygen and the provision of a pressurised aircraft cabin (Blumen et al. 2015).
An updated review of mesoporous carbon as a novel drug delivery system
Published in Drug Development and Industrial Pharmacy, 2021
Mohamed S. Attia, Mohamed Y. Hassaballah, Mohab A. Abdelqawy, Mahmoud Emad-Eldin, Aya K. Farag, Ahmed Negida, Hazem Ghaith, Sherif E. Emam
Hypoxia is a biological condition that refers to partially low oxygen supplementation under certain circumstances such as cancer and ischemia. This effect usually alters the extracellular matrix and the cellular biochemical environment that is believed to be directly linked to tumor invasiveness, metastasis, and resistance. It was found that oxygen level decreases from the tumor surface and toward its interior [51–53]. Hypoxia has recently become an effective strategy that can trigger drug release responsively and suit the targeted delivery mechanism. The release mechanism is relying on the disparity in the partial oxygen concentration between tumors and normal tissues. Mesoporous materials were thus developed with specific gatekeepers responsively eliciting drug release according to the oxygen concentration [54]. This novel drug-releasing technique can be a promising approach for further applications if implemented to design carbonaceous materials.