ABSTRACT
Sustained hypoxic pulmonary vasoconstriction (HPV ) as experienced at high altitude can lead to hypoxic pulmonary hypertension(HPH).HPV,a special physiological phenomenon of lung,is the physiological reflex of organism in hypoxic envi-ronment.However,in high altitude hypoxic environment,the sustained HPV can lead to pulmonary vascular remodeling and right ventricular hypertrophy,at the same time,the degree of hypoxia in alveoli can be aggravated.Vicious circle of hypoxia is formed,further causing the severe high altitude sickness such as pulmonary edema and pulmonary heart disease.HPV appears in preliminary of HPH,but in the chronic phase,irreversible hy-poxic pulmonary vascular remodeling forms.Therefore,studying the mechanism of HPV and the effect of HPV in HPH can pro-vide targets and ideas for the prevention and treatment of high al-titude sickness. Additionally, in preliminary stage of HPV, prompt treatment is critical for the prevention of high altitude sickness.However,the mechanism of HPV and its roles in HPH are still not fully elucidated in current studies.This paper sum-marizes the studies about HPV in HPH of recent years,aiming to provide references for researchers and clinical treatment in this research field.
ABSTRACT
AIM:This study continuously monitors the hemodynamic changes in conscious and anesthetic rats during rapid ascent to high altitude to investigate whether there is difference between the 2 conditions and discuss the rela-ted underlying mechanism.METHODS: Sprague-Dawley rats were randomly divided into conscious group, anesthetic group, anesthetic-5000-control ( A-5000-control) group, anesthetic-5000-aminoguanidine ( A-5000-AG) group, conscious-5000-control ( C-5000-control ) group and conscious-5000-aminoguanidine ( C-5000-AG ) group.The rats in anesthetic group and conscious group were kept in a hypobaric chamber, in which the simulated altitude was increased from 2 260 m to 5 000 m at 2 m/s, and the rats in other 4 groups were at 5 000 m.The system arterial pressure ( Psa) , central venous pressure ( CVP) , heart rate ( HR) and breathing rate ( BR) were directly and continuously displayed and digitally recorded by a high-performance data acquisition (PowerLab 16/35, AD Instruments) at 200 Hz.RESULTS: The HR and BR in the conscious rats were higher and MAP was lower than those in the anesthetic rats obviously.A significant decrease in mean arterial pressure ( MAP) in conscious and anesthetic groups was observed following the increase in the altitude levels, and the net decrease in MAP in conscious group was significantly greater.Additionally, HR in the conscious rats was sig-nificantly lower at 5 000 m than that of the initial level.The rats in C-5000-AG group and A-5000-AG group showed a sig-nificant increase in the arterial pressure after the intravenous injection of AG, a selective inhibitor of inducible nitric oxide synthase ( iNOS) , and no marked change of HR and BR was found.CONCLUSION: Blood pressure and HR decrease during rapid ascent to high altitude, while the change of BR is not obvious.The mechanisms of self-safety would be trig-gered in the early stage of hypoxia, which activates iNOS and then leads to a larger number of nitric oxide.Plentiful NO di-astolizes the vessels to improve the ventilation-perfusion mismatch and lower the blood pressure.When the altitude arise to 5 000 m, even more earlier, a decompensatory stage may occur in the body, leading to decreased HR and blood pressure further more than those in the anesthetic rats.Due to the effects of pentobarbital sodium, the depression of blood pressure requires a lag period and the net decrease in MAP is less than that in the conscious rats.Therefore, hemodynamic changes during rapid ascent to high altitude in conscious rats are more comprehensive and authentic.
ABSTRACT
@#BACKGROUND:Human activity in wilderness areas has increased globally in recent decades, leading to increased risk of injury and illness. Wilderness medicine has developed in response to both need and interest. METHODS:The field of wilderness medicine encompasses many areas of interest. Some focus on special circumstances (such as avalanches) while others have a broader scope (such as trauma care). Several core areas of key interest within wilderness medicine are discussed in this study. RESULTS:Wilderness medicine is characterized by remote and improvised care of patients with routine or exotic illnesses or trauma, limited resources and manpower, and delayed evacuation to definitive care. Wilderness medicine is developing rapidly and draws from the breadth of medical and surgical subspecialties as well as the technical fields of mountaineering, climbing, and diving. Research, epidemiology, and evidence-based guidelines are evolving. A hallmark of this field is injury prevention and risk mitigation. The range of topics encompasses high-altitude cerebral edema, decompression sickness, snake envenomation, lightning injury, extremity trauma, and gastroenteritis. Several professional societies, academic fellowships, and training organizations offer education and resources for laypeople and health care professionals. CONCLUSIONS:The future of wilderness medicine is unfolding on multiple fronts:education, research, training, technology, communications, and environment. Although wilderness medicine research is technically difficult to perform, it is essential to deepening our understanding of the contribution of specific techniques in achieving improvements in clinical outcomes.