The oxygen is so thin on the Tibetan plateau that a local clinic is offering pre-trip examinations for senior citizens or people with medical conditions, who might be challenged at such extreme altitudes.

Zhongshan Hospital's respiratory disease department began offering examinations this month for people planning air travel or a trip to places at extreme elevation.

"About 5 percent of people are not suitable for taking a plane or going to the plateau, especially those of advanced age or having serious asthma, lung or heart disease," said Dr Bai Chunxue, director of the respiratory disease department.

At the clinic, doctors examine lung and heart function and blood test.

Additionally, patients will breathe oxygen from a mask that is 15 percent thinner than the air near sea level for 15 minutes to test whether a person can endure such situation.

"Failing to pass the test doesn't mean a red light to take an airplane or visit the plateau. We will give medicines and direct them to take additional oxygen if they feel sick," Bai said.

"People over 60 years old or having respiratory diseases and cardiovascular syndromes had better undergo such checkup before traveling."

A local travel agency encourages such pre-Tibet testing, suggesting those particularly with weakened health and advanced age go for a checkup.

"For customers with poor health, we can design package tours to avoid risking their life," said Wang Jiping, manager of Shanghai Odessey Traveling Agency.

"We have met some middle-aged stubborn people with high blood pressure who insisted in going to Tibet and suffered serious altitude sickness there," Wang said.

(Shanghai Daily via Xinhua August 21, 2006)