After his shift in the wards, Zhang needed to call the patients' families and update them of their loved-one's condition.

On one occasion, after speaking to one patient's family member, he was told that they were on the way to another hospital because they were also infected.

"I felt bad for the patient, but all we could do was to try and save as many patients as possible," Zhang says.

He says as an ICU doctor, one has to adapt themselves to accepting the truth that not all patients can be saved.

Zhang says he felt mentally OK when he returned from Wuhan. However, the psychological test conducted by his hospital showed that he still needed time to recover from his experiences there.

Zhang started his career in the cardiothoracic surgery department, where he watched senior doctors operate and became interested by the work in the ICU, where the patients were looked after following their surgery.

In 2005, he turned his focus to critical care medicine, and he enjoyed the sense of achievement he got when a patient was saved from the brink of death.

"When you see your patient after they are fully recovered, they look like a totally different person than when they were in the ICU, which feels good," Zhang explains.

Zhang says to be a good critical care medicine doctor takes a dedication to the job, which brings great pressure and needs sharp focus on the constantly changing conditions of the patients.

"You need to make judgments quickly, as it's a profession that has a very low tolerance for error－often, there is not much time for you to save your patient's life."

Zhang originally planned to take his family out of Beijing for the Spring Festival holiday, but the outbreak changed that plan.

When he returned home at the end of April, with schools conducting classes online due to the pandemic, Zhang has been able to enjoy more time with his daughter Zhang Mulan.

She wrote him a letter four days after he left for Wuhan in January.

"Dad, you are at the front line of the fight against the epidemic, there must be many patients who are in a dangerous condition. You are an ICU doctor who treats the patients closely and fights the virus directly. I worry about you every day, so please take good care of yourself," his daughter writes. "Only by protecting yourself well can you save more patients' lives."

Zhang Hongmin says his aunt told him that his mother, who likes to watch TV dramas, turned the channel to watch the news each day while he was working in Wuhan.

"She only resumed watching her TV shows when I came back to Beijing," Zhang Hongmin says.

Contact the writer at liyingxue@chinadaily.com.cn