There's a slight difference in blood pressure between our left and right arms.
In a normal person, the systolic pressure in the right arm is about 10 mmHg higher than in the left, and the diastolic pressure is about 5 mmHg higher.
A difference of more than 10 mmHg between the arms can indicate a serious health problem.
Clinically, a large difference in blood pressure between the arms leads doctors to highly suspect one of several conditions.
First, aortic dissection.
Second, severe arteriosclerosis.
Third, arterial embolism.
In Yan Feifan's earlier estimation, the difference in Mrs. Na's blood pressure was at least 15 mmHg.
Combined with Mrs. Na's symptoms, Yan Feifan judged with at least ninety percent certainty that she had a thoracoabdominal aortic dissection.
This condition is extremely critical.
If her aortic dissection were to rupture, it would cause massive internal bleeding in her thoracic and abdominal cavities, which could be fatal in an instant.
Seeing how serious Yan Feifan was, Mrs. Na grew scared. She stopped arguing and had a colleague drive her to the Affiliated Hospital...
After waiting for another ten-plus minutes, Zheng Libin finally returned to the office.
He pulled up a video, about three minutes long, on his office computer and asked Yan Feifan to watch it.
When he saw the video's content, Yan Feifan shot a look at Zheng Libin.
'This guy... he's really testing me.'
The first person in the video was dressed from head to toe in riot gear, complete with a full-face helmet.
The four people who appeared after him were all dressed in the same attire.
Zheng Libin waited for Yan Feifan to finish the video, then explained, a bit embarrassed, "Mr. Yan, my apologies."
"My superior said the verification had to be rigorous, so the results would be irrefutable."
Yan Feifan smiled and said confidently, "That's how it should be. This way, the results will be convincing."
"Let's begin the identification."
Zheng Libin stood up, gestured for him to proceed, and said, "Mr. Yan, if you're ready, please follow me."
"They're on the small training ground in the courtyard right now..."
Yan Feifan followed Zheng Libin out of the office.
When they arrived at the Public Security Bureau's courtyard, Yan Feifan saw five police officers in riot gear standing in a neat line on the basketball court.
They were all of similar height, around 178 centimeters, with comparable body types.
And they were all wearing full-face helmets.
Beside these five, a dozen or so men and women in police uniforms or plain clothes were also standing there.
Evidently, these people had gathered either to watch the show or to witness the event firsthand.
Zheng Libin led Yan Feifan to the front of the line of five and said in a stern voice, "In a moment, I want you to walk exactly as you did when we filmed the video."
"If anyone deliberately holds back or alters their movements, they'll be disciplined for violating work protocol."
"Do you understand?"
"Yes, sir!"
The five men's sudden, unified shout was so loud it made Yan Feifan's ears ring.
Zheng Libin nodded in satisfaction and turned to Yan Feifan. "Mr. Yan, from now on, they will follow your instructions."
"If you want one of them to step out and walk around, just point."
"If you want him to walk in a certain way, just give the order."
Yan Feifan glanced at the five men and said with a straight face, "Mr. Zheng, there's no need for all that trouble. Just have them all walk back and forth a few times together."
Zheng Libin let out a soft "Oh," then looked at the five men and shouted, "Use the same gait you used when we filmed the video. Move around freely."
"Now... begin!"
At his command, the five men broke from their line and began walking back and forth within the confines of half the basketball court.
Yan Feifan watched for a moment, his brow furrowing involuntarily.
In his mind, he was capturing the most minute details of their gaits: the speed and height of their steps, the angle of their arm and hand swings, whether their heads tilted forward or swayed, the degree of their upper body's side-to-side and back-and-forth movement, the swing of their hips, and more.
He compared this information, one by one, with the gait characteristics of the men in the video he had just watched.
But...
Yan Feifan closed his eyes, concentrating all his effort on a deeper analysis.
Beside him, Zheng Libin was watching Yan Feifan intently.
He was aware of technology like gait analysis; just like facial and voice recognition, there was specialized analytical software for it.
It was just that the district's Public Security Bureau didn't have such software.