Chapter 270: Corridor and Waveform

At 6:50 in the morning, Lin Chen sat on a plastic bench in the hospital’s first-floor lobby. His left foot rested on his right knee, and his fingers slowly kneaded the spot three inches above his ankle. The muscles were stiff, like an old towel soaked through with cold water; when he pressed down, there was no spring in it, only a dull, heavy ache crawling upward along his shinbone. The voice-activated lights went out and came back on. A cleaning auntie pushed a mop cart past him, the rubber wheels grinding over the terrazzo floor with a muffled rasp. The air smelled of disinfectant, damp mop, and boxed meals left overnight.

At exactly seven, the SF Express courier’s electric scooter stopped outside the glass doors. Lin Chen got up and walked over with a slight limp. He signed, then opened the cardboard box. Buried in the foam packing was a gray-white engineering unit. The casing was rough-machined CNC aluminum alloy; the edges had not yet been anodized and still carried tiny burrs from the cutting tool. He pressed the power button on the side. The screen lit up, and the firmware version V1.2-ENG appeared. He connected the test electrodes and attached the simulated load. The voltage curve held steady, and the fan gave off a faint hum. He let out a long breath, put the unit into his backpack, and pulled the zipper all the way up. The metal casing pressed cold against his back, but it felt solid.

At 9:40, on the third floor of the Municipal Second Hospital’s Information Department, the corridor smelled of old paper and antistatic cleaning spray. Lin Chen stood outside Room 302, holding a company-stamped Research Data Access Application Form and a confidentiality agreement. The door opened, and a clerk in black-framed glasses stuck his head out.

“Engineer Lin, right? Director Zhao mentioned you. Come in.”

The office was small. Four monitors stood in a row, and a thin layer of dust had collected around the ventilation holes of the computer towers. The clerk handed him a checklist.

“Desensitized EEG and EMG data from the past three years. Twelve thousand entries in total. Format is EDF+, but the lead naming is inconsistent. You’ll have to write the parsing script yourselves. Also”—the clerk pointed at the regulations on the wall—“the data can only be read on the intranet terminal. No copying, no photos. Anything you need to take away must go through ethics committee approval. That takes about two weeks.”

Lin Chen nodded. “I only need the structured data after feature extraction. Timestamps, peak frequencies, impedance baselines. I’ll run the script on-site, save the results to an encrypted USB drive, and have you review it.”

The clerk glanced at him, said nothing, and cleared half a desk for him. Lin Chen sat down and opened his laptop. His left foot tingled faintly under the desk. He adjusted his posture, shifting his weight entirely onto his right leg. The sound of the keyboard was especially clear in the quiet office. He brought up the parsing script he had written the night before and mounted the intranet mapped drive. The data stream began to roll. Garbled text, missing values, displaced leads. His fingers moved quickly across the trackpad as he revised the regular expressions and added fault-tolerant logic. The progress bar inched forward. At 11:20, the script finished and generated a CSV file. Lin Chen handed it to the clerk.

“Please check the count.”

The clerk opened the file and skimmed it. “Eleven thousand eight hundred entries. The missing two hundred are invalid records caused by electrode detachment. No problem.” He stamped the review seal and handed the USB drive back. “Submit your materials to the Equipment Department this afternoon. Don’t go to the wrong building.”

At two in the afternoon, at the Provincial Hospital Equipment Department, the materials were submitted smoothly, but the preliminary-review doctor’s feedback was direct.

“The warning logic of an offline terminal can’t be judged only by algorithmic accuracy. Clinically, what matters is the balance between ‘no missed alerts’ and ‘no false alerts.’ With a false-positive rate of 0.71, if this is at home, the family will break down. If it is in a ward, the nurses will turn off the power.”

Lin Chen wrote the sentence down. He did not argue. He returned downstairs to the inpatient department and found a quiet flower bed to sit beside. He opened the engineering unit and connected the real-time data stream. Su Man’s message popped up: Got the appointment with Director Zhao. Next Wednesday at 9 a.m., special-needs clinic, No. 15. He requires a device demo and the complete medical records from the past three months. Also, the hardware factory says they replaced the imported cell with a domestic high-rate cell for the low-temperature power-drop issue. Cost is down, but cycle life is only half of the imported one.

Lin Chen replied: The lifespan is enough. Get through filing first.

He turned off his phone and placed the engineering unit on his knees. The screen displayed the real-time waveform. He took a deep breath and began manually injecting interference signals: simulated movement, simulated electrode loosening, simulated environmental electromagnetic interference. The waveform shook violently, and the filtering algorithm began to intervene. The adaptive window narrowed; the high-frequency EMG signals were stripped away. The baseline gradually stabilized. But the voltage reading kept jumping between 3.6V and 3.5V. The 0.8% fluctuation threshold was like a taut string.

He stared at the screen, his finger hovering over the debugging interface. He could not brute-force it. He opened the code editor and added one line to the power-management module: if voltage_drop > 0.05V: trigger_low_power_mode(); reduce_sampling_rate_to_100Hz; Downshift the frequency to stay alive. Sacrifice part of the high-frequency detail in exchange for keeping the warning chain powered. It was a compromise, and it was reality. Perfect parameters in the laboratory had to learn how to bow their heads once they landed in the real world.

A sharp stab of pain shot through his left foot. He lowered his head. Beneath the trouser leg, his ankle had already swollen in a ring. He slowly stood, supporting himself on the edge of the flower bed. With each step, his right leg took twice the weight. He walked back to the ward and pushed the door open. Xiaoman was still asleep, breathing steadily. The monitor on the bedside cabinet ticked on. Lin Chen connected the engineering unit to Xiaoman’s spare lead wire. The waveform synchronized onto the screen. Everything was normal.

At eight that evening, Lin Chen sat at the desk. Three sets of materials were spread out before him: the Municipal Second Hospital’s data analysis report, the Provincial Hospital’s preliminary-review opinion, and the hardware factory’s power test records. He checked them word by word, marking contradictions with a red pen. What clinical practice demanded was certainty, while the engineering unit offered probabilities. In front of Director Zhao, he had to translate those probabilities into language the clinic could understand.

He opened his computer and created a new PowerPoint. The title on the first slide was: Offline Epilepsy Warning Terminal: Supplementary Plan for Clinical Pathways. There were no flashy charts, only three groups of comparative data: the missed-alert rate of traditional monitoring, the false-positive rate of the existing algorithm, and the battery life and warning response time of V1.2 in low-frequency mode. He wrote slowly, weighing every word again and again. He knew that next Wednesday’s fifteen minutes would determine the life or death of these ninety days, and also the bottom line of whether Xiaoman could sleep one full night in peace.

At eleven, Su Man sent over a file: Abstracts of Director Zhao’s core-journal papers from the past three years. He focuses on “early biomarkers of atypical seizures.” In your data, there are two low-frequency spike-wave records that may be useful.

Lin Chen opened the attachment. His gaze stopped on the chart on the third page. He pulled up the Municipal Second Hospital’s data and cross-checked it. Sure enough, seventy-two hours before two major seizures, the EMG signal had shown a faint tremor lasting about four seconds. Its frequency was between 8-12Hz, and the conventional filter had treated it as noise and removed it.

His fingers trembled slightly. It was not excitement, but a kind of heavy confirmation. He immediately modified the code, removed that frequency band from the filter blacklist, and added it to the warning-feature library. The progress bar on the screen began running again.

At one in the morning, the engineering unit suddenly gave a soft “beep.” Lin Chen looked up. In the lower-right corner of the screen, the power indicator shifted from green to yellow. Voltage reading: 3.48V. Low-frequency mode had been triggered. The sampling rate had dropped to 100Hz. But the warning module was still running.

He walked to the window. The night was heavy, and the city lights in the distance were sparse. He took out his phone and sent Zhao Qiming a message: TS terms signed. Meeting Director Zhao next Wednesday. Power-redundancy plan implemented, false-positive rate down to 0.41. Filing materials will be submitted tonight.

After sending it, he returned to the chair and closed his eyes. His left foot was still numb, but his heartbeat was steady. He knew that the real clinical validation was not in the server room, not in the laboratory, but tomorrow morning, when the first slant of sunlight entered the ward—whether the engineering unit could accurately catch those four seconds of tremor one second before the voltage fell below the critical line.

Outside the window, the wind had stopped. From the nurses’ station at the end of the corridor came the electric crackle of an intercom. A new day was counting down.