Chapter 269: Redundancy and Metrics

The busy tone after the call ended dragged on for a long time in the ward. Lin Chen did not put down his phone right away. The screen dimmed, reflecting the gray-blue shadows beneath his eyes. The reply from the equipment department at the Provincial Hospital had been more straightforward than expected, but behind the four words “green channel” lay a compliance review stricter than the regular process. He sat up again, shifting his weight half an inch toward his right leg. The numbness around his left ankle was like a thick layer of waterlogged cotton, wrapping around the bone and dragging it downward.

An email notification sounded. The FA on Zhao Qiming’s side had sent over the official PDF of the Term Sheet. Lin Chen opened it and checked it item by item. A two-million-yuan seed round, divided into three tranches. The first tranche was five hundred thousand, to arrive within seven working days. Not a word of the performance-bet clause had changed: within ninety days, two prefecture-level city community hospitals, fifty units deployed, an 85% retention rate, false positives reduced below 0.4%, missed detections no higher than 0.1%, and acceptance of the Class II medical device filing. One additional line in small print had been added to the supplementary clauses: if a clinical adverse event occurred due to defects in the product itself, the investor had the right to unilaterally terminate the agreement and recover the initial investment.

He picked up a pen and wrote “50 units × hardware cost” in a blank space on the scratch paper. Motherboard prototyping, shell tooling, power modules, sensor arrays, packaging and logistics. The four-hundred-yuan price increase for the imported battery cells that Su Man had mentioned that afternoon would directly eat up the bulk of the gross margin on each unit. If they followed the original plan, the cash flow for fifty units would bottom out in the third month. He could not gamble on luck.

Lin Chen closed the PDF and opened the circuit design software. The parallel circuit diagram on the screen was still in its rough-sketch stage. He pulled up the datasheet for the power management chip, his gaze stopping on two parameters: “low-dropout linear regulator (LDO)” and “dynamic voltage scaling.” The advantage of the imported cells was their stable discharge curve at low temperatures, but the consistency of domestic cells’ internal resistance at room temperature already met the standard. The problem lay in the voltage plunge below 15°C. He did not need to change the cells. He only needed to add a buffer layer.

He added two components to the schematic: a low-quiescent-current LDO, paired with a voltage sampling interrupt on the firmware side. When the system detected the input voltage dropping below the threshold, it would automatically switch to low-power monitoring mode, cut power to non-core modules, and keep only electrode acquisition and local storage running. The cost was that warning latency would increase by 0.5 seconds, but it could keep the device from losing power. A 0.5-second delay was within clinically acceptable limits, while the cost per unit would rise by only twelve yuan.

He saved the file and marked the version number: HW_V1.2_电源冗余方案. His fingers tapped over the keyboard as he organized the key points of the plan into an email, copying the hardware factory and Su Man. Just as he pressed Send, a sharp spasm suddenly shot through his left foot. The muscle twitched beyond his control, tugging at the back of his calf. Lin Chen clenched his molars and made no sound. He bent down, grasped his left ankle with both hands, and pressed his thumbs hard into the Chengshan acupoint. The pain receded like a tide, leaving behind a lingering ache and swelling. He straightened, fished half a bottle of mineral water from the drawer, and gulped down two mouthfuls. The water had gone completely cold; it slid down his esophagus and triggered a tight contraction in his stomach.

The monitor in the neighboring ward gave off a regular ticking sound. Lin Chen pushed the door open and went in. Xiao Man was sleeping deeply, breathing evenly. Electrode pads were attached to his chest, and the leads hung down along the edge of the bedsheet. Lin Chen glanced at the waveform on the screen: heart rate 72, blood oxygen 98%, EEG rhythm stable. He picked up the logbook at the bedside, turned to the latest page, and wrote down the date, time, and vital sign data. The handwriting was neat, with no corrections. This notebook had been used from 2014 until now, a thick stack of pages recording the interval between every episode, medication responses, and environmental triggers. It was not a medical chart. It was an error log.

Back at the desk, his phone screen lit up. A message from Su Man popped up: The hardware factory confirms the LDO plan is feasible, and the prototyping cycle can be compressed to four weeks. But there are variables with the ethics committee. Municipal Second Hospital requires ten retrospective clinical cases to be submitted first, or they won’t schedule us. Our simulated data isn’t enough.

Lin Chen stared at the screen. Ten retrospective cases. That meant retrieving monitoring records for epilepsy patients from the past three years who met the inclusion criteria, then anonymizing them. The hospital’s data department would not easily grant access. He leaned back in his chair and closed his eyes. His mind quickly ran through the contacts he could use. Professor Zhou, his university advisor? He had led horizontal projects in neurology, but he had been retired for two years. Old Wang from the Provincial Hospital’s equipment department? He only handled procurement and did not touch clinical data.

He opened his eyes, opened his contacts, and scrolled down. He found a number labeled “Old Chen—Municipal Second Hospital Information Department.” It was a contact he had kept from 2016, when he had done outsourcing work in the provincial capital and helped the hospital with a data migration. They had later lost touch, though they still occasionally liked each other’s posts. He opened the chat box and typed: Brother Chen, sorry to bother you. I wanted to ask about the process for retrieving historical monitoring data on epilepsy patients at Municipal Second Hospital. We have a research support project that we’d like to put through the green channel, and we need ten anonymized retrospective cases to support the initial ethics review.

Send. There was no immediate reply. He switched back to the code editor and opened the test script for the filtering algorithm. Last night’s 0.71 false-positive record was still sitting in the logs. He pulled up the raw waveform and magnified the high-frequency band of the EMG signal. The logic for adaptive impedance monitoring had already been written into V1.2, but it still needed real motion data for validation. He created a new folder and named it Field_Test_Data. It was empty.

Outside the window, the sky had gone completely dark. The sound-activated lights in the corridor came on and went out again. Footsteps approached from afar, drew near, and stopped at the door. The duty nurse poked her head in and asked in a lowered voice, “Family member for Bed 32, do you need the hot water changed?”

“No, thank you.” Lin Chen stood, moved the folding chair a little closer to the wall, and cleared a path. The nurse nodded and pushed the treatment cart away.

He sat down again, putting his weight on his right leg. Lines of code scrolled across the screen. He added a new logging module to record the threshold of each impedance jump and the adjustment range of the filtering window. He ran the test. The progress bar advanced slowly. Thirty percent, sixty percent, eighty-five percent.

His phone vibrated. Old Chen had replied: The process is strict. You need ethics approval + a research project proposal + a data anonymization commitment letter. If you have preliminary review comments from the Provincial Hospital, I can help you push an internal expedite. But the data can only be provided as anonymized CSV. The raw waveform database is off limits.

Lin Chen typed quickly: We’re submitting the Provincial Hospital preliminary review tonight. We have our own template for the anonymization commitment letter. CSV is enough, including timestamps, heart rate, blood oxygen, and EEG frequency-band power values.

Old Chen: All right. Tomorrow morning at ten, bring the materials to the Information Department, third floor. Miss the time and you’re on your own.

Lin Chen replied, “Received.” He closed the chat window, opened Word, and created a new document titled Data Anonymization and Safe Use Commitment Letter. He checked the clauses word by word, leaving no ambiguity. He knew what hospitals feared was not technology, but liability. Only by drawing the boundaries clearly could the matter move forward.

The document was saved. He rubbed the space between his brows, his gaze falling on the scratch paper at the corner of the desk. Parallel circuits, LDO parameters, twelve yuan in cost, a 0.5-second delay, ten cases of data, a fourteen-day calibration report. Every number was an obstacle. He picked up the pen and drew a small square in the lower right corner of the paper. Inside it, he wrote: D-89.

The countdown had gone from ninety days to eighty-nine.

He reran the filtering script. The progress bar reached one hundred percent. The log displayed the result: [INFO] 自适应滤波生效。误报率降至0.39。漏报率0.08。

The numbers met the target. But Lin Chen knew that a laboratory benchmark was not the same as ward reality. Motion artifacts, electrode detachment, environmental electromagnetic interference—any one variable could pull 0.39 back to 0.7. He needed to take the device out of the machine room and let it run in a real environment.

He picked up his phone and called the contact person at the hardware factory. The phone rang four times before it connected.

“Engineer Lin, this late?” The other person’s voice was tired.

“The V1.2 power plan is confirmed. I’ll send you the prototyping list tomorrow morning. Also,” Lin Chen paused, “I need one engineering unit. Tonight. With the complete shell and basic firmware. I’ll pay the rush fee.”

The other end was silent for two seconds. “Tonight? QC at the factory is off duty. Engineer Lin, this isn’t according to process.”

“I know.” Lin Chen’s voice was very calm. “But the clinic doesn’t wait. I’ll pay the rush fee out of my personal account, not through company reimbursement. At eight tomorrow morning, I need to see the machine.”

The sound of papers being flipped came through the phone. In the end, the other person sighed. “Fine. I’ll have the night shift line run one unit separately. Freight is collect.”

“Thank you.” Lin Chen hung up.

He leaned back in the chair and let out a long breath. His shirt was wet through another layer at the back. He lowered his head and looked at his left foot. The tips of his toes still had no sensation at all. Supporting himself on the edge of the desk, he stood and slowly moved to the window. The early-autumn wind came through the half-open window, carrying the disinfectant smell unique to hospital corridors. Downstairs, the streetlights stretched the shadows of the ginkgo trees very long.

His phone screen lit up again. It was not a message, but a system push notification: Provincial Medical Device Testing Institute Announcement: This month’s calibration schedule is full. Appointments will open next month. Applications must be submitted fifteen working days in advance.

Lin Chen stared at that line of text. The fourteen-day deadline had collided with a fully booked schedule. The green channel might be approved, but the calibration report was stuck. Without the report, the Class II filing could not even be submitted for acceptance. The performance-bet requirement of “filing accepted within ninety days” had turned directly into a dead knot.

He walked back to the desk, opened the browser, and searched for the Provincial Medical Device Testing Institute’s contact information. On the third page, he found a landline number. He picked up his phone and dialed. A long waiting tone sounded in the receiver.

After five rings, someone picked up. The voice was clearly weary. “Hello, Testing Institute.”

“Hello, this is Lin Chen. Regarding Class II filing calibration for an offline monitoring terminal, I’d like to apply for an expedited slot.”

“Expedited?” The other person gave a laugh, the tone cool and bureaucratic. “Mr. Lin, the schedule is assigned by the system. Cutting in line requires special approval. Do you have an official red-headed document from the Provincial Health Commission?”

“No,” Lin Chen said. “But I have letters of intent for deployment in fifty units at community hospitals, and preliminary ethics review comments from two hospitals. The device is used for seizure warning, and the clinical window is very short.”

The other end of the line was quiet for several seconds. Keyboard taps sounded.

“Letters of intent and preliminary review comments won’t qualify for the special approval process,” the other person said. “Unless you can obtain a joint recommendation letter from the neurology department directors of tertiary Grade A hospitals, proving that this device is irreplaceable in the existing clinical pathway. Otherwise, wait in line until next month.”

Lin Chen’s fingers tightened slightly around the phone. A joint recommendation letter. That meant persuading the department director of a tertiary Grade A hospital to endorse a device that had not yet completed its filing. The risk was enormous, the return unknown.

“I understand,” he said. “Thank you.”

He hung up. He sat down again, pressing his weight onto his right leg. The code and spreadsheets on the screen intertwined like a net that was gradually drawing tight. He knew the ninety-day countdown had only truly begun from this second. Outside the window, the night was sinking inch by inch.

He opened his contacts and scrolled to a number labeled “Professor Zhou—Neurology.” His finger hovered over the call button for a long time. In the end, he did not press it. He switched back to WeChat, found his chat with Su Man, and typed: Tomorrow morning at ten, pick up the data at the Information Department of Municipal Second Hospital. In the afternoon, go to the Provincial Hospital equipment department to submit the preliminary review materials. Also, help me check Director Zhao’s clinic hours in the neurology department at Provincial First Hospital.

Send. He turned off the screen and leaned back in the chair. The monitor’s ticking sounded regularly in the next room. He closed his eyes, and his mind began rehearsing every step of tomorrow’s route, the list of materials, and the resistance he might encounter. There was no way back. He could only move forward.

At 1:17 a.m., his phone vibrated. Su Man replied: Director Zhao has a VIP clinic next Wednesday morning. All slots are full. I’ll see if I can get an add-on through the society channel. Also, the hardware factory just messaged: the engineering unit has shipped, SF cold chain, arriving at seven tomorrow morning.

Lin Chen opened his eyes. Seven o’clock. He glanced at the wall clock. A little more than five hours remained.

He stood, took a jacket from the cabinet, and put it on. When his left foot touched the floor, it was still numb, but his gait had already steadied. He walked to the door, looked back at the sleeping Xiao Man, and gently pulled the door closed.

The corridor was empty. The sound-activated lights came on one by one with his footsteps. He slowly walked toward the stairwell, preparing to go down to the convenience store to buy two packets of instant coffee and a few slices of bread. On the ninety-day road, the first brick had only just been laid. And the real test was waiting for him tomorrow morning at ten, in the corridor on the third floor of the Information Department at Municipal Second Hospital.