We designed a “Respiratory Health Study” platform application (Figure 1) that includes the following two parts: 1. smart devices measure physiological parameters including heart rate, blood oxygen, respiratory rate, body temperature, and cough sound; 2. the measured physiological parameters are uploaded to the cloud through the mobile app Respiratory Health Research; the system was designed to seek the deviations among the physiological parameters between pulmonary infections and healthy volunteers. Using this system, we established and verified the algorithm for pulmonary infection screening. All data were uploaded to the given research platform, and outside researchers had no access. The study was approved by the Ethics Committee of Chinese PLA General Hospital, Approval No. S2021-663-01. All participants signed informed consent before beginning the study. Further, this
study was registered in the Chinese Clinical Trial Registry, which was part of the International Clinical Trials Registry Platform of the World Health Organization (ChiCTR2100050843).
Establishment of the Pulmonary Infection Screening Algorithm
We enrolled 137 adult patients with suspected pneumonia hospitalized in the first and eighth medical center of the PLA General Hospital from June 1, 2021, to August 31, 2021, and 409 asymptomatic healthy controls for the training dataset. Data collection was based on a clinical questionnaire (Supplement 1), electronic disease history, and physiological parameter measurement using a wearable device. The smart device (Figure 2A, B) presented to the patients monitored, recorded, and analyzed their heart rate, respiratory rate, body temperature, cough sound, and blood oxygen saturation when worn; these data were used to develop a screening algorithm for pulmonary infection. The pneumonia diagnosis was made simultaneously by two independent physicians with respiratory specializations. Then, 137 patients who were confirmed to have a pneumonia diagnosis were used for the algorithm. Combined with 409 healthy volunteers, 545 sets of wearable data were collected (Figure 3).
Figure 1. Respiratory Health Research App and Huawei Smart Device
Figure 2. Collection of Cough Sound (A) and Physiological Parameters (B)
Validation of the Pulmonary Infection Screening Algorithm
To verify the accuracy of the algorithm, we recruited 75 hospitalized patients with suspected pneumonia and 85 healthy controls to form the validation dataset from the eighth medical center of the PLA General Hospital from September 10 to November 10, 2021. Three algorithms were generated: one only measured the cough sound (Algo-CS); another measured only the physiological parameters apart from the cough (Algo-PP), namely, heart rate, blood oxygen, body temperature, and respiratory rate; and the third combined the other two (Algo-CSPP). The diagnosis of pulmonary infection took the final clinical discharge diagnosis as the gold standard for comparison with the results of monitoring to verify the accuracy, specificity, and sensitivity of the algorithm.
Figure 3. Flow Diagram of the Study
Inclusion, Exclusion, and Diagnostic Criteria for Patients with Pneumonia
Inclusion criteria: 1. age ≥ 18 years; 2. computed tomography (CT) identification of suspected pulmonary lesions; and 3. patient compliance with wearing a smartwatch.
Exclusion criteria: 1. patient not diagnosed with pneumonia; 2. poor sensor signal quality on wearable device; and 3. patient withdrawal before completion of data collection.
The pneumonia diagnostic standard is as follows: 1. recent cough, expectoration, or aggravation of original respiratory disease, with or without sputum production, chest pain, tachypnea, dyspnea, wheezing, or hemoptysis; 2. fever; 3. physical findings such as lung consolidation and/or wet rales; 4. peripheral blood leukocytes > 10 × 109/L or < 4 × 109/L, with or without left shift of nucleus; and 5. chest imaging examination via CT that shows new patchy infiltration, consolidation of leaves or segments, ground glass observation, or interstitial changes, with or without pleural effusion. Pneumonia is defined as meeting either criterion 1 or 2 above, which excludes the pathophysiological changes caused by pulmonary edema, atelectasis, pulmonary eosinophilic infiltration, and pulmonary vasculitis.
Physiological Data Acquisition Using the Wearable Device
The acquisition of physiological signals by a wearable device was divided into two parts, and each patient collected the data for each part separately.
The first part was nocturnal monitoring. Patients wore their smart devices in bed to collect data over the entire sleep period, including data on the motion of the body measured using an accelerometer; heart rate, respiratory rate, and blood oxygen data measured via PPG signals; and body temperature data.
The second part involved spontaneous measurement data. Wearing a smart device, patients were asked to take a deep breath and then cough serially and vigorously three times, repeating the entire process twice. Next, they wore the smart device for 1 min to collect physiological data including blood oxygen, respiratory rate, heart rate, and body temperature.
After the data were acquired, the signal data were transferred through the Respiratory Health Research app to the research-specific platform.
Statistical Analysis
Continuous variables were tested for normality using the Kolmogorov–Smirnov test. Data with normal distribution were presented as mean±standard deviation (SD). Data with non-normal distribution were analyzed using the Mann–Whitney U test and presented as median (interquartile range (IQR)). Categorical variables were analyzed using Pearson’s chi-square test or Fisher’s exact test. A two-sided P-value <0.05 was considered statistically significant. Kappa coefficients were obtained, and statistical analysis of variables was performed using IBM SPSS Statistics, version 26.0 (SPSS Inc, Chicago, IL, USA).
The sensitivity and specificity were calculated based on the interpretation of the smart device compared to the physician’s diagnosis. 95% confidence intervals (CIs) were calculated using MedCalc 19.0.4 (MedCalc Software BVBA, Ostend, Belgium). ROC curve was pictured by Python 3.10.5(Python Software Foundation).