Bio-signal Processing Research Group (BSPRG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor Bahru, Johor, Malaysia.
Emergency Department, Hospital Pulau Pinang, Pinang, Malaysia.
J Breath Res. 2018 Jan 4;12(2):026003. doi: 10.1088/1752-7163/aa8dbd.
The development of a human respiration carbon dioxide (CO) measurement device to evaluate cardiorespiratory status inside and outside a hospital setting has proven to be a challenging area of research over the few last decades. Hence, we report a real-time, user operable CO measurement device using an infrared CO sensor (Arduino Mega2560) and a thin film transistor (TFT, 3.5″), incorporated with low pass (cut-off frequency, 10 Hz) and moving average (span, 8) filters. The proposed device measures features such as partial end-tidal carbon dioxide (EtCO), respiratory rate (RR), inspired carbon dioxide (ICO), and a newly proposed feature-Hjorth activity-that annotates data with the date and time from a real-time clock, and is stored onto a secure digital (SD) card. Further, it was tested on 22 healthy subjects and the performance (reliability, validity and relationship) of each feature was established using (1) an intraclass correlation coefficient (ICC), (2) standard error measurement (SEM), (3) smallest detectable difference (SDD), (4) Bland-Altman plot, and (5) Pearson's correlation (r). The SEM, SDD, and ICC values for inter- and intra-rater reliability were less than 5% and more than 0.8, respectively. Further, the Bland-Altman plot demonstrates that mean differences ± standard deviations for a set limit were 0.30 ± 0.77 mmHg, -0.34 ± 1.41 mmHg and 0.21 ± 0.64 breath per minute (bpm) for CO, EtCO and RR. The findings revealed that the developed device is highly reliable, providing valid measurements for CO, EtCO, ICO and RR, and can be used in clinical settings for cardiorespiratory assessment. This research also demonstrates that EtCO and RR (r, -0.696) are negatively correlated while EtCO and activity (r, 0.846) are positively correlated. Thus, simultaneous measurement of these features may possibly assist physicians in understanding the subject's cardiopulmonary status. In future, the proposed device will be tested with asthmatic patients for use as an early screening tool outside a hospital setting.
在过去几十年中，开发一种能够在医院内外评估心肺状态的人体呼吸二氧化碳（CO）测量设备一直是一个具有挑战性的研究领域。因此，我们报告了一种使用红外 CO 传感器（Arduino Mega2560）和薄膜晶体管（TFT，3.5 英寸）的实时、用户可操作的 CO 测量设备，该设备结合了低通（截止频率，10 Hz）和移动平均（跨度，8）滤波器。该设备可测量部分潮气末二氧化碳（EtCO）、呼吸率（RR）、吸入二氧化碳（ICO）和一个新提出的特征——Hjorth 活动等特征，该特征用实时时钟的日期和时间注释数据，并存储到安全数字（SD）卡上。此外，它在 22 名健康受试者上进行了测试，使用（1）组内相关系数（ICC）、（2）标准误差测量（SEM）、（3）最小可检测差异（SDD）、（4）Bland-Altman 图和（5）Pearson 相关（r）来确定每个特征的性能（可靠性、有效性和关系）。内部和外部观察者的可靠性的 SEM、SDD 和 ICC 值均小于 5%，大于 0.8。此外，Bland-Altman 图表明，在设定的限值内，CO、EtCO 和 RR 的平均差异±标准偏差分别为 0.30±0.77 mmHg、-0.34±1.41 mmHg 和 0.21±0.64 次/分钟（bpm）。研究结果表明，所开发的设备具有高度的可靠性，能够为 CO、EtCO、ICO 和 RR 提供有效的测量值，并可在临床环境中用于心肺评估。这项研究还表明，EtCO 和 RR（r，-0.696）呈负相关，而 EtCO 和活动（r，0.846）呈正相关。因此，同时测量这些特征可能有助于医生了解受试者的心肺状况。在未来，将在哮喘患者中测试该设备，以便在医院外环境中用作早期筛查工具。
