Development of a Low-Cost Pulse Oximeter for Taking Medical-Scientific Parameters to Monitor Remote Patients
, Sandra Sendra 1,*, Jaime Lloret 1, Jesus Tomas 1 and Jose Belda-Ramirez 2
Round 1
Reviewer 1 Report
Congratulations for your work. Topic of relevance, as at present, healthcare systems strategies trend to find more efficient pathways to attend society needs, and where home monitoring and telemedicine have an important role.
Comments by lines for consideration:
- line 17: "...such as SpO2, PR (bpm), RR/min and Pi (%), plethysmography wave, PVi (%), the shape...": because of, as depending on the reader ( more or less familiarized with medical terms), writting fullname of variables before writting abbreviations.
- line 37: "...between health professionals and patients and health professionals": I´m not sure if I understood appropiately, do you mean as a communication process, where information goes from (1) professional to patient and then (2) returns from patient to professional?
- line 15: "...the patientʹs oxygen pressure (SpO2) data is...": when talking about SpO2, not sure that the term "pressure" is adequate to use.
- On the methodology / ethical considerations side, maybe I havent found it in the document, any data regarding information to the subjects of the test, informed consent, etc. that may be relevant to conduct the research.
Author Response
Response for Reviewer 1:
Thanks for reviewing our paper. Thank you for your pertinent comments and detailed observations. These were really useful to improve the quality of our paper. Our responses are in line, starting with “Answer:”.
Congratulations for your work. Topic of relevance, as at present, healthcare systems strategies trend to find more efficient pathways to attend society needs, and where home monitoring and telemedicine have an important role.
Comment 1: - line 17: "...such as SpO2, PR (bpm), RR/min and Pi (%), plethysmography wave, PVi (%), the shape...": because of, as depending on the reader ( more or less familiarized with medical terms), writting fullname of variables before writting abbreviations.
Answer: We have added the full variable names on lines 17 and 18.
Comment 2: - line 37: "...between health professionals and patients and health professionals": I´m not sure if I understood appropiately, do you mean as a communication process, where information goes from (1) professional to patient and then (2) returns from patient to professional?
Answer: it is a little confusing. We have rewritten the line 37-38, as follow:” between health professionals and patients can be strengthened, generating a two-way process communication.“
Comment 3: - line 15: "...the patientʹs oxygen pressure (SpO2) data is...": when talking about SpO2, not sure that the term "pressure" is adequate to use.
Answer: we have reviewed the doccument to correct this term. Now, we are using “peripheral oxygen saturation (SpO2)” the first time the term appears and the abreviation of SpO2 in the rest of the document.
Comment 4: - On the methodology / ethical considerations side, maybe I havent found it in the document, any data regarding information to the subjects of the test, informed consent, etc. that may be relevant to conduct the research.
Answer: The people that participated in the experiment were researchers and volunteers from the same research group that were informed and they agreed. In fact, 5 of them are authors of this paper. In any case, the collected data has been anonymized to avoid any problem or correlation between data and person. We want to extend the experiments to real hospital environment where the consent of real patients will be required. To clarify this issue the following text has been added at the beginning od section 4 (page 12):
“ The 11 people that participated in the experiment were researchers and volunteers from the same research group that were informed and agreed to participate in it. Additionally, to avoid any problem of confidentiality or correlation between data and person, the collected data has been anonymized.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
I suggest the authors to continue their research.
Author Response
Response for Reviewer 2:
Thanks for reviewing our paper. Thank you for your comments. We will focus our efforts on designing a more complete system to enhance the results.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors have made a concise overview of the topic and a brief reference to existing literature. In general, the text is well structured and has clearly defined topics. Some comments for improvement:
1. As a general drawback, I could say that there is no reference to similar works that used wearables and deep learning methods (e.g. [1]) in different health monitoring areas:
[1] Daskalos A-C, Theodoropoulos P, Spandonidis C, Vordos N. Wearable Device for Observation of Physical Activity with the Purpose of Patient Monitoring Due to COVID-19. Signals. 2022; 3(1):11-28. https://doi.org/10.3390/signals3010002
2. Authors should provide a statement on the novelty of their work in the introductory section. As it s now it seems that an android application has been developed some time series for a commercial sensor have been presented. The authors should emphasize the part of software design or methodology (algorithmic or other) that is novel.
3. Similarly, authors should answer the following questions: What is the added value of their work? What is its impact?
4. The authors should explain why reverse engineering was needed. Was the protocol followed by the specific sensor different than the specified by the Bluetooth organization for the oxymeters?
5. In addition, is a detailed description of the BLE communication needed? It seems that this is information normally found in any relevant book/site.
6. Why do authors need to develop a new application? Does the sensor vendor provide an application for the device? Was this application limited compared to the developed one? What about other ready-made applications? for oxymeters?
7. Other than collecting and visualizing data does the application do other post-analyses? What about data storage? Do the application transfer the data to the cloud? Does it provide any triggering events/or alarms?
8. Do authors think that the data used are statistically important? It seems that only 5 patients were tested and results by one are presented.
9. What was the purpose of the tests? Since a commercial of the self-sensor is used did the authors want to validate its accuracy or efficiency or something else?
10. Authors should include the appropriate comments regarding the ethical committee agreement since human subjects were used for the trials.
11. Authors should provide in the concluding section the main outcome and approach an answer to the research question of their work.
Author Response
Response for Reviewer 3:
Thanks for reviewing our paper. Thank you for your pertinent comments and detailed observations. These were really useful to improve the quality of our paper. Our responses are in line, starting with “Answer:”.
The authors have made a concise overview of the topic and a brief reference to existing literature. In general, the text is well structured and has clearly defined topics. Some comments for improvement:
Comment 1: As a general drawback, I could say that there is no reference to similar works that used wearables and deep learning methods (e.g. [1]) in different health monitoring areas:
[1] Daskalos A-C, Theodoropoulos P, Spandonidis C, Vordos N. Wearable Device for Observation of Physical Activity with the Purpose of Patient Monitoring Due to COVID-19. Signals. 2022; 3(1):11-28. https://doi.org/10.3390/signals3010002
Answer: We have improved the related work section, including 3 new Works where authors present portable systems for measuring vital signs (reference B and C) and/or modern techniques to process the collected data (reference A). the following text has been added in section 2, pages 4 and 5.
“In 2018, Shanin et al. [B] proposed a portable electronic device to record the patient's health. This system was lightweight and inexpensive. Among the parameters subsequently monitored were the ECG, temperature, pressure and heart rate. For this, different types of sensors were used. After obtaining the data, they are sent to the cloud through the Internet of Things (IoT). In addition, it has GPS, which helps track the patient’s location during an emergency. It also includes the medical reports of each patient stored in the cloud.
Marathe et al. [C] also designed and developed a portable system to monitor patients. To do this, he used four different types of sensors integrated into a single system. This system is made up of an electrocardiogram (ECG) module, a blood pressure sensor, a temperature sensor, and a pulse oximeter module. Arduino has been used for system integration. The system collected the data obtained from the patient and obtained them via Wi-Fi to upload them to the cloud.
……
Finally, the use of this kind of devices are ussually combined with the use of neural networks of modern techinques of machine learing. This is the case of Daskalos et al. [A], who developed a wearable device to monitor patient body temperature and environmental conditions. In this way, the presence of COVID could be alerted through the developed application and the established alarm system. To rule out that the rise in body temperature was due to physical exercise, a "continuous displacement algorithm" based on an accelerometer was used. They used the BLE 5.0 Protocol for wireless data transmission and low power consumption. On the other hand, a 1D convolutional neural network (CNN) was obtained to classify whether the user has a fever or not, considering whether they are doing physical activity.”
[B] Shanin, F., Das, H. A., Krishnan, G. A., Neha, L. S., Thaha, N., Aneesh, R. P., ... & Jayakrishan, S. (2018, July). Portable and centralised e-health record system for patient monitoring using internet of things (IoT). In 2018 international CET conference on control, communication, and computing (IC4) (pp. 165-170). IEEE.
[C] Marathe, S., Zeeshan, D., Thomas, T., & Vidhya, S. (2019, March). A wireless patient monitoring system using integrated ecg module, pulse oximeter, blood pressure and temperature sensor. In 2019 International Conference on Vision Towards Emerging Trends in Communication and Networking (ViTECoN) (pp. 1-4). IEEE.
[A] Daskalos, A. C., Theodoropoulos, P., Spandonidis, C., & Vordos, N. (2022). Wearable Device for Observation of Physical Activity with the Purpose of Patient Monitoring Due to COVID-19. Signals, 3(1), 11-28.
Comment 2: Authors should provide a statement on the novelty of their work in the introductory section. As it s now it seems that an android application has been developed some time series for a commercial sensor have been presented. The authors should emphasize the part of software design or methodology (algorithmic or other) that is novel.
Answer: To clarify our contribution, the following text has been added at the end of the introduction section (page 2-3): “The application is also able to analyze the series of collected data to determine important aspects in patients such as the right and left slopes of the captured signals and the dicrotic fissure through the shape and the area under the curve.”
Comment 3: Similarly, authors should answer the following questions: What is the added value of their work? What is its impact?
Answer: We try to develop a low-cost and quick diagnostic device by using a commercial device and to provide the required “intelligence”, we develop the application and the different algorithms to extract the important information and to offer it to the user in a simple and easy way to interpret. To clarify our contribution, the following text has been added at the end of the introduction section (page 2-3):
“This fact makes it different from commercial devices and provides it the necessary characteristics to be used as a quick diagnostic device in hospital, domestic or geriatric environments.”
Comment 4: The authors should explain why reverse engineering was needed. Was the protocol followed by the specific sensor different than the specified by the Bluetooth organization for the oxymeters?
Answer: The problem with this device is not the sensor used to measure the vital signs. The difficulty is about how the device offers the results in a numerical format to process and take profit of them for other goals. This kind of commercial device presents closed protocols to avoid debugging itself. This difficult the Reading of data in any other way different from its application. we were able to capture Bluetooth traffic with a specific sniffer for smartphones. However, the content of its bytes was not initially significant. Therefore, we need to graphically represent what information the device was capturing and compare it with real shapes until we identify which parameter was being represented. With all this, the information on the content of the plots explained in the article is obtained.
To explain the reason to apply reverse engineering is explained in section 3.3 (page 8) with the following text:
“A commercial device usually preserves the code and technology by using closed protocols to avoid debugging itself and copy the product. This fact makes difficult the extraction of data in any other way different from its application. Therefore, the Bluetooth traffic is captured by a specific sniffer for smartphones. And the values are compared with real shapes to identify which parameters are represented.”
Comment 5: In addition, is a detailed description of the BLE communication needed? It seems that this is information normally found in any relevant book/site.
Answer: The paper includes a brief description (only some important details; the rest can be read in technical documentation) of how BLE Works and how this device uses the services and profiles to send the information. The following text is added in section 3.3 (page 8), after text added in comment 4:
”In addition to this, it is also important to know how services in BLE are used to encapsulate the information.”
Comment 6: Why do authors need to develop a new application? Does the sensor vendor provide an application for the device? Was this application limited compared to the developed one? What about other ready-made applications? for oxymeters?
Answer: The sensor has an extremely limited application from which it is impossible to obtain parameters such as photo-plethysmography wave, the dicrotic fissure shape, and the area under the curve. These parameters are important for the detection of many diseases, especially those related to the heart or respiratory system. Regarding the use of applications of other pulse oximeters, they cannot be used because each sensor needs its own application. On the other hand, the applications developed are not normally open access and specific licenses are needed to be able to use them. Our application is capable of processing the waveforms to interpret them and extract parameters such as the dicrotic fissure shape. To clarify it, the following text has been added at the end of related work (page 5):
“The presented devices present limited ranges of measurements and in most cases they use their own application. On the other hand, the applications developed are not normally open access and specific licenses are needed to be able to use them. Our application is capable of processing the waveforms to interpret them and extract parameters such as the photo-plethysmography wave, the dicrotic fissure shape, and the area under the curve, which are important parameters to detect many diseases, especially in problems related to the heart or respiratory system”
Comment 7: Other than collecting and visualizing data does the application do other post-analyses? What about data storage? Do the application transfer the data to the cloud? Does it provide any triggering events/or alarms?
Answer: Currently, we have a developed prototype that is capable of taking data, analyzing it, and offering it to users in an understandable format. Likewise, data storage is currently carried out on the device itself in a file in CSV format (as it is already mentioned in the text). It is currently a diagnostic device, instead of a remote monitoring device, so it has not currently been programmed to autonomously generate alarms. In future works, it is commented that we want to improve this device and integrate it into a more complex framework with other devices. The following text has been modified at the end of the conclusions and future work section (page 19):
“Additionally, it could be interesting to create a framework to include several devices like the one presented in this paper and others such as glucose meter or weighing machine. We finally consider the presence of an active connection to the cloud to centralize the data collection and to apply machine learning to enhance the clinical monitoring of patients and their progress.”
Comment 8: Do authors think that the data used are statistically important? It seems that only 5 patients were tested and results by one are presented.
Answer: As table 2 explains, the system is tested with 11 people of different ages and genders. However, we only provided the data of one of them just to show its operation. We have included the data of 3 other people that have collaborated in the test. Those figures replace figures from 16 to 19. As we can see the results are coherent, considering we have measured data from different people with different conditions. This is the new text and figures included. (Page 13 and 14):
“To simplify the explanations of the results, we have selected the data of patients from 1 to 4. Figures 15 to 19 show the parameters measured as a function of time. Figure 15 shows the plethysmography wave of patients from 1 to 4 for 10 seconds. Figure 16 shows the average value of SpO2 of patients from 1 to 4 for 250 seconds. Figure 17 shows the PR/min of patients from 1 to 4 for 250 seconds. Figure 18 shows the RR/min of patients from 1 to 4 for 250 seconds and, finally, Figure 19 shows the average value of PI of patients from 1 to 4 for 250 seconds.
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Figure 15. Plethysmography wave.
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Figure 16. Values of SpO2 measured for 250 seconds |
Figure 17. Values of PR/min measured for 250 seconds |
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Figure 18. Values of RR/min measured for 250 seconds |
Figure 19. Values of PI measured for 250 seconds |
Blood oxygen saturation values were correct in all cases. However, patient 1 was nervous or exercising due to tachycardia with highly variable respiration. The general conclusions are that those graphs do not show any pathology for patients from 1 to 4. “
Comment 9: What was the purpose of the tests? Since a commercial of the self-sensor is used did the authors want to validate its accuracy or efficiency or something else?
Answer: The objective of performing these tests was to demonstrate that our application and algorithm was capable of extracting the data from Bluetooth frames and processing them, to obtain the parameters of SpO2, PR (bpm), RR/min, and Pi (%) which are directly provided by the device and the plethysmography wave, the PVi (%), the shape of the dicrotic fissure, and the area under the curve which are indirectly calculated by our algorithm.
The following text is included at the beginning of section 4 (page 13): “ Through the test of our system, we want to demonstrate that the device together with the algorithm are capable of extracting the data from Bluetooth frames and processing them, to obtain the parameters of SpO2, PR (bpm), RR/min, and Pi (%). These parameters are directly provided by the device while the plethysmography wave, the PVi (%), the shape of the dicrotic fissure, and the area under the curve are indirectly calculated by our algorithm.”
Comment 10: Authors should include the appropriate comments regarding the ethical committee agreement since human subjects were used for the trials.
Answer: The people that participated in the experiment were researchers and volunteers from the same research group that were informed and they agreed. In fact, 5 of them are authors of this paper. In any case, the collected data has been anonymized to avoid any problem or correlation between data and person. We want to extend the experiments to real hospital environment where the consent of real patients will be required. To clarify this issue the following text has been added at the beginning of section 4 (page 12):
“ The 11 people that participated in the experiment were researchers and volunteers from the same research group that were informed and agreed to participate in it. Additionally, to avoid any problem of confidentiality or correlation between data and person, the collected data has been anonymized.”
Comment 11: Authors should provide in the concluding section the main outcome and approach an answer to the research question of their work.
Answer: The answer to our research question is that using commercial devices that a priori do not offer more specific or useful medical data (such as plethysmography waveform, PVi (%), dicrotic fissure shape, and area under the curve) to determine certain medical problems, with the help of correct processing of the raw data offered by the pulse oximeter, we have been able to extract them. Likewise, the Android application offers the user a simple interface that allows any user without extensive knowledge to read them. In addition, the classic parameters, SpO2, PR/min (bpm), RR/min, and Pi (%) are maintained. With this, we create cheaper diagnostic systems that will allow developing countries and users with few resources to make use of specific devices for monitoring the progress of certain diseases. The following text has been added in the conclusion section (page 17-18):
“As general conclusion, we can say that using commercial devices that a priori do not offer more specific or useful medical data to determine certain medical problems, we have been able to process the raw data offered by the commercial pulse oximeter to obtain useful information like the plethysmography waveform, PVi (%), dicrotic fissure shape, and area under the curve while maintaining the classic parameters of SpO2, PR (bpm), RR/min, and Pi (%). Finally, the Android application offers the user a simple interface that allows any user without extensive knowledge to read them. With this, we create cheaper diagnostic systems that will allow developing countries and users with few resources to make use of specific devices for monitoring the progress of certain diseases.”
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The manuscript has been improved according to previous comments.
