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CHAPTER 14:

DESIGN AND DEVELOPMENT OF A COST-EFFECTIVE CPAP DEVICE WITH OXYGENATION AND AN AUTOMATED MDI DELIVERY SYSTEM

Muhammad Arshad Eyasim, Sudesh Sivarasu

ORCID ID: 0000-0001-9571-6586, 0000-0002-0812-568X

Division of Biomedical Engineering

Department of Human Biology

University of Cape Town

Western Cape

South Africa


ABSTRACT

Patients suffering from Covid-19 and Chronic Obstructive Pulmonary Disease (COPD), or asthma comorbidities receive Continuous Positive Airway Pressure (CPAP) therapy as one of the treatment options. They additionally require regular administration of a bronchodilator medication using a Metered Dose Inhaler (MDI) to open the airways of the lungs to make breathing easier. However, some challenges have been identified with existing techniques of using MDI with CPAP; a nurse must remain at the bedside to manually time the actuations and actuate the MDI. One of the current methods does not provide Positive End-Expiratory Pressure (PEEP), thereby reducing the medication's effectiveness. The current global Covid-19 pandemic has resulted in the limited number of Intensive Care Unit (ICU) resources such as bedside nurses and ventilators. Therefore, a need for a device that can provide oxygenation and automated MDI medication delivery has been identified to reduce the number of ICU admissions, increase the effectiveness of MDI treatment, and reduce the number of patients requiring intubation. This design project entails the development of a prototype as well as verification and validation tests. The prototype was built by focusing on the functional blocks and iterating the core component of the design. The prototype was then verified and validated. It was found the Proof of Concept of the device meets the requirements and works as intended. In conclusion, the project highlights how the needs are met and the drawbacks of the design are identified. Recommendations are then made on the improvement of the device's functionality and usability features.

Keywords: CPAP, MDI, Bronchodilator, Automated, Covid-19, COPD, Asthma

NOMENCLATURE

COPD Chronic Obstructive Pulmonary Disease
CPAP Continuous Positive Airway Pressure
FiO2 Fraction of Inspired Oxygen
ICU Intensive Care Unit
MDI Metered Dose Inhaler
PEEP Positive End-Expiratory Pressure

INTRODUCTION

The number of cases in the current global Covid-19 pandemic is on the rise, and many of these patients have COPD or asthma comorbidities. Pneumonia and Hypoxemia in Covid-19 patients with pre-existing illnesses such as COPD or asthma are the disease state fundamentals of interest within the target group. Many people in the target group require oxygen therapy, such as CPAP therapy, as well as the delivery of a bronchodilator using an MDI. The MDI delivery is currently conducted using two methods. The first technique, shown in Figure 1, employs an inline MDI T-piece adaptor, which requires a nurse to manually time and actuate the MDI. The second approach, shown in Figure 2, necessitates the removal of the mask to administer the drug orally using an MDI spacer.

Figure 1: Inline MDI T-piece adapter (Armstrong Medical, 2021)
Figure 1: Inline MDI T-piece adapter (Armstrong Medical, 2021)

Figure 2: MDI spacer (Doyle & McCutcheon, 2021)
Figure 2: MDI spacer (Doyle & McCutcheon, 2021)

A study on the severity and mortality associated with COPD and smoking in patients with Covid-19 found that COPD patients had a higher severity risk of 63% compared to patients without COPD with a severity risk of 33.4%, and Covid-19 patients with COPD have a higher mortality rate of 60% (Alqahtani et al., 2020). Africa has the second highest prevalence of COPD in the world and Cape Town has the highest COPD prevalence in Africa (Blanco et al., 2019). The symptoms are worse for people who already have asthma when they are infected with the Covid-19 virus (Wiginton, 2021). Based on a recent study by Naidoo & Naidoo (2021) on scarce ICU resources, they found that approximately 16% of Covid-19 infected cases require ICU admission and that this percentage in a South African setting will put additional pressure on the country’s ICU resources which are already in usage by other patients with medical conditions that require ICU support. Thus, the need statement formulated to address the problem identified is a way of addressing the delivery of MDI medication using a CPAP device by integrating an automated MDI delivery system, allowing for a decreased number of ICU admission, increased effectiveness of MDI treatment and a decreased number of patients requiring intubation.

Currently, there is no commercial solution available to address the identified issue. The proposed solution is a CPAP device with oxygenation and an automated MDI delivery system. This device allows users to set CPAP and MDI settings such as inspiratory pressure, dosing frequency, and dosing interval. A prototype is to be built, verified and validated. The prototype must meet all user and design requirements, identified needs, and Proof of Concept.

MATERIALS AND METHODS

The design thinking 6-3-5 brainstorming method (Wilson, 2013) was used amongst six participants to ideate on various components of the device. The best ideas were collated, and nine concepts were generated. A final concept was obtained after selecting and screening the concepts.

i. Functional Block of Prototype

After obtaining the final concept, functional blocks were identified based on the needs criteria for the preliminary step in the prototype development. The functional blocks are: a fan that can provide adjustable continuous pressure, a way to adjust and determine Fraction of Inspired Oxygen (FiO2), an automated MDI delivery system, an easily accessible and reloadable medication canister, supplied air must be warmed and humidified, the device must provide PEEP and have safety features.

ii. Technical Specifications

The technical specifications of the prototype are drawn using the specifications prescribed by the World Health Organization for non-invasive ventilators for Covid-19 (2020) as shown in Table 1.

Table 1: Technical specifications

iii. Design Iterations

RESULTS AND DISCUSSIONS

i. Verification and Validation

ii. Proof of Concept and Test results

The Proof of Concept of the prototype was met by verifying and validating whether the device can provide continuous pressure, actuate the MDI and adjustable FiO2 based on user input. The maximum inspiratory pressure range that can currently be achieved with the device is 3 to 13 cmH2O. It was also found that with increasing pressure the pressure at the mask is slightly lower than the output of the device. This pressure drop is expected and can be calibrated by increasing the output pressure of the device slightly higher than the user input pressure so that the pressure at the mask is the same as the user input. The MDI actuation device was found to be working effectively and accurately in respect to time. Theoretically, it was verified that the adjustable FiO2 will work. The test was then validated showing that the verification test and the validation test graphs are very similar. Thus, the working principle of this concept works. Hence, the Proof of Concept of the device was successfully met.

COSTING

The total cost of prototyping was R5 667. Considering the mass production of the device and various parts, the cost is expected to be reduced to R 4000. Thus, with a 25% markup, the retail price of the device to distributors will be R5 000. The developed device is cheaper than traditional CPAP devices without oxygenation, which cost upwards of R 8 900, but it is more expensive than CPAP devices that use air entrainment such as the Nippy 3+ or CPAP masks that cost upwards of R 4 800 and R 1 200 respectively (Afrimedics, 2021; Dotmed, 2021; Medex Supply, 2021). The device developed, which integrates an automated MDI delivery system, is thus considered to be cost-effective compared to both the cheaper and more expensive CPAP devices as they do not include the MDI delivery system. The cheaper CPAP devices have many limitations such as restricted flow rate in the Nippy 3+, and no display to monitor various parameters and fixed FiO2 with CPAP masks.

DRAWBACKS

The drawbacks of the prototype are that the accuracy and sensitivity of the pressure sensors are unreliable, the fan specifications are too low for this application, the prototype is very large, it needs to be reset at power up for the Arduino to work and the reloadability of the MDI canister is not user-friendly.

RECOMMENDATIONS

Based on the prototype, the following recommendations on the improvement of the device are made: a way to substitute the cap needed for the MDI canister by using a different cam design that will not get jammed in the canister’s concave end, a standard off-the-shelf flowmeter can be used for better accuracy and reliability, the flow dynamics of the device must be analysed and improved to increase the efficiency of the pressure delivery, the sliding door can be motorised for ease of use and to ensure it is closed fully, the reloading of the canister can also be improved by using an actuator that pushes the canister out for reloading and lastly, the device can be improved to detect inspiration and then actuate the MDI after the interval set.

CONCLUSION

A Proof of Concept for a CPAP device with oxygenation and an automated MDI delivery system has been successfully designed and developed. The device has been tested and validated to show that it works as intended. Based on its additional features, the device is cost-effective compared to existing solutions. This project presented a methodology that can be used for further iterations to create improved commercial solutions. Further improvements were recommended to adapt the design to the global market in terms of functionality and ease of use.

ACKNOWLEDGEMENTS

The authors would like to thank members of the Medical Devices lab at the University of Cape Town and merSETA for the ViroVent Innovation Challenge.

REFERENCES

Afrimedics. (2021). Portable auto Cpap Machine DS-6 AUTO CPAP. Retrieved 25 September 2021, from https://www.afrimedics.co.za/product/portable-auto-cpapmachine- ds-6- autocpap/?sfdr_ptcid=13621_617_673695122&sfdr_hash=d18ffb68f5f2948fd794621 db2bb5562

Alqahtani, J., Oyelade, T., Aldhahir, A., Alghamdi, S., Almehmadi, M., & Alqahtani, A. et al. (2020). Prevalence, Severity and Mortality associated with COPD and Smoking in patients with COVID-19: A Rapid Systematic Review and Meta- Analysis. PLOS ONE, 15(5), e0233147. doi: 10.1371/journal.pone.0233147

Armstrong Medical. (2021). Spirale® Drug Delivery System. Retrieved 20 September 2021, from https://www.armstrongmedical.net/product/spirale/

Blanco, I., Diego, I., Bueno, P., Casas-Maldonado, F., & Miravitlles, M. (2019). Geographic distribution of COPD prevalence in the world displayed by Geographic Information System maps. European Respiratory Journal, 54(1), 1900610. doi: 10.1183/13993003.00610-2019

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Doyle, G., & McCutcheon, J. (2021). Clinical Procedures for Safer Patient Care. Retrieved 20 October 2021, from https://opentextbc.ca/clinicalskills/chapter/inhaled-and-topical-medications/

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Medex Supply. (2021). Flow Safe II CPAP with large adult mask 5/Box. Retrieved 16 October 2021, from https://medexsupply.com/flow-safe-ii-cpap-with-large-adult-mask-5-box/?pid=104260

Naidoo, R., & Naidoo, K. (2021). Prioritising ‘already-scarce’ intensive care unit resources in the midst of COVID-19: a call for regional triage committees in South Africa. BMC Medical Ethics, 22(1). doi: 10.1186/s12910-021-00596-5

Technical specifications for invasive and non-invasive ventilators for COVID- 19. Apps.who.int. (2020). Retrieved from https://apps.who.int/iris/rest/bitstreams/1275111/retrieve

Wiginton, K. (2021). Coronavirus and Asthma. WebMD. Retrieved from https://www.webmd.com/asthma/covid-19-asthma.

Wilson, C. (2013). Using Brainwriting For Rapid Idea Generation. Smashing Magazine. Retrieved from https://www.smashingmagazine.com/2013/12/using-brainwriting-for-rapid-idea-generation/