When COVID-19 hit the Western world, it exposed an already existing shortage of medical oxygen. This study focuses on designing an oxygen purifier capable of producing high-purity oxygen on-site using Pressure Swing Adsorption (PSA) technology. Although small-scale oxygen devices are available on the market, little public information exists about their dimensions and working conditions. This research fills this gap by making the design open source, providing a foundation for other technicians, particularly in the developing world, to implement on-site oxygen production, which is essential for surgical use. Building upon a previous multi-column project that achieved peak oxygen concentrations of 75%, this study develops and thoroughly tests a single-column system. By varying adsorption and desorption pressures, fluctuating mass flow, and different desorption times, a comprehensive overview of its performance is obtained. These results are integrated into a configuration scheme representing multiple single-column systems giving insights into the amount of columns and pumps necessary to meet a patients demand. Experimental results showed that for lithium-treated zeolite, an adsorption pressure of 2 bar is sufficient, as higher pressures do not significantly improve outlet concentration performance. During desorption, a substantial increase in oxygen concentration was observed when using 0.3 bar instead of 0.5 bar, with peak concentration differences of almost 20%. Desorption time also plays a significant role in both outlet concentration and the overall system configuration. It can be concluded that a single-column system does not meet the requirements to provide the necessary oxygen concentration for a patient. While peak concentrations of 70% were measured, achieving a sustained average of 70% would require higher peak concentrations. Future works should explore alternative setups, particularly those incorporating a recycling system to enhance oxygen concentration peaks.

Medical oxygen is crucial for effective treatment of patients, yet many low- and middle-income countries (LMICs) without a good healthcare infrastructure have been unable to provide sufficient oxygen therapy for years now. The COVID-19 pandemic highlighted the critical need for more oxygen, leading to supply shortages and rising prices even in developed countries. Currently, most medical oxygen is produced by a few large companies using centralized Cryogenic Air Separation Units (CAS). Pressure Swing Adsorption (PSA) offers a promising alternative, enabling local production of medical oxygen without reliance on suppliers. PSA leverages the pressure dependency of adsorption isotherms to selectively adsorb nitrogen, concentrating the oxygen.

This research has investigated the possibilities of designing a system that not only meets the specific oxygen demands of a Dutch hospital but also complies with the Dutch legal frameworks and forms an economically feasible case. A case study at Reinier de Graaf hospital (RdGG) in Delft used real oxygen consumption data. The applicable regulatory frameworks have been obtained by research in literature and with help of a representative at RdGG. For the technical design and optimisation, a numerical model of the PSA-cycle has been developed. This model is based on the Ideal Adsorption Solution Theory (IAST) and makes use of the Linear Driving Force model for adsorption kinetics. The model behaviour has been validated by experiments within a self-built, small-scale PSA-unit in the Process & Energy (P&E) lab. After this, the setup was scaled to hospital size within the model. A schematic PSA-plant has been designed based on the regulatory frameworks and system requirements which came from the numerical modelling. The economic viability has been addressed based on quotes, consumption data and electricity prices which were provided by RdGG.

Dutch regulations require hospitals to have three oxygen sources, each capable of independently providing the full design flow, with PSA units obligated to produce 93% oxygen concentration (± 3%) and meet strict impurity limits. To achieve the required oxygen purity, a vacuum pressure of 0.05 bar and an adsorption pressure of 6 bar with Oxysiv MDX zeolite are optimal. Depressurization should occur close to atmospheric pressure (1.05 bar) for efficiency. The adsorption column is most effective with a diameter-to-length ratio of 0.1 and a dimensionless time, tc, of 9.56 seconds for maximum oxygen production. The dimensionless time represents the time it takes for the gas to pass through the length of the column based on its inlet velocity.
The PSA unit at RdGG must handle a normal demand of 10 Nm³/h and a peak demand of 80 Nm³/h for three consecutive days. The second source can handle peak demand for three days, while the backup source can manage only 9 hours (tvital). If the PSA-storage has been depleted and the second source fails, tvital is the maximum refill time of the PSA-storage. This requires a production rate of 0.40 mol/s and two packages of storage cylinders (1.6 m³) which store the oxygen at 200 bar. This setup necessitates two 336L columns (3.5m height, 0.35m diameter, 0.36 m/s inlet velocity) and an air inlet flow of 126 m³/hr, supported by a vacuum pump and a compressor. The cycle steps for the adsorption, depressurization and vacuum (tAD = 79 s, tDP = 67 s, tVC = 112.1 s) total 258.7 s, allowing two columns to run in parallel. A 3 m³ air pressure vessel at 10 bar maintains PSA operation for three minutes during compressor disturbances. This setup achieves 93.61% oxygen purity with 41% recovery for 93% oxygen concentration, increasing to 58% recovery for 90% oxygen concentration. Each column requires 127 kg of zeolite, producing 5.75 mol O₂ kg⁻¹h⁻¹ (0.66 m³ O₂ kg⁻¹h⁻¹ at adsorption pressure), with an energy consumption of 29.38 kJ per mole of oxygen, totalling 255 kWh/tO₂.

The total investment for a PSA plant is estimated at 215,190 EUR, with fixed equipment costs of 176,800 EUR. Using straight-line depreciation over 20 years results in annual depreciation of 9,890 EUR. Annual costs also include energy and maintenance.
For an oxygen demand of 234 tons in 2023, the annual cost would be 25,590 EUR using PSA, significantly less than the current 60,840 EUR with the Liquefied Oxygen (LOX) installation. The levelized cost of oxygen over a period of 20 years for PSA is 128.61 EUR/ton, which is 2.1 times lower than the LCOO of LOX which is 270.52 EUR/ton.

The implementation of PSA plants for localized oxygen production in the Netherlands is both technically and economically feasible. A case study at Reinier de Graaf hospital shows significant cost savings compared to current liquid oxygen setups, with potential annual savings of 35,250 EUR. Required equipment is available and the setup size allows it to be installed inside or next to the hospital. Regulatory frameworks are already present and define clear requirements for using a PSA system as primary source. When implementing the right flow and pressure mechanisms the PSA plant can be connected to the current second and backup source, minimizing system adjustments for a smooth integration.

Future research should focus on several key areas to enhance the feasibility of using PSA in Dutch hospitals. Regulatory frameworks need approval or revision by experts in medical oxygen production. Analysing zeolite degradation and validating its performance are crucial for simulating the PSA unit's lifecycle. Improved modelling techniques, considering temperature variations, research on the validity of current assumptions and preventing backflow in the experimental setup will yield more accurate results. Additionally, industry practices should be reviewed to refine the proposed setup and obtaining precise cost estimates from quotes or hospital bills will improve the economic analysis.

Providing adequate healthcare in low- and middle-income countries (LMICs) faces significant challenges due to the frequent failure of medical devices, including hospital beds. These failures arise from environmental stressors, resource limitations, and design mismatches that fail to address the specific needs of LMIC settings. This thesis examines these challenges and develops a robust and modular solution tailored to these contexts, focusing on designing an appropriate backrest movement mechanism as a foundational component of a Universal Modular Hospital Bed.

Hospital beds are essential medical devices that provide quality patient care, comfort, and safety. However, existing designs often need to be more suitable for the harsh environmental conditions and resource constraints of LMICs, leading to high failure rates, compromised patient safety, and increased operational costs. This research addressed these gaps by designing a backrest movement mechanism that prioritizes durability, affordability, and contextual adaptability while laying the groundwork for a Universal Modular Hospital Bed suitable for diverse healthcare environments.

The study employs a comprehensive methodology integrating a systematic literature review, fieldwork, and a structured design process. The literature review identified key causes of medical device failures in low- and middle-income countries (LMICs), including environmental challenges, maintenance issues, and inadequate design considerations, which also apply to hospital beds. Fieldwork in Nepal, Suriname, and the Netherlands assessed hospital bed performance in different contexts. Drawing from these insights, a structured design process was used to generate, evaluate, and refine several concepts for a backrest movement mechanism. The chosen concept was then validated through prototyping and testing to ensure it met performance criteria, including robustness, safety, and ease of maintenance.

The research revealed that hospital beds in LMICs frequently fail due to high humidity, fluctuating temperatures, and unreliable infrastructure, compounded by limited access to spare parts and maintenance expertise. These challenges necessitate a context-sensitive design approach. The designed solution for the backrest movement mechanism employs a counterweight-based system that is manually operated, minimizing dependency on electricity and ensuring usability in resource-constrained settings. The design's modularity allows for easy maintenance, scalability, and integration with more advanced features, making it suitable for LMICs and high-income countries (HICs).

The backrest movement mechanism developed in this study addresses the critical challenges of hospital bed performance in LMICs. Its modular design ensures adaptability and compatibility with various healthcare settings, while its robust construction enhances durability and reduces maintenance costs. By focusing on local manufacturing and cost-effective materials, the design promotes accessibility and sustainability.

Future research should focus on scaling the modular design to incorporate additional features such as height adjustment and lateral movement systems. Collaborations with local manufacturers and healthcare providers are recommended to facilitate adoption and implementation. Long-term field testing will further validate the design’s efficacy and provide insights for continuous improvement. This study contributes significantly to developing medical devices that are both contextually appropriate and globally adaptable, addressing a critical gap in healthcare infrastructure in LMICs.

This thesis explores different ventilation systems used for operating rooms (OR). Entrainment test methods are used in most European standards to determine the protected zone whereas the air quality in the periphery is often excluded. Furthermore, these measurements are mostly carried out in an at-rest situation where intermittent sampling during operation should be required. Most ORs in the Netherlands have an air handling system with an ultra-clean ventilation system (UCV). ORs are energy-intensive departments, where air handling systems consume the most. Relatively simple adjustments can be made to the air handling system to reduce energy, such as expanding relative humidity limits and introducing operational clock times. Lowering outside air quantity has the biggest impact on energy reduction, lowering the OR classification the least. Reducing the air change rate in the OR from an ultra-clean to a generic OR will reduce the recovery degree and the local air change rate. Lowering the air change rate in operating rooms could harm comfort conditions and (ultra-clean) air quality. The capital and operational expenditures of air handling installations with an UCV-system are higher than those with a conventional system. The investment pays for itself when 2 to 4 surgical wound infections are prevented over the lifetime of the OR. The type of surgery should be a leading consideration in determining the typology of the air handling system and the type of air supply system. Absence of evidence that surgical site infections are prevented in ORs equipped with UCV-systems is not evidence that these are not prevented.

Background
Head-mounted augmented reality (AR) can be beneficial in orthopedic trauma surgery by projecting 3-dimensional (3D) holograms of preoperative imaging data, drilling or cutting planes, and osteosynthesis material, directly onto the surgeon’s field of view (FOV). For successful implementation of head-mounted AR in orthopedic trauma surgery, the surgeon’s experience is of utmost importance. This prospective clinical study aimed to evaluate the surgeon’s experience with head-mounted AR in orthopedic trauma surgery.
Methods
The Microsoft HoloLens 2 (Microsoft, Redmond, WA, USA) was used to project patient-specific 3D models of the patient’s fracture site as 3D holograms in the surgeon’s FOV during surgery of intra-articular fractures. The surgeon’s experience was recorded using the Simulator Sickness Questionnaire, Borg CR10 Scale, National Aeronautics and Space Administration Task Load Index, System Usability Scale, and a custom-made questionnaire.
Results
A total of 14 ORIF surgeries were performed while using a head-mounted AR device. Overall, surgeons were satisfied with AR HMDs (67.9 ± 22.3 (mean ± SD)) and wanted to use it again (70.0 ± 22.54 (mean ± SD)). Good results were reported regarding the usability of the AR HMD (65.7 ± 16.6 (mean ± SD)) and the interaction with 3D holograms 72.1 ± 15.8 (mean ± SD). However, the mental demand, size, and weight of the AR HMD were rated less favorable.
Conclusion
The surgeon’s experience with the intraoperative use of head-mounted AR in orthopedic trauma surgery is sufficient and head-mounted AR has great future potential in orthopedic trauma surgery. Future research has to focus on an ergonomic design of surgical AR HMDs, technological developments, a simple and fluent workflow, and proving clinical value of head-mounted AR.

Laparoscopy was shown to be highly effective in improving patients healthcare outcomes in comparison to traditional open surgery, ensuring faster healing, reduced scarring of the tissue and reduced pain. Laparoscopy has a great technological complexity, causing difficulties which make it of great interest to the engineering community. This research investigated whether colour filtering provides a better contrast during laparoscopic surgery, allowing for easier identification of tissues and vessels. A video of a gall bladder removal surgery was first carefully analysed for key moments when the hepatic vessels, gall duct and gallbladder vessels were visible. Three different reference images were selected from the original video and twelve different RGB (Red, Green, Blue) ratios were used to create new colour enhanced images for each of the selections in Darktable.