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Abstract

Respiratory conditions impact the quality of life for over 400 million people worldwide. Positive pressure ventilation, like BiPAP (Bilevel Positive Airway Pressure) or CPAP (Continuous Positive Airway Pressure) are typically used to manage dyspnea and hypercapnia; in severe or emergent cases, intubation may be necessary. Patients often experience discomfort and side effects including lacerations (caused by wearing a tight-fitting face mask over the nose and mouth), bloating, and nasal congestion. Severe complications like lung injury or barotrauma may occur, owing to unnaturally elevated inspiratory pressures or increased tidal volume. Developing a breathing assist device that can support natural breathing in a comfortable and unobtrusive way has the potential to improve quality of life for affected individuals. This thesis explores the development of the Flexovent, a flexible wearable negative pressure ventilation device that can be worn around the chest and abdomen like a vest. Negative pressure ventilation supports natural breathing motion and is less likely to cause severe complications, even with long-term use. The Flexovent is a relatively small (OD = 340 mm) and lightweight exoskeleton structure (< 6 kg), consisting of a series of flexures that enable circumferential contraction leading to radial change of over 30 mm without buckling. Each flexure is a combination of elastic beams and curved rigid plates. When the beams shear, the rigid components slide closer together. Using a compact motor, the contraction and relaxation cycle time is within the typical range of breathing at rest (12-20 cycles per minute). The Flexovent can vary pressure by ~ 1 kPa. Generation of -0.3 kPa was demonstrated in a small-scale model (ID = 100 mm, L = 100 mm). Further work is required to sufficiently seal the exoskeleton structure and generate negative pressure in the range of -1 kPa to -5 kPa, prior to trials with healthy volunteers.