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Improving Portable Oxygen Concentrator Performance through the development of a New Nasal Interface
- Author / Creator
- Christianson, Cole
Long term oxygen therapy (LTOT) is used to improve survival for patients with respiratory diseases who experience chronic respiratory failure. During LTOT, supplemental oxygen is supplied to patients from an oxygen source via cannula supply tubing. Portable oxygen concentrators (POCs) are a widely used oxygen source that often employ pulsed delivery modes to conserve oxygen. Pulsed delivery devices send a bolus of oxygen only during the inhalation phase of the user’s breath. In contrast, large amounts of oxygen are wasted during exhalation when using stationary, continuous flow sources. However, efficient pulsed delivery requires POCs to be triggered by patient inhalation. Triggering is known to fail during periods of quiet breathing, as occurs during sleep. As a result, the conventional method for delivering oxygen to LTOT patients includes a stationary, continuous flow oxygen source for sleep/rest, and a portable, pulsed flow oxygen source for activity. The need for multiple oxygen sources greatly limits patient autonomy and increases the cost of oxygen therapy. In the present thesis, a new nasal interface was developed to improve triggering of pulsed oxygen delivery from POCs. Ideally, this will eliminate the need for stationary oxygen sources in many cases, increasing patient autonomy and lowering the cost of LTOT.
The pressure drop across the cannula supply tubing, called the “signal pressure” herein, is monitored by the POC to determine when inhalation occurs. The new nasal interface is a tunable device with multiple settings used to control the signal pressure present during patient inhalation. In vitro experiments incorporating realistic nasal airway replicas and simulated breathing were conducted to test the performance of the new nasal interface. First, the signal pressure was measured over a range of constant inhalation flow rates with the nasal interface, a standard
cannula, or a flared cannula inserted into the nares of the nasal airway replicas. It was hypothesized that new nasal interface would provide higher signal pressures than the standard and flared nasal cannulas at a given flow rate for each airway replica. Next, POC triggering efficiency and the fraction of inhaled oxygen (FiO2) were evaluated for the nasal interface and both cannulas when connected to a commercial POC during simulated tidal breathing through the airway replicas. The simulated breathing patterns were representative of chronic obstructive pulmonary disorder (COPD) patients during sleep. It was hypothesized that using the new nasal interface would result in higher POC triggering efficiency and average FiO2 when compared to the standard and flared nasal cannulas.
At least one new nasal interface setting showed higher signal pressures than either nasal cannula for all flow rates and replicas tested. Also, in every simulated breathing scenario where the standard and/or flared cannula failed to trigger the POC, at least one new nasal interface setting successfully triggered. Average FiO2 was significantly higher for successful triggering cases than for failed triggering cases.
The new nasal interface is a tunable device designed to control the signal pressure present during patient inhalation. Using the new nasal interface during in vitro testing with realistic airway replicas improved triggering of pulsed oxygen delivery from a POC. This innovation presents a simple solution that could be used with commercially available POCs to reliably supply oxygen during periods of quiet breathing.
- Graduation date
- Fall 2021
- Type of Item
- Master of Science
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.