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University of California, San Diego
Mechanical and Aerospace Engineering
MAE 156B: Senior Design Project
Project Background
Acute respiratory failure (ARF) is a significant risk when transporting patients from the Operating Room (OR) to the Post-Anesthesia Care Unit (PACU) or other hospital locations. Currently, patients are typically not monitored during this transport period. Anesthesia providers are often forced to rely on subjective, non-standardized methods—such as looking for chest rise or "fogging" in the mask—to assess breathing. These methods are unreliable, especially while the provider is actively maneuvering a gurney. Consequently, respiratory distress can go undiagnosed until it is too late, leading to significant morbidity and mortality.
Fig. 1 - Final device prototype mounted on intravenous (IV) pole.
Project Overview
The goal of this project is to create a portable carbon dioxide (CO2) monitor (Fig. 1) for anesthiosologists and other healthcare providers to quantitatively monitor end-tidal CO2 (ETCO2) levels throughout transport from the OR to other hospital locations. This involves the full product lifecycle from design, fabrication, testing, and validation for each of the identified four major subsystems.
Casing and IV Pole Clamp (Fig. 2)
Sensors and Pneumatics (Fig. 3)
Electronics (Fig. 4)
Graphical User Interface (GUI) and Processing (Fig. 5)
Fig. 2 - Casing.
Fig. 4 - Pneumatics diagram.
Fig. 4 - Electronics overview.
Fig. 5 - GUI overview.
Description of Design Solution
The CO2-Go system demonstrated successful fulfilment of all initial design requirements. The waveform is clean enough to provide an easy reading to an anesthesiologists and the capability to detect pathology from the waveform visually. This satisfies the initial requirement for detecting pathology in the waveform. The casing was also tested in a one meter drop test successfully, however the electronics were not implemented in the casing during the test to reduce potential loss of expensive components. The device successfully passes all design criteria and was determined a success by the project sponsors during OR testing and final review.
The system altogether fit within a 7”x7” footprint and is able to easily clamp onto an IV pole. All electronics, sensors, and pneumatics are contained within the 3D printed casing and all connections use universal luer connectors to integrate with existing medical systems. Everything runs on an internal battery contained within the casing. The display is centered on the front of the casing. The design solution and usage is shown in Fig. 6 to the right.
Fig. 6 - Design solution and usage flow chart.
Performance Results
156B Objective
The overall goal of creating an integrated, portable ETCO2 module for use in hospitals during patient transit will be achieved by splitting the functionality into four distinct major subsystems and demonstration of full, holistic operation at the end with each interfacing with the other.
The CO2 sensing subsystem involves a circuit for data collection of the CO2 levels in the patient's breath using an non-dispersive infrared (NDIR) CO2 sensor, a pressure sensor, and temperature/humidity sensing.
The software and data processing subsystem involves processing of noisy sensor data, generation of an interpretable waveform on a screen, and pulsing/sampling logic for the pump and sensors.
The pump and battery subsystem involves a diaphragm pump for consistent volumetric airflow through the sensing chamber, the rechargeable battery power source, and the components required for voltage/current division across subsystems.
The casing and clamp subsystem involves an easy-to-use mechanical clamp for rapid attachment/detachment of the monitor to the IV pole of a hospital gurney, a case to hold all electronics and flow components in one integrated module.
Final Presentation
Poster
Images of Progress Achieved
Narrated Video Showing Design
(Risk Reduction)
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