The surge in COVID-19 cases leading to hospitalizations around the world quickly depleted hospital resources and reserves, forcing physicians to make extremely difficult life-or-death decisions on ventilator allocation between patients. Leaders in academia and industry have developed numerous ventilator support systems using both consumer- and industry-grade hardware to sustain life and to provide intermediate respiratory relief for hospitalized patients. This book is the first of its kind to discuss the respiratory pathophysiology underlying COVID-19, explain ventilator mechanics, provide and evaluate a repository of innovative ventilator support devices conceived amid the pandemic, and explain both hardware and software components necessary to develop an inexpensive ventilator support device. This book serves both as a historical record of the collaborative and innovative response to the anticipated ventilator shortage during the COVID-19 pandemic and as a guide for physicians, engineers, and DIY'ers interested in developing inexpensive transitory ventilator support devices.
Author(s): Amir A. Hakimi, Thomas E. Milner, Govind R. Rajan, Brian J-F Wong
Publisher: Springer
Year: 2022
Language: English
Pages: 266
City: Cham
Preface
Contents
About the Editors
Chapter 1: Establishment of the Bridge Ventilator Consortium
Part I: Lung Physiology and Ventilator Basics
Chapter 2: An Overview of Lung Anatomy and Physiology
Lung Anatomy
Trachea and Bronchi
Pulmonary Neurovasculature
Lung Mechanics
Compliance and Elastance
Airway Resistance and Drive Pressure
Work of Breathing
Gas Exchange
Ventilation
Perfusion
Dead Space
Shunt
A-a Gradient
V/Q Mismatch
Carbon Dioxide
Bohr Effect
O2 Delivery to Tissues
Haldane Effect
Oxyhemoglobin Dissociation Curve
Hypoxemia vs. Hypoxia
Altitude Effects on Gas Exchange
Normal Physiologic Parameters
References
Chapter 3: Respiratory Mechanics and Ventilation
History of Mechanical Ventilation
Noninvasive Positive-Pressure Ventilation
Positive-Pressure Invasive Ventilators
Basics of Mechanical Ventilation
Ventilator Settings
Reference
Chapter 4: Mechanical Ventilators and Monitors: An Abridged Guide for Engineers
Who Uses a Ventilator? What Level of Training Is Needed?
Which Patients Benefit from This Device?
Monitoring Physiologic Parameters
Oxygenation and Pulse Oximetry
Carbon Dioxide and Capnography
Volume Capnography
Transcutaneous CO2 Monitoring
Arterial Blood Gas vs. Venous Blood Gas
Airway Pressures
Peak Inspiratory Pressure vs. Plateau Pressure
Auto-PEEP vs. Extrinsic PEEP
Respiratory Rate
Respiratory Set vs. Actual Rate
Ventilator Sensed Rate
Humidity (Heat and Moister Exchangers vs. Heated Humidifier vs. Heated-Wire Circuits)
Tidal Volume
Patient-Ventilator Synchrony Monitoring
Patient-Ventilator Synchrony/Dyssynchrony Introduction
Ineffective Triggering
Double Triggering and Reverse Triggering
Flow Dyssynchrony and Auto-Triggering
Setup and Form Factor of Contemporary Ventilators
References
Chapter 5: An Overview of Mechanical Ventilation and Development of the UC San Diego MADVent
Introduction
Spontaneous Respiration
The Purpose and Basic Functions of a Ventilator
The Evolution of Assisted Ventilation
Types of Modern Ventilation
CMV: Continuous Mandatory Ventilation
A/C: Assist/Control Ventilation
IMV: Intermittent Mandatory Ventilation
SIMV: Synchronized Intermittent Mandatory Ventilation
S/T: Spontaneous/Timed Ventilation
CSV: Continuous Spontaneous Ventilation
APRV: Airway Pressure Release Ventilation
CPAP: Continuous Positive Airway Pressure
Pressure Support (PS)
Patient-Triggered
Ventilator-Initiated
Time-Terminated
Volume-Targeted
Designing Ventilators for Clinical Use
Regulations and Standards
IEC 60601-1:2005+AMD1:2012+AMD2:2020 CSV
IEC 60601-1-11
ISO 18652
ISO 5356-1
21 CFR Part 820 or ISO 13485
ISO 14971
IEC 62304:2015
AAMI TIR69:2017 and ANSI/IEEE C63.27:2017
ISO 7010
Example Design: Inexpensive Bag-Based Ventilator
Conclusions
References
Chapter 6: An Introduction to Noninvasive Ventilation
Introduction
High-Flow Nasal Cannula
HFNC in COVID-19 Patients
CPAP
CPAP in COVID-19 Patients
BiPAP
BiPAP in COVID-19 Patients
Survival Mode with Noninvasive Ventilation in a Resource-Limited Setting
References
Chapter 7: Noninvasive Ventilation and Mechanical Ventilation to Treat COVID-19-Induced Respiratory Failure
Introduction
Noninvasive Ventilation (NIV)
Prone Positioning
Mechanical Ventilation
Tracheostomy
References
Part II: SARS CoV-2 Transmission and Innovative Protective Barriers
Chapter 8: COVID-19 Pathophysiology and COVID-19-Induced Respiratory Failure
Pathophysiology of COVID-19
COVID-19-Induced Respiratory Failure
References
Chapter 9: Spread of COVID-19 and Personal Protective Equipment
Spread of COVID-19
Personal Protective Equipment and Its Role in Preventing Spread Among Healthcare Workers and Communities
References
Chapter 10: An Overview of Personal Protective Equipment and Disinfection
Protection of Personnel
Environmental Protection
References
Part III: Bridge Ventilator Design and Components
Chapter 11: What Is a Bridge Ventilator? Basic Requirements, the Bag Valve Mask, and the Breathing Circuit
Chapter 12: Hardware Considerations
Evolution of the Actuating Arm
Printed Circuit Board (PCB) Design
Optical Reflectors
Pulse with Modulation (PWM) Board
Power Supply
Pressure Transducers
User Input Controls
High-Priority Alarms
Overpressure
Underpressure
Loss of Power
Low-Priority Alarms
Tidal Volume Out of Spec
Motor End of Life
Outline of Motor Power Requirement Estimate
Energy/Power into Ambu Bag
Power Loss In 10 ft. Long Tube
Power/Energy Loss in Pulmonary Resistance
Energy/Power for Lung Compliance
Reference
Chapter 13: Software Considerations
Software Overview
Analog Input Acquisition
Hardware and Timer Interrupts
PWM Timer and Encoder Interrupts
Motor Control Task
Alarm Class
Display Class
Flash Storage
Watchdog Timer
Doxygen Documentation
Chapter 14: Development of Emergency Resuscitators: Considerations for Mechanical and Electrical Components
Introduction
Motor Systems
Stepper Motor
Basic Principles of Operation
Stepper Motor Operation
Encoders
Servomotor
Motor System Considerations and Comparison
Conclusion
References
Chapter 15: Incorporating Patient Assist Mode: The ABBU Experience
ABBU Synchronous Operation Testing
Chapter 16: A Qualitative Overview of Emergency Resuscitators Approved in the COVID-19 Pandemic
Introduction
Resuscitators vs. Ventilators
SecondBreath LLC
Coventor Adult Manual Resuscitator Compressor
Umbulizer
PVA Prevent (RECALLED)
Spiro Wave
Virgin Orbit Resuscitator
Venti-Now
Fitbit Flow
Air Boost Austin P51
Apollo ABVMN
LifeMech A-VS
Conclusions and Parting Design Considerations
References
Part IV: Regulatory Factors and Device Testing
Chapter 17: Innovation and Regulation: The FDA’s Response to the COVID-19 Pandemic
Timeline of Initial SARS-CoV-2 Response
Implementation of the Emergency Use Authorization
Ventilator and Ventilator Accessory EUAs
Ventilators
Ventilator Tubing Connectors
Challenges Associated with the FDA’s Emergency Use Authorization
Availability of Information to Clinicians
Lack of Data on Patient Use
Future Directions
The Future of the FDA Umbrella EUA
The Response to Future Pandemics
References
Chapter 18: Regulatory Considerations for Bridge Ventilators
Medical Devices 101
What Is a Medical Device?
Medical Device Design
Herding Cats (Creating the Team)
Mindset
Team of Many Hats (Exploit Previous Experience)
Bells and Whistles: How Much Is Too Much for an Emergency Use Authorization (EUA) Device?
Performance and Analytical Testing to Support Bells and Whistles
Conclusion
Tips
Reference
Chapter 19: Human Factors Considerations in the User Interface Design of Bridge Ventilator Devices
Introduction
The Human Factors Engineering (HFE) Process
HFE Process Details
User Research
Contextual Inquiry
Use Scenarios
Risk Analysis
Usability Objectives or Goals
Iterative Design
Usability Evaluation and Testing
Post-implementation Analysis
Regulator Expectations
References
Chapter 20: Preclinical Animal Testing of Emergency Resuscitator Breathing Devices
Introduction
Objectives of the Study
Materials
Animal Monitoring
Anesthesia and Drugs
Study Protocol
Inducing and Maintaining Anesthesia
Vascular Cutdown and Blood Pressure Catheter Placement
Healthy Lung Data Collection
Tidal Volume Test
Acute Lung Injury by Saline Lavage (Porcine ARDS Lung Model)
Injured Lung Data Collection
ARDS Tidal Volume Test
Respiratory Rate Test
ARDS PEEP Test
Euthanasia
References
Part V: Pandemic Innovations
Chapter 21: Multiplex Ventilation: Requirements and Feasibility of Ventilator Splitters
Introduction
Purpose of Ventilatory Splitters
Mechanisms of Split Ventilation
Simple Shared Ventilation Strategy
Individualized Shared Ventilation Strategies
Pressure-Mode Individualized Ventilation Devices
Volume-Mode Devices
Other Ventilator Splitter Designs
Implementation
Advantages
Limitations
Conclusions
References
Chapter 22: CPAP-to-Ventilator: Open-Source Documentation, UC Irvine
Project Overview
Components List
Modifying a CPAP Device to Gain Access to Blower and Connecting ESC
CPAP-to-Ventilator Wiring Diagram
Arduino Code
Limitations and Areas for Improvement
Disclaimer
Chapter 23: Alternatives to Conventional Noninvasive Positive-Pressure Ventilation Devices
Standard Noninvasive Ventilation
Innovative Noninvasive Ventilation Devices
Snorkel Masks
Advantages
Disadvantages
Helmets
Advantages
Disadvantages
Discussion
Conclusion
References
Chapter 24: Development of an Inexpensive Noninvasive Ventilation Hood
Introduction
Methods
Results
Discussion
Conclusion
References
Chapter 25: Collaborations and Accomplishments Among the Bridge Ventilator Consortium Teams
Index
