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Anaesthesiology
Anesthesia Ventilators
Built from Barash Clinical Anesthesia, 9th Edition
What’s inside
11 sections · 177 slides
Overview
- Scope of this presentation
The Anesthesia Ventilator
- Purpose of the anesthesia ventilator
- Anesthesia ventilator versus ICU ventilator
- Energy sources for gas delivery
- Non-circle breathing systems in context
- Gas exchange in Mapleson A and Mapleson D circuits
- The Bain circuit
- Four technologies for generating positive pressure
- Manufacturers using each ventilator technology
- Why the technology differences matter
Pneumatically Driven Bellows Ventilators
- Double-circuit bellows design
- Gas flow in a circle system with an ascending bellows ventilator
- Inspiratory phase of a bellows ventilator
- Expiratory phase of a bellows ventilator
- The weighted ball and inherent PEEP
- Sequence of a bellows breath
- Electronic cycling and ventilation modes
- Continuous fresh gas flow and delivered tidal volume
- Factors affecting set versus exhaled tidal volume
- Oxygen flush during inspiration
- Bag and APL valve during mechanical ventilation
- Ascending versus descending bellows
- Safety requirement with descending bellows
Electric Piston Pump Ventilators
- Piston ventilator design
- Advantages of piston ventilators
- Principle of fresh gas decoupling
- Fresh gas decoupled breathing system during inspiration
- Inspiratory phase in a fresh gas decoupled system
- Expiratory phase in a fresh gas decoupled system
- Advantages of fresh gas decoupling
- Fresh gas decoupling
- Negative pressure during piston refill
- Consequences of room air entrainment
- Delayed response to fresh gas changes
- Reservoir bag failure in a decoupled system
- Fresh gas decoupling valve incompetence
- Ventilation despite a low-pressure system leak
- Missing or incompetent expiratory unidirectional valve
Electric Turbine Ventilators
- Turbine ventilator design
- Turbine inspiratory phase
- Fresh gas handling in a turbine system
- Manual and spontaneous modes with a turbine
- Airway pressure release ventilation on turbine machines
Volume Reflectors
- Volume reflector breathing system
- Structure of the volume reflector
- Volume reflector coil and breathing circuit
- Inspiration through a volume reflector
- Driving gas in a volume reflector
- Expiration through a volume reflector
Problems and Hazards
- Categories of ventilator hazard
- Breathing circuit disconnections
- Limits of disconnection monitors
- Factors affecting pressure monitor effectiveness
- Threshold pressure alarm limit
- Setting the threshold pressure alarm limit
- Respiratory volume monitors
- Volume sensor technologies
- Hot wire flow sensors
- Capnography for detecting disconnection
- Breathing system misconnections
- Occlusion of the breathing circuit
- Barotrauma from excess inflow
- Adjustable inspiratory pressure limiters
- Leaks in the bellows assembly
- Ventilator relief valve incompetence
- Ventilator relief valve stuck closed
- Scavenging of driving gas on some GE machines
- Control assembly and power supply problems
- Power supply circuit boards and fire risk
- End-tidal target-controlled anaesthesia
- Requirements and availability of automated control
Waste Gas Scavenging Systems
- Purpose of scavenging
- NIOSH exposure recommendations
- Time-weighted average sampling
- NIOSH recommendations for maximum levels of personnel exposure to trace anesthesia gases and vapors
- ASTM and ASA scavenging guidance
- Anesthetic technique causes of room contamination
- Equipment causes of room contamination
- Five components of a scavenging system
- Components of a scavenging system
- Active versus passive disposal
- Gas-collecting assembly
- Overflow of the collecting assembly
- Transfer means
- Occlusion of the transfer means
- Function of the scavenging interface
- Open interfaces
- Open reservoir scavenging interfaces
- Gas path through an open canister
- Efficiency of an open interface
- Closed interfaces
- Closed scavenging interfaces
- Closed interface with positive-pressure relief only
- Closed interface with positive and negative relief
- Relief valve opening pressures
- Determinants of spillage in closed and open systems
- Gas-disposal assembly conduit
- Active and passive disposal assemblies
- Hazards of scavenging systems
- Fire hazard in vacuum pump machine rooms
- Rationale for low-flow scavenging
- Dynamic Gas Scavenging System
- Dynamic Gas Scavenging System
- Additional benefit of concentrated waste gas flow
Failure of Anesthesia Equipment
- Equipment failures in 1,000 anesthesia incidents
- Ventilation of equipment and workstation tidiness
- ASA Closed Claims analysis of gas delivery equipment
- Sites of malfunction in closed claims
- Closed claims update and later machine surveys
- Design limitations of older anesthesia machines
- Safety features of modern workstations
- Backup manual ventilation equipment
- Self-inflating resuscitation bag and its valve mechanism
- How the self-inflating bag works
Checkout of the Anesthesia Workstation
- Frequency of the checkout procedure
- The 2008 ASA approach to preanesthesia checkout
- The two most critical checkout items
- The next three most important preoperative checks
- Importance of the oxygen analyzer
- Calibrating the oxygen analyzer
- Paramagnetic analyzers and the effect of altitude
- What the low-pressure circuit leak test checks
- Common sites of low-pressure circuit leaks
- Why several different leak tests exist
- The Datex-Ohmeda outlet check valve
- Choosing the right leak test
- Positive versus negative pressure leak testing
- Inappropriate oxygen flush testing of a machine with a check valve
- False reassurance from the oxygen flush leak test
- The 1993 FDA universal negative-pressure leak test
- Negative-pressure leak testing device at the common gas outlet
- Interpreting the negative-pressure leak test
- Checking gas supply lines and vaporizers for leaks
- Purpose of the circle system tests
- Automated circle system testing and compliance
- The 1993 FDA circle system leak test
- The circle system flow test
- Visual inspection of unidirectional valves
- Detecting valve incompetence with monitoring
- Workstation self-tests
- Manual checklist screen on an anesthesia workstation
- Automated self-test screen on an anesthesia workstation
- Limits of automated checkout
- Manifold-mounted vaporizers and self-tests
- Adding a functional test of ventilator and circuit
- Assigning responsibility for checkout items
- Preanesthesia checkout items to be completed daily
- Preanesthesia checkout items to be completed daily (continued)
- Preanesthesia checkout items to be completed daily (continued)
- Basic principles of the preanesthesia checkout
- Requirements for safe delivery of anesthesia care
- Timing of the checkout versus urgent patient need
- The anesthesia time out before starting
- Auxiliary oxygen cylinder duration
- Desiccated carbon dioxide absorbent
- Verifying that carbon dioxide absorbent is not exhausted
Summary
- Key points on ventilator technology
- Key points on hazards and monitoring
- Key points on scavenging and checkout
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition