Technology Topics 2005 CA1 - CA40 focus BWH Anesthesia Clinical Conference August 31, 2005 James H. Philip, MEE, MD, CCE © Copyright 2005, James H Philip, all rights reserved

Our New Anes Machines

Three Ventilator types at BWH Old fashioned Bellows movement control Fresh Gas Flow decoupling Exhaled tidal volume feedback More

Old fashioned Bellows movement control Gas Compression and and tubing expansion decrease actual tidal volume Fresh gas flow (during each inspiration) adds to actual tidal volume Older Machines Ohmeda Modulus 2+ and CD Draeger MRT

Fresh Gas Flow decoupling Piston pushes defined volume into lungs Fresh gas is stored in reservoir bag during inspiration Piston takes first from reservoir bag, Piston then takes from Exhaled gas Reservoir bag moves with Mech Vent (V or P mode) Draeger Fabius, Tiro

Draeger COSY-2

Exhaled tidal volume feedback Bellows moves approximately set tidal volume Exhaled volume is measured Next and subsequent inspired bellows movement changes Bellows volume changes based on previous exhaled tidal volumes SmartVent in Ohmeda Modulus SE and Ohmeda Aestiva

Compensation for Compliance More

SmartVent will compensate for changing circuit and lung compliance SmartVent has exhaled tidal volume feedback If circuit or patient compliance changes, exhaled volume changes next inspired tidal volume is adjusted to compensate for this Ohmeda Aestiva SmartVent ® Mostly in OB

Fabius compensates for Circuit Compliance But, only for the compliance measured during pre-use system check Adding tubing will add compliance – Fabius will not adapt Record circuit compliance if adding length during case is possible Compliance is likely linear with length Compliance will have little or no impact during spontaneous breathing

Fabius will not compensate for Lung Compliance or changes in lung compliance

SmartVent will compensate for changing circuit and lung compliance SmartVent has exhaled tidal volume feedback If circuit or patient compliance changes, exhaled volume changes next inspired tidal volume is adjusted to compensate for this

SmartVent flow sensor must be kept dry If wet, it cannot compensate for flow because it cannot measure flow

Compliance will not impact spontaneous breathing much. Airway pressure will not differ much from zero Thus, with no change in pressure, thee will be no change in volume

Three Gas Sensor Technologies at BWH Turbine Flow Sensor Hot wire Anemometer Flow Sensor Differential pressure across an orifice Flow Sensor

Four Gas Sensor Technologies at BWH Turbine Flow Sensor Hot wire Anemometer Flow Sensor Differential pressure across an orifice Flow Sensor Ultrasonic Flow Sensor - MR-compatible More

Turbine Flow Sensor Turbine (fan) spins, light is interrupted by the blades Second light sensor-receiver pair to sense direction

Hot wire Anemometer Flow Sensor Wire is heated. Flow of gases cools it Desflurane has high specific heat and cools sensor Des comp means Desflurane compensation on Draeger Fabius. Under top surface of Absorber+ assembly Subject to physical damage leading to leak

Differential pressure across an orifice Flow Sensor Variable orifice allows accuracy over flow range from infant to giant One water droplet disables pressure reading and flow calculation Keep this sensor dry Pressure sample ports point up, SmartVent in Ohmeda Modulus SE and Aestiva

Ultrasound Flow Sensor MR - compatible More info some other time

Sample Gas Return (SGR) and Leaks

Older Ohmeda Anes Machines (Ohmeda Modulus 2 and SE) have SGR connected to CO2 Absorber port specific port is on Absorber but functionally in Expired Ckt Limb connection is marked Expiratory Airway Pressure Ohmeda Aestiva and Draeger Fabius have added adapters for SGR SGR connector is chrome and connected to CO2 Absorber Exp limb SGR can sometimes be connected to Scavenger Interface More

During Leak Test, be careful with Sample Gas and Sample Gas Return Two good options, and one bad Good - Disconnect Sample Gas and Sample Gas Return Good – Connect Sample Gas and Sample Gas Return to breathing circuit No net loss or gain from sampled gas or its return Bad – Connect one but not both of Sample and Return Connect Sample = 200 mL/min leak Connect Return = 200 mL/min anti-leak or volume gain Good – Connect both. No gain, no loss This also checks gas monitor for leaks Sample Gas Return from Gas Monitor (SGR) can confuse leak tests

CHARCOAL ANESTHETIC AGENT ABSORBERS Charcoal Absorbers can remove volatile agents from effluent gas Outlying Anesthetizing Locations need innovative scavenging Charcoal Absorbers absorb 50 g anesthetic Charcoal Absorbers absorb almost same amount that vaporizer delivered More

Charcoal Absorbers can remove volatile agents from effluent gas Charcoal is “activated” in factory by heating to eliminate hydrocarbons Charcoal absorber can be placed where Scavenger is attached Charcoal absorbs Iso, Sevo, Des, and other vapors Charcoal does not absorb Nitrous Oxide

Outlying Anesthetizing Locations need innovative scavenging No wall Waste Anesthetic Gas Disposal (WAGD) System Charcoal absorber on scavenger connection accomplishes this These Anes Machines are not fitted with Nitrous Oxide Rooms without WAGD System also lack wall Nitrous Oxide Future - all potentially anesthetizing locations should have WAGD System

Charcoal Absorbers absorb 50 g anesthetic Volume = 50 g / 1.5 g/mL = 33 mL Anes Tech will weigh Charcoal Absorber after each anesthetic Anes Tech will discard Charcoal Absorber that has gained 50 g

Charcoal Absorbers absorb almost same amount that vaporizer delivered All agent from vaporizer goes to Patient or out Scavenger to Absorber At end of case, agent in patient goes out Scavenger to Absorber Therefore, Charcoal Absorber collects all that leaves the vaporizer Directly via excess FGF or indirectly via Patient Amount absorbed is a bit less by amount patient retains on discharge from OR

ALTITUDE EFFECTS ON VAPORIZERS Concentration Delivery Vaporizers and Flowmeters Partial Pressure Delivery Vaporizers Approximate Partial Pressure Delivery Vaporizers More

Concentration Delivery from Vaporizers and Flowmeters Nitrous oxide and Desflurane via Tec 6 Vaporizer provide fractional composition Fractional composition is called concentration or fraction At altitude, since fraction applies to diminished atmospheric pressure These vaporizers under-anesthetize at altitude 50% of a lower atmospheric pressure of N2O less potent than 50% of higher atmospheric pressure

Partial Pressure Delivery Vaporizers Modern Vaporizers for the volatile liquids Iso, Sevo, Halo are all similar Dial is set and produces a splitting ratio. Flowmeter gas splits between vaporization chamber and bypass The actually spllitng is applied at the outflow of the vaporization chamber Thus, saturated vapor pressure (mmHg) is fractionally divided by the split Output is constant partial pressure at any altitude These vaporizers correctly anesthetize at altitude

Approximate Partial Pressure Delivery Vaporizers Older vaporizers for Halothane, Enflurane, and Isoflurane were different Split was at entrance to Vaporization Chamber rather than exit Outflow fraction from vaporization chamber increased slightly with altitude These vaporizers slightly over anesthetized at altitude Some textbooks and papers still cite this incorrect obsolete design

FABIUS REQUIRES PRESS ROTARY KNOB TO CONFIRM - be careful! Draeger Fabius requires you press Rotary Knob to confirm vent settings Ohmeda Smart-Vent allows you to confirm Rotary Knob or original Select button Beware, Beware, Beware This is a challenge to all of us

OXYGEN RATIO CONTROL DIFFERES AMONG MACHINES Ohmeda Anes Machines (Ohmeda Modulus 2 and SE) Hidden Chain links O2 and N2O needle valves Draeger Anes Machines (Fabius, Tiro, Narkomed, Future) Flow changes by itself when other flow is adjusted More

Ohmeda Anes Machines (Ohmeda Modulus 2 and SE) Hidden Chain links O2 and N2O needle valves Rotate either N2O or O2 to produce Fresh Gas < 25% oxygen and other knob turns Nitrous up or oxygen down does this No hidden or undisclosed functiuonality Icon/Picture of a chain linking the knobs is on the machine

O psi O 2 SERVICE INLET 55psi 35 psi Mechanical Stop 0, 50 or 250 ml/min NEEDLE VALVE FAILSAFE VALVE CALIBRATED VAPORIZERS Fresh Gas Flow (FGF) OXYGEN FLUSH VALVE [first] ON/OFF SWITCH CHECK VALVE PRESSURE REGULATOR N 2 O SERVICE INLET 55 psi SIMPLIFIED ANESTHESIA MACHINE SCHEMATIC DIAGRAM GEDO (GE-Datex-Ohmeda) Chain Link 25 for Delivered O 2 Modulus 2+, Aestiva O2O2 N2ON2O FRESH GAS HOSE Oxygen Flush Flow (last) [Anesthetizing gases flow] COMMON OUTLET FILTER WALL DISS diameter index safety system CONNEC- TION O2O2 N2ON2O D S I O2O2 N2ON2O PSI Is OK ≤ 3:1

O psi O 2 SERVICE INLET 55psi 35 psi Bypass Flow 0, 50 or 250 ml/min NEEDLE VALVE Linear Regulator CALIBRATED VAPORIZERS Fresh Gas Flow (FGF) OXYGEN FLUSH VALVE [first] ON/OFF SWITCH CHECK VALVE PRESSURE REGULATOR N 2 O SERVICE INLET 55 psi SIMPLIFIED ANESTHESIA MACHINE SCHEMATIC DIAGRAM Draeger ORMC = Oxygen Ratio Monitor/Controller Fabius, Tiro, Narkomed MR O2O2 N2ON2O FRESH GAS HOSE Oxygen Flush Flow (last) [Anesthetizing gases flow] COMMON OUTLET FILTER WALL DISS diameter index safety system CONNEC- TION O2O2 N2ON2O D S I O2O2 N2ON2O PSI Is OK

Draeger Anes Machines (Fabius, Tiro, Narkomed, future) User moves one flow control knob Flow don’t change User moves other knob Other Flow changes ‘by itself” Flows interact and often confuse

Negative Pressure Leak Test (NPLT) More

Negative Pressure Leak Test (NPLT) Detects a leak in Anes Machine Low Pressure System Low Pressure System is from Pressure Regulator to Common Outlet (CO) Low Pressure System is needle valve, rotameter, vaporizer, and some pipes.

Negative Pressure Leak Test (NPLT) Concept – “low pressure” because the pressure drops at the needle valve NPLT Required on Anes Machines which have a 1-way valve between Vaporizer and CO

Concept – one way valve hides leaks from positive pressure leak test of circuit N PLT on Older Ohmeda Machines (Modulus 2 through Modulus SE with SmartVent NPLT (Negative Pressure Leak Test) is performed as follows Switch off Anes Machine to achieve 0 FGF. Flow = 50 mL/min is almost perfect. Take negative pressure bulb from bottom drawer Connect negative pressure bulb to CO (Common Outlet) Switch on vaporizers one at a time With a vaporizer on, squeeze bulb three times to apply negative pressure to CO If bulb fills, there is a leak in needle valve, flow meter, vaporizer. Test each vaporizer this way Common leak sources are Vaporizer Filler Port open and broken flow tube

Draeger Fabius Alarms can be confusing More

Draeger Fabius Alarms can be confusing Some of them work as follows Ventilation alarms depend on pressure that the ventilator achieves and pressure thresholds that have been set Vent Monitor wants threshold to be 4 cmH 2 O below present peak ventilation pressure If Vent pressure is too high or too low compared with this, alarm sounds

Pressure Threshold Low - Advisory Pressure Threshold Low Advisory means you should raise the threshold This will make the monitor more sensitive to leak or decreased pressure

Apnea Pressure - Warning Apnea Pressure Warning means pressure did not cross the threshold You may be ventilating adequately but monitor only knows Pressure &Threshold Threshold was set by User or Ventilator when ventilation began

How to correct this Warning or Advisory 1) Check patient IS BEING VENTILATED AS YOU PLANNED 2) Reset thresholds to current situation of ventilator settings and patient physiology Here’s how 3) Press SETUP button Press AUTO SET Thresholds are now reset 4) Check Clinical situation

Pre-Use Check Documents are available Every machine has its machine-specific pre-use check list attached Pre-Use Check is usually on chain at right back corner of Anes Machine Pre-Use Checks vary slightly from model to model Draeger Fabius is very different and included automatic ventilator calibration Documents (Microsoft Word) are available several places

Just say “no” to 100% O2 Cal 21% is necessary and sufficient More

Just say “no” to 100% O2 Cal Datex-Ohmeda SmartVent has an oxygen sensor built in Removable Sensor is in inspiratory part of Absorber Assembly 21% Oxygen Cal is mandatory and important 100% Cal often cannot be satisfactorily performed 100% Oxygen calibration does not need the accuracy of 21% Just say No to optional 100% Cal

Fabius has a Water Trap Between Ventilator and Breathing Circuit Water condenses here Keep it empty More

Empty water trap in Fabius Ventilator hose Before using Fabius Observe and empty if full during case Failure to do this will result in Alarms and Ventilator Failure Beware of full Water Trap

First alarm is an incorrect one - Low Fresh Gas Flow Fabius has misinterpreted what is wrong Piston trying to refill encounters a negative pressure equal to depth of water pool Negative piston pressure usually means reservoir bag is empty and FGF is low Low Fresh Gas Flow alarms sounds

Second problem is real Vent Failure Alarm and Vent Failure This is from water too deep in the vent hose. Keeping water trap from overfilling will prevent this problem Empty water trap in Fabius Ventilator hose before using Fabius and observe and empty if full during case

Anesthesia Department Web Site And navigate to Education / Educational Resources / Technology Matters Or go directly to Special thanks to Anes IS Team Jamie Bell, Dan Holtzman, Fred Donovan, Athena Dimas, and new Director, Bob Gimlich All this pre-use check and use info is on

Thank you