1. Anesthetic Equipment

2. Gas Supplies Bulk Supply of Anesthetic Gases
In the majority of modern hospitals, piped medical gases and vacuum (PMGV) systems have been installed
only a few cylinders are kept in reserve, attached usually to the anesthetic machine
The PMGV services comprise five sections:
bulk store
distribution pipelines in the hospital
terminal outlets, situated usually on the walls or ceilings of the operating theatre suite and other sites
flexible hoses connecting the terminal outlets to the anesthetic machine
connections between flexible hoses and anesthetic machines
Responsibility for the first three items lies with the engineering and pharmacy departments. Within the operating theatre, it is partly the anesthetist’s responsibility to check the correct functioning of the last two items

3. Bulk Store: Oxygen In small hospitals:
Oxygen cylinder manifolds consist of two groups of large cylinders (size J)

4. Bulk Store: Oxygen In large hospitals: Liquid oxygen store
Liquid oxygen is stored at a temperature of approximately −165 °C at 10.5
If the pressure increases above 17 bar (1700 kPa), a safety valve opens and oxygen runs to waste
Liquid oxygen plants are housed some distance away from hospital buildings because of the risk of fire
Even when a hospital possesses a liquid oxygen plant, it is still necessary to hold reserve banks of oxygen cylinders in case of supply failure

5. Other Gases Nitrous Oxide Medical Compressed Air Piped Medical Vacuum
Nitrous oxide and Entonox may be supplied from banks of cylinders connected to manifolds similar to those used for oxygen
Medical Compressed Air
Compressed air is supplied from a bank of cylinders into the PMGV system
Air of medical quality is required, as industrial compressed air may contain fine particles of oil
Piped Medical Vacuum
Piped medical vacuum is provided by large vacuum pumps

6. Terminal Outlets
Six types of terminal outlet are found commonly in the operating theatre
The terminals are color-coded and also have non-interchangeable connections specific to each gas:
Vacuum (colored yellow) – a vacuum of at least 53 kPa (400 mmHg) should be maintained at the outlet, which should be able to take a free flow of air of at least 40 L min–1
Compressed air (colored white/black) at 4 bar – this is used for anesthetic breathing systems and ventilators
Air (colored white/black) at 7 bar – this is to be used only for powering compressed air tools and is confined usually to the orthopedic operating theatre
Nitrous oxide (colored blue) at 4 bar
Oxygen (colored white) at 4 bar
Scavenging designed to accept a standard 30-mm connection

7. Outlet of central oxygen supply system

8. Gas Cylinders Modern cylinders are constructed from molybdenum steel
They are checked at intervals by the manufacturer to ensure that they can withstand hydraulic pressures considerably in excess of those to which they are subjected in normal use
The cylinders are provided in a variety of sizes (A to J), and color-coded according to the gas supplied
Cylinders attached to the anesthetic machine are usually size E
The cylinders comprise a body and a shoulder

10. Gas Cylinders
Cylinder valves should be opened slowly to prevent sudden surges of pressure
The color codes used for medical gas cylinders in the United Kingdom are shown in Table Different colors are used for some gases in other countries
Cylinder sizes and capacities are shown in Table 15.3.
Oxygen, air and helium are stored as gases in cylinders and the cylinder contents can be estimated from the cylinder pressure
Nitrous oxide and carbon dioxide cylinders contain liquid and vapor
The cylinder pressure cannot be used to estimate its contents because the pressure remains relatively constant until after all the liquid has evaporated and the cylinder is almost empty
The contents of nitrous oxide and carbon dioxide cylinders can be estimated from the weight of the cylinder

11. The anesthetic machine comprises:
A means of supplying gases either from attached cylinders or from piped medical supplies via appropriate unions on the machine
Methods of measuring flow rate of gases
Apparatus for vaporizing volatile anesthetic agents
Breathing systems and a ventilator for delivery of gases and vapors from the machine to the patient
Apparatus for scavenging anesthetic gases in order to minimize environmental pollution.

12. ventilator
Flow meter
bellow
vaporizer
Corrugated tube
APL valve
Scavenging system
Soda lime

13. The Anesthesia Machine
High
Intermediate
Low Pressure Circuit
Mention how the machine is divided into high, intermediate, and low pressure systems

14. Oxygen Supply Failure Alarm
The machine standard specifies that whenever the oxygen supply pressure falls below a manufacturer-specified threshold (usually 30 psig) a medium priority alarm shall blow within 5 seconds

15. Oxygen Flush Valve (O2+)
Receives O2 from pipeline inlet or cylinder reducing device and directs high, unmetered flow directly to the common gas outlet (downstream of the vaporizer)
Machine standard requires that the flow be between 35 and 75 L/min
The ability to provide jet ventilation
Hazards
May cause barotrauma
Dilution of inhaled anesthetic

16. Low Pressure System Consists of: Flow meters Vaporizer mounting device
Check valve
Common gas outlet

17. Flowmeter assembly
When the flow control valve is opened the gas enters at the bottom and flows up the tube elevating the indicator
The indicator floats freely at a point where the downward force on it (gravity) equals the upward force caused by gas molecules hitting the bottom of the float

18. Vaporizers
A vaporizer is an instrument designed to change a liquid anesthetic agent into its vapor and add a controlled amount of this vapor to the fresh gas flow

19. Factors That Influence Vaporizer Output
Flow Rate: The output of the vaporizer is generally less than the dial setting at very low (< 200 ml/min) or very high (> 15 L/min) flows
Temperature: Automatic temperature compensating mechanisms in bypass chambers maintain a constant vaporizer output with varying temperatures
Back Pressure: Intermittent back pressure (eg positive pressure ventilation causes a higher vaporizer output than the dial setting)
C’ = concentration at the new atmospheric pressure
C = the concentration at the old atmospheric pressure (ie the concentration dialed into the vaporizer)
P’ = the barometric pressure for which c’ is being established
P = the barometric pressure for which the vaporizer is calibrated (ie at the old atmospheric pressure)

20. Factors That Influence Vaporizer Output
Atmospheric Pressure: Changes in atmospheric pressure affect variable bypass vaporizer output as measured by volume % concentration, but not (or very little) as measured by partial pressure (lowering atmospheric pressure increases volume % concentration and vice versa)
Carrier Gas: Vaporizers are calibrated for 100% oxygen Carrier gases other than this result in decreased vaporizer output

21. The Circuit: Circle System
Arrangement is variable, but to prevent re-breathing of CO2, the following rules must be followed:
Unidirectional valves between the patient and the reservoir bag
Fresh-gas-flow cannot enter the circuit between the expiratory valve and the patient
Adjustable pressure-limiting valve (APL) cannot be located between the patient and the inspiratory valve

22. The carbon dioxide absorber
Sodalime (CaOH2 + NaOH + KOH + silica) or Baralyme (Ba[OH] 2 + Ca[OH]2) contained in the absorber combines with carbon dioxide, forming CaCO2 and liberating heat and moisture (H2O)
A pH-sensitive dye changes to a blue-violet color, indicating exhaustion of the absorbing capacity
The canister should be changed when 25% to 50% of the contents has changed color, although it should continue to absorb satisfactorily until at least the contents of the top canister have changed color

23. Circle System Advantages: Relative stability of inspired concentration
Conservation of respiratory moisture and heat
Prevention of operating room pollution
PaCO2 depends only on ventilation, not fresh gas flow
Low fresh gas flows can be used
Disadvantages:
Complex design = potential for malfunction
High resistance (multiple one-way valves) = higher work of breathing
The final three points of the advantages section are meant to contrast with the Bain circuit

24. The reservoir bag The reservoir bag is located on the expiratory limb
The reservoir bag accumulates gas between inspirations
It is used to visualize spontaneous ventilation and to assist ventilation manually
Adults require a 3-L bag
Children a 2-L bag
Most new machines have a valve used to switch between the reservoir bag and the ventilator
Older machines may require that the bag be removed and a hose to the ventilator be connected
The final three points of the advantages section are meant to contrast with the Bain circuit

25. The Adjustable Pressure Limiting (APL) Valve
User adjustable valve that releases gases to the scavenging system and is intended to provide control of the pressure in the breathing system
Bag-mask Ventilation: Valve is usually left partially open During inspiration the bag is squeezed pushing gas into the inspiratory limb until the pressure relief is reached, opening the APL valve
Mechanical Ventilation: The APL valve is excluded from the circuit when the selector switch is changed from manual to automatic ventilation

26. Scavenging Systems
A scavenging system channels waste gases away from the operating room to a location outside the hospital building
The ambient concentration of anesthetic gases in the operating room should not exceed 25 ppm for nitrous oxide and 2 ppm for halogenated agents
Specific anesthetic gas-scavenging systems should be used routinely These systems consist of a collecting system, a transfer system, a receiving system, and a disposal system

27. Scavenging Systems
The disposal system may be passive or active, although passive systems are inadequate for modern hospitals
A passive system consists of wide-bore tubing that carries gases directly to the exterior or into the exhaust ventilation ducts
Active systems can be powered by vacuum systems, fans, pumps, or Venturi systems

28. Scavenging Systems
The disposal system may be passive or active, although passive systems are inadequate for modern hospitals
A passive system consists of wide-bore tubing that carries gases directly to the exterior or into the exhaust ventilation ducts
Active systems can be powered by vacuum systems, fans, pumps, or Venturi systems
Mention that the ventilator relief valve is the same thing as the overflow valve mentioned in the previous slides

29. Gas Analysis
Several methods are used to monitor concentrations of oxygen, carbon dioxide, and anesthetic gases in the breathing system
The oxygen analyzer is the single most important monitor for detection of a hypoxic gas mixture
Capnometry, the measurement of carbon dioxide, has many uses, including monitoring the adequacy of ventilation and detection of breathing system faults
Breath-to-breath monitoring of anesthetic concentrations provides tracking of anesthetic uptake and distribution
Most gas analyzers incorporate alarms. Among the techniques for measurement are the following: Mass spectrometry, infrared analysis and oxygen concentrations analysis

30. Anesthesia Ventilators
Most modern anesthesia machines are fitted with a mechanical ventilator that uses a collapsible bellows within a closed chamber
The bellows is compressed intermittently when oxygen or air is directed into the chamber, thereby pressurizing it
The ventilators are time cycled flow (as opposed to pressure) generators, controlled both mechanically and electronically, and pneumatically driven (requiring 10 to 20 L of driving gas per minute)
Ventilator controls vary among makes and models.
Some ventilators require setting of minute ventilation, rate, and inspiratory-expiratory (I:E) ratio to produce the desired tidal volume; other ventilators allow direct adjustment of tidal volume, with I : E ratio being dependent on the inspiratory flow rate, which is set independently

31. Anesthesia Ventilators
Ventilator controls vary among makes and models
Some ventilators require setting of minute ventilation, rate, and inspiratory-expiratory (I:E) ratio to produce the desired tidal volume; other ventilators allow direct adjustment of tidal volume, with I : E ratio being dependent on the inspiratory flow rate, which is set independently
Although gas-driven ventilators can be safely driven with either oxygen or air, most often oxygen is chosen and is supplied by pipeline. Whether or not cylinder gases are used to drive the ventilator in the event of pipeline failure is usually determined by the user. If the machine is set up to drive the ventilator using cylinder oxygen, mechanical ventilation should be discontinued in the event of pipeline failure to conserve oxygen supplies

32. Flow Generator Ventilators
Flow generators deliver a set tidal volume regardless of changes in patients' compliance ( unlike pressure generators ) but will not compensate for system leaks and may produce barotrauma because high pressures can be generated
They reliably deliver the preset tidal volume (even in the presence of a small leak).
The risk o f barotrauma is minimal because most patients presenting to the operating room have healthy normally compliant lungs.

33. Pressure Generator Ventilators
For infants and patients with diseased lungs, the maintenance of preset tidal volumes may produce unacceptably high airway pressures and increased risk of barotrauma
Pressure generators are more appropriate in these situations, because airway pressure is controlled and barotrauma risk minimized

34. Checking Anesthesia Machines
Emergency ventilation equipment
High-Pressure system
Low-Pressure system
Scavenging system
Breathing system
Manual and automatic ventilation system
Monitors

35. Basic Anesthetic Monitoring
ASA Standards for Basic Anesthesia Monitoring
Prepared by
Dr. Mahmoud Abdel-Khalek

36. Basic Anesthetic Monitoring
The primary goal of anesthesia is to keep the patient as safe as possible in the perioperative period
Anesthesia and surgery are serious invasions on the physiologic stability of the human body
Careful monitoring of the patient during and after surgery allows the anesthesiologist to identify problems early, when they can still be corrected
Proper monitoring of the patient can reduce the risks involved in anesthesia and surgery
Some of the physiologic disturbances that occur in the perioperative period include: apnea, respiratory depression, airway obstruction, cardiac depression, hypertension, hypotension, hypervolemia, hypovolemia, arrhythmias, blood loss, fluid shifts, weakness, bradycardia, tachycardia, hyperthermia, and hypothermia

37. Standards of Care Proper monitoring standards are well-defined
The most widely accepted current anesthesia monitoring standards are those that have been published by the by the American Society of Anesthesiologists (ASA)
The ASA standards were initially published in 1986, and were updated afterwards

38. The ASA Standards for Basic Anesthetic Monitoring
Standard I states that a qualified anesthesia provider will be present with the patient throughout the anesthetic
Standard II states that the patient's oxygenation, ventilation, circulation, and temperature will be continually monitored
Assessment of oxygenation involves two parts: measurement of inspired gas with an oxygen analyzer and assessment of hemoglobin saturation with a pulse oximeter and observation of skin color
Assessment of ventilation is by clinical assessment and preferably capnography

39. The ASA Standards for Basic Anesthetic Monitoring
Tracheal intubation must be verified clinically and by detection of exhaled CO2
Mechanical ventilation must be monitored with an audible disconnect monitor
Assessment of circulation involves continuous ECG monitoring, blood pressure measurement at least every five minutes, and continuous monitoring of peripheral circulation by such means as palpation, ausculation, plethysmography, or arterial pressure monitoring
The patient's temperature must be measured if changes are anticipated, intended, or suspected

40. Oxygen analyzers
Oxygen Analyzers Oxygen analyzers are an integral part of the newer anesthesia machines
The purpose of the oxygen analyzer is to confirm that oxygen is being delivered to the patient and that concentration of oxygen in the gas mixture is adequate
The oxygen analyzer provides one last check before the gas mixture is delivered to the patient
For the analyzer to be useful, it must be calibrated and the low-limit alarm must be working
The two main types of oxygen analyzers are galvanic (fuel cell), and the polarographic

41. Pulse Oximeters
Pulse oximetry have been a major advance in improving the safety of anesthesia
The pulse oximeter provides continuous monitoring of hemoglobin saturation using a two-wavelength light absorption technique
The monitor filters out the effects of ambient light, tissue, skin pigment, tissue, and venous blood It focuses on the pulsatile absorption which due to pulsatile arterial blood
Pulse oximeters were developed in the early 1980's and rapidly proved their value in anesthesia
Pulse oximetry allows rapid, beat-by-beat, noninvasive monitoring of blood oxygenation
Disadvantages of pulse oximetry are that it is motion sensitive, and that substances like carbon monoxide, methemoglobin, and some dyes like nail polish affect the readings

42. Capnography
The most common method of exhaled CO2 measurement is sidestream infrared (IR) capnography
Gas from the circuit is drawn into an infrared measurement chamber CO2, N2O, H20, and inhaled anesthetic agents all absorb infrared light, but at slightly different frequencies
Newer monitors have precise light sources and filters that specifically measure the individual gases These monitors provide breath-by-breath gas analysis
Problems with IR capnographs are that moisture can cause blockage of the gas path, and that they can't measure oxygen or nitrogen

43. Abnormalities: Complete absence of waveform Circuit disconnection
Cardiac arrest
Esophageal intubation
Complete respiratory obstruction

44. Automatic blood pressure monitors
Current automatic noninvasive blood pressure monitors work on the oscillometric technique
The cuff inflates well above the systolic pressure and then deflates slowly The monitor first senses oscillations as the cuff drops to systolic pressure
The point at which the oscillations are the strongest is read as the mean pressure
Most of these devices calculate the diastolic pressure after they measure the systolic and mean pressures
The system is normally very reliable and accurate, but motion (especially shivering) on the part of the patient or the surgeon leaning against the cuff will cause false readings or failure to get a reading
Patient injury is possible if the tubing becomes kinked Values may be in error if the cuff is not the proper size

45. ECG Monitor
The ECG monitor can provide a lot of information to the anesthesiologist
Arrhythmia detection and identification of tachycardia and bradycardia are important uses
The ECG monitor may also provide the first indication of myocardial ischemia However the absence of ST depression does not guarantee that ischemia is not present
Lead placement is important in ischemia detection
The most sensitive lead is lead V5, detecting about 75% of ischemic episodes Lead II plus lead V5 raise the detection rate to 80%, whereas leads II, V4, and V5 together detect 98% of ischemic events
Current top-of-the line monitors do automated ST analysis which is more reliable than individual practitioner assessment as long as the measurement points are correct

46. Ventilation Monitors
Current anesthesia machines have ventilator disconnect alarms and built-in spirometers
The spirometers have high and low limit alarm settings
Continuous measurement of exhaled tidal volume can detect circuit leaks and hypoventilation
The spirometers on the anesthesia machines may give false readings if moisture blocks the inner workings
Current anesthesia machines also have overpressure alarms and overpressure "pop-off" valves

47. Temperature Monitors Monitoring of skin temperature is nearly useless
Upper esophageal and nasopharyngeal temperature are affected by airway temperature
Lower esophageal temperature is normally a good reflection of core or blood temperature
Tympanic membrane temperature is also a good indication of core temperature but it is not practical in the operating room environment

48. Peripheral Nerve Stimulators
Peripheral nerve stimulation (PNS) monitoring is not required by the ASA standards However, it is an important safety monitor in patients who a receiving neuromuscular blocking drugs
Train-of-four monitoring assesses the level of nondepolarizer blockade and double-burst stimulation assesses return of strength at the end of the case
Clinical monitoring of neuro- muscular blockade during an anesthetic is difficult without a PNS monitor
Clinical assessment of strength is important, however, at the conclusion of an anesthetic before a final decision is made to extubate the patient

49. Thank You