anesthesia machine Flashcards
where does the high pressure system begin and end
begins at cylinder and ends at cylinder regulators
components of high pressure
hanger yoke, yoke block with check valves, cylinger pressure gague, cylinder pressure regulators
gas pressure= cylinder pressure
where does intermediate pressure system begin and end
begins: pipeline
ends: flowmeter valve
components of intemediate
pipeline inlets, pressure gagues, ventilator power inlet, oxygen pressure failure system, oxygen second stage regulator, oxygen flush valve, flowmeter valve
gas pressure if using pipeline vs tank
50 psi if pipeline
45 psi if tank
where does low pressure begin and end
beggins at flow meter tubes and ends at common gas inlet
components of low pressure
flowmeter tubes, vaporizers, check valves, common gas outlet
5 tasks of oxygen in anesthesia machine
o2 pressure failure alarm, o2 pressure failure device, o2 flowmeter, o2 flush valve, ventilator drive gas (if pneumatic bellows)
pin index safety system
PISS- prevents inadvertent misconnections of gas cylinders
on each hanger yoke
what could lead to bypass of PISS
presence of more than one washer between hanger yoke and tank
diameter index safety system
DISS- prevents inadvertent misconnectios of gas hoses- each hose and connector are sized and threaded for each individual gas
max pressure and volume for o2 tank
1900 psi
2, 5 pin
660 L
air tank
625 L
1900 psi
pin 1, 5
n2o tank
1590 L
745 psi
pin 3,5
what does n2o tank weigh empty
14.1 lb (about 20 lb full)
how do you know if a cylinder is mri safe
most of it will be silver- only the top will be colored so you know what gas it is
gas cylinders should neber be exposed to temperatures above
130 F
if a gas cylinder is exposed to a temperature too high what can happen
a fire or explosion
how may the oxygen pressure failure device permit the delvery of a hypoxic mixture
the failsafe device responds to pressure NOT flow- if there is a pipeline crossover- the pressure of the second gas produces pressure to defeat the failsafe device- the patient gets exposed to a hypoxic mixture
what situation devices will hypoxia prevention safety devices not allow delivery of hypoxic mixture
oxygen pipeline crossover, leaks distal to flowmeter valves, administration of 3rd gas, defective mechanic or pneumatic components
whats the difference between oxygen pressure failure device and hypoxic prevention safety device
oxygen pressure failure device: fail safe device- shuts off and reduces n2o flow is o2 pressure drops below 20 psi
hypoxia prevention safety device: proportioning device- prevents you from setting hypoxic mixture with flow control valves- limits n2o flow to 3x o2 flow
where should o2 flowmeter be positioned
always furthest right
made of glass- most delicate part of the machine!!! - a leak can cause hypoxic mixture- oxygen should be closest to manifold so leak in any of the others will not reduce fio2 delivered to the patient
what is the vaporizer splitting ratio
modern variable bypass vaporizers split fresh gas into 2 parts
- some fresh gas enters the vaporizing chamber and becomes 100% saturated with a volatile agent
- the rest of the gas bypasses the vaporizing chamber and does not pick up any volatile agent
before leaving, they mix and this determines the final anesthetic concentration enxiting the vaporizer
what is the pumping effect
it can increase vaporizer output.
basically anything causing gas that has already left the vaporizer to re enter the chamber causes the pumping effect. generally due to pos pressure ventiilation or oxygen flush valve
not a risk in modern machines
what is an injector type vaporizer
desflurane
what temp is des vaporizer heated to
39 C
are vaporizers in circuit or out of circuit
out
what does the oxygen analyzer monitor
oxygen concentration (not pressure)
it is the only device downstream of flowmeters that can detect a hypoxic mixture
what system do leaks most often occur in the machine
low pressure system
what do you do if there is an oxygen supply line crossover
- turn ON oxygen cylinder
- disconnect pipeline oxygen supply - KEY STEP
turning on cylinder will not save pressure b/c it will still pull from pipeline if pressure is fine regardless of the gas inside
2 risks of pressing oxygen flush valve
barotrauma and awareness
the gas from here does not flow through vaporizers so no anesthesia in it
what is volume controlled ventilation
delivers a preset tidal volume over predetermined time- volume is fixed so inspiratory pressure will vary as patients compliance changes. the inspiratory flow is held constant during inspiration
what is pressure control ventilation
delivers preset inspiratory pressure. pressure and time fixed
tidal volume and inspiratory flow varies- depends on pt lung mechanics
if resistance rises or lung compliance decreases- vt suffers and higher inspiratory flow is needed to achieve preset airway pressure
what do you do if you notice soda lime has been exhausted in the middle of the surgical procedure
increase fresh gas flow to convert it into a semi open configuration
increasing minute ventilation will not help
what is dessication
when absorbent is devoid of water
ethyl violet tells you about exhaustion but it does not tell you about the water content
what does a dessicated soda lime cause
carbon monoxide-> carboxyhemoglobinemia
compound a-> renal dysfunction
7 ways to monitor for disconnection of breathing circuit
precordial, visual inspection of chest rise, capnography, resp volume monitors, low expired volume alarm, low peak pressure alarm, failure of bellows to rise with ascending bellows (not with descending)
what is the purpose of unidirectional valves
ensure gas moves in one direction
what happens if a valve becomes incompetent
patient rebreathes exhaled gas- if you cannot fix the valve- increase FGF
what is decreased pulmonary compliance due to
a reduction in static compliance (PIP and PP increase)
-endobronchial intubation, pulmonary edema, pleural effusion, tension pneumo, atelectasis, chest wall trauma, abdominal insufflation, ascites, trend, inadequate muscle relaxation
what conditions increase pulmonary resistance
usually due to reduction in dynamic compliance
kinked ett, endotracheal tube cuff herniation, bronchospasm, bronchial secretions, compression of the airway, foreign body aspiration
what are the 4 phases of a normal capnograph
phase 1: (first flatline) exhalation of anatomic dead space
phase 2: (upstroke) exhalation of anatomic dead space and alveolar gas
phase 3: (top flatline): exhalation of alveolar gas
phase 4: inspiration of fresh gas not containing co2
what happens if the alpha angle increases
alpha angle is the angle on the capnography on the left-
indicates expiratory airflow obstruction
copd, bronchospasm or kinked ett
what does an increased beta angle mean
rebreathing
faulty unidirectional valve
list some reasons that cause increased etco2
increased BMR, malignant hyperthermia, thyroxicosis, fever, sepsis, seizures, laproscopy, tourniquet/ vascular clamp removal, na bicarb administration, anxiety, pain, shivering, increased muscle tone (after nmb reversal), med side effect
list some reasons of decreased etco2
decreased bmr, increased anesthetic depth, hypothermia, decreased pulmonary blood flow, decreased co, hotn, pulmonary embolism, v/q mismatch, med side effect
what are some equipment causes of increased etco2
rebreathing, co2 absorbent exhaustion, unidirectional valve malfunction, leak in breathing circuit, increased apparatus dead space
what are some equipment malfunction causes of decreased etco2
ventilator disconnection, esophogeal disconnect, esophogeal intubation, poor seal with ett or LMA, sample line leak, airway obstruction, apnea
what law is the pulse ox based on
beer lambert law
explain beer lambert law
relates intensity of light transmitted through a solution and the concentration of the solute within the solution
what 2 wavelengths of light does the pulse ox emit
red light (660 nm) - preferentially absorbed by deoxyhemoglobin (higher in venous blood
near infrared light (940 nm) - preferentially absorbed by oxyhemoglobin - higher in arterial blood
what will impair the reliability of the pulse ox
- decreased perfusion- vasoconstriction, hypothermia, raynauds
- dysfunction hgb- carboxyhemoglobin, methemoglobin, nOT hgbS or hgbBF
- altered optical characteristics: methylene blue, indocyanine green, indigo carmine, NOT fluroscein
- non pulsatile flow- CBP, LVAD
- shivering/ movement
- electrocautery, dark skin, venous pulsation, NOT jaundice or polycythemia
what is the ideal bladder length of BP cuff
80% of extremity
what is the ideal bladder width of BP cuff
40%
as pulse moves from aortic root to periphery what changes with SBP and DBP
at aortic root SBP is lowest, DBP is highest, PP is narrowest
dorsalis pedis SBP is highest, DBP lowest and PP is widest
if bp cuff is above heart bp reading will be false
decreased (less hydrostatic pressure)
what does it mean to be optimally damped
baseline is re-established after 1 oscillation
what does it mean to be under damped
the baseline is re-established after several oscillations (SBP is overestimated, DBP is underestimated, and MAP is accurate)
what does it mean to be over damped
the baseline is re established with no oscillations (SBP is underestimated, DBP is overestimated and MAP is accurate)
causes: air bubble, clot in pressure tubing or low flush bag pressure
what does a mean on cvp waveform
rA contraction
what does c mean on cvp waveform
tricuspid valve elevation into RA
what does x mean on cvp waveform
downward movement of contracting RV
what does v mean on cvp waveform
RA passive filling
what does y mean on cvp waveform
RA empties through open tricuspid valve
what increases cvp value
transducer below phlebostatic axis, hypervolemia, RV failure, tricuspid stenosis or regurg, pulmonic stenosis, peep, vsd, constructive pericarditis, cardiac tamponade
factors that decrease CVP
transducer above phlebostatic axis, hypovolemia
what conditions cause loss of a wave on CVP waveform
when synchronized contraction fo RA is lost
-a fib
-v pacing (if underlying rhythm is asystole)
what causes an increased a wave on cvp waveform
tricuspid stenosis, diastolic dysfunction, myocardial ischemia, chronic lung dz rv hypertrophy, av dissociation, junctional rhythm, v pacing asyn, pvs
what causes large v waves
tricuspid regurg, acute increase in intravascular volume, RV papillary muscle ischemia
what does the pressure and waveform of PA look like in RA
1-10 (flat wave)
what does the pressure and waveform of PA look like in RV
15-30/ 0-8
tall!
what does the pressure and waveform of PA look like in PA
you see the dicrotic notch
15-30/ 5-15
what does the pressure and waveform of PA look like in PAOP
lvedp
still see notch but it gets short (can see a, c, v)
5-15
the tip of the PAC should be in what west zone
3
what causes decreased svo2
increased o2 consumption: stress, pain, thyroid storm, shivering, fever
decreased o2 delivery: decreased pao2, decreased hgb, decreased CO
what causes increased svo2
decreased o2 consumption: hypothermia, cyanide toxicity
increased o2 delivery: increased pao2, increased hgb, increased CO
what are the bipolar leads
I, II, III
what are the limb leads
avl, avr, avf
what are the precordial leads
v1-v6
causes of R axis deviation
copd, acute bronchospasm, cor pulmonale, pulmonary htn, pulmonary embolus
causes of L axis deviation
chronic htn, LBBB, aortic stenosis, aortic insufficiency, mitral regurg
class 1 antiarrhythmic
Na channel blockers
depresses phase 0; prolongs phase 3
class 2 antiarrhythmics
beta blockers
slows phase 4- depol in sa node
class III MOA
K channel blockers
prolongs phase 3 repolarization- ex: amiodarone
class IV antiarrhythmic
ca channel blockers- decreases conduction velocity through AV node (verapamil and diltiazem)
what ekg findings are consistent with wolff parkinson white syndrome
delta wave caused by ventricular preexcitation
short PR interval <0.12 seconds
wide QRS complex
possible T wave inversion
what increases risk of torsades de pointes
POINTES
phenothiazines
other meds (methadone, droperidol, amiodarone w/ hypokalemia)
intracranial bleed
no known cause
t1 antiarrhtyhmic
electrolyte (low K, ca, mag)
syndromes (timothy, romano-ward)
treatment for torsades
mag
cardiac pacing to increase HR - reduce AP duration and QT interval
what conditions increase the risk of failure to capture
- high and low K
-hypocapnia
-hypothermia
-MI
-fibrotic tissue buildup around the pacing leads
-antiarrhtyhmic meds
how does the cerebral oximetry work
utilizes NIRS (near infrared sectroscopy)- to measure cerebral oxygenation
how do brain waves change during GA
-indution of GA is associated with increased beta wave acitvity
-light anesthesia is associated with increased beta wave activity
-theta and delta waves predominate during GA
-deep anesthesia produce burst suppression
-at 1.5- 2.0 MAC GA cause complete suppression or isoelectricity
name 2 drugs that are most likely to reduce the reliability of the BIS
-nitrous oxide - increases amplitude of high frequency activity and reduces the amplitude of low frequency ativity. does not affect the BIS value
-ketamine- increases high frequency activity- can produce a higher BIS than the level of sedation/ anesthesia
what is the difference between macro and microshock
macroshock: comparatively lg amount of current that is applied to the external surface of the body. the skins impedance offers a high ersistance so it takes a larger current to induce v fib
microshock: comparatively smaller amount of current that is applied directly to the myocardium- high resistance to skin is bypassed- takes a significantly smaller amount of current to induce v fib
what is the role of the line isolation monitor
line isolation monitor assess the integrity of the underground power system in the OR
tells you how much current could potentially flow through you or the pt if a second fault occurs
what is the main purpose of the LIM (line isolation monitor)
alert the OR staff at first fault
can the LIM protect you or the patient from macro or micro shock
no- not by itself
when will the LIM alarm
when 2-5 mA of leak current is detected
if the alarm sounds what do you do
last piece of equipment that was plugged in should be unplugged
