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Anesthesia Equipment Exam 1 > Anesthesia Gas Monitoring > Flashcards

Anesthesia Gas Monitoring Flashcards

1
Q

Patient Safety: Guiding Concern in Development of Monitors

A
  • Oxygen concentration
  • disconnect alarms
  • end tidal CO2
  • pulse ox
  • peak pressure monitoring
  • anesthesia gas monitoring
  • -N2O
  • -desflurane
  • -sevo
  • -iso
  • -oxygen
  • -CO2
  • -nitrogen
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2
Q

Prevention and Detection

A

-most adverse outcomes come from misuse by practitioner and/or failure to detect equipment failure when it happens

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3
Q

Non diverting gas monitor

A
  • Mainstream, in-line
  • sensor is located directly in the gas stream
  • only CO2 and oxygen are monitored with this mode (cannot monitor volatile gases)
  • oxygen: fuel cell (electrochemical)
  • CO2 infrared
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4
Q

Diverting gas monitor

A

-sidestream
-gas is aspirated from sampling site and through a tube to sensor located inside or on top of machine
-ALL gases can be monitored this way
oxygen: paramagnetic
volatiles, nitrous oxide, and CO2 infared

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5
Q

Infrared Analysis (Diverting or NonDiverting)

A
  • most often used analysis for CO2, nitrous oxide and volatile agents
  • molecules containing dissimiliar atoms will absorb infrared radiation
  • this technology does NOT work for oxygen and nitrogen
  • tend to underestimate inspired levels and overestimate expired levels at high respiratory rates
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6
Q

Infrared Analysis

A

-most molecules will absorb infrared at specific wavelengths and hence the molecule can be identified and its concentration measured

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7
Q

Beer-Lambert Law

A
  • absorption is according to this
  • there is a logarithmic dependence between the transmission of light through a substance and concentration of that substance
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8
Q

IR Side Stream Sampling Diverting

A
  • continuously aspirates a sample of the gas from patient circuit, usually near where breathing circuit is connected to the airway device
  • 50-250 ml/min aspirated (may be returned to patient or to scavenging)
  • sample direct to place between infrared emitter, optical filter, and infrared detector, which outputs a signal proportional to remaining infrared energy not absorbed by the gases
  • to quantify and identify multiple gases simultaneously multiple optical filters are required
  • detected signal then amplified and interpreted via microprocessors
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9
Q

The Good on side stream sampling

A
  • automatical calibration and zeroing
  • quick response time and short warm up
  • minimal added dead-space
  • low potential for cross-contamination between patients
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10
Q

What could be better on side stream sampling

A
  • multiple places that leaks may occur
  • more variability in CO2 readings than with in line sampling- accurate with RR 20-40, decreased with increased rate
  • slower response to changes than with in line sampling
  • water contamination (water traps)
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11
Q

Gas Monitoring

A

-to monitor CO2 the sensor must be positioned between the patient and the circuit, ideally closest to the patient end as possible
why- dead space

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12
Q

Dead space: wasted ventilation

A

-ventilated areas which do not participate in gas exchange

Total deadspace= anatomic + alevolar + mechanical

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13
Q

Anatomic deadspace

A

-airways leading to alveoli

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14
Q

Alveolar deadspace

A

-ventilated areas in lungs without blood flow

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15
Q

Mechanical deadspace

A

-artificial airways including ventilator circuits

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16
Q

Inspired Oxygen Analysis

A
  • FiO2 monitor is extremely important in patient safety
  • first line of defense against detecting hypoxic mixtures
  • but.. ventilation and oxygenation must be considered as two separate entities
  • pulse oximetry is a late indicator of hypoxemia
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17
Q

Low V/Q

A

-shunt perfusion: alveoli perfused but not ventilated

ET tube in mainstream bronchus

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18
Q

V/Q= .8

A

normal

alveoli perfused and ventilated

19
Q

High V/Q

A

deadspace ventilation
-alveoli ventilated but not perfused
(cardiac arrest)

20
Q

Two types of oxygen analyzers

A
  1. Paramagnetic (Diverting)
    - more expensive, no need to calibrate, fast enough to differentiate oxygen concentrations
  2. Electrochemical (Non Diverting)
    - galvanic (fuel cell)
    - calibration needed
21
Q

Paramagnetic Oxygen Analysis

A
  • unpaired electron in the oxygen molecule is attached to magnetic field
  • when oxygen passed through magnetic field it goes to the strongest portion of that field
  • expansion, contraction of the gas creates a pressure wave that is a proportional to the oxygen’s partial pressure
22
Q

Paramagnetic Oxygen Analyzers

A
  • both inspired and end tidal oxygen levels to be measured even at rapid respiratory rates
  • auto calibrates with reference gas (air or known concentration oxygen)
  • many monitors combine diverting IR analysis of CO2, volatiles and nitrous oxide with a paramagnetic oxygen analysis using the same side stream sample
23
Q

Electrochemical Oxygen Analysis (Fuel cell or Galvanic)

A
  • oxygen diffuses through sensor membrane and electrolyte to cathode ray tube
  • reduced there (gains electrons), allowing a current to flow
  • rate at which oxygen enters cell and generates current is proportional to the partial pressure of the gas outside of the membrane
24
Q

Electrochemical Oxygen Analyzer

A

-usually placed on or near the carbon dioxide canister on the inspiratory side
the good: cheaper
the bad: calibration every 8 hours, need frequent changing

25
Q

End-tidal CO2 monitoring

A
  • validation of proper endotracheal tube placement
  • detecting and monitoring of respiratory pathophys
  • hyper/hypoventilation
  • cardiac function, circuit disconnection or leaks
  • adjustment of parameter settings in mechanically ventilated patients
  • Estimate PaCO2
26
Q

ETCO2 and cardiac resuscitation

A

-Non survivors- average ETCO2: 4-10 mmHg
Survivors (to discharge): average ETCO2: >30 mmHg
-if patient is intubated and pulmonary ventilation is consistent with bagging, ETCO2, will directly reflect CO
-flat waveform can establish PEA
-configuration of waveform will change the obstruction

27
Q

Increase in ETCO2

A
  • increased muscular activity (shivering), MH
  • increased CO (during resuscitation)
  • bicarbonate infusion
  • tourniquet release
  • effective drug therapy for bronchospasm
  • decreased minute ventilation
28
Q

Decrease in ETCO2

A
  • decreased muscular activity (muscle relaxants)
  • hypothermia
  • decreased CO (cardiac arrest)
  • pulmonary embolism
  • bronchospasm
  • increased minute ventilation
29
Q

normal arterial CO2:

paCO2 values

A

35-45 mmHg

  1. 7-6.0 kPA
  2. 6-5.9%
30
Q

ETCO2

A

-capnograph
30-43 mmHg
4.0-5.7 kPa
4-5.6%

31
Q

Capnography

A
  • measurement and display of both ETCO2 value and capnogram (CO2 waveform)
  • mesaured by capnograph
  • **picture of waveform
32
Q

Capnometry

A
  • measurement and display of ETCO2 value (no waveform)

- measured by capnometer

33
Q

Value of capnogram

A
  • provides validation of ETCO2 value
  • visual assessment of patient airway integrity
  • verification of proper ETT placement
  • assessment of ventilator/breathing circuit integrity
34
Q

Quantitative vs. Qualitative ETCO2

A

Quantitative: provides actual numeric vale, found in capnographs and capnometer
Qualitative: only provides range of values, termed “CO2 Detector”

35
Q

Draw normal CO2 waveform and label parts

A 
-A-B baseline
B-C expiratory upstroke
C-D expiratory plateau
D- ETCO2 value
D-E inspiration begins
36
Q

CO2 with esophageal intubation

A

-little or no CO2 is present

37
Q

CO2 waveform with inadequate seal around ETT

A

cause: leaky or deflated ET or trach cuff

- artificial airwway too small for patient

38
Q

Hypoventilation causes what in ETCO2?

A 
Increase in ETCO2
-possible cause:
decreased RR
decreased TV
increased in metabolic rate
rapid rise in body temp
39
Q

Rebreathing– possible cause

A

faulty expiration valvue
inadequate inspiratory flow
insufficient expiratory flow
malfunction of CO2 absorber system

40
Q

Obstruction-possible causes

A

kinked or occluded artificial airway
presence of foreign body in the airway
obstruction in expiratory limb of breathing circuit
bronchospasm

41
Q

Spontaneous breathing Effort with Controlled Ventilation

A

-curare cleft:
appears when muscle relax being to subside
-depth of clef is inversely proportional to degree of drug activity

42
Q

Sudden loss of waveform

A 
#1 thought= airway disconnection
-apnea, airway obstruction, dislodged airway, ventilator malfunction, cardiac arrest
43
Q

Colormetric CO2 detector

A
  • NOT A MONITOR
  • uses chemically treated paper that exchanges color hen exposed to CO2
  • must match color to a range of values
  • requires 6 breaths before determination
  • gold is golden*

Anesthesia Equipment Exam 1 (9 decks)

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