Exam 1- Clinical Monitoring (6/12/23) Flashcards
What are the two sampling sites depicted by the two arrows?
- Elbow
- Y-piece
What are the two types of gas sampling systems?
- Side-stream/ diverting analyzer
- Mainstream/ non-diverting analyzer
Which gas sampling system will have more lag time (transit time)?
- Side-stream/ diverting analyzer
What is rise time in terms of the gas sampling system?
- The time taken by the analyzer to react to the change in gas concentration
The mainstream analyzer will have a faster rise time.
Side-stream response is dependent on what factors? What is the sampling rate?
- Sampling tubing inner diameter
- Length of tubing
- Gas sampling rate (50 - 250 mL/min)
What are gas sampling challenges with mainstream analyzers?
- Water vapor (can block IR waveforms)
- Secretions
- Blood
- More interfaces for disconnections
What are gas sampling challenges with side-stream analyzers?
- Kinking of sampling tubing (can break over time)
- Leaks in the line
- Failure of sampling pump
- Slow response time
- Water vapor (can block IR waveforms)
The total pressure exerted by a mixture of gases is equal to the sum of the partial pressures exerted by each gas in the mixture. What law is this?
- Dalton’s Law
At sea level, what is the total pressure of all anesthetic gases in the system?
- 760 mmHg
Calculate the partial pressure of O2 at room air
- 159.6 mmHg
760 mmHg x 21% = 159.6 mmHg
Calculate the partial pressure of inspired O2 at room air.
- 149.7 mmHg
PIO2 = FIO2 (PB -PH2O)
21% (760 - 47) = 149.7 mmHg
_________ is an instrument that allows the identification and quantification of up to eight of the gases commonly encountered during administering an inhalational anesthetic.
- Mass Spectrometry
This tool uses a high-powered argon laser to produce photons that collide with gas molecules in a gas sample. The scattered photons are measured in a spectrum that identifies each gas and concentration.
- Raman Spectrometry (Raman Scattering)
No longer in use
What is typically used in anesthesia machines to determine the concentration of gas?
- IR Analysis
What is the most common gas analyzer?
- Non-dispersive IR analyzer
IR analysis measures energy absorbed from a narrow band of wavelengths of IR radiation as it passes through a gas sample
What gases are measured using a non-dispersive IR analyzer?
- CO2
- Nitrous Oxide
- Water
- Volatile Anesthetic Gases
O2 does not absorb IR radiation
How does Infrared Analysis (IR Analyzer) work?
- Gas will enter the sample chamber
- Each gas has a unique IR transmission spectrum absorption band
- Strong absorption of IR light occurs at specific wavelengths
- IR light is transmitted through the gas sample and filtered
- The amount of IR light that reaches the detector is inversely related to the concentration of the gas being measured
- Less light = high concentration of gas
Do side-stream analyzers take into account of water vapors?
- No
- Side-stream analyzers report ambient temperature and pressure dry values (ATPD).
What are the two types of oxygen analyzers?
- Fuel or Galvanic Cell O2 Analyzer
- Paramagnetic O2 Analyzer
What are the drawbacks of a Fuel/ Galvanic Cell O2 Analyzer?
- Short life span (months) depending on the length of O2 exposure
- Slow response time (best to measure O2 in the inspiratory limb)
What oxygen analyzer is used in most side-stream sampling multi-gas analyzers?
What is the benefit of this analyzer?
- Paramagnetic O2 Analyzer
- Benefit: Rapid response, breath-by-breath monitoring
Purpose of gas sampling inside the inspiratory limb.
- Ensures oxygen delivery
- Analyzes hypoxic mixtures
Purpose of gas sampling inside the expiratory limb.
- Ensure complete pre-oxygenation/ “denitrogenation”
- ET O2 above 90% adequate
What can trigger a low O2 alarm?
- Pipeline crossover
- Incorrectly filled tanks
- Failure of a proportioning system
What patient population must we be wary of for high O2 alarms?
- Premature infants (high O2 can cause blindness)
- Patients on chemotherapeutic drugs (ex: bleomycin)
Bleomycin has been associated with pulmonary toxicity, which can cause lung damage. Supplemental oxygen may exacerbate this toxicity.
What can airway pressure monitoring detect?
- Circuit disconnections
- ETT occlusions
- Kinking in the inspiratory limb
- Fresh gas hose kink or disconnection
- Circuit leaks
- Sustained high-circuit pressure
- High and low scavenging system pressures
What are the two types of pressure gauges used in airway pressure monitoring?
- Mechanical Pressure Gauges
- Electronic Pressure Gauges
What are the characteristics of mechanical pressure gauges?
- Requires no power, always on, and have high reliability
- No recording of data
- No alarm system
- Must be continually scanned
What are the characteristics of electrical pressure gauges?
- Built within ventilator or anesthesia machine
- Alarm system integrated
- Sensitive to small changes
What is the purpose of the breathing circuit low-pressure alarms?
- Identification of circuit disconnection or leaks
- Monitors airway or circuit pressure and compares it with a preset low-pressure alarm limit.
Where do most of the circuit disconnections occur at?
- 70% of disconnections occur at the y-piece.
What is the normal peak airway pressure?
- 18-20 cmH20
Low-pressure limit should be set just below this.
What does the sub-atmospheric pressure alarm measure?
- Measure and alerts negative circuit pressure and potential for the reverse flow of gas
What can negative pressure cause the patient to have?
- Pulmonary Edema
- Atelectasis
- Hypoxia
What can cause negative pressure on the anesthesia machine?
- Active (suction) scavenging system malfunctions
- Pt inspiratory effort against a blocked circuit
- Inadequate fresh gas flow
- Suction to misplaced NGT/OGT
- Moisture in CO2 absorbent
What are the causes of high-pressure alarms?
- Obstruction
- Reduced compliance
- Cough/straining
- Kinked ETT
- Endobronchial intubation
At what pressure are continuing pressure alarms triggered? What causes it?
- Continuing pressure alarms are triggered when circuit pressure exceeds 10 cm H2O for more than 15 seconds
- Fresh gas can enter the circuit but can’t leave
What are causes of continuing pressure alarms?
- Malfunctioning adjustable pressure relief valve
- Scavenging system occlusion
- Activation of oxygen flush system
- Malfunctioning PEEP
What is the gold standard for the site of nerve stimulation?
- Ulnar Nerve
The ulnar nerve innervates the adductor pollicis muscle and has the lowest risk of direct muscle stimulation.