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Boards: Monitoring > Spirometry > Flashcards

Spirometry Flashcards

1
Q

Compliance

A

Change in volume per change in pressure

Can be dynamic or static

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2
Q

Static Compliance

A

calculated using end inspiratory occlusion pressure
■ Static compliance = VT/Plateau pressure - PEEP
■ Requires zero gas flow

Reflects elastic resistance of lungs, chest wall

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3
Q

Total Compliance

A

reflects elastic properties of lungs, thorax, abdomen, breathing system

NMBA: will increase chest wall compliance but not affect lung compliance - if paralyzed, changes in compliance DT alterations in lung compliance

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4
Q

Resistance

A

Non elastic resistance to breathing: airway flow resiatcne + pulmonary tissue resistance

For given VT, high resistance overcome by lower flow for longer time or higher driving pressure

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5
Q

Pulmonary Tissue Resistance

A

Pressure required to overcome resistance to gas flow through airways during respiration

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6
Q

factors that Increase resistance

A

Increased FR
Turbulent flow
Bronchoconstriction/increased SmM
Emphysema
Obstruction
Bronchitis/spasm

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7
Q

Factors that Decrease Resistance

A

Laminar flow
Increased lung volume
Bronchodilation
Shorter Airways
Decreased Viscosity

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7
Q

Factors that Decrease Resistance

A

Laminar flow
Increased lung volume
Bronchodilation
Shorter Airways
Decreased Visocisyt

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8
Q

Total Airway Resistance

A

estimated by (Peak Pressure - Plateau Pressure)
■ Normal 2-5 cmH20
■ Increased resistance: higher peak pressure needed to produce same flow

If inspiratory flow and VT remain constant, but resistance increases, greater difference (Ppeak - PPlateau)

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9
Q

Respirometer

A

device that measures volume of gas passing during period of time through a location in flow pathway

detect obstructions, leaks, disconnections, apnea, ventilatory failure and high/low volumes in spont breathing/controlled vent

Required: expired VT, minute volume, both

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10
Q

Ventilator Bellows Scale

A

rough estimate of tidal volume delivered into breathing system

Not an accurate estimate of the volume delivered to patient
● Wasted ventilation DT gas compression, distension of components of breathing system

FGF: additive to VT during inspiration
● Will not be reflected on this scale

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11
Q

Wright Respirometer

A

Gas enters through outer casing, directed through tangential slots to strike a vane, causing rotation

Vane connected to gear system to hands on dial so that a reading corresponding to volume of gas passing through device registered

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12
Q

Evaluation of the Wright Respirometer

A

Over-reads at high flows
○ Pulsatile flow adds to over-reading
○ Higher readings with N20 as carrier gas

Under-reads at low flows

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13
Q

Advantages of the Wright Respirometer

A

● Small size, light weight
● Low dead space - use between patient and breathing system

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14
Q

Disadvantages

A

● No alarms
● Can be difficult to read
● No respiratory rate
● Does not read bidirectional flow

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15
Q

Spiromed

A

Electronic respirometer: use with North American Drager breathing systems

Gas flows through monitor forcing a pair of rotors to counter-rotate - rotate in unison with armature containing magnets

Transistors ay 7, 12 o’clock receive pulses from magnets on rotating armatures –> interface panel –> processer

Number of paired pulses related to vol of gas that passes trough sensor over time with # counted during each breath = Vt

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16
Q

Spiromed Accuracy

A

Programmed to measure TV equal or > 150 mL
○ If < 150 mL, instrument will automatically +2 or more consecutive TV’, reduce the recorded frequency
■ Minute volume remains correct

17
Q

D-Lite Gas Sampler and Flow/Sensor

A

–Two-sided Pitot Tube
–Measuring flow via measurement of pressure difference across flow resistor via Bernoulli Equation

18
Q

MOA Pitot Tube

A

–Placed btw breathing system and patient

–Two sensing tubes: one faces direction of flow (total pressure measurement), other = opposite flow (static pressure)

–Difference between total, static pressure = dynamic pressure –> Bernoulli equation to estimate flow

19
Q

Advantages of Pitot Tube

A

Can determine CO2, O2, anesthetic gases

Derive flows, measured parameters, insp/expiratory VT, minute volumes

Can display FVL, PVLs

Not position dependent, allows bidirectional gas flows, able to be used in both Mapleson and Circle Systems

20
Q

Variable Orifice Flow Sensory

A

Sensors at both connections to CO2 absorber used to measure inspiratory, expiratory flows

Can be used to generate pressure, flow volume loops

Main advantage = used by ventilator to compensate for changes in FGF

21
Q

MOA Variable Flow Orifice

A

Sensors on both sides of circle system

Plastic (miler) flap placed across direction of gas flow - opens at increasing gas flows

Two sensors, transducer inside AxM measure proximal and distal pressure to flap

Volume calculated from these flows

Sensor on inspiratory side connected to pressure sensor so breathing system pressure is measured

22
Q

Fixed Orifice Flow Sensor

A

■ Restrictor and two pressure sensors (on either side of the restrictor)
■ Zeroing valve compensates for pressure sensor drift

23
Q

Respirometer: Ideal position in breathing system

A

Best location = C btw patient, breathing system (at y piece)

24
Q

Advantages: Respirometer at Y Piece

A

● Readings not affected by breathing system leaks, expansion of breathing system components, gas compression
● Can measure both inspired and expired volumes

25
Q

Disadvantages: Respirometer at Y Piece

A

● Will increase dead space
● water condensation may be a problem
● Increased likelihood of damage, disconnection or tracheal tube kinking

26
Q

Where respirometers normally found?

A

exhalation limb upstream or downstream of unidirectional valve

● Can detect reverse flow, malfunctioning uni-directional valve
● Disconnection upstream of exp valve will detect change in volume
● Disconnection that prevents exhaled gases from passing down the exhalation tubing an apnea alarm will occur
● Can read accurately during spontaneous respiration

27
Q

If respirometer downstream of absorber…

A

volume of gas measured will be decreased by the amount of CO2 absorbed

28
Q

If respirometer on inspiratory side…

A

■ Will display high readings as gas that does not inflate the patient’s lungs will also pass through it
■ May not detect disconnection during controlled ventilation

29
Q

Advantages of respirometer placed downstream of inspiratory valve and upstream of expiratory?

A

■ Measurement of both inspiratory and exhalation volumes to produce flow-volume and pressure-volume spirometry loops

30
Q

Placement of Respirometer in Mapleson System

A

Place between the patient connection port and the patient
● Place in expiratory limb in small patients to avoid increased dead space

31
Q

Low Peak Pressure - Causes DT Patient Factors

A

● Leaking trach tube cuff
● Extubation
● Increased compliance
● Reduced resistance

32
Q

Low Peak Pressure - Mechanical factors

A

● Disconnection or major leak in breathing system
● Obstruction upstream of pressure sensor
● Faulty or poorly set/unconnected ventilator
● Failure of gas or power supply to ventilator
● Malfunctioning scavenge
● Increased compliance
● Reduced resistance
● Suction device mistakenly placed within gas flow pathway

33
Q

Sustained Elevated Pressure

A

● Accidental activation of O2 flush
● Occlusion/obstruction of the expiratory limb
● Improperly adjusted APL valve
● Occlusion of scavenging system
● Malfunctioning ventilator
● malfunctioning/incorrectly placed PEEP valve

34
Q

High Pressure

A

● Airway obstruction
● Reduced compliance
● Increased resistance
● O2 flush activation
● occlusion/obstruction of expiratory limb
● Scavenger malfunction
● Patient coughing/straining

35
Q

Factors that can decrease PIP

A

● High compliance, leaks, low insp flow rates, high resp rates, low I:E ratios, Low TV and low FGF

36
Q

Subambient Pressure

A

■ Can be generated by a patient attempting to inhale against a collapse rebreathing bag or increased resistance (blocked inspiratory limb)

37
Q

Paw Measurement Site

A

Best = at y piece

More distant measuring site from patient, less useful as estimate of Paw

38
Q

Typical Locations for Paw Measurement

A

Immediately downstream of inspiratory valve
Upstream to peep valve
Downstream to expiratory valve

Occlusion in circuit = low-pressure distal to obstruction, high pressure proximal to it

39
Q

Expiratory Flow Rate

A

Rate at which gas is exhaled by the patient expressed as volume per unit of time.

40
Q

Expiratory Phase Time

A

Time between start of expiratory flow and the start of inspiratory flow

sum of the expiratory flow and expiratory pause times

Boards: Monitoring (19 decks)

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