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Lab Techniques (321) > Resiratory > Flashcards

Resiratory Flashcards

1
Q

What is the difference between ventilation and respiration?

A

Ventilation = moving air from external environment to the alveoli
Respiration = physiological process involving the exchange of gases (usually O2 & CO2) i.e.. internal respiration at the cellular level.

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2
Q

What is the equation for TOTAL VENTILATION (Ve)

A

TOTAL VENTILATION (Ve) = Va + Vdeadspace

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3
Q

What is Total Lung Capacity (TLC)

A

The total volume that the lungs can hold

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4
Q

What is Vital Capacity (VC)

A

The volume of air that can be fully exhaled after a full inhalation

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5
Q

What is tidal volume (Tv)

A

The volume of air exchanged during normal breathing

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6
Q

What is Functional Residual Volume (FRV)

A

The volume of air in the lungs after a normal exhalation

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7
Q

What is residual volume?

A

The volume of air remaining in the lungs after a max exhalation

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8
Q

Define spirometry

A

Spirometry determines a change in lung volume by measuring the volume of inspired and expired air

-subject must breath against a known resistance to then give a measurable output

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9
Q

Total Ve (minute ventilation) is determined by measuring _________ through a __________

A

Airflow, Transducer

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10
Q

How are volume and frequency determined from spirometry

A

Determined from the airflow recording

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11
Q

Total minute ventilation (Ve) is the product of __________ and ____________

A

Tidal volume (VT) and Breathing Frequency (Bf)

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12
Q

What is a normal resting Tidal volume (Vt)?

A

~ 500 mL or 0.5L

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13
Q

What is a normal resting Bf?

A

~12-18 breaths per min

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14
Q

What is the equation for MINUTE VENTILATION? (Ve)

A

Ve = Bf x Vt
Minute ventilation = breathing frequency x tidal volume

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15
Q

What are the 4 most frequently used transducers?

A
  • strain gauge plethysmography (indirect)
    -Pneumotachometer
    -turbine
    -hot wire anemometer
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16
Q

How does the strain gauge plethysmography work?

A

Stretch around chest wall —> transducer —> electrical signal

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17
Q

What are some disadvantages of the strain gauge plethysmography

A
  1. Chest wall can move against a closed glottis and make it seem like there is a change in airflow
  2. Does not directly measure airflow
  3. Super old school
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18
Q

What are some ADVANTAGES of the strain gauge plethysmography

A
  1. Very easy to set up and portable
  2. Works well when paired with a device that detects airflow
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19
Q

What is the Pneumotachometer?

A
  • airflow is determined by measuring the differential pressure (🔺P) across a known airflow resistance
  • 2 types :
    1. Lilly: measures pressure drop over a mesh screen
    2. Fleisch: measures pressure drop over a series of parallel capillary tubes
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20
Q

ADVANTAGES of the pneumotachometer

A
  1. Simple and easily positioned in a breathing circuit
  2. Can detect uni- and bi-directional airflow
  3. Good temporal resolution; capable of detecting rapid changes in direction and velocity
    - good for measuring O2 and CO2 changes over a short period of time
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21
Q

Disadvantages of the pneumotachometer

A
  1. Assumes (🔺P) remains linear with changes in flow
  2. Requires laminar flow (which likely isn’t always the case)
  3. Sensitive to resistance changes (e.g. secretion or condensation accumulation)
  4. Sensitive to gas density (e.g. gases of different composition)
    -pneumotachometer must be calibrated with the corresponding gas
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22
Q

Why are pneumotachometers more reliable with a thermostat?

A

-heating up the pneumotachometer can help prevent condensation buildup

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23
Q

What is the Turbine flow- meter?

A

It is a turbine that measures flow with vanes that spin in relation to the gas velocity

-the speed of the turbine spinning is detected by a beam of light that is broken when a vane passes through it

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24
Q

ADVANTAGES of the turbine flow-meter

A
  1. Insensitive to changes in water vapour, temp, flow profile
  2. Great for VO2max test
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25
Q

DISADVANTAGES of the turbine flow-meter

A
  1. Lag between cessation of actual flow and the stopping of the turbine spinning (inertia)
  2. Lag worse at high flow rates
  3. Temporal errors can impact measurement of breath-by-breath gas exchange (i.e. affects VO2 and VCO2)
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26
Q

What is the Hot-wire anemometer?

A

Flow is measured by determining the amount of cooling of a wire
-a metal wire is heated to a known temperature and kept constant (250ºC)
-as airflow passes, the wire is cooled and the thermostat has to work harder to keep the wire constant

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27
Q

ADVANTAGES of the Hot-wire anemometer

A
  1. Direct measure of mass flow
  2. Flow can be laminar or turbulent
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28
Q

DISADVANTAGES of the Hot-wire anemometer

A
  1. Additional analysis required to determine flow direction
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29
Q

4 examples of pulmonary function tests

A

-spirometry
-lung volumes (e.g. whole-body plethysmography)
-diffusing capacity
-exercise tests

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30
Q

What volumes can spirometry NOT determine

A
  • residual volume
  • total lung capacity
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31
Q

Which pulmonary function test CAN determine Residual volume and Total lung capacity?

A

Whole-body plethysmography

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32
Q

What is a whole-body plethysmography?

A

-known volume in box (sealed with rigid walls)
-generation of airflow requires pressure (change in pressure)
-generation of pressure results in compression or decompression of air (relative to its starting point)

33
Q

What is the clinical relevance of Pulmonary Function Tests? (PFTs)

A
  • Detect disease (potential screening tool for research)
  • Evaluate extent and monitor course of disease
  • Evaluate treatment
  • Assess risk for surgical procedures
34
Q

Diffusion VS perfusion

A

Diffusion = the movement of O2 and CO2 across the barrier occurs by passive (i.e., simple) diffusion
Perfusion = pulmonary capillaries perfume the lung with deoxygenated blood

35
Q

Define external respiration

A
  • the movement of gas across the barrier over time is proportional to the diffusing capacity (DL) and the concentration (i.e., pressure) gradient
36
Q

What is the equation for V NET

A

Vnet= DL (P1 - P2)

37
Q

How do we measure diffusion (DLCO) ?

A

DLCO: diffusing capacity of the lungs for carbon monoxide (CO)

We use CO because it has a higher affinity for hemoglobin than O2 does

  • participant inhales a small known amount of CO, 10 seconds of apnea (not breathing) and then measure how much CO is left
38
Q

What are some variables that can affect intensity and timing of breathing?

A

[CO2], [O2], [K+], [Na+] , Temperature, Atmospheric pressure, PO2, exercise, drugs & hormones , sleep state, emotional state, central / peripheral chemoreceptors

39
Q

What are the 3 respiratory centres?

A

Dorsal Respiratory Group (DRG)
- receives input from peripheral lung stretch receptors and chemoreceptors and passes it on to the ventral respiratory group for integration

Ventral Respiratory Group (VRG)
-rhythm-generating and integrative centre
-Excites the inspiratory muscles via the phrenic and intercostal nerves
-sets eupnoea (normal breathing ; 12-18 breaths per minute)

Pontine Respiratory centres
-influence & modify activity of the medullary centres
-influences transition between inspiration and expiration

40
Q

What does the prefix “NORMO” mean

A

Normal

41
Q

What does the prefix “An (Ana- or ano-)” mean

A

Without or lacking

42
Q

What does the prefix “HYPO” mean

A

Below normal

43
Q

What does the prefix “HYPER” mean?

A

Extreme or above normal

44
Q

What does the prefix “POIKILO” mean

A

Variable

45
Q

What does the suffix “OXIA (IC)” mean

A

Pertaining to oxygen ; O2

46
Q

What does the suffix “ CAPNIA (IC)” mean

A

Pertaining to carbon dioxide ; CO2

47
Q

What does the suffix “BARIA (IC)” pertaining to barometric pressure

A

Pertaining to barometric pressure

48
Q

Define HYPOventilation

A

-deceased ventilation that fails to meet metabolic needs

49
Q

What does HYPOventilation result in

A

-CO2 retention in blood and tissue
-leads to a respiratory acidosis (built up CO2/H+)
-vasodilation in cerebral vessels to increase washout

50
Q

Define HYPERventilation

A

-increased depth and rate of breathing that exceeds the body’s need to remove CO2

51
Q

What does HYPERventilation result in

A

-rapid flushing of CO2 from the blood and tissue
-respiratory alkalosis
-Cerebral vasoconstriction (dizziness & fainting)

52
Q

What do the Central Chemoreceptors detect

A

CO2 / H+ (pH)

53
Q

What do Peripheral Chemoreceptors detect?

A

CO2 / H+ / O2

54
Q

What are peripheral chemoreceptors good for

A

-sensitive to both changes in PaO2 and PaCO2… and much more
-Elicit a quick response
-Ventilatory onset is typically ~ 10-15 seconds from stimulus
-can isolate peripheral chemos temporally, locally, or specifically

55
Q

What are some ADVANTAGES of Peripheral Chemoreceptor sensitivity tests

A
  1. Cheap and simple
  2. Portable
  3. Short in duration (multiple tests within participants is easy)
56
Q

What are some DISADVANTAGES of peripheral chemoreceptor sensitivity tests

A
  1. Ventilation responses are highly variable and between participants
  2. Elicits a small respiratory and cardiovascular response
  3. Difficulty to blind participant (will breath different if they are not blinded & you can taste CO2
  4. Highly indirect
57
Q

Describe the Central Respiratiory Chemoreceptors

A

-does not ‘sample’ arterial blood (behind the blood brain barrier within and throughout brain tissue)
-detects tissue PCO2 and or [H+]
-responds slowly to changes (~25-30 seconds)
-peak Ventilatory response is in the order of minutes

58
Q

What is the Duffin Rebreath

A

-a closed circuit
-exhaled air is trapped (CO2 will accumulate)
-hyperoxic CO2 rebreath measures central chemoreceptors sensitivity (temporally & specifically) by blunting the PCRs WITH HYPEROXIA

59
Q

How does Hyperoxic CO2 rebreath measure central chemoreceptor sensitivity?

A

Gives plenty of time to measure the CCRs and ‘blunts’ the PCRs with hyperoxia (less feedback sent to the respiratory centres to change ventilation)

60
Q

What are 2 ways that quantification of O2 and CO2 can be done?

A

-blood analysis (e.g. PCO2, PO2, ETC)
-Respired air analysis

61
Q

How is SaO2 measured

A

-pulse oximetry
-near-infrared spectroscopy (NIRS)

62
Q

How can respiratory gases be manipulated?

A

-rebreath techniques
-fixed fraction of gases
-end-tidal forcing system

63
Q

How do we determine oxygen consumption of the body or a limb?

A

Ficks Equation = VO2=Q (CaO2 -CvO2)

64
Q

What are some considerations for blood gas analysis

A

Blood Sample Handling:
-blood sample must not come in contact with air
-needs to be ANOXIC (no additional air)
-will interact with atmospheric air (H2O, CO2, etc..,)
-errors are common if to little blood is collected (should collect >1.5ml of blood)

65
Q

Why is time to analysis critical when analyzing blood gas

A
  • collected blood still produces CO2 and consumes O2 (red blood cells still metabolically active)
    -PCO2 can rise by 0.1 mmHg per min @ 37ºC
    -PO2 can decline by 0.5-2.3 mmHg per min depending on PO2 levels
    -if analysis needs to be delayed, samples should be placed on ice
66
Q

How is the amount of O2 bound to hemoglobin usually measured?

A

Photometrically

-device emits known signal and records return signal to determine how much light has been absorbed (indicating SO2)
E.G. pulse oximetry and near-infrared spectroscopy (NIRS)

67
Q

What is pulse oximetry?

A

Non invasive, continuous measure of SO2 within arterial blood (indirect)
- light at 2 different wavelengths is transmitted through the finger, forehead or earlobe and reflected back to a receiver

68
Q

What are some limitations of pulse oximetry?

A

COHb (carboxygemoglobin), will give a false high SO2 reading (absorbs wavelengths as well)

-readings less accurate with hypotension

-anemia exaggerates desaturation

-nail polish can affect finger readings

  • can be inaccurate below 80% SO2
69
Q

What is Near-Infared Spectroscopy? (NIRS)

A

-measures the difference in the intensity of transmitted and received light (non-invasive)
-measures relative changes in SO2 within arterial blood, venous blood and tissue (claims to measure tissue oxygenation)

70
Q

What are some limitations of NIRS

A

-very low sensitivity and considerable about of light scatter
-skin and subdermal tissue perfusion contaminates the signal
-very sensitive to external light if not placed properly
-restricted to the microvasculature and cortical areas of the brain (does not measure flow)

71
Q

How is respired gas analyzed?

A

-need continuous measurement of O2 and CO2 within inspired and expired air
-can be used to quantify end-expiration and end-inspiratory gases
-comparing inspired and expired gas concentrations can reflect changes in ventilation, diffusion and perfusion

72
Q

What are END-EXPIRATORY gasses a surrogate measure for

A

Arterial blood gasses (PETO2 &PETCO2)

73
Q

What are END-INSPIRATORY gasses equivalent to

A

Partial pressure of inspired O2 and CO2 (PiO2 & PiCO2)

74
Q

What are some considerations for measuring O2 and CO2 in gas mixtures

A

-must consider (correct for) temp and barometric pressure
-will need to be recalibrated often with a known gas mixture (signals in most systems ‘drift’ over time)

75
Q

What are some methods for controlling end-tidal gasses?

A
  • FIXED FRACTION = breathing from a bag of gas with a fixed fraction of O2 and CO2
    -END-TIDAL FORCING = inspiratory gas constantly changing to maintain end-tidal gases constant (independent of changes in ventilation)
    -REBREATHING = rebreathing from a closed system such that end-tidal PCO2 will climb and end-tidal PO2 will fall
76
Q

What are some disadvantages of the fixed fraction method

A

-human variability in respiratory response to O2 and CO2 (not everyone will breathe the same amount to 10% of O2 (hypoxic Ventilatory response)
-results in differences in end-tidal O2 and CO2 between subjects (stimulus is variable)

77
Q

Advantages of end-tidal forcing

A

-breath-by-breath basis
-very good control of stimulus between participants (i.e. changes in O2 and CO2)
-reduces variability between people

78
Q

Disadvantages of end-tidal forcing

A

-expensive to buy and use
-requires highly trained personnel
-bulky, and not usually portable
-“noisy” which could affect Ventilatory response because you can’t blind participants

Lab Techniques (321) (4 decks)

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