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R+S phys > Overnight Oximetry > Flashcards

Overnight Oximetry Flashcards

1
Q

What’s the difference between type 1 and type 2 polysomnography?

A

Type 1 = attended sleep study

Type 2 = unattended sleep study

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2
Q

What’s the difference between type 3 and type 4 limited sleep studies?

A

Type 3 = at least 4 channels monitored

Type 4 = Only 1 or 2 monitored parameters

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3
Q

What is the clinical use of overnight oximetry?

A

A continuous overnight measurement during sleep, measuring oxygen saturation (SpO2) & pulse rate

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4
Q

Give 3 uses of OO?

A

1 –> Determine Frequency of O2 desaturations and SpO2

2–> Give information on pulse rate (marker for sleep arousal)

3–> Evaluation of treatments e.g. CPAP

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5
Q

How do you perform OO?

A
  • Performed at home (commonly)
  • Need correct size probe and correct placement
  • Aware of limitations like varnish etc
  • Use Instruction sheet
  • Set up Oximeter with date/time/battery/clean
  • Cover probe with opaque material elimination environmental light
  • Taping lead to back of hand helping securing device in place
  • DO NOT TAPE OVER PROBE
  • Sleep Questionnaire
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6
Q

Which patients wouldn’t be suitable for OO?

A
  • Severe Intellectual Disabilities
  • Communication difficulties
  • Physical difficulties
  • Unstable home
  • Discretionary (serious medico-legal)
  • More extensive studies needed
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7
Q

Advantages of OO?

A
  • Easy to perform
  • Can be done at home
  • Cheaper
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8
Q

Disadvantages of OO?

A
  • Normal Study cannot exclude Sleep Apnoea
  • Cannot distinguish between OSA and CSA
  • Patient Co-operation
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9
Q

What is the ODI?

A

Oxygen Desaturation Index (ODI)

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10
Q

Define ODI?

A
  • The number of 4% desaturations per hour of sleep

- Sometimes called RDI (Respiratory Disturbance Index)

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11
Q

How do we calculate ODI?

A

ODI =

Total no. of desaturations) / (sleep duration in hours

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12
Q

A worked example of ODI?

A

So the patient had 35 desats

and slept for 7 hours

so ODI = 35/7 = 5

units are events per hour

so 5 events per hour

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13
Q

What is a normal ODI?

A

Mild –> 5-14 events per hour

Moderate –> 15-20 events per hour

Severe–> 30+ events per hour

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14
Q

What are the essential features for screening equipment for OSAHS?

A
  • Sampling Frequencies for each signal must be appt
  • Portable
  • Battery Powered or Rechargeable
  • Data must be downloadable and editable
  • Easy to clean/decontaminate
  • Comply with Intl/EU standards
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15
Q

What is the minimal sampling frequency?

A

4Hz

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16
Q

Why can inappropriate sampling frequency lead to?

A

underestimate of desaturation events

17
Q

What is Sample Frequency?

A

The number of samples per second in a sound

18
Q

What is Sample Frequency measured in?

A

Measured in Hertz (Hz) – a unit of frequency

19
Q

What does minimal Samp frequency actually mean in terms of per second?

A

–> minimum sample frequency for SpO2 (4Hz)

–>1 Hz = 1 sample per second

–>4 Hz = 4 samples per second

–>Sample time therefore is reduced to 0.25 sec

20
Q

Relationship between SF and time?

A

↑sample freq = ↓ time

as in a higher frequency means there is less time between every sample

21
Q

What is data averaging?

A
  • the average of repeated SpO2 readings over a specific time interval
22
Q

What is the maximum averaging times?

A

-3s

23
Q

What is the protocol for negative studies?

A
  • must be investigated further using a multi-channel screening system”
24
Q

What is the 4 steps to interpret Interpretation and Pulse Oximetry traces?

A
  1. Quality of data (artefact/length)
  2. Interpretation (Look at traces/data)
  3. Link report to patient/referral
  4. Recommendations/Further actions

–> Services should have SOP’s for reporting

25
Q

What can OO be important for?

A

Patients with suspected or known nocturnal hypoventilation.

26
Q

What is nocturnal hypoventilation?

A

When level of alveolar ventilation is insufficient to meet metabolic needs

-Seen by a rise in CO2 (hypercapnia)

27
Q

Go over interpretation of OO

A

Paper Copy of Slides

R+S phys (17 decks)

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