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oxygen therapy Flashcards

1
Q

what factors affect resp function?

A
  • Neural stimulus
  • Resp mechanics: resp muscle/ thoracic cavity effectiveness
  • Airway resistance
  • Elastic recoil of lungs
  • Gas exchange interfaces
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2
Q

what % is oxygen in room air?

A

21%

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3
Q

what is more soluble O2 or CO2?

A

CO2 is 20x more soluble in body tissues than in O2
- CO2 diffuses 20x times faster than O2 in gas exchange interfaces
- Resp disease will first impact O2 transfer before CO2

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4
Q

what is type 1 resp failure?

A

Type 1 resp failure: leads to low O2 and low CO2 – hyperventilation
- Lung failure
- Hypoxic resp failure
- Low oxygen
- Normal or low CO2

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5
Q

what can cause type 1 resp failure?

A

pneumonia, ARDS (acute resp distress syndrome), pulmonary oedema

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6
Q

what is type 2 resp failure?

A

Type 2 resp failure: exhaustion and subsequent reduction to ventilation may lead to increased CO2
- Pump failure
- Hypercapnic resp failure
- High CO2
- Normal or low O2

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7
Q

what can cause type 2 resp failure?

A

obstructive (COPD), NMD

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8
Q

how is CO2 transported within the body?

A
  • 60% of CO2 is as bicarbonate form
  • Driven by enzyme carbonic anhydrase in erythrocytes
  • Generates acid which triggers respiration
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9
Q

how is oxygen transported within the blood?

A
  • Oxygen is poorly dissolved in blood
  • Haem binds to oxygen in blood to form oxyhaemoglobin – acts as a reservoir soaking up different oxygen to decrease PO2 therby maintaining partial pressure gradient across alveoli
  • Releases oxygen to form deoxyhaemoglobin
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10
Q

what is the function of oxygen therapy?

A
  • Increases alveolar concentrations
  • Decreases work of breathing
  • Increases alveolar concentrations
  • Too much can be fatal if delivered incorrectly – too much will decrease resp drive
    Use:
  • Probably most common drug used in medical emergency
  • Used to achieve sats >94%
  • If patient is known to be hypercapnic then aim for 88-92%
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11
Q

when to use high conc O2 therapy?

A
  • Safe in uncomplicated type 1 resp failure – pneumonia, pneumothorax, PE, shock
  • Low oxygen
  • Resp centres functioning normally
  • Little risk of hypoventilation or carbon dioxide retention
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12
Q

how do you give high conc O2 therapy?

A
  • Give 100% oxygen or 15L/min via mask
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13
Q

when would you give low O2 conc therapy?

A
  • Used where patients are at risk of CO2 rentention or low O2 requirements
  • Blunting of hypercapnic drive to due to bicarbonate and mopping of excess H=
  • Drive to breathe now from hypoxic stimulus
  • Too much oxygen can cause hypoventilation and worsening of CO2 retention
  • Patient may carry oxygen with documented target sats
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14
Q

how much O2 can wall oxygen provide?

A

up to 15L/min

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15
Q

how much O2 can oxygen cyclinders provide?

A

Oxygen cylinders – medium (2L/min) or high (4L/min)

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16
Q

what type of oxygen is given in LTOT?

A

Oxygen concentrators – more economical than cylinder, useful in LTOT

17
Q

describe nasal cannula oxygen

A
  • Comfy to wear and easy
  • Non obstructive during eating and drinking
  • Should only go to 4L/min
  • Unable to control exact amount of ispired O2 conc
  • Can lead to dry nasal mucosa and epistaxis – nose bleeds
  • Not secure – can move
  • Used in LTOT
18
Q

how does a non-rebreathe mask work?

A
  • One way valve means most exhaled air escapes so inhaled oxygen concs are higher
  • USED IN EMERGENCY – even if known hypercapnic
19
Q

how is high flow oxygen given?

A
  • High flow nasal cannula – can deliver near 100%
  • Wide- bore nasal cannula – taped to face
  • O2 driven through humidified circuit – to warm up body temp or nasal mucosa would dry in 10 mins
  • Delivers up to 100% O2 therapy
  • Improves work of breathing
20
Q

what is continuous pressure oxygen?

A
  • Tight fitting mask that supplies higher than atmospheric pressure to splint open airways and prevent them from collapsing
  • Can be used with our without oxygen
    CPAP or BIPAP
21
Q

when is CPAP used?

A
  • CPAP – pressure constant throughout resp cycle – used in neonates, mild obstructive sleep apnoea
22
Q

when is BIPAP used?

A
  • BIPAP- pressure drops during expiratory phase to encourage more movement of air in and out of lungs
  • Used in hypercapnic resp failure, severe OSA
  • Gold standard in type 2
23
Q

what is last resort within oxygen therapy?

A

intubation - mechanical ventilation

24
Q

what is criteria for LTOT?

A

<7.3kPa on ABG or 8kPa in pulmonary hypertension

25
Q

when might LTOT be prescribed?

A
  • Only prescribed after careful assessment – cant use Vaseline (petroleum in it)
  • Patient must have stopped smoking due to explosion risk – at least 6mths free
  • 16hrs daily of 1-2L/min may prolong survival in COPD
  • Use: polycythaemia, pulmonary hypertension, peripheral oedema
  • Prescribe using HOOF form – usually with community resp team input
26
Q

what indications for acute therapy in T2RF?

A
  • Exacerbation of longstanding lung disease: COPD, cystic fibrosis, other fibrosis
  • Severe kyphosis – restrictive lung defect caused by physical inability to fully inflate lungs
  • Resp muscle weakness – MND
  • Overdose of drugs causing resp depression – opiates/ benzodiazepines
27
Q

what do you do if someone has decreasing low oxygen sats but is a known chronic hypercapnic?

A
  • If confirmed evidence of hypercapnia- aim for target sats 88-92%, but hypoxia kills faster than hypercapnia
  • Initially give controlled conc of 28%V and adjust appropriately
  • Aim for oxygen sats of 88-92%
  • Monitor patient conditions and ABGs for signs of CO2 retention and acidosis
  • May require BIPAP
28
Q

what occurs during acute severe asthma?

A
  • Initially low oxygen levels and LOW CO2 LEVELS
  • Tachypnoea
  • Resp centres functioning normally
  • As patient tires of resp effort, resp rate falls
  • Can lead to further hypoxia and CO2 retention
  • Continue high flow oxygen and use positive pressure ventilation if required

respiratory (10 decks)

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