oxygen therapy

Question 1

What are the normal ranges of an arterial blood gas?

Answer 1

• PH 7.35-45
• Paco2 35-45mmhg (4.7-6kpa)
• pao2 80-100mmhg (10.6-13.3kpa)
• HCO3- 22-26mmol/l

Question 2

normal range of o2 sats for young healthy people;

Answer 2

96-98%

Question 3

what are clinical features of hyperaemia?

Answer 3

• altered mental state
• dyspnoea, cyanosis, tachypnoea, arrhythmias, coma
• hyperventilation whenPaO2 <5.3kPa (saturation <72%)
• loss of consciousness at pao2 4.3
• death at po2 2.7

Question 4

who is it risk of acidosis if given high doses of o2?

Answer 4

Chronic hypoxic lung disease

• COPD
• Severe chronic asthma (not acute asthma!)
• Bronchiectasis / CF

Chest wall disease

• Kyphoscoliosis
• Thoracoplasty
• Neuromuscular disease
• Obesity hypoventilation

Question 5

what is the target range of o2 for hypercapnia respect failure?

Answer 5

88 – 92%
RECOMMENDATION:
- Keep PaO2 below 10 kPa and SpO2 <92% in acute COPD

Question 6

clinical indications for o2 therapy?

Answer 6

• Acutely hypoxaemic patients
• Chronically hypoxaemic COPD patients with acute exacerbation
• Chronically hypoxaemic COPD patients who are stable
• Palliative use in advanced malignancy

Question 7

what may be the cause of acute breathlessness with hypoxaemia in patients without significant background lung problems?

Answer 7

• acute pulmonary oedema
• acute pneumonia
• acute pneumothorax
• acute asthma

Question 8

what is the risk of acute breathlessness with hyperaemia? and what is the treatment?

Answer 8

Acute hypoxaemia—> acute cardiac dysrhythmia & organ failure

Treatment
Maximal oxygen treatment
High flow uncontrolled mask

Question 9

how to treat acute exacerbation of COPD- hyperaemia?

Answer 9

• Oxygen should be delivered only by fixed percentage venturi oxygen masks starting at 24%.

nasal cannulae is potentially dangerous since the actual inspired oxygen percentage varies according to the patient’s respiratory characteristics

Question 10

what are the colours for the different percentage venturi masks?

Answer 10

blue - 24%
white- 28% 
yellow - 35%
red - 40%
green- 60%

Question 11

why should you be careful about o2 therapy for COPD?

Answer 11

• They often rely on their hypoxaemic drive
  if you over-correct their pO2 you may switch off their respiratory drive leading to CO2 retention, narcosis & acidosis (& death)

Question 12

how to assess if a COPD patient is ready for LTOT?

Answer 12

check they are unstable state:
- measurements taken on 2 occasions at least 3 weeks apart to demonstrate clinical stability (and no earlier than 8 weeks after an exacerbation)

Question 13

what are indications for LTOT?

Answer 13

COPD patients with pO2 < 7.3 kPa
or
COPD patients with pO2 < 8 kPa in the presence of secondary polycythaemia, nocturnal hypoxaemia, peripheral oedema or evidence of pulmonary hypertension