Table 3 COPD and other conditions requiring controlled or low-dose oxygen therapy (section 8.12)
  • Prior to availability of blood gases, use a 28% Venturi mask at 4 l/min and aim for an oxygen saturation of 88–92% for patients with risk factors for hypercapnia but no prior history of respiratory acidosis. [Grade D]

  • Adjust target range to 94–98% if the Paco2 is normal (unless there is a history of previous NIV or IPPV) and recheck blood gases after 30–60 min [Grade D]

  • Aim at a prespecified saturation range (from alert card) in patients with a history of previous respiratory acidosis. These patients may have their own Venturi mask. In the absence of an oxygen alert card but with a history of previous respiratory failure (use of NIV or IPPV), treatment should be commenced using a 28% oxygen mask at 4 l/min in prehospital care or a 24% Venturi mask at 2–4 l/min in hospital settings with an initial target saturation of 88–92% pending urgent blood gas results. [Grade D]

  • If the saturation remains below 88% in prehospital care despite a 28% Venturi mask, change to nasal cannulae at 2–6 l/min or a simple mask at 5 l/min with target saturation of 88–92%. All at-risk patients with alert cards, previous NIV or IPPV or with saturation <88% in the ambulance should be treated as a high priority. Alert the A&E department that the patient requires immediate senior assessment on arrival at the hospital. [Grade D]

  • If the diagnosis is unknown, patients aged >50 years who are long-term smokers with a history of chronic breathlessness on minor exertion such as walking on level ground and no other known cause of breathlessness should be treated as if having COPD for the purposes of this guideline. Patients with COPD may also use terms such as chronic bronchitis and emphysema to describe their condition but may sometimes mistakenly use “asthma”. FEV1 should be measured on arrival in hospital if possible and should be measured at least once before discharge from hospital in all cases of suspected COPD. [Grade D]

  • Patients with a significant likelihood of severe COPD or other illness that may cause hypercapnic respiratory failure should be triaged as very urgent and blood gases should be measured on arrival in hospital. [Grade D]

  • Blood gases should be rechecked after 30–60 min (or if there is clinical deterioration) even if the initial Paco2 measurement was normal. [Grade D]

  • If the Paco2 is raised but pH is ⩾7.35 ([H+] ⩽45 nmol/l), the patient has probably got long-standing hypercapnia; maintain target range of 88–92% for these patients. Blood gases should be repeated at 30–60 min to check for rising Paco2 or falling pH. [Grade D]

  • If the patient is hypercapnic (Paco2 >6 kPa or 45 mm Hg) and acidotic (pH <7.35 or [H+] >45 nmol/l) consider non-invasive ventilation, especially if acidosis has persisted for more than 30 min despite appropriate therapy. [Grade A]

Additional commentsGrade of recommendation
COPDMay need lower range if acidotic or if known to be very sensitive to oxygen therapy. Ideally use alert cards to guide treatment based on previous blood gas results. Increase flow by 50% if respiratory rate is >30 (see recommendation 32)Grade C
Exacerbation of CFAdmit to regional CF centre if possible; if not, discuss with regional centre or manage according to protocol agreed with regional CF centreGrade D
Ideally use alert cards to guide therapy. Increase flow by 50% if respiratory rate is >30 (see recommendation 32)
Chronic neuromuscular disordersMay require ventilatory support. Risk of hypercapnic respiratory failureGrade D
Chest wall disordersFor acute neuromuscular disorders and subacute conditions such as Guillain-Barré syndrome (see table 4)Grade D
Morbid obesityGrade D
  • CF, cystic fibrosis; COPD, chronic obstructive pulmonary disease; CPAP, continuous positive airway pressure; IPPV, intermittent positive pressure ventilation; NIV, non-invasive ventilation; Paco2, arterial carbon dioxide tension; Spo2, arterial oxygen saturation measured by pulse oximetry.