Table. Overview of differences between the BTS (British Thoracic Society) and the DGP (German Respiratory Society) guidelines for LTOT (taken from Magnet et al. [20]).

		British guideline of the British Thoracic Society (BTS)	German guideline of the German Respiratory Society (DGP)
1.	Blood gas analysis technique	Arterial blood gas analysis (ABG)	Capillary blood gas analysis (CBG)
2.	Criteria for initiation of LTOT in stable patients	Two ABG analyses at least 3 weeks apart	Three CBG analyses within a 4-week period
3.	Initiation of LTOT in patients with COPD after exacerbation	Discharge with oxygen supplementation only if patients cannot manage without oxygen, are breathless, and with SpO2 ≤92% at rest (room air); follow-up assessment of LTOT after 8 weeks	Direct, with later follow-up to re-evaluate indication
4.	Ambulatory oxygen therapy (AOT) for patients without classic indication criteria	Only during rehabilitation	Indicated by resting PaO2 ≤60 mm Hg and by drop in PaO2 during 6MWT or if AOT improves exercise capacity; not indicated by exclusively exercise-induced hypoxemia without increasing dyspnoea and resting PaO2 >55 mm Hg
5.	Nocturnal oxygen therapy	Only for severe congestive heart failure and in combination with NIV for other diseases	No clear statement—further evaluation by sleep laboratory recommended
6.	Titration of O2 flow rates	Based on SpO2 (followed by ABG)	Based on CBG
7.	Follow-up/re-assessment of LTOT	Home visit within 4 weeks, with first re-assessment after 3 months, and thereafter every 6–12 months	Every 3 months (outpatient setting)
8.	Patients who smoke	No contraindications	Conflicting information: LTOT is indicated after avoidance of all inhalative noxae; an overview table however states that there are no contraindications

COPD, chronic obstructive pulmonary disease; LTOT, long-term oxygen therapy; NIV, non-invasive ventilation; PaO₂, arterial partial pressure of oxygen;

SpO₂, blood oxygen saturation; 6MWT, 6-minute walk test