Quality statement 5	All patients being considered for LTOT should undergo serial blood gas assessments, by the home oxygen assessment service, when stable to confirm both the need for and tolerability of LTOT.
Rationale	Arterial oxygenation can vary with disease course and particularly at exacerbations. Therefore the date of the last exacerbation should be included in the referral for LTOT so that the assessment can be performed during a period of clinical stability (ie ≥8 weeks free from exacerbation of symptoms that require medical management). LTOT should not be prescribed using oximetry alone. All patients requiring LTOT should undergo assessment for suitability using arterial blood gas (ABG) sampling; where ABG sampling is not possible, the current guidelines do allow the use of capillary blood gas (CBG) as an alternative. Two ABG measurements at least 3 weeks apart should be obtained before the need for LTOT is confirmed. An ABG should be repeated after oxygen titration is complete to determine a PaO2 >8 kPa has been achieved without precipitating respiratory acidosis and/or worsening hypercapnia. Patients with PaCO2 >6 kPa at rest should also have blood gases performed after each oxygen titration to monitor for worsening hypercapnia. Assessing patients when clinically unstable, relying on only one blood gas measurement or using CBG may result in overprescribing of LTOT.
Quality measure	Structure: Evidence that patients are stable at the point of assessment through documentation of clinical stability i.e. at least 8 weeks since last exacerbation. Evidence that all patients receiving LTOT have had an initial ABG assessment on air and on titration of oxygen. Evidence of two ABG measurements were performed at least three weeks apart. Evidence that oxygen flow rate has been appropriately increased to achieve PaO2>8kpa without worsening hypercapnia (i.e. increase in PaCO2 by >1kpa).
	Process: The proportion of patients who are assessed for LTOT after a documented period of clinical stability. The proportion of patients receiving LTOT who have had an ABG measurement performed. The proportion of patients with two ABG measurements performed at least three weeks apart prior to commencing LTOT. The proportion of patients who have had a reassessment of PaCO2 after titration of their oxygen flow rate has been completed. Numerator 1: The number of patients initially assessed for LTOT during a documented period of clinical stability. Denominator 1: The number of patients on the home oxygen assessment register assessed for LTOT. Numerator 2: The number of patients receiving LTOT who have documented evidence of a formal baseline ABG assessment that successfully met LTOT qualifying criteria. Denominator 2: The number of patients receiving LTOT on a home oxygen assessment service register. Numerator 3: The number of patients who have had two ABGs performed at least 3 weeks apart prior to commencing LTOT. Denominator 3: The number of patients on the home oxygen assessment register assessed for LTOT. Numerator 4: The number of patients receiving LTOT who have had repeat blood gases to assess for worsening hypercapnia after completion of oxygen titration.
	Denominator 4: The number of patients receiving LTOT on a home oxygen assessment register.
Description of what the quality statement means for each audience	Service providers: Ensure all home oxygen assessment services have the equipment and staff with required skills to perform ABGs. Healthcare professionals: Ensure duration of clinical stability is documented prior to commencing an LTOT assessment. Ensure two qualifying ABGs at least 3 weeks apart are performed prior to commencing LTOT. Ensure titration of oxygen to achieve PaO2 >8 kPa without worsening hypercapnia (>1 kPa rise). Commissioners: Ensure services are adequately resourced with appropriate staff and equipment to undertake high-quality home oxygen assessments. People who require home oxygen: Are assessed rigorously to ensure they receive a home oxygen order appropriate to their needs.
Relevant existing indicators/data sources	Home oxygen assessment service register of assessments and patients on LTOT.
Source references	BTS Guideline for Home Oxygen Use in Adults.3 NHS Service Specification: Home Oxygen Assessment and Review Service 2012.7
Other information	Online Supplementary file 3, BTS Guideline for Home Oxygen Use in Adults (2015): Home Oxygen Assessment Referral Form.3