EBQ:Titrated Oxygen Therapy for COPD Exacerbation
In the prehospital setting, does titrating oxygen saturation of patients with presumed AECOPD to SpO2 88-92% compared to high flow oxygen for all decrease prehospital and in-hospital mortality?
Compared to high flow oxygen, titrating supplemental oxygen to a target SpO2 of 88-92% decreased mortality overall, and decreased hypercapnia and acidosis in patients treated according to protocol.
- Patients presenting with dyspnea often receive supplemental oxygen empirically to correct hypoxemia and for symptomatic relief . However, in patients with COPD hyperoxia has been shown to increase the risk of hypercapnia and acidosis, possibly through decreasing respiratory drive and worsening VQ-mismatch by disruption of hypoxic pulmonary vasoconstriction. Furthermore, observational studies have shown an association between high flow oxygen administration and length of stay, ICU admission and mortality.
- In this study, paramedics were randomized to administer either high flow oxygen or oxygen titrated to 88-92% SpO2 to patients with suspected AECOPD along with standard treatments such as nebulized bronchodilators.
- Cluster randomized controlled single centre parallel group trial.
- 214 had confirmed COPD by PFTs in the past 5 years
- Enrolment: June 2006 to July 2007
- Setting: Ambulance service in Hobart, Tasmania, Australia
- All patients (n=405)
- Male: 49%
- Mean Age: 69
- Confirmed diagnosis of COPD (n=214)
- Male: 48%
- Mean Age: 68
- FEV1 from most recent PFT: 42.6% predicted
- Avg Pack years: 45.5
- Age ≥ 35
- Paramedic diagnosis of AECOPD based upon one or more of:
- appropriateness of symptoms
- patient-reported history of COPD
- >10 pack-year smoking history
- Paramedics were randomized to administer one of two treatments:
- Active arm: Oxygen via nasal prongs to target an SpO2 or 88-92% + bronchodilators administered via nebulizer face mask over NPs driven by compressed air.
- Control arm: High flow oxygen via non-rebreather at 8-10 L/min + bronchodilators administered via nebulizer with oxygen 6-8L/min
Prehospital and in-hospital mortality
- 21/226 (9%) in high flow arm vs. 7/179 (4%) in the titrated oxygen arm. RR 0.42 (95% CI: 0.20 to 0.89) p=0.02
Incidence of both invasive and non-invasive ventilation
- 19/213 (9%) in high flow arm vs. 13/166 (8%) in the titrated oxygen arm. RR 0.88 (95% CI: 0.45 to 1.72) p=0.7.
- NIV 9/226 vs 8/179
Confirmed COPD. (Analysis of PFT within last 5 years + medical records by respirologist blinded to treatment allocation)
- 11/117 (9%) in high flow arm vs. 2/97 (2%) in the titrated oxygen arm. RR 0.22 (95%CI: 0.05 to 0.91) p=0.04
- Mean blood gasses (note the low # of patients who had blood gasses taken)
- pH: 7.29 (n=19) in high flow arm vs. 7.35 (n=19) in the titrated oxygen arm. Mean difference 0.06. p=0.11
- paCO2 (mmHg) : 77.8 (n=20) in high flow arm vs. 54.7 (n=20). Mean difference −23.1. p=0.06.
Criticisms & Further Discussion
- Treatment protocol violation occurred in 56% of patients in the titrated oxygen arm based on ambulance records. All violations involved administration of high flow oxygen at some point pre-hospital.
- Very few patients had a blood gas taken within 30 minutes of arrival at hospital. Those who did may represent a subgroup of sicker patients.
- Though hospital staff were instructed to treat according to patient assignment, data regarding whether patients received high flow oxygen in-hospital is largely missing.
- COPD subgroup defined retrospectively. In addition, this group excluded any patients who lacked recent PFTs, likely excluding patients with bona fide AECOPD.
- All patients were admitted to hospital which may not represent the typical disposition of all patients brought to EDs by ambulance for suspected AECOPD.
- Relatively little use of non-invasive ventilation, though this has been shown to improve hypercapnia and other outcomes in AECOPD.
- Nebulized treatments administered differently in each group.
- Single centre study, no blinding post-treatment initiation.
- Australian College of Ambulance Professionals (ACAP)
- FlaemNuova (equipment)