High VS Low Flow Nasal O2 for Acute Hypercapnic Respiratory Failure

High Flow Nasal Cannula Therapy for Initial Oxygen Administration in Acute Hypercapnic Respiratory Failure - A Comparison Study of Two Current Standards of Care

Chronic lung conditions such as smoking related lung damage lead to breathing fail. This results in accumulation of gases such as carbon-di-oxide in the body especially during periods of illness known as exacerbation. Current management of carbon-di-oxide accumulation is administration of oxygen, nebulisers, antibiotics etc and if necessary, provide a tight fitting mask around the face to provide breathing support. If this fails, then a patient is placed on a mechanical ventilator. The tight fitting mask therapy is also called non-invasive ventilation and is used widely but patients acceptability of the therapy is limited. Providing a high flow of air with some oxygen could potentially provide the same benefit of the non-invasive ventilation and may also be better accepted by patients. Currently the knowledge and evidence from studies suggest a beneficial role for this high flow therapy but this has not been investigated in well designed studies. In the proposed study we aim to investigate whether use of the high flow therapy reduces the need for non-invasive ventilation in patients who present with a recent onset accumulation of carbon-di-oxide in their body due to long-term lung disease. If this shows benefit, it will lead to a bigger trial with patient benefiting by reduction in the non-invasive ventilation or indeed a need for an invasive breathing machine.

Due to the nature of the intervention, the participants , care provider and investigator cannot be blinded but the outcome is objective and data will be analyzed by statistician independent of the study team.

Characterized by an elevated arterial CO2 (PaCO2) level of > 6kPa due to ventilatory failure. The ventilatory failure relates to the imbalance between the respiratory demand and the capacity of the respiratory system to match the demand.

Characterized by an elevated arterial CO2 (PaCO2) level of > 6kPa due to ventilatory failure. The ventilatory failure relates to the imbalance between the respiratory demand and the capacity of the respiratory system to match the demand.

Controlled oxygen administration using at least 20 L/min of flow rate and titrated up as tolerated. Titration of supplemental oxygen to an arterial saturation between 88 - 92%.

Controlled oxygen administration using (venturi mask or nasal cannulae) titrated to an arterial saturation between 88 - 92% as the initial oxygen administration method with a flow rate of <20 L/min.

From the date of randomization until the date of first documented admission to ICU, assessed up to 12 weeks.

From the date of randomization until the date of death or hospital discharge, whichever came first, assessed up to 12 weeks.

From the date of ICU admission until the date of last documented ICU discharge or date of death from any cause, whichever came first, assessed up to 12 weeks.

From the date of randomization until hospital discharge or date of death from any cause, whichever came first, assessed up to 12 weeks.

Dyspnoea will be assessed assessment using a visual analogue scale (VAS), score range 0-10, higher values represent a better outcome)) if patient has capacity or the Likert scale (score range 1-5; higher values represent a better outcome) to be completed by the clinical team (doctor/nurse/physio) if the patient lacks capacity.

Comfort will be assessed assessment using a visual analogue scale (VAS), score range 0-10, higher values represent a better outcome)) if patient has capacity or the Likert scale (score range 1-5; higher values represent a better outcome) to be completed by the clinical team (doctor/nurse/physio) if the patient lacks capacity.

Inclusion Criteria: Adult patients > 18 years of age Acute Hypercapnic respiratory failure with pH < 7.35 and pCO2 > 6 KPa Exclusion Criteria: Age < 18 years Pregnant or Breast-Feeding Patient cannot read and understand English Hypercapnia secondary to a drug toxicity or non-pulmonary aetiology Hypercapnia secondary to exacerbation of asthma Contraindication to NIV Contraindication to HFNC Not for escalation to NIV pH < 7.15 GCS 8 or less Shock defined as systolic < 90 mmHg or a reduction by 20mmHg from usual systolic BP despite volume resuscitation Respiratory or cardio-respiratory arrest Any other indication that requires immediate invasive/non-invasive mechanical ventilation

IPD may be shared on request to the Principal Investigator and will be decided on a case by case basis.

Alnajada A, Blackwood B, Mobrad A, Akhtar A, Shyamsundar M. High-flow nasal cannula therapy for initial oxygen administration in acute hypercapnic respiratory failure: study protocol of randomised controlled unblinded trial. BMJ Open Respir Res. 2021 Jan;8(1):e000853. doi: 10.1136/bmjresp-2020-000853.