This study was a single-centre, open-label, randomised controlled study conducted in a COVID hospital from February 2021 to April 2021. This clinical study was performed following Ethical Principles for Medical Research involving Human Subjects, outlined in the Helsinki Declaration of 1975 (revised 2013). The protocol was approved by the institutional ethics committee and was registered on ctri.nic.in (CTRI/2021/01/030829). Written informed consent was obtained from all enrolled subjects according to committee recommendations.
Operational definition of moderate category COVID 19 pneumonia: Pneumonia with no signs of severe disease with clinical features consisting of dyspnoea (respiratory rate 24–30/min), hypoxia (SpO2: ≤ 94% [range 90–94%] on room air), fever and cough. Operational definition of severe category COVID 19 pneumonia [5]: Pneumonia with signs of severe disease with clinical features consisting of respiratory distress (respiratory rate > 30/min), hypoxia (SpO2: < 90% on room air), fever and cough.
Keeping the success of oxygen therapy as the primary outcome, a pilot study was conducted with five moderate category COVID 19 patients in each group. Using open epi software version 3, presuming successful outcome in 60% patients in group 1 and 20% patients in group 2 to be true, with confidence of 95%, power 80%, allocation ratio 1: 1, the sample size calculated was a total of 48 patients with 24 patients in each group. A total of 30 patients were taken in each group to compensate for drop outs.
All COVID positive patients of moderate category, of age ≥ 16 years who were eligible and gave informed consent for study inclusion were randomly allocated into two study groups according to the oxygenation device used. Randomisation was done by computer generated randomisation list. In group 1, patients received oxygen therapy with HFNC set at a flow rate of 40–60 L/min, fractional inspiratory oxygen concentration (FiO2) 0.8–1 adjusted to maintain oxygen saturation (SpO2) ≥ 96–99%. The control of FiO2 was achieved by using an air oxygen blender (Draeger ®, Oxymixture MP04200). In group 2, patients received oxygen therapy with NRBM used at a flow rate of 12–15 L/min, FiO2 0.8–1, adjusted to maintain SpO2 ≥ 96–99%. With NRBM, the FiO2 was measured using a portable oxygen analyser. (MX 300, Teledyne® Analytical Instruments) Patients of severe category of COVID pneumonia, Glasgow Coma scale ≤ 12 and those with primary pulmonary disease, tracheostomy or any nasal/facial defect that could impede HFNC or NRBM use were excluded from the study.
Primary outcomes noted were success of oxygen therapy which was defined as not requiring replacement to a higher oxygen delivery device and the time to progression to severe disease. Secondary outcomes noted were, success of oxygen therapy which was defined as not requiring replacement to a higher oxygen delivery device partial pressure of arterial oxygen (PaO2), ratio of partial pressure of oxygen to fraction of inspiratory oxygen concentration (PaO2/FiO2), respiratory rate (RR), heart rate (HR), mean arterial pressure (MAP), number of patients requiring NIV, number of patients requiring endotracheal intubation, time for de-escalation of oxygen therapy to lower FiO2 device and patient satisfaction level. The patient satisfaction level was measured using a visual analogue scale (VAS) [6]. A satisfaction VAS is a 100-mm long horizontal line. There are two adjectives at the beginning and finish that symbolise extremes of satisfaction (i.e., no satisfaction and extreme satisfaction). The patient marked a vertical mark on the 100-mm line to indicate his level of pleasure. The millimetre measurement was translated to the same number of decimal points, ranging from 0 to 10. “Are you comfortable with the oxygen therapy device you're using?” was the actual inquiry. Under the VAS horizontal line, there was a standard instruction on how to fill out the VAS form.
Device failure was considered if the patient progressed to severe category COVID 19 pneumonia while on the study device and required escalation of oxygen therapy [5]. In case of device failure, the decision for shifting to higher oxygen delivery device (including HFNC for the patients in NRBM group or NIV or endotracheal intubation) was done according to the attending anaesthesiologist decision taking respiratory rate, work of breathing and oxygen saturation into account. The patients were followed up daily for monitoring disease progression by various vital parameters up to 14 days.
Vital parameters including HR, MAP, RR, PaO2, PaO2/FiO2, SpO2 and arterial blood gas (ABG) analysis were done as per Intensive Care Unit (ICU) protocol. In both groups, SpO2 was monitored continuously and FiO2 was titrated on an hourly basis to maintain SpO2 between ≥ 96%. The assigned treatment was administered continuously and patients were assessed for treatment success. Patients were weaned to a lower FiO2 oxygen therapy device when the following criteria were met: respiratory rate ≤ 24 breaths/min; no recruitment of accessory muscles during calm breathing; haemodynamic stability (HR < 120/min; MAP between 70 and 110 mmHg with no hemodynamically significant arrhythmias), PaO2 > 80 and SpO2 ≥ 96%. Patients from both groups underwent a standard treatment for COVID 19 with physiotherapy and awake proning protocol.
Statistical analysis was performed with Statistical Package for the Social Sciences (SPSS) software for Windows (Ver. 24.0, IBM Corp., USA). Categorical variables are reported as count and frequency/ per cent while continuous variables are reported as mean and standard deviation or median and interquartile range as appropriate. Associations were tested using student t test for parametrically distributed continuous variables and by using Mann Whitney U test for non-parametrically distributed variables. For categorical variables associations were tested using either Chi square test or Fisher's exact test where appropriate. The alpha level was set at 0.05 for statistical significance.