This study is an Observational, Single Center study to evaluate Ability of ∆POX-HR index score to predict HFNC outcome in trauma patients admitted in ICU by comparing the scores of patients categorized as HFNC Success (no need for escalating oxygen therapy from HFNC to NIV/Intubation within 48 hours of initiation) and HFNC Failure (need for escalating oxygen therapy from HFNC to NIV/Intubation within 48 hours of initiation). We hypothesize that Delta POX-HR is a better index for predicting HFNC Success than POX-HR, Delta ROX and ROX index. The primary outcome is predicting requirement of NIV / Intubation after 48 hours (HFNC Failure) using Delta POX-HR at 3 hours after HFNC initiation. The secondary outcomes are predicting requirement of NIV / Intubation after 48 hours (HFNC Failure) using Delta POX-HR at 12, 24 and 48 hours after HFNC initiation.
 

ROX index is a known predictor of intubation requirement after HFNC. Recent studies have shown superiority of POX-HR and Delta POX-HR over ROX index in predicting intubation requirement after HFNC. Most previous studies comparing new indices were conducted during a period marked by high rates of AHRF due to COVID-19. Predictive ability of these indices in Trauma patients having AHRF requiring HFNC has not been validated.

Initiation of HFNC therapy, need for intubation or NIV, or decision to wean a patient off HFNC will be made by the physicians attending to the patient guided by institute protocol but based on clinical assessment on a case-by-case basis keeping patient’s vitals, pH, PaO2, effort tolerance and comfort in view, to ensure the subjects of the study receive the same standard of therapy as regular ICU patients.

The guideline for weaning a patient off HFNC followed will be as per Institute protocol i.e.

•  Patients requiring HFNC therapy will be initiated at 60 L/min of 100% O2 targeting SpO2 > 94%. 
• Once patient is comfortable (Decreased RR and accessory muscle use) and SpO2 is stabilized at 94%, FiO2 will be decreased by 5% till 60% is reached.
• Once FiO2 is approximately equal to 60%, flows will be reduced by 10 L/min till they reach 30 L/min.
  
• Then FiO2 is to be reduced till 30 - 40% and the patient is switched to standard O2 therapy via Face mask thereafter as per institutional protocol.

Adult patients admitted in Trauma Center (JPNATC) General ICUs with AHRF and requiring HFNC that also fulfil all inclusion and exclusion criteria will be recruited for the study. Relevant data for the study will be collected, namely their demographics, vitals and ABG values at five time points (before HFNC initiation, and 3, 12, 24, 48 hours after initiation of HFNC) along with other information during their admission. Data is then used to calculate various indices. (ROX, POX, ROX-HR, POX-HR and their dynamic counterparts calculated by subtracting the initial score from a score at time t). These indices will be analysed and compared in their predictive value. The data collected will be classified as qualitative (or nominal or categorical) and quantitative (or ordinal) described using appropriate tools like Mean (SD) and Frequency (Percentages) respectively. Categorical variables will be compared using the Chi-square test. Non-parametric data was reported as median (interquartile range, IQR) and compared using the median test. Cut-offs for the various indices, rounded off to the nearest 0.01, will be chosen to maximize the sum of sensitivity and specificity based on the receiver operating characteristic (ROC) curves (to satisfy the highest value for Youden index). From these cut-offs, Kaplan–Meier (KM) plots for HFNC success were determined and compared using the log-rank test. Univariate and multivariate Cox proportional regression analysis will be performed to evaluate POX-HR indices. Statistical difference will be considered significant at p ≤ 0.05.