Early prediction of high flow nasal cannula therapy outcomes using a modified ROX index incorporating heart rate

Abstract

Background The ROX index (ratio of pulse oximetry/FIO2 to respiratory rate) has been validated to predict high flow nasal cannula therapy (HFNC) outcomes in patients with pneumonia. We evaluated a modified ROX index incorporating heart rate (HR) in patients initiated on HFNC for acute hypoxemic respiratory failure and as a preventative treatment following planned extubation. Methods We performed a prospective observational cohort study of 145 patients treated with HFNC. ROX-HR index was defined as the ratio of ROX index over HR (beats/min), multiplied by a factor of 100. Evaluation was performed using area under the receiving operating characteristic curve (AUROC) and cutoffs assessed for prediction of HFNC failure: defined as the need for mechanical ventilation. Results Ninety-nine (68.3%) and 46 (31.7%) patients were initiated on HFNC for acute hypoxemic respiratory failure and following a planned extubation, respectively. The majority (86.9%) of patients had pneumonia as a primary diagnosis, and 85 (56.6%) patients were immunocompromised. Sixty-one (42.1%) patients required intubation (HFNC failure). Amongst patients on HFNC for acute respiratory failure, HFNC failure was associated with a lower ROX and ROX-HR index recorded at time points between 1 and 48 h. Within the first 12 h, both indices performed with the highest AUROC at 10 h as follows: 0.723 (95% CI 0.605–0.840) and 0.739 (95% CI 0.626–0.853) for the ROX and ROX-HR index respectively. A ROX-HR index of > 6.80 was significantly associated with a lower risk of HFNC failure (hazard ratio 0.301 (95% CI 0.143–0.663)) at 10 h. This association was also observed at 2, 6, 18, and 24h, even with correction for potential confounding factors. For HFNC initiated post-extubation, only the ROX-HR index remained significantly associated with HFNC failure at all recorded time points between 1 and 24 h. A ROX-HR > 8.00 at 10 h was significantly associated with a lower risk of HFNC failure (hazard ratio 0.176 (95% CI 0.051–0.604)). Conclusion While validation studies are required, the ROX-HR index appears to be a promising tool for early identification of treatment failure in patients initiated on HFNC for acute hypoxemic respiratory failure or as a preventative treatment after a planned extubation.

The utility of high-flow nasal oxygen for severe COVID-19 pneumonia in a resource-constrained setting: A multi-centre prospective observational study

“…Preliminary data, mainly case reports and small case series, have also described its potential utility in patients with COVID-19 pneumonia [ 9 , 10 , [28] , [29] , [30] , [31] , [32] ], and usually in combination with awake proning [ 33 , 34 ]. The finding that ROX and mROX can be used as a prediction tool is also consistent with studies of early predictors of HFNO outcome in other forms of respiratory failure [ 19 , 20 ]. We found that ROX performed equivalently to mROX, and thus favoured it, as it comprised fewer input variables.…”

“…However, well-outlined protocolised provincial guidelines for intubation and mechanical ventilation, including score-based risk stratification (based on SOFA score, pre-morbid status, comorbidities and age) were followed [36] . Studies utilising composite physiological scores to determine predictors for the need for intubation inherently suffer from confirmation bias [ 19 , 20 , 37 , 38 ], as even if the ROX index is not formally calculated, the individual components (SpO 2 , FiO 2 and respiratory rate) are incorporated in a Bayesian-type reasoning by the clinician in making the intubation decision. Nevertheless, an objective measure that crystallises the current respiratory parameters, and can potentially reassure the clinician about the safety of continuing with HFNO, is still useful.…”

“…HFNO settings (FiO 2 and flow rate) along with heart rate, respiratory rate and peripheral oxygen saturations were recorded at 6 h post-initiation of HFNO. Using these variables, we calculated the validated ROX score [19] (ratio of oxygen saturation/FiO2 to respiratory rate) at 6 h (ROX-6) and modified ROX score [20] (ROX score divided by heart rate) at 6 h (mROX-6) score. For patients who were intubated before 6 h, the variables at the time that the decision was made that HFNO was failing were recorded.…”

COVID-IRS: A novel predictive score for risk of invasive mechanical ventilation in patients with COVID-19

“…We believe that the biomarkers used in the COVID-IRS scores (respiratory rate, SaO2/FiO2 ratio, LDH, and either IL-6 or NLR), accurately represent relevant aspects of the clinical phenomena seen in severe COVID-19. Both, the respiratory rate and the SaO2/FiO2 ratio evaluate ventilatory function, whose deterioration is the main component associated with COVID-19 mortality [ 9 , 10 ]. The SaO2/FiO2 ratio was used as a surrogate for the PaO2/FiO2 ratio due to its availability and because it maintains a close linear relationship with O2-CO2 exchange and blood oxygenation [ 11 ].…”

Effects of high-flow oxygen therapy on patients with hypoxemia after extubation and predictors of reintubation: a retrospective study based on the MIMIC-IV database

“…According to the results of the machine algorithm, heart rate and PaO 2 are more important features than respiratory rate. In another study, heart rate was also used to modify the ROX index as a predictor of HFNC failure treatment [28]. And SpO 2 , instead of tidal volume, is a physiological parameter monitored routinely.…”