The ROX index as a predictor of high-flow nasal cannula outcome in pneumonia patients with acute hypoxemic respiratory failure: a systematic review and meta-analysis

Respiratory rate-oxygenation index and National Early Warning Score 2 score are associated with orotracheal intubation in patients with cardiogenic pulmonary oedema

BACKGROUND

This study evaluates the association between the respiratory rate-oxygenation (ROX) index and the National Early Warning Score 2 (NEWS2) score with orotracheal intubation (OTI) and in-hospital mortality in patients with cardiogenic pulmonary oedema (CPE).

METHODS

This retrospective observational study enrolled patients aged 18 years or older who had developed CPE at admission or during hospital stay. Demographic, clinical, and laboratory data were collected within the first 24 h of CPE onset from the electronic records. The outcomes needed for OTI during 24 h after CPE diagnosis and in-hospital mortality were also collected. The ROX index and NEWS2 were calculated using variables collected at CPE occurrence.

RESULTS

Two hundred eighty-six patients with CPE were evaluated; however, 68 patients were excluded due to the absence of variables to calculate the ROX index. Thus, we included 218 patients in the analysis. The mean age was 67.8 ± 14.0 years, 51.8% were female, the median of the ROX index was 9.29 (6.06-13.05), and the median of the NEWS2 was 10.0 (7.0-12.0). Amongst these patients, 28.0% needed OTI 24 h after CPE and 30.3% died. In univariate analysis, lower values of the ROX index and higher values of the NEWS2 were associated with OTI. There was no association with mortality. In logistic regression models, the ROX index and NEWS2 were associated with OTI when adjusted by smoking, time of CPE, and endovenous nitrate and morphine (ROX index: odds ratio [OR] = 0.908, 95% confidence interval [CI] = 0.843-0.979, p = 0.012; NEWS2: OR = 1.261, 95% CI = 1.049-1.514, p = 0.013) and when adjusted by age, sex, and time of CPE (at admission or during hospital stay; ROX index: OR = 0.909, 95% CI = 0.847-0.976, p = 0.008; NEWS2: OR = 1.190, 95% CI = 1.015-1.396, p = 0.032).

CONCLUSIONS

The ROX index and NEWS2 were associated with OTI in CPE despite no association with mortality.

High-Flow Nasal Cannula Application After Extubation in Acute Respiratory Failure Patients

Background: The optimal timing of high-flow nasal cannula (HFNC) application in acute respiratory failure patients remains uncertain. This study aimed to investigate the impact of HFNC on the outcomes of patients with acute respiratory failure, focusing on its use after extubation. Methods: This multicenter retrospective study enrolled adult acute respiratory failure patients requiring invasive mechanical ventilation during the first major outbreak of the COVID-19 pandemic in Taiwan from April to July 2021. Endpoints included prognosis after extubation as 28-day post-extubation mortality. Results: Among the patients, 107 received HFNC before intubation and 461 received conventional oxygen therapy (COT). Pre-intubation HFNC failure did not significantly affect hospital mortality but was associated with prolonged durations of mechanical ventilation and intensive care unit stay. Among 375 patients who underwent planned extubation, 158 received post-extubation HFNC and 217 received COT. HFNC application after extubation was associated with significantly reduced post-extubation 28-day mortality compared with COT. Conclusions: HFNC application after extubation is associated with reduced post-extubation 28-day mortality risks in acute respiratory failure patients who received planned extubation.

Patient-Self Inflicted Lung Injury (P-SILI): An Insight into the Pathophysiology of Lung Injury and Management

Acute respiratory distress syndrome (ARDS) is a heterogeneous group of disease entities that are associated with acute hypoxic respiratory failure and significant morbidity and mortality. With a better understanding and phenotyping of lung injury, novel pathophysiologic mechanisms demonstrate the impact of a patient's excessive spontaneous breathing effort on perpetuating lung injury. Patient self-inflicted lung injury (P-SILI) is a recently identified phenomenon that delves into the impact of spontaneous breathing on respiratory mechanics in patients with lung injury. While the studies are hypothesis-generating and have been demonstrated in animal and human studies, further clinical trials are needed to identify its impact on ARDS management. The purpose of this review article is to highlight the physiologic mechanisms of P-SILI, novel tools and methods to detect P-SILI, and to review the current literature on non-invasive and invasive respiratory management in patients with ARDS.

Factors associated with the effectiveness of high-flow therapy in patients with acute hypoxemic respiratory failure: An observational study

BACKWARD

The COVID-19 pandemic has severely tested global health systems. Non-invasive respiratory support, especially combining high-flow nasal cannula (HFNC) and continuous positive airway pressure, has effectively treated COVID-19 induced Acute Hypoxemic Respiratory Failure and reduced mortality. However, HFNC alone is more comfortable, better tolerated, and less costly than non-invasive ventilation. Understanding which patients benefit from HFNC monotherapy versus combined therapies is essential.

METHODS

This observational study included patients admitted to the intermediate respiratory care unit of a COVID-19 hospital between December 2020 and September 2021. All patients treated with HFNC were included (n = 1301). HFNC failure was defined as the need for escalated therapy (non-invasive ventilation, intubation) or death. Epidemiological, clinical, non-invasive respiratory support parameters, and laboratory data were collected, and a multivariable analysis identified key determinants.

RESULTS

HFNC was successful in 39.9 % of patients. (n = 511) Risk factors for HFNC failure included increased age, male gender, obesity, obstructive sleep apnea, higher respiratory rate, initial SpO2/FiO2 ≤ 148, and initial PaO2/FiO2 ≤ 100. An increase in the ROX Index at 24 h and slower disease progression were associated with successful treatment. These findings led to the developmet of an index to identify patients who benefit most from HFNC monotherapy.

CONCLUSIONS

HFNC monotherapy can be effective for a specific profile of patients with Acute Hypoxemic Respiratory Failure due to COVID-19. This tool may help manage these patients more appropriately. Further studies are needed to determine if these findings can be applied to Acute Hypoxemic Respiratory Failure caused by other pathologies.

IMPLICATIONS FOR CLINICAL PRACTICE

This study underscores the importance of early identification and management of patients at risk of HFNC failure in intermediate respiratory care units. By recognizing factors such as age, comorbidities, and respiratory indices, healthcare providers can implement targeted strategies to enhance HFNC success. These strategies may include more stringent monitoring, tailored respiratory support, and timely escalation to more intensive therapies if needed. Our findings highlight the need for a comprehensive approach to managing severe respiratory failure in critical care settings, ultimately improving patient outcomes and reducing the burden on healthcare systems.

Predictive performance of ROX index and its variations for NIV failure

OBJECTIVE

To determine whether the ROX index and its variations can predict the risk of intubation in ICU patients receiving NIV ventilation using large public ICU databases.

DESIGN

Retrospective observational cohort study.

SETTING

Patient data was extracted from both the AmsterdamUMCdb and the MIMIC-IV ICU databases, which contained data related to 20,109 and 50,920 unique patients.

PATIENTS

Non-invasively mechanically ventilated.

INTERVENTIONS

Retrospective review of variables.

MAIN VARIABLES OF INTEREST

To assess the predictive values of models for each index, the ROX and its variations mROX, ROX-HR and mROX-HR were calculated based on mean values of SpO2, respiratory rate, FiO2 and PaO2 from 2-h windows within the first 12 h of NIV.

RESULTS

3344 patients were eligible for analysis of which 1344 were intubated, died or returned to NIV within 24 h of ending NIV. NIV failure group had higher SOFA scores and higher CRP levels at admission. There was no difference in duration of NIV therapy or 28-day mortality, but patients who failed NIV had longer length of stay. The best performing index was ROX with an AUROC of 0.626 at 10-12 h. All other indices for all other time windows were less discriminating.

CONCLUSIONS

The performance of ROX index and its variations to predict NIV failure in ICU patients across large public ICU databases was moderate at best and cannot currently be recommended for clinical decision support.

Predictors of high-flow nasal cannula (HFNC) failure in severe community-acquired pneumonia or COVID-19

The aim was to identify predictors for early identification of HFNC failure risk in patients with severe community-acquired (CAP) pneumonia or COVID-19. Data from adult critically ill patients admitted with CAP or COVID-19 and the need for ventilatory support were retrospectively analysed. HFNC failure was defined as the need for invasive ventilation or death before intubation. 60 patients with CAP and 185 with COVID-19 were included. 27 (45%) patients with CAP and 69 (37.3%) patients with COVID-19 showed HFNC failure. Lower oxygenation index, lower respiratory oxygenation (ROX) index, and higher respiratory rate at the start of HFNC were significantly associated with HFNC failure. ROC-analysis identified a respiratory rate of 27/min as the optimal cut-off for predicting HFNC failure, with a specificity of 59% and a sensitivity of 75%, and an oxygenation index after HFNC initiation of 99.6 (specificity 81%, sensitivity 74%). In COVID-19, an elevated CRB65-score at hospital admission and at HFNC-initiation was significantly associated with HFNC failure. In CAP and COVID patients an oxygenation index < 99.6, a respiratory rate > 27/min and a ROX index < 4.88 were predictors for HFNC failure whereas a CRB65 score > 3 at hospital admission and > 2 at HFNC start was predictive for HFNC failure in COVID-19.

Predicting High-Flow Nasal Cannula Oxygen Therapy Failure in Patients With Acute Hypoxaemic Respiratory Failure Using Machine Learning: Model Development and External Validation

AIMS AND OBJECTIVES

To develop and validate a prediction model for high-flow nasal cannula (HFNC) failure in patients with acute hypoxaemic respiratory failure (AHRF).

BACKGROUND

AHRF accounts for a major proportion of intensive care unit (ICU) admissions and is associated with high mortality. HFNC is a non-invasive respiratory support technique that can improve patient oxygenation. However, HFNC failure, defined as the need for escalation to invasive mechanical ventilation, can lead to delayed intubation, prolonged mechanical ventilation and increased risk of mortality. Timely and accurate prediction of HFNC failure has important clinical implications. Machine learning (ML) can improve clinical prediction.

DESIGN

Multicentre observational study.

METHODS

This study analysed 581 patients from an academic medical centre in Boston and 180 patients from Guangzhou, China treated with HFNC for AHRF. The Boston dataset was randomly divided into a training set (90%, n = 522) and an internal validation set (10%, n = 59), and the model was externally validated using the Guangzhou dataset (n = 180). A random forest (RF)-based feature selection method was used to identify predictive factors. Nine machine learning algorithms were selected to build the predictive model. The area under the receiver operating characteristic curve (AUC) and performance evaluation parameters were used to evaluate the models.

RESULTS

The final model included 38 features selected using the RF method, with additional input from clinical specialists. Models based on ensemble learning outperformed other models (internal validation AUC: 0.83; external validation AUC: 0.75). Important predictors of HFNC failure include Glasgow Coma Scale scores and Sequential Organ Failure Assessment scores, albumin levels measured during HFNC treatment, ROX index at ICU admission and sepsis.

CONCLUSIONS

This study developed an interpretable ML model that accurately predicts the risk of HFNC failure in patients with AHRF.

RELEVANCE TO CLINICAL PRACTICE

Clinicians and nurses can use ML models for early risk assessment and decision support in AHRF patients receiving HFNC.

REPORTING METHOD

TRIPOD checklist for prediction model studies was followed in this study.

PATIENT OR PUBLIC CONTRIBUTION

Patients were involved in the sample of the study.

Highlights from the Respiratory Failure and Mechanical Ventilation Conference 2024

The Respiratory Intensive Care Assembly of the European Respiratory Society gathered in Berlin to organise the third Respiratory Failure and Mechanical Ventilation Conference in February 2024. The conference covered key points of acute and chronic respiratory failure in adults. During the 3-day conference ventilatory strategies, patient selection, diagnostic approaches, treatment and health-related quality of life topics were addressed by a panel of international experts. In this article, lectures delivered during the event have been summarised by early career members of the Assembly and take-home messages highlighted.

NEWS2, S/F-ratio and ROX-index at emergency department for the prediction of adverse outcomes in COVID-19 patients: An external validation study

BACKGROUND

In the context of the COVID-19 pandemic, the early and accurate identification of patients at risk of deterioration was crucial in overcrowded and resource-limited emergency departments. This study conducts an external validation for the evaluation of the performance of the National Early Warning Score 2 (NEWS2), the S/F ratio, and the ROX index at ED admission in a large cohort of COVID-19 patients from Colombia, South America, assessing the net clinical benefit with decision curve analysis.

METHODS

A prospective cohort study was conducted on 6907 adult patients with confirmed COVID-19 admitted to a tertiary care ED in Colombia. The study evaluated the diagnostic performance of NEWS2, S/F ratio, and ROX index scores at ED admission using the area under the receiver operating characteristic curve (AUROC) for discrimination, calibration, and decision curve analysis for the prediction of intensive care unit admission, invasive mechanical ventilation, and in-hospital mortality.

RESULTS

We included 6907 patients who presented to the ED with confirmed SARS-CoV-2 infection from March 2020 to November 2021. Mean age was 51 (35-65) years and 50.4% of patients were males. The rate of intensive care unit admission was 28%, and in-hospital death was 9.8%. All three scores have good discriminatory performance for the three outcomes based on the AUROC. S/F ratio showed miscalibration at low predicted probabilities and decision curve analysis indicated that the NEWS2 score provided a greater net benefit compared to other scores across at a 10% threshold to decide ED admission at a high-level of care facility.

CONCLUSIONS

The NEWS2, S/F ratio, and ROX index at ED admission have good discriminatory performances in COVID-19 patients for the prediction of adverse outcomes, but the NEWS2 score has a higher net benefit underscoring its clinical utility in optimizing patient management and resource allocation in emergency settings.

The respiratory oxygenation index for identifying the risk of orotracheal intubation in COVID-19 patients receiving high-flow nasal cannula oxygen

OBJECTIVE

To assess whether the respiratory oxygenation index (ROX index) measured after the start of high-flow nasal cannula oxygen therapy can help identify the need for intubation in patients with acute respiratory failure due to coronavirus disease 2019.

METHODS

This retrospective, observational, multicenter study was conducted at the intensive care units of six Brazilian hospitals from March to December 2020. The primary outcome was the need for intubation up to 7 days after starting the high-flow nasal cannula.

RESULTS

A total of 444 patients were included in the study, and 261 (58.7%) were subjected to intubation. An analysis of the area under the receiver operating characteristic curve (AUROC) showed that the ability to discriminate between successful and failed high-flow nasal cannula oxygen therapy within 7 days was greater for the ROX index measured at 24 hours (AUROC 0.80; 95%CI 0.76 - 0.84). The median interval between high-flow nasal cannula initiation and intubation was 24 hours (24 - 72), and the most accurate predictor of intubation obtained before 24 hours was the ROX index measured at 12 hours (AUROC 0.75; 95%CI 0.70 - 0.79). Kaplan-Meier curves revealed a greater probability of intubation within 7 days in patients with a ROX index ≤ 5.54 at 12 hours (hazard ratio 3.07; 95%CI 2.24 - 4.20) and ≤ 5.96 at 24 hours (hazard ratio 5.15; 95%CI 3.65 - 7.27).

CONCLUSION

The ROX index can aid in the early identification of patients with acute respiratory failure due to COVID-19 who will progress to the failure of high-flow nasal cannula supportive therapy and the need for intubation.

Can the ROX index predict high-flow nasal cannula failure in children under 2 with lower respiratory tract infection?

OBJECTIVE

This study evaluates the ROX index's accuracy in predicting the success or failure of high-flow nasal cannula (HFNC) therapy in children under 2 years with acute respiratory failure (ARF) from lower respiratory tract infections.

METHODS

From January 2018 to 2021 we conducted this multicenter retrospective cohort study, which included patients aged 2-24 months. We aimed to assess HFNC therapy outcomes as either success or failure. The analysis covered patient demographics, diagnoses, vital signs, and ROX index values at intervals from 0 to 48 h after initiating HFNC. We used bivariate analysis, repeated measures ANOVA, multivariate logistic regression, and the area under the receiver operating characteristic (AUC-ROC) curve for statistical analysis.

RESULTS

The study involved 529 patients from six centers, with 198 females (37%) and a median age of 9 months (IQR: 3-15 months). HFNC therapy failed in 38% of cases. We observed significant variability in failure rates across different centers and physicians (p < .001). The ROX index was significantly associated with HFNC outcomes at all time points, showing an increasing trend in success cases over time (p < .001), but not in HFNC failure cases. Its predictive ability is limited, with AUC-ROC values ranging from 0.56 at the start to 0.67 at 48 h.

CONCLUSION

While the ROX index is associated with HFNC outcomes in children under 2 years, its predictive ability is modest, impacted by significant variability among patients, physicians, and centers. These findings emphasize the need for more reliable predictive tools for HFNC therapy in this patient population.

Racial Differences in Accuracy of Predictive Models for High-Flow Nasal Cannula Failure in COVID-19

OBJECTIVES

To develop and validate machine learning (ML) models to predict high-flow nasal cannula (HFNC) failure in COVID-19, compare their performance to the respiratory rate-oxygenation (ROX) index, and evaluate model accuracy by self-reported race.

DESIGN

Retrospective cohort study.

SETTING

Four Emory University Hospitals in Atlanta, GA.

PATIENTS

Adult patients hospitalized with COVID-19 between March 2020 and April 2022 who received HFNC therapy within 24 hours of ICU admission were included.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Four types of supervised ML models were developed for predicting HFNC failure (defined as intubation or death within 7 d of HFNC initiation), using routine clinical variables from the first 24 hours of ICU admission. Models were trained on the first 60% (n = 594) of admissions and validated on the latter 40% (n = 390) of admissions to simulate prospective implementation. Among 984 patients included, 317 patients (32.2%) developed HFNC failure. eXtreme Gradient Boosting (XGB) model had the highest area under the receiver-operator characteristic curve (AUROC) for predicting HFNC failure (0.707), and was the only model with significantly better performance than the ROX index (AUROC 0.616). XGB model had significantly worse performance in Black patients compared with White patients (AUROC 0.663 vs. 0.808, p = 0.02). Racial differences in the XGB model were reduced and no longer statistically significant when restricted to patients with nonmissing arterial blood gas data, and when XGB model was developed to predict mortality (rather than the composite outcome of failure, which could be influenced by biased clinical decisions for intubation).

CONCLUSIONS

Our XGB model had better discrimination for predicting HFNC failure in COVID-19 than the ROX index, but had racial differences in accuracy of predictions. Further studies are needed to understand and mitigate potential sources of biases in clinical ML models and to improve their equitability.

Effect of high flow nasal oxygen on inspiratory effort of patients with acute hypoxic respiratory failure and do not intubate orders

High flow nasal oxygen (HFNO) is recommended as a first-line respiratory support during acute hypoxic respiratory failure (AHRF) and represents a proportionate treatment option for patients with do not intubate (DNI) orders. The aim of the study is to assess the effect of HFNO on inspiratory effort as assessed by esophageal manometry in a population of DNI patients suffering from AHRF. Patients with AHRF and DNI orders admitted to Respiratory intermediate Care Unit between January 1st, 2018 and May 31st, 2023 to receive HFNO and subjected to esophageal manometry were enrolled. Esophageal pressure swing (ΔPes), clinical variables before and after 2 h of HFNO and clinical outcome (including HFNO failure) were collected and compared as appropriate. The change in physiological and clinical parameters according to the intensity of baseline breathing effort was assessed and the correlation between baseline ΔPes values and the relative change in breathing effort and clinical variables after 2 h of HFNO was explored. Eighty-two consecutive patients were enrolled according to sample size calculation. Two hours after HFNO start, patients presented significant improvement in ΔPes (12 VS 16 cmH2O, p < 0.0001), respiratory rate (RR) (22 VS 28 bpm, p < 0.0001), PaO2/FiO2 (133 VS 126 mmHg, p < 0.0001), Heart rate, Acidosis, Consciousness, Oxygenation and respiratory rate (HACOR) score, (4 VS 6, p < 0.0001), Respiratory rate Oxygenation (ROX) index (8.5 VS 6.1, p < 0.0001) and BORG (1 VS 4, p < 000.1). Patients with baseline ΔPes below 20 cmH2O where those who improved all the explored variables, while patients with baseline ΔPes above 30 cmH2O did not report significant changes in physiological or clinical features. A significant correlation was found between baseline ΔPes values and after 2 h of HFNO (R2 = 0.9, p < 0.0001). ΔPes change 2 h after HFNO significantly correlated with change in BORG (p < 0.0001), ROX index (p < 0.0001), HACOR score (p < 0.001) and RR (p < 0.001). In DNI patients with AHRF, HFNO was effective in reducing breathing effort and improving respiratory and clinical variables only for those patients with not excessive inspiratory effort.

Physical and respiratory therapy in the critically ill patient with obesity: a narrative review

Obesity has become increasingly prevalent in the intensive care unit, presenting a significant challenge for healthcare systems and professionals, including rehabilitation teams. Caring for critically ill patients with obesity involves addressing complex issues. Despite the well-established and safe practice of early mobilization during critical illness, in rehabilitation matters, the diverse clinical disturbances and scenarios within the obese patient population necessitate a comprehensive understanding. This includes recognizing the importance of metabolic support, both non-invasive and invasive ventilatory support, and their weaning processes as essential prerequisites. Physiotherapists, working collaboratively with a multidisciplinary team, play a crucial role in ensuring proper assessment and functional rehabilitation in the critical care setting. This review aims to provide critical insights into the key management and rehabilitation principles for obese patients in the intensive care unit.

ROX index as a predictor of failure of high-flow nasal cannula in infants with bronchiolitis

High-flow nasal cannula (HFNC) is a relatively recent therapy that has been used to treat respiratory failure. Until now, the criterion for failure requiring escalation to other forms of ventilatory support has remained unclear. This study evaluated how the ROX index predicts the success or failure of HFNC in infants with bronchiolitis. A prospective, observational, multicenter study was conducted in 2 pediatric ICUs. The data were collected at 7 moments. Patients were categorized into failure and success groups according to HFNC. A total of 102 infants were included, 18(17.6%) of whom failed HFNC therapy. For the ROX index, significant differences were observed between the failure 5.8(95%CI 4.7-7.1) and success 7.7(95%CI 7.2-8.2) groups (p = 0.005) at the 12 h evaluation. According to the analysis of the performance of the ROX index, the AUC at 12 h was 0.716(95%CI 0.591-0.842; p = 0.016). The best cutoff range for the ROX index at 12 h was 6.50-7.18, with a sensitivity of 42% and a specificity of 66% at the cutoff of 6.50, and a sensitivity of 92% and a specificity of 54% at the cutoff of 7.18. We concluded that the ROX index could be effective at predicting the failure of HFNC therapy in infants with bronchiolitis beginning at 12 h after installation.

Daily ROX index can predict transitioning to mechanical ventilation within the next 24 h in COVID-19 patients on HFNC

INTRODUCTION

High flow nasal cannula (HFNC) is used to prevent invasive ventilation in COVID-19-associated hypoxemia. The respiratory rate‑oxygenation (ROX) index has been reported to predict failure of HFNC in patients with COVID-19 pneumonia during the intensive care unit stay when measured in first hours of therapy. However, the clinical course of ICU patients may change substantially in the first days of admission. The objective of this study was to investigate whether ROX index obtained in the first four days of ICU admission could predict the need for invasive respiratory support within the next 24 h of measurements.

METHODS

A retrospective cross-sectional study was performed using a database that included adult patients with COVID-19 pneumonia treated in the ICU. Patients were followed from ICU admission and ROX index was calculated daily on HFNC. Receiver operating characteristics curves (ROCs) were performed.

RESULTS

Two hundred forty-nine patients were enrolled, 48% of whom require mechanical ventilation (MV). The area under the ROC of the pooled 4-day values of the ROX index as a predictor of transition from HFNC to MV within 24 h of measurements was 0.86 (95%CI 0.83 to 0.88, P < 0.001) with a cutoff point of 4.06.

CONCLUSION

In COVID-19 patients in high flow nasal cannula, daily ROX index measurements successfully predicted transition to mechanical ventilation within the next 24 h.

High-Flow Nasal Cannula oxygen therapy in COVID-19: retrospective analysis of clinical outcomes - single center experience

Background

High-Flow Nasal Cannula (HFNC) oxygen therapy emerged as the therapy of choice in COVID-19-related pneumonia and moderate to severe acute hypoxemic respiratory failure (AHRF). HFNC oxygen therapy in COVID-19 has been recommended based its use to treat AHRF of other etiologies, and studies on assessing outcomes in COVID-19 patients are highly needed. This study aimed to examine outcomes in COVID-19 patients with pneumonia and severe AHRF treated with HFNC.

Materials and methods

The study included 235 COVID-19 patients with pneumonia treated with HFNC. Data extracted from medical records included demographic characteristics, comorbidities, laboratory parameters, clinical and oxygenation status, clinical complications, as well as the length of hospital stay. Patients were segregated into two groups based on their oxygen therapy needs: HDU group, those who exclusively required HFNC and ICU group, those whose oxygen therapy needed to be escalated at some point of hospital stay. The primary outcome was the need for respiratory support escalation (noninvasive or invasive mechanical ventilation) and the secondary outcome was the in-hospital all-cause mortality.

Results

The primary outcome was met in 113 (48%) of patients. The overall mortality was 70%, significantly higher in the ICU group [102 (90.2%) vs. 62 (50.1%), p < 0.001]. The rate of intrahospital infections was significantly higher in the ICU group while there were no significant differences in the length of hospital stay between the groups. The ICU group exhibited significant increases in D-dimer, NLR, and NEWS values, accompanied by a significant decrease in the SaO2/FiO2 ratio. The multivariable COX proportional regression analysis identified malignancy, higher levels of 4C Mortality Score and NEWS2 as significant predictors of mortality.

Conclusion

High-Flow Nasal Cannula oxygen therapy is a safe type of respiratory support in patients with COVID-19 pneumonia and acute hypoxemic respiratory failure with significantly less possibility for emergence of intrahospital infections. In 52% of patients, HFNC was successful in treating AHRF in COVID-19 patients. Overall, mortality in COVID-19 pneumonia with AHRF is still very high, especially in patients treated with noninvasive/invasive mechanical ventilation.

Performance of the ROX index in predicting high flow nasal cannula failure in COVID-19 patients: a systematic review and meta-analysis

COVID-19 patients with acute hypoxemic respiratory failure (AHRF) benefit from high flow nasal cannula (HFNC) oxygen therapy. However, delays in initiating invasive ventilation after HFNC failure are associated with poorer outcomes. The respiratory oxygenation (ROX) index, combining SpO2/FiO2 and respiratory rate, can predict HFNC failure. This meta-analysis evaluated the optimal ROX index cut-offs in predicting HFNC failure among COVID-19 patients at different measurement timings and clinical settings. Three databases were searched for eligible papers. From each study, we reconstructed the confusion matrices at different cut-offs, fitted linear mixed models to estimate the ROX index distribution function, and derived the area under the summary receiver operator characteristic curve (sAUC) and optimal cut-offs to predict HFNC failure. 24 studies containing 4790 patients were included. Overall sAUC was 0.771 (95% CI: 0.666-0.847) (optimal cut-off: 5.23, sensitivity: 0.732, specificity: 0.690). The cut-off values to achieve 80%, 90% sensitivity, 80%, 90% specificity were 5.70, 6.69, 4.45, 3.37, respectively. We stratified the analysis by ROX measurement time and estimated optimal cut-offs and cut-offs to achieve 80% sensitivity and specificity. For 2-6 h and 6-12 h post-HFNC initiation, we propose the use of 80% specific cut-offs to rule in HFNC failure of < 5.33 and < 3.69, respectively. For 12-24 h post-HFNC initiation, we propose the use of the 80% sensitive cut-off of > 6.07 to rule out HFNC failure. Our analysis confirms the overall utility of the ROX index in risk stratification of COVID-19 patients with AHRF receiving HFNC and provides potentially useful cut-offs for different times from HFNC initiation.

The COVID-19 Driving Force: How It Shaped the Evidence of Non-Invasive Respiratory Support

During the COVID-19 pandemic, the use of non-invasive respiratory support (NIRS) became crucial in treating patients with acute hypoxemic respiratory failure. Despite the fear of viral aerosolization, non-invasive respiratory support has gained attention as a way to alleviate ICU overcrowding and reduce the risks associated with intubation. The COVID-19 pandemic has led to an unprecedented increased demand for research, resulting in numerous publications on observational studies, clinical trials, reviews, and meta-analyses in the past three years. This comprehensive narrative overview describes the physiological rationale, pre-COVID-19 evidence, and results of observational studies and randomized control trials regarding the use of high-flow nasal oxygen, non-invasive mechanical ventilation, and continuous positive airway pressure in adult patients with COVID-19 and associated acute hypoxemic respiratory failure. The review also highlights the significance of guidelines and recommendations provided by international societies and the need for further well-designed research to determine the optimal use of NIRS in treating this population.

An observational study on the timing of intubation and outcome in COVID-19 ARDS patients who were treated with high flow nasal oxygen prior to invasive mechanical ventilation: A time series analysis (InOutHFNO trial)

Background and Aims

Prolonged high flow nasal oxygen (HFNO) application might delay intubation and increase mortality in acute hypoxemic respiratory failure (AHRF) patients. Intubation in coronavirus disease 2019 (COVID-19) AHRF (CAHRF) patients 24 to 48 hours after HFNO initiation has been associated with increased mortality in previous studies. This cut-off period is variable in previous studies. A time series analysis could reflect more robust data on outcome in relation to HFNO duration before intubation in CAHRF.

Methods

A retrospective study was conducted at 30-bedded ICU of a tertiary care teaching hospital from July 2020 to August 2021. The study cohort comprised 116 patients who required HFNO and were subsequently intubated following HFNO failure. A time series analysis of patient outcomes on each day of HFNO application prior to invasive mechanical ventilation (IMV) was done.

Results

ICU and hospital mortality was 67.2%. Beyond day 4 of HFNO application, there was a trend towards increased risk-adjusted ICU and hospital mortality for each day delay in intubation of CAHRF patients on HFNO [OR 2.718; 95% CI 0.957-7.721; P 0.061]. This trend was maintained till day 8 of HFNO application, after which there was 100% mortality. Taking day four as a cut-off in the timeline of HFNO application, we have observed an absolute mortality benefit of 15% with early intubation despite a higher APACHE-IV score than the late intubation group.

Conclusion

IMV beyond the 4^th day of HFNO initiation in CAHRF patients increases mortality.

Patient Self-Inflicted Lung Injury-A Narrative Review of Pathophysiology, Early Recognition, and Management Options

Patient self-inflicted lung injury (P-SILI) is a life-threatening condition arising from excessive respiratory effort and work of breathing in patients with lung injury. The pathophysiology of P-SILI involves factors related to the underlying lung pathology and vigorous respiratory effort. P-SILI might develop both during spontaneous breathing and mechanical ventilation with preserved spontaneous respiratory activity. In spontaneously breathing patients, clinical signs of increased work of breathing and scales developed for early detection of potentially harmful effort might help clinicians prevent unnecessary intubation, while, on the contrary, identifying patients who would benefit from early intubation. In mechanically ventilated patients, several simple non-invasive methods for assessing the inspiratory effort exerted by the respiratory muscles were correlated with respiratory muscle pressure. In patients with signs of injurious respiratory effort, therapy aimed to minimize this problem has been demonstrated to prevent aggravation of lung injury and, therefore, improve the outcome of such patients. In this narrative review, we accumulated the current information on pathophysiology and early detection of vigorous respiratory effort. In addition, we proposed a simple algorithm for prevention and treatment of P-SILI that is easily applicable in clinical practice.

Update on the management of acute respiratory failure using non-invasive ventilation and pulse oximetry

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2023. Other selected articles can be found online at  https://www.biomedcentral.com/collections/annualupdate2023 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from  https://link.springer.com/bookseries/8901 .

Effectiveness of high-flow nasal cannula therapy on clinical outcomes in adults with COVID-19: A systematic review

Introduction/Background

Coronavirus disease 2019 (COVID-19) has high transmissibility and mortality rates. High-flow nasal cannula therapy (HFNC) might reduce the need for orotracheal intubation, easing the burden on the health system caused by COVID-19. The objective of the present study was to examine the effectiveness of HFNC in adult patients hospitalized with COVID-19. Specifically, the present study explores the effects of HFNC on rates of mortality, intubation and intensive care units (ICU) length of stay. The present study also seeks to define predictors of success and failure of HFNC.

Methods

A systematic literature search was conducted in the PubMed, EMBASE and SCOPUS databases, and the study was prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Study quality was assessed using the National Heart, Lung, and Blood Institute's Study Quality Assessment Tools.

Results

The search identified 1,476 unique titles; 95 articles received full-text reviews and 40 studies were included in this review. HFNC was associated with a reduction in the rate of orotracheal intubation, notably when compared to conventional oxygen therapy. Studies reported inconsistency in whether HFNC reduced ICU length of stay or mortality rates. Among the predictors of HFNC failure/success, a ratio of oxygen saturation index of approximately 5 or more was associated with HFNC success.

Conclusion

In adult patients hospitalized with COVID-19, HFNC may prove effective in reducing the rate of orotracheal intubation. The ratio of the oxygen saturation index was the parameter most examined as a predictor of HFNC success. Low-level research designs, inherent study weaknesses and inconsistent findings made it impossible to conclude whether HFNC reduces ICU length of stay or mortality. Future studies should employ higher level research designs.

Choice of respiratory therapy for COVID-19 patients with acute hypoxemic respiratory failure: a retrospective case series study

Background

In the treatment of acute hypoxemic respiratory failure (AHRF) due to coronavirus 2019 (COVID-19), physicians choose respiratory management ranging from low-flow oxygen therapy to more invasive methods, depending on the severity of the patient's symptoms. Recently, the ratio of oxygen saturation (ROX) index has been proposed as a clinical indicator to support the decision for either high-flow nasal cannulation (HFNC) or mechanical ventilation (MV). However, the reported cut-off value of the ROX index ranges widely from 2.7 to 5.9. The objective of this study was to identify indices to achieve empirical physician decisions for MV initiation, providing insights to shorten the delay from HFNC to MV. We retrospectively analyzed the ROX index 6 hours after initiating HFNC and lung infiltration volume (LIV) calculated from chest computed tomography (CT) images in COVID-19 patients with AHRF.

Methods

We retrospectively analyzed the data for 59 COVID-19 patients with AHRF in our facility to determine the cut-off value of the ROX index for respiratory therapeutic decisions and the significance of radiological evaluation of pneumonia severity. The physicians chose either HFNC or MV, and the outcomes were retrospectively analyzed using the ROX index for initiating HFNC. LIV was calculated using chest CT images at admission.

Results

Among the 59 patients who required high-flow oxygen therapy with HFNC at admission, 24 were later transitioned to MV; the remaining 35 patients recovered. Four of the 24 patients in the MV group died, and the ROX index values of these patients were 9.8, 7.3, 5.4, and 3.0, respectively. These index values indicated that the ROX index of half of the patients who died was higher than the reported cut-off values of the ROX index, which range from 2.7-5.99. The cut-off value of the ROX index 6 hours after the start of HFNC, which was used to classify the management of HFNC or MV as a physician's clinical decision, was approximately 6.1. The LIV cut-off value on chest CT between HFNC and MV was 35.5%. Using both the ROX index and LIV, the cut-off classifying HFNC or MV was obtained using the equation, LIV = 4.26 × (ROX index) + 7.89. The area under the receiver operating characteristic curve, as an evaluation metric of the classification, improved to 0.94 with a sensitivity of 0.79 and specificity of 0.91 using both the ROX index and LIV.

Conclusion

Physicians' empirical decisions associated with the choice of respiratory therapy for HFNC oxygen therapy or MV can be supported by the combination of the ROX index and the LIV index calculated from chest CT images.

Prediction of noninvasive ventilation failure using the ROX index in patients with de novo acute respiratory failure

BACKGROUND

The ratio of SpO₂/FiO₂ to respiratory rate (ROX) index is commonly used to predict the failure of high-flow nasal cannula. However, its predictive power for noninvasive ventilation (NIV) failure is unclear.

METHODS

This was a secondary analysis of a multicenter prospective observational study, intended to update risk scoring. Patients with de novo acute respiratory failure were enrolled, but hypercapnic patients were excluded. The ROX index was calculated before treatment and after 1-2, 12, and 24 h NIV. Differences in predictive power for NIV failure using the ROX index, PaO₂/FiO₂, and PaO₂/FiO₂/respiratory rate were tested.

RESULTS

A total of 1286 patients with de novo acute respiratory failure were enrolled. Of these, 568 (44%) experienced NIV failure. Patients with NIV failure had a lower ROX index than those with NIV success. The rates of NIV failure were 92.3%, 70.5%, 55.3%, 41.1%, 35.1%, and 29.5% in patients with ROX index values calculated before NIV of ≤ 2, 2-4, 4-6, 6-8, 8-10, and > 10, respectively. Similar results were found when the ROX index was assessed after 1-2, 12, and 24 h NIV. The area under the receiver operating characteristics curve was 0.64 (95% CI 0.61-0.67) when the ROX index was used to predict NIV failure before NIV. It increased to 0.71 (95% CI 0.68-0.74), 0.74 (0.71-0.77), and 0.77 (0.74-0.80) after 1-2, 12, and 24 h NIV, respectively. The predictive power for NIV failure was similar for the ROX index and for the PaO₂/FiO₂. Likewise, no difference was found between the ROX index and the PaO₂/FiO₂/respiratory rate, except at the time point of 1-2 h NIV.

CONCLUSIONS

The ROX index has moderate predictive power for NIV failure in patients with de novo acute respiratory failure.

The Relationship of Respiratory Rate-Oxygenation (ROX) and Modified ROX Index With High-Flow Nasal Cannula Oxygen Therapy in COVID-19 Patients: An Observational Pilot Study

Background and aim Respiratory Rate-Oxygenation (ROX) and modified ROX (mROX) indexes have been proposed to detect early high-flow nasal cannula (HFNC) therapy failure. We evaluated the utility and relationship of ROX and mROX indexes in COVID-19 patients started on HFNC oxygen therapy. Methods This pilot study collected data from adult COVID-19 patients requiring HFNC oxygenation from 29 Jan - 29 Jun 2021. The patients were divided into two cohorts based on HFNC therapy success. ROX and mROX were compared using statistical diagnostic testing, including receiver operating characteristics and area under the curve (AUC) using online Epitools (https://epitools.ausvet.com.au/) and MedCalc software (MedCalc Software Ltd, Ostend, Belgium, https://www.medcalc.org/); p<0.05 was considered significant. Results Twenty-seven patients fulfilled the inclusion criteria; 48.15% of therapy failed. The cohort's mean ± standard deviation age was 53.93 ± 10.67 years; 74.1% were male. The accuracy of predicting failure for mean ROX versus mROX at baseline and six-hour values was 59.81 versus 70.68 and 67.42 versus 74.88, respectively (all p>0.05). The AUC for ROX and mROX at baseline and at six hours were statistically indifferent. Only an mROX of 4.05 (mean value) and 3.34 (Youden's J cut-off) had a sensitivity plus specificity at 156% and 163%, respectively. Conclusion Both ROX and mROX at baseline and six hours had fair-to-good accuracies and AUC; the differences were insignificant. Both ROX and mROX had better accuracies at six hours. However, only mROX < 4.05 at six hours fulfilled the sensitivity plus specificity criteria to be a clinically valuable screener.