High-Flow Nasal Cannula Therapy for Acute Hypoxemic Respiratory Failure in Adults: A Retrospective Analysis

ROX index versus HACOR scale in predicting success and failure of high-flow nasal cannula in the emergency department for patients with acute hypoxemic respiratory failure: a prospective observational study

BACKGROUND

High-flow nasal cannula has been a promising initial respiratory support measure for patients with acute hypoxemic respiratory failure (AHRF) in the emergency department (ED). However, delayed detection of HFNC failure is associated with increased mortality. The ROX index is a tool that can help predict HFNC success. Nonetheless, its utility in ED patients is limited, and no studies have compared it with the HACOR scale, another tool that may be as accurate in predicting HFNC failure. Therefore, we aimed to compare the prognostic utility of the ROX index and the HACOR scale in emergency AHRF patients.

METHODS

This prospective observational study was conducted at the ED of Siriraj Hospital, Thailand, between August 2018 and February 2020. Adult patients with AHRF requiring HFNC in the ED were included. The ROX index and the HACOR scale were measured at 1, 2, and 6 h after HFNC initiation. The primary outcome was HFNC success, defined as no intolerance or escalation towards mechanical ventilation or non-invasive ventilation within 48 h.

RESULTS

A total of 75 patients were enrolled; 52 (69.3%) had a successful treatment. The ROX index was higher in the success group, while the HACOR scale was lower at all timepoints. The ROX index yielded generally higher discrimination capacity based on the area under the receiver operating characteristic curve (AUROC) than the HACOR scale [AUROC at 1, 2, and 6 h = 0.815, 0.784, 0.853 for ROX in predicting HFNC success and 0.733, 0.690, and 0.764 for HACOR in predicting HFNC failure]. The ROX index measured at 6 h at the cut-point of 4.88 had 92.98% sensitivity, 61.11% specificity, 88.33% positive predictive value, and 73.33% negative predictive value with a diagnostic accuracy of 85.33%.

CONCLUSION

The ROX index had superior prognostic utility in predicting HFNC outcome (success/failure) compared to the HACOR scale in patients with AHRF in the ED setting. Moreover, it is less complex and more efficient to be employed at bedside. Therefore, the ROX index is a more appropriate tool to guide further management and potential escalation therapy for AHRF patients with HFNC therapy initiated in the ED.

Expanding the utility of the ROX index among patients with acute hypoxemic respiratory failure

BACKGROUND

Delaying intubation in patients who fail high-flow nasal cannula (HFNC) may result in increased mortality. The ROX index has been validated to predict HFNC failure among pneumonia patients with acute hypoxemic respiratory failure (AHRF), but little information is available for non-pneumonia causes. In this study, we validate the ROX index among AHRF patients due to both pneumonia or non-pneumonia causes, focusing on early prediction.

METHODS

This was a retrospective observational study in eight Singapore intensive care units from 1 January 2015 to 30 September 2017. All patients >18 years who were treated with HFNC for AHRF were eligible and recruited. Clinical parameters and arterial blood gas values at HFNC initiation and one hour were recorded. HFNC failure was defined as requiring intubation post-HFNC initiation.

RESULTS

HFNC was used in 483 patients with 185 (38.3%) failing HFNC. Among pneumonia patients, the ROX index was most discriminatory in pneumonia patients one hour after HFNC initiation [AUC 0.71 (95% CI 0.64-0.79)], with a threshold value of <6.06 at one hour predicting HFNC failure (sensitivity 51%, specificity 80%, positive predictive value 61%, negative predictive value 73%). The discriminatory power remained moderate among pneumonia patients upon HFNC initiation [AUC 0.65 (95% CI 0.57-0.72)], non-pneumonia patients at HFNC initiation [AUC 0.62 (95% CI 0.55-0.69)] and one hour later [AUC 0.63 (95% CI 0.56-0.70)].

CONCLUSION

The ROX index demonstrated moderate discriminatory power among patients with either pneumonia or non-pneumonia-related AHRF at HFNC initiation and one hour later.

A Review of High Flow Nasal Cannula Oxygen Therapy in Human and Veterinary Medicine

Respiratory distress is a common ailment in small animal medicine. Oxygen supplementation is a mainstay of initial therapy. High Flow Nasal Cannula Oxygen Therapy (HFNCOT) has become increasingly popular as a treatment modality in human medicine, and more recently in canine patients. These devices deliver high flow rates of heated and humidified oxygen at an adjustable fraction of inspired oxygen (FiO₂). This article reviews current literature in human patients on HFNCOT as well as studies that have evaluated its use in veterinary patients. A discussion of the respiratory physiology that is associated with respiratory distress, in addition to an overview of currently available oxygen supplementation modalities is provided. The physiologic benefits of HFNCOT are explained, as are technical aspects associated with its use. Recommendations on initial settings, maintenance therapy, and weaning are also described.

High-flow nasal cannula oxygen therapy in acute hypoxemic respiratory failure in 22 dogs requiring oxygen support escalation

OBJECTIVE

To determine the effect of high-flow nasal cannula (HFNC) oxygen therapy on cardiorespiratory variables and outcome in dogs with acute hypoxemic respiratory failure.

DESIGN

Prospective, sequential clinical trial.

SETTING

University veterinary teaching hospital.

ANIMALS

Twenty-two client-owned dogs that failed to respond to traditional oxygen support.

INTERVENTIONS

Initiation of HFNC therapy after traditional oxygen supplementation failed to increase Spo₂ > 96% and Pao₂ > 75 mm Hg or improve respiratory rate/effort.

MEASUREMENTS AND MAIN RESULTS

Physiological variables, blood gas analyses, and dyspnea/sedation/tolerance scores were collected prior to HFNC initiation (on traditional oxygen support [time 0 or T0]), and subsequently during HFNC oxygen administration at time 30 minutes, 60 minutes, and 7 ± 1 hours. Relative to T0, use of HFNC resulted in a decreased respiratory rate at 1 hour (P = 0.022) and 7 hours (P = 0.012), a decrease in dyspnea score at all times (P < 0.01), and an increase in Spo₂ at all times (P < 0.01). There was no difference in arterial/venous Pco₂ relative to T0, although Paco₂ was correlated with flow rate. Based on respiratory assessment, 60% of dogs responded to HFNC use by 30 minutes, and 45% ultimately responded to HFNC use and survived. No clinical air-leak syndromes were observed.

CONCLUSIONS

HFNC use improved oxygenation and work of breathing relative to traditional oxygen therapies, without impairing ventilation. HFNC use appears to be a beneficial oxygen support modality to bridge the gap between standard oxygen supplementation and mechanical ventilation.

An Index Combining Respiratory Rate and Oxygenation to Predict Outcome of Nasal High-Flow Therapy

Rationale: One important concern during high-flow nasal cannula (HFNC) therapy in patients with acute hypoxemic respiratory failure is to not delay intubation. Objectives: To validate the diagnostic accuracy of an index (termed ROX and defined as the ratio of oxygen saturation as measured by pulse oximetry/Fi_O2 to respiratory rate) for determining HFNC outcome (need or not for intubation). Methods: This was a 2-year multicenter prospective observational cohort study including patients with pneumonia treated with HFNC. Identification was through Cox proportional hazards modeling of ROX association with HFNC outcome. The most specific cutoff of the ROX index to predict HFNC failure and success was assessed. Measurements and Main Results: Among the 191 patients treated with HFNC in the validation cohort, 68 (35.6%) required intubation. The prediction accuracy of the ROX index increased over time (area under the receiver operating characteristic curve: 2 h, 0.679; 6 h, 0.703; 12 h, 0.759). ROX greater than or equal to 4.88 measured at 2 (hazard ratio, 0.434; 95% confidence interval, 0.264-0.715; P = 0.001), 6 (hazard ratio, 0.304; 95% confidence interval, 0.182-0.509; P < 0.001), or 12 hours (hazard ratio, 0.291; 95% confidence interval, 0.161-0.524; P < 0.001) after HFNC initiation was consistently associated with a lower risk for intubation. A ROX less than 2.85, less than 3.47, and less than 3.85 at 2, 6, and 12 hours of HFNC initiation, respectively, were predictors of HFNC failure. Patients who failed presented a lower increase in the values of the ROX index over the 12 hours. Among components of the index, oxygen saturation as measured by pulse oximetry/Fi_O2 had a greater weight than respiratory rate. Conclusions: In patients with pneumonia with acute respiratory failure treated with HFNC, ROX is an index that can help identify those patients with low and those with high risk for intubation. Clinical trial registered with www.clinicaltrials.gov (NCT02845128).

Noninvasive approach for de novo acute hypoxemic respiratory failure: noninvasive ventilation, high-flow nasal cannula, both or none?

PURPOSE OF REVIEW

To summarize the recent evidence regarding the use of noninvasive strategies for de novo acute hypoxemic respiratory failure (AHRF).

RECENT FINDINGS

New guidelines for the use of noninvasive ventilation (NIV) in acute respiratory failure have been published. In parallel, high-flow nasal cannula (HFNC) is an emerging noninvasive strategy for AHRF patients. Although some have cautioned against the use of NIV in AHRF, new encouraging data about the use of a helmet interface for NIV in acute respiratory distress syndrome may overcome the limitations of facemask NIV.

SUMMARY

In the last two decades, the use of NIV and HFNC in patients with AHRF has considerably expanded, changing the paradigm of management of AHRF. Choice of each technique should be based according to centre experience and patient tolerability. However, when using noninvasive strategies for AHRF, it is crucial to predefine specific criteria for intubation and monitor patients closely for early detection of clinical deterioration to avoid delayed intubation.

Clinical efficacy of high-flow oxygen therapy through nasal cannula in patients with acute heart failure

Background

High-flow oxygen therapy through nasal cannula (HFNC) could reduce intubation rate and mortality rate among patients with acute respiratory failure. We evaluated the physiological responses and clinical outcomes of HFNC in patients with acute heart failure (AHF).

Methods

A retrospective cohort analysis was performed in single medical tertiary center. Patients with AHF who had a progressive hypoxemia after oxygenation via facemask were divided into intubation group and HFNC group. We analyzed the physiological responses and in-hospital clinical outcomes between two groups.

Results

Seventy-three patients of intubation group and 76 patients of HFNC group were included. Baseline characteristics were well-balanced between two groups. There were no differences in changes of mean arterial pressure, heart rate, and pulse oxygen saturation during the first 6 hours. Among HFNC group, 66 of 76 patients (86.8%) were successfully recovered from progressive hypoxemia without endotracheal intubation, and there were no differences in in-hospital clinical outcomes between two groups.

Conclusions

This study showed HFNC group had a similar result of improvement of oxygen saturation and in-hospital clinical outcomes compared with intubation group in AHF. Present study supported HFNC could be considered as initial choice of oxygen therapy in selected patients of AHF.

Improved oxygenation 48 hours after high-flow nasal cannula oxygen therapy is associated with good outcome in immunocompromised patients with acute respiratory failure

Background

Respiratory failure requiring intubation is a risk factor for mortality in immunocompromised patients, therefore, noninvasive methods to avoid intubation are preferred in such patients. A high-flow nasal cannula (HFNC) is an alternative noninvasive technique for oxygen delivery but can be potentially harmful in cases of delayed intubation. We sought to identify the physiological predictors of outcome to assess the responsiveness to HFNC of immunocompromised patients with acute respiratory failure.

Methods

We retrospectively analyzed the medical records of immunocompromised patients treated with HFNC in 2015 and 2016 in a tertiary hospital. Oxygenation was assessed by calculating the SpO₂/FiO₂ (SF) ratio. Subjects were defined as "SF-improved" when HFNC resulted in an increase in the SF ratio compared with baseline. The values were collected at baseline, 12, 24, and 48 h.

Results

Ninety-one patients with a median age of 64 years were analyzed; 68.1% were men. There was no significant difference between the SF₄₈-improved and the SF₄₈-nonimproved groups in clinical baseline characteristics or severity of illness as evaluated at the time of initiation of HFNC by APACHE II, SAPS II, and SOFA. The 28-day mortality was significantly lower in the SF₄₈-improved compared with the SF₄₈-nonimproved group. In univariate analysis, mortality was significantly associated with body mass index (BMI), poor functional status, do-not-intubate (DNI) status, the "SF₄₈-improved" group, the reason for immunocompromise, and the severity of illness at the time of initiation of HFNC. In multivariate analysis, "SF₄₈-improved" group was not significantly associated with increased mortality [odds ratio (OR) 0.462; 95% confidence interval (CI), 0.107-1.988; P=0.299].

Conclusions

In immunocompromised patients with acute respiratory failure, an improved SF ratio 48 h after HFNC treatment was associated with improved 28-day mortality.

High-flow nasal cannula therapy for adult patients

High-flow nasal cannula (HFNC) oxygen therapy has several physiological advantages over traditional oxygen therapy devices, including decreased nasopharyngeal resistance, washing out of the nasopharyngeal dead space, generation of positive pressure in the pharynx, increasing alveolar recruitment in the lungs, humidification of the airways, increased fraction of inspired oxygen and improved mucociliary clearance. Recently, the use of HFNC in treating adult critical illness patients has significantly increased, and it is now being used in many patients with a range of different disease conditions. However, there are no established guidelines to direct the safe and effective use of HFNC for these patients. This review article summarizes the available published literature on the positive physiological effects, mechanisms of action, and the clinical applications of HFNC, compared with traditional oxygen therapy devices. The available literature suggests that HFNC oxygen therapy is an effective modality for the early treatment of critically adult patients.

Applications of Nasal High-Flow Oxygen Therapy in Critically ill Adult Patients

The use of nasal high-flow oxygen therapy (NHFOT) has become increasingly common in hospitals across Europe, Asia, and North America. These high utility devices provide an efficient and comfortable access points for providing supplemental oxygen to patients with variety of respiratory disorders. They are relatively easy to set up, and clinicians and patients alike give very positive feedback about their ease of use and comfort for patients in the hospital setting. However, it remains uncertain whether NHFOT improves patient survival or even reduces respiratory complications. Outcome data in adult populations are few and frequently underpowered to guide physicians for their widespread use in hospital setting. In this article, we present a review of the current technology and available studies pertinent to NHFOT.

Current evidence for the effectiveness of heated and humidified high flow nasal cannula supportive therapy in adult patients with respiratory failure

High flow nasal cannula (HFNC) supportive therapy has emerged as a safe, useful therapy in patients with respiratory failure, improving oxygenation and comfort. Recently several clinical trials have analyzed the effectiveness of HFNC therapy in different clinical situations and have reported promising results. Here we review the current knowledge about HFNC therapy, from its mechanisms of action to its effects on outcomes in different clinical situations.