Diagnosis and Epidemiology of Acute Respiratory Failure

Acute respiratory failure is a common clinical finding caused by insufficient oxygenation (hypoxemia) or ventilation (hypocapnia). Understanding the pathophysiology of acute respiratory failure can help to facilitate recognition, diagnosis, and treatment. The cause of acute respiratory failure can be identified through utilization of physical examination findings, laboratory analysis, and chest imaging.

Switches in non-invasive respiratory support strategies during acute hypoxemic respiratory failure: Need to monitoring from a retrospective observational study

OBJECTIVE

To explore combined non-invasive-respiratory-support (NIRS) patterns, reasons for NIRS switching, and their potential impact on clinical outcomes in acute-hypoxemic-respiratory-failure (AHRF) patients.

DESIGN

Retrospective, single-center observational study.

SETTING

Intensive Care Medicine.

PATIENTS

AHRF patients (cardiac origin and respiratory acidosis excluded) underwent combined NIRS therapies such as non-invasive-ventilation (NIV) and High-Flow-Nasal-Cannula (HFNC).

INTERVENTIONS

Patients were classified based on the first NIRS switch performed (HFNC-to-NIV or NIV-to-HFNC), and further specific NIRS switching strategies (NIV trial-like vs. Non-NIV trial-like and single vs. multiples switches) were independently evaluated.

MAIN VARIABLES OF INTEREST

Reasons for switching, NIRS failure and mortality rates.

RESULTS

A total of 63 patients with AHRF were included, receiving combined NIRS, 58.7% classified in the HFNC-to-NIV group and 41.3% in the NIV-to-HFNC group. Reason for switching from HFNC to NIV was AHRF worsening (100%), while from NIV to HFNC was respiratory improvement (76.9%). NIRS failure rates were higher in the HFNC-to-NIV than in NIV-to-HFNC group (81% vs. 35%, p < 0.001). Among HFNC-to-NIV patients, there was no difference in the failure rate between the NIV trial-like and non-NIV trial-like groups (86% vs. 78%, p = 0.575) but the mortality rate was significantly lower in NIV trial-like group (14% vs. 52%, p = 0.02). Among NIV to HFNC patients, NIV failure was lower in the single switch group compared to the multiple switches group (15% vs. 53%, p = 0.039), with a shorter length of stay (5 [2-8] vs. 12 [8-30] days, p = 0.001).

CONCLUSIONS

NIRS combination is used in real life and both switches' strategies, HFNC to NIV and NIV to HFNC, are common in AHRF management. Transitioning from HFNC to NIV is suggested as a therapeutic escalation and in this context performance of a NIV-trial could be beneficial. Conversely, switching from NIV to HFNC is suggested as a de-escalation strategy that is deemed safe if there is no NIRS failure.

Optimal timing for awake prone positioning in Covid-19 patients: Insights from an observational study from two centers

BACKGROUND

The widespread application and interest in awake prone positioning stems from its ease and availability and its ability to enhance patients' oxygenation. Nevertheless, due to the absence of consensus over the regimen of awake prone positioning, the efficacy of awake prone positioning remains uncertain.

OBJECTIVE

To explore the optimal regimen for awake prone positioning, including the timing of initiation, ideal daily duration, and strategies for improving patient comfort and encouraging adherence.

DESIGN

Retrospective observational study.

SETTING(S)

Two university-affiliated hospitals in Shanghai.

PARTICIPANTS

Between December 2022 and February 2023, a total of 475 patients with COVID-19-related pneumonia who received awake prone positioning were observed.

METHODS

The data were collected from the hospital's electronic medical record system. The differentiation efficiency of peripheral blood oxygen saturation [SpO2]:fractional oxygen concentration in inspired air [FiO2] ratio at first awake prone positioning for different outcomes was tested by the area under the receiver operating characteristic curve. The Cox proportional hazard regression model was used to analyze the relationship between time to occurrence of 28-day outcomes and collected variables. Kaplan-Meier curves were plotted with the percentage of 28-day outcomes according to the SpO2:FiO2 ratio at first awake prone positioning after controlling covariates through Cox regression.

RESULTS

The best efficiency in predicting patient outcomes was achieved when the cutoff SpO2:FiO2 ratio at first awake prone positioning was 200. Patients with a reduced SpO2:FiO2 ratio (≤200) experienced more adverse respiratory outcomes (RR = 5.42, 95%CI [3.35, 8.76], p < 0·001) and higher mortality (RR = 16.64, 95%CI [5.53, 50.13], p < 0.001). Patients with a SpO2:FiO2 ratio of ≥200 at first awake prone positioning, longer duration between first awake prone positioning and admission, more awake prone positioning days, and better awake prone positioning completion were significantly protected from 28-day adverse respiratory outcomes and mortality.

CONCLUSIONS

Initiating awake prone positioning with a SpO2:FiO2 ratio exceeding 200, increasing the number of awake prone positioning days, prolonging the time between first awake prone positioning and admission, and achieving better completion of awake prone positioning were found to be significantly associated with reduced adverse respiratory outcomes and mortality.

REGISTRATION

ClinicalTrials.gov; No.: NCT05795751; URL: www.

CLINICALTRIALS

gov.

Association between the ROX index and mortality in patients with acute hypoxemic respiratory failure: a retrospective cohort study

BACKGROUND

Although ROX index is frequently used to assess the efficacy of high-flow nasal cannula treatment in acute hypoxemic respiratory failure (AHRF) patients, the relationship between the ROX index and the mortality remains unclear. Therefore, a retrospective cohort study was conducted to evaluate the ability of the ROX index to predict mortality risk in patients with AHRF.

METHOD

Patients diagnosed with AHRF were extracted from the MIMIC-IV database and divided into four groups based on the ROX index quartiles. The primary outcome was 28-day mortality, while in-hospital mortality and follow-up mortality were secondary outcomes. To investigate the association between ROX index and mortality in AHRF patients, restricted cubic spline curve and COX proportional risk regression were utilized.

RESULT

A non-linear association (L-shaped) has been observed between the ROX index and mortality rate. When the ROX index is below 8.28, there is a notable decline in the 28-day mortality risk of patients as the ROX index increases (HR per SD, 0.858 [95%CI 0.794-0.928] P < 0.001). When the ROX index is above 8.28, no significant association was found between the ROX index and 28-day mortality. In contrast to the Q1 group, the mortality rates in the Q2, Q3, and Q4 groups had a substantial reduction (Q1 vs. Q2: HR, 0.749 [0.590-0.950] P = 0.017; Q3: HR, 0.711 [0.558-0.906] P = 0.006; Q4: HR, 0.641 [0.495-0.830] P < 0.001).

CONCLUSION

The ROX index serves as a valuable predictor of mortality risk in adult patients with AHRF, and that a lower ROX index is substantially associated with an increase in mortality.

Immunomodulators for immunocompromised patients hospitalized for COVID-19: a meta-analysis of randomized controlled trials

Background

Although immunomodulators have established benefit against the new coronavirus disease (COVID-19) in general, it is uncertain whether such agents improve outcomes without increasing the risk of secondary infections in the specific subgroup of previously immunocompromised patients. We assessed the effect of immunomodulators on outcomes of immunocompromised patients hospitalized for COVID-19.

Methods

The protocol was prospectively registered with PROSPERO (CRD42022335397). MEDLINE, Cochrane Central Register of Controlled Trials and references of relevant articles were searched up to 01-06-2022. Authors of potentially eligible randomized controlled trials were contacted to provide data on immunocompromised patients randomized to immunomodulators vs control (i.e., placebo or standard-of-care).

Findings

Eleven randomized controlled trials involving 397 immunocompromised patients hospitalized for COVID-19 were included. Ten trials had low risk of bias. There was no difference between immunocompromised patients randomized to immunomodulators vs control regarding mortality [30/182 (16.5%) vs 41/215 (19.1%); RR 0.93, 95% CI 0.61-1.41; p = 0.74], secondary infections (RR 1.00, 95% CI 0.64-1.58; p = 0.99) and change in World Health Organization ordinal scale from baseline to day 15 (weighed mean difference 0.27, 95% CI -0.09-0.63; p = 0.15). In subgroup analyses including only patients with hematologic malignancy, only trials with low risk of bias, only trials administering IL-6 inhibitors, or only trials administering immunosuppressants, there was no difference between comparators regarding mortality.

Interpretation

Immunomodulators, compared to control, were not associated with harmful or beneficial outcomes, including mortality, secondary infections, and change in ordinal scale, when administered to immunocompromised patients hospitalized for COVID-19.

Funding

Hellenic Foundation for Research and Innovation.

A Prospective Observational Study Comparing Oxygen Saturation/Fraction of Inspired Oxygen Ratio with Partial Pressure of Oxygen in Arterial Blood/Fraction of Inspired Oxygen Ratio among Critically Ill Patients Requiring Different Modes of Oxygen Supplementation in Intensive Care Unit

Background

Intensive care unit (ICU) patients face a significant rise in mortality rates due to acute hypoxemic respiratory failure (AHRF). The diagnosis of AHRF is based on the PF ratio, but it has limitations in resource-constrained settings. Instead, the Kigali modification suggests using the oxygen saturation/fraction of inspired oxygen (SF) ratio. This study aims to correlate SF ratio and arterial oxygen pressure (PF) ratio in critically ill adults with hypoxemic respiratory failure, who required O2 therapy through different modes of oxygen supplementation.

Materials and methods

In an ICU, a prospective observational study included 125 adult AHRF patients receiving oxygen therapy, with data collected on FiO2, PaO2, and SpO2. The SF ratio and PF ratio were calculated, and their correlation was assessed using statistical analysis. The receiver operator characteristics (ROC) curve analysis was conducted to assess the diagnostic precision of the SF ratio in identifying AHRF.

Results

Data from a total of 250 samples were collected. The study showed a positive correlation (r = 0.622) between the SF ratio and the PF ratio. The SF threshold values of 252 and 321 were established for PF values of 200 and 300, respectively, featuring a sensitivity of 69% and specificity of 95%. Furthermore, it is worth noting that the PF ratio and SF ratio are interchangeable, regardless of the type of oxygen therapy, as the median values of both the PF ratio and SF ratio displayed statistical significance (p < 0.01) in both acidosis and alkalosis conditions.

Conclusion

For patients with AHRF, the noninvasive SF ratio can effectively serve as a substitute for the invasive PF ratio across all oxygen supplementation modes.

How to cite this article

Alur TR, Iyer SS, Shah JN, Kulkarni S, Jedge P, Patil V. A Prospective Observational Study Comparing Oxygen Saturation/Fraction of Inspired Oxygen Ratio with Partial Pressure of Oxygen in Arterial Blood/Fraction of Inspired Oxygen Ratio among Critically Ill Patients Requiring Different Modes of Oxygen Supplementation in Intensive Care Unit. Indian J Crit Care Med 2024; 28(3):251-255.

Effectiveness and safety of awake prone positioning in COVID-19-related acute hypoxaemic respiratory failure: an overview of systematic reviews

OBJECTIVE

To evaluate and summarize systematic reviews of the effects and safety of awake prone positioning for COVID-19-related acute hypoxaemic respiratory failure.

METHODS

A comprehensive search was conducted on PubMed, Embase, the Cochrane Library, Web of Science, CNKI, CSPD, CCD and CBM from their inception to March 28, 2023. Systematic reviews (SRs) of awake prone positioning (APP) for COVID-19-related acute hypoxaemic respiratory failure in adults were included. Two reviewers screened the eligible articles, and four reviewers in pairs extracted data and assessed the methodological quality/certainty of the evidence of all included SRs by AMSTAR 2 and GRADE tools. The overlap of primary studies was measured by calculating corrected covered areas. Data from the included reviews were synthesized with a narrative description.

RESULTS

A total of 11 SRs were included. The methodological quality of SRs included 1 "High", 4 "Moderate", 2 "Low" and 4 "Critically low" by AMSTAR 2. With the GRADE system, no high-quality evidence was found, and only 14 outcomes provided moderate-quality evidence. Data synthesis of the included SR outcomes showed that APP reduced the risk of requiring intubation (11 SRs) and improving oxygenation (3 SRs), whereas reduced significant mortality was not found in RCT-based SRs. No significant difference was observed in the incidence of adverse events between groups (8 SRs). The corrected covered area index was 27%, which shows very high overlap among studies.

CONCLUSION

The available SRs suggest that APP has benefits in terms of reducing intubation rates and improving oxygenation for COVID-19-related acute hypoxemic respiratory failure, without an increased risk of adverse events. The conclusion should be treated with caution because of the generally low quality of methodology and evidence.

TRIAL REGISTRATION

The protocol for this review was registered with PROSPERO: CRD42023400986. Registered 15 April 2023.

Respiratory rate‑oxygenation (ROX) index for predicting high-flow nasal cannula failure in patients with and without COVID-19

BACKGROUND

The predictive value of the respiratory rate‑oxygenation (ROX) index for a high-flow nasal cannula (HFNC) in patients with COVID-19 with acute hypoxemic respiratory failure (AHRF) may differ from patients without COVID-19 with AHRF, but these patients have not yet been compared. We compared the diagnostic accuracy of the ROX index for HFNC failure in patients with AHRF with and without COVID-19 during acute emergency department (ED) visits.

METHODS

We performed a retrospective analysis of patients with AHRF treated with an HFNC in an ED between October 2020 and April 2022. The ROX index was calculated at 1, 2, 4, 6, 12, and 24 h after HFNC placement. The primary outcome was the failure of the HFNC, which was defined as the need for subsequent intubation or death within 72 h. A receiver operating characteristic (ROC) curve was used to evaluate discriminative power of the ROX index for HFNC failure.

RESULTS

Among 448 patients with AHRF treated with an HFNC in an ED, 78 (17.4%) patients were confirmed to have COVID-19. There was no significant difference in the HFNC failure rates between the non-COVID-19 and COVID-19 groups (29.5% vs. 33.3%, p = 0.498). The median ROX index was higher in the non-COVID-19 group than in the COVID-19 group at all time points. The prognostic power of the ROX index for HFNC failure as evaluated by the area under the ROC curve was generally higher in the COVID-19 group (0.73-0.83) than the non-COVID-19 group (0.62-0.75). The timing of the highest prognostic value of the ROX index for HFNC failure was at 4 h for the non-COVID-19 group, whereas in the COVID-19 group, its performance remained consistent from 1 h to 6 h. The optimal cutoff values were 6.48 and 5.79 for the non-COVID-19 and COVID-19 groups, respectively.

CONCLUSIONS

The ROX index had an acceptable discriminative power for predicting HFNC failure in patients with AHRF with and without COVID-19 in the ED. However, the higher ROX index thresholds than those in previous publications involving intensive care unit (ICU) patients suggest the need for careful monitoring and establishment of a new threshold for patients admitted outside the ICU.

Associations of Awake Prone Positioning-Induced Changes in Physiology with Intubation: An International Prospective Observational Study in Patients with Acute Hypoxemic Respiratory Failure Related to COVID-19

INTRODUCTION

Awake prone positioning has the potential to improve oxygenation and decrease respiratory rate, potentially reducing the need for intubation in patients with acute hypoxemic respiratory failure. We investigated awake prone positioning-induced changes in oxygenation and respiratory rate, and the prognostic capacity for intubation in patients with COVID-19 pneumonia.

METHODS

International multicenter prospective observation study in critically ill adult patients with COVID-19 receiving supplemental oxygen. We collected data on oxygenation and respiratory rate at baseline, and at 1 h after being placed in prone positioning. The combined primary outcome was oxygenation and respiratory rate at 1 h. The secondary endpoint was treatment failure, defined as need for intubation within 24 h of start of awake prone positioning.

RESULTS

Between March 27th and November 2020, 101 patients were enrolled of which 99 were fully analyzable. Awake prone positioning lasted mean of 3 [2-4] h. In 77 patients (77.7%), awake prone positioning improved oxygenation, and in 37 patients (54.4%) it decreased respiratory rate. Twenty-nine patients (29.3%) were intubated within 24 h. An increase in SpO2/FiO2 of < 10 (OR 5.1, 95% CI 1.4-18.5, P = 0.01), a failure to increase PaO2/FiO2 to > 116 mmHg (OR 3.6, 95% CI 1.2-10.8, P = 0.02), and a decrease in respiratory rate of < 2 breaths/min (OR 3.6, 95% CI 1.3-9.5, P = 0.01) were independent variables associated with need for intubation. The AUC-ROC curve for intubation using a multivariable model was 0.73 (95% CI 0.62-0.84).

CONCLUSIONS

Awake prone positioning improves oxygenation in the majority of patients, and decreases respiratory rate in more than half of patients with acute hypoxemic respiratory failure caused by COVID-19. One in three patients need intubation within 24 h. Awake prone position-induced changes in oxygenation and respiratory rate have prognostic capacity for intubation within 24 h.

Racial and ethnic minority participants in clinical trials of acute respiratory distress syndrome

PURPOSE

There is growing interest in improving the inclusiveness of racial and ethnic minority participants in trials of acute respiratory distress syndrome (ARDS). With our study we aimed to examine temporal trends of representation and mortality of racial and ethnic minority participants in randomized controlled trials of ARDS.

METHODS

We performed a secondary analysis of eight ARDS Network and PETAL Network therapeutic clinical trials, published between 2000 and 2019. We classified race/ethnicity into "White", "Black", "Hispanic", or "Other" (including Asian, American Indian or Alaskan Native, Native Hawaiian, or other Pacific Islander participants).

RESULTS

Of 5375 participants with ARDS, 1634 (30.4%) were Black, Hispanic, or Other race participants. Representation of racial and ethnic minority participants in trials did not change significantly over time (p = 0.257). However, among participants with moderate to severe ARDS (i.e., partial pressure of arterial oxygen to fraction of inspired oxygen ratio < 150), the difference in mortality between racial and ethnic minority participants and White participants decreased over time. In the five most recent trials, including 2923 participants with ARDS, there were no statistically significant differences in mortality between racial/ethnic groups, even after adjusting for potential confounders. In these five most recent trials, mortality was 31% for White, 31.9% for Black, 30.3% for Hispanic, and 37.1% for Other race participants (p = 0.633).

CONCLUSION

Representation of racial and ethnic minority participants in ARDS trials from North America, published between 2000 and 2019, did not change over time. Black and Hispanic participants with ARDS may have similar mortality as White participants within trials.

A technique to measure tidal volume during noninvasive respiratory support by continuous-flow helmet CPAP

PURPOSE

The coronavirus disease 2019 (COVID-19) pandemic has promoted the use of helmet continuous positive airway pressure (CPAP) for noninvasive respiratory support in hypoxic respiratory failure patients, despite the lack of tidal volume monitoring. We evaluated a novel technique designed to measure tidal volume during noninvasive continuous-flow helmet CPAP.

METHODS

A bench model of spontaneously breathing patients undergoing helmet CPAP therapy (three positive end-expiratory pressure [PEEP] levels) at different levels of respiratory distress was used to compare measured and reference tidal volumes. Tidal volume measurement by the novel technique was based on helmet outflow-trace analysis. Helmet inflow was increased from 60 to 75 and 90 L/min to match the patient's peak inspiratory flow; an additional subset of tests was conducted under the condition of purposely insufficient inflow (i.e., high respiratory distress and 60 L/min inflow).

RESULTS

The tidal volumes examined herein ranged from 250 to 910 mL. The Bland‒Altman analysis showed a bias of -3.2 ± 29.3 mL for measured tidal volumes compared to the reference, corresponding to an average relative error of -1 ± 4.4%. Tidal volume underestimation correlated with respiratory rate (rho = .411, p = .004) but not with peak inspiratory flow, distress, or PEEP. When the helmet inflow was maintained purposely low, tidal volume underestimation occurred (bias - 93.3 ± 83.9 mL), corresponding to an error of -14.8 ± 6.3%.

CONCLUSION

Tidal volume measurement is feasible and accurate during bench continuous-flow helmet CPAP therapy by the analysis of the outflow signal, provided that helmet inflow is adequate to match the patient's inspiratory efforts. Insufficient inflow resulted in tidal volume underestimation. In vivo data are needed to confirm these findings.

High-flow nasal cannula oxygen versus conventional oxygen therapy for acute respiratory failure due to COVID-19: a systematic review and meta-analysis

BACKGROUND

The effectiveness of high-flow nasal cannula oxygen therapy (HFNC) in patients with acute respiratory failure due to COVID-19 remains uncertain. We aimed at assessing whether HFNC is associated with reduced risk of intubation or mortality in patients with acute respiratory failure due to COVID-19 compared with conventional oxygen therapy (COT).

METHODS

In this systematic review and meta-analysis, we searched MEDLINE, Embase, Web of Science, and CENTRAL databases for randomized controlled trials (RCTs) and observational studies comparing HFNC vs. COT in patients with acute respiratory failure due to COVID-19, published in English from inception to December 2022. Pediatric studies, studies that compared HFNC with a noninvasive respiratory support other than COT and those in which intubation or mortality were not reported were excluded. Two authors independently screened and selected articles for inclusion, extracted data, and assessed the risk of bias. Fixed-effects or random-effects meta-analysis were performed according to statistical heterogeneity. Primary outcomes were risk of intubation and mortality across RCTs. Effect estimates were calculated as risk ratios and 95% confidence interval (RR; 95% CI). Observational studies were used for sensitivity analyses.

RESULTS

Twenty studies were analyzed, accounting for 8383 patients, including 6 RCTs (2509 patients) and 14 observational studies (5874 patients). By pooling the 6 RCTs, HFNC compared with COT significantly reduced the risk of intubation (RR 0.89, 95% CI 0.80 to 0.98; p = 0.02) and reduced length of stay in hospital. HFNC did not significantly reduce the risk of mortality (RR 0.93, 95% CI 0.77 to 1.11; p = 0.40).

CONCLUSIONS

In patients with acute respiratory failure due to COVID-19, HFNC reduced the need for intubation and shortened length of stay in hospital without significant decreased risk of mortality. Trial registration The study was registered on the International prospective register of systematic reviews (PROSPERO) at https://www.crd.york.ac.uk/prospero/ with the trial registration number CRD42022340035 (06/20/2022).

Redefining ARDS: a paradigm shift

Although the defining elements of "acute respiratory distress syndrome" (ARDS) have been known for over a century, the syndrome was first described in 1967. Since then, despite several revisions of its conceptual definition, it remains a matter of debate whether ARDS is a discrete nosological entity. After almost 60 years, it is appropriate to examine how critical care has modeled this fascinating syndrome and affected patient's outcome. Given that the diagnostic criteria of ARDS (e.g., increased pulmonary vascular permeability and diffuse alveolar damage) are difficult to ascertain in clinical practice, we believe that a step forward would be to standardize the assessment of pulmonary and extrapulmonary involvement in ARDS to ensure that each patient can receive the most appropriate and effective treatment. The selection of treatments based on arbitrary ranges of PaO2/FiO2 lacks sufficient sensitivity to individualize patient care.

A new reservoir-based CPAP with low oxygen consumption: the Bag-CPAP

BACKGROUND

Several noninvasive ventilatory supports rely in their design on high oxygen consumption which may precipitate oxygen shortage, as experienced during the COVID-19 pandemic. In this bench-to-bedside study, we assessed the performance of a new continuous positive airway pressure (CPAP) device integrating a large reservoir ("Bag-CPAP") designed to minimize oxygen consumption, and compared it with other CPAP devices.

METHODS

First, a bench study compared the performances of Bag-CPAP and four CPAP devices with an intensive care unit ventilator. Two FiO₂ targets (40-60% and 80-100%) at a predefined positive end expiratory pressure (PEEP) level between 5 and 10 cm H₂O were tested and fraction of inspired oxygen (FiO₂) and oxygen consumption were measured. Device-imposed work of breathing (WOB) was also evaluated. Second, an observational clinical study evaluated the new CPAP in 20 adult patients with acute respiratory failure in two hospitals in France. Actual FiO₂, PEEP, peripheral oxygen saturation, respiratory rate, and dyspnea score were assessed.

RESULTS

All six systems tested in the bench study reached the minimal FiO₂ target of 40% and four reached at least 80% FiO₂ while maintaining PEEP in the predefined range. Device-delivered FiO₂/consumed oxygen ratio was the highest with the new reservoir-based CPAP irrespective of FiO₂ target. WOB induced by the device was higher with Bag-CPAP. In the clinical study, Bag-CPAP was well tolerated and could reach high (> 90%) and moderate (> 50%) FiO₂ with an oxygen flow rate of 15 [15-16] and 8 [7-9] L/min, respectively. Dyspnea score improved significantly after introduction of Bag-CPAP, and SpO₂ increased.

CONCLUSIONS

In vitro, Bag-CPAP exhibited the highest oxygen saving properties albeit had increased WOB. It was well accepted clinically and reduced dyspnea. Bag-CPAP may be useful to treat patients with acute respiratory failure in the field, especially when facing constraints in oxygen delivery.

ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies

The aim of these guidelines is to update the 2017 clinical practice guideline (CPG) of the European Society of Intensive Care Medicine (ESICM). The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19). These guidelines were formulated by an international panel of clinical experts, one methodologist and patients' representatives on behalf of the ESICM. The review was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations and the quality of reporting of each study based on the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network guidelines. The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS). In addition, the CPG includes expert opinion on clinical practice and identifies the areas of future research.

Comparison of the efficacy and comfort of high-flow nasal cannula with different initial flow settings in patients with acute hypoxemic respiratory failure: a systematic review and network meta-analysis

BACKGROUND

High-flow nasal cannula (HFNC) has been proven effective in improving patients with acute hypoxemic respiratory failure (AHRF), but a discussion of its use for initial flow settings still need to be provided. We aimed to compare the effectiveness and comfort evaluation of HFNC with different initial flow settings in patients with AHRF.

METHODS

Studies published by October 10, 2022, were searched exhaustively in PubMed, Embase, Web of Science, Cochrane Library (CENTRAL), and the China National Knowledge Infrastructure (CNKI) database. Network meta-analysis (NMA) was performed with STATA 17.0 and R software (version 4.2.1). A Bayesian framework was applied for this NMA. Comparisons of competing models based on the deviance information criterion (DIC) were used to select the best model for NMA. The primary outcome is the intubation at day 28. Secondary outcomes included short-term and long-term mortality, comfort score, length of ICU or hospital stay, and 24-h PaO₂/FiO₂.

RESULTS

This NMA included 23 randomized controlled trials (RCTs) with 5774 patients. With NIV as the control, the HFNC_high group was significantly associated with lower intubation rates (odds ratio [OR] 0.72 95% credible interval [CrI] 0.56 to 0.93; moderate quality evidence) and short-term mortality (OR 0.81 95% CrI 0.69 to 0.96; moderate quality evidence). Using HFNC_Moderate (Mod) group (mean difference [MD] - 1.98 95% CrI -3.98 to 0.01; very low quality evidence) as a comparator, the HFNC_Low group had a slight advantage in comfort scores but no statistically significant difference. Of all possible interventions, the HFNC_High group had the highest probability of being the best in reducing intubation rates (73.04%), short-term (82.74%) and long-term mortality (67.08%). While surface under the cumulative ranking curve value (SUCRA) indicated that the HFNC_Low group had the highest probability of being the best in terms of comfort scores.

CONCLUSIONS

The high initial flow settings (50-60 L/min) performed better in decreasing the occurrence of intubation and mortality, albeit with poor comfort scores. Treatment of HFNC for AHRF patients ought to be initiated from moderate flow rates (30-40 L/min), and individualized flow settings can make HFNC more sensible in clinical practice.

Long-term outcomes of patients with COVID-19 treated with helmet noninvasive ventilation or usual respiratory support: follow-up study of the Helmet-COVID randomized clinical trial

PURPOSE

To evaluate whether helmet noninvasive ventilation compared to usual respiratory support reduces 180-day mortality and improves health-related quality of life (HRQoL) in patients with acute hypoxemic respiratory failure due to COVID-19 pneumonia.

METHODS

This is a pre-planned follow-up study of the Helmet-COVID trial. In this multicenter, randomized clinical trial, adults with acute hypoxemic respiratory failure (n = 320) due to coronavirus disease 2019 (COVID-19) were randomized to receive helmet noninvasive ventilation or usual respiratory support. The modified intention-to-treat population consisted of all enrolled patients except three who were lost at follow-up. The study outcomes were 180-day mortality, EuroQoL (EQ)-5D-5L index values, and EQ-visual analog scale (EQ-VAS). In the modified intention-to-treat analysis, non-survivors were assigned a value of 0 for EQ-5D-5L and EQ-VAS.

RESULTS

Within 180 days, 63/159 patients (39.6%) died in the helmet noninvasive ventilation group compared to 65/158 patients (41.1%) in the usual respiratory support group (risk difference - 1.5% (95% confidence interval [CI] - 12.3, 9.3, p = 0.78). In the modified intention-to-treat analysis, patients in the helmet noninvasive ventilation and the usual respiratory support groups did not differ in EQ-5D-5L index values (median 0.68 [IQR 0.00, 1.00], compared to 0.67 [IQR 0.00, 1.00], median difference 0.00 [95% CI - 0.32, 0.32; p = 0.91]) or EQ-VAS scores (median 70 [IQR 0, 93], compared to 70 [IQR 0, 90], median difference 0.00 (95% CI - 31.92, 31.92; p = 0.55).

CONCLUSIONS

Helmet noninvasive ventilation did not reduce 180-day mortality or improve HRQoL compared to usual respiratory support among patients with acute hypoxemic respiratory failure due to COVID-19 pneumonia.

propofol for sedation in invasively ventilated patients with acute hypoxemic respiratory failure: an a priori hypothesis substudy of a randomized controlled trial

BACKGROUND

Acute hypoxemic respiratory failure (AHRF) is a leading concern in critically ill patients. Experimental and clinical data suggest that early sedation with volatile anesthestics may improve arterial oxygenation and reduce the plasma and alveolar levels of markers of alveolar epithelial injury and of proinflammatory cytokines.

METHODS

An a priori hypothesis substudy of a multicenter randomized controlled trial (The Sedaconda trial, EUDRA CT Number 2016-004551-67). In the Sedaconda trial, 301 patients on invasive mechanical ventilation were randomized to 48 h of sedation with isoflurane or propofol in a 1:1 ratio. For the present substudy, patients with a ratio of arterial pressure of oxygen (PaO₂) to inspired fraction of oxygen (FiO₂), PaO₂/FiO₂, of ≤ 300 mmHg at baseline were included (n = 162). The primary endpoint was the change in PaO₂/FiO₂ between baseline and the end of study sedation. A subgroup analysis in patients with PaO₂/FiO₂ ≤ 200 mmHg was performed (n = 82).

RESULTS

Between baseline and the end of study sedation (48 h), oxygenation improved to a similar extent in the isoflurane vs. the propofol group (isoflurane: 199 ± 58 to 219 ± 76 mmHg (n = 70), propofol: 202 ± 62 to 236 ± 77 mmHg (n = 89); p = 0.185). On day seven after randomization, PaO₂/FiO₂ was 210 ± 79 mmHg in the isoflurane group (n = 41) and 185 ± 87 mmHg in the propofol group (n = 44; p = 0.411). In the subgroup of patients with PaO₂/FiO₂ ≤ 200 mmHg, PaO₂/FiO₂ increase between baseline and end of study sedation was 152 ± 33 to 186 ± 54 mmHg for isoflurane (n = 37), and 150 ± 38 to 214 ± 85 mmHg for propofol (n = 45; p = 0.029). On day seven, PaO₂/FiO₂ was 198 ± 69 mmHg in patients randomized to isoflurane (n = 20) and 174 ± 106 mmHg in patients randomized to propofol (n = 20; p = 0.933). Both for the whole study population and for the subgroup with PaO₂/FiO₂ ≤ 200 mmHg, no significant between-group differences were observed for PaCO₂, pH and tidal volume as well as 30-day mortality and ventilator-free days alive.

CONCLUSIONS

In patients with AHRF, inhaled sedation with isoflurane for a duration of up to 48 h did not lead to improved oxygenation in comparison to intravenous sedation with propofol. Trial registration The main study was registered in the European Medicines Agency's EU Clinical Trial register (EudraCT), 2016-004551-67, before including the first patient. The present substudy was registered at German Clinical Trials Register (DRKS, ID: DRKS00018959) on January 7th, 2020, before opening the main study data base and obtaining access to study results.

Effectiveness of high flow nasal cannula oxygen therapy in patients of acute pulmonary thromboembolism with acute hypoxemic respiratory failure

Background

Acute Pulmonary thromboembolism (PTE) is associated with acute hypoxemic respiratory failure (AHRF), which is a leading cause of death in these patients. High-Flow Nasal Cannula (HFNC) oxygen therapy is a cornerstone of the treatment of respiratory failure. The aim of the present study is to explore the efficacy of HFNC in the treatment of patients of acute PTE with acute hypoxemic respiratory failure in India.

Methods

This is a retrospective study of patients admitted to a tertiary care center with acute PTE with AHRF during the period from January 2018 to January 2020. After reviewing medical files, patients of acute PTE with AHRF treated with HFNC were included in the study. We analyzed the improvement in oxygenation parameters and respiratory rate, as well as outcome in these patients.

Results

During the above specified period, 12 patients suffering from PTE with AHRF were treated with HFNC. After 1 h of the initiation of HFNC along with anticoagulation, the respiratory parameters of patients significantly improved. HFNC was applied for a period of 6-10 days. None of the patients required intubation for AHRF, and all patients were discharged from the hospital on oral anticoagulants.

Conclusion

HFNC oxygen therapy in patients with acute PTE with AHRF showed rapid improvement of oxygenation and respiratory rate. HFNC oxygen therapy is an efficacious treatment for patients with AHRF secondary to acute PTE without any significant hemodynamic effect. It acts as a superior modality of oxygen therapy avoiding noninvasive and invasive ventilatory support.

Respiratory support strategy in adults with acute hypoxemic respiratory failure: a systematic review and network meta-analysis

Introduction

Network meta-analyses (NMAs) of respiratory management strategies for acute hypoxemic respiratory failure (AHRF) have been reported, but no previous study has compared noninvasive ventilation (NIV), high-flow nasal oxygen (HFNO), standard oxygenation therapy (SOT), and invasive mechanical ventilation (IMV) for de novo AHRF. Therefore, we conducted an NMA to assess the effectiveness of these four respiratory strategies in patients with de novo AHRF.

Methods

The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and Ichushi databases were searched. Studies including adults aged ≥18 years with AHRF and RCTs that compared two different oxygenation techniques (SOT, NIV, HFNO, or IMV) were selected. A frequentist-based approach with multivariate random-effects meta-analysis was used. The outcomes were mortality and intubation rates.

Results

Among the 14,263 records initially identified, 25 studies (3302 patients) were included. In the analysis of mortality, compared to SOT, NIV (risk ratio [RR], 0.76; 95% confidence interval [CI], 0.61–0.95) reduced mortality; however, IMV (RR, 1.01; 95% CI, 0.57–1.78) and HFNO (RR, 0.89; 95% CI, 0.66–1.20) did not. For assessments of the intubation incidence, compared to SOT, NIV use (RR, 0.63; 95% CI, 0.51–0.79) was associated with a reduction in intubation, but HFNO (RR, 0.82; 95% CI, 0.61–1.11) was not significant.

Conclusions

Our NMA demonstrated that only NIV showed clinical benefits compared with SOT as an initial respiratory strategy for de novo AHRF. Further investigation, especially comparison with HFNO, is warranted.

Trial registration

PROSPERO (registration number: CRD42020213948, 11/11/2020).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40981-022-00525-4.

Non-invasive oxygenation support in acutely hypoxemic COVID-19 patients admitted to the ICU: a multicenter observational retrospective study

Background

Non-invasive oxygenation strategies have a prominent role in the treatment of acute hypoxemic respiratory failure during the coronavirus disease 2019 (COVID-19). While the efficacy of these therapies has been studied in hospitalized patients with COVID-19, the clinical outcomes associated with oxygen masks, high-flow oxygen therapy by nasal cannula and non-invasive mechanical ventilation in critically ill intensive care unit (ICU) patients remain unclear.

Methods

In this retrospective study, we used the best of nine covariate balancing algorithms on all baseline covariates in critically ill COVID-19 patients supported with > 10 L of supplemental oxygen at one of the 26 participating ICUs in Catalonia, Spain, between March 14 and April 15, 2020.

Results

Of the 1093 non-invasively oxygenated patients at ICU admission treated with one of the three stand-alone non-invasive oxygenation strategies, 897 (82%) required endotracheal intubation and 310 (28%) died during the ICU stay. High-flow oxygen therapy by nasal cannula (n = 439) and non-invasive mechanical ventilation (n = 101) were associated with a lower rate of endotracheal intubation (70% and 88%, respectively) than oxygen masks (n = 553 and 91% intubated), p < 0.001. Compared to oxygen masks, high-flow oxygen therapy by nasal cannula was associated with lower ICU mortality (hazard ratio 0.75 [95% CI 0.58–0.98), and the hazard ratio for ICU mortality was 1.21 [95% CI 0.80–1.83] for non-invasive mechanical ventilation.

Conclusion

In critically ill COVID-19 ICU patients and, in the absence of conclusive data, high-flow oxygen therapy by nasal cannula may be the approach of choice as the primary non-invasive oxygenation support strategy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03905-5.

Helmet NIV in Acute Hypoxemic Respiratory Failure due to COVID-19: Change in PaO2/FiO2 Ratio a Predictor of Success

In acute respiratory failure due to severe coronavirus disease 2019 (COVID-19) pneumonia, mechanical ventilation remains challenging and may result in high mortality. The use of noninvasive ventilation (NIV) may delay required invasive ventilation, increase adverse outcomes, and have a potential aerosol risk to caregivers. Data of 30 patients were collected from patient files and analyzed. Twenty-one (70%) patients were weaned successfully after helmet-NIV support (NIV success group), and invasive mechanical ventilation was required in 9 (30%) patients (NIV failure group) of which 8 (26.7%) patients died. In NIV success vs failure patients, the mean baseline PaO₂/FiO₂ ratio (PFR) (147.2 ± 57.9 vs 156.8 ± 59.0 mm Hg; p = 0.683) and PFR before initiation of helmet (132.3 ± 46.9 vs 121.6 ± 32.7 mm Hg; p = 0.541) were comparable. The NIV success group demonstrated a progressive improvement in PFR in comparison with the failure group at 2 hours (158.8 ± 56.1 vs 118.7 ± 40.7 mm Hg; p = 0.063) and 24 hours (PFR-24) (204.4 ± 94.3 vs 121.3 ± 32.6; p = 0.016). As predictor variables, PFR-24 and change (delta) in PFR at 24 hours from baseline or helmet initiation (dPFR-24) were significantly associated with NIV success in univariate analysis but similar significance could not be reflected in multivariate analysis perhaps due to a small sample size of the study. The PFR-24 cutoff of 161 mm Hg and dPFR-24 cutoff of -1.44 mm Hg discriminate NIV success and failure groups with the area under curve (confidence interval) of 0.78 (0.62-0.95); p = 0.015 and 0.74 (0.55-0.93); p = 0.039, respectively. Helmet interface NIV may be a safe and effective tool for the management of patients with severe COVID-19 pneumonia with acute respiratory failure. More studies are needed to further evaluate the role of helmet NIV especially in patients with initial PFR <150 mm Hg to define PFR/dPFR cutoff at the earliest time point for prediction of helmet-NIV success. How to cite this article Jha OK, Kumar S, Mehra S, Sircar M, Gupta R. Helmet NIV in Acute Hypoxemic Respiratory Failure due to COVID-19: Change in PaO₂/FiO₂ Ratio a Predictor of Success. Indian J Crit Care Med 2021;25(10):1137-1146.

Oxygen Administration under Surgical Face Mask in COVID-19 Patients: A Game Changer

COVID-19 is a multifaceted infectious disease. The development of hypoxemic respiratory failure is not uncommon during the course of illness in some of them. The objectives of the present study were to assess the effect of the addition of a surgical face mask while delivering oxygen via nasal cannula in hypoxemic COVID-19 patients and highlight on the advantages and patient's comforts. We prospectively assessed 30 consecutive conscious and hypoxemic COVID-19 patients, requiring oxygen via nasal cannula. The mean PaO₂ without and with surgical face mask were 52 (+9) and 83 (−12) mm Hg respectively in the cohort, and the elevation in oxygen saturation was statistically significant (p <0.001). The present results encourage the delivery of oxygen under the surgical face mask in symptomatic COVID-19 patients, as it improves oxygen saturation and prevents aerosol dispersion with no change in PaCO₂. The other advantages of this method are a reduction in the total requirement of oxygen per patient, better utilization of scarce resources, and lessening of the expenses incurred for oxygen.

Are Mechanically Ventilated Patients with COVID-19 More Likely to Die Than Those without COVID-19? Perhaps Not

How to cite this article: Divatia JV. Are Mechanically Ventilated Patients with COVID-19 More Likely to Die Than Those without COVID-19? Perhaps Not. Indian J Crit Care Med 2021;25(12):1341-1342.

Feasibility of non-invasive nitric oxide gas inhalation to prevent endotracheal intubation in patients with acute hypoxemic respiratory failure: A single-centre experience

BACKGROUND

Acute hypoxemic respiratory failure (ARF) is characterized by both lower arterial oxygen and carbon dioxide tensions in the blood. First line treatment for ARF includes oxygen therapy - intially administered non invasively using nasal prongs, high flow nasal cannulae (HFNC) or masks. Invasive mechanical ventilation (IMV) is usually reserved for patients who are unable to maintain their airway, those with worsening hypoxemia, or those who develop respiratory muscle fatigue and consequent hypercapnia. Inhaled nitric oxide (iNO) gas is known to improve oxygenation in patients with ARF by manipulating ventilation-perfusion matching. Addition of iNO may potentially alleviate the need for IMV in selected patients.

CASE SUMMARY

In this article we report our preliminary experience of using HFNC to deliver oxygen and nitric oxide gas in patients with hypoxemic ARF as a strategy to potentially avoid IMV in selected patients.

CONCLUSION

This article demonstrates the feasibility of this technique based on our experience of patients with hypoxemic ARF and generates hypothesis for future studies.

Early versus late awake prone positioning in non-intubated patients with COVID-19

BACKGROUND

Awake prone positioning (APP) is widely used in the management of patients with coronavirus disease (COVID-19). The primary objective of this study was to compare the outcome of COVID-19 patients who received early versus late APP.

METHODS

Post hoc analysis of data collected for a randomized controlled trial (ClinicalTrials.gov NCT04325906). Adult patients with acute hypoxemic respiratory failure secondary to COVID-19 who received APP for at least one hour were included. Early prone positioning was defined as APP initiated within 24 h of high-flow nasal cannula (HFNC) start. Primary outcomes were 28-day mortality and intubation rate.

RESULTS

We included 125 patients (79 male) with a mean age of 62 years. Of them, 92 (73.6%) received early APP and 33 (26.4%) received late APP. Median time from HFNC initiation to APP was 2.25 (0.8-12.82) vs 36.35 (30.2-75.23) hours in the early and late APP group (p < 0.0001), respectively. Average APP duration was 5.07 (2.0-9.05) and 3.0 (1.09-5.64) hours per day in early and late APP group (p < 0.0001), respectively. The early APP group had lower mortality compared to the late APP group (26% vs 45%, p = 0.039), but no difference was found in intubation rate. Advanced age (OR 1.12 [95% CI 1.0-1.95], p = 0.001), intubation (OR 10.65 [95% CI 2.77-40.91], p = 0.001), longer time to initiate APP (OR 1.02 [95% CI 1.0-1.04], p = 0.047) and hydrocortisone use (OR 6.2 [95% CI 1.23-31.1], p = 0.027) were associated with increased mortality.

CONCLUSIONS

Early initiation (< 24 h of HFNC use) of APP in acute hypoxemic respiratory failure secondary to COVID-19 improves 28-day survival. Trial registration ClinicalTrials.gov NCT04325906.

Identification of persistent and resolving subphenotypes of acute hypoxemic respiratory failure in two independent cohorts

Background

Acute hypoxemic respiratory failure (HRF) is associated with high morbidity and mortality, but its heterogeneity challenges the identification of effective therapies. Defining subphenotypes with distinct prognoses or biologic features can improve therapeutic trials, but prior work has focused on ARDS, which excludes many acute HRF patients. We aimed to characterize persistent and resolving subphenotypes in the broader HRF population.

Methods

In this secondary analysis of 2 independent prospective ICU cohorts, we included adults with acute HRF, defined by invasive mechanical ventilation and PaO₂-to-FIO₂ ratio ≤ 300 on cohort enrollment (n = 768 in the discovery cohort and n = 1715 in the validation cohort). We classified patients as persistent HRF if still requiring mechanical ventilation with PaO₂-to-FIO₂ ratio ≤ 300 on day 3 following ICU admission, or resolving HRF if otherwise. We estimated relative risk of 28-day hospital mortality associated with persistent HRF, compared to resolving HRF, using generalized linear models. We also estimated fold difference in circulating biomarkers of inflammation and endothelial activation on cohort enrollment among persistent HRF compared to resolving HRF. Finally, we stratified our analyses by ARDS to understand whether this was driving differences between persistent and resolving HRF.

Results

Over 50% developed persistent HRF in both the discovery (n = 386) and validation (n = 1032) cohorts. Persistent HRF was associated with higher risk of death relative to resolving HRF in both the discovery (1.68-fold, 95% CI 1.11, 2.54) and validation cohorts (1.93-fold, 95% CI 1.50, 2.47), after adjustment for age, sex, chronic respiratory illness, and acute illness severity on enrollment (APACHE-III in discovery, APACHE-II in validation). Patients with persistent HRF displayed higher biomarkers of inflammation (interleukin-6, interleukin-8) and endothelial dysfunction (angiopoietin-2) than resolving HRF after adjustment. Only half of persistent HRF patients had ARDS, yet exhibited higher mortality and biomarkers than resolving HRF regardless of whether they qualified for ARDS.

Conclusion

Patients with persistent HRF are common and have higher mortality and elevated circulating markers of lung injury compared to resolving HRF, and yet only a subset are captured by ARDS definitions. Persistent HRF may represent a clinically important, inclusive target for future therapeutic trials in HRF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03755-7.

ROX index as a good predictor of high flow nasal cannula failure in COVID-19 patients with acute hypoxemic respiratory failure: A systematic review and meta-analysis

Purpose

Prediction of high flow nasal cannula (HFNC) failure in COVID-19 patients with acute hypoxemic respiratory failure (AHRF) may improve clinical management and stratification of patients for optimal treatment. We performed a systematic review and meta-analysis to determine performance of ROX index as a predictor of HFNC failure.

Materials and methods

Systematic search was performed in electronic databases (PubMed, Google Scholar, Web of Science and Cochrane Library) for articles published till 15 June 2021 investigating ROX index as a predictor for HFNC failure. Quality In Prognosis Studies (QUIPS) tool was used to analyze risk of bias for prognostic factors, by two independent authors.

Results

Eight retrospective or prospective cohort studies involving 1301 patients showed a good discriminatory value, summary area under the curve (sAUC) 0.81 (95% CI, 0.77–0.84) with sensitivity of 0.70 (95% CI, 0.59–0.80) and specificity of 0.79 (95% CI, 0.67–0.88) for predicting HNFC failure. The positive and negative likelihood ratio were 3.0 (95% CI, 2.2–5.3) and 0.37 (95% CI, 0.28–0.50) respectively, and was strongly associated with a promising predictive accuracy (Diagnostic odds ratio (DOR) 9, 95% CI, 5–16).

Conclusion

This meta-analysis suggests ROX index has good discriminating power for prediction of HFNC failure in COVID-19 patients with AHRF.

High-Flow Nasal Cannula Treatment in Patients with COVID-19 Acute Hypoxemic Respiratory Failure: A Prospective Cohort Study

BACKGROUND

Early use of high-flow nasal cannula (HFNC) decreases the need for endotracheal intubation (EI) in different respiratory failure causes. While HFNC is used in coronavirus disease 2019 (COVID-19)-related acute hypoxemic respiratory failure (AHRF) under weak recommendations, its efficacy remains to be investigated.

OBJECTIVES

The primary objective was to examine HFNC efficacy in preventing EI among COVID-19 patients with AHRF. Secondary objectives were to determine predictors of HFNC success/failure, mortality rate, and length of hospital and intensive care unit (ICU) stay.

PATIENTS AND METHODS

This is a prospective cohort study conducted at a single tertiary care centre in Saudi Arabia from April to August 2020. Adult patients admitted to the ICU with AHRF secondary to COVID-19 pneumonia and managed with HFNC were included. We excluded patients who were intubated or managed with non-invasive ventilation before HFNC.

RESULTS

Forty-four patients received HFNC for a median duration of 3 days (interquartile range, 1-5 days). The mean age was 57 ± 14 years, and 86% were men. HFNC failure and EI occurred in 29 (66%) patients. Patients in whom HNFC treatment failed had a higher risk of death (52% versus 0%; P = 0.001). After adjusting for confounding factors, a high SOFA score and a low ROX index were significantly associated with HFNC failure (hazard ratio [HR], 1.42; 95% confidence interval [CI], 1.04-1.93; P = 0.025; and HR, 0.61; 95% CI, 0.42-0.88; P = 0.008, respectively).

CONCLUSIONS

One-third of hypoxemic COVID-19 patients who received HFNC did not require intubation. High SOFA score and low ROX index were associated with HFNC failure.

High flow nasal cannula for adult acute hypoxemic respiratory failure in the ED setting: A narrative review

Introduction

High flow nasal cannula (HFNC) is a noninvasive ventilation (NIV) system that has demonstrated promise in the emergency department (ED) setting.

Objective

This narrative review evaluates the utility of HFNC in adult patients with acute hypoxemic respiratory failure in the ED setting.

Discussion

HFNC provides warm (37 °C), humidified (100% relative humidity) oxygen at high flows with a reliable fraction of inspired oxygen (FiO₂). HFNC can improve oxygenation, reduce airway resistance, provide humidified flow that can flush anatomical dead space, and provide a low amount of positive end expiratory pressure. Recent literature has demonstrated efficacy in acute hypoxemic respiratory failure, including pneumonia, acute respiratory distress syndrome (ARDS), coronavirus disease 2019 (COVID-19), interstitial lung disease, immunocompromised states, the peri-intubation state, and palliative care, with reduced need for intubation, length of stay, and mortality in some of these conditions. Individual patient factors play an important role in infection control risks with respect to the use of HFNC in patients with COVID-19. Appropriate personal protective equipment, adherence to hand hygiene, surgical mask placement over the HFNC device, and environmental controls promoting adequate room ventilation are the foundation for protecting healthcare personnel. Frequent reassessment of the patient placed on HFNC is necessary; those with severe end organ dysfunction, thoracoabdominal asynchrony, significantly increased respiratory rate, poor oxygenation despite HFNC, and tachycardia are at increased risk of HFNC failure and need for further intervention.

Conclusions

HFNC demonstrates promise in several conditions requiring respiratory support. Further randomized trials are needed in the ED setting.

Helmet and face mask for non-invasive respiratory support in patients with acute hypoxemic respiratory failure: A retrospective study

PURPOSE

Non-invasive respiratory support could reduce the incidence of intubation in patients with Acute Hypoxemic Respiratory Failure (AHRF). The optimal interface or modality of non-invasive respiratory support is debated. We sought to evaluate the differences between patients who succeeded or failed non-invasive respiratory support, with a specific focus on the type of non-invasive respiratory support (i.e. helmet CPAP versus face mask NIV).

MATERIALS AND METHODS

In a single-center observational retrospective study, we investigated baseline, clinical characteristics and AHRF management by non-invasive respiratory support between January 2015 to December 2016. Data on gas exchange and respiratory mechanics, non-invasive respiratory support duration, ICU length of stay and mortality were collected.

RESULTS

110 patients with AHRF were included of which 41 patients (37%) were intubated. The use of helmet CPAP (p = 0.016) and a lower fluid balance (p = 0.038) were independently associated with a decreased rate of intubation after adjustment for confounders. Face mask NIV patients trended to a higher respiratory frequency at 1 h after treatment [28 (22-36) versus 24 (18-29) hours, p = 0.067], and showed a longer ICU stay (p = 0.009) compared to patients treated with helmet CPAP.

CONCLUSIONS

Helmet CPAP and a lower fluid balance were independent predictors of a lower intubation rate in AHRF patients in ICU. Prospective studies aimed at identifying the optimal interface and modality of non-invasive respiratory support in AHRF patients are needed.

COVID-19 Pneumonia and ROX index: Time to set a new threshold for patients admitted outside the ICU

High flow nasal cannula (HFNC) is used to treat acute hypoxemic respiratory failure (AHRF) even outside the ICU and the ROX index (pulse oximetry/fraction of inspired oxygen/respiratory rate) may predict HFNC failure.

Objective

The purpose of this investigation was therefore to verify whether the ROX index is an accurate predictor of HFNC failure for COVID-19 patients treated outside the intensive care unit (ICU) and to evaluate the validity of the previously suggested threshold.

Design

Multicenter study. Retrospective observational analysis of prospectively collected data.

Setting

3 centres specialized in non-invasive respiratory support (Buenos Aires, Argentina; Bolzano and Treviso, Italy). Patients treated outside the ICU were analysed

Measurements

The variables to calculate the ROX index were collected during the first day of therapy at 2, 6, 12 and 24 hours and then recorded every 24 hours. HFNC failure was defined as escalation of respiratory support to invasive mechanical ventilation (IMV) or death.

Main results

A total of 35 (29%) patients failed HFNC and required intubation. ROC analysis identified the 12-hour ROX index as the best predictor of intubation with an AUC of 0.7916[CI 95% 0.6905-0.8927] and the best threshold to be 5.99[Specificity 96% Sensitivity 62%]. In the survival analysis, a ROX value <5.99 was associated with an increased risk of failure (p = 0008 log – rank test). The threshold of 4,9 identified by Roca as the best predictor in non-COVID patients, was not able to discriminate between success and failure (p = 0.4 log-rank test) in our patients.

Conclusions

ROX index may be useful in guiding the clinicians in their decision to intubate patients, especially in patients with moderate ARF, treated therefore outside the ICU. Indeed, it also demonstrates a different threshold value than reported for non-COVID patients, possibly related to the different mechanisms of hypoxia.

Death in hospital following ICU discharge: insights from the LUNG SAFE study

Background

To determine the frequency of, and factors associated with, death in hospital following ICU discharge to the ward.

Methods

The Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE study was an international, multicenter, prospective cohort study of patients with severe respiratory failure, conducted across 459 ICUs from 50 countries globally. This study aimed to understand the frequency and factors associated with death in hospital in patients who survived their ICU stay. We examined outcomes in the subpopulation discharged with no limitations of life sustaining treatments (‘treatment limitations’), and the subpopulations with treatment limitations.

Results

2186 (94%) patients with no treatment limitations discharged from ICU survived, while 142 (6%) died in hospital. 118 (61%) of patients with treatment limitations survived while 77 (39%) patients died in hospital. Patients without treatment limitations that died in hospital after ICU discharge were older, more likely to have COPD, immunocompromise or chronic renal failure, less likely to have trauma as a risk factor for ARDS. Patients that died post ICU discharge were less likely to receive neuromuscular blockade, or to receive any adjunctive measure, and had a higher pre- ICU discharge non-pulmonary SOFA score. A similar pattern was seen in patients with treatment limitations that died in hospital following ICU discharge.

Conclusions

A significant proportion of patients die in hospital following discharge from ICU, with higher mortality in patients with limitations of life-sustaining treatments in place. Non-survivors had higher systemic illness severity scores at ICU discharge than survivors.

Trial Registration: ClinicalTrials.gov NCT02010073.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03465-0.

Non-invasive respiratory support in the treatment of acute hypoxemic respiratory failure secondary to CoViD-19 related pneumonia

In the last 11 months, the SARS-CoV-2 pandemic has overwhelmed and disrupted the whole world in health, social and economic terms. We are progressively learning more and more about the epidemiological and clinical features that distinguish CoViD-19 from any previous experience in the emergency and critical care setting. Experiences are multiplying with regard to the use of non-invasive respiratory support techniques in the context of acute hypoxemic respiratory failure secondary to CoViD-19-related pneumonia. Doubts still far outweigh certainties, but a growing series of mostly monocentric and retrospective studies are becoming available as concrete decision-making and operational support for healthcare workers. In this review the available studies and experiences about non-invasive respiratory support in the treatment of Covid-19 related respiratory failure, mainly coming from outside the ICU setting, will be discussed.

Continuous positive airway pressure for respiratory support during COVID-19 pandemic: a frugal approach from bench to bedside

BACKGROUND

We describe a frugal approach (focusing on needs, performance, and costs) to manage a massive influx of COVID-19 patients with acute hypoxemic respiratory failure (AHRF) using the Boussignac valve protected by a filter ("Filter Frugal CPAP", FF-CPAP) in and out the ICU.

METHODS

(1) A bench study measured the impact of two filters with different mechanical properties on CPAP performances, and pressures were also measured in patients. (2) Non-ICU healthcare staff working in COVID-19 intermediate care units were trained with a video tutorial posted on a massive open online course. (3) A clinical study assessed the feasibility and safety of using FF-CPAP to maintain oxygenation and manage patients out of the ICU during a massive outbreak.

RESULTS

Bench assessments showed that adding a filter did not affect the effective pressure delivered to the patient. The resistive load induced by the filter variably increased the simulated patient's work of breathing (6-34%) needed to sustain the tidal volume, depending on the filter's resistance, respiratory mechanics and basal inspiratory effort. In patients, FF-CPAP achieved pressures similar to those obtained on the bench. The massive training tool provided precious information on the use of Boussignac FF-CPAP on COVID-19 patients. Then 85 COVID-19 patients with ICU admission criteria over a 1-month period were studied upon FF-CPAP initiation for AHRF. FF-CPAP significantly decreased respiratory rate and increased SpO₂. Thirty-six (43%) patients presented with respiratory indications for intubation prior to FF-CPAP initiation, and 13 (36%) of them improved without intubation. Overall, 31 patients (36%) improved with FF-CPAP alone and 17 patients (20%) did not require ICU admission. Patients with a respiratory rate > 32 breaths/min upon FF-CPAP initiation had a higher cumulative probability of intubation (p < 0.001 by log-rank test).

CONCLUSION

Adding a filter to the Boussignac valve does not affect the delivered pressure but may variably increase the resistive load depending on the filter used. Clinical assessment suggests that FF-CPAP is a frugal solution to provide a ventilatory support and improve oxygenation to numerous patients suffering from AHRF in the context of a massive outbreak.

High-flow nasal oxygen in patients with COVID-19-associated acute respiratory failure

PURPOSE

Whether the use of high-flow nasal oxygen in adult patients with COVID-19 associated acute respiratory failure improves clinically relevant outcomes remains unclear. We thus sought to assess the effect of high-flow nasal oxygen on ventilator-free days, compared to early initiation of invasive mechanical ventilation, on adult patients with COVID-19.

METHODS

We conducted a multicentre cohort study using a prospectively collected database of patients with COVID-19 associated acute respiratory failure admitted to 36 Spanish and Andorran intensive care units (ICUs). Main exposure was the use of high-flow nasal oxygen (conservative group), while early invasive mechanical ventilation (within the first day of ICU admission; early intubation group) served as the comparator. The primary outcome was ventilator-free days at 28 days. ICU length of stay and all-cause in-hospital mortality served as secondary outcomes. We used propensity score matching to adjust for measured confounding.

RESULTS

Out of 468 eligible patients, a total of 122 matched patients were included in the present analysis (61 for each group). When compared to early intubation, the use of high-flow nasal oxygen was associated with an increase in ventilator-free days (mean difference: 8.0 days; 95% confidence interval (CI): 4.4 to 11.7 days) and a reduction in ICU length of stay (mean difference: - 8.2 days; 95% CI - 12.7 to - 3.6 days). No difference was observed in all-cause in-hospital mortality between groups (odds ratio: 0.64; 95% CI: 0.25 to 1.64).

CONCLUSIONS

The use of high-flow nasal oxygen upon ICU admission in adult patients with COVID-19 related acute hypoxemic respiratory failure may lead to an increase in ventilator-free days and a reduction in ICU length of stay, when compared to early initiation of invasive mechanical ventilation. Future studies should confirm our findings.

Bronchoscopic Cryotherapy for Acute Hypoxemic Respiratory Failure in Three Mechanically Ventilated Patients: A Case Series

Endobronchial blood clots or mucus plugs can present with minimal symptoms or acute airway obstruction in the intensive care unit (ICU) patients. Acute airway obstruction can lead to rapid worsening of dyspnea owing to poor oxygenation due to collapse of the lung. Prompt recognition and treatment of this condition can translate into a successful outcome by decreasing morbidity and mortality and facilitating successful weaning of these patients. When conventional methods fail to relieve the obstruction, cryoextraction a novel technique, may prove to be a useful alternative for the removal of these clots and mucus plugs. Cryoextraction is best performed with rigid bronchoscopic intubation. However, in certain conditions, it may be used with a flexible fiberoptic bronchoscope (FOB) through an endotracheal tube, especially when bedside procedure is required in ICU patients. In this series, three cases are being discussed where bedside flexible bronchoscopy-guided cryoextraction was done leading to a successful resolution of acute hypoxemic respiratory failure.

How to cite this article: Tale S, Meitei SP, Prakash V, Negi A, Mishra M, Sindhwani G. Bronchoscopic Cryotherapy for Acute Hypoxemic Respiratory Failure in Three Mechanically Ventilated Patients: A Case Series. Indian J Crit Care Med 2021;25(1):94–96.

Nasal high flow higher than 60 L/min in patients with acute hypoxemic respiratory failure: a physiological study

Background

Nasal high flow delivered at flow rates higher than 60 L/min in patients with acute hypoxemic respiratory failure might be associated with improved physiological effects. However, poor comfort might limit feasibility of its clinical use.

Methods

We performed a prospective randomized cross-over physiological study on 12 ICU patients with acute hypoxemic respiratory failure. Patients underwent three steps at the following gas flow: 0.5 L/kg PBW/min, 1 L/kg PBW/min, and 1.5 L/kg PBW/min in random order for 20 min. Temperature and FiO₂ remained unchanged. Toward the end of each phase, we collected arterial blood gases, lung volumes, and regional distribution of ventilation assessed by electrical impedance tomography (EIT), and comfort.

Results

In five patients, the etiology was pulmonary; infective disease characterized seven patients; median PaO₂/FiO₂ at enrollment was 213 [IQR 136–232]. The range of flow rate during NHF 1.5 was 75–120 L/min. PaO₂/FiO₂ increased with flow, albeit non significantly (p = 0.064), PaCO₂ and arterial pH remained stable (p = 0.108 and p = 0.105). Respiratory rate decreased at higher flow rates (p = 0.014). Inhomogeneity of ventilation decreased significantly at higher flows (p = 0.004) and lung volume at end-expiration significantly increased (p = 0.007), but mostly in the non-dependent regions. Comfort was significantly poorer during the step performed at the highest flow (p < 0.001).

Conclusions

NHF delivered at rates higher than 60 L/min in critically ill patients with acute hypoxemic respiratory failure is associated with reduced respiratory rate, increased lung homogeneity, and additional positive pressure effect, but also with worse comfort.

Causes and characteristics of death in patients with acute hypoxemic respiratory failure and acute respiratory distress syndrome: a retrospective cohort study

Background

Acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) are associated with high in-hospital mortality. However, in cohorts of ARDS patients from the 1990s, patients more commonly died from sepsis or multi-organ failure rather than refractory hypoxemia. Given increased attention to lung-protective ventilation and sepsis treatment in the past 25 years, we hypothesized that causes of death may be different among contemporary cohorts. These differences may provide clinicians with insight into targets for future therapeutic interventions.

Methods

We identified adult patients hospitalized at a single tertiary care center (2016–2017) with AHRF, defined as PaO₂/FiO₂ ≤ 300 while receiving invasive mechanical ventilation for > 12 h, who died during hospitalization. ARDS was adjudicated by multiple physicians using the Berlin definition. Separate abstractors blinded to ARDS status collected data on organ dysfunction and withdrawal of life support using a standardized tool. The primary cause of death was defined as the organ system that most directly contributed to death or withdrawal of life support.

Results

We identified 385 decedents with AHRF, of whom 127 (33%) had ARDS. The most common primary causes of death were sepsis (26%), pulmonary dysfunction (22%), and neurologic dysfunction (19%). Multi-organ failure was present in 70% at time of death, most commonly due to sepsis (50% of all patients), and 70% were on significant respiratory support at the time of death. Only 2% of patients had insupportable oxygenation or ventilation. Eighty-five percent died following withdrawal of life support. Patients with ARDS more often had pulmonary dysfunction as the primary cause of death (28% vs 19%; p = 0.04) and were also more likely to die while requiring significant respiratory support (82% vs 64%; p <  0.01).

Conclusions

In this contemporary cohort of patients with AHRF, the most common primary causes of death were sepsis and pulmonary dysfunction, but few patients had insupportable oxygenation or ventilation. The vast majority of deaths occurred after withdrawal of life support. ARDS patients were more likely to have pulmonary dysfunction as the primary cause of death and die while requiring significant respiratory support compared to patients without ARDS.

Respiratory Care for Severe COVID-19

Coronavirus disease-2019 (COVID-19) pandemic has put a severe strain on the healthcare services around the globe. Among the most affected areas of the hospital is critical care. A large number of patients of COVID-19 need critical care especially respiratory care. The acute hypoxemic respiratory failure (AHRF) due to COVID-19 needs careful understanding and strategies for management. Research in AHRF due to COVID-19 has progressed rapidly over the last 6 months.

HOW TO CITE THIS ARTICLE

Prayag S. Respiratory Care for Severe COVID-19. Indian J Crit Care Med 2020;24(7):493-495.

Voluntary Prone Position for Acute Hypoxemic Respiratory Failure in Unintubated Patients

Severe hypoxemic respiratory failure is frequently managed with invasive mechanical ventilation with or without prone position (PP). We describe 13 cases of nonhypercapnic acute hypoxemic respiratory failure (AHRF) of varied etiology, who were treated successfully in PP without the need for intubation. Noninvasive ventilation (NIV), high-flow oxygen via nasal cannula, supplementary oxygen with venturi face mask, or nasal cannula were used variedly in these patients. Mechanical ventilatory support is offered to patients with AHRF when other methods, such as NIV and oxygen via high-flow nasal cannula, fail. Invasive mechanical ventilation is fraught with complications which could be immediate, ranging from worsening of hypoxemia, worsening hemodynamics, loss of airway, and even death. Late complications could be ventilator-associated pneumonia, biotrauma, tracheal stenosis, etc. Prone position is known to improve oxygenation and outcome in adult respiratory distress syndrome. We postulated that positioning an unintubated patient with AHRF in PP will improve oxygenation and avoid the need for invasive mechanical ventilation and thereby its complications. Here, we describe a series of 13 patients with hypoxemic respiratory of varied etiology, who were successfully treated in the PP without endotracheal intubation. Two patients (15.4%) had mild, nine (69.2%) had moderate, and two (15.4%) had severe hypoxemia. Oxygenation as assessed by PaO₂/FiO₂ ratio in supine position was 154 ± 52, which improved to 328 ± 65 after PP. Alveolar to arterial (A-a) O₂ gradient improved from a median of 170.5 mm Hg interquartile range (IQR) (127.8, 309.7) in supine position to 49.1 mm Hg IQR (45.0, 56.6) after PP. This improvement in oxygenation took a median of 46 hours, IQR (24, 109). Thus, voluntary PP maneuver improved oxygenation and avoided endotracheal intubation in a select group of patients with hypoxemic respiratory failure. This maneuver may be relevant in the ongoing novel coronavirus disease pandemic by potentially reducing endotracheal intubation and the need for ventilator and therefore better utilization of critical care services.

Increasing support by nasal high flow acutely modifies the ROX index in hypoxemic patients: A physiologic study

The ROX (Respiratory rate-OXygenation) index is an early predictor of failure of nasal high flow (NHF), with lower values indicating higher risk of intubation. We measured the ROX index at set flow rate of 30 and 60 l/min in 57 hypoxemic patients on NHF. Patients with increased ROX index values at higher flow (n = 40) showed worse baseline oxygenation, higher respiratory rate and lower ROX index in comparison to patients with unchanged or decreased ROX index values (n = 17). The ROX index variation between flows was correlated with the change in end expiratory lung volume. Set flow rate during NHF might impact the ROX index value.

Early high-flow nasal cannula oxygen therapy in adults with acute hypoxemic respiratory failure in the ED: A before-after study

OBJECTIVES

To compare clinical impact after early initiation of high-flow nasal cannula oxygen therapy (HFNC) versus standard oxygen in patients admitted to an emergency department (ED) for acute hypoxemic respiratory failure.

METHODS

We performed a prospective before-after study at EDs in two centers including patients with acute hypoxemic respiratory failure defined by a respiratory rate above 25 breaths/min or signs of increased breathing effort under additional oxygen for a pulse oximetry above 92%. Patients with cardiogenic pulmonary edema or exacerbation of chronic lung disease were excluded. All patients were treated with standard oxygen during the first period and with HFNC during the second. The primary outcome was the proportion of patients with improved respiratory failure 1 h after treatment initiation (respiratory rate ≤ 25 breaths/min without signs of increased breathing effort). Dyspnea and blood gases were also assessed.

RESULTS

Among the 102 patients included, 48 were treated with standard oxygen and 54 with HFNC. One hour after treatment initiation, patients with HFNC were much more likely to recover from respiratory failure than those treated with standard oxygen: 61% (33 of 54 patients) versus 15% (7 of 48 patients), P < 0.001. They also showed greater improvement in oxygenation (increase in PaO₂ was 31 mm Hg [0-67] vs. 9 [-9-36], P = 0.02), and in feeling of breathlessness.

CONCLUSIONS

As compared to standard oxygen, patients with acute hypoxemic respiratory failure treated with HFNC at the ED had better oxygenation, less breathlessness and were more likely to show improved respiratory failure 1 h after initiation.

Identifying associations between diabetes and acute respiratory distress syndrome in patients with acute hypoxemic respiratory failure: an analysis of the LUNG SAFE database

BACKGROUND

Diabetes mellitus is a common co-existing disease in the critically ill. Diabetes mellitus may reduce the risk of acute respiratory distress syndrome (ARDS), but data from previous studies are conflicting. The objective of this study was to evaluate associations between pre-existing diabetes mellitus and ARDS in critically ill patients with acute hypoxemic respiratory failure (AHRF).

METHODS

An ancillary analysis of a global, multi-centre prospective observational study (LUNG SAFE) was undertaken. LUNG SAFE evaluated all patients admitted to an intensive care unit (ICU) over a 4-week period, that required mechanical ventilation and met AHRF criteria. Patients who had their AHRF fully explained by cardiac failure were excluded. Important clinical characteristics were included in a stepwise selection approach (forward and backward selection combined with a significance level of 0.05) to identify a set of independent variables associated with having ARDS at any time, developing ARDS (defined as ARDS occurring after day 2 from meeting AHRF criteria) and with hospital mortality. Furthermore, propensity score analysis was undertaken to account for the differences in baseline characteristics between patients with and without diabetes mellitus, and the association between diabetes mellitus and outcomes of interest was assessed on matched samples.

RESULTS

Of the 4107 patients with AHRF included in this study, 3022 (73.6%) patients fulfilled ARDS criteria at admission or developed ARDS during their ICU stay. Diabetes mellitus was a pre-existing co-morbidity in 913 patients (22.2% of patients with AHRF). In multivariable analysis, there was no association between diabetes mellitus and having ARDS (OR 0.93 (0.78-1.11); p = 0.39), developing ARDS late (OR 0.79 (0.54-1.15); p = 0.22), or hospital mortality in patients with ARDS (1.15 (0.93-1.42); p = 0.19). In a matched sample of patients, there was no association between diabetes mellitus and outcomes of interest.

CONCLUSIONS

In a large, global observational study of patients with AHRF, no association was found between diabetes mellitus and having ARDS, developing ARDS, or outcomes from ARDS.

TRIAL REGISTRATION

NCT02010073 . Registered on 12 December 2013.

Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula

BACKGROUND

The high-flow nasal cannula (HFNC) delivers up to 60 l/min of humidified air/oxygen blend at a temperature close to that of the human body. In this study, we tested whether higher temperature and flow decrease patient comfort. In more severe patients, instead, we hypothesized that higher flow might be associated with improved comfort.

METHODS

A prospective, randomized, cross-over study was performed on 40 acute hypoxemic respiratory failure (AHRF) patients (PaO₂/FiO₂ ≤ 300 + pulmonary infiltrates + exclusion of cardiogenic edema) supported by HFNC. The primary outcome was the assessment of patient comfort during HFNC delivery at increasing flow and temperature. Two flows (30 and 60 l/min), each combined with two temperatures (31 and 37 °C), were randomly applied for 20 min (four steps per patient), leaving clinical FiO₂ unchanged. Toward the end of each step, the following were recorded: comfort by Visual Numerical Scale ranging between 1 (extreme discomfort) and 5 (very comfortable), together with respiratory parameters. A subgroup of more severe patients was defined by clinical FiO₂ ≥ 45%.

RESULTS

Patient comfort was reported as significantly higher during steps at the lower temperature (31 °C) in comparison to 37 °C, with the HFNC set at both 30 and 60 l/min (p < 0.0001). Higher flow, however, was not associated with poorer comfort. In the subgroup of patients with clinical FiO₂ ≥ 45%, both lower temperature (31 °C) and higher HFNC flow (60 l/min) led to higher comfort (p < 0.01).

CONCLUSIONS

HFNC temperature seems to significantly impact the comfort of AHRF patients: for equal flow, lower temperature could be more comfortable. Higher flow does not decrease patient comfort; at variance, it improves comfort in the more severely hypoxemic patient.

Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula

BACKGROUND

The high-flow nasal cannula (HFNC) delivers up to 60 l/min of humidified air/oxygen blend at a temperature close to that of the human body. In this study, we tested whether higher temperature and flow decrease patient comfort. In more severe patients, instead, we hypothesized that higher flow might be associated with improved comfort.

METHODS

A prospective, randomized, cross-over study was performed on 40 acute hypoxemic respiratory failure (AHRF) patients (PaO₂/FiO₂ ≤ 300 + pulmonary infiltrates + exclusion of cardiogenic edema) supported by HFNC. The primary outcome was the assessment of patient comfort during HFNC delivery at increasing flow and temperature. Two flows (30 and 60 l/min), each combined with two temperatures (31 and 37 °C), were randomly applied for 20 min (four steps per patient), leaving clinical FiO₂ unchanged. Toward the end of each step, the following were recorded: comfort by Visual Numerical Scale ranging between 1 (extreme discomfort) and 5 (very comfortable), together with respiratory parameters. A subgroup of more severe patients was defined by clinical FiO₂ ≥ 45%.

RESULTS

Patient comfort was reported as significantly higher during steps at the lower temperature (31 °C) in comparison to 37 °C, with the HFNC set at both 30 and 60 l/min (p < 0.0001). Higher flow, however, was not associated with poorer comfort. In the subgroup of patients with clinical FiO₂ ≥ 45%, both lower temperature (31 °C) and higher HFNC flow (60 l/min) led to higher comfort (p < 0.01).

CONCLUSIONS

HFNC temperature seems to significantly impact the comfort of AHRF patients: for equal flow, lower temperature could be more comfortable. Higher flow does not decrease patient comfort; at variance, it improves comfort in the more severely hypoxemic patient.