Failure of Noninvasive Ventilation for De Novo Acute Hypoxemic Respiratory Failure: Role of Tidal Volume

Non-invasive support for the hypoxaemic patient

Optimisation of oxygenation strategies in patients with hypoxaemic respiratory failure is a top priority for acute care physicians, as hypoxaemic respiratory failure is one of the leading causes of admission. Various oxygenation methods range from non-invasive face masks to high flow nasal cannulae, which have advantages and disadvantages for this heterogeneous patient group. Focus has turned toward examining the benefits of non-invasive ventilation, as this was heavily researched in resource-limited settings during the COVID-19 pandemic. The oxygenation strategy should be determined on an individualised basis for patients, and with new evidence from the COVID-19 pandemic, providers may now consider placing further emphasis on non-invasive approaches. As non-invasive ventilation continues to be used in increasing frequency, new methods of monitoring patient response, including when to escalate ventilation strategy, will need to be validated.

Advantages and drawbacks of helmet noninvasive support in acute respiratory failure

INTRODUCTION

Non-invasive ventilation (NIV) represents an effective strategy for managing acute respiratory failure. Facemask NIV is strongly recommended in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) with hypercapnia and acute cardiogenic pulmonary edema (ACPE). Its role in managing acute hypoxemic respiratory failure (AHRF) remains a debated issue. NIV and continuous positive airway pressure (CPAP) delivered through the helmet are recently receiving growing interest for AHRF management.

AREAS COVERED

In this narrative review, we discuss the clinical applications of helmet support compared to the other available noninvasive strategies in the different phenotypes of acute respiratory failure.

EXPERT OPINION

Helmets enable the use of high positive end-expiratory pressure, which may protect from self-inflicted lung injury: in AHRF, the possible superiority of helmet support over other noninvasive strategies in terms of clinical outcome has been hypothesized in a network metanalysis and a randomized trial, but has not been confirmed by other investigations and warrants confirmation. In AECOPD patients, helmet efficacy may be inferior to that of face masks, and its use prompts caution due to the risk of CO₂ rebreathing. Helmet support can be safely applied in hypoxemic patients with ACPE, with no advantages over facemasks.

Usefulness and limitations of the acute respiratory distress syndrome definitions in non-intubated patients. A narrative review

According to the Berlin Definition of acute respiratory distress syndrome (ARDS), a positive end-expiratory pressure (PEEP) of at least 5 cmH₂O is required to diagnose and grade ARDS. While the Berlin consensus statement specifically acknowledges the role of non-invasive ventilation (NIV) in mild ARDS, this stratification has traditionally presumed a mechanically ventilated patient in the context of moderate to severe ARDS. This may not accurately reflect today's reality of clinical respiratory care. NIV and high-flow nasal cannula oxygen therapy (HFNO) have been used for managing of severe forms of acute hypoxemic respiratory failure with growing frequency, including in patients showing pathophysiological signs of ARDS. This became especially relevant during the COVID-19 pandemic. The levels of PEEP achieved with HFNO have been particularly controversial, and the exact FiO₂ it achieves is subject to variability. Pinpointing the presence of ARDS in patients receiving HNFO and the severity in those receiving NIV therefore remains methodically problematic. This narrative review highlights the evolution of the ARDS definition in the context of non-invasive ventilatory support and provides an overview of the parallel development of definitions and ventilatory management of ARDS. It summarizes the methodology applied in clinical trials to classify ARDS in non-intubated patients and the respective consequences on treatment. As ARDS severity has significant therapeutic and prognostic consequences, and earlier treatment in non-intubated patients may be beneficial, closing this knowledge gap may ultimately be a relevant step to improve comparability in clinical trial design and outcomes.

Noninvasive Mechanical Ventilation in Patients with Viral Pneumonia-Associated Acute Respiratory Distress Syndrome: An Observational Retrospective Study

OBJECTIVES

Appropriate mechanical ventilation may change the prognosis of patients with viral pneumonia-associated acute respiratory distress syndrome (ARDS). This study aimed to identify the factors associated with the success of noninvasive ventilation in the management of patients with ARDS secondary to respiratory viral infection.

METHODS

In this retrospective cohort study, all patients with viral pneumonia-associated ARDS were divided into the noninvasive mechanical ventilation (NIV) success group and the NIV failure group. The demographic and clinical data of all patients were collected. The factors associated with the success of noninvasive ventilation were identified by the logistic regression analysis.

RESULTS

Among this cohort, 24 patients with an average age of 57.9 ± 17.0 years received successful NIVs, and NIV failure occurred in 21 patients with an average age of 54.1 ± 14.0 years. The independent influencing factors for the success of the NIV were the acute physiology and chronic health evaluation (APACHE) II score (odds ratio (OR): 1.83, 95% confidence interval (CI): 1.10-3.03) and lactate dehydrogenase (LDH) (OR: 1.011, 95% CI: 1.00-1.02). When the oxygenation index (OI) is <95 mmHg, APACHE II > 19, and LDH > 498 U/L, the sensitivity and specificity of predicting a failed NIV were (66.6% (95% CI: 43.0%-85.4%) and 87.5% (95% CI: 67.6%-97.3%)); (85.7% (95% CI: 63.7%-97.0%) and 79.1% (95% CI: 57.8%-92.9%)); (90.4% (95% CI: 69.6%-98.8%) and 62.5% (95% CI: 40.6%-81.2%)), respectively. The areas under the receiver operating characteristic curve (AUC) of the OI, APACHE II scores, and LDH were 0.85, which was lower than the AUC of the OI combined with LDH and the APACHE II score (OLA) of 0.97 (P=0.0247).

CONCLUSIONS

Overall, patients with viral pneumonia-associated ARDS receiving successful NIV have lower mortality rates than those for whom NIV failed. In patients with influenza A-associated ARDS, the OI may not be the only indicator of whether NIV can be used; a new indicator of NIV success may be the OLA.

Comparison of high-flow nasal therapy, noninvasive ventilation, and continuous positive airway pressure on outcomes in critically ill patients admitted for COVID-19 with acute respiratory failure

BACKGROUND

The optimal first-line noninvasive respiratory support (NIRS) to improve outcome in patients affected by COVID-19 pneumonia admitted to ICU is still debated.

METHODS

We conducted a retrospective study in seven French ICUs, including all adults admitted between July and December 2020 with documented SARS-CoV-2 acute respiratory failure (PaO2/FiO2<300 mmHg), and treated with either high-flow nasal therapy (HFNT) alone, noninvasive ventilation alone or in combination with HFNT (NIV), or continuous positive airway pressure alone or in combination with HFNT (CPAP). The primary outcome was NIRS failure at day 28, defined as the need for endotracheal intubation (ETI) or death without ETI.

RESULTS

Among the 355 patients included, 160 (45%) were treated with HFNT alone, 115 (32%) with NIV and 80 (23%) with CPAP. The primary outcome occurred in 65 (41%), 69 (60%), and 25 (31%) patients among those treated with HFNT alone, NIV, and CPAP, respectively (P<0.001). After univariate analysis, patients treated with CPAP had a trend for a lower incidence of the primary outcome, whereas patients treated with NIV had a significant higher incidence of the primary outcome, both compared to those treated with HFNT alone (unadjusted Hazard ratio 0.67; 95% CI [0.42-1.06], and 1.58; 95% CI [1.12-2.22]; P=0.09 and 0.008, respectively).

CONCLUSIONS

Among ICU patients admitted for severe COVID-19 pneumonia and managed with NIRS, the outcome seems to differ according to the initial chosen strategy. Prospective randomized controlled studies are warranted to identify the optimal strategy.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

High-flow nasal oxygen in acute hypoxemic respiratory failure: A narrative review of the evidence before and after the COVID-19 pandemic

High-flow nasal oxygen (HFNO) is a type of non-invasive advanced respiratory support that allows the delivery of high-flow and humidified air through a nasal cannula. It can deliver a higher inspired oxygen fraction than conventional oxygen therapy (COT), improves secretion clearance, has a small positive end-expiratory pressure, and exhibits a washout effect on the upper air space that diminishes dead space ventilation. HFNO has been shown to reduce the work of breathing in acute hypoxemic respiratory failure (AHRF) and has become an interesting option for non-invasive respiratory support. Evidence published before the COVID-19 pandemic suggested a possible reduction of the need for invasive mechanical ventilation compared to COT. The COVID-19 pandemic has resulted in a substantial increase in AHRF worldwide, overwhelming both acute and intensive care unit capacity in most countries. This triggered new trials, adding to the body of evidence on HFNO in AHRF and its possible benefits compared to COT or non-invasive ventilation. We have summarized and discussed this recent evidence to inform the best supportive strategy in AHRF both related and unrelated to COVID-19.

Spontaneous pneumomediastinum: a surrogate of P-SILI in critically ill COVID-19 patients

Spontaneous pneumomediastinum (SP) has been described early during the COVID-19 pandemic in large series of patients with severe pneumonia, but most patients were receiving invasive mechanical ventilation (IMV) at the time of SP diagnosis. In this retrospective multicenter observational study, we aimed at describing the prevalence and outcomes of SP during severe COVID-19 with pneumonia before any IMV, to rule out mechanisms induced by IMV in the development of pneumomediastinum.Among 549 patients, 21 patients (4%) developed a SP while receiving non-invasive respiratory support, after a median of 6 days [4-12] from ICU admission. The proportion of patients requiring IMV was similar. However, the time to tracheal intubation was longer in patients with SP (6 days [5-13] vs. 2 days [1-4]; P = 0.00002), with a higher first-line use of non-invasive ventilation (n = 11; 52% vs. n = 150; 28%; P = 0.02). The 21 patients who developed a SP had persisting signs of severe lung disease and respiratory failure with lower ROX index between ICU admission and occurrence of SP (3.94 [3.15-5.55] at admission vs. 3.25 [2.73-4.02] the day preceding SP; P = 0.1), which may underline potential indirect signals of Patient-self inflicted lung injury (P-SILI).In this series of critically ill COVID-19 patients, the prevalence of SP without IMV was not uncommon, affecting 4% of patients. They received more often vasopressors and had a longer ICU length of stay, as compared with their counterparts. One pathophysiological mechanism may potentially be carried out by P-SILI related to a prolonged respiratory failure, as underlined by a delayed use of IMV and the evolution of the ROX index between ICU admission and the day preceding SP.

Non-invasive ventilation for acute hypoxemic respiratory failure, including COVID-19

Optimal initial non-invasive management of acute hypoxemic respiratory failure (AHRF), of both coronavirus disease 2019 (COVID-19) and non-COVID-19 etiologies, has been the subject of significant discussion. Avoidance of endotracheal intubation reduces related complications, but maintenance of spontaneous breathing with intense respiratory effort may increase risks of patients' self-inflicted lung injury, leading to delayed intubation and worse clinical outcomes. High-flow nasal oxygen is currently recommended as the optimal strategy for AHRF management for its simplicity and beneficial physiological effects. Non-invasive ventilation (NIV), delivered as either pressure support or continuous positive airway pressure via interfaces like face masks and helmets, can improve oxygenation and may be associated with reduced endotracheal intubation rates. However, treatment failure is common and associated with poor outcomes. Expertise and knowledge of the specific features of each interface are necessary to fully exploit their potential benefits and minimize risks. Strict clinical and physiological monitoring is necessary during any treatment to avoid delays in endotracheal intubation and protective ventilation. In this narrative review, we analyze the physiological benefits and risks of spontaneous breathing in AHRF, and the characteristics of tools for delivering NIV. The goal herein is to provide a contemporary, evidence-based overview of this highly relevant topic.

Helmet noninvasive support for acute hypoxemic respiratory failure: rationale, mechanism of action and bedside application

Introduction

Helmet noninvasive support may provide advantages over other noninvasive oxygenation strategies in the management of acute hypoxemic respiratory failure. In this narrative review based on a systematic search of the literature, we summarize the rationale, mechanism of action and technicalities for helmet support in hypoxemic patients.

Main results

In hypoxemic patients, helmet can facilitate noninvasive application of continuous positive-airway pressure or pressure-support ventilation via a hood interface that seals at the neck and is secured by straps under the arms. Helmet use requires specific settings. Continuous positive-airway pressure is delivered through a high-flow generator or a Venturi system connected to the inspiratory port of the interface, and a positive end-expiratory pressure valve place at the expiratory port of the helmet;  alternatively, pressure-support ventilation is delivered by connecting the helmet to a mechanical ventilator through a bi-tube circuit. The helmet interface allows continuous treatments with high positive end-expiratory pressure with good patient comfort. Preliminary data suggest that helmet noninvasive ventilation (NIV) may provide physiological benefits compared to other noninvasive oxygenation strategies (conventional oxygen, facemask NIV, high-flow nasal oxygen) in non-hypercapnic patients with moderate-to-severe hypoxemia (PaO₂/FiO₂ ≤ 200 mmHg), possibly because higher positive end-expiratory pressure (10–15 cmH₂O) can be applied for prolonged periods with good tolerability. This improves oxygenation, limits ventilator inhomogeneities, and may attenuate the potential harm of lung and diaphragm injury caused by vigorous inspiratory effort. The potential superiority of helmet support for reducing the risk of intubation has been hypothesized in small, pilot randomized trials and in a network metanalysis.

Conclusions

Helmet noninvasive support represents a promising tool for the initial management of patients with severe hypoxemic respiratory failure. Currently, the lack of confidence with this and technique and the absence of conclusive data regarding its efficacy render helmet use limited to specific settings, with expert and trained personnel. As per other noninvasive oxygenation strategies, careful clinical and physiological monitoring during the treatment is essential to early identify treatment failure and avoid delays in intubation.

The optimal management of the patient with COVID‐19 pneumonia: HFNC, NIV/CPAP or mechanical ventilation?

The recent pandemic has seen unprecedented demand for respiratory support of patients with COVID‐19 pneumonia, stretching services and clinicians. Yet despite the global numbers of patients treated, guidance is not clear on the correct choice of modality or the timing of escalation of therapy for an individual patient.This narrative review assesses the available literature on the best use of different modalities of respiratory support for an individual patient, and discusses benefits and risks of each, coupled with practical advice to improve outcomes. On current data, in an ideal context, it appears that as disease severity worsens, conventional oxygen therapy is not sufficient alone. In more severe disease, i.e. PaO2/FiO2 ratios below approximately 200, helmet‐CPAP (continuous positive airway pressure) (although not widely available) may be superior to high‐flow nasal cannula (HFNC) therapy or facemask non‐invasive ventilation (NIV)/CPAP, and that facemask NIV/CPAP may be superior to HFNC, but with noted important complications, including risk of pneumothoraces. In an ideal context, invasive mechanical ventilation should not be delayed where indicated and available. Vitally, the choice of respiratory support should not be prescriptive but contextualised to each setting, as supply and demand of resources vary markedly between institutions. Over time, institutions should develop clear policies to guide clinicians before demand exceeds supply, and should frequently review best practice as evidence matures.

Breathing pattern, accessory respiratory muscles work, and gas exchange evaluation for prediction of NIV failure in moderate-to-severe COVID-19-associated ARDS after deterioration of respiratory failure outside ICU: the COVID-NIV observational study

BACKGROUND

Data on the efficacy of non-invasive ventilation (NIV) after progression of respiratory failure in patients who have already received oxygen therapy, or CPAP outside ICU is limited. The study aimed to find predictors of NIV failure based on breathing pattern, gas exchange, and accessory respiratory muscles evaluation in patients who progressed to moderate-to-severe COVID-19 ARDS.

METHODS

This was a prospective observational study in patients with moderate-to-severe COVID-19-ARDS on NIV (n = 80) admitted to COVID-ICU of Sechenov University. The combined success rate for conventional oxygen and CPAP outside ICU was 78.6% (440 of 560 patients). The primary endpoints were intubation rate and mortality. We measured respiratory rate, exhaled tidal volume (Vte), mean peak inspiratory flow (PIF), inspiratory time (Ti), PaO₂, SpO₂, end-tidal carbon dioxide (P_ETCO₂), and Patrick score, and calculated ROX index, PaO₂/FiO₂, ventilatory ratio, and alveolar dead space (Vdalv/Vt) on Days 1, 3, 5, 7, 10, and 14. For all significant differences between NIV success and failure groups in measured data, we performed ROC analysis.

RESULTS

NIV failure rate in ICU after deterioration of respiratory failure outside ICU was 71.3% (n = 57). Patients with the subsequent NIV failure were older at inclusion, more frail, had longer duration of disease before ICU admission, and higher rate of CPAP use outside ICU. ROC-analysis revealed that the following respiratory parameters after 48 h of NIV can serve as a predictors for NIV failure in moderate-to-severe COVID-19-associated ARDS: PaO₂/FiO₂ < 112 mmHg (AUROC 0.90 (0.93-0.97), p < 0.0001); P_ETCO₂ < 19.5 mmHg (AUROC 0.84 (0.73-0.94), p < 0.0001); VDalv/VT > 0.43 (AUROC 0.78 (0.68-0.90), p < 0.0001); ROX-index < 5.02 (AUROC 0.89 (0.81-0.97), p < 0.0001); Patrick score > 2 points (AUROC 0.87 (0.78-0.96), p = 0.006).

CONCLUSION

In patients who progressed to moderate-to-severe COVID-19-ARDS probability of NIV success rate was about 1/3. Prediction of the NIV failure can be made after 48 h based on ROX index < 5.02, PaO₂/FiO₂ < 112 mmHg, P_ETCO2 < 19.5 mmHg, and Patrick score >  = 2.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04667923 , registered on 16/12/2020.

How to recognize patients at risk of self-inflicted lung injury

INTRODUCTION

Patient self-inflicted lung injury (P-SILI) has been proposed as a form of lung injury caused by strong inspiratory efforts consequent to a high respiratory drive in patients with hypoxemic acute respiratory failure (hARF). Increased respiratory drive and effort may lead to variable combinations of deleterious phenomena, such as excessive transpulmonary pressure, pendelluft, intra-tidal recruitment, local lung volutrauma, and pulmonary edema. Gas exchange and respiratory mechanics derangements further increase respiratory drive and effort, thus inducing a vicious circle. Forms of partial ventilatory support may further add to the detrimental effects of P-SILI. Since P-SILI may worsen patient outcome, strategies aimed at identifying and preventing P-SILI would be of great importance.

AREAS COVERED

We systematically searched Pubmed since inception until 15 April 2022 to review the patho-physiological mechanisms of P-SILI and the strategies to identify those patients at risk of P-SILI.

EXPERT OPINION

Although the concept of P-SILI has been increasingly supported by experimental and clinical data, no study has insofar demonstrated the efficacy of any strategy to identify it in the clinical setting. Further research is thus needed to ascertain the detrimental effects of spontaneous breathing and identify patients with hARF at high risk of developing P-SILI.

Application of High-Flow Nasal Cannula in COVID-19: A Narrative Review

Background: During the first wave of COVID-19, the large influx of severely ill patients led to insufficient availability of beds in intensive care units and a shortage of ventilators. The shortage of ventilators, high mortality of intubated patients, and high risk of infections among healthcare workers involved in intubation were the main factors that led to the prevalence of noninvasive respiratory support during the pandemic. The high-flow nasal cannula (HFNC) is a commonly used, popular form of noninvasive respiratory support. Due to its unique physiological effects, HFNC can provide a high fraction of humidified oxygen and is satisfactorily comfortable for patients with COVID-19. However, before the COVID-19 era, there was little evidence on the application of HFNC in patients with acute respiratory failure caused by viral infection. Aim: This narrative review provides an overview of recent studies on the use of HFNC in patients with COVID-19-related acute hypoxemic respiratory failure. The main topics discussed include the probability of successful use of HFNC in these patients, whether late intubation increases mortality, the availability of convenient and accurate monitoring tools, comparison of HFNC with other types of noninvasive respiratory support, whether HFNC combined with the prone position is more clinically useful, and strategies to further reduce the infection risk associated with HFNC. The implication of this study is to identify some of the limitations and research gaps of the current literature and to give some advice for future research.

High-Dose Dexamethasone and Oxygen Support Strategies in Intensive Care Unit Patients With Severe COVID-19 Acute Hypoxemic Respiratory Failure: The COVIDICUS Randomized Clinical Trial

IMPORTANCE

The benefit of high-dose dexamethasone and oxygenation strategies vs standard of care for patients with severe acute hypoxemic respiratory failure (AHRF) caused by COVID-19 pneumonia is debated.

OBJECTIVES

To assess the benefit of high-dose dexamethasone compared with standard of care dexamethasone, and to assess the benefit of high-flow nasal oxygen (HFNo2) or continuous positive airway pressure (CPAP) compared with oxygen support standard of care (o2SC).

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, placebo-controlled randomized clinical trial was conducted in 19 intensive care units (ICUs) in France from April 2020 to January 2021. Eligible patients were consecutive ICU-admitted adults with COVID-19 AHRF. Randomization used a 2 × 3 factorial design for dexamethasone and oxygenation strategies; patients not eligible for at least 1 oxygenation strategy and/or already receiving invasive mechanical ventilation (IMV) were only randomized for dexamethasone. All patients were followed-up for 60 days. Data were analyzed from May 26 to July 31, 2021.

INTERVENTIONS

Patients received standard dexamethasone (dexamethasone-phosphate 6 mg/d for 10 days [or placebo prior to RECOVERY trial results communication]) or high-dose dexamethasone (dexamethasone-phosphate 20 mg/d on days 1-5 then 10 mg/d on days 6-10). Those not requiring IMV were additionally randomized to o2SC, CPAP, or HFNo2.

MAIN OUTCOMES AND MEASURES

The main outcomes were time to all-cause mortality, assessed at day 60, for the dexamethasone interventions, and time to IMV requirement, assessed at day 28, for the oxygenation interventions. Differences between intervention groups were calculated using proportional Cox models and expressed as hazard ratios (HRs).

RESULTS

Among 841 screened patients, 546 patients (median [IQR] age, 67.4 [59.3-73.1] years; 414 [75.8%] men) were randomized between standard dexamethasone (276 patients, including 37 patients who received placebo) or high-dose dexamethasone (270 patients). Of these, 333 patients were randomized among o2SC (109 patients, including 56 receiving standard dexamethasone), CPAP (109 patients, including 57 receiving standard dexamethasone), and HFNo2 (115 patients, including 56 receiving standard dexamethasone). There was no difference in 60-day mortality between standard and high-dose dexamethasone groups (HR, 0.96 [95% CI, 0.69-1.33]; P = .79). There was no significant difference for the cumulative incidence of IMV criteria at day 28 among o2 support groups (o2SC vs CPAP: HR, 1.08 [95% CI, 0.71-1.63]; o2SC vs HFNo2: HR, 1.04 [95% CI, 0.69-1.55]) or 60-day mortality (o2SC vs CPAP: HR, 0.97 [95% CI, 0.58-1.61; o2SC vs HFNo2: HR, 0.89 [95% CI, 0.53-1.47]). Interactions between interventions were not significant.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial among ICU patients with COVID-19-related AHRF, high-dose dexamethasone did not significantly improve 60-day survival. The oxygenation strategies in patients who were not initially receiving IMV did not significantly modify 28-day risk of IMV requirement.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04344730; EudraCT: 2020-001457-43.

Noninvasive Ventilation in Treatment of Respiratory Failure-Related COVID-19 Infection: Review of the Literature

The recently diagnosed coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in December 2019 commonly affects the respiratory system. The incidence of acute hypoxic respiratory failure varied among epidemiological studies with high percentage of patients requiring mechanical ventilation with a high mortality. Noninvasive ventilation is an alternative tool for ventilatory support instead of invasive mechanical ventilation, especially with scarce resources and intensive care beds. Initially, there were concerns by the national societies regarding utilization of noninvasive ventilation in acute respiratory failure. Recent publications reflect the gained experience with the safe utilization of noninvasive mechanical ventilation. Noninvasive ventilation has beneficiary role in treatment of acute hypoxic respiratory failure with proper indications, setting, monitoring, and timely escalation of therapy. Patients should be monitored frequently for signs of improvement or deterioration in the clinical status. Awareness of indications, contraindications, and parameters reflecting either success or failure of noninvasive ventilation in the management of acute respiratory failure secondary to COVID-19 is essential for improvement of outcomes.

Noninvasive Mechanical Ventilation with Average Volume-Assured Pressure Support versus BiPAP S/T in De Novo Hypoxemic Respiratory Failure

Background

Bilevel positive airway pressure in spontaneous/time and average volume-assured pressure support (BiPAP·S/T-AVAPS) could maintain an adequate tidal volume by reducing the patient's inspiratory effort; however, this ventilatory strategy has not been compared with other ventilatory modes, especially the conventional BiPAP S/T mode, when noninvasive mechanical ventilation (NIMV) is used. The primary objective of this study was to determine the rate of success and failure of the use of BiPAP·S/T-AVAPS versus BiPAP·S/T alone in patients with mild-to-moderate "de novo" hypoxemic respiratory failure.

Methods

This was a matched-cohort study. Subjects with mild-to-moderate de novo hypoxemic respiratory failure were divided into two groups according to the ventilatory strategy used. The subjects in the BiPAP·S/T group were paired with those in the BiPAP·S/T-AVAPS group.

Results

A total of 58 subjects were studied. Twenty-nine subjects in the BiPAP·S/T group were paired with 29 subjects in the BiPAP·S/T-AVAPS group. Twenty patients (34.5%) presented with "failure of NIMV," while 38 (65.5%) patients did not. In addition, 13 (22.4%) patients died, while 45 (77.6%) recovered. No differences were found in the percentage of intubation (P=0.44) and mortality (P=0.1).

Conclusion

The BiPAP S/T-AVAPS ventilator mode was not superior to the BiPAP·S/T mode. A high mortality rate was observed in patients with NIMV failure in both modes. This trial is registered with https://doi.org/10.1186/ISRCTN17904857.

Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) occurs in up to 10% of patients with respiratory failure admitted through the emergency department. Use of noninvasive respiratory support has proliferated in recent years; clinicians must understand the relative merits and risks of these technologies and know how to recognize signs of failure. The cornerstone of ARDS care of the mechanically ventilated patient is low-tidal volume ventilation based on ideal body weight. Adjunctive therapies, such as prone positioning and neuromuscular blockade, may have a role in the emergency department management of ARDS depending on patient and department characteristics.

Spontaneous breathing promotes lung injury in an experimental model of alveolar collapse

Vigorous spontaneous breathing has emerged as a promotor of lung damage in acute lung injury, an entity known as “patient self-inflicted lung injury”. Mechanical ventilation may prevent this second injury by decreasing intrathoracic pressure swings and improving regional air distribution. Therefore, we aimed to determine the effects of spontaneous breathing during the early stage of acute respiratory failure on lung injury and determine whether early and late controlled mechanical ventilation may avoid or revert these harmful effects. A model of partial surfactant depletion and lung collapse was induced in eighteen intubated pigs of 32 ±4 kg. Then, animals were randomized to (1) SB‐group: spontaneous breathing with very low levels of pressure support for the whole experiment (eight hours), (2) Early MV-group: controlled mechanical ventilation for eight hours, or (3) Late MV-group: first half of the experiment on spontaneous breathing (four hours) and the second half on controlled mechanical ventilation (four hours). Respiratory, hemodynamic, and electric impedance tomography data were collected. After the protocol, animals were euthanized, and lungs were extracted for histologic tissue analysis and cytokines quantification. SB-group presented larger esophageal pressure swings, progressive hypoxemia, lung injury, and more dorsal and inhomogeneous ventilation compared to the early MV-group. In the late MV-group switch to controlled mechanical ventilation improved the lung inhomogeneity and esophageal pressure swings but failed to prevent hypoxemia and lung injury. In a lung collapse model, spontaneous breathing is associated to large esophageal pressure swings and lung inhomogeneity, resulting in progressive hypoxemia and lung injury. Mechanical ventilation prevents these mechanisms of patient self-inflicted lung injury if applied early, before spontaneous breathing occurs, but not when applied late.

Noninvasive ventilation in COVID-19 patients aged ≥ 70 years-a prospective multicentre cohort study

BACKGROUND

Noninvasive ventilation (NIV) is a promising alternative to invasive mechanical ventilation (IMV) with a particular importance amidst the shortage of intensive care unit (ICU) beds during the COVID-19 pandemic. We aimed to evaluate the use of NIV in Europe and factors associated with outcomes of patients treated with NIV.

METHODS

This is a substudy of COVIP study-an international prospective observational study enrolling patients aged ≥ 70 years with confirmed COVID-19 treated in ICU. We enrolled patients in 156 ICUs across 15 European countries between March 2020 and April 2021.The primary endpoint was 30-day mortality.

RESULTS

Cohort included 3074 patients, most of whom were male (2197/3074, 71.4%) at the mean age of 75.7 years (SD 4.6). NIV frequency was 25.7% and varied from 1.1 to 62.0% between participating countries. Primary NIV failure, defined as need for endotracheal intubation or death within 30 days since ICU admission, occurred in 470/629 (74.7%) of patients. Factors associated with increased NIV failure risk were higher Sequential Organ Failure Assessment (SOFA) score (OR 3.73, 95% CI 2.36-5.90) and Clinical Frailty Scale (CFS) on admission (OR 1.46, 95% CI 1.06-2.00). Patients initially treated with NIV (n = 630) lived for 1.36 fewer days (95% CI - 2.27 to - 0.46 days) compared to primary IMV group (n = 1876).

CONCLUSIONS

Frequency of NIV use varies across European countries. Higher severity of illness and more severe frailty were associated with a risk of NIV failure among critically ill older adults with COVID-19. Primary IMV was associated with better outcomes than primary NIV. Clinical Trial Registration NCT04321265 , registered 19 March 2020, https://clinicaltrials.gov .

An updated HACOR score for predicting the failure of noninvasive ventilation: a multicenter prospective observational study

BACKGROUND

Heart rate, acidosis, consciousness, oxygenation, and respiratory rate (HACOR) have been used to predict noninvasive ventilation (NIV) failure. However, the HACOR score fails to consider baseline data. Here, we aimed to update the HACOR score to take into account baseline data and test its predictive power for NIV failure primarily after 1-2 h of NIV.

METHODS

A multicenter prospective observational study was performed in 18 hospitals in China and Turkey. Patients who received NIV because of hypoxemic respiratory failure were enrolled. In Chongqing, China, 1451 patients were enrolled in the training cohort. Outside of Chongqing, another 728 patients were enrolled in the external validation cohort.

RESULTS

Before NIV, the presence of pneumonia, cardiogenic pulmonary edema, pulmonary ARDS, immunosuppression, or septic shock and the SOFA score were strongly associated with NIV failure. These six variables as baseline data were added to the original HACOR score. The AUCs for predicting NIV failure were 0.85 (95% CI 0.84-0.87) and 0.78 (0.75-0.81) tested with the updated HACOR score assessed after 1-2 h of NIV in the training and validation cohorts, respectively. A higher AUC was observed when it was tested with the updated HACOR score compared to the original HACOR score in the training cohort (0.85 vs. 0.80, 0.86 vs. 0.81, and 0.85 vs. 0.82 after 1-2, 12, and 24 h of NIV, respectively; all p values < 0.01). Similar results were found in the validation cohort (0.78 vs. 0.71, 0.79 vs. 0.74, and 0.81 vs. 0.76, respectively; all p values < 0.01). When 7, 10.5, and 14 points of the updated HACOR score were used as cutoff values, the probability of NIV failure was 25%, 50%, and 75%, respectively. Among patients with updated HACOR scores of ≤ 7, 7.5-10.5, 11-14, and > 14 after 1-2 h of NIV, the rate of NIV failure was 12.4%, 38.2%, 67.1%, and 83.7%, respectively.

CONCLUSIONS

The updated HACOR score has high predictive power for NIV failure in patients with hypoxemic respiratory failure. It can be used to help in decision-making when NIV is used.

High-flow nasal cannula failure in critically ill cancer patients with acute respiratory failure: Moving from avoiding intubation to avoiding delayed intubation

Background

High-flow nasal cannula (HFNC) is increasingly used in critically ill cancer patients with acute respiratory failure (ARF) to avoid mechanical ventilation (MV). The objective was to assess prognostic factors associated with mortality in ICU cancer patients requiring MV after HFNC failure, and to identify predictive factors of intubation.

Methods

We conducted a retrospective study from 2012–2016 in a cancer referral center. All consecutive onco-hematology adult patients admitted to the ICU treated with HFNC were included. HFNC failure was defined by intubation requirement.

Results

202 patients were included, 104 successfully treated with HFNC and 98 requiring intubation. ICU and hospital mortality rates were 26.2% (n = 53) and 42.1% (n = 85) respectively, and 53.1% (n = 52) and 68.4% (n = 67) in patients requiring MV. Multivariate analysis identified 4 prognostic factors of hospital mortality after HFNC failure: complete/partial remission (OR = 0.2, 95%CI = 0.04–0.98, p<0.001) compared to patients with refractory/relapse disease (OR = 3.73, 95%CI = 1.08–12.86), intubation after day 3 (OR = 7.78, 95%CI = 1.44–41.96), number of pulmonary quadrants involved on chest X-ray (OR = 1.93, 95%CI = 1.14–3.26, p = 0.01) and SAPSII at ICU admission (OR = 1.06, 95%CI = 1–1.12, p = 0.019). Predictive factors of intubation were the absence of sepsis (sHR = 0.32, 95%CI = 0.12–0.74, p = 0.0087), Sp02<95% 15 minutes after HFNC initiation (sHR = 2.05, 95%CI = 1.32–3.18, p = 0.0014), number of quadrants on X-ray (sHR = 1.73, 95%CI = 1.46–2.06, p<0.001), Fi02>60% at HFNC initiation (sHR = 3.12, 95%CI = 2.06–4.74, p<0.001) and SAPSII at ICU admission (sHR = 1.03, 95%CI = 1.02–1.05, p<0.01).

Conclusion

Duration of HFNC may be predictive of an excess mortality in ARF cancer patients. Early warning scores to predict HFNC failure are needed to identify patients who would benefit from early intubation.

Insights Regarding the Berlin Definition of ARDS from Prospective Observational Studies

The definition of acute respiratory distress syndrome (ARDS), has evolved since it was first described in 1967 by Ashbaugh and Petty to the current "Berlin" definition of ARDS developed in 2012 by an expert panel, that provided clarification on the definition of "acute," and on the cardiac failure criteria. It expanded the definition to include patients receiving non-invasive ventilation, and removed the term "acute lung injury" and added a requirement of patients to be receiving a minimum 5 cmH₂O expiratory pressure.Since 2012, a series of observational cohort studies have generated insights into the utility and robustness of this definition. This review will examine novel insights into the epidemiology of ARDS, failures in ARDS diagnosis, the role of lung imaging in ARDS, the novel ARDS cohort that is not invasively ventilated, lung compliance profiles in patients with ARDS, sex differences that exist in ARDS management and outcomes, the progression of ARDS following initial diagnosis, and the clinical profile and outcomes of confirmed versus resolved ARDS. Furthermore, we will discuss studies that challenge the utility of distinguishing ARDS from other causes of acute hypoxemic respiratory failure (AHRF) and identify issues that may need to be addressed in a revised definition.

SIMEU position paper on non-invasive respiratory support in COVID-19 pneumonia

The rapid worldwide spread of the Coronavirus disease (COVID-19) crisis has put health systems under pressure to a level never experienced before, putting intensive care units in a position to fail to meet an exponentially growing demand. The main clinical feature of the disease is a progressive arterial hypoxemia which rapidly leads to ARDS which makes the use of intensive care and mechanical ventilation almost inevitable. The difficulty of health systems to guarantee a corresponding supply of resources in intensive care, together with the uncertain results reported in the literature with respect to patients who undergo early conventional ventilation, make the search for alternative methods of oxygenation and ventilation and potentially preventive of the need for tracheal intubation, such as non-invasive respiratory support techniques particularly valuable. In this context, the Emergency Department, located between the area outside the hospital and hospital ward and ICU, assumes the role of a crucial junction, due to the possibility of applying these techniques at a sufficiently early stage and being able to rapidly evaluate their effectiveness. This position paper describes the indications for the use of non-invasive respiratory support techniques in respiratory failure secondary to COVID-19-related pneumonia, formulated by the Non-invasive Ventilation Faculty of the Italian Society of Emergency Medicine (SIMEU) on the base of what is available in the literature and on the authors' direct experience. Rationale, literature, tips & tricks, resources, risks and expected results, and patient interaction will be discussed for each one of the escalating non-invasive respiratory techniques: standard oxygen, HFNCO, CPAP, NIPPV, and awake self-repositioning. The final chapter describes our suggested approach to the failing patient.

Risk Stratification in Noninvasive Respiratory Support Failure: A Narrative Review

TOPIC/CLINICAL RELEVANCE

The use of noninvasive respiratory support, including noninvasive ventilation and high-flow nasal cannula therapy, has increased over the years. Failure of noninvasive respiratory support, defined as the need for invasive mechanical ventilation, increases the mortality rate.

PURPOSE

To familiarize critical care nurses with available risk stratification assessments and identify common concepts and limitations.

CONTENT COVERED

Few risk stratification assessments are available to identify patients at risk of failure of noninvasive respiratory support. Although many studies have analyzed risk, substantial variation in study design, definitions, terminology, and outcomes have led to a wide range of findings, making clinical application difficult. Further study is needed to broaden known assessments to general patient populations, determine diagnostic accuracy during critical periods, and analyze noninvasive ventilation and high-flow nasal cannula therapy. Risk stratification could allow for better implementation of preventive strategies and patient education.

CONCLUSION

Future research opportunities include improving study design for risk stratification and implementing preventive strategies for patients requiring noninvasive respiratory support. Clinically, risk stratification can provide an opportunity to share knowledge and facilitate conversations with patients and families.

Feasibility of non-invasive respiratory drive and breathing pattern evaluation using CPAP in COVID-19 patients

PURPOSE

Increased respiratory drive and respiratory effort are major features of acute hypoxemic respiratory failure (AHRF) and might help to predict the need for intubation. We aimed to explore the feasibility of a non-invasive respiratory drive evaluation and describe how these parameters may help to predict the need for intubation.

MATERIALS AND METHODS

We conducted a prospective observational study. All consecutive patients with COVID-19-related AHRF requiring high-flow nasal cannula (HFNC) were screened for inclusion. Physiologic data (including: occlusion pressure (P0.1), tidal volume (Vt), inspiratory time (Ti), peak and mean inspiratory flow (Vt/Ti)) were collected during a short continuous positive airway pressure (CPAP) session. Measurements were repeated once, 12-24 h later.

RESULTS

Measurements were completed in 31 patients after the screening of 45 patients (70%). P0.1 was high (4.4 [2.7-5.1]), but it was not significantly higher in patients who were intubated. The Vt (p = .006), Vt/Ti (p = .019), minute ventilation (p = .006), and Ti/Ttot (p = .003) were higher among intubated patients compared to non-intubated patients. Intubated patients had a significant increase in their diaphragm thickening fraction, Vt, and Vt/Ti over time.

CONCLUSIONS

Non-invasive assessment of respiratory drive was feasible in patients with AHRF and showed an increased P0.1, although it was not predictive of intubation.

Non-invasive ventilation for acute hypoxaemic respiratory failure: a propensity-matched cohort study

Background

Non-invasive ventilation (NIV), although effective in treating hypercapnic respiratory failure, has not demonstrated the same efficacy in treating acute hypoxaemic respiratory failure. We aimed to examine the effect of NIV use on ventilator-free days in patients with acute hypoxaemic respiratory failure admitted to the intensive care unit (ICU).

Methods

We conducted a retrospective study of patients admitted to the ICU with acute hypoxaemic respiratory failure at Waikato Hospital, New Zealand, from 1 January 2009 to 31 December 2018. Patients treated with NIV as the initial oxygenation strategy were compared with controls treated with early intubation. The two groups were matched using a propensity score based on baseline characteristics. The primary outcome was the number of ventilator-free days at day 28. The secondary outcomes were ICU and hospital length of stay and in-hospital mortality.

Results

Out of 175 eligible patients, 79 each out of the NIV and early intubation groups were matched using a propensity score. Early NIV was associated with significantly higher median ventilator-free days than early intubation (17 days vs 23 days, p=0.013). There was no significant difference in median ICU length of stay (112.5 hours vs 117.7 hours), hospital length of stay (14 days vs 14 days) or in-hospital mortality (31.6% vs 37.9%) between the NIV and the early intubation group.

Conclusion

Compared with early intubation, NIV use was associated with more ventilator-free days in patients with hypoxaemic respiratory failure. However, this did not translate into a shorter length of stay or reduced mortality based on our single-centre experience.

High flow nasal cannula oxygen therapy: P-SILI or not P-SILI?

We would like to thank A.S. Saini and co-workers for their interest and their valuable and constructive comments concerning our study [1]. We have shown that, assessed by pulmonary electrical impedance tomography (EIT), high-flow nasal cannula (HFNC) oxygen therapy and noninvasive ventilation (NIV) could generate comparable alveolar recruitment, but NIV generated larger lung volumes. This increase in lung volumes with NIV could be involved in alveolar lesions worsening, induced by the patient's spontaneous ventilation or “patient self-inflicted lung injury” (P-SILI) [2]. However, A.S. Saini and co-workers argue that HFNC could also generate P-SILI and describe the main pathophysiological determinants involved in this deleterious effect. If one can accept this potential risk with HFNC and share the arguments proposed by A.S. Saini and co-workers concerning its mechanisms, we nevertheless wish to make a few additional comments.

The risk of P-SILI with HFNC is controversial and may be less than with NIV. Some physiological mechanisms of the protective effect of HFNC are hypoxaemia correction, reduction of inspiratory efforts and homogeneity of lung volume distribution.https://bit.ly/3skOEKX

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).

Early prolonged prone position in noninvasively ventilated patients with SARS-CoV-2-related moderate-to-severe hypoxemic respiratory failure: clinical outcomes and mechanisms for treatment response in the PRO-NIV study

Background

Whether prone position (PP) improves clinical outcomes in COVID-19 pneumonia treated with noninvasive ventilation (NIV) is unknown. We evaluated the effect of early PP on 28-day NIV failure, intubation and death in noninvasively ventilated patients with moderate-to-severe acute hypoxemic respiratory failure due to COVID-19 pneumonia and explored physiological mechanisms underlying treatment response.

Methods

In this controlled non-randomized trial, 81 consecutive prospectively enrolled patients with COVID-19 pneumonia and moderate-to-severe (paO2/FiO2 ratio < 200) acute hypoxemic respiratory failure treated with early PP + NIV during Dec 2020–May 2021were compared with 162 consecutive patients with COVID-19 pneumonia matched for age, mortality risk, severity of illness and paO2/FiO2 ratio at admission, treated with conventional (supine) NIV during Apr 2020–Dec 2020 at HUMANITAS Gradenigo Subintensive Care Unit, after propensity score adjustment for multiple baseline and treatment-related variables to limit confounding. Lung ultrasonography (LUS) was performed at baseline and at day 5. Ventilatory parameters, physiological dead space indices (DSIs) and circulating inflammatory and procoagulative biomarkers were monitored during the initial 7 days.

Results

In the intention-to-treat analysis. NIV failure occurred in 14 (17%) of PP patients versus 70 (43%) of controls [HR = 0.32, 95% CI 0.21–0.50; p < 0.0001]; intubation in 8 (11%) of PP patients versus 44 (30%) of controls [HR = 0.31, 95% CI 0.18–0.55; p = 0.0012], death in 10 (12%) of PP patients versus 59 (36%) of controls [HR = 0.27, 95% CI 0.17–0.44; p < 0.0001]. The effect remained significant within different categories of severity of hypoxemia (paO2/FiO2 < 100 or paO2/FiO2 100–199 at admission). Adverse events were rare and evenly distributed. Compared with controls, PP therapy was associated with improved oxygenation and DSIs, reduced global LUS severity indices largely through enhanced reaeration of dorso-lateral lung regions, and an earlier decline in inflammatory markers and D-dimer. In multivariate analysis, day 1 CO2 response outperformed O2 response as a predictor of LUS changes, NIV failure, intubation and death.

Conclusion

Early prolonged PP is safe and is associated with lower NIV failure, intubation and death rates in noninvasively ventilated patients with COVID-19-related moderate-to-severe hypoxemic respiratory failure. Early dead space reduction and reaeration of dorso-lateral lung regions predicted clinical outcomes in our study population.

Clinical trial registration

ISRCTN23016116. Retrospectively registered on May 1, 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03937-x.

Delayed intubation is associated with mortality in patients with severe COVID-19: A single-centre observational study in Switzerland

Introduction

Switzerland experienced two waves of COVID-19 in 2020, but with a different ICU admission and treatment management strategy. The timing of ICU admission and intubation remains a matter of debate in severe patients. The aim of our study was to describe the characteristics of ICU patients between two subsequent waves of COVID-19 who underwent a different management strategy and to assess whether the timing of intubation was associated with differences in mortality.

Patients and methods

We conducted a prospective observational study of all adult patients with acute respiratory failure due to COVID-19 who required intubation between the 9^th of March 2020 and the 9^th of January 2021 in the intensive care unit (ICU) at Geneva University Hospitals, Switzerland.

Results

Two hundred twenty-three patients were intubated during the study period; 124 during the first wave, and 99 during the second wave. Patients admitted to the ICU during the second wave had a higher SAPS II severity score (52.5 vs. 60; p = 0.01). The time from hospital admission to intubation was significantly longer during the second compared to the first wave (4 days [IQR, 1-7] vs. 2 days [IQR, 0-4]; p < 0.01). All-cause ICU mortality was significantly higher during the second wave (42% vs. 23%; p < 0.01). In a multivariate analysis, the delay between hospital admission and intubation was significantly associated with ICU mortality (OR 3.25 [95% CI, 1.38-7.67]; p < 0.05).

Conclusions

In this observational study, delayed intubation was associated with increased mortality in patients with severe COVID-19. Further randomised controlled trials are needed.

Higher mortality and intubation rate in COVID-19 patients treated with noninvasive ventilation compared with high-flow oxygen or CPAP

The effectiveness of noninvasive respiratory support in severe COVID-19 patients is still controversial. We aimed to compare the outcome of patients with COVID-19 pneumonia and hypoxemic respiratory failure treated with high-flow oxygen administered via nasal cannula (HFNC), continuous positive airway pressure (CPAP) or noninvasive ventilation (NIV), initiated outside the intensive care unit (ICU) in 10 university hospitals in Catalonia, Spain. We recruited 367 consecutive patients aged ≥ 18 years who were treated with HFNC (155, 42.2%), CPAP (133, 36.2%) or NIV (79, 21.5%). The main outcome was intubation or death at 28 days after respiratory support initiation. After adjusting for relevant covariates and taking patients treated with HFNC as reference, treatment with NIV showed a higher risk of intubation or death (hazard ratio 2.01; 95% confidence interval 1.32–3.08), while treatment with CPAP did not show differences (0.97; 0.63–1.50). In the context of the pandemic and outside the intensive care unit setting, noninvasive ventilation for the treatment of moderate to severe hypoxemic acute respiratory failure secondary to COVID-19 resulted in higher mortality or intubation rate at 28 days than high-flow oxygen or CPAP. This finding may help physicians to choose the best noninvasive respiratory support treatment in these patients.

Clinicaltrials.gov identifier: NCT04668196.

Mechanical Ventilation for COVID-19 Patients

Non-invasive ventilation (NIV) or invasive mechanical ventilation (MV) is frequently needed in patients with acute hypoxemic respiratory failure due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. While NIV can be delivered in hospital wards and nonintensive care environments, intubated patients require intensive care unit (ICU) admission and support. Thus, the lack of ICU beds generated by the pandemic has often forced the use of NIV in severely hypoxemic patients treated outside the ICU. In this context, awake prone positioning has been widely adopted to ameliorate oxygenation during noninvasive respiratory support. Still, the incidence of NIV failure and the role of patient self-induced lung injury on hospital outcomes of COVID-19 subjects need to be elucidated. On the other hand, endotracheal intubation is indicated when gas exchange deterioration, muscular exhaustion, and/or neurological impairment ensue. Yet, the best timing for intubation in COVID-19 is still widely debated, as it is the safest use of neuromuscular blocking agents. Not differently from other types of acute respiratory distress syndrome, the aim of MV during COVID-19 is to provide adequate gas exchange while avoiding ventilator-induced lung injury. At the same time, the use of rescue therapies is advocated when standard care is unable to guarantee sufficient organ support. Nevertheless, the general shortage of health care resources experienced during SARS-CoV-2 pandemic might affect the utilization of high-cost, highly specialized, and long-term supports. In this article, we describe the state-of-the-art of NIV and MV setting and their usage for acute hypoxemic respiratory failure of COVID-19 patients.

Noninvasive Oxygenation in Patients with Acute Respiratory Failure: Current Perspectives

Purpose of Review

High-flow nasal oxygen and noninvasive ventilation are two alternative strategies to standard oxygen in the management of acute respiratory failure.

Discussion

Although high-flow nasal oxygen has gained major popularity in ICUs due to its simplicity of application, good comfort for patients, efficiency in improving oxygenation and promising results in patients with acute hypoxemic respiratory failure, further large clinical trials are needed to confirm its superiority over standard oxygen. Non-invasive ventilation may have deleterious effects, especially in patients exerting strong inspiratory efforts, and no current recommendations support its use in this setting. Protective non-invasive ventilation using higher levels of positive-end expiratory pressure, more prolonged sessions and other interfaces such as the helmet may have beneficial physiological effects leading to it being proposed as alternative to high-flow nasal oxygen in acute hypoxemic respiratory failure. By contrast, non-invasive ventilation is the first-line strategy of oxygenation in patients with acute exacerbation of chronic lung disease, while high-flow nasal oxygen could be an alternative to non-invasive ventilation after partial reversal of respiratory acidosis. Questions remain about the target populations and non-invasive oxygen strategy representing the best alternative to standard oxygen in acute hypoxemic respiratory failure. As concerns acute on-chronic-respiratory failure, the place of high-flow nasal oxygen remains to be evaluated.

[Development of a giant bulla under spontaneous breathing by self-inflicted lung injury in a patient with COVID-19 pneumonia]

The outbreak of SARS-CoV‑2 and the associated COVID-19 pandemic pose major challenges to healthcare systems worldwide. New data on diagnosis, clinical presentation and treatment of the disease are published on a daily basis. This case report describes the fatal course of severe COVID-19 pneumonia in an 81-year-old patient with no previous pulmonary disease who developed a giant bulla during non-invasive high-flow oxygen therapy. Virus-induced diffuse destruction of alveolar tissue or patient self-inflicted lung injury (P-SILI) are discussed as possible pathomechanisms. Future studies must determine whether lung-protective mechanical ventilation with high levels of sedation and paralysis to suppress spontaneous respiratory drive and to reduce transpulmonary pressure can prevent structural lung damage induced both by the virus and P‑SILI in COVID-19 patients with ARDS.

Treatment of acute respiratory failure: noninvasive mechanical ventilation

Background: Noninvasive ventilation (NIV) has been an important strategy to support patients with respiratory failure, while preventing complications assorted with invasive mechanical ventilation. Physicians need to be aware of the various roles of NIV and the challenges encountered in clinical practice.Current Concepts: Traditionally, the application of NIV has been well-known to be associated with reduced mortality in patients with chronic obstructive pulmonary disease (COPD) or acute pulmonary edema and those suffering from acute respiratory failure. However, despite some positive results of NIV treatment in patients with de novo hypoxemic respiratory failure such as acute pneumonia or acute respiratory distress syndrome, NIV failure (or delayed intubation) can have deleterious effects on patients outcomes. Besides, the aggravation of lung injury should also be taken into consideration when applied to patients exhibiting high respiratory drive. Nonetheless, NIV has potential for wide applications in various clinical situations such as facilitation of ventilator weaning, post-operative respiratory failure, or palliative treatment.Discussion and Conclusion: In addition to the strong evidence in patients with acute respiratory failure due to COPD or acute pulmonary edema, the NIV treatment can be potentially used for various clinical conditions. However, compared to European countries, the prevalence of NIV use continues to remain lower in South Korea. Nevertheless, when applied in appropriately selected patients in a timely manner, NIV treatment can be associated with improved patient outcomes.

High flow nasal catheter therapy versus non-invasive positive pressure ventilation in acute respiratory failure (RENOVATE trial): protocol and statistical analysis plan

Background: The best way to offer non-invasive respiratory support across several aetiologies of acute respiratory failure (ARF) is presently unclear. Both high flow nasal catheter (HFNC) therapy and non-invasive positive pressure ventilation (NIPPV) may improve outcomes in critically ill patients by avoiding the need for invasive mechanical ventilation (IMV). Objective: Describe the details of the protocol and statistical analysis plan designed to test whether HFNC therapy is non-inferior or even superior to NIPPV in patients with ARF due to different aetiologies. Methods: RENOVATE is a multicentre adaptive randomised controlled trial that is recruiting patients from adult emergency departments, wards and intensive care units (ICUs). It takes advantage of an adaptive Bayesian framework to assess the effectiveness of HFNC therapy versus NIPPV in four subgroups of ARF (hypoxaemic non-immunocompromised, hypoxaemic immunocompromised, chronic obstructive pulmonary disease exacerbations, and acute cardiogenic pulmonary oedema). The study will report the posterior probabilities of non-inferiority, superiority or futility for the comparison between HFNC therapy and NIPPV. The study assumes neutral priors and the final sample size is not fixed. The final sample size will be determined by a priori determined stopping rules for non-inferiority, superiority and futility for each subgroup or by reaching the maximum of 2000 patients. Outcomes: The primary endpoint is endotracheal intubation or death within 7 days. Secondary outcomes are 28-day and 90-day mortality, and ICU-free and IMV-free days in the first 28 days. Results and conclusions: RENOVATE is designed to provide evidence on whether HFNC therapy improves, compared with NIPPV, important patient-centred outcomes in different aetiologies of ARF. Here, we describe the rationale, design and status of the trial. Trial registration:ClinicalTrials.gov NCT03643939.

Noninvasive Ventilation by Helmet vs Face Mask in COVID-19 Pneumonia: Emerging Evidence and Need of the Hour

Jain P. Noninvasive Ventilation by Helmet vs Face Mask in COVID-19 Pneumonia: Emerging Evidence and Need of the Hour. Indian J Crit Care Med 2022;26(3):256–258.

Endotracheal intubation rate is lower in critically-ill SARS-CoV-2 patients requiring high-flow nasal oxygen receiving additional face-mask noninvasive ventilation: a retrospective bicentric cohort with propensity score analysis

BACKGROUND

SARS-CoV-2 pneumonia is responsible for unprecedented numbers of acute respiratory failure requiring invasive mechanical ventilation (IMV). This work aimed to assess whether adding face-mask noninvasive ventilation (NIV) to high-flow nasal oxygen (HFNO) was associated with a reduced need for endotracheal intubation.

METHODS

This retrospective cohort study was conducted from July 2020 to January 2021 in two tertiary care intensive care units (ICUs) in Paris, France. Patients admitted for laboratory confirmed SARS-CoV-2 infection with acute hypoxemic respiratory failure requiring HFNO with or without NIV were included. The primary outcome was the rate of endotracheal intubation. Secondary outcomes included day-28 mortality, day-28 respiratory support and IMV free days, ICU and hospital length-of-stay. Sensitivity analyses with both propensity score matching and overlap weighting were used.

RESULTS

128 patients were included, 88 (69%) received HFNO alone and 40 (31%) received additional NIV. Additional NIV was associated with a reduced rate of endotracheal intubation in multivariate analysis (53 (60%) vs 15 (38%), HR=0.46 (95%CI, 0.23-0.95), p=0.04). Sensitivity analyses by propensity score matching (HR=0.45 (95%IC, 0.24-0.84), p=0.01) and overlap weighting (HR=0.52 (95% CI, 0.28-0.94), p=0.03) were consistent. Day-28 mortality was 25 (28%) in the HFNO group and 8 (20%) in the NIV group (HR=0.75 (95%CI, 0.15-3.82), p=0.72). NIV was associated with higher IMV free days (20 (0-28) vs 28 (14-28), p=0.015). All sensitivity analyses were consistent regarding secondary outcomes.

CONCLUSION

Need for endotracheal intubation was lower in critically-ill SARS-CoV-2 patients receiving face-mask noninvasive mechanical ventilation in addition to high-flow oxygen therapy.

Effect of Noninvasive Respiratory Strategies on Intubation or Mortality Among Patients With Acute Hypoxemic Respiratory Failure and COVID-19: The RECOVERY-RS Randomized Clinical Trial

IMPORTANCE

Continuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) have been recommended for acute hypoxemic respiratory failure in patients with COVID-19. Uncertainty exists regarding the effectiveness and safety of these noninvasive respiratory strategies.

OBJECTIVE

To determine whether either CPAP or HFNO, compared with conventional oxygen therapy, improves clinical outcomes in hospitalized patients with COVID-19-related acute hypoxemic respiratory failure.

DESIGN, SETTING, AND PARTICIPANTS

A parallel group, adaptive, randomized clinical trial of 1273 hospitalized adults with COVID-19-related acute hypoxemic respiratory failure. The trial was conducted between April 6, 2020, and May 3, 2021, across 48 acute care hospitals in the UK and Jersey. Final follow-up occurred on June 20, 2021.

INTERVENTIONS

Adult patients were randomized to receive CPAP (n = 380), HFNO (n = 418), or conventional oxygen therapy (n = 475).

MAIN OUTCOMES AND MEASURES

The primary outcome was a composite of tracheal intubation or mortality within 30 days.

RESULTS

The trial was stopped prematurely due to declining COVID-19 case numbers in the UK and the end of the funded recruitment period. Of the 1273 randomized patients (mean age, 57.4 [95% CI, 56.7 to 58.1] years; 66% male; 65% White race), primary outcome data were available for 1260. Crossover between interventions occurred in 17.1% of participants (15.3% in the CPAP group, 11.5% in the HFNO group, and 23.6% in the conventional oxygen therapy group). The requirement for tracheal intubation or mortality within 30 days was significantly lower with CPAP (36.3%; 137 of 377 participants) vs conventional oxygen therapy (44.4%; 158 of 356 participants) (absolute difference, -8% [95% CI, -15% to -1%], P = .03), but was not significantly different with HFNO (44.3%; 184 of 415 participants) vs conventional oxygen therapy (45.1%; 166 of 368 participants) (absolute difference, -1% [95% CI, -8% to 6%], P = .83). Adverse events occurred in 34.2% (130/380) of participants in the CPAP group, 20.6% (86/418) in the HFNO group, and 13.9% (66/475) in the conventional oxygen therapy group.

CONCLUSIONS AND RELEVANCE

Among patients with acute hypoxemic respiratory failure due to COVID-19, an initial strategy of CPAP significantly reduced the risk of tracheal intubation or mortality compared with conventional oxygen therapy, but there was no significant difference between an initial strategy of HFNO compared with conventional oxygen therapy. The study may have been underpowered for the comparison of HFNO vs conventional oxygen therapy, and early study termination and crossover among the groups should be considered when interpreting the findings.

TRIAL REGISTRATION

isrctn.org Identifier: ISRCTN16912075.

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.

Noninvasive respiratory support for COVID-19 patients: when, for whom, and how?

The significant mortality rate and prolonged ventilator days associated with invasive mechanical ventilation (IMV) in patients with severe COVID-19 have incited a debate surrounding the use of noninvasive respiratory support (NIRS) (i.e., HFNC, CPAP, NIV) as a potential treatment strategy. Central to this debate is the role of NIRS in preventing intubation in patients with mild respiratory disease and the potential beneficial effects on both patient outcome and resource utilization. However, there remains valid concern that use of NIRS may prolong time to intubation and lung protective ventilation in patients with more advanced disease, thereby worsening respiratory mechanics via self-inflicted lung injury. In addition, the risk of aerosolization with the use of NIRS has the potential to increase healthcare worker (HCW) exposure to the virus. We review the existing literature with a focus on rationale, patient selection and outcomes associated with the use of NIRS in COVID-19 and prior pandemics, as well as in patients with acute respiratory failure due to different etiologies (i.e., COPD, cardiogenic pulmonary edema, etc.) to understand the potential role of NIRS in COVID-19 patients. Based on this analysis we suggest an algorithm for NIRS in COVID-19 patients which includes indications and contraindications for use, monitoring recommendations, systems-based practices to reduce HCW exposure, and predictors of NIRS failure. We also discuss future research priorities for addressing unanswered questions regarding NIRS use in COVID-19 with the goal of improving patient outcomes.