Physiologic effects of noninvasive ventilation during acute lung injury

Noninvasive Respiratory Support in Acute Respiratory Distress Syndrome

Noninvasive respiratory supports have been successfully used as an alternative to endotracheal intubation especially in patients with a milder degree of hypoxemia. In patients with acute respiratory distress syndrome (ARDS), the main goals of noninvasive oxygenation strategies are to improve oxygenation, unload the respiratory muscles, and relieve dyspnea. On the other hand, recent studies have suggested that spontaneous breathing could represent an additional mechanism of lung injury, especially in the more severe forms. The aim of this review is to describe the role of different noninvasive respiratory supports in ARDS, to optimize its use in clinical practice.

Effect of high-flow nasal cannula oxygen versus standard oxygen on mortality in patients with acute hypoxaemic respiratory failure: protocol for a multicentre, randomised controlled trial (SOHO)

INTRODUCTION

First-line oxygenation strategy in patients with acute hypoxaemic respiratory failure consists in standard oxygen or high-flow nasal oxygen therapy. Clinical practice guidelines suggest the use of high-flow nasal oxygen rather than standard oxygen. However, findings remain contradictory with a low level of certainty. We hypothesise that compared with standard oxygen, high-flow nasal oxygen may reduce mortality in patients with acute hypoxaemic respiratory failure.

METHOD AND ANALYSIS

The Standard Oxygen versus High-flow nasal Oxygen-trial is an investigator-initiated, multicentre, open-label, randomised controlled trial comparing high-flow nasal oxygen versus standard oxygen in patients admitted to an intensive care unit (ICU) for acute respiratory failure with moderate-to-severe hypoxaemia. 1110 patients will be randomly assigned to one of the two groups with a ratio of 1:1. The primary outcome is the number of patients who died 28 days after randomisation. Secondary outcomes include comfort, dyspnoea and oxygenation 1 hour after treatment initiation, the number of patients intubated at day 28, mortality in ICU, in hospital and until day 90, and complications during ICU stay.

ETHICS AND DISSEMINATION

The study has been approved by the central Ethics Committee 'Sud Méditerranée III' (2020-07-05) and patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04468126.

Monitoring and modulating respiratory drive in mechanically ventilated patients

PURPOSE OF REVIEW

Respiratory drive is frequently deranged in the ICU, being associated with adverse clinical outcomes. Monitoring and modulating respiratory drive to prevent potentially injurious consequences merits attention. This review gives a general overview of the available monitoring tools and interventions to modulate drive.

RECENT FINDINGS

Airway occlusion pressure (P0.1) is an excellent measure of drive and is displayed on ventilators. Respiratory drive can also be estimated based on the electrical activity of respiratory muscles and measures of respiratory effort; however, high respiratory drive might be present in the context of low effort with neuromuscular weakness. Modulating a deranged drive requires a multifaceted intervention, prioritizing treatment of the underlying cause and adjusting ventilator settings for comfort. Additional tools include changes in PEEP, peak inspiratory flow, fraction of inspired oxygen, and sweep gas flow (in patients receiving extracorporeal life-support). Sedatives and opioids have differential effects on drive according to drug category. Monitoring response to any intervention is warranted and modulating drive should not preclude readiness to wean assessment or delay ventilation liberation.

SUMMARY

Monitoring and modulating respiratory drive are feasible based on physiological principles presented in this review. However, evidence arising from clinical trials will help determine precise thresholds and optimal interventions.

Ventilator performances for non-invasive ventilation: a bench study

INTRODUCTION

A wide range of recent ventilators, dedicated or not, is available for non-invasive ventilation (NIV) in respiratory or intensive care units (ICU). We conducted a bench study to compare their technical performances.

METHODS

Ventilators, including five ICU ventilators with NIV mode on, two dedicated NIV ventilators and one transport ventilator, were evaluated on a test bench for NIV, consisting of a 3D manikin head connected to an ASL 5000 lung model via a non-vented mask. Ventilators were tested according to three simulated lung profiles (normal, obstructive, restrictive), three levels of simulated air leakage (0, 15, 30 L/min), two levels of pressure support (8, 14 cmH2O) and two respiratory rates (15, 25 cycles/min).

RESULTS

The global median Asynchrony Index (AI) was higher with ICU ventilators than with dedicated NIV ventilators (4% (0; 76) vs 0% (0; 15), respectively; p<0.05) and different between all ventilators (p<0.001). The AI was higher with ICU ventilators for the normal and restrictive profiles (p<0.01) and not different between ventilators for the obstructive profile. Auto-triggering represented 43% of all patient-ventilator asynchrony. Triggering delay, cycling delay, inspiratory pressure-time product, pressure rise time and pressure at mask were different between all ventilators (p<0.01). Dedicated NIV ventilators induced a lower pressure-time product than ICU and transport ventilators (p<0.01). There was no difference between ventilators for minute ventilation and peak flow.

CONCLUSION

Despite the integration of NIV algorithms, most recent ICU ventilators appear to be less efficient than dedicated NIV ventilators. Technical performances could change, however, according to the underlying respiratory disease and the level of air leakage.

Oxygen therapy and noninvasive respiratory supports in acute hypoxemic respiratory failure: a narrative review

BACKGROUND

This narrative review was written by an expert panel to the members of the jury to help in the development of clinical practice guidelines on oxygen therapy.

RESULTS

According to the expert panel, acute hypoxemic respiratory failure was defined as PaO2 < 60 mm Hg or SpO2 < 90% on room air, or PaO2/FiO2 ≤ 300 mm Hg. Supplemental oxygen should be administered according to the monitoring of SpO2, with the aim at maintaining SpO2 above 92% and below 98%. Noninvasive respiratory supports are generally reserved for the most hypoxemic patients with the aim of relieving dyspnea. High-flow nasal cannula oxygen (HFNC) seems superior to conventional oxygen therapy (COT) as a means of avoiding intubation and may therefore be should probably be used as a first-line noninvasive respiratory support in patients requiring more than 6 L/min of oxygen or PaO2/FiO2 ≤ 200 mm Hg and a respiratory rate above 25 breaths/minute or clinical signs of respiratory distress, but with no benefits on mortality. Continuous positive airway pressure (CPAP) cannot currently be recommended as a first-line noninvasive respiratory support, since its beneficial effects on intubation remain uncertain. Despite older studies favoring noninvasive ventilation (NIV) over COT, recent clinical trials fail to show beneficial effects with NIV compared to HFNC. Therefore, there is no evidence to support the use of NIV or CPAP as first-line treatment if HFNC is available. Clinical trials do not support the hypothesis that noninvasive respiratory supports may lead to late intubation. The potential benefits of awake prone positioning on the risk of intubation in patients with COVID-19 cannot be extrapolated to patients with another etiology.

CONCLUSIONS

Whereas oxygen supplementation should be initiated for patients with acute hypoxemic respiratory failure defined as PaO2 below 60 mm Hg or SpO2 < 90% on room air, HFNC should be the first-line noninvasive respiratory support in patients with PaO2/FiO2 ≤ 200 mm Hg with increased respiratory rate. Further studies are needed to assess the potential benefits of CPAP, NIV through a helmet and awake prone position in patients with acute hypoxemic respiratory failure not related to COVID-19.

Highlights from the Respiratory Failure and Mechanical Ventilation Conference 2024

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

Noninvasive ventilation on reintubation in patients with obesity and hypoxemic respiratory failure following abdominal surgery: a post hoc analysis of a randomized clinical trial

PURPOSE

Although noninvasive ventilation (NIV) may reduce reintubation in patients with acute hypoxemic respiratory failure following abdominal surgery, this strategy has not been specifically assessed in patients with obesity.

METHODS

We conducted a post hoc analysis of a multicenter randomized controlled trial comparing NIV delivered via facial mask to standard oxygen therapy among patients with obesity and acute hypoxemic respiratory failure within 7 days after abdominal surgery. The primary outcome was reintubation within 7 days. Secondary outcomes were invasive ventilation-free days at day 30, intensive care unit (ICU)-acquired pneumonia and 30-day survival.

RESULTS

Among 293 patients with hypoxemic respiratory failure following abdominal surgery, 76 (26%) patients had obesity and were included in the intention-to-treat analysis. Reintubation rate was significantly lower with NIV (13/42, 31%) than with standard oxygen therapy (19/34, 56%) within 7 days (absolute difference: - 25%, 95% confidence interval (CI) - 49 to - 1%, p = 0.03). NIV was associated with significantly more invasive ventilation-free days compared with standard oxygen therapy (27.1 ± 8.6 vs 22.7 ± 11.1 days; p = 0.02), while fewer patients developed ICU-acquired pneumonia (1/42, 2% vs 6/34, 18%; p = 0.04). The 30-day survival was 98% in the NIV group (41/42) versus 85% in the standard oxygen therapy (p = 0.08). In patients with body mass index (BMI) < 30 kg/m2, no significant difference was observed between NIV (36/105, 34%) and standard oxygen therapy (47/109, 43%, p = 0.03). An interaction test showed no statistically significant difference between the two subsets (BMI ≥ 30 kg/m2 and BMI < 30 kg/m2).

CONCLUSIONS

Among patients with obesity and hypoxemic respiratory failure following abdominal surgery, use of NIV compared with standard oxygen therapy reduced the risk of reintubation within 7 days, contrary to patients without obesity. However, no interaction was found according to the presence of obesity or not, suggesting either a lack of power to conclude in the non-obese subgroup despite existing differences, or that the statistical difference found in the overall sample was driven by a large effect in the obese subsets.

Noninvasive Ventilation Before Intubation and Mortality in Patients Receiving Extracorporeal Membrane Oxygenation for COVID-19: An Analysis of the Extracorporeal Life Support Organization Registry

Bilevel-positive airway pressure (BiPAP) is a noninvasive respiratory support modality which reduces effort in patients with respiratory failure. However, it may increase tidal ventilation and transpulmonary pressure, potentially aggravating lung injury. We aimed to assess if the use of BiPAP before intubation was associated with increased mortality in adult patients with coronavirus disease 2019 (COVID-19) who received venovenous extracorporeal membrane oxygenation (ECMO). We used the Extracorporeal Life Support Organization Registry to analyze adult patients with COVID-19 supported with venovenous ECMO from January 1, 2020, to December 31, 2021. Patients treated with BiPAP were compared with patients who received other modalities of respiratory support or no respiratory support. A total of 9,819 patients from 421 centers were included. A total of 3,882 of them (39.5%) were treated with BiPAP before endotracheal intubation. Patients supported with BiPAP were intubated later (4.3 vs . 3.3 days, p < 0.001) and showed higher unadjusted hospital mortality (51.7% vs. 44.9%, p < 0.001). The use of BiPAP before intubation and time from hospital admission to intubation resulted as independently associated with increased hospital mortality (odds ratio [OR], 1.32 [95% confidence interval {CI}, 1.08-1.61] and 1.03 [1-1.06] per day increase). In ECMO patients with severe acute respiratory failure due to COVID-19, the extended use of BiPAP before intubation should be regarded as a risk factor for mortality.

The latest on positive airway pressure for pediatric obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) is an important and evolving area in the pediatric population, with significant sequelae when not adequately managed. The use of positive airway pressure (PAP) therapy is expanding rapidly and is being prescribed to patients with persistent OSA post adenotonsillectomy as well as those children who are not surgical candidates including those with medical complexity.

AREAS DISCUSSED

This article provides a state-of-the-art review on the diagnosis of pediatric OSA and treatment with positive airway pressure (PAP). The initiation of PAP therapy, pediatric interface considerations, PAP mode selection, administration and potential complications of PAP therapy, factors influencing PAP adherence, the use of remote ventilation machine downloads, considerations surrounding follow-up of patients post PAP initiation and evaluation of weaning off PAP will be reviewed. The literature search was conducted via PubMed, Cochrane Library and Google Scholar databases through to March 2024.

EXPERT OPINION

Further research is required to address barriers to adherence. Further innovation of home monitoring devices for both the diagnosis and assessment of OSA is required, given the limited pediatric sleep medicine resources in several countries worldwide.

Dyspnea is severe and associated with a higher intubation rate in de novo acute hypoxemic respiratory failure

BACKGROUND

Dyspnea is a key symptom of de novo acute hypoxemic respiratory failure. This study explores dyspnea and its association with intubation and mortality in this population.

METHODS

This was a secondary analysis of a multicenter, randomized, controlled trial. Dyspnea was quantified by a visual analog scale (dyspnea-VAS) from zero to 100 mm. Dyspnea was measured in 259 of the 310 patients included. Factors associated with intubation were assessed with a competing risks model taking into account ICU discharge. The Cox model was used to evaluate factors associated with 90-day mortality.

RESULTS

At baseline (randomization in the parent trial), median dyspnea-VAS was 46 (interquartile range, 16-65) mm and was ≥ 40 mm in 146 patients (56%). The intubation rate was 45%. Baseline variables independently associated with intubation were moderate (dyspnea-VAS 40-64 mm) and severe (dyspnea-VAS ≥ 65 mm) dyspnea at baseline (sHR 1.96 and 2.61, p = 0.023), systolic arterial pressure (sHR 2.56, p < 0.001), heart rate (sHR 1.94, p = 0.02) and PaO2/FiO2 (sHR 0.34, p = 0.028). 90-day mortality was 20%. The cumulative probability of survival was lower in patients with baseline dyspnea-VAS ≥ 40 mm (logrank test, p = 0.049). Variables independently associated with mortality were SAPS 2 ≥ 25 (p < 0.001), moderate-to-severe dyspnea at baseline (p = 0.073), PaO2/FiO2 (p = 0.118), and treatment arm (p = 0.046).

CONCLUSIONS

In patients admitted to the ICU for de novo acute hypoxemic respiratory failure, dyspnea is associated with a higher risk of intubation and with a higher mortality.

TRIAL REGISTRATION

clinicaltrials.gov Identifier # NCT01320384.

PaCO2 is nonlinearly associated with NIV failure in patients with hypoxemic respiratory failure

OBJECTIVE

To explore the association between PaCO2 and noninvasive ventilation (NIV) failure in patients with hypoxemic respiratory failure.

METHODS

A retrospective study was performed in a respiratory ICU of a teaching hospital. Patients admitted to ICU between 2011 and 2019 were screened. We enrolled the patients with hypoxemic respiratory failure. However, patients who used NIV due to acute-on-chronic respiratory failure or heart failure were excluded. Data before the use of NIV were collected. Requirement of intubation was defined as NIV failure.

RESULTS

A total of 1029 patients were enrolled in final analysis. The rate of NIV failure was 45% (461/1029). A nonlinear relationship between PaCO2 and NIV failure was found by restricted cubic splines (p = 0.03). The inflection point was 32 mmHg. The rate of NIV failure was 42% (224/535) in patients with PaCO2 >32 mmHg. However, it increased to 48% (237/494) in those with PaCO2 ≤ 32 mmHg. The crude and adjusted hazard ratio (HR) for NIV failure was 1.36 (95%CI:1.13-1.64) and 1.23(1.01-1.49), respectively, if the patients with PaCO2 >32 mmHg were set as reference. In patients with PaCO2 ≤ 32 mmHg, one unit increment of PaCO2 was associated with 5% reduction of NIV failure. However, it did not associate with NIV failure in patients with PaCO2 >32 mmHg.

CONCLUSIONS

PaCO2 and NIV failure was nonlinear relationship. The inflection point was 32 mmHg. Below the inflection point, lower PaCO2 was associated with higher NIV failure. However, it did not associate with NIV failure above this point.

Multidisciplinary Consensus on the Management of Non-Invasive Respiratory Support in the COVID-19 Patient

Acute respiratory failure due to COVID-19 pneumonia often requires a comprehensive approach that includes non-pharmacological strategies such as non-invasive support (including positive pressure modes, high flow therapy or awake proning) in addition to oxygen therapy, with the primary goal of avoiding endotracheal intubation. Clinical issues such as determining the optimal time to initiate non-invasive support, choosing the most appropriate modality (based not only on the acute clinical picture but also on comorbidities), establishing criteria for recognition of treatment failure and strategies to follow in this setting (including palliative care), or implementing de-escalation procedures when improvement occurs are of paramount importance in the ongoing management of severe COVID-19 cases. Organizational issues, such as the most appropriate setting for management and monitoring of the severe COVID-19 patient or protective measures to prevent virus spread to healthcare workers in the presence of aerosol-generating procedures, should also be considered. While many early clinical guidelines during the pandemic were based on previous experience with acute respiratory distress syndrome, the landscape has evolved since then. Today, we have a wealth of high-quality studies that support evidence-based recommendations to address these complex issues. This document, the result of a collaborative effort between four leading scientific societies (SEDAR, SEMES, SEMICYUC, SEPAR), draws on the experience of 25 experts in the field to synthesize knowledge to address pertinent clinical questions and refine the approach to patient care in the face of the challenges posed by severe COVID-19 infection.

[Non-invasive ventilation in acute respiratory failure of oncology-hematology patients: What are its current benefits and limitations?]

Acute respiratory failure (ARF) is a leading cause, along with sepsis, of admission to the intensive care unit (ICU) of patients with active cancer. Presenting variable clinical severity, ARF in onco-hematological patients has differing etiologies, primarily represented by possibly opportunistic acute infectious pneumonia (de novo hypoxemic ARF), and decompensation in chronic cardiac or respiratory diseases (e.g., acute pulmonary edema or exacerbated chronic obstructive pulmonary disease). In these patients, orotracheal intubation is associated with a doubled risk of in-hospital mortality. Consequently, over the last three decades, numerous researchers have attempted to demonstrate and pinpoint the precise role of non-invasive ventilation (NIV) in the specific context of ARF in onco-hematological patients. While the benefits of NIV in the management of acute pulmonary edema or alveolar hypoventilation (hypercapnic ARF) are well-demonstrated, its positioning in de novo hypoxemic ARF is debatable, and has recently been called into question. In the early 2000s, based on randomized controlled trials, NIV was recommended as first-line treatment, one reason being that it allowed significantly reduced use of orotracheal intubation. In the latest randomized studies, however, the benefits of NIV in terms of survival orotracheal intubation have not been observed; as a result, it is no longer recommended in the management of de novo hypoxemic ARF in onco-haematological patients.

Longitudinal Assessment of ROX and HACOR Scores to Predict Non-Invasive Ventilation Failure in Patients with SARS-CoV-2 Pneumonia

Introduction

NIV (Non-invasive ventilation) and HFNC (High Flow nasal cannula) are being used in patients with acute respiratory failure. HACOR score has been exclusively calculated for patients on NIV, on other hand ROX index is being used for patients on HFNC. This is first study where ROX index has been used in patients on NIV to predict failure.

Aim of the study

This study investigates the comparative diagnostic performance of HACOR score and ROX index to predict NIV failure.

Methods

We performed a retrospective cohort study of non-invasively ventilated COVID-19 patients admitted between 1st April 2020 to 15th June 2021 to ICU of a tertiary care teaching hospital located in Central India. We assessed factors responsible for NIV failure, and whether these scores HACOR/ROX index have discriminative capacity to predict risk of invasive mechanical ventilation.

Results

Of the 441 patients included in the current study, 179 (40.5%) recovered, while remaining 262 (59.4%) had NIV failure. On multivariable analysis, ROX index > 4.47 was found protective for NIV-failure (OR 0.15 (95% CI 0.03-0.23; p<0.001). Age > 60 years and SOFA score were other significant independent predictors of NIV-failure. The AUC for prediction of failure rises from 0.84 to 0.94 from day 1 to day 3 for ROX index and from 0.79 to 0.92 for HACOR score in the same period, hence ROX score was non-inferior to HACOR score in current study. DeLong's test for two correlated ROC curves had insignificant difference expect day-1 (D1: 0.03 to 0.08; p=3.191e-05, D2: -0.002 to 0.02; p = 0.2671, D3: -0.003 to 0.04; p= 0.1065).

Conclusion

ROX score of 4.47 at day-3 consists of good discriminatory capacity to predict NIV failure. Considering its non-inferiority to HACOR score, the ROX score can be used in patients with acute respiratory failure who are on NIV.

Severe Community-Acquired Pneumonia: Noninvasive Mechanical Ventilation, Intubation, and HFNT

Severe acute respiratory failure (ARF) is a major issue in patients with severe community-acquired pneumonia (CAP). Standard oxygen therapy is the first-line therapy for ARF in the less severe cases. However, respiratory supports may be delivered in more severe clinical condition. In cases with life-threatening ARF, invasive mechanical ventilation (IMV) will be required. Noninvasive strategies such as high-flow nasal therapy (HFNT) or noninvasive ventilation (NIV) by either face mask or helmet might cover the gap between standard oxygen and IMV. The objective of all the supporting measures for ARF is to gain time for the antimicrobial treatment to cure the pneumonia. There is uncertainty regarding which patients with severe CAP are most likely to benefit from each noninvasive support strategy. HFNT may be the first-line approach in the majority of patients. While NIV may be relatively contraindicated in patients with excessive secretions, facial hair/structure resulting in air leaks or poor compliance, NIV may be preferable in those with increased work of breathing, respiratory muscle fatigue, and congestive heart failure, in which the positive pressure of NIV may positively impact hemodynamics. A trial of NIV might be considered for select patients with hypoxemic ARF if there are no contraindications, with close monitoring by an experienced clinical team who can intubate patients promptly if they deteriorate. In such cases, individual clinician judgement is key to choose NIV, interface, and settings. Due to the paucity of studies addressing IMV in this population, the protective mechanical ventilation strategies recommended by guidelines for acute respiratory distress syndrome can be reasonably applied in patients with severe CAP.

Prognostic analysis of high-flow nasal cannula therapy and non-invasive ventilation in mild to moderate hypoxemia patients and construction of a machine learning model for 48-h intubation prediction-a retrospective analysis of the MIMIC database

Background

This study aims to investigate the clinical outcome between high-flow nasal cannula (HFNC) and non-invasive ventilation (NIV) therapy in mild to moderate hypoxemic patients on the first ICU day and to develop a predictive model of 48-h intubation.

Methods

The study included adult patients from the MIMIC III and IV databases who first initiated HFNC or NIV therapy due to mild to moderate hypoxemia (100 < PaO2/FiO2 ≤ 300). The 48-h and 30-day intubation rates were compared using cross-sectional and survival analysis. Nine machine learning and six ensemble algorithms were deployed to construct the 48-h intubation predictive models, of which the optimal model was determined by its prediction accuracy. The top 10 risk and protective factors were identified using the Shapley interpretation algorithm.

Result

A total of 123,042 patients were screened, of which, 673 were from the MIMIC IV database for ventilation therapy comparison (HFNC n = 363, NIV n = 310) and 48-h intubation predictive model construction (training dataset n = 471, internal validation set n = 202) and 408 were from the MIMIC III database for external validation. The NIV group had a lower intubation rate (23.1% vs. 16.1%, p = 0.001), ICU 28-day mortality (18.5% vs. 11.6%, p = 0.014), and in-hospital mortality (19.6% vs. 11.9%, p = 0.007) compared to the HFNC group. Survival analysis showed that the total and 48-h intubation rates were not significantly different. The ensemble AdaBoost decision tree model (internal and external validation set AUROC 0.878, 0.726) had the best predictive accuracy performance. The model Shapley algorithm showed Sequential Organ Failure Assessment (SOFA), acute physiology scores (APSIII), the minimum and maximum lactate value as risk factors for early failure and age, the maximum PaCO2 and PH value, Glasgow Coma Scale (GCS), the minimum PaO2/FiO2 ratio, and PaO2 value as protective factors.

Conclusion

NIV was associated with lower intubation rate and ICU 28-day and in-hospital mortality. Further survival analysis reinforced that the effect of NIV on the intubation rate might partly be attributed to the other impact factors. The ensemble AdaBoost decision tree model may assist clinicians in making clinical decisions, and early organ function support to improve patients' SOFA, APSIII, GCS, PaCO2, PaO2, PH, PaO2/FiO2 ratio, and lactate values can reduce the early failure rate and improve patient prognosis.

Incidence of noninvasive ventilation failure and mortality in patients with acute respiratory distress syndrome: a systematic review and proportion meta-analysis

BACKGROUND

Noninvasive ventilation (NIV) is commonly used in patients with acute respiratory distress syndrome (ARDS). However, the incidence and distribution of treatment failure are unclear.

METHODS

A comprehensive online search was conducted to select potentially eligible studies with reports of the rate of NIV failure in patients with ARDS. A manual search was also performed to identify additional studies. Data were extracted to calculate the pooled incidences of NIV failure and mortality. Based on oxygenation, the severity of the disease was classified as mild, moderate, or severe ARDS. Based on etiologies, ARDS was defined as being of pulmonary origin or extrapulmonary origin.

RESULTS

We enrolled 90 studies in this meta-analysis, involving 98 study arms. The pooled incidence of NIV failure was 48% (n = 5847, 95% confidence interval [CI]: 43-52%). The pooled incidence of ICU mortality was 29% (n = 2363, 95%CI: 22-36%), and that of hospital mortality was 33% (n = 2927, 95%CI: 27-40%). In patients with mild, moderate, and severe ARDS, the pooled incidence of NIV failure was 30% (n = 819, 95%CI: 21-39%), 51% (n = 1332, 95%CI: 43-60%), and 71% (n = 525, 95%CI: 62-79%), respectively. In patients with pulmonary ARDS, it was 45% (n = 2687, 95%CI: 39-51%). However, it was 30% (n = 802, 95%CI: 21-38%) in those with extrapulmonary ARDS. In patients with immunosuppression, the incidence of NIV failure was 62% (n = 806, 95%CI: 50-74%). However, it was 46% (n = 5041, 95%CI: 41-50%) in those without immunosuppression.

CONCLUSIONS

Nearly half of patients with ARDS experience NIV failure. The incidence of NIV failure increases with increasing ARDS severity. Pulmonary ARDS seems to have a higher rate of NIV failure than extrapulmonary ARDS. ARDS patients with immunosuppression have the highest rate of NIV failure.

Continuous positive airway pressure or high-flow nasal cannula oxygen therapy for acute hypoxemic respiratory failure unrelated to COVID-19: Another brick in the wall?

See related article

Influence of different noninvasive oxygenation support devices on tidal volume

BACKGROUND

Multiple devices are available for noninvasive oxygenation support, including non-rebreather oxygen mask (O2-mask), high-flow oxygen through nasal cannula (HFNC), continuous positive airway pressure (CPAP), mask noninvasive ventilation (Mask-NIV) and helmet NIV (Helmet-NIV). As tidal volume is a key determinant of efficacy and safety during ventilatory support, we assessed whether it was influenced by the type of noninvasive oxygenation device.

METHODS

A bench study using a manikin with a realistic face connected to a lung simulator was performed. Six conditions were assessed: no device, O2-mask, HFNC, CPAP, Mask-NIV and Helmet-NIV. Three respiratory mechanics were simulated (normal, obstructive, restrictive), at three simulated efforts (low, moderate, respiratory distress). Flow was recorded at the lung simulator inlet and mouth pressure into the manikin mouth. The same devices were evaluated on healthy volunteers with tidal volume assessed by electrical impedance tomography (EIT).

RESULTS

Tidal volume was significantly influenced by oxygenation devices in bench model. As compared to O2-mask, HFNC and CPAP delivered significantly lower tidal volumes (440 ± 352 mL, 414 ± 333 mL and 377 ± 297 mL, respectively), while Mask-NIV or Helmet-NIV were associated with significantly higher tidal volumes (690 ± 321 mL and 652 ± 366 mL, respectively). Tidal volume was strongly correlated with the specific effect of each device on mouth pressure during inspiration: HFNC and CPAP were characterized by a negative PTPmouth (- 0.3 [- 0.8 to - 0.2] and - 0.7 [- 2.2 to - 0.5] cmH2O.sec/cycle, respectively), while Helmet-NIV and Mask-NIV were associated with a positive PTPmouth (4.5 [4.1-4.6] and 6.1 [5.9-7.1] cmH2O.sec/cycle, respectively). Tidal volume was also significantly influenced by oxygenation devices in healthy volunteers, with similar tidal volumes between O2-mask and CPAP (644 [571-764] and 648 [586-770] mL) but higher with HFNC, Mask-NIV and Helmet-NIV (819 [609-918], 1110 [661-1305] and 1086 [833-1243] mL).

CONCLUSIONS

Tidal volume is significantly influenced by noninvasive oxygenation support devices, with a strong correlation with the pressure variation generated into the mouth during inspiration. NIV was associated with the highest tidal volumes and CPAP with the lowest ones. Clinical studies are needed to clarify the clinical implications of these effects.

Effect of noninvasive respiratory support on interstitial lung disease with acute respiratory failure: A systematic review and meta-analysis

Background

Primary studies have demonstrated the effectiveness of noninvasive respiratory supports, including noninvasive positive pressure ventilation (NIPPV) and high flow nasal cannula (HFNC), for improving oxygenation and ventilation in patients with interstitial lung diseases (ILDs) and acute respiratory failure (ARF). These studies have not been synthesized and are not included in current practice guidelines. This systematic review with meta-analysis synthesizes studies that compared the effectiveness of NIPPV, HFNC and conventional oxygen therapy (COT) for improving oxygenation and ventilation in ILD patients with ARF.

Methods

MEDLINE, EMBASE and the Cochrane Library searches were conducted from inception to August 2023. An additional search of relevant primary literature and review articles was also performed. A random effects model was used to estimate the PF ratio (ratio of arterial oxygen partial pressure to fractional inspired oxygen), PaCO2 (partial pressure of carbon dioxide), mortality, intubation rate and hospital length of stay.

Results

Ten studies were included in the systematic review and meta-analysis. Noninvasive respiratory supports demonstrated a significant improvement in PF ratio compared to conventional oxygen therapy (COT); the mean difference was 55.92 (95% CI [18.85-92.99]; p=0.003). Compared to HFNC, there was a significant increase in PF ratio in NIPPV (mean difference 0.45; 95% CI [0.12-0.79]; p=0.008). There were no mortality and intubation rate benefits when comparing NIPPV and HFNC; the mean difference was 1.1; 95% CI [0.83-1.44]; p=0.51 and 1.86; 95% CI [0.42-8.33]; p=0.42, respectively. In addition, there was a significant decrease in hospital length of stay in HFNC compared to NIPPV (mean difference 9.27; 95% Cl [1.45 - 17.1]; p=0.02).

Conclusions

Noninvasive respiratory supports might be an alternative modality in ILDs with ARF. NIPPV demonstrated a potential to improve the PF ratio compared to HFNC. There was no evidence to support the benefit of NIPPV or HFNC in terms of mortality and intubation rate.

High-Flow Oxygen Therapy in the Perioperative Setting and Procedural Sedation: A Review of Current Evidence

High-flow oxygen therapy (HFOT) is a respiratory support system, through which high flows of humidified and heated gas are delivered to hypoxemic patients. Several mechanisms explain how HFOT improves arterial blood gases and enhances patients' comfort. Some mechanisms are well understood, but others are still unclear and under investigation. HFOT is an interesting oxygen-delivery modality in perioperative medicine that has many clinical applications in the intensive care unit (ICU) and the operating room (OR). The purpose of this article was to review the literature for a comprehensive understanding of HFOT in the perioperative period, as well as its uses in procedural sedation. This review will focus on the HFOT definition, its physiological benefits, and their mechanisms, its clinical uses in anesthesia, and when it is contraindicated.

Effects of CPAP and FiO2 on respiratory effort and lung stress in early COVID-19 pneumonia: a randomized, crossover study

BACKGROUND

in COVID-19 acute respiratory failure, the effects of CPAP and FiO2 on respiratory effort and lung stress are unclear. We hypothesize that, in the compliant lungs of early Sars-CoV-2 pneumonia, the application of positive pressure through Helmet-CPAP may not decrease respiratory effort, and rather worsen lung stress and oxygenation when compared to higher FiO2 delivered via oxygen masks.

METHODS

In this single-center (S.Luigi Gonzaga University-Hospital, Turin, Italy), randomized, crossover study, we included patients receiving Helmet-CPAP for early (< 48 h) COVID-19 pneumonia without additional cardiac or respiratory disease. Healthy subjects were included as controls. Participants were equipped with an esophageal catheter, a non-invasive cardiac output monitor, and an arterial catheter. The protocol consisted of a random sequence of non-rebreather mask (NRB), Helmet-CPAP (with variable positive pressure and FiO2) and Venturi mask (FiO2 0.5), each delivered for 20 min. Study outcomes were changes in respiratory effort (esophageal swing), total lung stress (dynamic + static transpulmonary pressure), gas-exchange and hemodynamics.

RESULTS

We enrolled 28 COVID-19 patients and 7 healthy controls. In all patients, respiratory effort increased from NRB to Helmet-CPAP (5.0 ± 3.7 vs 8.3 ± 3.9 cmH2O, p < 0.01). However, Helmet's pressure decreased by a comparable amount during inspiration (- 3.1 ± 1.0 cmH2O, p = 0.16), therefore dynamic stress remained stable (p = 0.97). Changes in static and total lung stress from NRB to Helmet-CPAP were overall not significant (p = 0.07 and p = 0.09, respectively), but showed high interpatient variability, ranging from - 4.5 to + 6.1 cmH2O, and from - 5.8 to + 5.7 cmH2O, respectively. All findings were confirmed in healthy subjects, except for an increase in dynamic stress (p < 0.01). PaO2 decreased from NRB to Helmet-CPAP with FiO2 0.5 (107 ± 55 vs 86 ± 30 mmHg, p < 0.01), irrespective of positive pressure levels (p = 0.64). Conversely, with Helmet's FiO2 0.9, PaO2 increased (p < 0.01), but oxygen delivery remained stable (p = 0.48) as cardiac output decreased (p = 0.02). When PaO2 fell below 60 mmHg with VM, respiratory effort increased proportionally (p < 0.01, r = 0.81).

CONCLUSIONS

In early COVID-19 pneumonia, Helmet-CPAP increases respiratory effort without altering dynamic stress, while the effects upon static and total stress are variable, requiring individual assessment. Oxygen masks with higher FiO2 provide better oxygenation with lower respiratory effort. Trial registration Retrospectively registered (13-May-2021): clinicaltrials.gov (NCT04885517), https://clinicaltrials.gov/ct2/show/NCT04885517 .

Physiological effects of awake prone position in acute hypoxemic respiratory failure

BACKGROUND

The effects of awake prone position on the breathing pattern of hypoxemic patients need to be better understood. We conducted a crossover trial to assess the physiological effects of awake prone position in patients with acute hypoxemic respiratory failure.

METHODS

Fifteen patients with acute hypoxemic respiratory failure and PaO2/FiO2 < 200 mmHg underwent high-flow nasal oxygen for 1 h in supine position and 2 h in prone position, followed by a final 1-h supine phase. At the end of each study phase, the following parameters were measured: arterial blood gases, inspiratory effort (ΔPES), transpulmonary driving pressure (ΔPL), respiratory rate and esophageal pressure simplified pressure-time product per minute (sPTPES) by esophageal manometry, tidal volume (VT), end-expiratory lung impedance (EELI), lung compliance, airway resistance, time constant, dynamic strain (VT/EELI) and pendelluft extent through electrical impedance tomography.

RESULTS

Compared to supine position, prone position increased PaO2/FiO2 (median [Interquartile range] 104 mmHg [76-129] vs. 74 [69-93], p < 0.001), reduced respiratory rate (24 breaths/min [22-26] vs. 27 [26-30], p = 0.05) and increased ΔPES (12 cmH2O [11-13] vs. 9 [8-12], p = 0.04) with similar sPTPES (131 [75-154] cmH2O s min-1 vs. 105 [81-129], p > 0.99) and ΔPL (9 [7-11] cmH2O vs. 8 [5-9], p = 0.17). Airway resistance and time constant were higher in prone vs. supine position (9 cmH2O s arbitrary units-3 [4-11] vs. 6 [4-9], p = 0.05; 0.53 s [0.32-61] vs. 0.40 [0.37-0.44], p = 0.03). Prone position increased EELI (3887 arbitrary units [3414-8547] vs. 1456 [959-2420], p = 0.002) and promoted VT distribution towards dorsal lung regions without affecting VT size and lung compliance: this generated lower dynamic strain (0.21 [0.16-0.24] vs. 0.38 [0.30-0.49], p = 0.004). The magnitude of pendelluft phenomenon was not different between study phases (55% [7-57] of VT in prone vs. 31% [14-55] in supine position, p > 0.99).

CONCLUSIONS

Prone position improves oxygenation, increases EELI and promotes VT distribution towards dependent lung regions without affecting VT size, ΔPL, lung compliance and pendelluft magnitude. Prone position reduces respiratory rate and increases ΔPES because of positional increases in airway resistance and prolonged expiratory time. Because high ΔPES is the main mechanistic determinant of self-inflicted lung injury, caution may be needed in using awake prone position in patients exhibiting intense ΔPES. Clinical trail registeration: The study was registered on clinicaltrials.gov (NCT03095300) on March 29, 2017.

Acute dyspnea in the emergency department: a clinical review

Acute dyspnea represents one of the most frequent symptoms leading to emergency room evaluation. Its significant prognostic value warrants a careful evaluation. The differential diagnosis of dyspnea is complex due to the lack of specificity and the loose association between its intensity and the severity of the underlying pathological condition. The initial assessment of dyspnea calls for prompt diagnostic evaluation and identification of optimal monitoring strategy and provides information useful to allocate the patient to the most appropriate setting of care. In recent years, accumulating evidence indicated that lung ultrasound, along with echocardiography, represents the first rapid and non-invasive line of assessment that accurately differentiates heart, lung or extra-pulmonary involvement in patients with dyspnea. Moreover, non-invasive respiratory support modalities such as high-flow nasal oxygen and continuous positive airway pressure have aroused major clinical interest, in light of their efficacy and practicality to treat patients with dyspnea requiring ventilatory support, without using invasive mechanical ventilation. This clinical review is focused on the pathophysiology of acute dyspnea, on its clinical presentation and evaluation, including ultrasound-based diagnostic workup, and on available non-invasive modalities of respiratory support that may be required in patients with acute dyspnea secondary or associated with respiratory failure.

Personalized Respiratory Support in ARDS: A Physiology-to-Bedside Review

Acute respiratory distress syndrome (ARDS) is a leading cause of disability and mortality worldwide, and while no specific etiologic interventions have been shown to improve outcomes, noninvasive and invasive respiratory support strategies are life-saving interventions that allow time for lung recovery. However, the inappropriate management of these strategies, which neglects the unique features of respiratory, lung, and chest wall mechanics may result in disease progression, such as patient self-inflicted lung injury during spontaneous breathing or by ventilator-induced lung injury during invasive mechanical ventilation. ARDS characteristics are highly heterogeneous; therefore, a physiology-based approach is strongly advocated to titrate the delivery and management of respiratory support strategies to match patient characteristics and needs to limit ARDS progression. Several tools have been implemented in clinical practice to aid the clinician in identifying the ARDS sub-phenotypes based on physiological peculiarities (inspiratory effort, respiratory mechanics, and recruitability), thus allowing for the appropriate application of personalized supportive care. In this narrative review, we provide an overview of noninvasive and invasive respiratory support strategies, as well as discuss how identifying ARDS sub-phenotypes in daily practice can help clinicians to deliver personalized respiratory support and potentially improve patient outcomes.

Assessment of Inspiratory Effort in Spontaneously Breathing COVID-19 ARDS Patients Undergoing Helmet CPAP: A Comparison between Esophageal, Transdiaphragmatic and Central Venous Pressure Swing

INTRODUCTION

The clinical features of COVID-19 are highly variable. It has been speculated that the progression across COVID-19 may be triggered by excessive inspiratory drive activation. The aim of the present study was to assess whether the tidal swing in central venous pressure (ΔCVP) is a reliable estimate of inspiratory effort.

METHODS

Thirty critically ill patients with COVID-19 ARDS underwent a PEEP trial (0-5-10 cmH₂O) during helmet CPAP. Esophageal (ΔPes) and transdiaphragmatic (ΔPdi) pressure swings were measured as indices of inspiratory effort. ΔCVP was assessed via a standard venous catheter. A low and a high inspiratory effort were defined as ΔPes ≤ 10 and  >15 cmH2O, respectively.

RESULTS

During the PEEP trial, no significant changes in ΔPes (11 [6-16] vs. 11 [7-15] vs. 12 [8-16] cmH2O, p = 0.652) and in ΔCVP (12 [7-17] vs. 11.5 [7-16] vs. 11.5 [8-15] cmH2O, p = 0.918) were detected. ΔCVP was significantly associated with ΔPes (marginal R² 0.87, p < 0.001). ΔCVP recognized both low (AUC-ROC curve 0.89 [0.84-0.96]) and high inspiratory efforts (AUC-ROC curve 0.98 [0.96-1]).

CONCLUSIONS

ΔCVP is an easily available a reliable surrogate of ΔPes and can detect a low or a high inspiratory effort. This study provides a useful bedside tool to monitor the inspiratory effort of spontaneously breathing COVID-19 patients.

Performance of helmet CPAP using different configurations: Turbine-driven ventilators vs Venturi devices

BACKGROUND

Traditionally, Venturi-based flow generators have been preferred over mechanical ventilators to provide continuous positive airway pressure (CPAP) through the helmet (h-CPAP). Recently, modern turbine-driven ventilators (TDVs) showed to be safe and effective in delivering h-CPAP. We aimed to compare the pressure stability during h-CPAP delivered by Venturi devices and TDVs and assess the impact of High Efficiency Particulate Air (HEPA) filters on their performance.

METHODS

We performed a bench study using an artificial lung simulator set in a restrictive respiratory condition, simulating two different levels of patient effort (high and low) with and without the interposition of the HEPA filter. We calculated the average of minimal (Pmin), maximal (Pmax) and mean (Pmean) airway pressure and the time product measured on the airway pressure curve (PTPinsp). We defined the pressure swing (Pswing) as Pmax - Pmin and pressure drop (Pdrop) as End Expiratory Pressure - Pmin.

RESULTS

Pswing across CPAP levels varied widely among all the tested devices. During "low effort", no difference in Pswing and Pdrop was found between Venturi devices and TDVs; during high effort, Pswing (p<0.001) and Pdrop (p<0.001) were significantly higher in TDVs compared to Venturi devices, but the PTPinsp was lower (1.50 SD 0.54 vs 1.67 SD 0.55, p<0.001). HEPA filter addition almost doubled Pswing and PTPinsp (p<0.001) but left unaltered the differences among Venturi and TDVs systems in favor of the latter (p<0.001).

CONCLUSIONS

TDVs performed better than Venturi systems in delivering a stable positive pressure level during h-CPAP in a bench setting.

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

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

Lessons from COVID-19 in the management of acute respiratory failure

Accumulated evidence supports the efficacy of noninvasive respiratory support therapies in coronavirus disease 2019 (COVID-19)-related acute hypoxaemic respiratory failure, alleviating admissions to intensive care units. Noninvasive respiratory support strategies, including high-flow oxygen therapy, continuous positive airway pressure via mask or helmet and noninvasive ventilation, can be alternatives that may avoid the need for invasive ventilation. Alternating different noninvasive respiratory support therapies and introducing complementary interventions, like self-proning, may improve outcomes. Proper monitoring is warranted to ensure the efficacy of the techniques and to avoid complications while supporting transfer to the intensive care unit. This article reviews the latest evidence on noninvasive respiratory support therapies in COVID-19-related acute hypoxaemic respiratory failure.

Helmet noninvasive ventilation in acute hypoxic respiratory failure

PURPOSE OF REVIEW

Invasive mechanical ventilation is a lifesaving intervention for patients with severe acute hypoxic respiratory failure (AHRF), but it is associated with neuromuscular, cognitive, and infectious complications. Noninvasive ventilation (NIV) may provide sufficient respiratory support without these complications. The helmet interface for NIV could address concerns raised for the use of NIV as first-line therapy in AHRF. This review will summarize and appraise the current evidence for helmet NIV in AHRF.

RECENT FINDINGS

There are only six randomized controlled trials comparing helmet NIV to standard nasal cannula, facemask NIV, or high-flow nasal oxygen in patients with AHRF. Lower rates of endotracheal intubations and fewer days of mechanical ventilation were reported, with inconsistent findings on patient survival. Facemask NIV may worsen preexisting lung injury, delay intubations, and be inferior at delivering lung protective ventilation strategies compared with mechanical ventilation. The helmet interface could circumvent some of these concerns through the delivery of higher positive end expiratory pressure and more uniform distribution of negative pleural pressure.

SUMMARY

There is limited evidence to support or refute the use of helmet NIV in AHRF. Further studies investigating the interface of helmet in NIV as a separate clinical entity are needed.

Flow generators for helmet CPAP: Which to prefer? A bench study

OBJECTIVE

To assess the different effect of filters' application during helmet-CPAP delivered with three different flow generators on the delivered fresh gas flow, FiO₂, and the noise level inside and outside the helmet.

METHODS

In a bench study, three flow generators (air-oxygen blender, turbine ventilator and Venturi system) were used to generate two different gas flows (60 L/min and 80 L/min), with a fixed FiO₂ at 0.6, to perform a helmet-CPAP on a manikin. Three different fixed PEEP valves (7.5, 10, and 12.5 cmH₂O) were applied at the expiratory port. Gas flow, FiO₂ and noise were recorded for each Flow-generator/Flow/PEEP combination, first without filter interposition and then after positioning a heat and moister exchanger filter (HMEF) at the helmet inlet port.

RESULTS

The application of the HMEF lead to a significant difference in the flow variation among the three flow generators (p < 0.001). Compared to baseline, the highest flow reduction was observed with the VENTURI (-13.4 ± 1.2 %, p < 0.001), a slight increase with the BLENDER (1.2 ± 0.5 %, p < 0.001), whereas no difference was recorded with the TURBINE (0.1 ± 0.6 %, p = 0.12). After HMEF was interposed, a significant FiO₂ variation was observed only with VENTURI (11.3 ± 1.8 %, p < 0.001). As for the noise, the TURBINE was the least noisy system, both with and without the filter interposition.

CONCLUSIONS

Flow generators used to deliver helmet-CPAP have different characteristics and responses to HMEF interposition. Users should be aware of the effects on FiO₂ and flow of the different devices in order to make a precise setup of the circuit.

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.

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.

The right interface for the right patient in noninvasive ventilation: a systematic review

INTRODUCTION

Research in the field of noninvasive ventilation (NIV) has contributed to the development of new NIV interfaces. However, interface tolerance plays a crucial role in determining the beneficial effects of NIV therapy.

AREAS COVERED

This systematic review explores the most significant scientific research on NIV interfaces, with a focus on the potential impact that their design might have on treatment adherence and clinical outcomes. The rationale on the choice of the right interface among the wide variety of devices that are currently available is discussed here.

EXPERT OPINION

The paradigm "The right mask for the right patient" seems to be difficult to achieve in real life. Ranging from acute to chronic settings, the gold standard should include the tailoring of NIV interfaces to patients' needs and preferences. However, such customization may be hampered by issues of economic nature. High production costs and the increasing demand represent consistent burdens and have to be considered when dealing with patient-tailored NIV interfaces. New research focusing on developing advanced and tailored NIV masks should be prioritized; indeed, interfaces should be designed according to the specific patient and clinical setting where they need to be used.

COVID-19: Opportunities to Improve Prognosis

COVID-19 is characterized by a severe course in approximately 5‒10% of patients, who require admittance to the intensive care unit and mechanical ventilation, which is associated with a very high risk of a poor prognosis. At present, in real clinical practice, in managing severe patients with COVID-19, noninvasive ventilation (NIV) is widely used (in some countries, up to 60% of all methods of respiratory support). In most studies on the effectiveness of NIV in hypoxemic acute respiratory failure in patients with COVID-19, the need for tracheal intubation and hospital mortality with the use of NIV averaged 20-30%, which suggests the rather high efficiency of this method. The COVID-19 pandemic has given a powerful impetus to the widespread use of prone positioning among nonintubated patients with acute respiratory failure caused by COVID-19. Several studies have shown that prone positioning can reduce the need for mechanical ventilation and hospital mortality. Medications that have proven effective in severe forms of COVID-19 include remdesivir, systemic glucocorticoids, tocilizumab, baricitinib, and anticoagulants. Among the new promising areas of drug therapy, noteworthy is the use of thiol-containing drugs (N-acetylcysteine), inhaled surfactant, and inhaled prostacyclin analogues.

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.

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.

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.

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.

Effect of pressures and type of ventilation on aerosol delivery to chronic obstructive pulmonary disease patients

Background

Continuous Positive Airway Pressure (CPAP), BiPhasic Positive Airway Pressure (BiPAP), and high flow nasal cannula (HFNC) show some evidence to have efficacy in COVID-19 patients. Delivery during noninvasive mechanical ventilation (NIV) or HFNC gives faster and more enhanced clinical effects than when aerosols are given without assisted breath. The present work aimed to compare the effect of BiPhasic Positive Airway Pressure (BiPAP) mode at two different pressures; low BiPAP (Inspiratory Positive Airway Pressure (IPAP)/Expiratory Positive Airway Pressure (EPAP) of 10/5 cm water) and high BiPAP (IPAP/EPAP of 20/5 cm water), with HFNC system on pulmonary and systemic drug delivery of salbutamol. On the first day of the experiment, all patients received 2500 μg salbutamol using Aerogen Solo vibrating mesh nebulizer. Urine samples 30 min post-dose and cumulative urinary salbutamol during the next 24 h were collected on the next day. On the third day, the ex-vivo filter was inserted before the patient to collect the delivered dose to the patient of the 2500 μg salbutamol. Salbutamol was quantified using high-performance liquid chromatography (HPLC).

Results

Low-pressure BiPAP showed the highest amount delivered to the lung after 30 min followed by HFNC then high-pressure BiPAP. But the significant difference was only observed between low and high-pressure BiPAP modes (p = 0.012). Low-pressure BiPAP showed the highest delivered systemic delivery amount followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.017) and high-pressure BiPAP (p = 0.008). No significant difference was reported between HFNC and high-pressure BiPAP. The ex-vivo filter was the greatest in the case of low-pressure BiPAP followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.033) and high-pressure BiPAP (p = 0.008). Also, no significant difference was found between HFNC and high-pressure BiPAP.

Conclusions

Our results of pulmonary, systemic, and ex-vivo drug delivery were found to be consistent. The low BiPAP delivered the highest amount followed by the HFNC then the high BiPAP with the least amount. However, no significant difference was found between HFNC and high BiPAP.

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.

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.

Dexmedetomidine in critically ill adults requiring noninvasive ventilation

Noninvasive ventilation (NIV) is an effective therapy for hypercapnic and hypoxemic respiratory failure and can reduce the need for intubation and mechanical ventilation.¹ It may also reduce intensive care unit (ICU) length of stay, pneumonia, and mortality.^2-6 However, NIV can be uncomfortable for patients due to the mask interface and respiratory pressures delivered, and over one-third of patients placed on NIV will experience agitation.^7,8 Intolerance to NIV typically requires intubation. A variety of interventions can be utilized to improve compliance with NIV, including medications such as dexmedetomidine, an α-2 agonist with sedative and analgesic effects.⁹ Current guidelines recommend the use of a non-benzodiazepine sedative such as propofol or dexmedetomidine in critically ill, mechanically ventilated adults, as these medications may improve delirium, ICU length of stay, and duration of mechanical ventilation.¹⁰.

Early assessment of the efficacy of noninvasive ventilation tested by HACOR score to avoid delayed intubation in patients with moderate to severe ARDS

Background:

Use of noninvasive ventilation (NIV) in patients with moderate to severe ARDS is controversial. We aimed to use HACOR (combination of heart rate, acidosis, consciousness, oxygenation and respiratory rate) score to comprehensively assess the efficacy of NIV in ARDS patients with PaO₂/FiO₂ ⩽ 150 mmHg.

Methods:

Secondary analysis was performed using the data collected from two databases. We screened the ARDS patients who used NIV as a first-line therapy. Patients with PaO₂/FiO₂ ⩽ 150 mmHg were enrolled. NIV failure was defined as requirement of intubation.

Results:

A total of 224 moderate to severe ARDS patients who used NIV as a first-line therapy were enrolled. Of them, 125 patients (56%) experienced NIV failure and received intubation. Among the intubated patients, the survivor had shorter time from initiation of NIV to intubation than nonsurvivors (median 10 vs 22 h, p  < 0.01). The median differences of HACOR score before and 1–2 h of NIV were 1 point (interquartile range: 0–3). We defined the patients with △HACOR >1 as responders (n  = 102) and the rest to non-responders (n  = 122). Compared to non-responders, the responders had higher HACOR score before NIV. However, the HACOR score was lower in the responders than non-responders after 1–2 h, 12 h, and 24 h of NIV. The responders also had lower NIV failure rate (36% vs 72%, p  < 0.01) and lower 28-day mortality (32% vs 47%, p  = 0.04) than non-responders.

Conclusions:

NIV failure was high among patients with moderate to severe ARDS. Delayed intubation is associated with increased mortality. The reduction of HACOR score after 1–2 h of NIV can identify the patients who respond well to NIV.

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 Ventilation and Oxygenation Strategies

Noninvasive ventilation (NIV) provides respiratory support without the use of invasive ventilation with techniques that do not bypass the upper airway. NIV is particularly attractive given its associated reduced risk of complications associated with intubation. Available NIV modes include nasal cannula, simple mask, nonrebreather, high flow nasal cannula, continuous positive airway pressure (CPAP), and bilevel positive airway pressure. Acute exacerbation of COPD, cardiogenic pulmonary edema, and COVID-19 are conditions for which NIV has shown to be beneficial, whereas there is no consensus among the use of NIV in trauma patients and ARDS.