Inspiratory Effort and Lung Mechanics in Spontaneously Breathing Patients with Acute Respiratory Failure Due to COVID-19: A Matched Control Study

Development of clinical tools to estimate the breathing effort during high-flow oxygen therapy: A multicenter cohort study

INTRODUCTION AND OBJECTIVES

Quantifying breathing effort in non-intubated patients is important but difficult. We aimed to develop two models to estimate it in patients treated with high-flow oxygen therapy.

PATIENTS AND METHODS

We analyzed the data of 260 patients from previous studies who received high-flow oxygen therapy. Their breathing effort was measured as the maximal deflection of esophageal pressure (ΔPes). We developed a multivariable linear regression model to estimate ΔPes (in cmH2O) and a multivariable logistic regression model to predict the risk of ΔPes being >10 cmH2O. Candidate predictors included age, sex, diagnosis of the coronavirus disease 2019 (COVID-19), respiratory rate, heart rate, mean arterial pressure, the results of arterial blood gas analysis, including base excess concentration (BEa) and the ratio of arterial tension to the inspiratory fraction of oxygen (PaO2:FiO2), and the product term between COVID-19 and PaO2:FiO2.

RESULTS

We found that ΔPes can be estimated from the presence or absence of COVID-19, BEa, respiratory rate, PaO2:FiO2, and the product term between COVID-19 and PaO2:FiO2. The adjusted R2 was 0.39. The risk of ΔPes being >10 cmH2O can be predicted from BEa, respiratory rate, and PaO2:FiO2. The area under the receiver operating characteristic curve was 0.79 (0.73-0.85). We called these two models BREF, where BREF stands for BReathing EFfort and the three common predictors: BEa (B), respiratory rate (RE), and PaO2:FiO2 (F).

CONCLUSIONS

We developed two models to estimate the breathing effort of patients on high-flow oxygen therapy. Our initial findings are promising and suggest that these models merit further evaluation.

Assessment of nasal pressure swing predicts respiratory support dependency in patients with hypoxic respiratory failure

BACKGROUND

Monitoring is essential in managing acute hypoxemic respiratory failure (AHRF). Nasal pressure swing (Pnose) may predict high-flow nasal oxygen (HFNO) therapy failure and respiratory support dependency. This study investigates Pnose's predictive value for respiratory support needs and clinical outcomes in AHRF patients initially treated with HFNO.

METHODS

This post-hoc analysis included 60 AHRF patients treated with HFNO. Respiratory variables, including Pnose, were assessed at baseline and two hours after HFNO initiation. Patients were classified into high (HG) and low (LG) Pnose groups based on a 5.1 cmH2O threshold. The primary outcome was RS-free survival at day 7; HFNO failure, escalation to non-invasive ventilation (NIV) or mechanical ventilation (MV), mortality, and HFNO weaning time were also analyzed. Predictive accuracy of respiratory indices, including Pnose, was evaluated.

RESULTS

Out of the patients enrolled, 35 were in the HG, and 25 in LG group. HG patients showed a lower RS-free survival at day 7 (adjusted HR=0.26, p < 0.0001), and experienced higher failure rates of HFNO (88 % versus 0 %, p < 0.0001), escalation to NIV (84 % versus 0 %, p < 0.0001), endotracheal intubation (36 % versus 0 %, p < 0.0001), and mortality (24 % versus 6 %, p = 0.0001) compared to LG. Accordingly, RS-free days at day 28 were lower in HG (11 days versus 23 days, p < 0.0001). Finally, among the respiratory variables, Pnose resulted independently associated with the primary outcome (OR=0.64 95 %CI [0.42-0.90], p = 0.02).

CONCLUSIONS

In patients with AHRF admitted to the ward and treated by HFNO, Pnose is an independent and accurate factor in forecasting the dependency from RS and survival within the first week.

Airway pressures generated by high flow nasal cannula in patients with acute hypoxemic respiratory failure: a computational study

INTRODUCTION AND OBJECTIVES

High flow nasal cannula (HFNC) therapy is an increasingly popular mode of non-invasive respiratory support for the treatment of patients with acute hypoxemic respiratory failure (AHRF). Previous experimental studies in healthy subjects have established that HFNC generates flow-dependent positive airway pressures, but no data is available on the levels of mean airway pressure (mPaw) or positive end-expiratory pressure (PEEP) generated by HFNC therapy in AHRF patients. We aimed to estimate the airway pressures generated by HFNC at different flow rates in patients with AHRF, whose functional lung volume may be significantly reduced compared to healthy subjects due to alveolar consolidation and/or collapse.

MATERIALS AND METHODS

We developed a high-fidelity mechanistic computational model of the cardiopulmonary system during HFNC therapy using data from healthy subjects, and then measured the mPaw and PEEP levels produced when different amounts of alveolar consolidation/collapse were incorporated into the model.

RESULTS

When calibrated to represent normal lung physiology in healthy subjects, our model recapitulates the airway pressures produced by HFNC at different flow rates in healthy volunteers who were breathing normally, with their mouths closed or open. When different amounts of alveolar consolidation/collapse are implemented in the model to reflect the pathophysiology of AHRF, the mPaw and PEEP produced by HFNC at all flow rates increase as the functional lung volume decreases (up to a mPaw of 11.53 and a PEEP of 11.41 cmH2O at 60 L/min with the mouth closed when 50% of the model's alveolar compartments are non-aerated). When the model was matched to individual patient data from a cohort of 58 patients with AHRF receiving HFNC at 60 L/min, the mean (standard deviation) of the mPaw / PEEP produced by HFNC in the models of these patients was 8.56 (1.50) / 8.92 (1.49) cmH2O with mouths closed, and 1.73 (0.31) / 1.36 (0.36) cmH2O with mouths open.

CONCLUSIONS

Our results suggest that the airway pressures produced by HFNC in patients with AHRF could be higher than is currently assumed based on experimental data from healthy subjects, particularly in patients whose mouths remain closed. Higher levels of PEEP could be beneficial if they lead to alveolar recruitment and improved lung compliance, but could cause alveolar overdistension if they do not, motivating the close monitoring of the effects of HFNC on lung mechanics. Further clinical studies are warranted to directly measure the airway pressures produced by HFNC in patients with different severities of AHRF.

Comparison of the risk of pneumothorax in COVID-19 and seasonal influenza

Limited evidence exists regarding the link between coronavirus disease 2019 (COVID-19) and pneumothorax. Therefore, we aimed to evaluate the occurrence rate of pneumothorax in hospitalized patients with COVID-19 and compare the risk of pneumothorax between patients with COVID-19 and influenza. This retrospective cohort study used patient data from the National Health Insurance Service of South Korea. Patients diagnosed with COVID-19 (December 2019 to December 2021) and influenza (January 2019 to December 2021) who required hospitalization and respiratory support were included. We identified 46,460 patients with COVID-19 and 6,117 with influenza. The occurrence rate of pneumothorax was 0.74% in patients with COVID-19. In an inverse probability of treatment weighting matched cohort, the Cox proportional hazards regression model showed that COVID-19 was not associated with an increased risk of pneumothorax compared to influenza (hazard ratio, 1.22; 95% confidence interval, 0.75-1.99). However, the risk of pneumothorax associated with COVID-19 compared to influenza was significantly higher in patients without chronic lung disease than in those with (P for heterogeneity = 0.037). In conclusion, COVID-19, compared with influenza, is not associated with an increased risk of pneumothorax; however, it is associated with an increased risk in patients without chronic lung disease.

Interpretability-based machine learning for predicting the risk of death from pulmonary inflammation in Chinese intensive care unit patients

Objective

The objective of this research was to create a machine learning predictive model that could be easily interpreted in order to precisely determine the risk of premature death in patients receiving intensive care after pulmonary inflammation.

Methods

In this study, information from the China intensive care units (ICU) Open Source database was used to examine data from 2790 patients who had infections between January 2019 and December 2020. A 7:3 ratio was used to randomly assign the whole patient population to training and validation groups. This study used six machine learning techniques: logistic regression, random forest, gradient boosting tree, extreme gradient boosting tree (XGBoost), multilayer perceptron, and K-nearest neighbor. A cross-validation grid search method was used to search the parameters in each model. Eight metrics were used to assess the models' performance: accuracy, precision, recall, F1 score, area under the curve (AUC) value, Brier score, Jordon's index, and calibration slope. The machine methods were ranked based on how well they performed in each of these metrics. The best-performing models were selected for interpretation using both the Shapley Additive exPlanations (SHAP) and Local interpretable model-agnostic explanations (LIME) interpretable techniques.

Results

A subset of the study cohort's patients (120/1668, or 7.19%) died in the hospital following screening for inclusion and exclusion criteria. Using a cross-validated grid search to evaluate the six machine learning techniques, XGBoost showed good discriminative ability, achieving an accuracy score of 0.889 (0.874-0.904), precision score of 0.871 (0.849-0.893), recall score of 0.913 (0.890-0.936), F1 score of 0.891 (0.876-0.906), and AUC of 0.956 (0.939-0.973). Additionally, XGBoost exhibited excellent performance with a Brier score of 0.050, Jordon index of 0.947, and calibration slope of 1.074. It was also possible to create an interactive internet page using the XGBoost model.

Conclusion

By identifying patients at higher risk of early mortality, machine learning-based mortality risk prediction models have the potential to significantly improve patient care by directing clinical decision making and enabling early detection of survival and mortality issues in patients with pulmonary inflammation disease.

Association between respiratory distress time and invasive mechanical ventilation in COVID-19 patients: A multicentre regional cohort study

AIM

To determine whether the duration of respiratory distress symptoms in severe COVID-19 pneumonia affects the need for invasive mechanical ventilation and clinical outcomes.

MATERIALS AND METHODS

An observational multicentre cohort study of patients hospitalised in five COVID-19-designated ICUs of the University Hospitals of Emilia-Romagna Region. Patients included were adults with pneumonia due to SARS-CoV-2 with PaO₂/FiO₂ ratio <300 mmHg, respiratory distress symptoms, and need for mechanical ventilation (invasive or non-invasive). Exclusion criteria were an uncertain time of respiratory distress, end-of-life decision, and mechanical respiratory support before hospital admission.

MEASUREMENTS AND MAIN RESULTS

We analysed 171 patients stratified into tertiles according to respiratory distress duration (distress time, DT) before application of mechanical ventilation support. The rate of patients requiring invasive mechanical ventilation was significantly different (p < 0.001) among the tertiles: 17/57 patients in the shortest duration, 29/57 in the intermediate duration, and 40/57 in the longest duration. The respiratory distress time significantly increased the risk of invasive ventilation in the univariate analysis (OR 5.5 [CI 2.48-12.35], p = 0.003). Multivariable regression analysis confirmed this association (OR 10.7 [CI 2.89-39.41], p < 0.001). Clinical outcomes (mortality and hospital stay) did not show significant differences between DT tertiles.

DISCUSSION

Albeit preliminary and retrospective, our data raised the hypothesis that the duration of respiratory distress symptoms may play a role in COVID-19 patients' need for invasive mechanical ventilation. Furthermore, our observations suggested that specific strategies may be directed towards identifying and managing early symptoms of respiratory distress, regardless of the levels of hypoxemia and the severity of the dyspnoea itself.

Oscillometry Longitudinal Data on COVID-19 Acute Respiratory Syndrome Treated with Non-Invasive Respiratory Support

Background: Oscillometry allows for the non-invasive measurements of lung mechanics. In COVID-19 ARDS patients treated with Non-Invasive Oxygen Support (NI-OS), we aimed to (1) observe lung mechanics at the patients' admission and their subsequent changes, (2) compare lung mechanics with clinical and imaging data, and (3) evaluate whether lung mechanics helps to predict clinical outcomes. Methods: We retrospectively analyzed the data from 37 consecutive patients with moderate-severe COVID-19 ARDS. Oscillometry was performed on their 1st, 4th, and 7th day of hospitalization. Resistance (R5), reactance (X5), within-breath reactance changes (ΔX5), and the frequency dependence of the resistance (R5-R19) were considered. Twenty-seven patients underwent computed tomographic pulmonary angiography (CTPA): collapsed, poorly aerated, and normally inflated areas were quantified. Adverse outcomes were defined as intubation or death. Results: Thirty-two patients were included in this study. At the first measurement, only 44% of them had an abnormal R5 or X5. In total, 23 patients had measurements performed on their 3rd day and 7 on their 7th day of hospitalization. In general, their R5, R5-R19, and ΔX decreased with time, while their X5 increased. Collapsed areas on the CTPA correlated with the X5 z-score (ρ = -0.38; p = 0.046), while poorly aerated areas did not. Seven patients had adverse outcomes but did not present different oscillometry parameters on their 1st day of hospitalization. Conclusions: Our study confirms the feasibility of oscillometry in critically ill patients with COVID-19 pneumonia undergoing NI-OS. The X5 z-scores indicates collapsed but not poorly aerated lung areas in COVID-19 pneumonia. Our data, which show a severe impairment of gas exchange despite normal reactance in most patients with COVID-19 ARDS, support the hypothesis of a composite COVID-19 ARDS physiopathology.

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

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

Optimizing the safety and efficacy of the awake venovenous extracorporeal membrane oxygenation in patients with COVID-19-related ARDS

BACKGROUND

Maintaining the patient awake and not intubated during the venovenous extracorporeal membrane oxygenation (VV ECMO) reduces the risk of ventilation-induced lung injury in patients with ARDS. Currently, there is a lack of data on outcomes and complications associated with the awake ECMO approach.

OBJECTIVES

To evaluate outcomes and the occurrence of complications of awake ECMO approach guided by local safety protocol comprising ultrasound-guided cannulation, argatroban-based anticoagulation, respiratory support, and routine sedation targeted to reduce respiratory effort and keeping nurse-to-patient ratio of 1:1.

DESIGN

A single-center retrospective case series analysis.

METHODS

Consecutive patients with COVID-19-related acute respiratory distress syndrome (ARDS) (CARDS) treated by full awake VV ECMO approach from April 2019 to December 2023 were eligible.

RESULTS

Our center treated 10 patients (mean age 54.7 ± 11.6 years) with CARDS with an awake ECMO approach. The reasons for awake ECMO included the presence of barotrauma in six patients, a team consensus to prefer awake ECMO instead of mechanical ventilation in three patients, and the patient's refusal to be intubated in one case. Before ECMO, patients were severely hypoxemic, with a mean value of Horowitz index of 48.9 ± 9.1 mmHg and a mean respiratory rate of 28.8 ± 7.3 breaths per minute on high-flow nasal cannula or noninvasive ventilation support. The mean duration of awake VV ECMO was 558.0 ± 173.6 h. Seven patients (70%) were successfully disconnected from ECMO and fully recovered. Intubation from respiratory causes was needed in three patients (30%), all of whom died eventually. In total, three episodes of delirium, two episodes of significant bleeding, one pneumothorax requiring chest tube insertion, and one oxygenator acute exchange occurred throughout the 5580 h of awake ECMO. No complications related to cannula displacement or malposition occurred.

CONCLUSION

The awake ECMO strategy guided by safety protocol appears to be a safe approach in conscious, severely hypoxemic, non-intubated patients with COVID-19-related ARDS.

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.

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 .

Effects of three spontaneous ventilation modes on respiratory drive and muscle effort in COVID-19 pneumonia patients

BACKGROUND

High drive and high effort during spontaneous breathing can generate patient self-inflicted lung injury (P-SILI) due to uncontrolled high transpulmonary and transvascular pressures, with deterioration of respiratory failure. P-SILI has been demonstrated in experimental studies and supported in recent computational models. Different treatment strategies have been proposed according to the phenotype of elastance of the respiratory system (Ers) for patients with COVID-19. This study aimed to investigate the effect of three spontaneous ventilation modes on respiratory drive and muscle effort in clinical practice and their relationship with different phenotypes. This was achieved by obtaining the following respiratory signals: airway pressure (Paw), flow (V´) and volume (V) and calculating muscle pressure (Pmus).

METHODS

A physiologic observational study of a series of cases in a university medical-surgical ICU involving 11 mechanically ventilated patients with COVID-19 pneumonia at the initiation of spontaneous breathing was conducted. Three spontaneous ventilation modes were evaluated in each of the patients: pressure support ventilation (PSV), airway pressure release ventilation (APRV), and BiLevel positive airway pressure ventilation (BIPAP). Pmus was calculated through the equation of motion. For this purpose, we acquired the signals of Paw, V´ and V directly from the data transmission protocol of the ventilator (Dräger). The main physiological measurements were calculation of the respiratory drive (P0.1), muscle effort through the ΔPmus, pressure‒time product (PTP/min) and work of breathing of the patient in joules multiplied by respiratory frequency (WOBp, J/min).

RESULTS

Ten mechanically ventilated patients with COVID-19 pneumonia at the initiation of spontaneous breathing were evaluated. Our results showed similar high drive and muscle effort in each of the spontaneous ventilatory modes tested, without significant differences between them: median (IQR): P0.1 6.28 (4.92-7.44) cm H2O, ∆Pmus 13.48 (11.09-17.81) cm H2O, PTP 166.29 (124.02-253.33) cm H2O*sec/min, and WOBp 12.76 (7.46-18.04) J/min. High drive and effort were found in patients even with low Ers. There was a significant relationship between respiratory drive and WOBp and Ers, though the coefficient of variation widely varied.

CONCLUSIONS

In our study, none of the spontaneous ventilatory methods tested succeeded in reducing high respiratory drive or muscle effort, regardless of the Ers, with subsequent risk of P-SILI.

Mechanical Power Delivered by Noninvasive Ventilation Contributes to Physio-Anatomical and Clinical Responses to Early Versus Late Proning in COVID-19 Pneumonia

OBJECTIVES

To study: 1) the effect of prone position (PP) on noninvasive ventilation (NIV)-delivered mechanical power (MP) and 2) the impact of MP on physio-anatomical and clinical responses to early versus late PP in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia.

DESIGN

Nonrandomized trial with inverse probability of treatment weighted-matched groups.

SETTING

HUMANITAS Gradenigo Sub-ICU.

PATIENTS

One hundred thirty-eight SARS-CoV-2 pneumonia patients with moderate-to-severe acute hypoxemic respiratory failure (Pa o2 /F io2 ratio < 200 mm Hg) receiving NIV from September 1, 2020, to February 28, 2021 (Ethics approval: ISRCTN23016116).

INTERVENTIONS

Early PP or late PP or supine position.

MEASUREMENTS AND MAIN RESULTS

Respiratory parameters were hourly recorded. Time-weighted average MP values were calculated for each ventilatory session. Gas exchange parameters and ventilatory ratio (VR) were measured 1 hour after each postural change. Lung ultrasonographic scores and circulating biomarkers were assessed daily. MP delivered during the initial 24 hours of NIV (MP [first 24 hr]) was the primary exposure variable. Primary outcomes: 28-day endotracheal intubation and death. Secondary outcomes: oxygen-response, C o2 -response, ultrasonographic, and systemic inflammatory biomarker responses after 24 hours of NIV. Fifty-eight patients received early PP + NIV, 26 late PP + NIV, and 54 supine NIV. Early PP group had lower 28-day intubation and death than late PP (hazard ratio [HR], 0.35; 95% CI, 0.19-0.69 and HR, 0.26; 95% CI, 0.07-0.67, respectively) and supine group. In Cox multivariate analysis, (MP [first 24 hr]) predicted 28-day intubation (HR, 1.70; 95% CI, 1.25-2.09; p = 0.009) and death (HR, 1.51; 95% CI, 1.19-1.91; p = 0.007). Compared with supine position, PP was associated with a 35% MP reduction. VR, ultrasonographic scores, and inflammatory biomarkers improved after 24 hours of NIV in the early PP, but not in late PP or supine group. A MP (first 24 hr) greater than or equal to 17.9 J/min was associated with 28-day death (area under the curve, 0.92; 95% CI, 0.88-0.96; p < 0.001); cumulative hours of MP greater than or equal to 17.9 J/min delivered before PP initiation attenuated VR, ultrasonographic, and biomarker responses to PP.

CONCLUSIONS

MP delivered by NIV during initial 24 hours predicts clinical outcomes. PP curtails MP, but cumulative hours of NIV with MP greater than or equal to 17.9 J/min delivered before PP initiation attenuate the benefits of PP.

Mechanical power normalized to aerated lung predicts noninvasive ventilation failure and death and contributes to the benefits of proning in COVID-19 hypoxemic respiratory failure

Background

Concern exists that noninvasive ventilation (NIV) may promote ventilation-induced lung injury(VILI) and worsen outcome in acute hypoxemic respiratory failure (AHRF). Different individual ventilatory variables have been proposed to predict clinical outcomes, with inconsistent results.Mechanical power (MP), a measure of the energy transfer rate from the ventilator to the respiratory system during mechanical ventilation, might provide solutions for this issue in the framework of predictive, preventive and personalized medicine (PPPM). We explored (1) the impact of ventilator-delivered MP normalized to well-aerated lung (MP_WAL) on physio-anatomical and clinical responses to NIV in COVID-19-related AHRF and (2) the effect of prone position(PP) on MP_WAL.

Methods

We analyzed 216 noninvasively ventilated COVID-19 patients (108 patients receiving PP + NIV and 108 propensity score-matched patients receiving supine NIV) with moderate-to-severe(paO2/FiO2 ratio < 200) AHRF enrolled in the PRO-NIV controlled non-randomized study (ISRCTN23016116).Quantification of differentially aerated lung volumes by lung ultrasonography (LUS) was validated against CT scans. Respiratory parameters were hourly recorded, ABG were performed 1 h after each postural change. Time-weighed average values of ventilatory variables, including MP_WAL, and gas exchange parameters (paO2/FiO2 ratio, dead space indices) were calculated for each ventilatory session. LUS and circulating biomarkers were assessed daily.

Results

Compared with supine position, PP was associated with a 34% MP_WAL reduction, attributable largely to an absolute MP reduction and secondly to an enhanced lung reaeration.Patients receiving a high MP_WAL during the 1^st 24 h of NIV [MP_WAL(day 1)] had higher 28-d NIV failure (HR = 4.33,95%CI:3.09 - 5.98) and death (HR = 5.17,95%CI: 3.01 - 7.35) risks than those receiving a low MP_WAL(day 1).In Cox multivariate analyses, MP_WAL(day 1) remained independently associated with 28-d NIV failure (HR = 1.68,95%CI:1.15-2.41) and death (HR = 1.69,95%CI:1.22-2.32).MP_WAL(day 1) outperformed other power measures and ventilatory variables as predictor of 28-d NIV failure (AUROC = 0.89;95%CI:0.85-0.93) and death (AUROC = 0.89;95%CI:0.85-0.94).MP_WAL(day 1) predicted also gas exchange, ultrasonographic and inflammatory biomarker responses, as markers of VILI, on linear multivariate analysis.

Conclusions

In the framework of PPPM, early bedside MP_WAL calculation may provide added value to predict response to NIV and guide subsequent therapeutic choices i.e. prone position adoption during NIV or upgrading to invasive ventilation, to reduce hazardous MP_WAL delivery, prevent VILI progression and improve clinical outcomes in COVID-19-related AHRF.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00325-5.

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.

Long-term outcome of COVID-19 patients treated with helmet noninvasive ventilation vs. high-flow nasal oxygen: a randomized trial

BACKGROUND

Long-term outcomes of patients treated with helmet noninvasive ventilation (NIV) are unknown: safety concerns regarding the risk of patient self-inflicted lung injury and delayed intubation exist when NIV is applied in hypoxemic patients. We assessed the 6-month outcome of patients who received helmet NIV or high-flow nasal oxygen for COVID-19 hypoxemic respiratory failure.

METHODS

In this prespecified analysis of a randomized trial of helmet NIV versus high-flow nasal oxygen (HENIVOT), clinical status, physical performance (6-min-walking-test and 30-s chair stand test), respiratory function and quality of life (EuroQoL five dimensions five levels questionnaire, EuroQoL VAS, SF36 and Post-Traumatic Stress Disorder Checklist for the DSM) were evaluated 6 months after the enrollment.

RESULTS

Among 80 patients who were alive, 71 (89%) completed the follow-up: 35 had received helmet NIV, 36 high-flow oxygen. There was no inter-group difference in any item concerning vital signs (N = 4), physical performance (N = 18), respiratory function (N = 27), quality of life (N = 21) and laboratory tests (N = 15). Arthralgia was significantly lower in the helmet group (16% vs. 55%, p = 0.002). Fifty-two percent of patients in helmet group vs. 63% of patients in high-flow group had diffusing capacity of the lungs for carbon monoxide < 80% of predicted (p = 0.44); 13% vs. 22% had forced vital capacity < 80% of predicted (p = 0.51). Both groups reported similar degree of pain (p = 0.81) and anxiety (p = 0.81) at the EQ-5D-5L test; the EQ-VAS score was similar in the two groups (p = 0.27). Compared to patients who successfully avoided invasive mechanical ventilation (54/71, 76%), intubated patients (17/71, 24%) had significantly worse pulmonary function (median diffusing capacity of the lungs for carbon monoxide 66% [Interquartile range: 47-77] of predicted vs. 80% [71-88], p = 0.005) and decreased quality of life (EQ-VAS: 70 [53-70] vs. 80 [70-83], p = 0.01).

CONCLUSIONS

In patients with COVID-19 hypoxemic respiratory failure, treatment with helmet NIV or high-flow oxygen yielded similar quality of life and functional outcome at 6 months. The need for invasive mechanical ventilation was associated with worse outcomes. These data indicate that helmet NIV, as applied in the HENIVOT trial, can be safely used in hypoxemic patients. Trial registration Registered on clinicaltrials.gov NCT04502576 on August 6, 2020.

Respective Effects of Helmet Pressure Support, Continuous Positive Airway Pressure, and Nasal High-Flow in Hypoxemic Respiratory Failure: A Randomized Crossover Clinical Trial

Rationale: The respective effects of positive end-expiratory pressure (PEEP) and pressure support delivered through the helmet interface in patients with hypoxemia need to be better understood. Objectives: To assess the respective effects of helmet pressure support (noninvasive ventilation [NIV]) and continuous positive airway pressure (CPAP) compared with high-flow nasal oxygen (HFNO) on effort to breathe, lung inflation, and gas exchange in patients with hypoxemia (PaO2/FiO2 ⩽ 200). Methods: Fifteen patients underwent 1-hour phases (constant FiO2) of HFNO (60 L/min), helmet NIV (PEEP = 14 cm H2O, pressure support = 12 cm H2O), and CPAP (PEEP = 14 cm H2O) in randomized sequence. Measurements and Main Results: Inspiratory esophageal (ΔPES) and transpulmonary pressure (ΔPL) swings were used as surrogates for inspiratory effort and lung distension, respectively. Tidal Volume (Vt) and end-expiratory lung volume were assessed with electrical impedance tomography. ΔPES was lower during NIV versus CPAP and HFNO (median [interquartile range], 5 [3-9] cm H2O vs. 13 [10-19] cm H2O vs. 10 [8-13] cm H2O; P = 0.001 and P = 0.01). ΔPL was not statistically different between treatments. PaO2/FiO2 ratio was significantly higher during NIV and CPAP versus HFNO (166 [136-215] and 175 [158-281] vs. 120 [107-149]; P = 0.002 and P = 0.001). NIV and CPAP similarly increased Vt versus HFNO (mean change, 70% [95% confidence interval (CI), 17-122%], P = 0.02; 93% [95% CI, 30-155%], P = 0.002) and end-expiratory lung volume (mean change, 198% [95% CI, 67-330%], P = 0.001; 263% [95% CI, 121-407%], P = 0.001), mostly due to increased aeration/ventilation in dorsal lung regions. During HFNO, 14 of 15 patients had pendelluft involving >10% of Vt; pendelluft was mitigated by CPAP and further by NIV. Conclusions: Compared with HFNO, helmet NIV, but not CPAP, reduced ΔPES. CPAP and NIV similarly increased oxygenation, end-expiratory lung volume, and Vt, without affecting ΔPL. NIV, and to a lesser extent CPAP, mitigated pendelluft. Clinical trial registered with clinicaltrials.gov (NCT04241861).

Highlights from the Respiratory Failure and Mechanical Ventilation 2022 Conference

The Respiratory Intensive Care Assembly of the European Respiratory Society gathered in Berlin to organise the second Respiratory Failure and Mechanical Ventilation Conference in June 2022. The conference covered several 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. Lectures delivered during the event have been summarised by Early Career Members of the Assembly and take-home messages highlighted.

Delayed mechanical ventilation with prolonged high-flow nasal cannula exposure time as a risk factor for mortality in acute respiratory distress syndrome due to SARS-CoV-2

In a high proportion of patients, infection by COVID-19 progresses to acute respiratory distress syndrome (ARDS), requiring invasive mechanical ventilation (IMV) and admission to an intensive care unit (ICU). Other devices, such as a high-flow nasal cannula (HFNC), have been alternatives to IMV in settings with limited resources. This study evaluates whether HFNC exposure time prior to IMV is associated with mortality. This observational, analytical study was conducted on a historical cohort of adults with ARDS due to SARS-CoV-2 who were exposed to HFNC and subsequently underwent IMV. Univariate and multivariate logistic regression was used to analyze the impact of HFNC exposure time on mortality, controlling for multiple potential confounders. Of 325 patients with ARDS, 41 received treatment with HFNC for more than 48 h before IMV initiation. These patients had a higher mortality rate (43.9% vs. 27.1%, p: 0.027) than those using HFNC < 48 h. Univariate analysis evidenced an association between mortality and HFNC ≥ 48 h (OR 2.16. 95% CI 1.087-4.287. p: 0.028). Such an association persisted in the multivariable analysis (OR 2.21. 95% CI 1.013-4.808. p: 0.046) after controlling for age, sex, comorbidities, basal severity of infection, and complications. This study also identified a significant increase in mortality after 36 h in HFNC (46.3%, p: 0.003). In patients with ARDS due to COVID-19, HFNC exposure ≥ 48 h prior to IMV is a factor associated with mortality after controlling multiple confounders. Physiological mechanisms for such an association are need to be defined.

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.

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.

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.

Effects of non-invasive respiratory supports on inspiratory effort in moderate-severe COVID-19 patients. A randomized physiological study

RATIONALE AND OBJECTIVE

Various forms of Non-invasive respiratory support (NRS) have been used during COVID-19, to treat Hypoxemic Acute Respiratory Failure (HARF), but it has been suggested that the occurrence of strenuous inspiratory efforts may cause Self Induced Lung Injury(P-SILI). The aim of this investigation was to record esophageal pressure, when starting NRS application, so as to better understand the potential risk of the patients in terms of P-SILI and ventilator induced lung injury (VILI).

METHODS AND MEASUREMENTS

21 patients with early de-novo respiratory failure due to COVID-19, underwent three 30 min trials applied in random order: high-flow nasal cannula (HFNC), continuous positive airway pressure (CPAP), and non-invasive ventilation (NIV). After each trial, standard oxygen therapy was reinstituted using a Venturi mask (VM). 15 patients accepted a nasogastric tube placement. Esophageal Pressure (ΔPes) and dynamic transpulmonary driving pressure (ΔPLDyn), together with the breathing pattern using a bioelectrical impedance monitor were recorded. Arterial blood gases were collected in all patients.

MAIN RESULTS

No statistically significant differences in breathing pattern and PaCO₂ were found. PaO₂/FiO₂ ratio improved significantly during NIV and CPAP vs VM. NIV was the only NRS to reduce significantly ΔPes vs. VM (-10,2 ±5 cmH20 vs -3,9 ±3,4). No differences were found in ΔPLDyn between NRS (10,2±5; 9,9±3,8; 7,6±4,3; 8,8±3,6 during VM, HFNC, CPAP and NIV respectively). Minute ventilation (Ve) was directly dependent on the patient's inspiratory effort, irrespective of the NRS applied. 14% of patients were intubated, none of them showing a reduction in ΔPes during NRS.

CONCLUSIONS

In the early phase of HARF due to COVID-19, the inspiratory effort may not be markedly elevated and the application of NIV and CPAP ameliorates oxygenation vs VM. NIV was superior in reducing ΔPes, maintaining ΔPLDyn within a range of potential safety.

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.

Risk Factors for Pulmonary Air Leak and Clinical Prognosis in Patients With COVID-19 Related Acute Respiratory Failure: A Retrospective Matched Control Study

Background

The role of excessive inspiratory effort in promoting alveolar and pleural rupture resulting in air leak (AL) in patients with SARS-CoV-2 induced acute respiratory failure (ARF) while on spontaneous breathing is undetermined.

Methods

Among all patients with COVID-19 related ARF admitted to a respiratory intensive care unit (RICU) and receiving non-invasive respiratory support, those developing an AL were and matched 1:1 [by means of PaO2/FiO2 ratio, age, body mass index-BMI and subsequent organ failure assessment (SOFA)] with a comparable population who did not (NAL group). Esophageal pressure (ΔP_es) and dynamic transpulmonary pressure (ΔP_L) swings were compared between groups. Risk factors affecting AL onset were evaluated. The composite outcome of ventilator-free-days (VFD) at day 28 (including ETI, mortality, tracheostomy) was compared between groups.

Results

Air leak and NAL groups (n = 28) showed similar ΔP_es, whereas AL had higher ΔP_L (20 [16–21] and 17 [11–20], p = 0.01, respectively). Higher ΔP_L (OR = 1.5 95%CI[1–1.8], p = 0.01), positive end-expiratory pressure (OR = 2.4 95%CI[1.2–5.9], p = 0.04) and pressure support (OR = 1.8 95%CI[1.1–3.5], p = 0.03), D-dimer on admission (OR = 2.1 95%CI[1.3–9.8], p = 0.03), and features suggestive of consolidation on computed tomography scan (OR = 3.8 95%CI[1.1–15], p = 0.04) were all significantly associated with AL. A lower VFD score resulted in a higher risk (HR = 3.7 95%CI [1.2–11.3], p = 0.01) in the AL group compared with NAL. RICU stay and 90-day mortality were also higher in the AL group compared with NAL.

Conclusion

In spontaneously breathing patients with COVID-19 related ARF, higher levels of ΔP_L, blood D-dimer, NIV delivery pressures and a consolidative lung pattern were associated with AL onset.

Nasal pressure swings as the measure of inspiratory effort in spontaneously breathing patients with de novo acute respiratory failure

Background

Excessive inspiratory effort could translate into self-inflicted lung injury, thus worsening clinical outcomes of spontaneously breathing patients with acute respiratory failure (ARF). Although esophageal manometry is a reliable method to estimate the magnitude of inspiratory effort, procedural issues significantly limit its use in daily clinical practice. The aim of this study is to describe the correlation between esophageal pressure swings (ΔP_es) and nasal (ΔP_nos) as a potential measure of inspiratory effort in spontaneously breathing patients with de novo ARF.

Methods

From January 1, 2021, to September 1, 2021, 61 consecutive patients with ARF (83.6% related to COVID-19) admitted to the Respiratory Intensive Care Unit (RICU) of the University Hospital of Modena (Italy) and candidate to escalation of non-invasive respiratory support (NRS) were enrolled. Clinical features and tidal changes in esophageal and nasal pressure were recorded on admission and 24 h after starting NRS. Correlation between ΔP_es and ΔP_nos served as primary outcome. The effect of ΔP_nos measurements on respiratory rate and ΔP_es was also assessed.

Results

ΔP_es and ΔP_nos were strongly correlated at admission (R² = 0.88, p < 0.001) and 24 h apart (R² = 0.94, p < 0.001). The nasal plug insertion and the mouth closure required for ΔP_nos measurement did not result in significant change of respiratory rate and ΔP_es. The correlation between measures at 24 h remained significant even after splitting the study population according to the type of NRS (high-flow nasal cannulas [R² = 0.79, p < 0.001] or non-invasive ventilation [R² = 0.95, p < 0.001]).

Conclusions

In a cohort of patients with ARF, nasal pressure swings did not alter respiratory mechanics in the short term and were highly correlated with esophageal pressure swings during spontaneous tidal breathing. ΔP_nos might warrant further investigation as a measure of inspiratory effort in patients with ARF.

Trial registration: NCT03826797. Registered October 2016.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03938-w.

Monitoring respiratory mechanics by oscillometry in COVID-19 patients receiving non-invasive respiratory support

Background

Non-invasive ventilation (NIV) has been increasingly used in COVID-19 patients. The limited physiological monitoring and the unavailability of respiratory mechanic measures, usually obtainable during invasive ventilation, is a limitation of NIV for ARDS and COVID-19 patients management.

Objectives

This pilot study was aimed to evaluate the feasibility of non-invasively monitoring respiratory mechanics by oscillometry in COVID-19 patients with moderate-severe acute respiratory distress syndrome (ARDS) receiving NIV.

Method

15 COVID-19 patients affected by moderate-severe ARDS at the RICU (Respiratory Intensive Care Unit) of the University hospital of Cattinara, Trieste, Italy were recruited. Patients underwent oscillometry tests during short periods of spontaneous breathing between NIV sessions.

Results

Oscillometry proved to be feasible, reproducible and well-tolerated by patients. At admission, 8 of the 15 patients showed oscillometry parameters within the normal range which further slightly improved before discharge. At discharge, four patients had still abnormal respiratory mechanics, not exclusively linked to pre-existing respiratory comorbidities. Lung mechanics parameters were not correlated with oxygenation.

Conclusions

Our results suggest that lung mechanics provide complementary information for improving patients phenotyping and personalisation of treatments during NIV in COVID 19 patients, especially in the presence of respiratory comorbidities where deterioration of lung mechanics may be less coupled with changes in oxygenation and more difficult to identify. Oscillometry may provide a valuable tool for monitoring lung mechanics in COVID 19 patients receiving NIV.

Different Methods to Improve the Monitoring of Noninvasive Respiratory Support of Patients with Severe Pneumonia/ARDS Due to COVID-19: An Update

The latest guidelines for the hospital care of patients affected by coronavirus disease 2019 (COVID-19)-related acute respiratory failure have moved towards the widely accepted use of noninvasive respiratory support (NIRS) as opposed to early intubation at the pandemic onset. The establishment of severe COVID-19 pneumonia goes through different pathophysiological phases that partially resemble typical acute respiratory distress syndrome (ARDS) and have been categorized into different clinical-radiological phenotypes. These can variably benefit on the application of external positive end-expiratory pressure (PEEP) during noninvasive mechanical ventilation, mainly due to variable levels of lung recruitment ability and lung compliance during different phases of the disease. A growing body of evidence suggests that intense respiratory effort producing excessive negative pleural pressure swings (Ppl) plays a critical role in the onset and progression of lung and diaphragm damage in patients treated with noninvasive respiratory support. Routine respiratory monitoring is mandatory to avoid the nasty continuation of NIRS in patients who are at higher risk for respiratory deterioration and could benefit from early initiation of invasive mechanical ventilation instead. Here we propose different monitoring methods both in the clinical and experimental settings adapted for this purpose, although further research is required to allow their extensive application in clinical practice. We reviewed the needs and available tools for clinical-physiological monitoring that aims at optimizing the ventilatory management of patients affected by acute respiratory distress syndrome due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection.

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.

Pathophysiology of coronavirus-19 disease acute lung injury

PURPOSE OF REVIEW

More than 230 million people have tested positive for severe acute respiratory syndrome-coronavirus-2 infection globally by September 2021. The infection affects primarily the function of the respiratory system, where ∼20% of infected individuals develop coronavirus-19 disease (COVID-19) pneumonia. This review provides an update on the pathophysiology of the COVID-19 acute lung injury.

RECENT FINDINGS

In patients with COVID-19 pneumonia admitted to the intensive care unit, the PaO2/FiO2 ratio is typically <26.7 kPa (200 mmHg), whereas lung volume appears relatively unchanged. This hypoxaemia is likely determined by a heterogeneous mismatch of pulmonary ventilation and perfusion, mainly associated with immunothrombosis, endothelialitis and neovascularisation. During the disease, lung weight, elastance and dead space can increase, affecting respiratory drive, effort and dyspnoea. In some severe cases, COVID-19 pneumonia may lead to irreversible pulmonary fibrosis.

SUMMARY

This review summarises the fundamental pathophysiological features of COVID-19 in the context of the respiratory system. It provides an overview of the key clinical manifestations of COVID-19 pneumonia, including gas exchange impairment, altered pulmonary mechanics and implications of abnormal chemical and mechanical stimuli. It also critically discusses the clinical implications for mechanical ventilation therapy.

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.

Role of total lung stress on the progression of early COVID-19 pneumonia

Purpose

We investigated if the stress applied to the lung during non-invasive respiratory support may contribute to the coronavirus disease 2019 (COVID-19) progression.

Methods

Single-center, prospective, cohort study of 140 consecutive COVID-19 pneumonia patients treated in high-dependency unit with continuous positive airway pressure (n = 131) or non-invasive ventilation (n = 9). We measured quantitative lung computed tomography, esophageal pressure swings and total lung stress.

Results

Patients were divided in five subgroups based on their baseline PaO₂/FiO₂ (day 1): non-CARDS (median PaO₂/FiO₂ 361 mmHg, IQR [323–379]), mild (224 mmHg [211–249]), mild-moderate (173 mmHg [164–185]), moderate-severe (126 mmHg [114–138]) and severe (88 mmHg [86–99], p < 0.001). Each subgroup had similar median lung weight: 1215 g [1083–1294], 1153 [888–1321], 968 [858–1253], 1060 [869–1269], and 1127 [937–1193] (p = 0.37). They also had similar non-aerated tissue fraction: 10.4% [5.9–13.7], 9.6 [7.1–15.8], 9.4 [5.8–16.7], 8.4 [6.7–12.3] and 9.4 [5.9–13.8], respectively (p = 0.85).

Treatment failure of CPAP/NIV occurred in 34 patients (24.3%). Only three variables, at day one, distinguished patients with negative outcome: PaO₂/FiO₂ ratio (OR 0.99 [0.98–0.99], p = 0.02), esophageal pressure swing (OR 1.13 [1.01–1.27], p = 0.032) and total stress (OR 1.17 [1.06–1.31], p = 0.004). When these three variables were evaluated together in a multivariate logistic regression analysis, only the total stress was independently associated with negative outcome (OR 1.16 [1.01–1.33], p = 0.032).

Conclusions

In early COVID-19 pneumonia, hypoxemia is not linked to computed tomography (CT) pathoanatomy, differently from typical ARDS. High lung stress was independently associated with the failure of non-invasive respiratory support.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-021-06519-7.