Advanced Point-of-care Bedside Monitoring for Acute Respiratory Failure

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.

Analgosedation practice during noninvasive respiratory supports: Results from an Italian survey

PURPOSE

There are currently no established guidelines pertaining the application of analgosedation strategies for patients undergoing Noninvasive Respiratory Supports (NRSs) for acute respiratory failure treatment. The Italian Society of Anesthesia Analgesia Resuscitation and Intensive Care (SIAARTI) conducted a nation-wide survey to describe the current clinical practice in the management of analgosedation during NRSs.

METHODS

This is a nationwide online survey, involving Italian anesthesiologist-intensivists, developed by experts affiliated with SIAARTI. Invitations to participate were distributed via emails and social networks. Data were collected over a period of three months (March 16 to May 10, 2024).

RESULTS

Two hundred and seventy-seven full responses were collected. Most respondents were attending physician (83 %), with <10 years of ICU experience (56 %) and work in ICU medical department (75 %). In terms of optimizing the NRS success, 80 % of respondents used a pharmacological strategy and 50 % of respondents did not use a non-pharmacological strategy. Dexmedetomidine was the most commonly administered drug (82 %), followed by morphine and remifentanil. Additionally, 33 % of respondents reported using a combination of dexmedetomidine and remifentanil as part of their pharmacological strategy during NRSs. Concerning the motivations for analgosedation use during NRSs, over 80 % of respondents aimed to improve patient-ventilator interaction, more than 60 % focused on reducing patient anxiety and dyspnea, 59 % sought for having a lower respiratory rate, and only 40 % prioritized pain reduction.

CONCLUSION

Sedation is frequently used in patients with acute respiratory failure undergoing NRSs. Current analgesic practices are becoming more standardized, with analgosedation strategies increasingly tailored to individual patient characteristics.

Monitoring effort and respiratory drive in patients with acute respiratory failure

PURPOSE OF REVIEW

Accurate monitoring of respiratory drive and inspiratory effort is crucial for optimizing ventilatory support during acute respiratory failure. This review evaluates current and emerging bedside methods for assessing respiratory drive and effort.

RECENT FINDINGS

While electrical activity of the diaphragm and esophageal pressure remain the reference standards for assessing respiratory drive and effort, their clinical utility is largely limited to research. At the bedside, airway occlusion maneuvers are the most useful tools: P0.1 is a reliable marker of drive and detects abnormal inspiratory efforts, while occlusion pressure (Pocc) may outperform P0.1 in identifying excessive effort. The Pressure-Muscle-Index (PMI) can help detecting insufficient inspiratory effort, though its accuracy depends on obtaining a stable plateau pressure. Other techniques, such as central venous pressure swings (ΔCVP), are promising but require further investigation. Emerging machine learning and artificial intelligence based algorithms could play a pivotal role in automated respiratory monitoring in the near future.

SUMMARY

Although Pes and EAdi remain reference methods, airway occlusion maneuvers are currently the most practical bedside tools for monitoring respiratory drive and effort. Noninvasive alternatives such as ΔCVP deserve further evaluation. Artificial intelligence and machine learning may soon provide automated solutions for bedside monitoring of respiratory drive and effort.

Navigating Heart-Lung Interactions in Mechanical Ventilation: Pathophysiology, Diagnosis, and Advanced Management Strategies in Acute Respiratory Distress Syndrome and Beyond

Patients in critical condition who require mechanical ventilation experience intricate interactions between their respiratory and cardiovascular systems. These complex interactions are crucial for clinicians to understand as they can significantly influence therapeutic decisions and patient outcomes. A deep understanding of heart-lung interactions is essential, particularly under the stress of mechanical ventilation, where the right ventricle plays a pivotal role and often becomes a primary concern. Positive pressure ventilation, commonly used in mechanical ventilation, impacts right and left ventricular pre- and afterload as well as ventricular interplay. The right ventricle is especially susceptible to these changes, and its function can be critically affected, leading to complications such as right heart failure. Clinicians must be adept at recognizing and managing these interactions to optimize patient care. This perspective will analyze this matter comprehensively, covering the pathophysiology of these interactions, the monitoring of heart-lung dynamics using the latest methods (including ECHO), and management and treatment strategies for related conditions. In particular, the analysis will delve into the efficacy and limitations of various treatment modalities, including pharmaceutical interventions, nuanced ventilator management strategies, and advanced devices such as extracorporeal membrane oxygenation (ECMO). Each approach will be examined for its impact on optimizing right ventricular function, mitigating complications, and ultimately improving patient outcomes in the context of mechanical ventilation.

Electrical Impedance Tomography-Based Evaluation of Anesthesia-Induced Development of Atelectasis in Obese Patients

Background/Objectives: The induction of general anesthesia leads to the development of atelectasis and redistribution of ventilation to non-dependent lung regions with subsequent impairment of gas exchange. However, it remains unclear how rapidly atelectasis occurs after the induction of anesthesia in obese patients. We therefore investigated the extent of atelectasis formation in obese patients in the first few minutes after the induction of general anesthesia and initiation of mechanical ventilation in the operating room. Methods: In 102 patients with morbid obesity (BMI ≥ 35 kg m-2) scheduled for laparoscopic intrabdominal surgery, induction of general anesthesia was performed while continuously monitoring regional pulmonary ventilation using electrical impedance tomography. Distribution of ventilation to non-dependent lung areas as a surrogate for atelectasis formation was determined by taking the mean value of five consecutive breaths for each minute starting five minutes before to five minutes after intubation. Ventilation inhomogeneity was assessed using the Global Inhomogeneity Index. Results: Median tidal volume in non-dependent lung areas was 58.3% before and 71.5% after intubation and increased by a median of 13.79% after intubation (p < 0.001). Median Global Inhomogeneity Index was 49.4 before and 71.4 after intubation and increased by a median of 21.99 units after intubation (p < 0.001). Conclusions: Atelectasis forms immediately after the induction of general anesthesia and increases the inhomogeneity of lung ventilation.

High-frequency percussive ventilation in acute respiratory failure

Introduction

High-frequency percussive ventilation (HFPV) is a ventilation mode characterised by high-frequency breaths. This study investigated the impact of HFPV on gas exchange and clinical outcomes in acute respiratory failure (ARF) patients during spontaneous breathing, noninvasive ventilation (NIV) and invasive mechanical ventilation (iMV).

Methods

This systematic review included randomised and nonrandomised studies up to August 2023. Inclusion criteria focused on adult ARF patients, HFPV application, comparisons with other ventilation modes, and outcomes related to oxygenation and clinical parameters. A pooled data analysis was performed comparing HFPV with iMV concerning gas exchange, pulmonary infection and mortality.

Results

Of the 51 identified records, 29 met the inclusion criteria. HFPV was safely and effectively applied to ARF patients during spontaneous breathing or NIV, improving oxygenation. For patients who underwent iMV, HFPV significantly enhanced oxygenation and the arterial partial pressure of carbon dioxide, reduced pulmonary infection occurrence and improved survival. Barotrauma rates were not elevated with HFPV, and haemodynamic stability remained unaffected. HFPV was also utilised in patients undergoing extracorporeal membrane oxygenation, resulting in improved lung recruitment and oxygenation.

Conclusion

HFPV had favourable effects on physiological and certain clinical outcomes in ARF patients. However, the overall evidence quality remains weak, necessitating large-scale randomised controlled trials for definitive conclusions.

Clinical implementation of advanced respiratory monitoring with esophageal pressure and electrical impedance tomography: results from an international survey and focus group discussion

BACKGROUND

Popularity of electrical impedance tomography (EIT) and esophageal pressure (Pes) monitoring in the ICU is increasing, but there is uncertainty regarding their bedside use within a personalized ventilation strategy. We aimed to gather insights about the current experiences and perceived role of these physiological monitoring techniques, and to identify barriers and facilitators/solutions for EIT and Pes implementation.

METHODS

Qualitative study involving (1) a survey targeted at ICU clinicians with interest in advanced respiratory monitoring and (2) an expert focus group discussion. The survey was shared via international networks and personal communication. An in-person discussion session on barriers, facilitators/solutions for EIT implementation was organized with an international panel of EIT experts as part of a multi-day EIT meeting. Pes was not discussed in-person, but we found the focus group results relevant to Pes as well. This was confirmed by the survey results and four additional Pes experts that were consulted.

RESULTS

We received 138 survey responses, and 26 experts participated in the in-person discussion. Survey participants had diverse background [physicians (54%), respiratory therapists (19%), clinical researchers (15%), and nurses (6%)] with mostly > 10 year ICU experience. 84% of Pes users and 74% of EIT users rated themselves as competent to expert users. Techniques are currently primarily used during controlled ventilation for individualization of PEEP (EIT and Pes), and for monitoring lung mechanics and lung stress (Pes). EIT and Pes are considered relevant techniques to guide ventilation management and is helpful for educating clinicians; however, 57% of EIT users and 37% of Pes users agreed that further validation is needed. Lack of equipment/materials, evidence-based guidelines, clinical protocols, and/or the time-consuming nature of the measurements are main reasons hampering Pes and EIT application. Identified facilitators/solutions to improve implementation include international guidelines and collaborations between clinicians/researcher and manufacturers, structured courses for training and use, easy and user-friendly devices and standardized analysis pipelines.

CONCLUSIONS

This study revealed insights on the role and implementation of advanced respiratory monitoring with EIT and Pes. The identified barriers, facilitators and strategies can serve as input for further discussions to promote the development of EIT-guided or Pes-guided personalized ventilation strategies.

A comparison of the effects of lung protective ventilation and conventional ventilation on the occurrence of atelectasis during laparoscopic surgery in young infants: a randomized controlled trial

Objective

This study utilized lung ultrasound to investigate whether lung protective ventilation reduces pulmonary atelectasis and improves intraoperative oxygenation in infants undergoing laparoscopic surgery.

Methods

Eighty young infants (aged 1-6 months) who received general anesthesia for more than 2 h during laparoscopic surgery were randomized into the lung protective ventilation group (LPV group) and the conventional ventilation group (control group). The LPV group received mechanical ventilation starting at 6 mL/kg tidal volume, 5 cmH2O PEEP, 60% inspired oxygen fraction, and half-hourly alveolar recruitment maneuvers. Control group ventilation began with 8-10 mL/kg tidal volume, 0 cmH2O PEEP, and 60% inspired oxygen fraction. Lung ultrasound was conducted five times-T1 (5 min post-intubation), T2 (5 min post-pneumoperitoneum), T3 (at the end of surgery), T4 (post-extubation), and T5 (prior to discharge from the PACU)-for each infant. Simultaneous arterial blood gas analysis was performed at T1, T2, T3, and T4.

Results

Statistically significant differences were observed in pulmonary atelectasis incidence, lung ultrasound scores, and the PaO2, PaCO2, PaO2/FiO2 ratios at T2, T3, and T4. However, at T5, no statistically significant differences were noted in terms of lung ultrasound scores (4.30 ± 1.87 vs. 5.00 ± 2.43, 95% CI: -1.67 to 0.27, p = 0.153) or the incidence of pulmonary atelectasis (32.5% vs. 47.5%, p = 0.171).

Conclusion

In infants aged 1-6 months, lung protective ventilation during laparoscopy under general anesthesia significantly reduced the incidence of pulmonary atelectasis and enhanced intraoperative oxygenation and dynamic lung compliance compared to conventional ventilation. However, these benefits did not persist; no differences were observed in lung ultrasound scores or the incidence of pulmonary atelectasis at PACU discharge.

Clinical trial registration

http://www.chictr.org.cn/, identifier: ChiCTR2200058653.

Monitoring lung recruitment

PURPOSE OF REVIEW

This review explores lung recruitment monitoring, covering techniques, challenges, and future perspectives.

RECENT FINDINGS

Various methodologies, including respiratory system mechanics evaluation, arterial bold gases (ABGs) analysis, lung imaging, and esophageal pressure (Pes) measurement are employed to assess lung recruitment. In support to ABGs analysis, the assessment of respiratory mechanics with hysteresis and recruitment-to-inflation ratio has the potential to evaluate lung recruitment and enhance mechanical ventilation setting. Lung imaging tools, such as computed tomography scanning, lung ultrasound, and electrical impedance tomography (EIT) confirm their utility in following lung recruitment with the advantage of radiation-free and repeatable application at the bedside for sonography and EIT. Pes enables the assessment of dorsal lung tendency to collapse through end-expiratory transpulmonary pressure. Despite their value, these methodologies may require an elevated expertise in their application and data interpretation. However, the information obtained by these methods may be conveyed to build machine learning and artificial intelligence algorithms aimed at improving the clinical decision-making process.

SUMMARY

Monitoring lung recruitment is a crucial component of managing patients with severe lung conditions, within the framework of a personalized ventilatory strategy. Although challenges persist, emerging technologies offer promise for a personalized approach to care in the future.

Complications during Veno-Venous Extracorporeal Membrane Oxygenation in COVID-19 and Non-COVID-19 Patients with Acute Respiratory Distress Syndrome

Background: Acute respiratory distress syndrome (ARDS) presents a significant challenge in critical care settings, characterized by compromised gas exchange, necessitating in the most severe cases interventions such as veno-venous extracorporeal membrane oxygenation (vv-ECMO) when conventional therapies fail. Critically ill ARDS patients on vv-ECMO may experience several complications. Limited data exist comparing complication rates between COVID-19 and non-COVID-19 ARDS patients undergoing vv-ECMO. This retrospective observational study aimed to assess and compare complications in these patient cohorts. Methods: We retrospectively analyzed the medical records of all patients receiving vv-ECMO for ARDS between March 2020 and March 2022. We recorded the baseline characteristics, the disease course and complication (barotrauma, bleeding, thrombosis) before and after ECMO cannulation, and clinical outcomes (mechanical ventilation and ECMO duration, intensive care unit, and hospital lengths of stay and mortalities). Data were compared between COVID-19 and non-COVID-19 patients. In addition, we compared survived and deceased patients. Results: Sixty-four patients were included. COVID-19 patients (n = 25) showed higher rates of pneumothorax (28% vs. 8%, p = 0.039) with subcutaneous emphysema (24% vs. 5%, p = 0.048) and longer non-invasive ventilation duration before vv-ECMO cannulation (2 [1; 4] vs. 0 [0; 1] days, p = <0.001), compared to non-COVID-19 patients (n = 39). However, complication rates and clinical outcomes post-vv-ECMO were similar between groups. Survival analysis revealed no significant differences in pre-vv-ECMO complications, but non-surviving patients had a trend toward higher complication rates and more pleural effusions post-vv-ECMO. Conclusions: COVID-19 patients on vv-ECMO exhibit higher pneumothorax rates with subcutaneous emphysema pre-cannulation; post-cannulation complications are comparable to non-COVID-19 patients.

Advanced Respiratory Monitoring during Extracorporeal Membrane Oxygenation

Advanced respiratory monitoring encompasses a diverse range of mini- or noninvasive tools used to evaluate various aspects of respiratory function in patients experiencing acute respiratory failure, including those requiring extracorporeal membrane oxygenation (ECMO) support. Among these techniques, key modalities include esophageal pressure measurement (including derived pressures), lung and respiratory muscle ultrasounds, electrical impedance tomography, the monitoring of diaphragm electrical activity, and assessment of flow index. These tools play a critical role in assessing essential parameters such as lung recruitment and overdistention, lung aeration and morphology, ventilation/perfusion distribution, inspiratory effort, respiratory drive, respiratory muscle contraction, and patient-ventilator synchrony. In contrast to conventional methods, advanced respiratory monitoring offers a deeper understanding of pathological changes in lung aeration caused by underlying diseases. Moreover, it allows for meticulous tracking of responses to therapeutic interventions, aiding in the development of personalized respiratory support strategies aimed at preserving lung function and respiratory muscle integrity. The integration of advanced respiratory monitoring represents a significant advancement in the clinical management of acute respiratory failure. It serves as a cornerstone in scenarios where treatment strategies rely on tailored approaches, empowering clinicians to make informed decisions about intervention selection and adjustment. By enabling real-time assessment and modification of respiratory support, advanced monitoring not only optimizes care for patients with acute respiratory distress syndrome but also contributes to improved outcomes and enhanced patient safety.

Intraoperative lung protection: strategies and their impact on outcomes

PURPOSE OF REVIEW

The present review summarizes the current knowledge and the barriers encountered when implementing tailoring lung-protective ventilation strategies to individual patients based on advanced monitoring systems.

RECENT FINDINGS

Lung-protective ventilation has become a pivotal component of perioperative care, aiming to enhance patient outcomes and reduce the incidence of postoperative pulmonary complications (PPCs). High-quality research has established the benefits of strategies such as low tidal volume ventilation and low driving pressures. Debate is still ongoing on the most suitable levels of positive end-expiratory pressure (PEEP) and the role of recruitment maneuvers. Adapting PEEP according to patient-specific factors offers potential benefits in maintaining ventilation distribution uniformity, especially in challenging scenarios like pneumoperitoneum and steep Trendelenburg positions. Advanced monitoring systems, which continuously assess patient responses and enable the fine-tuning of ventilation parameters, offer real-time data analytics to predict and prevent impending lung complications. However, their impact on postoperative outcomes, particularly PPCs, is an ongoing area of research.

SUMMARY

Refining protective lung ventilation is crucial to provide patients with the best possible care during surgery, reduce the incidence of PPCs, and improve their overall surgical journey.

Unexpected intensive care unit admission after surgery: impact on clinical outcome

PURPOSE OF REVIEW

This review is focused on providing insights into unplanned admission to the intensive care unit (ICU) after surgery, including its causes, effects on clinical outcome, and potential strategies to mitigate the strain on healthcare systems.

RECENT FINDINGS

Postoperative unplanned ICU admission results from a combination of several factors including patient's clinical status, the type of surgical procedure, the level of supportive care and clinical monitoring outside the ICU, and the unexpected occurrence of major perioperative and postoperative complications. The actual impact of unplanned admission to ICU after surgery on clinical outcome remains uncertain, given the conflicting results from several observational studies and recent randomized clinical trials. Nonetheless, unplanned ICU admission after surgery results a significant strain on hospital resources. Consequently, this issue should be addressed in hospital policy with the aim of implementing preoperative risk assessment and patient evaluation, effective communication, vigilant supervision, and the promotion of cooperative healthcare.

SUMMARY

Unplanned ICU admission after surgery is a multifactorial phenomenon that imposes a significant burden on healthcare systems without a clear impact on clinical outcome. Thus, the early identification of patient necessitating ICU interventions is imperative.

An Initial Investigation of Diaphragm Neurostimulation in Patients with Acute Respiratory Distress Syndrome

BACKGROUND

Lung protective ventilation aims at limiting lung stress and strain. By reducing the amount of pressure transmitted by the ventilator into the lungs, diaphragm neurostimulation offers a promising approach to minimize ventilator-induced lung injury. This study investigates the physiologic effects of diaphragm neurostimulation in acute respiratory distress syndrome (ARDS) patients. The hypothesis was that diaphragm neurostimulation would improve oxygenation, would limit the distending pressures of the lungs, and would improve cardiac output.

METHODS

Patients with moderate ARDS were included after 48 h of invasive mechanical ventilation and had a left subclavian catheter placed to deliver bilateral transvenous phrenic nerve stimulation. Two 60-min volume-controlled mechanical ventilation (control) sessions were interspersed by two 60-min diaphragm neurostimulation sessions delivered continually, in synchrony with the ventilator. Gas exchange, lung mechanics, chest electrical impedance tomography, and cardiac index were continuously monitored and compared across four sessions. The primary endpoint was the Pao2/fraction of inspired oxygen (Fio2) ratio at the end of each session, and the secondary endpoints were lung mechanics and hemodynamics.

RESULTS

Thirteen patients were enrolled but the catheter could not be inserted in one, leaving 12 patients for analysis. All sessions were conducted without interruption and well tolerated. The Pao2/Fio2 ratio did not change during the four sessions. Median (interquartile range) plateau pressure was 23 (20 to 31) cm H2O and 21 (17 to 25) cm H2O, driving pressure was 14 (12 to 18) cm H2O and 11 (10 to 13) cm H2O, and end-inspiratory transpulmonary pressure was 9 (5 to 11) cm H2O and 7 (4 to 11) cm H2O during mechanical ventilation alone and during mechanical ventilation + neurostimulation session, respectively. The dorsal/ventral ventilation surface ratio was 0.70 (0.54 to 0.91) when on mechanical ventilation and 1.20 (0.76 to 1.33) during the mechanical ventilation + neurostimulation session. The cardiac index was 2.7 (2.3 to 3.5) l · min-1 · m-2 on mechanical ventilation and 3.0 (2.4 to 3.9) l · min-1 · m-2 on mechanical ventilation + neurostimulation.

CONCLUSIONS

This proof-of-concept study showed the feasibility of short-term diaphragm neurostimulation in conjunction with mechanical ventilation in ARDS patients. Diaphragm neurostimulation was associated with positive effects on lung mechanics and on hemodynamics.

EDITOR’S PERSPECTIVE

Lung ultrasound and supine chest X-ray use in modern adult intensive care: mapping 30 years of advancement (1993-2023)

In critically ill patients with acute respiratory failure, thoracic images are essential for evaluating the nature, extent and progression of the disease, and for clinical management decisions. For this purpose, computed tomography (CT) is the gold standard. However, transporting patients to the radiology suite and exposure to ionized radiation limit its use. Furthermore, a CT scan is a static diagnostic exam for the thorax, not allowing, for example, appreciation of "lung sliding". Its use is also unsuitable when it is necessary to adapt or decide to modify mechanical ventilation parameters at the bedside in real-time. Therefore, chest X-ray and lung ultrasound are today's contenders for shared second place on the podium to acquire a thoracic image, with their specific strengths and limitations. Finally, electrical impedance tomography (EIT) could soon have a role, however, its assessment is outside the scope of this review. Thus, we aim to carry out the following points: (1) analyze the advancement in knowledge of lung ultrasound use and the related main protocols adopted in intensive care units (ICUs) over the latest 30 years, reporting the principal publications along the way, (2) discuss how and when lung ultrasound should be used in a modern ICU and (3) illustrate the possible future development of LUS.

Pressure- and time-dependent alveolar recruitment/derecruitment in a spatially resolved patient-specific computational model for injured human lungs

We present a novel computational model for the dynamics of alveolar recruitment/derecruitment (RD), which reproduces the underlying characteristics typically observed in injured lungs. The basic idea is a pressure- and time-dependent variation of the stress-free reference volume in reduced dimensional viscoelastic elements representing the acinar tissue. We choose a variable reference volume triggered by critical opening and closing pressures in a time-dependent manner from a straightforward mechanical point of view. In the case of (partially and progressively) collapsing alveolar structures, the volume available for expansion during breathing reduces and vice versa, eventually enabling consideration of alveolar collapse and reopening in our model. We further introduce a method for patient-specific determination of the underlying critical parameters of the new alveolar RD dynamics when integrated into the tissue elements, referred to as terminal units, of a spatially resolved physics-based lung model that simulates the human respiratory system in an anatomically correct manner. Relevant patient-specific parameters of the terminal units are herein determined based on medical image data and the macromechanical behavior of the lung during artificial ventilation. We test the whole modeling approach for a real-life scenario by applying it to the clinical data of a mechanically ventilated patient. The generated lung model is capable of reproducing clinical measurements such as tidal volume and pleural pressure during various ventilation maneuvers. We conclude that this new model is an important step toward personalized treatment of ARDS patients by considering potentially harmful mechanisms-such as cyclic RD and overdistension-and might help in the development of relevant protective ventilation strategies to reduce ventilator-induced lung injury (VILI).

Intraoperative individualization of positive-end-expiratory pressure through electrical impedance tomography or esophageal pressure assessment: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

This systematic review of randomized-controlled trials (RCTs) with meta-analyses aimed to compare the effects on intraoperative arterial oxygen tension to inspired oxygen fraction ratio (PaO2/FiO2), exerted by positive end-expiratory pressure (PEEP) individualized trough electrical impedance tomography (EIT) or esophageal pressure (Pes) assessment (intervention) vs. PEEP not tailored on EIT or Pes (control), in patients undergoing abdominal or pelvic surgery with an open or laparoscopic/robotic approach.

METHODS

PUBMED®, EMBASE®, and Cochrane Controlled Clinical trials register were searched for observational studies and RCTs from inception to the end of August 2022. Inclusion criteria were: RCTs comparing PEEP titrated on EIT/Pes assessment vs. PEEP not individualized on EIT/Pes and reporting intraoperative PaO2/FiO2. Two authors independently extracted data from the enrolled investigations. Data are reported as mean difference and 95% confidence interval (CI).

RESULTS

Six RCTs were included for a total of 240 patients undergoing general anesthesia for surgery, of whom 117 subjects in the intervention group and 123 subjects in the control group. The intraoperative mean PaO2/FiO2 was 69.6 (95%CI 32.-106.4 ) mmHg higher in the intervention group as compared with the control group with 81.4% between-study heterogeneity (p < 0.01). However, at meta-regression, the between-study heterogeneity diminished to 44.96% when data were moderated for body mass index (estimate 3.45, 95%CI 0.78-6.11, p = 0.011).

CONCLUSIONS

In patients undergoing abdominal or pelvic surgery with an open or laparoscopic/robotic approach, PEEP personalized by EIT or Pes allowed the achievement of a better intraoperative oxygenation compared to PEEP not individualized through EIT or Pes.

PROSPERO REGISTRATION NUMBER

CRD 42021218306, 30/01/2023.

Asymmetrical high-flow nasal cannula performs similarly to standard interface in patients with acute hypoxemic post-extubation respiratory failure: a pilot study

BACKGROUND

Standard high-flow nasal cannula (HFNC) is a respiratory support device widely used to manage post-extubation hypoxemic acute respiratory failure (hARF) due to greater comfort, oxygenation, alveolar recruitment, humidification, and reduction of dead space, as compared to conventional oxygen therapy. On the contrary, the effects of the new asymmetrical HFNC interface (Optiflow® Duet system (Fisher & Paykel, Healthcare, Auckland, New Zealand) is still under discussion. Our aim is investigating whether the use of asymmetrical HFNC interface presents any relevant difference, compared with the standard configuration, on lung aeration (as assessed by end-expiratory lung impedance (EELI) measured by electrical impedance tomography (EIT)), diaphragm ultrasound thickening fraction (TFdi) and excursion (DE), ventilatory efficiency (estimated by corrected minute ventilation (MV)), gas exchange, dyspnea, and comfort.

METHODS

Pilot physiological crossover randomized controlled study enrolling 20 adults admitted to the Intensive Care unit, invasively ventilated for at least 24 h, and developing post-extubation hARF, i.e., PaO2/set FiO2 < 300 mmHg during Venturi mask (VM) within 120 min after extubation. Each HFNC configuration was applied in a randomized 60 min sequence at a flow rate of 60 L/min.

RESULTS

Global EELI, TFdi, DE, ventilatory efficiency, gas exchange and dyspnea were not significantly different, while comfort was greater during asymmetrical HFNC support, as compared to standard interface (10 [7-10] and 8 [7-9], p-value 0.044).

CONCLUSIONS

In post-extubation hARF, the use of the asymmetrical HFNC, as compared to standard HFNC interface, slightly improved patient comfort without affecting lung aeration, diaphragm activity, ventilatory efficiency, dyspnea and gas exchange.

CLINICAL TRIAL NUMBER

ClinicalTrial.gov.

REGISTRATION NUMBER

NCT05838326 (01/05/2023).

NEW & NOTEWORTHY

The asymmetrical high-flow nasal cannula oxygen therapy (Optiflow® Duet system (Fisher & Paykel, Healthcare, Auckland, New Zealand) provides greater comfort as compared to standard interface; while their performance in term of lung aeration, diaphragm activity, ventilatory efficiency, dyspnea, and gas exchange is similar.

Effects of High-Flow Nasal Cannula on Right Heart Dysfunction in Patients with Acute-on-Chronic Respiratory Failure and Pulmonary Hypertension

High-flow nasal cannula (HFNC) has several benefits in patients affected by different forms of acute respiratory failure, based on its own mechanisms. We postulated that HFNC may have some advantages over conventional oxygen therapy (COT) on the heart function in patients with acute-on-chronic respiratory failure with concomitant pulmonary hypertension (PH). We therefore designed this retrospective observational study to assess if HFNC improves the right and left ventricle functions and morphologies, arterial blood gases (ABGs), and patients' dyspnea, compared to COT. We enrolled 17 hospitalized patients receiving HFNC, matched with 17 patients receiving COT. Echocardiographic evaluation was performed at the time of admission (baseline) and 10 days after (T10). HFNC showed significant improvements in right ventricular morphology and function, and a reduction in sPAP. However, there were no significant changes in the left heart measurements with HFNC application. Conversely, COT did not lead to any modifications in echocardiographic measurements. In both groups, oxygenation significantly improved from baseline to T10 (in the HFNC group, from 155 ± 47 to 204 ± 61 mmHg while in the COT group, from 157 ± 27 to 207 ± 27 mmHg; p < 0.0001 for both comparisons). In conclusion, these data suggest an improvement of oxygenation with both treatments; however, only HFNC was able to improve the right ventricular morphology and function after 10 days from the beginning of treatment in a small cohort of patients with acute-on-chronic respiratory failure with PH.

Reverse Triggered Breath during Pressure Support Ventilation and Neurally Adjusted Ventilatory Assist at Increasing Propofol Infusion

BACKGROUND

Reverse triggered breath (RTB) has been extensively described during assisted-controlled modes of ventilation. We aimed to assess whether RTB occurs during Pressure Support Ventilation (PSV) and Neurally Adjusted Ventilatory Assist (NAVA) at varying depths of propofol sedation.

METHODS

This is a retrospective analysis of a prospective crossover randomized controlled trial conducted in an Intensive Care Unit (ICU) of a university hospital. Fourteen intubated patients for acute respiratory failure received six trials of 25 minutes randomly applying PSV and NAVA at three different propofol infusions: awake, light, and deep sedation. We assessed the occurrence of RTBs at each protocol step. The incidence level of RTBs was determined through the RTB index, which was calculated by dividing RTBs by the total number of breaths triggered and not triggered.

RESULTS

RTBs occurred during both PSV and NAVA. The RTB index was greater during PSV than during NAVA at mild (1.5 [0.0; 5.3]% vs. 0.6 [0.0; 1.1]%) and deep (5.9 [0.7; 9.0]% vs. 1.7 [0.9; 3.5]%) sedation.

CONCLUSIONS

RTB occurs in patients undergoing assisted mechanical ventilation. The level of propofol sedation and the mode of ventilation may influence the incidence of RTBs.

Acoustic Lung Imaging Utilized in Continual Assessment of Patients with Obstructed Airway: A Systematic Review

Smart respiratory therapy is enabled by continual assessment of lung functions. This systematic review provides an overview of the suitability of equipment-to-patient acoustic imaging in continual assessment of lung conditions. The literature search was conducted using Scopus, PubMed, ScienceDirect, Web of Science, SciELO Preprints, and Google Scholar. Fifteen studies remained for additional examination after the screening process. Two imaging modalities, lung ultrasound (LUS) and vibration imaging response (VRI), were identified. The most common outcome obtained from eleven studies was positive observations of changes to the geographical lung area, sound energy, or both, while positive observation of lung consolidation was reported in the remaining four studies. Two different modalities of lung assessment were used in eight studies, with one study comparing VRI against chest X-ray, one study comparing VRI with LUS, two studies comparing LUS to chest X-ray, and four studies comparing LUS in contrast to computed tomography. Our findings indicate that the acoustic imaging approach could assess and provide regional information on lung function. No technology has been shown to be better than another for measuring obstructed airways; hence, more research is required on acoustic imaging in detecting obstructed airways regionally in the application of enabling smart therapy.

Ultrasound assessment of the respiratory system using diaphragm motion-volume indices

Background

Although previous studies have determined limit values of normality for diaphragm excursion and thickening, it would be beneficial to determine the normal diaphragm motion-to-inspired volume ratio that integrates the activity of the diaphragm and the quality of the respiratory system.

Methods

To determine the normal values of selected ultrasound diaphragm motion-volume indices, subjects with normal pulmonary function testing were recruited. Ultrasound examination recorded diaphragm excursion on both sides during quiet breathing and deep inspiration. Diaphragm thickness was also measured. The inspired volumes of the corresponding cycles were systematically recorded using a spirometer. The indices were calculated using the ratio excursion, or percentage of thickening, divided by the corresponding breathing volume. From this corhort, normal values and limit values for normality were determined. These measurements were compared to those performed on the healthy side in patients with hemidiaphragm paralysis because an increase in hemidiaphragm activity has been previously demonstated in such circumstances.

Results

A total of 122 subjects (51 women, 71 men) with normal pulmonary function were included in the study. Statistical analysis revealed that the ratio of excursion, or percentage of thickening, to inspired volume ratio significantly differed between males and females. When the above-mentioned indices using excursion were normalized by body weight, no gender differences were found. The indices differed between normal respiratory function subjects and patients with hemidiaphragm paralysis (27 women, 41 men). On the paralyzed side, the average ratio of the excursion divided by the inspired volume was zero. On the healthy side, the indices using the excursion and the percentage of thickening during quiet breathing or deep inspiration were significantly increased comparedto patients with normal lung function. According to the logistic regression analysis, the most relevant indice appeared to be the ratio of the excursion measured during quiet breathing to the inspired volume.

Conclusion

The normal values of the diaphragm motion-volume indices could be useful to estimate the performance of the respiratory system. Proposed indices appear suitable in a context of hyperactivity.

Effects of awake prone position vs. usual care on acute hypoxemic respiratory failure in patients with COVID-19: A systematic review and meta-analysis of randomized controlled trials

Background

Previous studies have shown that an awake prone position may be beneficial for the treatment of acute respiratory distress syndrome (ARDS) or acute hypoxic respiratory failure (AHRF) in patients with COVID-19, but the results are not consistent, especially in terms of oxygenation outcomes and intubation rate. This systematic review and meta-analysis assessed the effects of the awake prone position on AHRF in patients with COVID-19 with all randomized controlled trials (RCTs).

Methods

An extensive search of online databases, including MEDLINE, Embase, Web of Science, and Cochrane Central Register of Controlled Trials from 1 December 2019 to 30 October 2022, with no language restrictions was performed. This systematic review and meta-analysis are based on the PRISMA statement. We only included RCTs and used the Cochrane risk assessment tool for quality assessment.

Results

Fourteen RCTs fulfilled the selection criteria, and 3,290 patients were included. A meta-analysis found that patients in the awake prone position group had more significant improvement in the SpO₂/FiO₂ ratio [mean difference (MD): 29.76; 95% confidence interval (CI): 1.39-48.13; P = 0.001] compared with the usual care. The prone position also reduced the need for intubation [odd ratio (OR): 0.72; 95% CI: 0.61 to 0.84; P < 0.0001; I ² = 0%]. There was no significant difference in mortality, hospital length of stay, incidence of intensive care unit (ICU) admission, and adverse events between the two groups.

Conclusion

The awake prone position was a promising intervention method, which is beneficial to improve the oxygenation of patients with ARDS or AHRF caused by COVID-19 and reduce the need for intubation. However, the awake prone position showed no obvious advantage in mortality, hospital length of stay, incidence of ICU admission, and adverse events.

Systematic review registration

International Prospective Register of Systematic Reviews (PROSPERO), identifier: CRD42022367885.