Lung Recruitment Research Articles

Positive end-expiratory pressure, or the perennial conundrum surrounding lung recruitment.

Positive end-expiratory pressure, or the perennial conundrum surrounding lung recruitment.

Changes in stroke volume induced by lung recruitment maneuver can predict fluid responsiveness during intraoperative lung-protective ventilation in prone position

BackgroundThe present study aimed to evaluate the reliability of hemodynamic changes induced by lung recruitment maneuver (LRM) in predicting stroke volume (SV) increase after fluid loading (FL) in prone position.MethodsThirty patients undergoing spine surgery in prone position were enrolled. Lung-protective ventilation (tidal volume, 6–7 mL/kg; positive end-expiratory pressure, 5 cmH2O) was provided to all patients. LRM (30 cmH2O for 30 s) was performed. Hemodynamic variables including mean arterial pressure (MAP), heart rate, SV, SV variation (SVV), and pulse pressure variation (PPV) were simultaneously recorded before, during, and at 5 min after LRM and after FL (250 mL in 10 min). Receiver operating characteristic curves were generated to evaluate the predictability of SVV, PPV, and SV decrease by LRM (ΔSVLRM) for SV responders (SV increase after FL > 10%). The gray zone approach was applied for ΔSVLRM.ResultsAreas under the curve (AUCs) for ΔSVLRM, SVV, and PPV to predict SV responders were 0.778 (95% confidence interval: 0.590–0.909), 0.563 (0.371–0.743), and 0.502 (0.315–0.689), respectively. The optimal threshold for ΔSVLRM was 30% (sensitivity, 92.3%; specificity, 70.6%). With the gray zone approach, the inconclusive values ranged 25 to 75% for ΔSVLRM (including 50% of enrolled patients).ConclusionIn prone position, LRM-induced SV decrease predicted SV increase after FL with higher reliability than traditional dynamic indices. On the other hand, considering the relatively large gray zone in this study, future research is needed to further improve the clinical significance.Trial registrationUMIN Clinical Trial Registry UMIN000027966. Registered 28th June 2017.

OLA strategy for ARDS: Its effect on mortality depends on achieved recruitment (PaO2/FiO2) and mechanical power. Systematic review and meta-analysis with meta-regression

ObjectiveThe “Open Lung Approach” (OLA), that includes high levels of positive end-expiratory pressure coupled with limited tidal volumes, is considered optimal for adult patients with ARDS. However, many previous meta-analyses have shown only marginal benefits of OLA on mortality but with statistical heterogeneity. It is crucial to identify the most likely moderators of this effect.To determine the effect of OLA strategy on mortality of ventilated ARDS patients. We hypothesized that the degree of recruitment achieved in the control group (PaO2/FiO2 ratio on day 3 of ventilation), and the difference in Mechanical Power (MP) or Driving Pressure (DP) between experimental and control groups will be the most likely sources of heterogeneity. DesignA Systematic Review and Meta-analysis was performed according to PRISMA statement and registered in PROSPERO database. We searched only for randomized controlled trials (RCTs). GRADE guidelines were used for rating the quality of evidence. Publication bias was assessed. For the Meta-analysis, we used a Random Effects Model. Sources of heterogeneity were explored with Meta-Regression, using a priori proposed set of possible moderators. For model comparison, Akaike's Information Criterion with the finite sample correction (AICc) was used. SettingNot applicable. PatientsFourteen RCTs were included in the study. InterventionsNot applicable. Main variables of interestNot applicable. ResultsEvidence of publication bias was detected, and quality of evidence was downgraded. Pooled analysis did not show a significant difference in the 28-day mortality between OLA strategy and control groups. Overall risk of bias was low. The analysis detected statistical heterogeneity. The two “best” explicative meta-regression models were those that used control PaO2/FiO2 on day 3 and difference in MP between experimental and control groups. The DP and MP models were highly correlated. ConclusionsThere is no clear benefit of OLA strategy on mortality of ARDS patients, with significant heterogeneity among RCTs. Mortality effect of OLA is mediated by lung recruitment and mechanical power.

Positive end-expiratory pressure, or the perennial conundrum surrounding lung recruitment

Positive end-expiratory pressure, or the perennial conundrum surrounding lung recruitment

Atelectasis and lung recruitment in pediatric anesthesia: An educational review.

General anesthesia is associated with development of pulmonary atelectasis. Children are more vulnerable to the development and adverse effects of atelectasis. We review the physiology and risk factors for the development of atelectasis in pediatric patients under general anesthesia. We discuss the clinical significance of atelectasis, the use and value of recruitment maneuvers, and other techniques available to minimize lung collapse. This review demonstrates the value of a recruitment maneuver, maintaining positive end-expiratory pressure (PEEP) until extubation and lowering FiO2 where possible in the daily practice of the pediatric anesthetist.

Perioperative Pulmonary Atelectasis: Part II. Clinical Implications.

The development of pulmonary atelectasis is common in the surgical patient. Pulmonary atelectasis can cause various degrees of gas exchange and respiratory mechanics impairment during and after surgery. In its most serious presentations, lung collapse could contribute to postoperative respiratory insufficiency, pneumonia, and worse overall clinical outcomes. A specific risk assessment is critical to allow clinicians to optimally choose the anesthetic technique, prepare appropriate monitoring, adapt the perioperative plan, and ensure the patient's safety. Bedside diagnosis and management have benefited from recent imaging advancements such as lung ultrasound and electrical impedance tomography, and monitoring such as esophageal manometry. Therapeutic management includes a broad range of interventions aimed at promoting lung recruitment. During general anesthesia, these strategies have consistently demonstrated their effectiveness in improving intraoperative oxygenation and respiratory compliance. Yet these same intraoperative strategies may fail to affect additional postoperative pulmonary outcomes. Specific attention to the postoperative period may be key for such outcome impact of lung expansion. Interventions such as noninvasive positive pressure ventilatory support may be beneficial in specific patients at high risk for pulmonary atelectasis (e.g., obese) or those with clinical presentations consistent with lung collapse (e.g., postoperative hypoxemia after abdominal and cardiothoracic surgeries). Preoperative interventions may open new opportunities to minimize perioperative lung collapse and prevent pulmonary complications. Knowledge of pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should provide the basis for current practice and help to stratify and match the intensity of selected interventions to clinical conditions.

Effects of Positive End-Expiratory Pressure on Lung Recruitment, Respiratory Mechanics, and Intracranial Pressure in Mechanically Ventilated Brain-Injured Patients.

Background: The pathophysiological effects of positive end-expiratory pressure (PEEP) on respiratory mechanics, lung recruitment, and intracranial pressure (ICP) in acute brain-injured patients have not been completely elucidated. The primary aim of this study was to assess the effects of PEEP augmentation on respiratory mechanics, quantitative computed lung tomography (qCT) findings, and its relationship with ICP modifications. Secondary aims included the assessment of the correlations between different factors (respiratory mechanics and qCT features) with the changes of ICP and how these factors at baseline may predict ICP response after greater PEEP levels.Methods: A prospective, observational study included mechanically ventilated patients with acute brain injury requiring invasive ICP and who underwent two-PEEP levels lung CT scan. Respiratory system compliance (Crs), arterial partial pressure of carbon dioxide (PaCO2), mean arterial pressure (MAP), data from qCT and ICP were obtained at PEEP 5 and 15 cmH2O.Results: Sixteen examinations (double PEEP lung CT and neuromonitoring) in 15 patients were analyzed. The median age of the patients was 54 years (interquartile range, IQR = 39–65) and 53% were men. The median Glasgow Coma Scale (GCS) at intensive care unit (ICU) admission was 8 (IQR = 3–12). Median alveolar recruitment was 2.5% of total lung weight (−1.5 to 4.7). PEEP from 5 to 15 cmH2O increased ICP [median values from 14.0 (11.2–17.5) to 23.5 (19.5–26.8) mmHg, p < 0.001, respectively]. The amount of recruited lung tissue on CT was inversely correlated with the change (Δ) in ICP (rho = −0.78; p = 0.0006). Additionally, ΔCrs (rho = −0.77, p = 0.008), ΔPaCO2 (rho = 0.81, p = 0.0003), and ΔMAP (rho = −0.64, p = 0.009) were correlated with ΔICP. Baseline Crs was not predictive of ICP response to PEEP.Conclusions: The main factors associated with increased ICP after PEEP augmentation included reduced Crs, lower MAP and lung recruitment, and increased PaCO2, but none of these factors was able to predict, at baseline, ICP response to PEEP. To assess the potential benefits of increased PEEP in patients with acute brain injury, hemodynamic status, respiratory mechanics, and lung morphology should be taken into account.

Lung Response to a Higher Positive End-Expiratory Pressure in Mechanically Ventilated Patients With COVID-19

BackgroundInternational guidelines suggest using a higher (> 10 cm H2O) positive end-expiratory pressure (PEEP) in patients with moderate-to-severe ARDS due to COVID-19. However, even if oxygenation generally improves with a higher PEEP, compliance, and Paco2 frequently do not, as if recruitment was small.Research QuestionIs the potential for lung recruitment small in patients with early ARDS due to COVID-19?Study Design and MethodsForty patients with ARDS due to COVID-19 were studied in the supine position within 3 days of endotracheal intubation. They all underwent a PEEP trial, in which oxygenation, compliance, and Paco2 were measured with 5, 10, and 15 cm H2O of PEEP, and all other ventilatory settings unchanged. Twenty underwent a whole-lung static CT scan at 5 and 45 cm H2O, and the other 20 at 5 and 15 cm H2O of airway pressure. Recruitment and hyperinflation were defined as a decrease in the volume of the non-aerated (density above −100 HU) and an increase in the volume of the over-aerated (density below −900 HU) lung compartments, respectively.ResultsFrom 5 to 15 cm H2O, oxygenation improved in 36 (90%) patients but compliance only in 11 (28%) and Paco2 only in 14 (35%). From 5 to 45 cm H2O, recruitment was 351 (161-462) mL and hyperinflation 465 (220-681) mL. From 5 to 15 cm H2O, recruitment was 168 (110-202) mL and hyperinflation 121 (63-270) mL. Hyperinflation variably developed in all patients and exceeded recruitment in more than half of them.InterpretationPatients with early ARDS due to COVID-19, ventilated in the supine position, present with a large potential for lung recruitment. Even so, their compliance and Paco2 do not generally improve with a higher PEEP, possibly because of hyperinflation.

A CASE OF NINE WEEKS ON VENO-VENOUS EXTRACORPOREAL MEMBRANE OXYGENATION FOR COVID-19

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: COVID-19 was declared a public health emergency by the World Health Organization in January 2020. The development of acute respiratory distress syndrome (ARDS) due to COVID-19 has high mortality. We present a case of 9 weeks of veno-venous extracorporeal membrane oxygenation (VV ECMO) for COVID-19 ARDS. CASE PRESENTATION: A 47-year-old male with a positive COVID-19 test 5 days prior to admission presented to the emergency department with dyspnea. He was severely hypoxemic prompting admission to the intensive care unit and treatment with high flow nasal canula, glucocorticoids, inhaled nitric oxide and remdesivir. He remained hypoxemic requiring intubation. His hypoxemia worsened despite maximal ventilatory support, proning and paralysis. He was evaluated and considered a candidate for VV ECMO. His cannulation strategy included right femoral vein drainage and right internal jugular (IJ) return cannulas. Anticoagulation for the ECMO circuit was held at 5 days due to bloody secretions and hematochezia. He was started on early nutritional supplementation with high protein tube feeds. Physical therapy included tilting to an upright position with a special bed and passive range of motion exercises. His course was complicated by prolonged respiratory failure requiring tracheostomy, nosocomial pneumonias, bilateral pneumothoraces, right IJ line associated venous thrombosis and bacteremia with native mitral valve endocarditis. At 60 days, his lung compliance began to improve. His ECMO gas sweep and delivered fractional oxygen percentage were incrementally decreased as his native lung gas exchange improved. He was decannulated after 65 days on ECMO. He had continued improvement in physical and respiratory function, including tracheostomy decannulation. He was discharged home after 12 weeks on 1-liter nasal cannula and currently uses oxygen with exertion with minimal dyspnea. DISCUSSION: VV ECMO in traditional ARDS has shown to improve mortality in patients with respiratory failure. Respiratory failure in patients with COVID-19 ARDS tends to be more protracted than traditional ARDS. COVID-19 ARDS patients have higher lung compliance, ventilatory ratio and lung recruitment early in the course. They can have persistent lung diffusion and radiologic abnormalities at 3 months with lingering pulmonary effects post-infection. COVID-19 ARDS patients who require ECMO eventually lose lung compliance. Improvement in tidal volume is the first sign of lung recovery in traditional and COVID-19 ARDS. CONCLUSIONS: VV ECMO is a viable option for the management of COVID-19 ARDS. Longer ECMO support in COVID-19 patients is expected given the difference in lung physiology compared to traditional ARDS and further research into VV ECMO and COVID-19 ARDS is needed. REFERENCE #1: Combes, Alain et al. "ECMO for severe ARDS: systematic review and individual patient data meta-analysis." Intensive care medicine vol. 46,11 (2020): 2048-2057. REFERENCE #2: Haudebourg, Anne-Fleur et al. "Respiratory Mechanics of COVID-19- versus Non-COVID-19-associated Acute Respiratory Distress Syndrome." American journal of respiratory and critical care medicine vol. 202,2 (2020): 287-290. REFERENCE #3: Combes, Alain et al. "Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome." The New England journal of medicine vol. 378,21 (2018): 1965-1975. DISCLOSURES: No relevant relationships by Kathy Chan, source=Web Response No relevant relationships by Hekmat Nasiri, source=Web Response No relevant relationships by Sudhir Rajan, source=Web Response

USE OF HIGH FREQUENCY PERCUSSIVE VENTILATION FOR ARDS

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: High frequency percussive ventilation (HFPV) is a method of ventilation that delivers biphasic percussive microvolumes in a time-cycled, pressure limited fashion. The goal is to increase recruitment of alveoli burdened by secretions or atelectasis to improve gas exchange for those failing conventional ventilation. HFPV has been utilized in the acute inhalation injury population; however, its use has spread to the medical community as a rescue method in acute respiratory distress (ARDS) patients. CASE PRESENTATION: A 24-year-old male with a past medial history of type 2 diabetes, obstructive sleep apnea, and obesity presented to the Emergency Department for worsening epigastric pain, nausea, and vomiting. He was ill appearing with diffuse abdominal pain, guarding, and rebound. Pertinent labs included a lipase of 3,600 U/L and triglycerides of 1,700 mg/dL. Computed tomography (CT) of the abdomen and pelvis revealed severe pancreatic edema with a non-enhancing pancreatic tail concerning for necrosis. He was admitted to the Intensive Care Unit and started on crystalloid infusion and continuous insulin. He developed progressive tachypnea and ultimately required intubation for severe hypoxemia. He further decompensated with worsening fevers and hypotension, requiring initiation of broad-spectrum antibiotics and vasopressors. Despite the insulin infusion, the patient's triglycerides increased to 9,500 mg/dL and he was started on therapeutic plasma exchange. Echocardiogram did not reveal evidence of left ventricular dysfunction. Chest x-ray showed worsening bilateral pulmonary infiltrates suggestive of ARDS. Despite a lung-protective, volume-controlled method of ventilation, the patient continued to exhibit high plateau and driving pressures. Given his significantly distended abdomen and high bladder pressures, he was unable to tolerate prone positioning. PaO2/FiO2 ratio (P/F ratio) was as low as 91. Subsequently he underwent cannulation for veno-venous extracorporeal membrane oxygenation (VV-ECMO). His secretion burden remained high and CT chest revealed dense atelectasis. He was then switched to HFPV for better secretion management and improvement in oxygenation. After 48 hours of HFPV, he had significant improvement in his atelectasis on CT chest and P/F ratio. After eight days, he was decannulated from VV-ECMO and later extubated. DISCUSSION: Our patient experienced known severe complications from hypertriglyceride-induced pancreatitis. His ARDS improved robustly with HFPV with VV-ECMO support. In centers with experience with this type of ventilation, it can be a powerful tool for patients suffering from inhalation injury, high-secretion pneumonias, and ARDS. CONCLUSIONS: Though HFPV does not have a dense volume of data supporting its use in ARDS, in the appropriately selected patient it can provide a safe and efficient way of improving lung recruitment, gas exchange, and potentially outcomes. REFERENCE #1: Godet T, Jabaudon M, Blondonnet R, Tremblay A, Audard J, Rieu B, Pereira B, Garcier JM, Futier E, Constantin JM. High frequency percussive ventilation increases alveolar recruitment in early acute respiratory distress syndrome: an experimental, physiological and CT scan study. Crit Care. 2018 Jan 11;22(1):3. REFERENCE #2: Spapen H, Borremans M, Diltoer M. Van Gorp V, Nguyen D, Honore P. (2014). High-frequency percussive ventilation in severe acute respiratory distress syndrome: A single center experience. Journal of Anesthesiology Clinical Pharmacology. 30(1):65-70. DISCLOSURES: No relevant relationships by Alaynna Kears, source=Web Response No relevant relationships by Christopher Lenivy, source=Web Response No relevant relationships by Kaitlyn Musco, source=Web Response No relevant relationships by Roshun Sangani, source=Web Response No relevant relationships by Daniel Schwed Lustgarten, source=Web Response

Electrical Impedance Tomography Monitoring of Bronchoalveolar Lavage in Patients With Acute Respiratory Distress Syndrome.

The impact of bronchoalveolar lavage on regional ventilation in mechanically ventilated patients with acute respiratory distress syndrome has rarely been described. Our objectives were use electrical impedance tomography to describe lung impedance variation post bronchoalveolar lavage and identify morphologic patterns according to respiratory failure severity. Monocenter physiologic study on mechanically ventilated patients. University medical ICU. After a recruitment maneuver, tidal impedance variation distributions (a surrogate for impact of bronchoalveolar lavage on tidal volume distribution), end-expiratory lung impedance (correlated with end-expiratory lung volume and used to quantify postbronchoalveolar lavage derecruitment), respiratory mechanics, and blood gases were recorded before and over 6 hours post bronchoalveolar lavage with Pao2 to the Fio2 ratio. Patients were grouped according to their prebronchoalveolar lavage, that is, Pao2 to the Fio2 ratio less than 200 or greater than or equal to 200. Twenty-one patients (median [interquartile range] age 55 yr [50-58 yr]; 13 males), 13 with Pao2 to the Fio2 ratio less than 200, were included. Unlike that latter group, bronchoalveolar lavage significantly impacted tidal impedance variation distribution in patients with Pao2 to the Fio2 ratio greater than or equal to 200, with a ventilation shift to the contralateral lung (from 54% to 42% in the bronchoalveolar lavage side), which persisted up to 6 hours post bronchoalveolar lavage. Similarly, end-expiratory lung impedance was less distributed in the bronchoalveolar lavage side post procedure of patients with Pao2 to the Fio2 ratio greater than or equal to 200, but the difference did not reach statistical significance (p = 0.09). As reported for tidal impedance variation, end-expiratory lung impedance distribution in patients with severe or moderate acute respiratory distress syndrome did not change significantly during the 6 hours post bronchoalveolar lavage. Although bronchoalveolar lavage effects on gas exchanges were minor in all patients, static compliance in patients with Pao2 to the Fio2 ratio greater than or equal to 200 was significantly lower post bronchoalveolar lavage (p = 0.04). The negative impact of bronchoalveolar lavage on regional ventilation, which persisted at least 6 hours, appeared to be more profound in patients with normal lung function or mild acute respiratory distress syndrome. In contrast, regional ventilation, lung recruitment, respiratory mechanics, and gas exchanges were modestly impacted by the bronchoalveolar lavage in patients with severe or moderate acute respiratory distress syndrome. That finding is reassuring and supports not summarily proscribing bronchoalveolar lavage for the most severely ill with acute respiratory distress syndrome.

Mechanical ventilation in COVID‐19: A physiological perspective

New Findings What is the topic of this review? This review presents the fundamental concepts of respiratory physiology and pathophysiology, with particular reference to lung mechanics and the pulmonary phenotype associated with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and subsequent coronavirus disease 2019 (COVID‐19) pneumonia. What advances does it highlight? The review provides a critical summary of the main physiological aspects to be considered for safe and effective mechanical ventilation in patients with severe COVID‐19 in the intensive care unit. Severe respiratory failure from coronavirus disease 2019 (COVID‐19) pneumonia not responding to non‐invasive respiratory support requires mechanical ventilation. Although ventilation can be a life‐saving therapy, it can cause further lung injury if airway pressure and flow and their timing are not tailored to the respiratory system mechanics of the individual patient. The pathophysiology of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection can lead to a pattern of lung injury in patients with severe COVID‐19 pneumonia typically associated with two distinct phenotypes, along a temporal and pathophysiological continuum, characterized by different levels of elastance, ventilation‐to‐perfusion ratio, right‐to‐left shunt, lung weight and recruitability. Understanding the underlying pathophysiology, duration of symptoms, radiological characteristics and lung mechanics at the individual patient level is crucial for the appropriate choice of mechanical ventilation settings to optimize gas exchange and prevent further lung injury. By critical analysis of the literature, we propose fundamental physiological and mechanical criteria for the selection of ventilation settings for COVID‐19 patients in intensive care units. In particular, the choice of tidal volume should be based on obtaining a driving pressure < 14 cmH2O, ensuring the avoidance of hypoventilation in patients with preserved compliance and of excessive strain in patients with smaller lung volumes and lower lung compliance. The level of positive end‐expiratory pressure (PEEP) should be informed by the measurement of the potential for lung recruitability, where patients with greater recruitability potential may benefit from higher PEEP levels. Prone positioning is often beneficial and should be considered early. The rationale for the proposed mechanical ventilation settings criteria is presented and discussed.

Comparing the Benefits of Titrated PEEP vs Low PEEP in Terms of Mortality in Patients Suffering from Acute Respiratory Distress Syndrome

Objective: To compare the benefits of titrated PEEP vs low PEEP in terms of mortality in patients suffering from acute respiratory distress syndrome&#x0D; Study Design: Randomized clinical trial&#x0D; Place and Duration of Study: Intensive care unit (ICU) of Nishtar Hospital Multan over a period of January 2017 to January 2018.&#x0D; Methodology: Patients were randomly divided into two groups LP group and TP group. TP group received fluids and neuromuscular blockers. Lung recruitment maneuver was done with incremental PEEP level and in the second time by a decremental PEEP maneuver. If levels of PaO2 and FIO2 were same or increasing during one day we stared to decrease the PEEP of 2cm Hg for every 8 hours. .&#x0D; Results: Of the outcome variables, numbers of death within 28 days were significantly higher in the low PEEP group (p-value 0.045 and 0.022, respectively). Development of pneumothorax requiring drainage and incidence of barotrauma within the first 7 days was significantly less in the titrated PEEP group. During the first 28 days, more number of patients in the titrated PEEP group had ventilator free days.&#x0D; Conclusion: In our study we find that the deaths within 28 days, development of pneumothorax requiring drainage and incidence of barotrauma within the first 7 days were significantly higher in the low PEEP group.

Wavelet Transform Image Enhancement Algorithm-Based Evaluation of Lung Recruitment Effect and Nursing of Acute Respiratory Distress Syndrome by Ultrasound Image.

This study aimed to analyze the application of ultrasound images of lung recruitment (LR) nursing treatment guided by positive-end expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS). An ultrasound image enhancement algorithm (UIEA) wavelet transform (WT) was constructed, and the soft threshold (ST) and adjacent region average (ARA) were introduced for simulation comparison. In addition, the signal-to-noise ratio (SNR), peak signal-to-noise ratio (PSNR), and running time were undertaken as the evaluation indexes. The WT algorithm was applied to the ultrasound images of 85 ARDS patients before and after PEEP recruitment. The mean artery pressure (MAP), heart rate (HR), and central venous pressure (CVP), peak inspiratory pressure (Ppeak), mean inspiratory pressure (Pmean), dynamic lung compliance (DLC), PCO2, and PaO2/FiO2 of the patients were recorded before and after the LR. The results showed that the signal-to-noise ratio (SNR) (19.67 ± 3.15 dB) and PSNR (23.08 ± 2.08 dB) of the images enhanced by the WT algorithm were much higher than those of ST (13.88 ± 2.74 dB and 14.62 ± 1.76 dB, respectively) and ARA (14.96 ± 3.06 dB and 15.11 ± 1.94 dB, respectively), while the running time was in adverse (P < 0.05); the HR and CVP of patients after LR nursing treatment were increased greatly, while the MAP was in the opposite case (P < 0.05); after LR nursing treatment, Ppeak, Pmean, DLC, PCO2, and PaO2/FiO2 of the patient were significantly greater than those before the LR, and the difference was statistically significant (P < 0.05). In short, the WT algorithm not only enhanced the quality of ultrasound images but also shortened the running time and improved the processing efficiency. PEEP LR nursing treatment could effectively improve the vascular patency, cardiac ejection capacity, and DLC in patients with ARDS, thereby increasing the airway pressure and maintaining the unobstructed expiration.

Use of Lung Ultrasound for Assessment of Lung Recruitment Maneuvers in Patients with ARDS

BACKGROUND: Positive pressure mechanical ventilation is a non-physiological intervention that saves lives but is not free of important side effects. It invariably results in different degrees of collapse of small airways. Recruitment maneuver (RM) aims to resolve lung collapse by a brief and controlled increment in airway pressure while positive end-expiratory pressure (PEEP) afterward keeps the lungs open. Therefore, ideally RM and PEEP selection must be individualized and this can only be done when guided by specific monitoring tools since lung’s opening and closing pressures vary among patients with different lung conditions. AIM: The aim of this study was to explore the clinical value of ultrasonic monitoring in the assessment of pulmonary recruitment and the best PEEP. PATIENTS AND METHODS: This study was conducted on 120 patients, 30 were excluded as in whom lung collapse cannot be confirmed then the rest were 90 patients from whom another 25 patients excluded as they were hemodynamically unstable the rest 65 patients were divided into two groups: Group A: Included 50 mechanically ventilated patients with ARDS, underwent lung recruitment using lung ultrasound and Group B: Included 15 mechanically ventilated patients with ARDS, underwent lung recruitment using oxygenation index. This prospective study was held at many critical care departments around Egypt. RESULTS: We noticed that lung recruitment in both groups significantly increased Pao2/Fio2 ratio immediately after recruitment compared with basal state and also significantly increase dynamic compliance compared with basal state. The increase in PF ratio immediately was significantly more in ultrasound group than in oxygenation group. Furthermore, we noticed that that P/F ratio 12 h after recruitment decreased compared with P/F ratio immediately after recruitment but significantly increased compared with basal state before recruitment and also we found that the increase in P/F ratio 12 h after recruitment was more significantly in lung ultrasound group than in oxygenation group. Furthermore, we noticed that lung recruitment (both lung ultrasound and oxygenation group) significantly increase RV function using TAPSE compared with basal state. Both opening pressure and optimal PEEP were significantly higher in lung ultrasound group than in oxygenation group. In our study, opening pressure was 37.28 ± 1.25 in lung ultrasound group and was 36.67±0.98 in oxygenation group and optimal PEEP was 14.64 ± 1.08 in lung ultrasound group and was 13.13 ± 0.74 in oxygenation group. CONCLUSION: Lung US is an effective mean of evaluating and guiding alveolar recruitment in ARDS. Compared with the maximal oxygenation–guided method, the protocol for reaeration in US-guided lung recruitment achieved a higher opening pressure, resulted in greater improvements in lung aeration, and substantially reduced lung heterogeneity in ARDS.

Transoesophageal Ultrasound Assessment of Lung Aeration in Patients With Acute Respiratory Distress Syndrome.

Introduction: The effect of positive end-expiratory pressure (PEEP) depends closely on the potential for lung recruitment. Bedside assessment of lung recruitability is crucial for personalized lung-protective mechanical ventilation in acute respiratory distress syndrome (ARDS) patients.Methods: We developed a transoesophageal lung ultrasound (TE-LUS) method in which a quantitative (computer-assisted) grayscale determination served as a guide to PEEP-induced lung recruitment. The method is based on the following hypothesis: when the PEEP increases, inflation of the recruited alveoli leads to significant changes in the air/water ratio. Normally ventilated areas are hypoechoic because the ultrasound waves are weakly reflected while poorly aerated areas or non-aerated areas are hyperechoic. We calculated the TE-LUS re-aeration score (RAS) as the ratio of the mean gray scale level at low PEEP to that value at high PEEP for the lower and upper lobes. A RAS > 1 indicated an increase in ventilated area. We used this new method to detect changes in ventilation in patients with a low (<0.5) vs. high (≥0.5) recruitment-to-inflation (R/I) ratio (i.e., the ratio between the recruited lung compliance and the respiratory system compliance at low PEEP).Results: We included 30 patients with moderate-to-severe ARDS. In patients with a high R/I ratio, the TE-LUS RAS was significantly higher in the lower lobes than in the upper lobes (1.20 [1.12–1.63] vs. 1.05 [0.89–1.38]; p = 0.05). Likewise, the TE-LUS RAS in the lower lobes was significantly higher in the high R/I group than in the low R/I group (1.20 [1.12–1.63] vs. 1.07 [1.00–1.20]; p = 0.04).Conclusion: The increase in PEEP induces a substantial gain in the ventilation detected by TE-LUS of poorly or non-aerated lower lobes (dependent lung regions), especially in patients with a high R/I ratio.

Intra-operative open-lung ventilatory strategy reduces postoperative complications after laparoscopic colorectal cancer resection: A randomised controlled trial.

BACKGROUNDThe role of the positive end-expiratory pressure (PEEP) and lung recruitment manoeuvre (LRM) combination (termed open-lung strategy, OLS) during intra-operative mechanical ventilation is not clear.OBJECTIVETo determine whether an open-lung strategy constituting medium PEEP (6–8 cmH2O) and repeated LRMs protects against postoperative complications in at-risk patients undergoing laparoscopic colorectal cancer resection under low-tidal-volume ventilation.DESIGNA prospective, assessor-blinded, randomised controlled trial.SETTINGSingle university-affiliated hospital, conducted from January 2017 to October 2018.PATIENTSA total of 280 patients at risk of pulmonary complications, scheduled for laparoscopic colorectal cancer resection under general anaesthesia and low-tidal-volume (6–8 ml kg−1 predicted body weight) ventilation.INTERVENTIONThe patients were randomly assigned (1 : 1) to a PEEP of 6–8 cmH2O with LRMs repeated every 30 min (OLS group) or a zero PEEP without LRMs (non-OLS group).MAIN OUTCOME MEASURESThe primary outcome was a composite of major pulmonary and extrapulmonary complications occurring within 7 days after surgery. The secondary outcomes included intra-operative potentially harmful hypotension and the need for vasopressors.RESULTSA total of 130 patients from each group were included in the primary outcome analysis. Primary outcome events occurred in 24 patients (18.5%) in the OLS group and 43 patients (33.1%) in the non-OLS group [relative risk, 0.46; 95% confidence interval (CI), 0.26 to 0.82; P = 0.009). More patients in the OLS group developed potentially harmful hypotension (OLS vs. non-OLS, 15% vs. 4.3%; P = 0.004) and needed vasopressors (25% vs. 8.6%; P < 0.001).CONCLUSIONAmong at-risk patients undergoing laparoscopic colorectal cancer resection under low-tidal-volume ventilation, an open-lung strategy with a PEEP of 6–8 cmH2O and repeated LRMs reduced postoperative complications compared with a strategy using zero PEEP without LRMs. Of note, LRMs should be used with caution in patients with haemodynamic instability.TRIAL REGISTRATIONClinicaltrials.gov identifier: NCT03160144.

Myeloid-IL4Rα is an indispensable link in IL-33-ILCs-IL-13-IL4Rα axis of eosinophil recruitment in murine lungs

Increased eosinophil recruitment is a hallmark feature of eosinophilic disorders. Here, we delineated the key molecular and cellular players involved in physiological eosinophilic recruitment during normal postnatal lung development in mice. Physiological eosinophilic recruitment was consistently present in 7-, 10-, and 15-day-old neonatal mice, but not in 42-day-old mice. This feature was completely abolished in interleukin 33 (IL-33)-, interleukin 2 receptor gamma chain (IL2rγ)-, and interleukin 4 receptor alpha (IL4Rα)-knockout mice, but not in recombination activating gene 1 (Rag1)-knockout mice demonstrating an indispensable role for IL-33, innate lymphoid cells (ILCs), and IL4Rα in eosinophil recruitment. Interestingly, myeloid-specific IL4Rα-deficient (mye-IL4Rα−/−) mice had significantly reduced eosinophilia in the airspaces that was associated with reduced levels of IL-4 and IL-5 in the bronchoalveolar lavage fluid (BALF). Further, we tested the effect of myeloid-specific IL4Rα deficiency on IL-13-induced eosinophil recruitment into adult lung airspaces. Eosinophil recruitment into the airspaces was elevated in IL-13-treated WT mice but not in IL-13-treated mye-IL4Rα−/− mice. Consistent with the degree of eosinophilia, the BALF levels of eosinophil recruitment-associated cytokines were significantly elevated in IL-13-treated WT but not in IL-13-treated mye-IL4Rα−/− mice. These data establish that myeloid-IL4Rα is an indispensable component of the IL-33-ILCsIL-13-IL4Rα axis of eosinophil recruitment.

Personalized Positive End-Expiratory Pressure and Tidal Volume in Acute Respiratory Distress Syndrome: Bedside Physiology-Based Approach.

OBJECTIVES:Positive end-expiratory pressure and tidal volume may have a key role for the outcome of patients with acute respiratory distress syndrome. The variety of acute respiratory distress syndrome phenotypes implies personalization of those settings. To guide personalized positive end-expiratory pressure and tidal volume, physicians need to have an in-depth understanding of the physiologic effects and bedside methods to measure the extent of these effects. In the present article, a step-by-step physiologic approach to select personalized positive end-expiratory pressure and tidal volume at the bedside is described.DATA SOURCES:The present review is a critical reanalysis of the traditional and latest literature on the topic.STUDY SELECTION:Relevant clinical and physiologic studies on positive end-expiratory pressure and tidal volume setting were reviewed.DATA EXTRACTION:Reappraisal of the available physiologic and clinical data.DATA SYNTHESIS:Positive end-expiratory pressure is aimed at stabilizing alveolar recruitment, thus reducing the risk of volutrauma and atelectrauma. Bedside assessment of the potential for lung recruitment is a preliminary step to recognize patients who benefit from higher positive end-expiratory pressure level. In patients with higher potential for lung recruitment, positive end-expiratory pressure could be selected by physiology-based methods balancing recruitment and overdistension. In patients with lower potential for lung recruitment or in shock, positive end-expiratory pressure could be maintained in the 5–8 cm H2O range. Tidal volume induces alveolar recruitment and improves gas exchange. After setting personalized positive end-expiratory pressure, tidal volume could be based on lung inflation (collapsed lung size) respecting safety thresholds of static and dynamic lung stress. Positive end-expiratory pressure and tidal volume could be kept stable for some hours in order to allow early recognition of changes in the clinical course of acute respiratory distress syndrome but also frequently reassessed to avoid crossing of safety thresholds.CONCLUSIONS:The setting of personalized positive end-expiratory pressure and tidal volume based on sound physiologic bedside measures may represent an effective strategy for treating acute respiratory distress syndrome patients.

Utilization of Airway Pressure Release Ventilation as a Rescue Strategy in COVID-19 Patients: A Retrospective Analysis.

Background:Airway Pressure Release Ventilation (APRV) is a pressure controlled intermittent mandatory mode of ventilation characterized by prolonged inspiratory time and high mean airway pressure. Several studies have demonstrated that APRV can improve oxygenation and lung recruitment in patients with Acute Respiratory Distress Syndrome (ARDS). Although most patients with COVID-19 meet the Berlin criteria for ARDS, hypoxic respiratory failure due to COVID-19 may differ from traditional ARDS as patients often present with severe, refractory hypoxemia and significant variation in respiratory system compliance. To date, no studies investigating APRV in this patient population have been published. The aim of this study was to evaluate the effectiveness of APRV as a rescue mode of ventilation in critically ill patients diagnosed with COVID-19 and refractory hypoxemia.Methods:We conducted a retrospective analysis of patients admitted with COVID-19 requiring invasive mechanical ventilation who were treated with a trial of APRV for refractory hypoxemia. PaO2/FIO2 (P/F ratio), ventilatory ratio and ventilation outputs before and during APRV were compared.Results:APRV significantly improved the P/F ratio and decreased FIO2 requirements. PaCO2 and ventilatory ratio were also improved. There was an increase in tidal volume per predicted body weight during APRV and a decrease in total minute ventilation. On multivariate analysis, higher inspiratory to expiratory ratio (I: E) and airway pressure were associated with greater improvement in P/F ratio.Conclusions:APRV may improve oxygenation, alveolar ventilation and CO2 clearance in patients with COVID-19 and refractory hypoxemia. These effects are more pronounced with higher airway pressure and inspiratory time.