Use Of Low Tidal Volumes Research Articles

Impact of Lower Tidal Volumes During One-Lung Ventilation: A 2022 Update of the Meta-analysis of Randomized Controlled Trials

To clarify the influence of lower tidal volume (4-7 mL/kg) compared with higher tidal volume (8-15 mL/kg) during one-lung ventilation (OLV) on gas exchange and postoperative clinical outcome. Meta-analysis of randomized trials. Thoracic surgery. Patients receiving OLV. Lower tidal volume during OLV. Primary outcome was PaO2-to-the oxygen fraction (PaO2/FIO2) ratio at the end of the surgery, after the reinstitution of two-lung ventilation. Secondary endpoints included perioperative changes in PaO2/FIO2 ratio and carbon dioxide (PaCO2) tension, airway pressure, the incidence of postoperative pulmonary complications, arrhythmia, and length of hospital stay. Seventeen randomized controlled trials (1,463 patients) were selected. Overall analysis showed that the use of low tidal volume during OLV was associated with a significantly higher PaO2/FIO2 ratio 15 minutes after the start of OLV and at the end of surgery (mean difference 33.7 mmHg [p=0.02] and mean difference 18.59 mmHg [p < 0.001], respectively). The low tidal volume also was associated with higher PaCO2 values 15 minutes and 60 minutes after the start of OLV and with lower airway pressure, which was maintained during two-lung ventilation after surgery. Moreover, the application of lower tidal volume was associated with fewer postoperative pulmonary complications (odds ratio 0.50; p < 0.001) and arrhythmias (odds ratio 0.58; p=0.009), with no difference in length of hospital stay. The use of lower tidal volume, a component of protective OLV, increases the PaO2/FIO2 ratio, reduces the incidence of postoperative pulmonary complications, and should be considered strongly in daily practice.

Challenges in ARDS Definition, Management, and Identification of Effective Personalized Therapies.

Over the last decade, the management of acute respiratory distress syndrome (ARDS) has made considerable progress both regarding supportive and pharmacologic therapies. Lung protective mechanical ventilation is the cornerstone of ARDS management. Current recommendations on mechanical ventilation in ARDS include the use of low tidal volume (VT) 4-6 mL/kg of predicted body weight, plateau pressure (PPLAT) < 30 cmH2O, and driving pressure (∆P) < 14 cmH2O. Moreover, positive end-expiratory pressure should be individualized. Recently, variables such as mechanical power and transpulmonary pressure seem promising for limiting ventilator-induced lung injury and optimizing ventilator settings. Rescue therapies such as recruitment maneuvers, vasodilators, prone positioning, extracorporeal membrane oxygenation, and extracorporeal carbon dioxide removal have been considered for patients with severe ARDS. Regarding pharmacotherapies, despite more than 50 years of research, no effective treatment has yet been found. However, the identification of ARDS sub-phenotypes has revealed that some pharmacologic therapies that have failed to provide benefits when considering all patients with ARDS can show beneficial effects when these patients were stratified into specific sub-populations; for example, those with hyperinflammation/hypoinflammation. The aim of this narrative review is to provide an overview on current advances in the management of ARDS from mechanical ventilation to pharmacological treatments, including personalized therapy.

High frequency oscillatory ventilation in adult patients with acute respiratory distress syndrome

Clinical trials on the use of mechanical ventilation in Acute Respiratory Distress Syndrome (ARDS) showed that use of low tidal volumes reduces the mortality significantly. Another approach that proved beneficial was to open the lung and keep it open. Theoretically, this can be best achieved with High Frequency Oscillatory Ventilation (HFOV). HFOV provides oscillations at three to ten Hertz in adults. Both inspiration and expiration are active. Gas exchange occurs even though the tidal volume delivered during each oscillation is less than the anatomical dead space. Furthermore, the potential adverse effects of the conventional ventilation such as alveolar overdistension, and repeated opening and collapse of alveoli are reduced. Many investigators have studied the potential benefit of HFOV in neonatal and paediatric population but the evidence for its use in adult population is limited. A lot of work is being done and two large ongoing trials OSCAR and OSCILLATE should give better idea regarding its use in adults. This review article mainly focuses on the principles and practices of HFOV in adults and current evidence regarding its use in adults.

Optimization of protective lung ventilation in thoracic surgery

Background: Today protective ventilation is the predominant ventilation methodology. It includes the use of low tidal volume, inspiratory pressure limitation, and the application of positive end-expiratory pressure. However, several retrospective studies have shown that tidal volume, inspiratory pressure, and Positive End-Expiratory Pressure (PEEP) are not associated with patients’ treatment outcomes, but could be associated only when they influence driving pressure.Objective: Optimization of the strategy of protective one-lung ventilation under the control of driving pressure, to reduce early postoperative respiratory complications in patients operated for lung cancer.Material and methods: A prospective controlled study was conducted on 110 patients undergoing extended anatomical lung resections with subsequent comparison of clinical results depending on the level of driving pressure during one-lung ventilation. Postoperative pulmonary complications based on the Melbourne scale that appeared within 3 days after surgery became the endpoint.Results: A correlation was established between the level of driving pressure and the level of PaO2 in the intraoperative period – high inverse (r = – 0.901). The greatest value in the development of postoperative respiratory failure is driving pressure, exceeding 15 cm of water (Odds ratio = 18.25). In the first 3 days, postoperative pulmonary complications, determined by the Melbourne group scale, occurred in 9 (8.2%) patients in whom the driving pressure exceeded 15 cm of water, and in 3 patients (2.7%) with a driving pressure level less than 15 cm of water (p = 0.016).Conclusion: Driving pressure excess with values of more than 15 cm of water significantly increases the incidence of postoperative pulmonary complications. Fixed PEEP will be inappropriate both high and low, and individualized PEEP titrated by CStat may reduce driving pressure and become the next step in protective one-lung ventilation.

A Comprehensive Review on the Management of ARDS among Pediatric Patients

Pediatric acute respiratory distress syndrome (PARDS) is a complex inflammatory syndrome of lungs leading to disruption of alveolar epithelial membrane barrier in the lungs. It includes varying age groups from infants to adolescents. PARDS definition has changed over decades as current definition is given by the Pediatric Acute Lung Injury Consensus Conference group. Although most of management principles are extrapolated from adult data, physiology of Acute Respiratory Distress Syndrome (ARDS) in children is different when compared to adults. The present review mainly focused on current evidence in the management of ARDS with emphasis to pediatric population. MeSH headings such as ARDS, positive end-expiratory pressure (PEEP), and lung protective ventilation were used for searching publications in PubMed, Embase, and SciELO. Publications were limited to human studies in the past 20 years. Core ventilatory strategies in PARDS include use of low-tidal volume, higher PEEP and acceptance of permissive hypercapnia and permissive hypoxemia. Supportive strategies such as restrictive fluid therapy, prone positioning, early enteral nutrition, and adequate analgosedation remain the mainstay of management of principles. As PARDS contains heterogeneous population, personalized mechanical ventilation under umbrella of lung protective ventilator strategies such as low-tidal volume ventilation, open lung strategy, acceptance of permissive hypercapnia, and permissive hypoxia is standard of care.

A Comprehensive Review of the Management of Acute Respiratory Distress Syndrome.

Acute respiratory distress syndrome (ARDS) is an inflammatory process in the lungs that induces non-hydrostatic protein-rich pulmonary edema.ARDS occurs in roughly halfof coronavirus disease 2019 (COVID-19) pneumonia patients, with most of them requiring intensive care. Oxygen saturation, partial pressure of the oxygen, and the fraction of the inspired oxygen are health indicators that may indicate a severe illnessnecessitating further investigation.As treatments have evolved, a typical pattern of ARDS has likewise evolved. In cases where mechanical ventilation is required, the use of low tidal volumes (<6 ml/kg ideal body weight) and airway pressures (plateau pressure <30 cmH2O) was recommended. For patients with moderate/severe ARDS (partial pressure to fractional inspired oxygenratio <20), prone positioning was recommended for at least 16 hours per day. By contrast, high-frequency oscillation was not recommended. The use of inhaled vasodilators was recommended in patients with persistent hypoxemia despite invasive ventilation and prone position until extracorporeal membrane oxygenation (ECMO). The use of a conservative fluid management strategy was suggested for all patients. Mechanical ventilation with high positive end-expiratory pressure (PEEP) was suggestedfor patients with ARDS with a ratio of arterial oxygen partial pressure to fractional inspired oxygen (PF) ratios. ECMO was suggested as an adjunct to protective mechanical ventilation for patients with severe ARDS. In the absence of adequate evidence, research recommendations were made for corticosteroids and extracorporeal carbon dioxide removal. While decades of research have been conducted, treatment options for underlying pathologies remain limited, and mechanical ventilation, which removes carbon dioxide from the body, remains essential to achieving better clinical outcomes. This review aims to identify the best ARDStreatments that are currently available.

ONE LUNG LUCY: PEDIATRIC ARDS IN A CHILD WITH LUNG AGENESIS

TYPE: Case Report TOPIC: Critical Care INTRODUCTION: Pediatric acute respiratory distress syndrome (PARDS) is a relatively common clinical problem in the PICU. However, ARDS in a pediatric patient with one lung is unique and not well defined. We present such a case and highlight challenges in management. CASE PRESENTATION: Our patient is a 14month old girl who presented to the ER in acute hypoxemic respiratory failure secondary to RSV bronchiolitis. Her past medical history is significant for left lung agenesis and supracardiac total anomalous pulmonary venous return (surgically repaired). She was admitted to the PICU and subsequently developed severe ARDS, with peak OI of 28. Single lung protective strategy was initially applied with the use of lower tidal volumes of 5-6 ml/kg and a PEEP of 6. Inhaled NO was employed and she was subsequently placed on tidal volumes of 8ml/kg and PEEP of 8 with subsequent improved lung compliance. She was successfully extubated after 2 weeks of MV. DISCUSSION: The Pediatric Acute Lung Injury Consensus Conference (PALICC) developed pediatric-specific definitions for ARDS and recommendations regarding treatment. Recommendations regarding management of patients with one lung who develop ARDS are lacking. One lung ventilation is a standard approach to facilitate surgical exposure for pulmonary and other thoracic surgeries, however it is not known whether ventilation strategies suggested by the anesthesia literature is applicable to PARDS. CONCLUSIONS: Our case presented challenges in providing adequate ventilation and oxygenation while minimizing further lung injury in a patient with one lung PARDS. Further study is needed to elucidate the optimum mechanical ventilation strategy. DISCLOSURE: Nothing to declare. KEYWORD: One Lung ARDS

Intraoperative protective mechanical ventilation in patients requiring emergency abdominal surgery: the multicentre prospective randomised IMPROVE-2 study protocol

IntroductionEmergency abdominal surgery is associated with a high risk of postoperative complications. One of the most serious is postoperative respiratory failure (PRF), with reported rates up to 20%–30% and attributable...

Practical Review of Mechanical Ventilation in Adults and Children in the Operating Room and Emergency Department

During general anesthesia, mechanical ventilation can cause pulmonary damage through mechanism of ventilator-induced lung injury, which is a major cause of post-operative pulmonary complications, which varies between 5 and 33% and increases the 30-day mortality of the surgical patient significantly. The aim of this review is to analyze different variables which played a key role in the safe application of mechanical ventilation in the operating room and emergency setting. Also, we wanted to analyze different types of the population that underwent intraoperative mechanical ventilation like obese patients, pediatric and adult population and different strategies such as one lung ventilation and ventilation in trendelemburg position. The peer-reviewed articles analyzed were selected according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) from Pubmed/Medline, Ovid/Wiley and Cochrane Library, combining key terms such as: "pulmonary post-operative complications", "protective ventilation", "alveolar recruitment maneuvers", "respiratory compliance", "intraoperative paediatric ventilation", "best peep", "types of ventilation". Among the 230 papers identified, 150 articles were selected, after title - abstract examination and removing the duplicates, resulting in 94 articles related to mechanical ventilation in operating room and emergency setting that were analyzed. Careful preoperative patient's evaluation and protective ventilation (i.e., use of low tidal volumes, adequate PEEP and alveolar recruitment maneuvers) has been shown to be effective not only in limiting alveolar de-recruitment, alveolar overdistension and lung damage, but also in reducing the onset of Pulmonary Post-operative Complications (PPCs). Mechanical ventilation is like "Janus Bi-front" because it is essential for surgical procedures, for the care of critical care patients and in life-threatening conditions, but it can be harmful to the patient if continued for a long time and where an excessive dose of oxygen is administered into the lungs. Low tidal volume is associated with a minor rate of PPCs and other complications and every complication can increase the length of Stay, adding cost to NHS between 1580 € and 1650 € per day in Europe and currently the prevention of PPCS is the only weapon that we possess.

New insights in mechanical ventilation and adjunctive therapies in ARDS

Patients with acute respiratory distress syndrome (ARDS) often require mechanical ventilation (MV) and may experience high morbidity and mortality. The ventilatory management of ARDS patients has changed over the years to mitigate the risk of ventilator-induced lung injury (VILI) and improve outcomes. Current recommended MV strategies include the use of low tidal volume (VT) at 4–6 mL/kg of predicted body weight (PBW) and plateau pressure (PPLAT ) below 27 cmH2O. Some patients achieve better outcomes with low VT than others, and several strategies have been proposed to individualize VT , including standardization for end-expiratory lung volume or inspiratory capacity. To date, no strategy for individualizing positive-end expiratory pressure (PEEP) based on oxygenation, recruitment, respiratory mechanics, or hemodynamics has proven superior for improving survival. Driving pressure, transpulmonary pressure, and mechanical power have been proposed as markers to quantify risk of VILI and optimize ventilator settings. Several rescue therapies, including neuromuscular blockade, prone positioning, recruitment maneuvers (RMs), vasodilators, and extracorporeal membrane oxygenation (ECMO), may be considered in severe ARDS. New ventilator strategies such as airway pressure release ventilation (APRV) and time-controlled adaptive ventilation (TCAV) have demonstrated potential benefits to reduce VILI, but further studies are required to evaluate their clinical relevance. This review aims to discuss the cornerstones of MV and new insights in ARDS ventilatory management, as well as their rationales, to guide the physician in an individually tailored rather than a fixed, sub-physiological approach. We recommend that MV be individualized based on physiological targets to achieve optimal ventilatory settings for each patient.

Impact of sex on use of low tidal volume ventilation in invasively ventilated ICU patients-A mediation analysis using two observational cohorts.

Studies in patients receiving invasive ventilation show important differences in use of low tidal volume (VT) ventilation (LTVV) between females and males. The aims of this study were to describe temporal changes in VT and to determine what factors drive the sex difference in use of LTVV. This is a posthoc analysis of 2 large longitudinal projects in 59 ICUs in the United States, the 'Medical information Mart for Intensive Care III' (MIMIC III) and the 'eICU Collaborative Research DataBase'. The proportion of patients under LTVV (median VT < 8 ml/kg PBW), was the primary outcome. Mediation analysis, a method to dissect total effect into direct and indirect effects, was used to understand which factors drive the sex difference. We included 3614 (44%) females and 4593 (56%) males. Median VT declined over the years, but with a persistent difference between females (from median 10.2 (9.1 to 11.4) to 8.2 (7.5 to 9.1) ml/kg PBW) vs. males (from median 9.2 [IQR 8.2 to 10.1] to 7.3 [IQR 6.6 to 8.0] ml/kg PBW) (P < .001). In females versus males, use of LTVV increased from 5 to 50% versus from 12 to 78% (difference, -27% [-29% to -25%]; P < .001). The sex difference was mainly driven by patients' body height and actual body weight (adjusted average causal mediation effect, -30% [-33% to -27%]; P < .001, and 4 [3% to 4%]; P < .001). While LTVV is increasingly used in females and males, females continue to receive LTVV less often than males. The sex difference is mainly driven by patients' body height and actual body weight, and not necessarily by sex. Use of LTVV in females could improve by paying more attention to a correct calculation of VT, i.e., using the correct body height.

ASPECTS OF INVASIVE MECHANICAL VENTILATION IN PATIENTS WITH ARDS CAUSED BY COVID-19

Mortality among patients with severe pneumonia and / or acute respiratory distress syndrome (ARDS) due to COVID-19 infection, who underwent mechanical ventilation (MV), is characterized by a fairly high frequency. However, despite the large number of patients receiving appropriate treatment, the question of choosing the optimal ventilation parameters remains poorly understood. In our article, we reviewed the available literature data on the indications for mechanical ventilation, parameters of MV, the need for prone-positioning of patients with ARDS caused by COVID-19 infection in intensive care units to identify unresolved issues.Despite the large number of publications about respiratory support in patients with severe coronavirus infection, there are only general principles regarding the indications for switching to invasive ventilation. Most authors identified the following clinical situations: progression of hypoxemia and / or respiratory failure but with constant oxygen support with increasing percentage of oxygen in the respiratory mixture, use of high-flow cannula or non-invasive ventilation for 1 hour without improvement; persistent hypercapnia, multiorgan failure, coma, high risk of aspiration, hemodynamic instability.According to most of the studies analyzed, the main components of the ventilation strategy should be based on the principles of pulmonary protective ventilation and include the use of low tidal volumes (Vt = 4-8 ml / kg of ideal body weight) and ventilation with plateau pressure Pplat &lt;30 cm H2O (plateau pressure - air pressure measured after an inspiratory pause of 0.5 s). At the same time, many authors recommend using prone position and high levels of positive end-expiratory pressure (PEEP) compared to low levels in patients with ARDS on the background of COVID-19.The approach to invasive mechanical ventilation in ARDS caused by SARS-CoV-2 still requires further research and answers to a number of questions.

COVID 19 infection: Pediatric perspectives.

The coronavirus disease 2019 (COVID‐19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has rapidly spread across the globe, causing innumerable deaths and a massive economic catastrophe. Exposure to household members with confirmed COVID‐19 is the most common source of infection among children. Children are just as likely as adults to get infected with SARS‐CoV‐2. Most children are asymptomatic and when symptoms occur, they are usually mild. Infants <12 months old are at a higher risk for severe or critical disease. COVID‐19 is diagnosed the same way in pediatric population as adults by testing specimen obtained from upper respiratory tract for nucleic acid amplification test (NAAT) using reverse transcriptase viral polymerase chain reaction (RT‐PCR). The common laboratory findings in hospitalized patient include leukopenia, lymphopenia, and increased levels of inflammatory markers. Chest X‐ray findings are variable and computed tomography scans of the chest may show ground glass opacities similar to adults or non‐specific findings. Prevention is the primary intervention strategy. Recently the U.S. Food and Drug Administration (FDA) has provided emergency authorization of the Pfizer‐BioNTech COVID‐19 vaccine and many other vaccine candidates are in the investigational stage. There is limited data in children on the use of antivirals, hydroxychloroquine, azithromycin, monoclonal antibody, and convalescent plasma. Oxygen therapy is required in hypoxic children (saturation <92%). Similar to adults, other measures to maintain oxygenation such as high flow nasal cannula, CPAP, or ventilatory support may be needed. Ventilatory management strategies should include use of low tidal volumes (5–6 cc/kg), high positive expiratory pressure, adequate sedation, paralysis, and prone positioning. Recently, a new entity associated with COVID‐19 called multisystem inflammatory syndrome in children (MIS‐C) has emerged. Clinical, laboratory, and epidemiological criteria are the basis for this diagnosis. Management options include ICU admission, steroids, intravenous gamma globulin, aspirin, anakinra, and anticoagulants. Vasoactive‐inotropic score (VIS) is used to guide vasopressor support.

Mechanical ventilation of the healthy lungs: lessons learned from recent trials.

Although there is clear evidence for benefit of protective ventilation settings [including low tidal volume and higher positive end-expiratory pressure (PEEP)] in patients with acute respiratory distress syndrome (ARDS), it is less clear what the optimal mechanical ventilation settings are for patients with healthy lungs. Use of low tidal volume during operative ventilation decreases postoperative pulmonary complications (PPC). In the critically ill patients with healthy lungs, use of low tidal volume is as effective as intermediate tidal volume. Use of higher PEEP during operative ventilation does not decrease PPCs, whereas hypotension occurred more often compared with use of lower PEEP. In the critically ill patients with healthy lungs, there are conflicting data regarding the use of a higher PEEP, which may depend on recruitability of lung parts. There are limited data suggesting that higher driving pressures because of higher PEEP contribute to PPCs. Lastly, use of hyperoxia does not consistently decrease postoperative infections, whereas it seems to increase PPCs compared with conservative oxygen strategies. In patients with healthy lungs, data indicate that low tidal volume but not higher PEEP is beneficial. Thereby, ventilation strategies differ from those in ARDS patients.

Pneumomediastinum and subcutaneous emphysema in COVID-19: barotrauma or lung frailty?

BackgroundIn mechanically ventilated acute respiratory distress syndrome (ARDS) patients infected with the novel coronavirus disease (COVID-19), we frequently recognised the development of pneumomediastinum and/or subcutaneous emphysema despite employing a protective mechanical ventilation strategy. The purpose of this study was to determine if the incidence of pneumomediastinum/subcutaneous emphysema in COVID-19 patients was higher than in ARDS patients without COVID-19 and if this difference could be attributed to barotrauma or to lung frailty.MethodsWe identified both a cohort of patients with ARDS and COVID-19 (CoV-ARDS), and a cohort of patients with ARDS from other causes (noCoV-ARDS).Patients with CoV-ARDS were admitted to an intensive care unit (ICU) during the COVID-19 pandemic and had microbiologically confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. NoCoV-ARDS was identified by an ARDS diagnosis in the 5 years before the COVID-19 pandemic period.ResultsPneumomediastinum/subcutaneous emphysema occurred in 23 out of 169 (13.6%) patients with CoV-ARDS and in three out of 163 (1.9%) patients with noCoV-ARDS (p<0.001). Mortality was 56.5% in CoV-ARDS patients with pneumomediastinum/subcutaneous emphysema and 50% in patients without pneumomediastinum (p=0.46).CoV-ARDS patients had a high incidence of pneumomediastinum/subcutaneous emphysema despite the use of low tidal volume (5.9±0.8 mL·kg−1 ideal body weight) and low airway pressure (plateau pressure 23±4 cmH2O).ConclusionsWe observed a seven-fold increase in pneumomediastinum/subcutaneous emphysema in CoV-ARDS. An increased lung frailty in CoV-ARDS could explain this finding more than barotrauma, which, according to its etymology, refers to high transpulmonary pressure.

Individualized lung protective ventilation vs. conventional ventilation during general anesthesia in laparoscopic total hysterectomy.

Laparoscopic total hysterectomy is performed by carbon dioxide insufflation, Trendelenburg position and mechanical ventilation of patients under general anesthesia. However, this may induce pulmonary atelectasis and/or hyperdistention of the lungs. Multiple studies have indicated that mechanical ventilation with the use of low tidal volumes, moderate positive end-expiratory pressure (PEEP) and regular alveolar recruitment maneuvers may improve post-operative outcomes. However, the benefits of an individualized level of PEEP have not been clearly established. In the present study, it was hypothesized that a moderate fixed PEEP may not suit all patients and an individually-titrated PEEP during anesthesia may improve the peri-operative pulmonary oxygenation function. The aim of the present study was to compare the pulmonary oxygenation function and post-operative pulmonary complications (PPCs) in patients receiving individualized lung-protective mechanical ventilation (LPV) vs. conventional ventilation (CV) during laparoscopic total hysterectomy. The present study was a randomized double-blinded clinical trial on 87 patients who were randomly divided to receive CV or protective ventilation (PV). An optimal individualized PEEP value was determined using a static pulmonary compliance-directed PEEP titration procedure. Pulmonary oxygenation function, serum inflammatory factors, including interleukin-8 and Clara cell protein 16, the incidence of PPCs and the post-operative length of stay were also determined. Patients in the PV group exhibited improved pulmonary oxygenation function during and after the operation. The total percentage of PPCs during the first 7 days after surgery was significantly lower in the PV group compared with those in the CV group. In conclusion, as compared to CV, intra-operative individualized LPV significantly improved pulmonary oxygenation function and reduced the incidence of PPCs during the first 7 days after laparoscopic total hysterectomy (Clinical trial registration no. ChiCTR1900027738).

Maintaining spontaneous ventilation during surgery—a review article

Mechanical ventilation is necessary during many surgical procedures, however a paradigm shift in ventilation has taken place in the past decades. There is convincing evidence that neuromuscular blockade and subsequent controlled mechanical ventilation applying intermittent positive pressure, also in patients with non-injured, healthy lungs, may impair the respiratory system, leading to postoperative pulmonary complications (PPCs), resulting in worse clinical outcome, prolonged hospitalization time and increased cost of hospital care. Multifactorial pathophysiology of ventilator induced lung injury (VILI) has been evaluated and a pulmonary protective ventilatory strategy [lung protective ventilation (LPV)], including the use of low tidal volumes [6 mL/kg, ideal body weight (IBW)], moderate or optimal levels of positive end-expiratory pressure (PEEP) and applying regular or targeted alveolar recruitment maneuvers (ARMs), has been developed. Recognizing the role of neuromuscular blockade during general anesthesia and even the importance of avoiding residual neuromuscular blockade in the early postoperative period regarding to postoperative respiratory impairment have become another, newer direction of research. Despite promising and convincing results of recent clinical trials, incidence of PPCs could not be reduced significantly and lung protective ventilation has remained to be a “hot topic” among researchers in the field of anesthesia and critical care. Maintaining spontaneous breathing during general anesthesia has some pathophysiological rationale worth to be dealt with, because it may be one of the options for further improvement. Physiology, advantages, disadvantages and potential role of spontaneous breathing during surgery as compared to intermittent positive pressure ventilation will be described in this article.

Extracorporeal carbon dioxide removal requirements for ultraprotective mechanical ventilation: Mathematical model predictions

Extracorporeal carbon dioxide (CO2) removal (ECCO2R) facilitates the use of low tidal volumes during protective or ultraprotective mechanical ventilation when managing patients with acute respiratory distress syndrome (ARDS); however, the rate of ECCO2R required to avoid hypercapnia remains unclear. We calculated ECCO2R rate requirements to maintain arterial partial pressure of CO2 (PaCO2) at clinically desirable levels in mechanically ventilated ARDS patients using a six‐compartment mathematical model of CO2 and oxygen (O2) biochemistry and whole‐body transport with the inclusion of an ECCO2R device for extracorporeal veno‐venous removal of CO2. The model assumes steady state conditions. Model compartments were lung capillary blood, arterial blood, venous blood, post‐ECCO2R venous blood, interstitial fluid and tissue cells, with CO2 and O2 distribution within each compartment; biochemistry included equilibrium among bicarbonate and non‐bicarbonate buffers and CO2 and O2 binding to hemoglobin to elucidate Bohr and Haldane effects. O2 consumption and CO2 production rates were assumed proportional to predicted body weight (PBW) and adjusted to achieve reported arterial partial pressure of O2 and a PaCO2 level of 46 mmHg at a tidal volume of 7.6 mL/kg PBW in the absence of an ECCO2R device based on average data from LUNG SAFE. Model calculations showed that ECCO2R rates required to achieve mild permissive hypercapnia (PaCO2 of 46 mmHg) at a ventilation frequency or respiratory rate of 20.8/min during mechanical ventilation increased when tidal volumes decreased from 7.6 to 3 mL/kg PBW. Higher ECCO2R rates were required to achieve normocapnia (PaCO2 of 40 mmHg). Model calculations also showed that required ECCO2R rates were lower when ventilation frequencies were increased from 20.8/min to 26/min. The current mathematical model predicts that ECCO2R rates resulting in clinically desirable PaCO2 levels at tidal volumes of 5‐6 mL/kg PBW can likely be achieved in mechanically ventilated ARDS patients with current technologies; use of ultraprotective tidal volumes (3‐4 mL/kg PBW) may be challenging unless high mechanical ventilation frequencies are used.

¿Cuál es el volumen tidal ideal en pacientes ingresados en UCI sin SDRA que requieren ventilación mecánica más de 24 horas?

La protección pulmonar en los pacientes críticos sometidos a ventilación mecánica, es uno de los objetivos que persiguen los facultativos cuando utilizan esta herramienta terapéutica; que, pese a todos sus beneficios y su uso extendido, no está exenta de efectos adversos. El apoyo ventilatorio en el Síndrome de Distrés Respiratorio Agudo (SDRA) consta de una serie de medidas, entre las que se incluye el volumen tidal (VT) bajo. Pero, ¿qué ocurre con aquellos pacientes que precisan más de 24 horas de ventilación mecánica sin criterios de SDRA? ¿Cuál es su VT recomendado? La evidencia científica apoya que la ventilación con VT bajo se asocia a la disminución del número de complicaciones respiratorias en comparación con VT alto (si bien, los ensayos clínicos preexistentes comparaban volúmenes bajos de 6 ml/kg vs volúmenes muy altos, de más de 10 ml/kg) (1)(2). Por contra, los VT bajos pueden incrementar la necesidad de sedación, aumentan la tasa de asincronía entre el paciente y el ventilador e incluso algunos trabajos hablan de que podría aumentar el riesgo de delirio.(3) El objetivo principal del estudio fue determinar si una estrategia de ventilación con VT bajo es más efectiva que una estrategia de VT intermedio en función del número de días libres de ventilación en el día 28 en los pacientes vivos tras la aleatorización. ABSTRACT Which is the ideal tidal volume for patients in ICU without ARDS who need mechanical ventilation more than 24h? Invasive ventilation, one of the most frequently applied strategies in the intensive care unit (ICU), is increasingly recognized as a potentially harmful intervention. There is evidence that lung-protective ventilation using low tidal volumes improves survival in patients with acute respiratory distress syndrome (ARDS), but it is less certain whether tidal volume restriction benefits patients without ARDS. Two randomized clinical trials found tidal volume reduction to be associated with a lower number of pulmonary complications in patients without ARDS, and 2 individual patient data meta-analyses suggested that tidal volume reduction may shorten the time spent on the ventilator and duration of stay in the ICU and hospital. However, the use of low tidal volumes could lead to an in- creased need for sedation because of higher respiratory rate or patient-ventilator asynchrony and, possibly, self- inflicted lung injury due to compensatory injurious inspiratory efforts. In addition, it has been suggested that low tidal volumes may increase the risk of delirium. The Protective Ventilation in Patients Without ARDS (PReVENT) trial was conducted to test whether a ventilation strategy using low tidal volumes is superior to a ventilation strategy using intermediate tidal volumes with respect to the number of ventilator-free days and alive at day.

Driving pressure y mortalidad en el síndrome de distrés respiratorio agudo

Las actuales guías de manejo del síndrome de distrés respiratorio agudo (SDRA) recomiendan una ventilación protectora: volumen corriente bajo, presión positiva al final de la espiración (PEEP) adecuada y maniobras de reclutamiento alveolar. Sin embargo, estudios recientes han mostrado que la driving pressure podría ser la variable que mejor se correlaciona con la supervivencia en pacientes con SDRA. ABSTRACT Driving pressure and mortality in acute respiratory distress syndrome Current guidelines for ventilation in patients with acute respiratory distress syndrome (ARDS) recommend lung-protective ventilation: use of low tidal volumes, appropiate positive end-expiratory pressure and alveolar recruitment maneuvers. However, recent studies have shown that driving pressure could be the variable that best correlated with survival in patients with ARDS.