Positive End-expiratory Pressure Titration Research Articles

Automated Positive End-Expiratory Pressure Titration during Mechanical Ventilation

Abstract Optimizing the positive end-expiratory pressure remains challenging for any clinician treating a patient with acute respiratory distress syndrome. This paper presents an approach to automate a PEEP titration maneuver and identify the best PEEP according to maximal compliance. The respiratory system was modeled by a single-compartment model, and parameters were estimated using multiple linear regression. A classifier identified the best PEEP using the scaled relative change in compliance between PEEP levels based on empirical data from previous manual PEEP titrations. An experimental system allows the in vivo testing of the automated PEEP titration, including additional safety measures. The complete system was tested in a single animal experiment and correctly identified the best PEEP. The introduced system is a step closer towards an automated, standardized PEEP optimization and closed-loop control of mechanical ventilation.

THE STORY OF ONE PATIENT: MULTIPLE TRAUMA, ECMO, THE PATH TO LUNG TRANSPLANTATION AND ...

The mortality rate for multiple trauma in combination with severe chest trauma according to Abbreviated Injury Scale (AIS) > 3 is very high: 15.1% for all ages and 28.4% for people 65 years and older [7]. Severe contusion of the lungs can lead to massive hemothorax and severe tracheobronchial bleeding. If, for hemothorax, urgent surgery is performed based on chest drainage only, it is relatively difficult to find the source of tracheobronchial bleeding at an early stage of injury due to positive airway pressure ventilation. Due to lung contusion, a huge amount of tissue factor is released, which worsens coagulopathy and leads to increased bleeding. Worsening respiratory failure can also be caused by blood flow to the area of intact lungs from the area of the injured lungs. The incidence of acute respiratory distress syndrome in trauma patients ranges from 4.3 to 8.5%. In such cases, it is very difficult to maintain respiratory function only by standard ventilation control. Over the past two decades, a number of treatments have been developed that have improved the survival rate of patients with ARDS. Titration of lower tidal volumes and positive end-expiratory pressure (PEEP) significantly reduces mortality compared to traditional mechanical ventilation with high tidal volumes. In recent years, neuromuscular blocks and prone positioning have been introduced, demonstrating the mortality benefits of ARDS. Other supportive therapies are used, such as inhalation of prostacyclin, as well as alternative ventilation modes, such as bi-level ventilation or reduced airway pressure ventilation (APRV). Despite these advances in emergency therapies, some patients continue to deteriorate, and in such cases, veno-venous extracorporeal membrane oxygenation (IV-ECMO) becomes the best option as a last resort to save the lives of these patients.In this article, we presented a case of severe multiple trauma in a 35-year-old man with massive contusion of the lungs and continuing tracheobronchial bleeding, which led to the development of ARDS, destructive processes in the lungs and became the reason for the connection and long-term presence of the patient on VV-ECMO, due to the impossibility of providing with the help of mechanical ventilation gas exchange in the lungs.

Chinese expert consensus on the diagnosis and treatment of severely and critically ill patients with coronavirus disease 2019.

Chinese expert consensus on the diagnosis and treatment of severely and critically ill patients with coronavirus disease 2019.

Electrical impedance tomography to titrate positive end-expiratory pressure in COVID-19 acute respiratory distress syndrome

RationalePatients with coronavirus disease-19-related acute respiratory distress syndrome (C-ARDS) could have a specific physiological phenotype as compared with those affected by ARDS from other causes (NC-ARDS).ObjectivesTo describe the effect of positive end-expiratory pressure (PEEP) on respiratory mechanics in C-ARDS patients in supine and prone position, and as compared to NC-ARDS. The primary endpoint was the best PEEP defined as the smallest sum of hyperdistension and collapse.MethodsSeventeen patients with moderate-to-severe C-ARDS were monitored by electrical impedance tomography (EIT) and evaluated during PEEP titration in supine (n = 17) and prone (n = 14) position and compared with 13 NC-ARDS patients investigated by EIT in our department before the COVID-19 pandemic.ResultsAs compared with NC-ARDS, C-ARDS exhibited a higher median best PEEP (defined using EIT as the smallest sum of hyperdistension and collapse, 12 [9, 12] vs. 9 [6, 9] cmH2O, p < 0.01), more collapse at low PEEP, and less hyperdistension at high PEEP. The median value of the best PEEP was similar in C-ARDS in supine and prone position: 12 [9, 12] vs. 12 [10, 15] cmH2O, p = 0.59. The response to PEEP was also similar in C-ARDS patients with higher vs. lower respiratory system compliance.ConclusionAn intermediate PEEP level seems appropriate in half of our C-ARDS patients. There is no solid evidence that compliance at low PEEP could predict the response to PEEP.

Individualized flow-controlled ventilation compared to best clinical practice pressure-controlled ventilation: a prospective randomized porcine study

BackgroundFlow-controlled ventilation is a novel ventilation method which allows to individualize ventilation according to dynamic lung mechanic limits based on direct tracheal pressure measurement at a stable constant gas flow during inspiration and expiration. The aim of this porcine study was to compare individualized flow-controlled ventilation (FCV) and current guideline-conform pressure-controlled ventilation (PCV) in long-term ventilation.MethodsAnesthetized pigs were ventilated with either FCV or PCV over a period of 10 h with a fixed FiO2 of 0.3. FCV settings were individualized by compliance-guided positive end-expiratory pressure (PEEP) and peak pressure (Ppeak) titration. Flow was adjusted to maintain normocapnia and the inspiration to expiration ratio (I:E ratio) was set at 1:1. PCV was performed with a PEEP of 5 cm H2O and Ppeak was set to achieve a tidal volume (VT) of 7 ml/kg. The respiratory rate was adjusted to maintain normocapnia and the I:E ratio was set at 1:1.5. Repeated measurements during observation period were assessed by linear mixed-effects model.ResultsIn FCV (n = 6), respiratory minute volume was significantly reduced (6.0 vs 12.7, MD − 6.8 (− 8.2 to − 5.4) l/min; p < 0.001) as compared to PCV (n = 6). Oxygenation was improved in the FCV group (paO2 119.8 vs 96.6, MD 23.2 (9.0 to 37.5) Torr; 15.97 vs 12.87, MD 3.10 (1.19 to 5.00) kPa; p = 0.010) and CO2 removal was more efficient (paCO2 40.1 vs 44.9, MD − 4.7 (− 7.4 to − 2.0) Torr; 5.35 vs 5.98, MD − 0.63 (− 0.99 to − 0.27) kPa; p = 0.006). Ppeak and driving pressure were comparable in both groups, whereas PEEP was significantly lower in FCV (p = 0.002). Computed tomography revealed a significant reduction in non-aerated lung tissue in individualized FCV (p = 0.026) and no significant difference in overdistended lung tissue, although a significantly higher VT was applied (8.2 vs 7.6, MD 0.7 (0.2 to 1.2) ml/kg; p = 0.025).ConclusionOur long-term ventilation study demonstrates the applicability of a compliance-guided individualization of FCV settings, which resulted in significantly improved gas exchange and lung tissue aeration without signs of overinflation as compared to best clinical practice PCV.

Respiratory Therapeutic Strategies in Children and Adolescents with COVID-19: A Critical Review.

Evidence on the treatment strategies for the child population with critical conditions due to COVID-19 is scarce and lacks consensus. Thus, this study aimed to critically review non-pharmacological respiratory strategies for this population. Original studies were searched in six databases considering predefined inclusion criteria. Other studies and recommendations were also included after a manual search. Oxygen therapy, invasive (IMV) and non-invasive (NIV) ventilation were the most frequently addressed interventions. In general, the original studies have cited these strategies, but detailed information on the parameters used was not provided. The recommendations provided more detailed data, mainly based on experiences with other acute respiratory syndromes in childhood. In the context of oxygen therapy, the nasal catheter was the most recommended strategy for hypoxemia, followed by the high-flow nasal cannula (HFNC). However, the risks of contamination due to the dispersion of aerosols in the case of the HFNC were pointed out. Lung protective IMV with the use of bacteriological or viral filters was recommended in most documents, and there was great variation in PEEP titration. Alveolar recruitment maneuvers were mentioned in a few recommendations. NIV was not consensual among studies, and when selected, several precautions must be taken to avoid contamination. Airway suctioning with a closed-circuit was recommended to reduce aerosol spread. Information on prone positioning and physiotherapy was even more scarce. In conclusion, oxygen therapy seems to be essential in the treatment of hypoxemia. If necessary, IMV should not be delayed, and protective strategies are encouraged for adequate pulmonary ventilation. Information about techniques that are adjuvant to ventilatory support is superficial and requires further investigation.

Current and evolving standards of care for patients with ARDS.

Care for patients with acute respiratory distress syndrome (ARDS) has changed considerably over the 50 years since its original description. Indeed, standards of care continue to evolve as does how this clinical entity is defined and how patients are grouped and treated in clinical practice. In this narrative review we discuss current standards – treatments that have a solid evidence base and are well established as targets for usual care – and also evolving standards – treatments that have promise and may become widely adopted in the future. We focus on three broad domains of ventilatory management, ventilation adjuncts, and pharmacotherapy. Current standards for ventilatory management include limitation of tidal volume and airway pressure and standard approaches to setting PEEP, while evolving standards might focus on limitation of driving pressure or mechanical power, individual titration of PEEP, and monitoring efforts during spontaneous breathing. Current standards in ventilation adjuncts include prone positioning in moderate-severe ARDS and veno-venous extracorporeal life support after prone positioning in patients with severe hypoxemia or who are difficult to ventilate. Pharmacotherapy current standards include corticosteroids for patients with ARDS due to COVID-19 and employing a conservative fluid strategy for patients not in shock; evolving standards may include steroids for ARDS not related to COVID-19, or specific biological agents being tested in appropriate sub-phenotypes of ARDS. While much progress has been made, certainly significant work remains to be done and we look forward to these future developments.

Application of two different nasal CPAP levels for the treatment of respiratory distress syndrome in preterm infants\u2014\u201cThe OPTTIMMAL-Trial\u201d\u2014Optimizing PEEP To The IMMAture Lungs: study protocol of a randomized controlled trial

BackgroundNasal continuous positive airway pressure (CPAP) applies positive end-expiratory pressure (PEEP) and has been shown to reduce the need for intubation and invasive mechanical ventilation in very low birth weight infants with respiratory distress syndrome. However, CPAP failure rates of 50% are reported in large randomized controlled trials. A possible explanation for these failure rates is the application of insufficient low levels of PEEP during nasal CPAP treatment to maintain adequate functional residual capacity shortly after birth. The optimum PEEP level to treat symptoms of respiratory distress in very low birth weight infants has not been assessed in clinical studies. The aim of the study is to compare two different PEEP levels during nasal CPAP treatment in preterm infants.MethodsIn this randomized multicenter trial, 216 preterm infants born at 26 + 0–29 + 6 gestational weeks will be allocated to receive a higher (6–8 cmH2O) or a lower (3–5 cmH2O) PEEP during neonatal resuscitation and the first 120 h of life. The PEEP level within each group will be titrated throughout the intervention based on the FiO2 (fraction of inspired oxygen concentration) requirements to keep oxygenation within the target range. The primary outcome is defined as the need for intubation and mechanical ventilation for > 1 h or being not ventilated but reaching one of the two pre-defined CPAP failure criteria (FiO2 > 0.5 for > 1 h or pCO2 ≥ 70 mmHg in two consecutive blood gas analyses at least 2 h apart).DiscussionBased on available data from the literature, the optimum level of PEEP that most effectively treats respiratory distress syndrome in preterm infants is unknown, since the majority of large clinical trials applied a wide range of PEEP levels (4–8 cmH2O). The rationale for our study hypothesis is that the early application of a higher PEEP level will more effectively counteract the collapsing properties of the immature and surfactant-deficient lungs and that the level of inspired oxygen may serve as a surrogate marker to guide PEEP titration. Finding the optimum noninvasive continuous distending pressure during early nasal CPAP is required to improve CPAP efficacy and as a consequence to reduce the exposure to ventilator-induced lung injury and the incidence of chronic lung disease in this vulnerable population of very preterm infants.Trial registrationdrks.de DRKS00019940. Registered on March 13, 2020

The use of intraoperative bedside lung ultrasound in optimizing positive end expiratory pressure in obese patients undergoing laparoscopic bariatric surgeries.

Anesthetic management of patients with obesity undergoing laparoscopic abdominal surgeries requires careful plan for intraoperative mechanical ventilation aiming to avoid lung atelectasis and/or overdistention. There are conflicting data on the optimum positive end expiratory pressure (PEEP) during these surgeries. We hypothesized that lung ultrasound could be used for PEEP titration during laparoscopic surgery. The purpose of this study is to evaluate the effectiveness of intraoperative individualized lung ultrasound-guided PEEP in obese patients undergoing laparoscopic bariatric surgery on intraoperative partial arterial oxygen tension (PaO2) and early postoperative pulmonary complications. A randomized controlled trial included 40 adult patients with body mass index (BMI) > 35 kg/m2 undergoing laparoscopic bariatric surgery. Patients were randomized into: control group (n= 20) who received PEEP 4 cm.H2 O and ultrasound-guided group (n = 20) who received individualized lung ultrasound stepwise PEEP. All patients received volume-controlled ventilation with a tidal volume of 6 mL/kg of ideal weight and a fraction of inspired oxygen of .5. The primary outcome was the difference in partial arterial oxygen tension (PaO2) between the control group and the ultrasound-guided group. The secondary outcomes included the incidence of early postoperative pulmonary atelectasis, respiratory failure, bronchospasm, hypoxia or pneumothorax. General surgery operating theatre at Cairo University hospitals. Ultrasound-guided group showed higher PO2 after PEEP optimization and postoperatively compared with control group (P = .005, and P = .01 respectively). Also, ultrasound-guided group showed no postoperative complications compared with control group that had 5 cases who developed postoperative pulmonary complications in the form of hypoxia and basal collapse in the first 24 hour postoperatively chest x ray (0% versus 25%, P = .047). In patients with obesity undergoing laparoscopic bariatric surgery, the use of lungultrasound individualized stepwise PEEP approach improved oxygenation, compliance and reduced the incidence of postoperative pulmonary atelectasis and hypoxia without causing hemodynamicinstability.

Robust predictive control for respiratory CO2 gas removal in closed-loop mechanical ventilation: An in-silico study

Abstract In this study a physiological closed-loop system for arterial CO2 partial pressure control was designed and comprehensively tested using a set of models of the respiratory CO2 gas exchange. The underlying preclinical data were collected from 12 pigs in presence of severe changes in hemodynamic and pulmonary condition. A minimally complex nonlinear state space model of CO2 gas exchange was identified post hoc in different lung conditions. The control variable was measured noninvasively using the endtidal CO2 partial pressure. For the simulation study the output signal of the controller was defined as the alveolar minute volume set value of an underlying adaptive lung protective ventilation mode. A linearisation of the two-compartment CO2 gas exchange model was used for the design of a model predictive controller (MPC). It was augmented by a tube based controller suppressing prediction errors due to model uncertainties. The controller was subject to comparative testing in interaction with each of the CO2 gas exchange models previously identified on the preclinical study data. The performance was evaluated for the system response towards the following five tests in comparison to a PID controller: recruitment maneuver, PEEP titration maneuver, stepwise change in the CO2 production, breath-hold maneuver and a step in the reference signal. A root mean square error of 2.69 mmHg between arterial CO2 partial pressure and the reference signal was achieved throughout the trial. The reference-variable response of the model predictive controller was superior regarding overshoot and settling time.

Physiological effects of two driving pressure-based methods to set positive end-expiratory pressure during one lung ventilation.

During one-lung ventilation (OLV), titrating the positive end-expiratory pressure (PEEP) to target a low driving pressure (∆P) could reduce postoperative pulmonary complications. However, it is unclear how to conduct PEEP titration: by stepwise increase starting from zero PEEP (PEEPINCREMENTAL) or by stepwise decrease after a lung recruiting manoeuvre (PEEPDECREMENTAL). In this randomized trial, we compared the physiological effects of these two PEEP titration strategies on respiratory mechanics, ventilation/perfusion mismatch and gas exchange. Patients undergoing video-assisted thoracoscopic surgery in OLV were randomly assigned to a PEEPINCREMENTAL or PEEPDECREMENTAL strategy to match the lowest ∆P. In the PEEPINCREMENTAL group, PEEP was stepwise titrated from ZEEP up to 16 cm H2O, whereas in the PEEPDECREMENTAL group PEEP was decrementally titrated, starting from 16 cm H2O, immediately after a lung recruiting manoeuvre. Respiratory mechanics, ventilation/perfusion mismatch and blood gas analyses were recorded at baseline, after PEEP titration and at the end of surgery. Sixty patients were included in the study. After PEEP titration, shunt decreased similarly in both groups, from 50 [39–55]% to 35 [28–42]% in the PEEPINCREMENTAL and from 45 [37–58]% to 33 [25–45]% in the PEEPDECREMENTAL group (both p < 0.001 vs baseline). The resulting ∆P, however, was lower in the PEEPDECREMENTAL than in the PEEPINCREMENTAL group (8 [7–11] vs 10 [9–11] cm H2O; p = 0.03). In the PEEPDECREMENTAL group the PaO2/ FIO2 ratio increased significantly after intervention (from 140 [99–176] to 186 [152–243], p < 0.001). Both the PEEPINCREMENTAL and the PEEPDECREMENTAL strategies were able to decrease intraoperative shunt, but only PEEPDECREMENTAL improved oxygenation and lowered intraoperative ΔP.Clinical trial number NCT03635281; August 2018; “retrospectively registered”Electronic supplementary materialThe online version of this article (10.1007/s10877-020-00582-z) contains supplementary material, which is available to authorized users.

Intensive care management to reduce morbidities following pediatric liver transplantation in Indonesia

PurposeOutcome of pediatric liver transplant patients is affected by various factors, including critical care management in the early phase following surgery. This article focuses on early recognition of complications in pediatric liver transplant patients in Pediatric Intensive Care Unit (PICU). In particular, this article highlights the common problem in post-liver transplant pediatric patients in Indonesia, and the strategies to optimize recovery and minimize complications. SummaryAlmost every system organ is affected by the surgery and medications given intra- and post-operatively. Careful monitoring and appropriate management are needed to ensure long-term success of surgery and prevent both early and late complications. Early extubation is recommended, however some may need PEEP titration to obtain optimal oxygenation. Advanced hemodynamic monitoring paired with clinical signs is recommended for optimal perfusion and ventriculo-arterial coupling. Routine electrolytes examination and neurological assessment are needed. Infection control and immunosuppression have to be optimized. Early enteral nutrition, nutritional support for recovery is needed, however should be gradually administered in malnourished patients. ConclusionEarly detection of post-transplant complications must be identified to ensure appropriate management is given as soon as possible. The ultimate goal is to retain graft acceptance as long as possible and the reduction of morbidity and mortality post-transplantation.

La tomographie par impédance électrique : un outil précieux pour le clinicien

La tomographie par impédance électrique (TIE) est une technique d’imagerie non invasive, facilement utilisable au chevet du patient qui permet d’obtenir une évaluation dynamique de la ventilation pulmonaire ainsi qu’une analyse fonctionnelle de régions pulmonaires distinctes. Les variations d’impédance sont mesurées en appliquant un courant alternatif de faible intensité (5mA, 50-70 Hz) au travers d’électrodes placées sur une ceinture positionnée au niveau de la cage thoracique du patient. Les images reconstruites à l’écran sont soit statiques soit dynamiques et représentent la distribution de conductivité à un instant donné ou la variation de la distribution de conductivité entre deux instants. Elles permettent au clinicien d’apprécier en temps réel le degré d’homogénéité de la ventilation et de détecter d’éventuelles asynchronies ventilatoires. Pratiquement, la TIE permet de quantifier les variations régionales d’impédance pulmonaire en fin d’expiration qui seraient en étroit rapport avec les variations de volume de fin d’expiration.Elle offre également la possibilité de mesurer la variation d’impédance à chaque cycle respiratoire, la compliance régionale du système respiratoire, d’évaluer les zones de collapsus, d’atélectasies ou de surdistension, de calculer le centre de ventilation ou encore l’indice de retard régional de ventilation. Elle permet donc de surveiller la ventilation en temps réel et en continu et d’apprécier les répercussions de différents réglages de la ventilation mécanique (titration de la PEEP…) ou de manœuvres à visée thérapeutique sur la ventilation régionale.

Individualized positive end-expiratory pressure setting in patients with severe acute respiratory distress syndrome supported with veno-venous extracorporeal membrane oxygenation.

Patients with acute respiratory distress syndrome supported with veno-venous extracorporeal membrane oxygenation benefit from higher positive end-expiratory pressure combined with conventional ventilation during the early extracorporeal membrane oxygenation period. The role of incremental positive end-expiratory pressure titration in patients with severe acute respiratory distress syndrome supported with veno-venous extracorporeal membrane oxygenation remains unclear. This study aimed to determine the preferred method for setting positive end-expiratory pressure in patients with severe acute respiratory distress syndrome on veno-venous extracorporeal membrane oxygenation support. We retrospectively reviewed all subjects supported with veno-venous extracorporeal membrane oxygenation for severe acute respiratory distress syndrome from 2009 to 2019 in the intensive care units in Tianjin Third Central Hospital. Subjects were divided into two groups according to the positive end-expiratory pressure titration method used: P-V curve (quasi-static pressure-volume curve-guided positive end-expiratory pressure setting) group or Crs (respiratory system compliance-guided positive end-expiratory pressure setting) group. Forty-three subjects were included in the clinical outcome analysis: 20 in the P-V curve group and 23 in the Crs group. Initial positive end-expiratory pressure levels during veno-venous extracorporeal membrane oxygenation were similar in both groups. Incidence rates of barotrauma and hemodynamic events were significantly lower in the Crs group (all p < 0.05). Mechanical ventilation duration, intensive care unit length of stay, and hospital length of stay were significantly shorter in the Crs group than the P-V curve group (all p < 0.05). Subjects in the Crs group showed non-significant improvements in the duration of extracorporeal membrane oxygenation support and 28-day mortality (p > 0.05). Respiratory system compliance-guided positive end-expiratory pressure setting may lead to more optimal clinical outcomes for patients with severe acute respiratory distress syndrome supported by veno-venous extracorporeal membrane oxygenation. Moreover, the operation is simple, safe, and convenient in clinical practice.

The Stepwise Slow Titration of Positive End-Expiratory Pressure Before the End of General Anaesthesia Improves Lung Mechanics in Children: A Randomized Open Label Clinical Trial

Background: Intraoperative application of positive end-end-expiratory pressure (PEEP) is recommended in mechanically ventilated children since it improves lung mechanics. However, inadequate level of applied pressure can increase risk of barotrauma. Objectives: To assess the impact of titrated PEEP on lung mechanics in mechanically ventilated children under general anaesthesia. Methods: This was an open label, single Tertiary Centre randomized controlled clinical trial. The study population included 70 preschool children, ASA I and II, scheduled for orthopaedic, reconstructive, abdominal or urological surgery. Children with upper respiratory tract infection, allergic to chosen anaesthetics, cardiorespiratory comorbidities were excluded. Patients were randomly assigned either to receive intraoperative PEEP titration form 5 - 11 cmH2O 20 minutes before the end of anaesthesia (intervention group) or to be ventilated until the end of anaesthesia conventionally with a positive end-expiratory pressure of 3 cmH2O (control group). Main outcomes: changes in dynamic lung compliance (Cdyn), peak airway pressure (PIP), mean airway pressure (Paw) between groups at the end of surgery; changes in PIP and Paw during PEEP titration and desaturation in interventional group during PEEP titration. Results: Seventy preschool children were recruited and analysed. Intraoperative positive end-expiratory pressure titration improved Cdyn in the intervention group comparing to control (ΔCdy -3.2 vs. 0.63; P &lt; 0.001). PIP and Paw were higher in interventional group (ΔPIP -0.57vs. 0.11; P &lt; 0.001, and ΔPaw -0.63 vs. 0.0; P &lt; 0.001) and desaturation was not observed in interventional group. Conclusions: Stepwise titration of PEEP up to 11 cmH2O improves subsequent lung mechanics without causing of barotrauma.

In Response.

In Response.

Effects of intraoperative individualized PEEP on postoperative atelectasis in obese patients: study protocol for a prospective randomized controlled trial

BackgroundObese patients undergoing general anesthesia and mechanical ventilation during laparoscopic abdominal surgery commonly have a higher incidence of postoperative pulmonary complications (PPCs), due to factors such as decreasing oxygen reserve, declining functional residual capacity, and reducing lung compliance. Pulmonary atelectasis caused by pneumoperitoneum and mechanical ventilation is further aggravated in obese patients. Recent studies demonstrated that individualized positive end-expiratory pressure (iPEEP) was one of effective lung-protective ventilation strategies. However, there is still no exact method to determine the best iPEEP, especially for obese patients. Here, we will use the best static lung compliance (Cstat) method to determine iPEEP, compared with regular PEEP, by observing the atelectasis area measured by electrical impedance tomography (EIT), and try to prove a better iPEEP setting method for obese patients.MethodsThis study is a single-center, two-arm, prospective, randomized control trial. A total number of 80 obese patients with body mass index ≥ 32.5 kg/m2 scheduled for laparoscopic gastric volume reduction and at medium to high risk for PPCs will be enrolled. They will be randomly assigned to control group (PEEP5 group) and iPEEP group. A PEEP of 5 cmH2O will be used in PEEP5 group, whereas an individualized PEEP value determined by a Cstat-directed PEEP titration procedure will be applied in the iPEEP group. Standard lung-protective ventilation methods such as low tidal volumes (7 ml/kg, predicted body weight, PBW), a fraction of inspired oxygen ≥ 0.5, and recruitment maneuvers (RM) will be applied during and after operation in both groups. Primary endpoints will be postoperative atelectasis measured by chest electrical impedance tomography (EIT) and intraoperative oxygen index. Secondary endpoints will be serum IL-6, TNF-α, procalcitonin (PCT) kinetics during and after surgery, incidence of PPCs, organ dysfunction, length of in-hospital stay, and hospital expense.DiscussionAlthough there are several studies about the effect of iPEEP titration on perioperative PPCs in obese patients recently, the iPEEP setting method they used was complex and was not always feasible in routine clinical practice. This trial will assess a possible simple method to determine individualized optimal PEEP in obese patients and try to demonstrate that individualized PEEP with lung-protective ventilation methods is necessary for obese patients undergoing general surgery. The results of this trial will support anesthesiologist a feasible Cstat-directed PEEP titration method during anesthesia for obese patients in attempt to prevent PPCs.Trial registrationwww.chictr.org.cn ChiCTR1900026466. Registered on 11 October 2019

Lung protective ventilation in infants undergoing cardiopulmonary bypass surgery for congenital heart disease: A prospective randomized controlled trial.

Lung protective ventilation (LPV) has been applied to surgical adults with normal pulmonary function for optimizing mechanical ventilation and reducing postoperative pulmonary complications. Few studies have reported the use of LPV in infants undergoing cardiac surgery with cardiopulmonary bypass (CPB). To explore safety and effectiveness of LPV in infants undergoing CPB surgery for congenital heart disease (CHD). Included in this study were 77 infants who underwent CPB surgery for CHD from November 2017 to September 2018. They were randomized into the LPV group and conventional ventilation (CV) group. In the LPV group, small-tidal-volume (6-8ml/kg) ventilation, lung recruitment by PEEP increment to the maximum level of 15cm H2 O after CPB, and individualized optimal PEEP titration were applied. In the CV group, traditional tidal volume (10-12ml/kg with zero PEEP) was applied. The primary outcome was the ratio of arterial partial pressure of oxygen to inspiratory oxygen fraction (PaO2 /FiO2 ). The secondary outcomes were respiratory dynamic parameters, hypoxemia, prognostic indexes, and postoperative pulmonary complications. PaO2 /FiO2 in the LPV group (416.86, 95%CI: 381.60-452.12) was significantly higher than that in the CV group (263.37, 95%CI: 227.65-299.09) after intervention (P<.001). There was a significant difference in the trend of change in dynamic compliance, alveolar-arterial oxygen difference, arterial-end-expired carbon dioxide difference, driving pressure, and respiratory index between the two groups at different time points from weaning from CPB to 2hours after operation. There was no significant difference in PaO2 /FiO2 , alveolar-arterial oxygen difference, respiratory index, and dynamic compliance 2hours postoperative and in the incidence of postoperative pulmonary complications, prognostic indexes between the two groups. LPV could be used safely in infants undergoing CPB in that it can improve oxygenation, alveolar aeration, and dynamic compliance, and reduce driving pressure, pulmonary shunting, and dead space. Its effect on oxygenation, pulmonary gas exchange, and pulmonary compliance was relatively short, and had less impact on postoperative pulmonary complications and prognosis.

Recruitability and effect of PEEP in SARS-Cov-2-associated acute respiratory distress syndrome

BackgroundA large proportion of patients with a SARS-Cov-2-associated respiratory failure develop an acute respiratory distress syndrome (ARDS). It has been recently suggested that SARS-Cov-2-associated ARDS may differ from usual non-SARS-Cov-2-associated ARDS by higher respiratory system compliance (CRS), lower potential for recruitment with positive end-expiratory pressure (PEEP) contrasting with severe shunt fraction. The purpose of the study was to systematically assess respiratory mechanics and recruitability in SARS-Cov-2-associated ARDS.MethodsGas exchanges, CRS and hemodynamics were assessed at 2 levels of PEEP (15 cmH2O and 5 cmH2O) within 36 h (day1) and from 4 to 6 days (day 5) after intubation. The recruited volume was computed as the difference between the volume expired from PEEP 15 to 5 cmH2O and the volume predicted by compliance at PEEP 5 cmH2O (or above airway opening pressure). The recruitment-to-inflation (R/I) ratio (i.e. the ratio between the recruited lung compliance and CRS at PEEP 5 cmH2O) was used to assess lung recruitability. A R/I ratio value higher than or equal to 0.5 was used to define highly recruitable patients.ResultsThe R/I ratio was calculated in 25 of the 26 enrolled patients at day 1 and in 15 patients at day 5. At day 1, 16 (64%) were considered as highly recruitable (R/I ratio median [interquartile range] 0.7 [0.55–0.94]) and 9 (36%) were considered as poorly recruitable (R/I ratio 0.41 [0.31–0.48]). The PaO2/FiO2 ratio at PEEP 15 cmH2O was higher compared to PEEP 5 cmH2O only in highly recruitable patients (173 [139–236] vs 135 [89–167] mmHg; p < 0.01). Neither PaO2/FiO2 or CRS measured at PEEP 15 cmH2O or at PEEP 5 cmH2O nor changes in PaO2/FiO2 or CRS in response to PEEP changes allowed to identify highly or poorly recruitable patients.ConclusionIn this series of 25 patients with SARS-Cov-2 associated ARDS, 64% were considered as highly recruitable and only 36% as poorly recruitable based on the R/I ratio performed on the day of intubation. This observation suggests that a systematic R/I ratio assessment may help to guide initial PEEP titration to limit harmful effect of unnecessary high PEEP in the context of Covid-19 crisis.

Influence of Positive End-Expiratory Pressure Titration on the Effects of Pronation in Acute Respiratory Distress Syndrome: A Comprehensive Experimental Study.

Prone position can reduce mortality in acute respiratory distress syndrome (ARDS), but several studies found variable effects on oxygenation and lung mechanics. It is unclear whether different positive end-expiratory pressure (PEEP) titration techniques modify the effect of prone position. We tested, in an animal model of ARDS, if the PEEP titration method may influence the effect of prone position on oxygenation and lung protection. In a crossover study in 10 piglets with a two-hit injury ARDS model, we set the “best PEEP” according to the ARDS Network low-PEEP table (BPARDS) or targeting the lowest transpulmonary driving pressure (BPDPL). We measured gas exchange, lung mechanics, aeration, ventilation, and perfusion with computed tomography (CT) and electrical impedance tomography in each position with both PEEP titration techniques. The primary endpoint was the PaO2/FiO2 ratio. Secondary outcomes were lung mechanics, regional distribution of ventilation, regional distribution of perfusion, and homogeneity of strain derived by CT scan. The PaO2/FiO2 ratio increased in prone position when PEEP was set with BPARDS [difference 54 (19–106) mmHg, p = 0.04] but not with BPDPL [difference 17 (−24 to 68) mmHg, p = 0.99]. The transpulmonary driving pressure significantly decreased during prone position with both BPARDS [difference −0.9 (−1.5 to −0.9) cmH2O, p = 0.009] and BPDPL [difference −0.55 (−1.6 to −0.4) cmH2O, p = 0.04]. Pronation homogenized lung regional strain and ventilation and redistributed the ventilation/perfusion ratio along the sternal-to-vertebral gradient. The PEEP titration technique influences the oxygenation response to prone position. However, the lung-protective effects of prone position could be independent of the PEEP titration strategy.