Positive End-expiratory Pressure Levels Research Articles

The impact of pneumoperitoneum on respirtory system: complications and managment strategies in laparoscopic surgery

Laparoscopic surgery, a cornerstone of contemporary surgical practice, revolutionizes traditional surgical techniques by employing minimally invasive procedures. However, this innovative approach poses intricate challenges, particularly in respiratory management, necessitating a comprehensive understanding of its physiological implications. Pneumoperitoneum involves insufflating the abdominal cavity with carbon dioxide (CO2) to create a suitable working space. The introduction of CO2 into the peritoneal cavity elevates intra-abdominal pressure, prompting physiological adaptations that compromise respiratory function. These alterations, including increased peak inspiratory pressure, decreased dynamic respiratory system compliance, and the promotion of intraoperative atelectasis, underscore the intricate interplay between pneumoperitoneum and respiratory physiology.Amidst these challenges, positive end-expiratory pressure emerges as a crucial intervention for mitigating the adverse effects of pneumoperitoneum on respiratory mechanics. By maintaining airway patency and preventing alveolar collapse during expiration, positive end-expiratory pressure helps counteract the reduction in functional residual capacity associated with elevated intra-abdominal pressure. Additionally, positive endexpiratory pressure serves to optimize lung recruitment, thereby improving ventilation-perfusion matching and enhancing oxygenation.Mechanical ventilation during laparoscopic procedures further complicates respiratory management, potentially exacerbating lung injury. The application of protective lung ventilation strategies, such as low tidal volume combined with judicious positive end-expiratory pressure titration, represents a cornerstone in mitigating ventilator-induced lung injury and reducing postoperative pulmonary complications. However, the optimal implementation of these strategies remains a subject of ongoing debate, highlighting the need for personalized approaches tailored to individual patient characteristics and surgical contexts.Understanding the pivotal role of positive end-expiratory pressure in mitigating the adverse respiratory effects of pneumoperitoneum underscores its importance as a cornerstone intervention in laparoscopic surgery. By optimizing positive end-expiratory pressure levels based on patient characteristics and procedural requirements, healthcare practitioners can effectively mitigate the risk of pulmonary complications and enhance surgical outcomes.

Development of a Framework for the Hemodynamic Impact of Positive End-Expiratory Pressure in Normal and Heart Failure Conditions.

Positive end-expiratory pressure (PEEP) improves respiratory conditions. However, the complex interaction between PEEP and hemodynamics in heart failure patients makes it challenging to determine appropriate PEEP settings. In this study, we developed a framework for the impact of PEEP on hemodynamics considering cardiac function, by integrating the impact of PEEP in the generalized circulatory equilibrium framework, and validated the framework by assessing its ability to accurately predict PEEP-induced hemodynamics. In eight dogs, PEEP was increased stepwise, and hemodynamic responses were measured under normal, volume-loaded, and myocardial infarction (MI)-induced heart failure conditions. For predicting hemodynamics under PEEP using the proposed framework, the PEEP-intrathoracic pressure (ITP) relationship was empirically established in dogs. Hemodynamic parameters were estimated at each PEEP level based on the hemodynamics recorded without PEEP. The parameters were then used to predict hemodynamics under various heart conditions. The predicted and measured values were compared. Stepwise increase of PEEP decreased arterial pressure (AP) and cardiac output (CO). Left atrial pressure (LAP) decreased in normal hearts but increased in MI hearts. Predicted AP [R2, 0.92; root mean squared error (RMSE), 6.3 mmHg], CO (R2, 0.96; RMSE, 7.9 ml∙min-1∙kg-1) and LAP (R2, 0.92; RMSE, 2.3 mmHg) matched measured values with high accuracy, irrespective of volume status or heart condition. In conclusion, we developed a framework for the hemodynamic impact of PEEP considering cardiac function and demonstrated its validity. The results indicate that the effects of PEEP on hemodynamics can be explained primarily by ITP, and are modulated by cardiac function.

Effect of intraoperative positive end-expiratory pressure on post-operative pulmonary complications in overweight patients undergoing elective laparoscopic hernia surgery: A prospective randomised controlled trial.

Post-operative pulmonary complications (PPCs) are a significant cause of morbidity following surgery. This study evaluated the effect of intraoperative positive end-expiratory pressure (PEEP) on PPCs in overweight patients undergoing elective laparoscopic hernia surgery. In this randomised controlled trial, 60 patients with a body mass index between 25 and 30 kg/m² were divided equally into a standard PEEP group (5 cm H2O) and a high PEEP group (10 cm H2O). The primary outcome was the incidence of PPCs, with secondary outcomes assessing intraoperative respiratory mechanics, haemodynamics and post-operative oxygenation levels. Both groups demonstrated comparable demographic and baseline characteristics. The results showed a significant reduction in the incidence of PPCs in the high PEEP group, with atelectasis observed in 16% of control patients versus 6% of those receiving higher PEEP. In addition, the high PEEP group exhibited improved dynamic lung compliance and oxygenation but had an increased mean arterial pressure, indicating haemodynamic effects associated with higher PEEP levels. While the Cabrini Respiratory Strain Score and air test scores were comparable, patients in the high PEEP group had shorter durations of supplemental oxygen therapy and improved post-operative oxygenation at 6, 12 and 24 h. These findings suggest that high PEEP may enhance lung mechanics and oxygenation while reducing PPCs in overweight patients, although careful monitoring of haemodynamic stability is recommended.

Respiratory metrics of neonatal positive pressure ventilation on different ventilatory rates: A simulation study.

Effective ventilation is the core of neonatal resuscitation (NR). T-piece resuscitators (TPR) and self-inflating bags (SIB) are the two most widely utilized resuscitation devices. Nevertheless, limited information is available regarding the respiratory metrics during NR with these devices. This study aimed to evaluate the respiratory metrics at different ventilatory rates (VR) using a TPR or SIB during NR training. An observational, simulation study was conducted during a NR training course. The participants were instructed to perform positive pressure ventilation at predetermined pressures and varying rates using TPR and SIB. They were subsequently grouped into three categories based on their actual VR: 20-40 breaths per minute (bpm) (SlowVR), 40-60bpm (StdVR), and 60-80bpm (FastVR). Respiratory metrics were recorded and analyzed using a neonatal active lung model (NALM). Of the 71 participants in the training course, data from 66 were validated by analyzing 198 ventilations. In general, the participants manipulated the TPR slightly slower than the SIB. Notably, the positive end-expiratory pressure (PEEP) detected via TPR in the NALM was substantially higher, whereas the tidal volume (Tv) and minute volume (MV) with TPR were significantly smaller than those with SIB (p<0.05). A significant decrease in the peak alveolar pressure (palva) was observed with faster TPR ventilation (p<0.001), whereas no such reduction was observed with SIB (p=0.103). Additionally, faster VR correlated positively with higher PEEP levels for both TPR (F=7.543, p=0.002) and SIB (F=7.720, p=0.002) and inversely with smaller Tv for both TPR (F=19.239, p<0.001) and SIB (F=14.937, p<0.001). However, no significant differences in MV were observed across the different VR for either TPR or SIB (both p>0.05). Faster VR were inversely associated with smaller Tv but increased PEEP in both devices. Despite the guidelines of NR, VR exceeding 60bpm with TPR might sometimes be used, was associated with excessive PEEP in TPR, which may not be a safe in clinical practice. The effect of varying VR on MV was relatively minor for both TPR and SIB.

Effects of Automated Versus Conventional Ventilation on Quality of Oxygenation—A Substudy of a Randomized Crossover Clinical Trial

Background/Objectives: Attaining adequate oxygenation in critically ill patients undergoing invasive ventilation necessitates intense monitoring through pulse oximetry (SpO2) and frequent manual adjustments of ventilator settings like the fraction of inspired oxygen (FiO2) and the level of positive end-expiratory pressure (PEEP). Our aim was to compare the quality of oxygenation with the use of automated ventilation provided by INTELLiVENT–Adaptive Support Ventilation (ASV) vs. ventilation that is not automated, i.e., conventional pressure-controlled or pressure support ventilation. Methods: A substudy within a randomized crossover clinical trial in critically ill patients under invasive ventilation. The primary endpoint was the percentage of breaths in an optimal oxygenation zone, defined by predetermined levels of SpO2, FiO2, and PEEP. Secondary endpoints were the percentage of breaths in acceptable or critical oxygenation zones, the percentage of time spent in optimal, acceptable, and critical oxygenation zones, the number of manual interventions at the ventilator, and the number and duration of ventilator alarms related to oxygenation. Results: Of the 96 patients included in the parent study, 53 were eligible for this current subanalysis. Among them, 31 patients were randomized to start with automated ventilation, while 22 patients began with conventional ventilation. No significant differences were found in the percentage of breaths within the optimal zone between the two ventilation modes (median percentage of breaths during automated ventilation 19.4 [0.1–99.9]% vs. 25.3 [0.0–100.0]%; p = 0.963). Similarly, there were no differences in the percentage of breaths within the acceptable and critical zones, nor in the time spent in the three predefined oxygenation zones. Although the number of manual interventions was lower with automated ventilation, the number and duration of ventilator alarms were fewer with conventional ventilation. Conclusions: The quality of oxygenation with automated ventilation is not different from that with conventional ventilation. However, while automated ventilation comes with fewer manual interventions at the ventilator, it also comes with more ventilator alarms.

Safety of flow-controlled ventilation with positive and negative end-expiratory pressure in a swine model of intracranial hypertension

BackgroundPatients with brain damage often require mechanical ventilation. Although lung-protective ventilation is recommended, the application of increased positive end-expiratory pressure (PEEP) has been associated with elevated intracranial pressure (ICP) due to altered cerebral venous return. This study investigates the effects of flow-controlled ventilation (FCV) using negative end-expiratory pressures (NEEP), on cerebral hemodynamics in a swine model of intracranial hypertension.MethodsA model of intracranial hypertension involving bilateral trepan bolt holes was performed in 14 pigs. Pressure-controlled volume-guaranteed ventilation (PCV-VG) with PEEP and FCV using PEEP and then NEEP were applied. Intracranial pressure and oxygenation, as well as systemic hemodynamics and gas exchange parameters, were continuously monitored. Data were collected at baseline and at varying PEEP levels for both PCV-VG and FCV ventilation modalities. Following this, FCV ventilation and NEEP levels of -3, -6 and -9 cmH2O were applied.ResultsICP remained stable with low PEEP levels, but significantly decreased with NEEP. Lower ICP following NEEP improved cerebral perfusion pressure and cerebral tissue oxygenation (p < 0.05 for all). FCV with NEEP at EEP-6 and EEP-9 significantly improved cardiac output and mean arterial pressure (MAP), compared to PCV-VG and FCV using PEEP (p < 0.05, respectively). There were no significant differences in gas exchange parameters between modalities (PCV-VG vs FCV), and between the application of PEEP or NEEP. No significant correlations were observed between ΔICP and ΔMAP.ConclusionThe application of FCV with NEEP appears to be a safe ventilation mode and offers an additional tool for controlling severe intracranial pressure episodes. These findings warrant validation in future studies and may lead to important potential applications in clinical practice.

Determination of positive end-expiratory pressure in COVID-19-related acute respiratory distress syndrome

BACKGROUND The impact of high positive end-expiratory pressure (PEEP) ventilation and the optimization of PEEP titration in COVID-19-induced acute respiratory distress syndrome (ARDS) continues to be a subject of debate. In this systematic review, we investigated the effects of varying PEEP settings on patients with severe ARDS primarily resulting from COVID-19 (C-ARDS). OBJECTIVES Does higher or lower PEEP improve the outcomes in COVID-19 ARDS? Does individually titrated PEEP lead to better outcomes compared with PEEP set by standardised (low and high ARDS network PEEP tables) approaches? Does the individually set PEEP (best PEEP) differ from PEEP set according to the standardised approaches (low and high ARDS network PEEP tables)? DESIGN Systematic review of observational studies without metaanalysis. DATA SOURCES We performed an extensive systematic literature search in Cochrane COVID-19 Study Register (CCSR), PubMed, Embase.com, Web of Science Core Collection, World Health Organization COVID-19 Global literature on coronavirus disease, World Health Organization International Clinical Trials Registry Platform (ICTRP), medRxiv, Cochrane Central Register of Controlled Trials until 24/01/2024. ELIGIBILITY CRITERIA Ventilated adult patients (≧18 years) with C-ARDS. RESULTS We screened 16 026 records, evaluated 119 full texts, and included 12 studies (n = 1431 patients) in our final data synthesis, none of them being a randomised controlled trial. The heterogeneity of study procedures and populations did not allow conduction of a meta-analysis. The results of those studies that compared lower and higher PEEP strategies in C-ARDS were ambiguous pointing out either positive effects on oxygenation with high levels of PEEP, or negative changes in lung mechanics. CONCLUSION The available evidence does not provide sufficient guidance for recommendations on optimal PEEP settings in C-ARDS. In general, well designed platform studies are needed to answer the questions raised in this review and, in particular, to investigate the use of individualised PEEP titration techniques and the inclusion of patients with different ARDS entities, severities and disease stages. TITLE REGISTRATION Our systematic review protocol was registered with the international prospective register of systematic reviews (PROSPERO 2021: CRD42021260303).

Preliminary study: Low to moderate PEEP effects on ICP in acute neurological injury patients under mechanical ventilation

Background Acute respiratory distress syndrome (ARDS) significantly impacts mortality and prognosis in acute neurological injury patients. Positive end-expiratory pressure (PEEP) is essential in mechanical ventilation to enhance oxygenation, yet its application may elevate intracranial pressure (ICP). Studies show conflicting findings regarding PEEP's effect on ICP, particularly at low to moderate levels (5–10cmH2O), warranting further investigation in acute neurological injury cases. Objective To assess the impact of low to moderate PEEP on ICP in patients with acute neurological injury who require mechanical ventilation. Methods A retrospective analysis of 62 patients with acute neurological injury requiring mechanical ventilation at our hospital between January 2021 and September 2023 was conducted. Patients were divided into high PEEP (&gt; 10cmH2O) and low to moderate PEEP (5–10cmH2O) groups. Parameters including PaO2, PaCO2, PaO2/FiO2, driving pressure, compliance (Cst), airway resistance, such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), central venous pressure (CVP), cardiac index (CI), ICP, and cerebral perfusion pressure (CPP) were recorded pre- and post-ventilation initiation, with correlation analysis performed between ICP and other parameters. Results Pre-treatment comparisons between the high PEEP and low to moderate PEEP groups revealed no significant differences in PaO2, PaCO2, PaO2/FiO2, driving pressure, Cs, and airway resistance. However, post-treatment analysis showed significant disparities, with the high PEEP group exhibiting higher PaO2 and PaO2/FiO2 levels and lower PaCO2, driving pressure, and airway resistance levels compared to the low to moderate PEEP group. Additionally, hemodynamic parameters such as HR, SBP, DBP, CI, MAP, CVP, ICP, and CPP remained more stable in the low to moderate PEEP group post-treatment, with ICP demonstrating significant correlations with various physiological parameters. Conclusion High PEEP improves oxygenation and respiratory mechanics in acute neurological injury patients on mechanical ventilation but may affect hemodynamic parameters, ICP, and CPP. Conversely, low to moderate PEEP has minimal impact on these factors. Hence, personalized adjustment of PEEP levels is essential in clinical management.

Esophageal pressure as estimation of pleural pressure: a study in a model of eviscerated chest

BackgroundTranspulmonary pressure is the effective pressure across the lung parenchyma and has been proposed as a guide for mechanical ventilation. The pleural pressure is challenging to directly measure in clinical setting and esophageal manometry using esophageal balloon catheters was suggested for estimation. However, the accuracy of using esophageal pressure to estimate pleural pressure is debated due to variability in the mechanical properties of respiratory system, esophagus and esophageal catheter. Furthermore, while a vertical pleural pressure gradient exists across lung regions, esophageal pressure balloon provides a single value, representing, at most, the pressure surrounding the esophagus.MethodsIn a swine model with a preserved esophagus and a single homogenous, easily measurable intrathoracic pressure, we evaluated esophageal pressure’s agreement with intrathoracic pressure at different positive end-expiratory pressure (PEEP) levels (0, 5, 10, 15 cmH2O). We assessed the improvement of measurement accuracy by correcting absolute esophageal values using a previously described technique, that accounts for the pressure generated by the esophageal wall in response to esophageal balloon inflation.The study involved five swine, wherein two different esophageal catheters were used alongside the four distinct PEEP levels. Swings, uncorrected and corrected absolute esophageal pressures (end-inspiratory, end-expiratory) were compared with their respective intrathoracic pressures. The effect of correction technique was assessed with manual incremental step inflation procedure.ResultsWe found that both catheters significantly overestimated absolute esophageal pressure compared to intrathoracic pressure (5.01 ± 3.32 and 6.06 ± 5.62 cmH2O at end-expiration and end-inspiration, respectively), with error increasing at higher positive end-expiratory pressure levels (end-expiration: 2.36 ± 2.03, 3.77 ± 1.37, 6.24 ± 2.51 and 7.69 ± 4.02 for each PEEP level, P < 0.0001; end-inspiration: 1.71 ± 2.10, 3.70 ± 1.73, 7.67 ± 3.62 and 11.14 ± 7.60 for each PEEP level, P = 0.0004).Applying the correction technique significantly improved agreement for absolute values (0.82 ± 1.62 and 1.86 ± 3.94 cmH2O at end-expiration and end-inspiration, respectively). Esophageal pressure swings accurately estimated intrathoracic pressure swings at low-medium intrathoracic pressures (-0.64 ± 0.62, -0.07 ± 0.53, 1.43 ± 1.51, and 3.45 ± 3.94 at PEEP 0, 5, 10 and 15 cmH2O, respectively; P = 0.0197).ConclusionsThe correction technique, based on the mechanical response of esophageal wall to the balloon inflation, is fundamental for obtaining reliable estimations of absolute intrathoracic pressure values, and for ensuring its correct application in clinical setting.

Risk factors affecting the development of pneumothorax in patients followed up in intensive care with a diagnosis of COVID-19

BackgroundPneumothorax is a little known and reported complication of COVID-19. These patients have poorer general outcomes and greater respiratory support requirements, longer hospitalization times, and higher mortality rates. The purpose of this study was to determine which factors predict mortality in patients with tube thoracostomy diagnosed with COVID-19, admitted to the COVID-19 intensive care unit (ICU), and developing pneumothorax.MethodsThis respective, observational study was conducted in all COVID-19 ICUs at the Marmara University Pendik Training and Research Hospital, Türkiye. Patients admitted to the ICU with diagnoses of COVID-19 pneumonia and with chest tubes inserted due to pneumothorax were investigated retrospectively.ResultsOne hundred patients with tube thoracostomy were included in the study. Their median age was 68 (57–78), and 63% were men. The median follow-up time was 20 [10–29] days, and the median time from initial reverse transcriptase polymerase chain reaction (RT-PCR) results to tube thoracostomy was 17 [9–23] days. Initial RT-PCR results were positive in 90% of the patients, while 8% were negative, and 2% were unknown. Half the patients exhibited pulmonary involvement at thoracic computed tomography (CT) (n = 50), while 22 patients had COVID-19 reporting and data system (CO-RADS) scores of 5 (22%). Sixty-two patients underwent right tube thoracostomy, 24 left side placement, and 14 bilateral placement. The patients’ mean positive end expiratory pressure (PEEP) level was 10.31 (4.48) cm H2O, with a mean peak inspiratory pressure (PIP) level of 26.69 (5.95) cm H2O, a mean fraction of inspired oxygen (FiO2) level of 80.06 (21.11) %, a mean respiratory rate of 23.71 (5.62) breaths/min, and a mean high flow nasal cannula (HFNC) flow rate of 70 (8.17) L/min. Eighty-seven patients were intubated (87%), six used non-rebreathable reservoir masks, four HFNC, two non-invasive mechanical ventilation (NIV), and one a simple face mask. Comorbidity was present in 70 patients, 25 had no comorbidity, and the comorbidity status of five was unknown. Comorbidities included hypertension (38%), diabetes mellitus (23%), cardiovascular disease (12%), chronic obstructive pulmonary disease (5%), malignancy (3%), rheumatological diseases (3%), dementia (2%) and other diseases (9%). Twelve of the 100 patients survived. The median survival time was 20 (17.82–22.18) days, and the median 28-day overall survival rate was 29% (20-38%). The multivariate Cox proportional hazards model indicated that age over 68 (HR = 2.23 [95% CI: 1.39–3.56]; p = 0.001), oxygenation status other than by intubation (HR = 2.24 [95% CI: 1.11–4.52]; p = 0.024), and HCO3- below 22 compared with a normal range of 22 to 26 (HR = 1.95 [95% CI: 1.08–3.50]; p = 0.026) were risk factors associated with mortality in patients in the ICU.ConclusionsAge over 68, receipt of oxygenation other than by intubation, and HCO3- values lower than 22 in patients with COVID-19 pneumonia emerged as prognostic factors associated with mortality in terms of pneumothorax.

Spontaneous breathing trials should be adapted for each patient according to the critical illness. A new individualised approach: the GLOBAL WEAN study.

Spontaneous breathing trials (SBT) evaluate the patient's capacity to maintain inspiratory effort after extubation. SBT practices are heterogeneous and not individualised. The objective of this study was to assess which SBT best reproduces inspiratory effort after extubation in five critical illnesses. In this multicentre randomized cross-over study, adult intensive care unit patients under invasive mechanical ventilation for at least 24-h and ready for extubation, underwent three 15-min SBTs in random order: pressure support ventilation level of 7-cmH2O with positive end-expiratory pressure (PEEP) level of 0-cmH2O (PSV7PEEP0), PSV 0-cmH2O with PEEP 0-cmH2O (PSV0PEEP0) and T-piece trial. Primary outcome was the variation of pressure-time-product per minute (PTPmin) between each SBT and 20-min after extubation. Five categories of critical illnesses were selected: abdominal surgery, brain injury, chest trauma, chronic obstructive pulmonary disease (COPD) and miscellaneous. Five hundred measures of effort from 100 patients were analysed. PTPmin (cmH2O s/min, median and interquartile range, IQR) was 256 (208-321) after extubation, 192 (127-281) at the end of PSV7PEEP0 (p < 0.001 in comparison to after extubation), 291 (235-347) at the end of PSV0PEEP0 and 262 (198-338) at the end of T-piece (both no different from after extubation). One method of SBT in patients with brain injury (PSV0PEEP0), two in abdominal surgery (PSV0PEEP0 and T-piece) and miscellaneous patients (PSV7PEEP0 and T-piece) and all three methods in chest trauma and COPD exacerbation patients replicated reasonably accurately the postextubation effort to breathe. Unassisted SBTs, namely PSV0PEEP0 and T-piece trial, are the most appropriate to replicate the postextubation effort to breathe.

Measurement of intrinsic positive end-expiratory pressure and clinical outcomes of infants with severe bronchopulmonary dysplasia

To investigate the levels of intrinsic positive end-expiratory pressure (PEEPi) in infants with severe bronchopulmonary dysplasia (sBPD) and the relationship between different levels of PEEPi and clinical outcomes. A retrospective analysis was conducted on the clinical data of 12 sBPD infants who underwent PEEPi measurement and were hospitalized at Guangzhou Women and Children's Medical Center from January 2022 to June 2023. The clinical manifestations and outcomes at discharge were compared between infants with very high PEEPi (≥10 cmH2O) and those with lower PEEPi (<10 cmH2O). PEEPi measurements were taken in 12 sBPD infants between gestational age 31+3 and 67+2 weeks postmenstrual age, with the lowest PEEPi measured at 0.9 cmH2O and the highest at 19.6 cmH2O; 50% (6/12) of the infants had PEEPi ≥10 cmH2O. All infants with very high PEEPi exhibited ineffective triggering and patient-ventilator asynchrony. Among them, 5 infants could not be weaned off invasive ventilation, resulting in 4 deaths and 1 infant being discharged with a tracheostomy and ventilator support. In contrast, among the infants with PEEPi <10 cmH2O, only 1 infant died, while the others were successfully extubated and discharged. Infants with sBPD may have elevated PEEPi levels, and very high PEEPi may be associated with adverse outcomes in these patients.

Adapting general anaesthesia for a patient with class III obesity and obstructive sleep apnoea undergoing day case laparoscopic cholecystectomy: A case report.

This report describes the anaesthesia provided for a class III obese patient with obstructive sleep apnoea, undergoing an elective laparoscopic cholecystectomy. Several adaptations were required to provide safe anaesthesia. A McGrath video laryngoscopy was utilised for intubation. The patient was positioned in the ramped position, thereby increasing time to desaturation on induction of anaesthesia. Pressure controlled ventilation - volume guaranteed mode was selected for ventilation to provide consistent tidal volumes. An increased level of positive end-expiratory pressure was utilised to minimise atelectasis. Drug doses were carefully considered and calculated with the aid of The Society for Obesity and Bariatric Anaesthesia dose calculator. The airway management adaptations provided an unobstructed view for intubation. Peak airway pressures during surgery remained within safe limits and no atelectasis was evident postoperatively. Pain was kept under control and desaturation was avoided during postanaesthetic care. The patient was discharged home later that evening.

Heterogeneous impact of Sighs on mortality in patients with acute hypoxemic respiratory failure: insights from the PROTECTION study.

Sigh breaths may impact outcomes in acute hypoxemic respiratory failure (AHRF) during assisted mechanical ventilation. We investigated whether sigh breaths may impact mortality in predefined subgroups of patients enrolled in the PROTECTION multicenter clinical trial according to: 1.the physiological response in oxygenation to Sigh (responders versus non-responders) and 2.the set levels of positive end-expiratory pressure (PEEP) (High vs. Low-PEEP). If mortality differed between Sigh and No Sigh, we explored physiological daily differences at 7-days. Patients were randomized to pressure support ventilation (PSV) with Sigh (Sigh group) versus PSV with no sigh (No Sigh group). (1) Sighs were not associated with differences in 28-day mortality in responders to baseline sigh-test. Contrarily-in non-responders-56 patients were randomized to Sigh (55%) and 28-day mortality was lower with sighs (17%vs.36%, log-rank p = 0.031). (2) In patients with PEEP > 8cmH2O no difference in mortality was observed with sighs. With Low-PEEP, 54 patients were randomized to Sigh (48%). Mortality at 28-day was reduced in patients randomised to sighs (13%vs.31%, log-rank p = 0.021). These findings were robust to multivariable adjustments. Tidal volume, respiratory rate and ventilatory ratio decreased with Sigh as compared with No Sigh at 7-days. Ventilatory ratio was associated with mortality and successful extubation in both non-responders and Low-PEEP. Addition of Sigh to PSV could reduce mortality in AHRF non-responder to Sigh and exposed to Low-PEEP. Results in non-responders were not expected. Findings in the low PEEP group may indicate that insufficient PEEP was used or that Low PEEP may be used with Sigh. Sigh may reduce mortality by decreasing physiologic dead space and ventilation intensity and/or optimizing ventilation/perfusion mismatch. ClinicalTrials.gov; Identifier: NCT03201263.

Physiological definition for region of interest selection in electrical impedance tomography data: description and validation of a novel method

Objective. Geometrical region of interest (ROI) selection in electrical impedance tomography (EIT) monitoring may lack sensitivity to subtle changes in ventilation distribution. Therefore, we demonstrate a new physiological method for ROI definition. This is relevant when using ROIs to compute subsequent EIT-parameters, such as the ventral-to-dorsal ratio during a positive end-expiratory pressure (PEEP) trial.Approach.Our physiological approach divides an EIT image to ensure exactly 50% tidal impedance variation in the ventral and dorsal region. To demonstrate the effects of our new method, EIT measurements during a decremental PEEP trial in 49 mechanically ventilated ICU-patients were used. We compared the center of ventilation (CoV), a robust parameter for changes in ventro-dorsal ventilation distribution, to our physiological ROI selection method and different commonly used ROI selection methods. Moreover, we determined the impact of different ROI selection methods on the PEEP level corresponding to a ventral-to-dorsal ratio closest to 1.Main results.The division line separating the ventral and dorsal ROI was closer to the CoV for our new physiological method for ROI selection compared to geometrical ROI definition. Moreover, the PEEP level corresponding to a ventral-to-dorsal ratio of 1 is strongly influenced by the chosen ROI selection method, which could have a profound clinical impact; the within-subject range of PEEP level was 6.2 cmH2O depending on the chosen ROI selection method.Significance.Our novel physiological method for ROI definition is sensitive to subtle ventilation-induced changes in regional impedance (i.e. due to (de)recruitment) during mechanical ventilation, similar to the CoV.

Impact of airway closure and lung collapse on inhaled nitric oxide effect in acute lung injury: an experimental study

BackgroundEfficacy of inhaled therapy such as Nitric Oxide (iNO) during mechanical ventilation may depend on airway patency. We hypothesized that airway closure and lung collapse, countered by positive end-expiratory pressure (PEEP), influence iNO efficacy. This could support the role of an adequate PEEP titration for inhalation therapy. The main aim of this study was to assess the effect of iNO with PEEP set above or below the airway opening pressure (AOP) generated by airway closure, on hemodynamics and gas exchange in swine models of acute respiratory distress syndrome. Fourteen pigs randomly underwent either bilateral or asymmetrical two-hit model of lung injury. Airway closure and lung collapse were measured with electrical impedance tomography as well as ventilation/perfusion ratio (V/Q). After AOP detection, the effect of iNO (10ppm) was studied with PEEP set randomly above or below regional AOP. Respiratory mechanics, hemodynamics, and gas-exchange were recorded.ResultsAll pigs presented airway closure (AOP > 0.5cmH2O) after injury. In bilateral injury, iNO was associated with an improved mean pulmonary pressure from 49 ± 8 to 42 ± 7mmHg; (p = 0.003), and ventilation/perfusion matching, caused by a reduction in pixels with low V/Q and shunt from 16%[IQR:13–19] to 9%[IQR:4–12] (p = 0.03) only at PEEP set above AOP. iNO had no effect on hemodynamics or gas exchange for PEEP below AOP (low V/Q 25%[IQR:16–30] to 23%[IQR:14–27]; p = 0.68). In asymmetrical injury, iNO improved pulmonary hemodynamics and ventilation/perfusion matching independently from the PEEP set. iNO was associated with improved oxygenation in all cases.ConclusionsIn an animal model of bilateral lung injury, PEEP level relative to AOP markedly influences iNO efficacy on pulmonary hemodynamics and ventilation/perfusion match, independently of oxygenation.

The impact of PEEP on mechanical power and driving pressure in children with pediatric acute respiratory distress syndrome.

Positive end-expiratory pressure (PEEP) is widely used to improve oxygenation and avoid alveolar collapse in mechanically ventilated patients with pediatric acute respiratory distress syndrome (PARDS). However, its improper use can be harmful, impacting variables associated with ventilation-induced lung injury, such as mechanical power (MP) and driving pressure (∆P). Our main objective was to assess the impact of increasing PEEP on MP and ∆P in children with PARDS. Mechanically ventilated children on pressure-controlled volume-guaranteed mode were prospectively assessed for inclusion. PEEP was sequentially changed to 5, 12, 10, 8, and again to 5 cm H2O. After 10 min at each PEEP level, ventilatory data were collected and then variables of interest were determined. Respiratory system mechanics were measured using the least squares fitting method. Thirty-one patients were included, with median age and weight of 6 months and 6.3 kg. Most subjects were admitted for acute viral bronchiolitis (45%) or community-acquired pneumonia (32%) and were diagnosed with mild (45%) or moderate (42%) PARDS. There was a significant increase in MP and ∆P at PEEP levels of 10 and 12 cm H2O. When PEEP was increased from 5 to 12 cm H2O, there was a relative increase in MP of 60.7% (IQR 49.3-82.9) and in ΔP of 33.3% (IQR 17.8-65.8). A positive correlation was observed between MP and ΔP (ρ = 0.59). Children with mild or moderate PARDS may experience a significant increase in MP and ∆P with increased PEEP. Therefore, respiratory system mechanics and lung recruitability must be carefully evaluated during PEEP titration.

Effects of different masks on diaphragm motion in OSAS patients undergoing CPAP: results from an ultrasound-based proof of concept study.

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway narrowing or collapse during sleep. Continuous positive airway pressure (CPAP) remains the preferred treatment in selected patients and masks' choice plays an important role for subsequent respiratory events' reduction. It is known that oronasal masks are not as effective at opening the upper airway compared to nasal ones. Thus, the objective of this study was to investigate differences in US-assessed diaphragmatic excursion (DE) using oronasal vs. nasal CPAP masks. This observational study included 50 OSA patients presenting a moderate to severe apnea-hypopneaindex and requiring CPAP treatment. All participants received US evaluations on diaphragm motion during their oronasal and nasal CPAP trial at equal positive end-expiratory pressure level. The difference of DE switching mask during CPAP was assessed by using the non-parametric Wilcoxon signed-rank test. A statistically significant increase in US- assessed DE was found when shifting from oronasal to nasal mask (p-value < 0.01). Linear regression models revealed that increased neck circumference and more severe AHI were associated with decreased DE when shifting to an oronasal mask. This study evaluated the acute impact on US-assessed DE after changing CPAP route from oronasal to nasal mask. Our results suggest that the nasal type should be the more suitable option for most patients with OSA, especially those with higher nasal circumference. Diaphragmatic motion throughout US may become a practical tool to help in the choice of the fittest mask in patients undergoing CPAP.

A Comparison of the Effects of Different Positive End-Expiratory Pressure Levels on Respiratory Parameters During Prone Positioning Under General Anaesthesia: A Randomized Controlled Trial.

Background and objective In general anesthesia, for certain surgical procedures in the prone position, patients often face increased airway pressures, reduced pulmonary and thoracic compliance, and restricted chest expansion, all of which can affect venous return and cardiac output, impacting overall hemodynamic stability. Positive end-expiratory pressure (PEEP) is used to address these issues by improving lung recruitment and ventilation while reducing stress on lung units. However, different PEEP levels also present risks such as increased parenchymal strain, higher pulmonary vascular resistance, and impaired venous return. Proper positioning and frequent monitoring are key to ensuring adequate oxygenation and minimizing complicationsarising from prolonged periods in the prone position. This study aimed to evaluate the effects of different PEEP levels (0 cmH2O, 5 cmH2O, and 10 cmH2O) in the prone position to determine the optimal setting for balancing improved oxygenation and lung recruitment against potential adverse effects. The goal is to refine individualized PEEP strategies beyond what is typically outlined in standard PEEP tables. We endeavored to examine the impact of different PEEP levels during pressure-controlled ventilation (PCV) on arterial oxygenation, respiratory parameters, and intraoperative blood loss in patients undergoing spine surgery in a prone position under general anesthesia. Methodology This randomized, single-blinded, controlled study enrolled 90 patients scheduled for elective spine fixation surgeries. Patients were randomized into three groups: Group A (PEEP 0), Group B (PEEP 5), and Group C (PEEP 10). Standardized anesthesia protocols were administered to all groups, with ventilation set to pressure-controlled mode at desired levels. PEEP levels were adjusted according to group allocation. Arterial blood gases were measured before induction, 30 minutes after prone positioning, and 30 minutes post-extubation. Arterial line insertion was performed, and dynamic compliance, mean arterial pressure (MAP), heart rate (HR), and intraoperative blood loss were recorded at regular intervals. Data were analyzed using SPSS Statistics version 21 (IBM Corp., Armonk, NY). Results Arterial oxygenation was significantly higher in Groups B (PEEP 5) and C (PEEP 10) compared to Group A (PEEP 0) at both 30 minutes post-intubation and post-extubation. Specifically, at 30 minutes post-intubation, arterial oxygenation was 142.26 ±24.7 in Group B and 154.9 ±29.88 in Group C, compared to 128.18 ±13.3 in Group A (p=0.002). Similarly, post-extubation arterial oxygenation levels were 105.1 ±8.28 for Group B and 115.46 ±15.2 for Group C, while Group A had levels of 97.07 ±9.90 (p<0.001). MAP decreased significantly in Groups B and C compared to Group A. Dynamic compliance was also improved in Groups B and C. Furthermore, intraoperative blood loss was notably lower in Group C (329.66 ±93.93) and Group B (421.16 ±104.52) compared to Group A (466.66 ±153.76), and these differences were statistically significant. Conclusions Higher levels of PEEP (10 and 5 cmH2O) during prone positioning in spine surgery improve arterial oxygenation, dynamic compliance, and hemodynamic stability while reducing intraoperative blood loss. These findings emphasize the importance of optimizing ventilatory support to enhance patient outcomes during prone-position surgeries.

A novel positive end-expiratory pressure titration using electrical impedance tomography in spontaneously breathing acute respiratory distress syndrome patients on mechanical ventilation: an observational study from the MaastrICCht cohort.

There is no universally accepted method for positive end expiratory pressure (PEEP) titration approach for patients on spontaneous mechanical ventilation (SMV). Electrical impedance tomography (EIT) guided PEEP-titration has shown promising results in controlled mechanical ventilation (CMV), current implemented algorithm for PEEP titration (based on regional compliance measurements) is not applicable in SMV. Regional peak flow (RPF, defined as the highest inspiratory flow rate based on EIT at a certain PEEP level) is a new method for quantifying regional lung mechanics designed for SMV. The objective is to study whether RPF by EIT is a feasible method for PEEP titration during SMV. Single EIT measurements were performed in COVID-19 ARDS patients on SMV. Clinical (i.e., tidal volume, airway occlusion pressure, end-tidal CO2) and mechanical (cyclic alveolar recruitment, recruitment, cumulative overdistension (OD), cumulative collapse (CL), pendelluft, and PEEP) outcomes were determined by EIT at several pre-defined PEEP thresholds (1-10% CL and the intersection of the OD and CL curves) and outcomes at all thresholds were compared to the outcomes at baseline PEEP. In total, 25 patients were included. No significant and clinically relevant differences were found between thresholds for tidal volume, end-tidal CO2, and P0.1 compared to baseline PEEP; cyclic alveolar recruitment rates changed by -3.9% to -37.9% across thresholds; recruitment rates ranged from - 49.4% to + 79.2%; cumulative overdistension changed from - 75.9% to + 373.4% across thresholds; cumulative collapse changed from 0% to -94.3%; PEEP levels from 10 up to 14 cmH2O were observed across thresholds compared to baseline PEEP of 10 cmH2O. A threshold of approximately 5% cumulative collapse yields the optimum compromise between all clinical and mechanical outcomes. EIT-guided PEEP titration by the RPF approach is feasible and is linked to improved overall lung mechanics) during SMV using a threshold of approximately 5% CL. However, the long-term clinical safety and effect of this approach remain to be determined.