Levels Of End-expiratory Pressure Research Articles

Dynamic relative regional lung strain estimated by computed tomography and electrical impedance tomography in ARDS patients

BackgroundIn the acute distress respiratory syndrome (ARDS), specific lung regions can be exposed to excessive strain due to heterogeneous disease, gravity-dependent lung collapse and injurious mechanical ventilation. Computed tomography (CT) is the gold standard for regional strain assessment. An alternative tool could be the electrical impedance tomography (EIT). We aimed to determine whether EIT-based methods can predict the dynamic relative regional strain (DRRS) between two levels of end-expiratory pressure (PEEP) in gravity-non-dependent and dependent lung regions.MethodsFourteen ARDS patients underwent CT and EIT acquisitions (at end-inspiratory and end-expiratory) at two levels of PEEP: a low-PEEP based on ARDS-net strategy and a high-PEEP titrated according to EIT. Three EIT-based methods for DRRS were compared to relative CT-based strain: (1) the change of the ratio between EIT ventilation and end-expiratory lung impedance in arbitrary units ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]), (2) the change of ΔZ/EELI ratio calibrated to mL ([ΔZml low-PEEP/EELIml low-PEEP]/[ΔZml high-PEEP/EELIml high-PEEP]) using CT data, and (3) the relative change of ∆ZAU (∆ZAU low-PEEP/∆ZAU high-PEEP). We performed linear regressions analysis and calculated bias and limits of agreement to assess the performance of DRRS by EIT in comparison with CT.ResultsThe DRRS assessed by (ΔZml low-PEEP/EELIml low-PEEP)/(ΔZml high-PEEP/EELIml high-PEEP) and ∆ZAU low-PEEP/∆ZAU high-PEEP showed good relationship and agreement with the CT method (R2 of 0.9050 and 0.8679, respectively, in non-dependent region; R2 of 0.8373 and 0.6588, respectively, in dependent region; biases ranging from − 0.11 to 0.51 and limits of agreement ranging from − 0.73 to 1.16 for both methods and lung regions). Conversely, DRRS based on EELIAU ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]) exhibited a weak negative relationship and poor agreement with the CT method for both non-dependent and dependent regions (R2 ~ 0.3; bias of 3.11 and 2.08, and limits of agreement of − 2.13 to 8.34 and from − 1.49 to 5.64, respectively).ConclusionChanges in DRRS during a PEEP trial in ARDS patients could be monitored using EIT, based on changes in ΔZmL/EELIml and ∆ZAU. The relative change ∆ZAU offers the advantage of not requiring CT data for calibration.

Cardiovascular and Gas Exchange Effects of Individualized Positive End-Expiratory Pressures in Cats Anesthetized With Isoflurane.

ObjectivesTo compare the effects of four levels of end-expiratory pressure [zero (ZEEP) and three levels of positive end-expiratory pressure (PEEP)] on the cardiovascular system and gas exchange of cats anesthetized with isoflurane and mechanically ventilated for 3 h with a tidal volume of 10 ml/kg.Study DesignProspective, randomized, controlled trial.AnimalsSix healthy male neutered purpose-bred cats.MethodsAnesthesia was induced with isoflurane and maintained at 1.3 minimum alveolar concentration. PEEP of maximal respiratory compliance (PEEPmaxCrs) was identified in a decremental PEEP titration, and cats were randomly ventilated for 3 h with one of the following end-expiratory pressures: ZEEP, PEEPmaxCrs minus 2 cmH2O (PEEPmaxCrs−2), PEEPmaxCrs, and PEEPmaxCrs plus 2 cmH2O (PEEPmaxCrs+2). Cardiovascular and gas exchange variables were recorded at 5, 30, 60, 120, and 180 min (T5 to T180, respectively) of ventilation and compared between and within ventilation treatments with mixed-model ANOVA followed by Dunnet's and Tukey's tests (normal distribution) or Friedman test followed by the Dunn's test (non-normal distribution). Significance to reject the null hypothesis was considered p < 0.05.ResultsMean arterial pressure (MAP—mmHg) was lower in PEEPmaxCrs+2 [63 (49–69); median (range)] when compared to ZEEP [71 (67–113)] at T5 and stroke index (ml/beat/kg) was lower in PEEPmaxCrs+2 (0.70 ± 0.20; mean ± SD) than in ZEEP (0.90 ± 0.20) at T60. Cardiac index, oxygen delivery index (DO2I), systemic vascular resistance index, and shunt fraction were not significantly different between treatments. The ratio between arterial partial pressure and inspired concentration of oxygen (PaO2/FIO2) was lower in ZEEP than in the PEEP treatments at various time points. At T180, DO2I was higher when compared to T5 in PEEPmaxCrs. Dopamine was required to maintain MAP higher than 60 mmHg in one cat during PEEPmaxCrs and in three cats during PEEPmaxCrs+2.ConclusionIn cats anesthetized with isoflurane and mechanically ventilated for 3 h, all levels of PEEP mildly improved gas exchange with no significant difference in DO2I when compared to ZEEP. The PEEP levels higher than PEEPmaxCrs−2 caused more cardiovascular depression, and dopamine was an effective treatment. A temporal increase in DO2I was observed in the cats ventilated with PEEPmaxCrs. The effects of these levels of PEEP on respiratory mechanics, ventilation-induced lung injury, as well as in obese and critically ill cats deserve future investigation for a better understanding of the clinical use of PEEP in this species.

Potential for the lung recruitment and the risk of lung overdistension during 21\xa0days of mechanical ventilation in patients with\xa0 COVID-19 after noninvasive ventilation failure: the COVID-VENT observational trial

BackgroundData on the lung respiratory mechanics and gas exchange in the time course of COVID-19-associated respiratory failure is limited. This study aimed to explore respiratory mechanics and gas exchange, the lung recruitability and risk of overdistension during the time course of mechanical ventilation.MethodsThis was a prospective observational study in critically ill mechanically ventilated patients (n = 116) with COVID-19 admitted into Intensive Care Units of Sechenov University. The primary endpoints were: «optimum» positive end-expiratory pressure (PEEP) level balanced between the lowest driving pressure and the highest SpO2 and number of patients with recruitable lung on Days 1 and 7 of mechanical ventilation. We measured driving pressure at different levels of PEEP (14, 12, 10 and 8 cmH2O) with preset tidal volume, and with the increase of tidal volume by 100 ml and 200 ml at preset PEEP level, and calculated static respiratory system compliance (CRS), PaO2/FiO2, alveolar dead space and ventilatory ratio on Days 1, 3, 5, 7, 10, 14 and 21.ResultsThe «optimum» PEEP levels on Day 1 were 11.0 (10.0–12.8) cmH2O and 10.0 (9.0–12.0) cmH2O on Day 7. Positive response to recruitment was observed on Day 1 in 27.6% and on Day 7 in 9.2% of patients. PEEP increase from 10 to 14 cmH2O and VT increase by 100 and 200 ml led to a significant decrease in CRS from Day 1 to Day 14 (p < 0.05). Ventilatory ratio was 2.2 (1.7–2,7) in non-survivors and in 1.9 (1.6–2.6) survivors on Day 1 and decreased on Day 7 in survivors only (p < 0.01). PaO2/FiO2 was 105.5 (76.2–141.7) mmHg in non-survivors on Day 1 and 136.6 (106.7–160.8) in survivors (p = 0.002). In survivors, PaO2/FiO2 rose on Day 3 (p = 0.008) and then between Days 7 and 10 (p = 0.046).ConclusionLung recruitability was low in COVID-19 and decreased during the course of the disease, but lung overdistension occurred at «intermediate» PEEP and VT levels. In survivors gas exchange improvements after Day 7 mismatched CRS.Trial registrationClinicalTrials.gov, NCT04445961. Registered 24 June 2020—Retrospectively registered.

High flow nasal cannula therapy in children: working principles and treatment failure predictors

High Flow Nasal Cannula (HFNC) delivers high flowrates of a heated air/oxygen fresh gas breathing mixture, in an open system, at the exact amount of fraction inspired oxygen, and at the optimum hydration level. By definition, due to high flow rates, higher than 2 L/min, it produces a wash out of the anatomic dead space and the End-tidal Carbon dioxide (EtCO2), and augments thus effective alveolar ventilation at the same rate of minute ventilation, helping reduce partial arterial pressure of Carbon dioxide (PaCO2) levels. Although depending on mouth closure and the relative size of the nasal cannula prongs related to nares, it produces a minimum Positive End Expiratory Pressure (PEEP) level, which is especially helpful in keeping unstable alveoli open, recruiting lung volume, and increasing the functional residual capacity. It reduces respiratory resistance and the high work of breathing which is a common feature in patients with respiratory failure. But its most important characteristics are the ease of implementation and good patient tolerance. It has emerged as a promising support mode in the last decade, and its use is being continuously expanded. Although it started from neonates, it expanded to children and adults, and tested in all causes of acute hypoxemic respiratory failure, especially in bronchiolitis, and in post-extubation respiratory failure as well, starting from Emergency Department (ED), Pediatric Ward (PW), Pediatric Intensive Care Unit (PICU), and during transportation. Comparisons and meta-analyses, although not of equal modalities, have shown that it is definitely better than Standard Oxygen Therapy (SOT), and rather inferior to Continuous Positive Airway Pressure (CPAP). The aim of the present study is to explore the HFNC position in the timeline of recommendations for mechanical ventilation in critically ill children. We present a review on HFNC literature evidence in patients aged 1 month to 18 years, focusing on its mechanism of action, clinical effects, and timely recognition of treatment failure predictors.

Особливості респіраторної терапії пацієнтів з ожирінням при лапароскопічних операціях

У цьому клінічному дослідженні ми вивчали респіраторні властивості легень 40 пацієнтів із різним ступенем ожиріння під час лапароскопічних операцій. Усі пацієнти були розподілені на 4 групи: три контрольні групи (1-ша група — пацієнти без ожиріння або з надмірною вагою, 2-га група — пацієнти з 1-м та 2-м ступенем ожиріння, 3-тя група — пацієнти з морбідним ожирінням) і одну основну (4-та група — пацієнти з 1-м і 2-м ступенем ожиріння, яким застосовувалась передопераційна неінвазивна CPAP-терапія (Continues Positive Airway Pressure — постійний позитивний тиск у дихальних шляхах), а параметри штучної вентиляції були оптимізовані шляхом зміни рівня позитивного тиску в кінці видиху (ПТКВ) і застосування рекрутмент-маневру). Досліджувались такі респіраторні властивості легень: статичний комплайєнс, середній динамічний комплайєнс, загальний опір дихальних шляхів, піковий тиск вдиху й тиск плато, середній внутрішньогрудний тиск. Усі ці параметри визначалися під час загальної анестезії у встановлених контрольних точках: 1-ша контрольна точка — після інтубації; 2-га контрольна точка — після підвищення внутрішньочеревного тиску до 15 мм рт.ст.; 3-тя контрольна точка — після зменшення внутрішньочеревного тиску до 10 мм рт.ст.; 4-та контрольна точка — після нормалізації рівня внутрішньочеревного тиску. В основній групі додатково визначали ці параметри після зміни рівня ПТКВ та рекрутменту. Застосування передопераційної неінвазивної CPAP-терапії та підвищеного інтраопераційного рівня ПТКВ покращує респіраторні властивості легень, особливо в пацієнтів з ожирінням і тяжкою супутньою легеневою патологією на фоні підвищеного внутрішньочеревного тиску. Внутрішньочеревний тиск на рівні 15 мм рт.ст., що часто застосовується при лапароскопічних операціях, негативно впливає на респіраторну механіку. ПТКВ на рівні 5 см вод.ст. недостатній для підтримання «відкритих легень» у пацієнтів з ожирінням при внутрішньочеревній гіпертензії. Неінвазивна CPAP-терапія та ПТКВ на рівні 10 см вод.ст. дозволяє втримати задовільну розтяжність легень, знизити загальний опір дихальних шляхів, зменшити та провести профілактику ателектазування легень і, можливо, у подальшому скоротити час відлучення від ШВЛ.

Периоперационная протективная искусственная вентиляция легких при лапароскопических операциях у пациентов с ожирением

Актуальность. Пациенты с ожирением являются основной группой риска для формирования резорбционных ателектазов и возникновения послеоперационных легочных осложнений. Цель исследования: исследовать эффективность и безопасность принципов протективной искусственной вентиляции легких (ИВЛ) у пациентов с ожирением при абдоминальных лапароскопических операциях. На сегодняшний день доказано, что резорбционные ателектазы формируются у 90 % пациентов, которым проводится общая анестезия с ИВЛ. На фоне повышенного внутрибрюшного давления и гиповентиляции базальных отделов легких ателектазирование еще больше прогрессирует и может привести к существенным изменениям респираторной механики и гипоксемии. Основные компоненты протективной ИВЛ включают в себя: использование небольших дыхательных объемов, положительного давления конца выдоха (ПДКВ) выше физиологического уровня и проведение интраоперационного альвеолярного рекрутмента (аРМ). Материалы и методы. Всего было 24 пациента, которые были разделены на 3 группы: контрольную (ПДКВ5) и две основные (ПДКВ (10)/аРМ + ПДКВ (10)). В 4 контрольных точках общей анестезии исследовались: статический тораколегочный комплайенс, среднее внутригрудное давление и среднее артериальное давление. Результаты. Проанализировав статический тораколегочный комплайенс, лучшие результаты мы наблюдали в группе, в которой проводились аРМ в сочетании с последующим повышением ПДКВ. Относительно среднего внутригрудного давления и среднего артериального давления существенных различий и негативных изменений во всех группах пациентов не наблюдалось. Выводы. Интраоперационное сочетание альвеолярных рекрутментов и последующего повышенного уровня ПДКВ показывает увеличение тораколегочного комплайенса и может свидетельствовать об уменьшении процента ателектазированной легочной ткани. В основной группе пациентов не наблюдалось гемодинамической нестабильности после проведения аРМ и установки ПТКВ. Предварительно данные методы можно считать безопасными при лапароскопических операциях.

Closed Endotracheal Suctioning Impact on Ventilator-Related Parameters in Obstructive and Restrictive Respiratory Systems: A Bench Study

A closed suctioning system (CSS) in patients with coronavirus disease 2019 (COVID-19) prevents spraying respiratory secretions into the environment during suction. However, it is not clear whether ventilation is maintained during the suction procedure, especially in patients with compromised pulmonary mechanics. This paper determines the effects of endotracheal tube (ETT) size, suction catheter size, and two lung mechanics (resistance and compliance) on ventilator-related parameters measured during suction. Suction was performed on an adult training lung, ventilated with either volume-controlled (VC-CMV) or pressure-controlled mandatory ventilation (PC-CMV), using ETT sizes of 6.5–8.0 mm paired with suction catheter sizes of 8–14 French (Fr). Peak inspiratory pressure (PIP) increased by 50% when the ETT’s ventilation area was less than 25 mm2 in size, especially in patients with high airway resistance ventilated with VC-CMV. Positive end-expiratory pressure (PEEP) levels significantly decreased when using 14 Fr SC during VC-CMV and fewer effects during PC-CMV. Change of expiratory minute volume increased with higher outer diameter of suction catheters and decreased with severe lung compliance during PC-CMV. The change in ventilator-related parameters were intently monitored in the patient whose pulmonary mechanic was compromised through the CSS endotracheal tube suctioning procedures in clinical airway management.

How do high and low positive end-expiratory pressure (PEEP) levels compare for mechanically ventilated adults with acute lung injury and acute respiratory distress syndrome?

How do high and low positive end-expiratory pressure (PEEP) levels compare for mechanically ventilated adults with acute lung injury and acute respiratory distress syndrome?

Targeted lateral positioning decreases lung collapse and overdistension in COVID-19-associated ARDS

BackgroundAmong the challenges for personalizing the management of mechanically ventilated patients with coronavirus disease (COVID-19)-associated acute respiratory distress syndrome (ARDS) are the effects of different positive end-expiratory pressure (PEEP) levels and body positions in regional lung mechanics. Right-left lung aeration asymmetry and poorly recruitable lungs with increased recruitability with alternating body position between supine and prone have been reported. However, real-time effects of changing body position and PEEP on regional overdistension and collapse, in individual patients, remain largely unknown and not timely monitored. The aim of this study was to individualize PEEP and body positioning in order to reduce the mechanisms of ventilator-induced lung injury: collapse and overdistension.MethodsWe here report a series of five consecutive mechanically ventilated patients with COVID-19-associated ARDS in which sixteen decremental PEEP titrations were performed in the first days of mechanical ventilation (8 titration pairs: supine position immediately followed by 30° targeted lateral position). The choice of lateral tilt was based on X-Ray. This targeted lateral position strategy was defined by selecting the less aerated lung to be positioned up and the more aerated lung to be positioned down. For each PEEP level, global and regional collapse and overdistension maps and percentages were measured by electrical impedance tomography. Additionally, we present the incidence of lateral asymmetry in a cohort of forty-four patients.ResultsThe targeted lateral position strategy resulted in significantly smaller amounts of overdistension and collapse when compared with the supine one: less collapse along the PEEP titration was found within the left lung in targeted lateral (P = 0.014); and less overdistension along the PEEP titration was found within the right lung in targeted lateral (P = 0.005). Regarding collapse within the right lung and overdistension within the left lung: no differences were found for position. In the cohort of forty-four patients, ventilation inequality of > 65/35% was observed in 15% of cases.ConclusionsTargeted lateral positioning with bedside personalized PEEP provided a selective attenuation of overdistension and collapse in mechanically ventilated patients with COVID-19-associated ARDS and right-left lung aeration/ventilation asymmetry.Trial registrationTrial registration number: NCT04460859

Cardiovascular function, pulmonary gas exchange and tissue oxygenation in isoflurane-anesthetized, mechanically ventilated Beagle dogs with four levels of positive end-expiratory pressure

ObjectivesTo compare pulmonary gas exchange, tissue oxygenation and cardiovascular effects of four levels of end-expiratory pressure: no positive end-expiratory pressure (ZEEP), positive end-expiratory pressure (PEEP) of maximal respiratory system compliance (PEEPmaxCrs), PEEPmaxCrs + 2 cmH2O (PEEPmaxCrs+2), PEEPmaxCrs + 4 cmH2O (PEEPmaxCrs+4), in isoflurane-anesthetized dogs. Study designProspective randomized crossover study. AnimalsA total of seven healthy male Beagle dogs, aged 1 year and weighing 10.2 ± 0.7 kg (mean ± standard deviation). MethodsThe dogs were administered acepromazine and anesthesia was induced with propofol and maintained with isoflurane. Ventilation was controlled for 4 hours with ZEEP, PEEPmaxCrs, PEEPmaxCrs+2 or PEEPmaxCrs+4. Cardiovascular, pulmonary gas exchange and tissue oxygenation data were evaluated at 5, 60, 120, 180 and 240 minutes of ventilation and compared using a mixed-model anova followed by Bonferroni test. p < 0.05 was considered significant. ResultsCardiac index (CI) and mean arterial pressure (MAP) were lower in all PEEP treatments at 5 minutes when compared with ZEEP. CI persisted lower throughout the 4 hours only in PEEPmaxCrs+4 with the lowest CI at 5 minutes (2.15 ± 0.70 versus 3.45 ± 0.94 L minute–1 m–2). At 180 and 240 minutes, MAP was lower in PEEPmaxCrs+4 than in PEEPmaxCrs, with the lowest value at 180 minutes (58 ± 7 versus 67 ± 7 mmHg). Oxygen delivery index (DO2I) was lower in PEEPmaxCrs+4 than in ZEEP at 5, 60, 120 and 180 minutes. Venous admixture was not different among treatments. Conclusion and clinical relevanceThe use of PEEP caused a transient decrease in MAP and CI in lung-healthy dogs anesthetized with isoflurane, which improved after 60 minutes of ventilation in all levels of PEEP except PEEPmaxCrs+4. A clinically significant improvement in arterial oxygenation and DO2I was not observed with PEEPmaxCrs and PEEPmaxCrs+2 in comparison with ZEEP, whereas PEEPmaxCrs+4 decreased DO2I.

Lower Levels of Positive End-Expiratory Pressure Didn't Harm Patients Without Acute Respiratory Distress Syndrome

Low tidal volume ventilation, often with high levels of positive end-expiratory pressure (PEEP), is the standard of care for patients with acute

How do high and low positive end-expiratory pressure (PEEP) levels compare for mechanically ventilated adults with acute lung injury and acute respiratory distress syndrome?

How do high and low positive end-expiratory pressure (PEEP) levels compare for mechanically ventilated adults with acute lung injury and acute respiratory distress syndrome?

Autotitrating external positive end-expiratory airway pressure to abolish expiratory flow limitation during tidal breathing in patients with severe COPD: a physiological study.

The optimal noninvasive application of external positive end-expiratory pressure (EPAP) to abolish tidal-breathing expiratory flow limitation (EFLT) and minimise intrinsic positive end-expiratory pressure (PEEPi) is challenging in COPD patients. We investigated whether auto-titrating EPAP, using the forced oscillation technique (FOT) to detect and abolish EFLT, would minimise PEEPi, work of breathing and neural respiratory drive (NRD) in patients with severe COPD. Patients with COPD with chronic respiratory failure underwent auto-titration of EPAP using a FOT-based algorithm that detected EFLT. Once optimal EPAP was identified, manual titration was performed to assess NRD (using diaphragm and parasternal intercostal muscle electromyography, EMGdi and EMGpara, respectively), transdiaphragmatic inspiratory pressure swings (ΔP di), transdiaphragmatic pressure-time product (PTPdi) and PEEPi, between EPAP levels 2 cmH2O below to 3 cmH2O above optimal EPAP. Of 10 patients enrolled (age 65±6 years; male 60%; body mass index 27.6±7.2 kg.m-2; forced expiratory volume in 1 s 28.4±8.3% predicted), eight had EFLT, and optimal EPAP was 9 (range 4-13) cmH2O. NRD was reduced from baseline EPAP at 1 cmH2O below optimal EPAP on EMGdi and at optimal EPAP on EMGpara. In addition, at optimal EPAP, PEEPi (0.80±1.27 cmH2O versus 1.95± 1.70 cmH2O; p<0.05) was reduced compared with baseline. PTPdi (10.3±7.8 cmH2O·s-1 versus 16.8±8.8 cmH2O·s-1; p<0.05) and ΔP di (12.4±7.8 cmH2O versus 18.2±5.1 cmH2O; p<0.05) were reduced at optimal EPAP+1 cmH2O compared with baseline. Autotitration of EPAP, using a FOT-based algorithm to abolish EFLT, minimises transdiaphragmatic pressure swings and NRD in patients with COPD and chronic respiratory failure.

Management of Respiratory Distress Syndrome in Preterm Infants In Wales: A Full Audit Cycle of a Quality Improvement Project

Respiratory Distress Syndrome (RDS) is the commonest diagnosis after premature birth. We aimed to audit clinical practices before and after introduction of a national guideline in Wales on RDS management. Anonymised, prospective data on all infants born at <34 weeks of gestation and cared for at one of the participating neonatal units in Wales were collected in two six-month time periods in 2015 and 2018. A national guideline was introduced in 2016 by the Wales Neonatal Network. Data collection included areas of antenatal management, delivery room stabilisation, invasive and non-invasive respiratory support, surfactant treatment and elements of supportive care. Univariate and multivariate methods were used to compare data between the two epochs. Comparing care before and after introduction of the national guideline, areas of significant improvement include use of targeted tidal volume ventilation, use of caffeine therapy, oxygen therapy post-surfactant and increasing early use of parenteral nutrition. Areas of poorer management included levels of positive end expiratory pressures and timing of introduction of enteral feeds. Little variation was seen between level two and three units, although gestational age was a significant independent variable for several practices, including delayed cord clamping, stabilisation with intubation, early enteral feeding and caffeine administration. A national guideline for management of RDS in Wales has significantly improved practice in several areas. However, despite a large volume of high-quality evidence and robust guidance, there remains a significant variation in some elements of best practice for RDS management. Further work should focus on education and training, especially for elements requiring cross-departmental work.

Lung aeration distribution in anesthetized Beagles ventilated with lower or higher tidal volume in three different levels of end expiratory pressure: a computed tomography study

Lung aeration distribution in anesthetized Beagles ventilated with lower or higher tidal volume in three different levels of end expiratory pressure: a computed tomography study

High-frequency oscillatory ventilation guided by transpulmonary pressure in acute respiratory syndrome: an experimental study in pigs

BackgroundRecent clinical studies have not shown an overall benefit of high-frequency oscillatory ventilation (HFOV), possibly due to injurious or non-individualized HFOV settings. We compared conventional HFOV (HFOVcon) settings with HFOV settings based on mean transpulmonary pressures (PLmean) in an animal model of experimental acute respiratory distress syndrome (ARDS).MethodsARDS was induced in eight pigs by intrabronchial installation of hydrochloric acid (0.1 N, pH 1.1; 2.5 ml/kg body weight). The animals were initially ventilated in volume-controlled mode with low tidal volumes (6 ml kg− 1) at three positive end-expiratory pressure (PEEP) levels (5, 10, 20 cmH2O) followed by HFOVcon and then HFOV PLmean each at PEEP 10 and 20.The continuous distending pressure (CDP) during HFOVcon was set at mean airway pressure plus 5 cmH2O. For HFOV PLmean it was set at mean PL plus 5 cmH2O. Baseline measurements were obtained before and after induction of ARDS under volume controlled ventilation with PEEP 5. The same measurements and computer tomography of the thorax were then performed under all ventilatory regimens at PEEP 10 and 20.ResultsCardiac output, stroke volume, mean arterial pressure and intrathoracic blood volume index were significantly higher during HFOV PLmean than during HFOVcon at PEEP 20. Lung density, total lung volume, and normally and poorly aerated lung areas were significantly greater during HFOVcon, while there was less over-aerated lung tissue in HFOV PLmean. The groups did not differ in oxygenation or extravascular lung water index.ConclusionHFOV PLmean is associated with less hemodynamic compromise and less pulmonary overdistension than HFOVcon. Despite the increase in non-ventilated lung areas, oxygenation improved with both regimens. An individualized approach with HFOV settings based on transpulmonary pressure could be a useful ventilatory strategy in patients with ARDS. Providing alveolar stabilization with HFOV while avoiding harmful distending pressures and pulmonary overdistension might be a key in the context of ventilator-induced lung injury.

Alveolar Tidal recruitment/derecruitment and Overdistension During Four Levels of End-Expiratory Pressure with Protective Tidal Volume During Anesthesia in a Murine Lung-Healthy Model.

We compared respiratory mechanics between the positive end-expiratory pressure of minimal respiratory system elastance (PEEPminErs) and three levels of PEEP during low-tidal-volume (6mL/kg) ventilation in rats. Twenty-four rats were anesthetized, paralyzed, and mechanically ventilated. Airway pressure (Paw), flow (F), and volume (V) were fitted by a linear single compartment model (LSCM) Paw(t) = Ers × V(t) + Rrs × F(t) + PEEP or a volume- and flow-dependent SCM (VFDSCM) Paw(t) = (E1 + E2 × V(t)) × V(t)+(K1 + K2 × |F(t)|) × F(t) + PEEP, where Ers and Rrs are respiratory system elastance and resistance, respectively; E1 and E2× V are volume-independent and volume-dependent Ers, respectively; and K1 and K2 × F are flow-independent and flow-dependent Rrs, respectively. Animals were ventilated for 1h at PEEP 0cmH2O (ZEEP); PEEPminErs; 2cmH2O above PEEPminErs (PEEPminErs+2); or 4cmH2O above PEEPminErs (PEEPminErs+4). Alveolar tidal recruitment/derecruitment and overdistension were assessed by the index %E2 = 100 × [(E2 × VT)/(E1+|E2| × VT)], and alveolar stability by the slope of Ers(t). %E2 varied between 0 and 30% at PEEPminErs in most respiratory cycles. Alveolar Tidal recruitment/derecruitment (%E2 < 0) and overdistension (%E2 > 30) were predominant in the absence of PEEP and in PEEP levels higher than PEEPminErs, respectively. The slope of Ers(t) was different from zero in all groups besides PEEPminErs+4. PEEPminErs presented the best compromise between alveolar tidal recruitment/derecruitment and overdistension, during 1h of low-VT mechanical ventilation.

Standardized Use of Recruitment Maneuvers Leads to Higher Mortality in Acute Respiratory Distress Syndrome Patients

To mitigate ventilator-induced lung injury, finding the “right” level of positive end-expiratory pressure (PEEP) for a patient with acute respiratory

The Effects of Positive End-Expiratory Pressure at Different Levels on Postoperative Respiration Parameters in Patients Undergoing Laparoscopic Cholecystectomy

ABSTRACTPurpose/Aim of the study: We investigated the effects of different positive end-expiratory pressure (PEEP) levels on postoperative respiration parameters in patients undergoing laparoscopic cholecystectomy. Materials and Methods: One hundred and five consecutive patients were randomly divided to three groups (n = 35, for each group). Group I did not receive PEEP whereas group II received PEEP as 5 cmH2O and group III received PEEP as 8 cm H2O. Measurements with spirometer were taken 1 hour before the operation (T1) and, 1 (T2), 6 (T3), and 24 hours (T4) after extubation by an anesthetist. Forced expiratory volume (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF) were recorded. Results: Group I had higher FVC values measured at T2 time point compared with other groups (p < 0.05, for both groups). There was a statistically significant difference between group I and group III in terms of the FVC values measured at T3 and T4 time points (p = 0.05 and p < 0.05, retrospectively). A statistical difference was found between group I and group II in terms of FEV1 measured at T2 time point (p < 0.05). Group I had higher FEV1 values measured at T3 and T4 time points compared to group III (p = 0.05, P<0.05; respectively). Group III had lower PEF values measured at T4 time point compared to group I and II (p < 0.05). Conclusions: We concluded that PEEP with 5 or 8 cmH2O has negative effects on lung function tests measured with spirometer during postoperative 1st, 6th, and 24th hours in patients underwent elective laparoscopic cholecystectomy.

Effect of lung protective ventilation strategies on improving postoperative pulmonary complications in patients with high risk factors

Background Pulmonary complications are major cause of postoperative mortality. Many factors aggravate pulmonary complications(PPC). Lung protective ventilation strategy prevents pulmonary complications to some extent. Objective To know if lung protective ventilation strategies can improve clinical outcomes of patients with high risk factors. Content To explain if lung protective ventilation strategies can improve clinical outcomes of patients with high risk factors like smoking, advanced age, pulmonary hypertension, chronic obstructive pulmonary disease(COPD), cardiac and neurologic diseases, and so on. Trend In patients with acute respiratory distress syndrome(ARDS), ventilation with low tidal volumes and high level of positive end expiratory pressure(PEEP) are recommended, and intraoperative ventilation should continue the settings applied on the ICU. In other critically ill patients, the evidence for the benefits of low tidal volume ventilation is growing. Low tidal volumes could cause excessive hypercapnia. High level of PEEP could cause dynamic hyperinflation, increased intracranial pressure and increased incidence of hemodynamic instability. We should not use lung protective ventilation strategies blindly. In patients with comorbidities, further research is necessary to find out whether lung protective ventilation should be adopted. Key words: Lung protective ventilation strategies; Postoperative pulmonary complications