Association between mean airway pressure during high-frequency oscillatory ventilation and pulmonary air leak in extremely preterm infants during the first week of life.

Background: While positive pressure ventilation has been considered an important contributing factor associated with pulmonary air leaks, studies examining the association between specific ventilatory settings during acute-phase high-frequency oscillatory ventilation (HFOV) and pulmonary air leaks among extremely preterm infants are limited. Methods: This was a single-center retrospective cohort study conducted at an institution that primarily used HFOV after intubation in extremely preterm infants. We analyzed data from extremely preterm infants born between 2010 and 2021. The primary outcome was pulmonary air leakage during the first 7 days of life. The exposure variable was the maximum mean airway pressure (MAP) on HFOV during the first 7 days of life or before the onset of pulmonary air leaks. Maximum MAP was categorized into three groups: low (7-10 cmH2O), moderate (11-12 cmH2O), and high (13-15 cmH2O) MAP categories. We conducted robust Poisson regression analyses after adjustment for perinatal confounders, using the low MAP category as the reference. Results: The cohort included 171 infants (low MAP, 123; moderate MAP, 27; and high MAP, 21). The median (interquartile range) gestational age and birth weight were 25.7 (24.3-26.7), 25.7 (24.9-26.9), and 25.3 (24.3-26.6) weeks and 760 (612-878), 756 (648-962), and 734 (578-922) g for infants in the low, moderate, and high MAP categories, respectively. Compared to infants in the low MAP category, those in the high MAP category had a higher incidence of pulmonary air leaks (4.1% vs. 33.3%; adjusted risk ratio, 5.4; 95% confidence interval, 1.6-18.5). In contrast, there was no clear difference in the risk of pulmonary air leaks between the moderate and low MAP categories (3.7% vs. 4.1%; adjusted risk ratio, 0.9; 95% confidence interval, 0.1-6.1). Conclusion: Extremely preterm infants requiring high MAP (≥13 cmH2O) in acute-phase HFOV had a higher risk of pulmonary air leak during the first 7 days of life.

Use of Optical Redox Imaging to Quantify Alveolar Macrophage Redox State in Infants: Proof of Concept Experiments in a Murine Model and Human Tracheal Aspirates Samples.

Emerging data indicate that lung macrophages (LM) may provide a novel biomarker to classify disease endotypes in bronchopulmonary dysplasia (BPD), a form of infant chronic lung disease, and that augmentation of the LM phenotype may be a potential therapeutic target. To contribute to this area of research, we first used Optical Redox Imaging (ORI) to characterize the responses to H2O2-induced oxidative stress and caffeine treatment in an in vitro model of mouse alveolar macrophages (AM). H2O2 caused a dose-dependent decrease in NADH and an increase in FAD-containing flavoproteins (Fp) and the redox ratio Fp/(NADH + Fp). Caffeine treatment did not affect Fp but significantly decreased NADH with doses of ≥50 µM, and 1000 µM caffeine treatment significantly increased the redox ratio and decreased the baseline level of mitochondrial ROS (reactive oxygen species). However, regardless of whether AM were pretreated with caffeine or not, the mitochondrial ROS levels increased to similar levels after H2O2 challenge. We then investigated the feasibility of utilizing ORI to examine macrophage redox status in tracheal aspirate (TA) samples obtained from premature infants receiving invasive ventilation. We observed significant heterogeneity in NADH, Fp, Fp/(NADH + Fp), and mitochondrial ROS of the TA macrophages. We found a possible positive correlation between gestational age and NADH and a negative correlation between mean airway pressure and NADH that provides hypotheses for future testing. Our study demonstrates that ORI is a feasible technique to characterize macrophage redox state in infant TA samples and supports further use of this method to investigate lung macrophage-mediated disease endotypes in BPD.

Mean airway pressure as a parameter of lung-protective and heart-protective ventilation.

Mean airway pressure (MAP) is the mean pressure generated in the airway during a single breath (inspiration + expiration), and is displayed on most anaesthesia and intensive care ventilators. This parameter, however, is not usually monitored during mechanical ventilation because it is poorly understood and usually only used in research. One of the main determinants of MAP is PEEP. This is because in respiratory cycles with an I:E ratio of 1:2, expiration is twice as long as inspiration. Although MAP can be used as a surrogate for mean alveolar pressure, these parameters differ considerably in some situations. Recently, MAP has been shown to be a useful prognostic factor for respiratory morbidity and mortality in mechanically ventilated patients of various ages. Low MAP has been associated with a lower incidence of 90-day mortality, shorter ICU stay, and shorter mechanical ventilation time. MAP also affects haemodynamics: there is evidence of a causal relationship between high MAP and low perfusion index, both of which are associated with poor prognosis in mechanically ventilated patients. Elevated MAP values have also been associated with high central venous pressure and lactate, which are indicative of ventilator-associated right ventricular failure and tissue hypoperfusion, respectively. MAP, therefore, is an important parameter to measure in clinical practice. The aim of this review has been to identify the determinants of MAP, the pros and cons of using MAP instead of traditional protective ventilation parameters, and the evidence that supports the use of MAP in clinical practice.

Comparison of High-Frequency Oscillatory Ventilators.

BACKGROUND: The performance of high-frequency oscillatory ventilators (HFOV) differs by the waveform generation mode and circuit characteristics. Few studies have described the performance of piston-type HFOV. The present study aimed to compare the amplitude required to reach the target high-frequency tidal volume ([Formula: see text]); determine the relationship between the settings and actual pressure in amplitude or mean airway pressure ([Formula: see text]); and describe the interaction among compliance, frequency, and endotracheal tube (ETT) inner diameter in 4 HFOV models, including Humming X, Vue (a piston type ventilator commonly used in Japan), VN500 (a diaphragm type), and SLE5000 (a reverse jet type). METHODS: The oscillatory ventilators were evaluated by using a 50-mL test lung with 0.5 and 1.0 mL/cm H2O compliance, [Formula: see text] of 10 cm H2O, frequency of 12 and 15 Hz, and ETT inner diameters 2.0, 2.5, and 3.5 mm. At each permutation of compliance, frequency, and ETT, the target high-frequency [Formula: see text] was increased from 0.5 to 3.0 mL. The change in [Formula: see text] from the ventilator (ventilator [Formula: see text]) to Y-piece (Y [Formula: see text]) and alveolar pressure (alveolar [Formula: see text]) and the change in amplitude from the ventilator (ventilator amplitude) to Y-piece (Y amplitude) and alveolar pressure (alveolar amplitude) were determined at high-frequency [Formula: see text] of 1.0 and 3.0 mL. RESULTS: To achieve the target high-frequency [Formula: see text], the Humming X and Vue required a higher amplitude than did the SLE5000, but the maximum amplitude in the VN500 was unable to attain a larger high-frequency [Formula: see text]. Ventilator [Formula: see text] and alveolar pressure decreased at the Y-piece with the Humming X and Vue but increased with the SLE5000. The ventilator [Formula: see text] in the VN500 decreased remarkably at a frequency of 15 Hz. The ventilator amplitude in all 4 ventilators decreased while temporarily increasing at the Y-piece in the VN500. CONCLUSIONS: The actual measured value, such as alveolar [Formula: see text] and high-frequency [Formula: see text], varied according to the type of HFOV system and the inner diameter of the ETT, even with identical settings. Clinicians should therefore determine the setting appropriate to each HFOV model.

Correlations between APACHE-II score and pressure parameters of mechanical ventilation in patients with ARDS and their value in prognostic evaluation.

Objective: To investigate the correlations between APACHE-II score and pressure parameters of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) and their value in prognostic evaluation. Methods: This was a retrospective study. The clinical data of 79 patients with ARDS treated in Shengzhou Hospital of Traditional Chinese Medicine from April 2020 to April 2022 were analyzed retrospectively. According to whether their APACHE-II scores were higher than 15, they were divided into low score group (n= 20) and high score group (n= 59). The plateau pressure (Pplat), driving pressure(ΔP) and mean airway pressure (Pmean) were compared. The correlation between APACHE-II score and pressure parameters of mechanical ventilation was analyzed. Based on the follow-up of 28-d survival, their Pplat, ΔP, Pmean and APACHE-II scores were compared. The value of APACHE-II score and pressure parameters in the prognostic evaluation of ARDS patients was analyzed. Results: Pplat, ΔP and Pmean in the low score group were significantly lower than those in the high score group(P<0.05). Pplat, ΔP, Pmean and APACHE-II score in the survival group were significantly lower than those in the control group(P<0.05). APACHE-II score showed significantly positive correlations with Pplat, ΔP and Pmean. The AUC of Pmean, Pplat, ΔP and APACHE-II score in predicting the prognosis and diagnosis of ARDS patients was 0.761, 0.833, 0.754 and 0.832, respectively. Conclusion: APACHE-II score of ARDS patients shows significantly positive correlations with pressure parameters of mechanical ventilation, and has diagnostic value for the prognosis of ARDS patients.

Erroneous presentation of respiratory-hemodynamic disturbances and postsurgical inflammatory responses in patients having undergone abdominal cavity cancer surgery.

In this letter to the editor, the authors discuss the findings and shortcomings of a published retrospective study, including 120 patients undergoing surgery for gastric or colon cancer under general anesthesia. The study focused on perioperative dynamic respiratory and hemodynamic disturbances and early postsurgical inflammatory responses.

Cardiopulmonary resuscitation of a very preterm infant using high-frequency oscillation ventilation.

We present a novel approach of ventilation, using high-frequency oscillation ventilation (HFOV), during neonatal cardiopulmonary resuscitation (CPR) of a very preterm neonate. This case report highlights the importance of adequate lung inflation, which is a current topic, with neonatal resuscitation guidelines recommending a coordinated 3:1 compression:ventilation ratio during CPR. Our patient, a female infant born at 30 weeks gestational age, weighing 970 g, appeared floppy and apneic following birth in the amniotic sac. Lungs were unfolded and white-out in an x-ray done during resuscitation. The aim was to open lungs effectively using HFOV, instead of positive pressure ventilation, which was used unsuccessfully until the 7th minute of life. Heart rate continuously dropped below 60/min 15 min after birth and chest compressions with asynchronous HFOV were started, adrenalin was administered three times and surfactant was instilled endotracheally twice. It was possible to stabilize the patient after 15 min of CPR, following return of spontaneous circulation. HFOV may have enabled an alternative and rescue option of ventilation during neonatal CPR in this case.

Aplicaciones e implicaciones de la pausa al final de la inspiración en ventilación mecánica / Applications and implications of end-inspiratory pause in mechanical ventilation / Aplicações e implicações da pausa ao final da inspiração na ventilação mecânica

Resumen: El uso de la pausa al final de la inspiración (PFI) en ventilación mecánica data de hace más de 50 años y con mayor impulso en la década de los 70, se le atribuye una mejoría en la presión parcial de oxígeno arterial (PaO2) al incrementar la presión media de la vía aérea (Pma), mayor aclaramiento de la presión parcial de dióxido de carbono arterial (PaCO2) y permite la monitorización de la presión meseta (Pmeseta) en la mecánica ventilatoria; sin embargo, los estudios clínicos sobre su uso son escasos y controversiales. En este artículo se abordan los mecanismos fisiológicos, fisiopatológicos y la evidencia sobre el uso de la PFI en ventilación mecánica (VM).

Abstract: The use of the end inspiratory pause (EIP) in mechanical ventilation has been going on for more than 50 years and with greater momentum in the 1970s, an improvement in the partial pressure of arterial oxygen (PaO2) is attributed to the increase mean airway pressure, greater clearance of partial pressure of arterial carbon dioxide and allows monitoring of plateau pressure in ventilatory mechanics; However, the Clinical studies on its use are few and controversial. This article addresses the physiological and pathophysiological mechanisms and the evidence on the use of EIP in mechanical ventilation.

Resumo: A utilização da pausa ao final da inspiração (PFI) na ventilação mecânica remonta a mais de 50 anos e com maior impulso na década de 70, atribui-se uma melhora na pressão parcial de oxigênio arterial (PaO2) pelo aumento da pressão média das vias aéreas (Pma), uma maior depuração da pressão parcial de dióxido de carbono arterial (PaCO2) e permite a monitorização da pressão de platô (Pplateau) na mecânica ventilatória, porém estudos Os dados clínicos sobre seu uso são escassos e controversos. Este artigo aborda os mecanismos fisiológicos e fisiopatológicos e as evidências sobre o uso do PFI na ventilação mecânica (VM).

Acute neurological injury in pediatric patients with single-ventricle congenital heart disease.

OBJECTIVE: Single-ventricle congenital heart disease (CHD) in pediatric patients with Glenn and Fontan physiology represents a unique physiology requiring the surgical diversion of the systemic venous return from the superior vena cava (Glenn) and then the inferior vena cava (Fontan) directly to the pulmonary arteries. Because many of these patients are on chronic anticoagulation therapy and may have right-to-left shunts, arrhythmias, or lymphatic disorders that predispose them to bleeding and/or clotting, they are at risk of experiencing neurological injury requiring intubation and positive pressure ventilation, which can significantly hamper pulmonary blood flow and cardiac output. The aim of this study was to describe the complex neurological and cardiopulmonary interactions of these pediatric patients after acute central nervous system (CNS) injury. METHODS: The authors retrospectively analyzed the records of pediatric patients who had been admitted to a quaternary children's hospital with CHD palliated to bidirectional Glenn (BDG) or Fontan circulation and acute CNS injury and who had undergone intubation and mechanical ventilation. Patients who had been admitted from 2005 to 2019 were included in the study. Clinical characteristics, surgical outcomes, cardiovascular and pulmonary data, and intracranial pressure data were collected and analyzed. RESULTS: Nine pediatric single-ventricle patients met the study inclusion criteria. All had undergone the BDG procedure, and the majority (78%) were status post Fontan palliation. The mean age was 7.4 years (range 1.3-17.3 years). At the time of acute CNS injury, which included traumatic brain injury, intracranial hemorrhage, and cerebral infarct, the median time interval from the most recent cardiac surgical procedure was 3 years (range 2 weeks-11 years). Maintaining normocarbia to mild hypercarbia for most patients during intubation periods did not cause neurological deterioration, and hemodynamic profiles were more favorable as compared to periods of hypocarbia. Hypocarbia was associated with unfavorable hemodynamics but was necessary to decrease intracranial hypertension. Most patients were managed using low mean airway pressure (MAWP) in order to minimize the impact on preload and cardiac output. CONCLUSIONS: The authors highlight the complex neurological and cardiopulmonary interactions with respect to partial pressure of arterial CO2 (PaCO2) and MAWP when pediatric CHD patients with single-ventricle physiology require mechanical ventilation. The study data demonstrated that tight control of PaCO2 and minimizing MAWP with the goal of early extubation may be beneficial in this population. A multidisciplinary team of pediatric critical care intensivists, cardiac intensivists and anesthesiologists, and pediatric neurosurgeons and neurologists are recommended to ensure the best possible outcomes.

A simple method of mechanical power calculation: using mean airway pressure to replace plateau pressure.

The reference method for mechanical power (MP) calculation proposed by Gattinoni et al. is based on plateau pressure (Pplat) which needs an inspiratory hold. This study aims to introduce and validate a simple surrogate for MP calculation without any intervention in ventilated patients with or without acute respiratory distress syndrome (ARDS). The introduced equation is as:[Formula: see text]where Pmean is mean airway pressure, VE is minute ventilation, PEEP is positive end-expiratory pressure, and Te/Ti is expiratory-to-inspiratory ratio. 50 patients with ARDS and 50 post-operative patients without ARDS were enrolled. Pmean-derived MP and reference MP were obtained at the inspiratory plateau time (Tplat) of 0 and 0.5 s (s). When Tplat was adjusted from 0 to 0.5 s, higher Pmean [non-ARDS cases: 9.3 (8.8-9.9) cmH2O versus 8.2 (7.9-8.8) cmH2O, P < 0.001; ARDS cases: 14 (13-16) cmH2O versus 13 (11-14) cmH2O, P < 0.001] and shorter Te/Ti [non-ARDS cases: 1.4 (1.2-1.7) versus 2.4 (2.0-3.0), P < 0.001; ARDS cases: 1.3 (1.2-1.5) versus 2.5 (2.3-2.9), P < 0.001] were found. At both Tplat levels, the Pmean-derived MP correlated well with the reference MP both in patients with or without ARDS (non-ARDS: slopes = 1.05, 0.94, R2 = 0.95, 0.93, bias + 0.76, + 0.51; ARDS: slopes = 1.03, 0.95, R2 = 0.96, 0.96, bias + 0.97, + 0.78. P < 0.0001 for all). In patients with or without ARDS, Pmean-derived MP allows rapid and dynamic estimation of mechanical power without any intervention at the bedside.

Mean airway pressure has the potential to become the core pressure indicator of mechanical ventilation: Raising to the front from behind the clinical scenes.

Mean airway pressure (Pmean) is a common pressure monitoring parameter of mechanical ventilators that is closely correlated with mean alveolar pressure and represents stresses applied to the lung parenchyma during ventilation. Pmean is determined by the peak inspiratory pressure, positive end-expiratory pressure (PEEP), and inspiratory-to-expiratory time ratio with dynamic and real-time characteristics, which represents mechanical power affected by the ventilator mode. Additionally, Pmean is an important parameter that affects hemodynamics. Tidal forces and PEEP increase pulmonary vascular resistance (PVR) in direct proportion to their effects on Pmean. Therefore, Pmean is increasingly considered to be related to the prognosis of patients on mechanical ventilation. We propose a 3P strategy (Pmean, central venous pressure [CVP], and perfusion index [PI]) which is indicated to achieve circulation protection mechanical ventilation with flow priority. Titrating the appropriate CVP and meeting PI to ensure tissue perfusion with a lower Pmean are the core purposes. Pmean links the circulatory and respiratory systems and is expected to become a potential parameter for intelligent ventilation.

Comparison of the Oxygenation Factor and the Oxygenation Ratio in Subjects With ARDS.

BACKGROUND: The oxygenation ratio (ie, [Formula: see text]/[Formula: see text]) remains the most commonly used index for assessing oxygenation and disease severity in patients with acute ARDS. However, the oxygenation ratio does not account for mechanical ventilation settings. We hypothesized that the oxygenation factor (ie, oxygenation ratio/mean airway pressure) is superior to the oxygenation ratio in reflecting oxygenation in patients with ARDS and results in a different classification of ARDS severity. METHODS: In 150 subjects with ARDS (50 severe, 50 moderate, and 50 mild), arterial blood gas, mean airway pressure, static lung compliance, driving pressure, and mechanical power were obtained. The oxygenation ratio and the oxygenation factor were then calculated. Receiver operating characteristic curves were constructed for oxygenation ratio and oxygenation factor at lung compliance > 40 mL/cm H2O, driving pressure < 15 cm H2O, and mechanical power < 17 J/min, thresholds that are known to predict survival in patients with ARDS. Subjects were reclassified for ARDS severity on the basis of the oxygenation factor and compared to classification on the basis of the oxygenation ratio. RESULTS: Areas under the receiver operating characteristic curves for the oxygenation factor were significantly higher than for the oxygenation ratio. Reclassification of ARDS severity using the oxygenation factor did not affect subjects classified as having severe ARDS per the oxygenation ratio. However, 52% of subjects with moderate ARDS per the oxygenation ratio criteria were reclassified as either severe (25 subjects) or mild ARDS (1 subject) on the basis of oxygenation factor criteria. Also, 54% of subjects with mild ARDS per the oxygenation ratio criteria were reclassified as severe (4 subjects), moderate (21 subjects), or non-ARDS (2 subjects) on the basis of oxygenation factor criteria. CONCLUSIONS: The oxygenation factor was a superior ARDS oxygenation index compared to the oxygenation ratio and should be considered as a substitute criteria for classification of the severity of ARDS. (ClinicalTrials.gov registration NCT03946189.).

Optimal mean airway pressure during high-frequency oscillatory ventilation in an experimental model of acute respiratory distress syndrome: EIT-based method.

BACKGROUND: High-frequency oscillatory ventilation (HFOV) may theoretically provide lung protective ventilation. The negative clinical results may be due to inadequate mean airway pressure (mPaw) settings in HFOV. Our objective was to evaluate the air distribution, ventilatory and hemodynamic effects of individual mPaw titration during HFOV in ARDS animal based on oxygenation and electrical impedance tomography (EIT). METHODS: ARDS was introduced with repeated bronchoalveolar lavage followed by injurious mechanical ventilation in ten healthy male pigs (51.2 ± 1.9 kg). Settings of HFOV were 9 Hz (respiratory frequency), 33% (inspiratory time) and 70 cmH2O (∆pressure). After lung recruitment, the mPaw was reduced in steps of 3 cmH2O every 6 min. Hemodynamics and blood gases were obtained in each step. Regional ventilation distribution was determined with EIT. RESULTS: PaO2/FiO2 decreased significantly during the mPaw decremental phase (p < 0.001). Lung overdistended regions decreased, while recruitable regions increased as mPaw decreased. The optimal mPaw with respect to PaO2/FiO2 was 21 (18.0-21.0) cmH2O, that is comparable to EIT-based center of ventilation (EIT-CoV) and EIT-collapse/over, 19.5 (15.0-21.0) and 19.5 (18.0-21.8), respectively (p = 0.07). EIT-CoV decreasing along with mPaw decrease revealed redistribution toward non-dependent regions. The individual mPaw titrated by EIT-based indices improved regional ventilation distribution with respect to overdistension and collapse (p = 0.035). CONCLUSION: Our data suggested personalized optimal mPaw titration by EIT-based indices improves regional ventilation distribution and lung homogeneity during high-frequency oscillatory ventilation.

Investigation of mechanical ventilation pressure parameters' effect on the prognosis of acute respiratory distress syndrome / 中华急诊医学杂志

Objective To find out whether we can get the optimality in the prognosis of acute respiratory distress syndrome (ARDS) by combing the pressure parameters in mechanical ventilation with traditional PaO2/FiO2.Methods This is a retrospective study.Patients included here were diagnosed as ARDS in the Emergency Unit (EICU) of the First Affiliated Hospital of China Medical University fiom January 2018 to December 2018.All the patients were intubated and mechanically ventilated.Patients with a short observation time (＜ 48 h) or unable to cooperate with treatment were excluded.According to the patient's 28-day survival,patients were divided into the survival and non-survival groups.Parameters in the two groups such as basic characteristics,SOFA score,non-respiratory system SOFA score (nR-SOFA),and PaO2/FiO2 were analyzed with LSD-t test or rank sum test.Simultaneously,plateau pressure,driving pressure,mean airway pressure and the ratio of these mechanical ventilation pressure parameters to the PaO2/FiO2 were also analyzed.Results A total of 147 patients were included in the study and 117 of them were analyzed.The overall 28-day mortality was 31.62％ (n=37).There were no significant differences in gender,age,body mass index,initial arterial oxygen partial pressure and carbon dioxide partial pressure between the survival group and non-survival groups (P ＞0.05).But there was a significant difference in SOFA score(6.53 ± 2.96 vs 8.65 ± 3.00) and nR-SOFA(3.44 ± 2.98 vs 5.27 ± 2.86).Among the evaluation indexes,the PPOI obtained the AUC of 0.828,with the sensitivity of 86.5％,and specificity of 71.2％.The AUC of the SOFA score was 0.707,while the AUC of the PPOI combined with the SOFA score was 0.833.Conclusion Mechanical ventilation pressure parameters can be used to predict the prognosis of patients with ARDS.PPOI may evaluate the prognosis of ARDS in a more simple,timely and real-time manner.

The value of combined hemodynamic, respiratory and intra-abdominal pressure monitoring in predicting acute kidney injury after major intraabdominal surgeries.

BACKGROUND: The incidence of postoperative acute kidney injury (AKI) is predominantly determined by renal hemodynamics. Beside arterial blood pressure, the role of factors causing a deterioration of venous congestion (intraabdominal pressure, central venous pressure, mechanical ventilation) has emerged. The value of combined hemodynamic, respiratory and intra-abdominal pressure (IAP) monitoring in predicting postoperative acute kidney injury has received only limited exploration to date. METHODS: Data were collected for adult patients admitted after major abdominal surgery at nine Hungarian ICUs. Hemodynamic parameters were compared in AKI vs. no-AKI patients at the time of admission and 48 h thereafter. Regarding ventilatory support, we tested mean airway pressures (Pmean). Effective renal perfusion pressure (RPP) was calculated as MAP-(IAP + CVP + Pmean). The Mann-Whitney U and the chi-square tests were carried out for statistical analysis with forward stepwise logistic regression for AKI as a dependent outcome. RESULTS: A total of 84 patients (34 ventilated) were enrolled in our multicenter observational study. The median values of MAP were above 70 mmHg, IAP not higher than 12 mmHg and CVP not higher than 8 mmHg at all time-points. When we combined those parameters, even those belonging to the 'normal' range with Pmean, we found significant differences between no-AKI and AKI groups only at 12 h after ICU admission (median and IQR: 57 (42-64) vs. 40 (36-52); p < .05). Below it's median (40.7 mmHg) on admission, AKI developed in all patients. If above 40.7 mmHg on admission, they were protected against AKI, but only if it did not decrease within the first 12 h. CONCLUSIONS: Calculated effective RPP with the novel formula MAP-(IAP + CVP + Pmean) may predict the onset of AKI in the surgical ICU with a great sensitivity and specificity. Maintaining effective RPP appears important not only at ICU admission but during the next 12 h, as well. Additional, larger studies are needed to explore therapeutic interventions targeting this parameter.

Extubation from high-frequency oscillatory ventilation in extremely low birth weight infants: a prospective observational study.

OBJECTIVE: To evaluate if weaning from high-frequency oscillatory ventilation (HFOV) directly to a non-invasive mode of respiratory support is feasible and results in successful extubation in extremely low birth weight (ELBW) infants. DESIGN: Prospective observational study. SETTING: Tertiary neonatal intensive care unit. PATIENTS: One hundred and eight ELBW infants of 26.2±1.4 weeks of gestational age (GA) directly extubated from HFOV. INTERVENTIONS: All infants were managed with elective HFOV and received surfactant after a recruitment HFOV manoeuvre. Extubation was attempted at mean airways pressure (MAP) ≤6 cm H2O with FiO2 ≤0.25. After extubation, all infants were supported by nasal continuous positive airway pressure (6-8 cm H2O). MAIN OUTCOME MEASURES: Extubation failure (clinical deterioration requiring reintubation) was defined as shorter than 7 days. RESULTS: Ninety patients (83%) were successfully extubated and 18 (17%) required reintubation. No significant differences were found between the two groups in terms of birth weight, day of life and weight at the time of extubation. Multivariable analysis showed that GA (OR 1.71; 95% CI 1.04, 2.08) and higher MAP prior to surfactant (OR 1.51; 95% CI 1.06, 2.15) were associated with successful extubation. CONCLUSIONS: In ELBW infants, direct extubation from HFOV at MAP ≤6 cm H2O with FiO2 ≤0.25 is feasible. Our extubation success rate (83%) is higher than conventional mechanical ventilation in this very vulnerable class of infants.

Renoprotective Postoperative Monitoring: What Is the Best Method for Computing Renal Perfusion Pressure? An Observational, Prospective, Multicentre Study.

BACKGROUND: Low mean arterial pressure (MAP) is a well-known risk factor for postoperative acute kidney injury (AKI), but probably it is not the sole hemodynamic parameter that can influence the development of renal failure. There are data in cardiac patients supporting the role of renal venous congestion in the development of AKI. The aim of our study was to determine a combination of factors best predicting the development of AKI. METHODS: Data were collected prospectively for adult patients admitted after major abdominal surgery to 9 Hungarian intensive care units. Hemodynamic and laboratory parameters were compared in patients with AKI vs. no-AKI at the time of admission. Renal perfusion was computed by different methods from hemodynamic measurements involving MAP, central venous pressure (CVP), intraabdominal pressure (IAP), and mean airway pressures (Pmean). Twelve different, clinically interpretable equations were tested. Statistical evaluation was performed by the Mann-Whitney U test and ROC analysis. RESULTS: Eighty-four patients were enrolled in the study. Renal perfusion pressure was significantly lower in all equations. The equations MAP-IAP-Pmean (1-area under the curve [AUC]: 0.796; likelihood ratio [LR]+: 3.520; LR-: 0.337; p < 0.01), MAP-IAP-CVP-Pmean (1-AUC: 0.794; LR+: 2.743; LR-: 0.282; p < 0.01), and MAP-2 × IAP-CVP-Pmean (1-AUC: 0.791; LR+: 4.321; LR-: 0.262; p < 0.001) showed small to moderate effect on AKI but have better performance than severity score systems (SAPS II [AUC: 0.696; LR+: 3.143, LR-: 0.433; p < 0.01], SOFA [AUC: 0.717; LR+: 2.089; LR-: 0.528; p < 0.001]). CONCLUSION: We found that the best parameter predicting AKI is the MAP-2 × IAP-CVP-Pmean. Further investigation is needed to analyze the role of CVP and Pmean, and to characterize renal venous congestion and tubular pressure more in detail.

Quantifying the Amount of Bleeding and Associated Changes in Intra-Abdominal Pressure and Mean Airway Pressure in Patients Undergoing Lumbar Fixation Surgeries: A Comparison of Three Positioning Systems.

STUDY DESIGN: Prospective, randomised controlled, single centre study of 45 patients posted for two level lumbar fixation surgery in the prone position. PURPOSE: To compare intra-abdominal pressure (IAP), mean airway pressure mean airway pressure and blood loss during the spine surgery in prone position using three different positioning systems. OVERVIEW OF LITERATURE: Studies have correlated IAP with the amount of perioperative bleeding. However, IAP and airway pressures while assessing the bleeding comparing two or more prone positioning systems are unclear. METHODS: This prospective study was conducted on a cohort of 45 patients scheduled for two-level lumbar fixation. Patients were randomly allocated to a spine table, Wilson's frame, and thermomodulated pads. Bladder pressure as an indicator of IAP, mean and peak airway pressures, and blood loss were monitored. RESULTS: IAP increased whenever patient position was changed to prone .The increase in pressure was more in the Wilson's frame group but was statistically significant only on prolonged positioning. Adopting the prone position always increased the mean airway pressure, but the increased was significant only in the Wilson's frame group. Mean airway pressure decreased in the spine table group and was statistically significant. The blood loss in the spine table group was significantly less as compared to the other groups. CONCLUSIONS: Positioning on a spine table results in less blood loss and low mean airway pressure. The Wilson's frame results in high IAP, increased mean airway pressure, and more blood loss. The thermomodulated frame increases mean airway pressure and produces a moderate increase in IAP and airway pressure.

Factors influencing delivered mean airway pressure during nasal CPAP with the RAM cannula.

OBJECTIVE: To measure mean airway pressure (MAP) delivered through the RAM Cannula® when used with a ventilator in CPAP mode as a function of percent nares occlusion in a simulated nasal interface/test lung model and to compare the results to MAPs using a nasal continuous positive airway pressure (NCPAP) interface with nares fully occluded. STUDY DESIGN: An artificial airway model was connected to a spontaneous breathing lung model in which MAP was measured at set NCPAP levels between 4 and 8 cmH2 O provided by a Dräger Evita XL® ventilator and delivered through three sizes of RAM cannulae. Measurements were performed with varying leakage at the nasal interface by decreasing occlusion from 100% to 29%, half-way prong insertion, and simulated mouth leakage. Comparison measurements were made using the Dräger BabyFlow® NCPAP interface with a full nasal seal. RESULTS: With simulated mouth closed, the Dräger interface delivered MAPs within 0.5 cmH2 O of set CPAP levels. For the RAM cannula, with 60-80% nares occlusion, overall delivered MAPs were 60 ± 17% less than set CPAP levels (P < 0.001). Further, MAP decreased progressively with decreasing percent nares occlusion. The simulated open mouth condition resulted in significantly lower MAPs to <1.7 cmH2 O. The one-half prong insertion depth condition, with closed mouth, yielded MAPs approximately 35 ± 9% less than full insertion pressures (P < 0.001). CONCLUSIONS: In our bench tests, the RAM interface connected to a ventilator in NCPAP mode failed to deliver set CPAP levels when applied using the manufacturer recommended 60-80% nares occlusion, even with closed mouth and full nasal prong insertion conditions.

Quantifying the Amount of Bleeding and Associated Changes in Intra-Abdominal Pressure and Mean Airway Pressure in Patients Undergoing Lumbar Fixation Surgeries: A Comparison of Three Positioning Systems

STUDY DESIGN: Prospective, randomised controlled, single centre study of 45 patients posted for two level lumbar fixation surgery in the prone position. PURPOSE: To compare intra-abdominal pressure (IAP), mean airway pressure mean airway pressure and blood loss during the spine surgery in prone position using three different positioning systems. OVERVIEW OF LITERATURE: Studies have correlated IAP with the amount of perioperative bleeding. However, IAP and airway pressures while assessing the bleeding comparing two or more prone positioning systems are unclear. METHODS: This prospective study was conducted on a cohort of 45 patients scheduled for two-level lumbar fixation. Patients were randomly allocated to a spine table, Wilson's frame, and thermomodulated pads. Bladder pressure as an indicator of IAP, mean and peak airway pressures, and blood loss were monitored. RESULTS: IAP increased whenever patient position was changed to prone .The increase in pressure was more in the Wilson's frame group but was statistically significant only on prolonged positioning. Adopting the prone position always increased the mean airway pressure, but the increased was significant only in the Wilson's frame group. Mean airway pressure decreased in the spine table group and was statistically significant. The blood loss in the spine table group was significantly less as compared to the other groups. CONCLUSIONS: Positioning on a spine table results in less blood loss and low mean airway pressure. The Wilson's frame results in high IAP, increased mean airway pressure, and more blood loss. The thermomodulated frame increases mean airway pressure and produces a moderate increase in IAP and airway pressure.