PEEP role in ICU and operating room: from pathophysiology to clinical practice

Effects of positive end-expiratory pressure on brain oxygenation, systemic oxygen cascade and metabolism in acute brain injured patients: a pilot physiological cross-sectional study

Patients with acute brain injury (ABI) often require the application of positive end-expiratory pressure (PEEP) to optimize mechanical ventilation and systemic oxygenation. However, the effect of PEEP on cerebral function and metabolism is unclear. The primary aim of this study was to evaluate the effects of PEEP augmentation test (from 5 to 15 cmH2O) on brain oxygenation, systemic oxygen cascade and metabolism in ABI patients. Secondary aims include to determine whether changes in regional cerebral oxygenation are reflected by changes in oxygenation cascade and metabolism, and to assess the correlation between brain oxygenation and mechanical ventilation settings. Single center, pilot cross-sectional observational study in an Academic Hospital. Inclusion criteria were: adult (> 18 y/o) patients with ABI and stable intracranial pressure, available gas exchange and indirect calorimetry (IC) monitoring. Cerebral oxygenation was monitored with near-infrared spectroscopy (NIRS) and different derived parameters were collected: variation (Δ) in oxy (O2)-hemoglobin (Hb) (ΔO2Hbi), deoxy-Hb(ΔHHbi), total-Hb(ΔcHbi), and total regional oxygenation (ΔrSO2). Oxygen cascade and metabolism were monitored with arterial/venous blood gas analysis [arterial partial pressure of oxygen (PaO2), arterial saturation of oxygen (SaO2), oxygen delivery (DO2), and lactate], and IC [energy expenditure (REE), respiratory quotient (RQ), oxygen consumption (VO2), and carbon dioxide production (VCO2)]. Data were measured at PEEP 5 cmH2O and 15 cmH2O and expressed as delta (Δ) values. Ten patients with ABI [median age 70 (IQR 62-75) years, 6 (60%) were male, median Glasgow Coma Scale at ICU admission 5.5 (IQR 3-8)] were included. PEEP augmentation from 5 to 15 cmH2O did not affect cerebral oxygenation, systemic oxygen cascade parameters, and metabolism. The arterial component of cerebral oxygenation was significantly correlated with DO2 (ΔO2HBi, rho = 0.717, p = 0.037). ΔrSO2 (rho = 0.727, p = 0.032), ΔcHbi (rho = 0.797, p = 0.013), and ΔHHBi (rho = 0.816, p = 0.009) were significantly correlated with SaO2, but not ΔO2Hbi. ΔrSO2 was significantly correlated with VCO2 (rho = 0.681, p = 0.049). No correlation between brain oxygenation and ventilatory parameters was found. PEEP augmentation test did not affect cerebral and systemic oxygenation or metabolism. Changes in cerebral oxygenation significantly correlated with DO2, SaO2, and VCO2. Cerebral oxygen monitoring could be considered for individualization of mechanical ventilation setting in ABI patients without high or instable intracranial pressure.

Electric impedance tomography and protective mechanical ventilation in elective robotic-assisted laparoscopy surgery with steep Trendelenburg position: a randomized controlled study

Electrical impedance tomography (EIT) reconstructs functional lung images and evaluates the variations of impedance during the breathing cycle. The aim of this study was to evaluate the effect of protective mechanical ventilation on ventilation distributions recorded by the EIT during elective robotic-assisted laparoscopy surgery with steep Trendelenburg position. This prospective, randomized single center study included patients with healthy lungs undergoing elective robot-assisted laparoscopic urological surgery in general anesthesia. Patients were randomly assigned to either protective lung ventilation or conventional ventilation. In the protective ventilation group, tidal volume (TV) was set at 6 ml/Kg predicted body weight (PBW), with PEEP 6 cmH₂O, and recruitment maneuvers (RM) as needed. In the conventional ventilation group, TV was set at 9 ml/Kg PBW, with PEEP 2 cmH₂O and RM only as needed. Ventilation distribution was assessed using an EIT device. This study included 40 patients in the functional image analysis. Significant differences were found in ventilation distribution in the region of interest (p < 0.05). Driving pressure was significantly lower in protective ventilation group (p < 0.05). Peak and plateau pressures were not different between the groups while statical significance was found in tidal volume and respiratory rate. EIT may be a valuable tool for monitoring lung function during general anesthesia. During elective robotic-assisted laparoscopy surgery with steep Trendelenburg position, protective mechanical ventilation may have a more homogenous distribution of intraoperative and postoperative ventilation. Larger sample size and long-term evaluation are needed in future studies to assess the benefit of EIT monitoring in operation room.Clinical trial registration ClinicalTrials.gov Identifier: NCT04194177 registered at 11th December 2019.

Outcomes of and factors associated with the development of bronchopulmonary dysplasia with pulmonary hypertension in very low birth weight infants: A retrospective study in a medical center

Introduction

Bronchopulmonary dysplasia (BPD) with pulmonary hypertension (PH) leads to increased morbidity and mortality in extremely preterm infants. Recent studies have analyzed factors associated with development of PH in BPD; however, this research remains inconclusive, and controversy exists regarding the correlation between BPD and PH. This study aimed to investigate potential associated factors, clinical characteristics, and outcomes of BPD with pulmonary hypertension in very low birth weight (VLBW) preterm infants.

Methods

We conducted a retrospective study, reviewing the records of infants with gestational age (GA) <32 weeks and birth weight <1,500 g admitted to a tertiary neonatal intensive care unit between January 2020 and October 2021 who were diagnosed with moderate to severe BPD. Echocardiogram was performed at the postmenstrual age of 36 weeks or before discharge. The diagnosis of PH was based on the findings of echocardiogram. Prenatal and postnatal characteristics, demographic data, treatment details, and outcomes were collected and analyzed.

Results

A total of 139 VLBW infants with BPD were enrolled and divided into a PH group (n = 25) and a non-PH group (n = 114). The mean GA was 27.3 ± 2.3 weeks and the mean birth weight of infants with BPD was 927.3 ± 293.3 g. A multivariate logistic regression model revealed that a high positive end-expiratory pressure (PEEP) setting (OR: 2.105; 95% CI: 1.472-3.011; p < 0.001) in established BPD and surgical closure of patent ductus arteriosus (PDA; OR: 6.273; 95% CI: 1.574-24.977; p = 0.009) were associated with BPD-PH. Neonates with BPD who developed pulmonary hypertension remained hospitalized for longer (p < 0.001), received invasive mechanical ventilation support for longer (p < 0.001), had a higher incidence of retinopathy of prematurity (ROP; OR: 4.201; 95% CI: 1.561-11.304; p = 0.003), were more likely to require oxygen support at discharge (OR: 5.600; 95% CI: 2.175-14.416; p < 0.001), and were more likely to undergo tracheostomy (OR: 35.368; 95% CI: 4.03-310.43; p < 0.001).

Conclusion

PDA ligation and a higher PEEP setting were associated with BPD-PH in our cohort study. Compared with VLBW infants with BPD but without PH, infants with BPD and PH were hospitalized for longer, and also had a higher incidence of oxygen support after discharge, ROP, and tracheostomy.

High-Flow Nasal Oxygenation and Its Applicability in COVID Patients

High-flow nasal oxygenation (HFNO) is a type of oxygen therapy that provides humidified and heated oxygen through a nasal cannula at much higher flow rates than standard oxygen therapy, while also allowing control over the fraction of inspired oxygen (FIO₂). Compared to standard oxygen therapy, it is much more comfortable for the patient and seems to alleviate most of the problems associated with standard oxygen therapy, such as dry nose, dry throat and nasal pain. It also provides a variety of benefits that can reduce the incidence of escalating treatment and initiating mechanical ventilation in COVID patients with acute hypoxemic respiratory failure (AHRF). This article provides an overview of HFNO and its current applications in COVID patients during the pandemic.

The effects of chest drainage on pressure-controlled ventilation

BACKGROUND

The use of pressure-controlled ventilation (PCV) for anesthesia management is becoming more commonly used. Chest drainage is commonly performed after thoracic surgery, and the negative pressure it generates might affect the transpulmonary pressure (TPP). In the present study, we investigated how chest drainage could affect ventilating conditions during PCV.

METHODS

We created a hand-made simple thoracic and lung model, which was connected to an anesthesia machine. The tidal volume (TV) was measured with positive end-expiratory pressure (PEEP) 0 and no chest drainage (baseline), followed by 10 cmH₂O PEEP/no drainage, 10 cmH₂O PEEP/drainage with - 10 cmH₂O and 10 cmH₂O PEEP/drainage with - 20 cmH₂O. Finally, TV with 20 cmH₂O and 30 cmH₂O PEEP/no drainage was measured. Driving (inspiratory) pressure was maintained at 20 cmH₂O during the whole experiment.

RESULTS

TV was significantly increased by applying 10 cmH₂O PEEP compared with baseline, further increased by applying - 10 cmH₂O by drainage, similar to the value with PEEP 20 cmH₂O with no drainage (end-tidal TPP of 20 cmH₂O for both). TV decreased to < 50% of the baseline by applying 10 cmH₂O PEEP with - 20 cmH₂O by drainage, which was similar to that with 30 cmH₂O PEEP with no drainage (end-tidal TPP of 30 cmH₂O for both).

CONCLUSIONS

TV was maintained at similar levels with the same TPP, regardless of PEEP or negative pressure by chest drainage change, suggesting that negative intrapleural pressure by the chest tube drainage system might mimic PEEP from the point of TV.

Fragility Index and Fragility Quotient in Randomized Controlled Trials on Corticosteroids in ARDS Due to COVID-19 and Non-COVID-19 Etiology

Background: The effectiveness of corticosteroids in acute respiratory distress syndrome (ARDS) and COVID-19 still remains uncertain. Since ARDS is due to a hyperinflammatory response to a direct injury, we decided to perform a meta-analysis and an evaluation of robustness of randomised clinical trials (RCTs) investigating the impact of corticosteroids on mortality in ARDS in both COVID-19 and non-COVID-19 patients. We conducted a systematic search of the literature from inception up to 30 October 2020, using the MEDLINE database and the PubMed interface. We evaluated the fragility index (FI) of the included RCTs using a two-by-two contingency table and the p-value produced by the Fisher exact test; the fragility quotient (FQ) was calculated by dividing the FI score by the total sample size of the trial. Results: Thirteen RCTs were included in the analysis; five of them were conducted in COVID-19 ARDS, including 7692 patients, while 8 RCTS were performed in non-COVID ARDS with 1091 patients evaluated. Three out of eight RCTs in ARDS had a FI > 0 while 2 RCTs out of five in COVID-19 had FI > 0. The median of FI for ARDS was 0.625 (0.47) while the median of FQ was 0.03 (0.014). The median of FI for COVID-19 was 6 (2) while the median of FQ was 0.059 (0.055). In this systematic review, we found that FI and FQ of RCTs evaluating the use of corticosteroids in ARDS and COVID-19 were low.

Thoracic, Peripheral, and Cerebral Volume, Circulatory and Pressure Responses To PEEP During Simulated Hemorrhage in a Pig Model: a Case Study

Positive end-expiratory pressure (PEEP) is a respiratory/ventilation procedure that is used to maintain or improve breathing in clinical and experimental cases that exhibit impaired lung function. Body fluid shift movement is not monitored during PEEP application in intensive care units (ICU), which would be interesting specifically in hypotensive patients. Brain injured and hypotensive patients are known to have compromised cerebral blood flow (CBF) autoregulation (AR) but currently, there is no non-invasive way to assess the risk of implementing a hypotensive resuscitation strategy and PEEP use in these patients. The advantage of electrical bioimpedance measurement is that it is noninvasive, continuous, and convenient. Since it has good time resolution, it is ideal for monitoring in intensive care units (ICU). The basis of its future use is to establish physiological correlates. In this study, we demonstrate the use of electrical bioimpedance measurement during bleeding and the use of PEEP in pig measurement. In an anesthetized pig, we performed multimodal recording on the torso and head involving electrical bioimpedance spectroscopy (EIS), fixed frequency impedance plethysmography (IPG), and bipolar (rheoencephalography - REG) measurements and processed data offline. Challenges (n=16) were PEEP, bleeding, change of SAP, and CO2 inhalation. The total measurement time was 4.12 hours. Systemic circulatory results: Bleeding caused a continuous decrease of SAP, cardiac output (CO), and increase of heart rate, temperature, shock index (SI), vegetative - Kerdo index (KI). Pulse pressure (PP) decreased only after second bleeding which coincided with loss of CBF AR. Pulmonary arterial pressure (PAP) increased during PEEP challenges as a function of time and bleeding. EIS/IPG results: Body fluid shift change was characterized by EIS-related variables. Electrical Impedance Spectroscopy was used to quantify the intravascular, interstitial, and intracellular volume changes during the application of PEEP and simulated hemorrhage. The intravascular fluid compartment was the primary source of blood during hemorrhage. PEEP produced a large fluid shift out of the intravascular compartment during the first bleeding period and continued to lose more blood following the second and third bleeding. Fixed frequency IPG was used to quantify the circulatory responses of the calf during PEEP and simulated hemorrhage. PEEP reduced the arterial blood flow into the calf and venous outflow from the calf. Head results: CBF AR was evaluated as a function of SAP change. Before bleeding, and after moderate bleeding, intracranial pressure (ICP), REG, and carotid flow pulse amplitudes (CFa) increased. This change reflected vasodilatation and active CBF AR. After additional hemorrhaging during PEEP, SAP, ICP, REG, CFa signal amplitudes decreased, indicating passive CBF AR. 1) The indicators of active AR status by modalities was the following: REG (n=9, 56 %), CFa (n=7, 44 %), and ICP (n=6, 38 %); 2) CBF reactivity was better for REG than ICP; 3) REG and ICP correlation coefficient were high (R2 = 0.81) during CBF AR active status; 4) PRx and REGx reflected active CBF AR status. CBF AR monitoring with REG offers safety for patients by preventing decreased CBF and secondary brain injury. We used different types of bioimpedance instrumentation to identify physiologic responses in the different parts of the body (that have not been discussed before) and how the peripheral responses ultimately lead to decreased cardiac output and changes in the head. These bioimpedance methods can improve ICU monitoring, increase the adequacy of therapy, and decrease mortality and morbidity.

The safety and efficacy of prolonged use of one-way speaking valves

BACKGROUND

One-way speaking valves were first engineered to improve communication in patients with tracheostomies. More recently, additional indications for one-way speaking valves have been explored, including improving ventilation, weaning, and reducing aspiration; however, safety and adverse events have not been well defined.

OBJECTIVES

The aim of this study was to examine the cardiorespiratory changes that occur with prolonged use of a one-way speaking valve in relation to safety and efficacy.

METHODS

A prospective observational study of adult patients (n = 20) was carried out in a tertiary level intensive care unit. Continuous monitoring of cardiorespiratory parameters, including heart rate (beats per minutes), respiratory rate (breaths per minute), systolic, diastolic, and mean arterial pressure (mmHg), and oxygen saturations (%), was conducted for 2 h whilst participants used a one-way speaking valve. The participants then continued to use the one-way speaking valve as long as tolerated. Data are reported as median and range (non-normative data) or as mean ± standard deviation (normative data).

RESULTS

The time to tracheostomy was 17.5 (range = 7-54) days after the initiation of mechanical ventilation, and the time to first use of the one-way speaking valve was 11.4 days (standard deviation = 5.46) after tracheostomy. The participants tolerated using a one-way speaking valve (for more than 2 h) after a median of 2 (range = 1-8) days from first use. There were no significant changes to any cardiorespiratory parameters over the 2-h period and also no adverse events in this study whilst participants used one-way speaking valves for up to 17 (range = 5.5-17) hours.

CONCLUSIONS

The prolonged use of a one-way speaking valve is safe for patients who reached a threshold of 2 h.

The effect of positive end-expiratory pressure on cardiac output and oxygen delivery during cardiopulmonary resuscitation

Background

Positive end-expiratory pressure (PEEP) is used to optimize oxygenation by preventing alveolar collapse. However, PEEP can potentially decrease cardiac output through cardiopulmonary interactions. The effect of PEEP on cardiac output during cardiopulmonary resuscitation (CPR) is not known.

Methods

This was a preclinical randomized, controlled, animal study conducted in an animal research facility on 25 Landrace-Yorkshire pigs. After inducing cardiac arrest, CPR was performed with LUCAS 3. During CPR, pigs were ventilated at a PEEP of 0, 5, 10, 15, 20 cmH₂O (randomly determined via lottery) for 9 min. Cardiac output, obtained via ultrasound dilution, and PaO₂ were measured, and oxygen delivery calculated for each PEEP.

Results

A mixed-effects repeated-measures analysis of variance was used to compare the baseline value adjusted mean cardiac output, PaO₂, and oxygen delivery between PEEP groups. Least significant difference test was used to conduct pairwise comparisons between PEEP groups. To determine optimum PEEP, Gaussian mixture model was applied to the adjusted means of cardiac output and oxygen delivery. Increasing PEEP to 10 and higher resulted in significant declines in cardiac output. A PEEP of 15 and higher resulted in significant declines in oxygen delivery. As PEEP was increased from 0 to 20, PaO₂ increased significantly. Gaussian mixture model identified the 0–5 PEEP group as providing optimal cardiac output and oxygen delivery, with PEEP of 5 providing the highest oxygen delivery.

Conclusions

A PEEP of 0–5 resulted in the optimal oxygen delivery and cardiac output during CPR, with PEEP of 5 resulting in higher oxygen delivery, and a slightly lower, statistically insignificant cardiac output than PEEP of 0.

Body Habitus and Dynamic Surgical Conditions Independently Impair Pulmonary Mechanics during Robotic-assisted Laparoscopic Surgery

Background

Body habitus, pneumoperitoneum, and Trendelenburg positioning may each independently impair lung mechanics during robotic laparoscopic surgery. This study hypothesized that increasing body mass index is associated with more mechanical strain and alveolar collapse, and these impairments are exacerbated by pneumoperitoneum and Trendelenburg positioning.

Methods

This cross-sectional study measured respiratory flow, airway pressures, and esophageal pressures in 91 subjects with body mass index ranging from 18.3 to 60.6 kg/m2. Pulmonary mechanics were quantified at four stages: (1) supine and level after intubation, (2) with pneumoperitoneum, (3) in Trendelenburg docked with the surgical robot, and (4) level without pneumoperitoneum. Subjects were stratified into five body mass index categories (less than 25, 25 to 29.9, 30 to 34.9, 35 to 39.9, and 40 or higher), and respiratory mechanics were compared over surgical stages using generalized estimating equations. The optimal positive end-expiratory pressure settings needed to achieve positive end-expiratory transpulmonary pressures were calculated.

Results

At baseline, transpulmonary driving pressures increased in each body mass index category (1.9 ± 0.5 cm H2O; mean difference ± SD; P &lt; 0.006), and subjects with a body mass index of 40 or higher had decreased mean end-expiratory transpulmonary pressures compared with those with body mass index of less than 25 (–7.5 ± 6.3 vs. –1.3 ± 3.4 cm H2O; P &lt; 0.001). Pneumoperitoneum and Trendelenburg each further elevated transpulmonary driving pressures (2.8 ± 0.7 and 4.7 ± 1.0 cm H2O, respectively; P &lt; 0.001) and depressed end-expiratory transpulmonary pressures (–3.4 ± 1.3 and –4.5 ± 1.5 cm H2O, respectively; P &lt; 0.001) compared with baseline. Optimal positive end-expiratory pressure was greater than set positive end-expiratory pressure in 79% of subjects at baseline, 88% with pneumoperitoneum, 95% in Trendelenburg, and ranged from 0 to 36.6 cm H2O depending on body mass index and surgical stage.

Conclusions

Increasing body mass index induces significant alterations in lung mechanics during robotic laparoscopic surgery, but there is a wide range in the degree of impairment. Positive end-expiratory pressure settings may need individualization based on body mass index and surgical conditions.

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

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

High positive end expiratory pressure levels affect hemodynamics in elderly patients with hypertension admitted to the intensive care unit: a prospective cohort study

Background

To study the effects of different positive end expiratory pressure (PEEP) on blood pressure and heart function in elderly patients with hypertension.

Methods

Forty elderly patients above 65 years of age treated with mechanical ventilation were divided into two groups: a control group of non-hypertensive subjects (n = 18) and a hypertension group (n = 22) patients with essential hypertension. Changes in blood pressure, central venous pressure (CVP), central venous oxygen saturation (ScvO₂), heart rate, and airway pressure were determined in response to different selected PEEP levels of 0, 2, 4, 6, 8, 10 and 12 cm H₂O under SIMV(PC) + PSV mode throughout the study.

Results

In both groups, the increase in PEEP led to an increase in CVP and airway pressure. When PEEP was above 4 cm H₂O in the hypertension group, a decrease in blood pressure and ScvO₂, and an increase of heart rate were observed. These results indicated that cardiac output significantly decreased.

Conclusion

High levels of PEEP can significantly influence changes in blood pressure and heart function in elderly patients with hypertension.

Trial registration

This trial was retrospectively registered, The Chinese trial registration number is ChiCTR-ROC-17012873. The date of registration is 10-2-2017.

Variability in the Use of Protective Mechanical Ventilation During General Anesthesia

BACKGROUND

The purpose of this study was to determine whether significant variation exists in the use of protective ventilation across individual anesthesia providers and whether this difference can be explained by patient, procedure, and provider-related characteristics.

METHODS

The cohort consisted of 262 anesthesia providers treating 57,372 patients at a tertiary care hospital between 2007 and 2014. Protective ventilation was defined as a median positive end-expiratory pressure of 5 cm H2O or more, tidal volume of <10 mL/kg of predicted body weight and plateau pressure of <30 cm H2O. Analysis was performed using mixed-effects logistic regression models with propensity scores to adjust for covariates. The definition of protective ventilation was modified in sensitivity analyses.

RESULTS

In unadjusted analysis, the mean probability of administering protective ventilation was 53.8% (2.5th percentile of provider 19.9%, 97.5th percentile 80.8%). After adjustment for a large number of covariates, there was little change in the results with a mean probability of 51.1% (2.5th percentile 24.7%, 97.5th percentile 77.2%). The variations persisted when the thresholds for protective ventilation were changed.

CONCLUSIONS

There was significant variability across individual anesthesia providers in the use of intraoperative protective mechanical ventilation. Our data suggest that this variability is highly driven by individual preference, rather than patient, procedure, or provider-related characteristics.

Positive end-expiratory pressure improves elastic working pressure in anesthetized children

Background

Positive end-expiratory pressure (PEEP) has been demonstrated to decrease ventilator-induced lung injury in patients under mechanical ventilation (MV) for acute respiratory failure. Recently, some studies have proposed some beneficial effects of PEEP in ventilated patients without lung injury. The influence of PEEP on respiratory mechanics in children is not well known. Our aim was to determine the effects on respiratory mechanics of setting PEEP at 5 cmH₂O in anesthetized healthy children.

Methods

Patients younger than 15 years old without history of lung injury scheduled for elective surgery gave informed consent and were enrolled in the study. After usual care for general anesthesia, patients were placed on volume controlled MV. Two sets of respiratory mechanics studies were performed using inspiratory and expiratory breath hold, with PEEP 0 and 5 cmH₂O. The maximum inspiratory and expiratory flow (Q_I and Q_E) as well as peak inspiratory pressure (PIP), plateau pressure (P_PL) and total PEEP (tPEEP) were measured. Respiratory system compliance (C_RS), inspiratory and expiratory resistances (RawI and RawE) and time constants (K_TI and K_TE) were calculated. Data were expressed as median and interquartile range (IQR). Wilcoxon sign test and Spearman’s analysis were used. Significance was set at P < 0.05.

Results

We included 30 patients, median age 39 (15–61.3) months old, 60% male. When PEEP increased, PIP increased from 12 (11,14) to 15.5 (14,18), and C_RS increased from 0.9 (0.9,1.2) to 1.2 (0.9,1.4) mL·kg^− 1·cmH₂O^− 1; additionally, when PEEP increased, driving pressure decreased from 6.8 (5.9,8.1) to 5.8 (4.7,7.1) cmH₂O, and Q_E decreased from 13.8 (11.8,18.7) to 11.7 (9.1,13.5) L·min^− 1 (all P < 0.01). There were no significant changes in resistance and Q_I.

Conclusions

Analysis of respiratory mechanics in anesthetized healthy children shows that PEEP at 5 cmH₂O places the respiratory system in a better position in the P/V curve. A better understanding of lung mechanics may lead to changes in the traditional ventilatory approach, limiting injury associated with MV.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0611-8) contains supplementary material, which is available to authorized users.

Effects of intraoperative PEEP optimization on postoperative pulmonary complications and the inflammatory response: study protocol for a randomized controlled trial

Background

Patients undergoing general anesthesia and mechanical ventilation during major abdominal surgery commonly develop pulmonary atelectasis and/or hyperdistention of the lungs. Recent studies show benefits of lung-protective mechanical ventilation with the use of low tidal volumes, a moderate level of positive end-expiratory pressure (PEEP) and regular alveolar recruitment maneuvers during general anesthesia, even in patients with healthy lungs. The purpose of this clinical trial is to evaluate the effects of intraoperative lung-protective mechanical ventilation, using individualized PEEP values, on postoperative pulmonary complications and the inflammatory response.

Methods/design

A total number of 40 patients with bladder cancer undergoing open radical cystectomy and urinary diversion (ileal conduit or orthotopic bladder substitute) will be enrolled and randomized into a study (SG) and a control group (CG). Standard lung-protective ventilation with a PEEP of 6 cmH₂O will be applied in the CG and an optimal PEEP value determined during a static pulmonary compliance (Cstat)-directed PEEP titration procedure will be used in the SG. Low tidal volumes (6 mL/Kg ideal bodyweight) and a fraction of inspired oxygen of 0.5 will be applied in both groups. After surgery both groups will receive standard postoperative management. Primary endpoints are postoperative pulmonary complications and serum procalcitonin kinetics during and after surgery until the third postoperative day. Secondary and tertiary endpoints will be: organ dysfunction as monitored by the Sequential Organ Failure Assessment Score, in-hospital stay, 28-day and in-hospital mortality.

Discussion

This trial will assess the possible benefits or disadvantages of an individualized lung-protective mechanical ventilation strategy during open radical cystectomy and urinary diversion regarding postoperative pulmonary complications and the inflammatory response.

Trial registration

ClinicalTrials.gov, ID: NCT02931409. Registered on 5 October 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2116-z) contains supplementary material, which is available to authorized users.

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

Purpose/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 1^st, 6^th, and 24^th hours in patients underwent elective laparoscopic cholecystectomy.

Acute respiratory distress syndrome

Acute respiratory distress syndrome presents as hypoxia and bilateral pulmonary infiltrates on chest imaging in the absence of heart failure sufficient to account for this clinical state. Management is largely supportive, and is focused on protective mechanical ventilation and the avoidance of fluid overload. Patients with severe hypoxaemia can be managed with early short-term use of neuromuscular blockade, prone position ventilation, or extracorporeal membrane oxygenation. The use of inhaled nitric oxide is rarely indicated and both β₂ agonists and late corticosteroids should be avoided. Mortality remains at approximately 30%.

Percutaneous dilatational tracheostomy with a double-lumen endotracheal tube: a comparison of feasibility, gas exchange, and airway pressures

OBJECTIVE

Gas exchange and airway pressures are markedly altered during percutaneous dilatational tracheostomy (PDT). A double-lumen endotracheal tube (DLET) has been developed for better airway management during PDT. The current study prospectively evaluated the in vivo feasibility, gas exchange, and airway pressures during PDT with DLET compared with a conventional endotracheal tube (ETT).

METHODS

According to eligibility criteria, patients were divided into a case group (those receiving PDT with DLET) and a control group (those receiving PDT with a conventional ETT). The Ciaglia single-dilator technique was used for PDT in both groups. The primary end point of this study was the feasibility of tracheostomy with DLET. The secondary end points were a comparison of gas exchange, airway pressures, minute volume, and tidal volume before, during, and after PDT performed with DLET and conventional ETT.

RESULTS

Ten patients meeting the inclusion criteria were assigned to each group. PDTs were performed without difficulties in nine patients in the DLET group and 10 patients in the conventional ETT group. During PDT, gas exchange, airway pressures, and minute ventilation remained more stable in the DLET group and were significantly different from those in the conventional ETT group.

CONCLUSIONS

PDT with DLET can be performed safely without difficulties limiting the technique. Furthermore, during PDT, the use of the DLET resulted in more stable gas exchange, airway pressures, and ventilation than PDT with a conventional ETT.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01691222; URL: www.clinicaltrials.gov.