Transpulmonary Pressure Research Articles

Early spontaneous breathing for acute respiratory distress syndrome in individuals with COVID-19.

Acute respiratory distress syndrome (ARDS) represents the most severe course of COVID-19 (caused by the SARS-CoV-2 virus), usually resulting in a prolonged stay in an intensive care unit (ICU) and high mortality rates. Despite the fact that most affected individuals need invasive mechanical ventilation (IMV), evidence on specific ventilation strategies for ARDS caused by COVID-19 is scarce. Spontaneous breathing during IMV is part of a therapeutic concept comprising light levels of sedation and the avoidance of neuromuscular blocking agents (NMBA). This approach is potentially associated with both advantages (e.g. a preserved diaphragmatic motility and an optimised ventilation-perfusion ratio of the ventilated lung), as well as risks (e.g. a higher rate of ventilator-induced lung injury or a worsening of pulmonary oedema due to increases in transpulmonary pressure). As a consequence, spontaneous breathing in people with COVID-19-ARDS who are receiving IMV is subject to an ongoing debate amongst intensivists. To assess the benefits and harms of early spontaneous breathing activity in invasively ventilated people with COVID-19 with ARDS compared to ventilation strategies that avoid spontaneous breathing. We searched the Cochrane COVID-19 Study Register (which includes CENTRAL, PubMed, Embase, Clinical Trials.gov WHO ICTRP, and medRxiv) and the WHO COVID-19 Global literature on coronavirus disease to identify completed and ongoing studies from their inception to 2 March 2022. Eligible study designs comprised randomised controlled trials (RCTs) that evaluated spontaneous breathing in participants with COVID-19-related ARDS compared to ventilation strategies that avoided spontaneous breathing (e.g. using NMBA or deep sedation levels). Additionally, we considered controlled before-after studies, interrupted time series with comparison group, prospective cohort studies and retrospective cohort studies. For these non-RCT studies, we considered a minimum total number of 50 participants to be compared as necessary for inclusion. Prioritised outcomes were all-cause mortality, clinical improvement or worsening, quality of life, rate of (serious) adverse events and rate of pneumothorax. Additional outcomes were need for tracheostomy, duration of ICU length of stay and duration of hospitalisation. We followed the methods outlined in the Cochrane Handbook for Systematic Reviews of Interventions. Two review authors independently screened all studies at the title/abstract and full-text screening stage. We also planned to conduct data extraction and risk of bias assessment in duplicate. We planned to conduct meta-analysis for each prioritised outcome, as well as subgroup analyses of mortality regarding severity of oxygenation impairment and duration of ARDS. In addition, we planned to perform sensitivity analyses for studies at high risk of bias, studies using NMBA in addition to deep sedation level to avoid spontaneous breathing and a comparison of preprints versus peer-reviewed articles. We planned to assess the certainty of evidence using the GRADE approach. We identified no eligible studies for this review. We found no direct evidence on whether early spontaneous breathing in SARS-CoV-2-induced ARDS is beneficial or detrimental to this particular group of patients. RCTs comparing early spontaneous breathing with ventilatory strategies not allowing for spontaneous breathing in SARS-CoV-2-induced ARDS are necessary to determine its value within the treatment of severely ill people with COVID-19. Additionally, studies should aim to clarify whether treatment effects differ between people with SARS-CoV-2-induced ARDS and people with non-SARS-CoV-2-induced ARDS.

Identifying asynchronies: Reverse trigger

A variety of asynchronies between the patient’s respiratory efforts and the programed ventilatory settings have been categorized. Reverse trigger is described as an inspiratory effort occurring after a ventilator-initiated breath and may represent a form of respiratory entrainment. In other words, the ventilator triggers muscular efforts. It often appears in a repetitive, stereotyped pattern. It occurs often in mechanically ventilated patients at risk of injury, might be underrecognized at the bedside and may has adverse effects on oxygenation and ventilation, as well as potentially increasing lung injury. We can phenotype these events using the Campbell diagram (pressure–volume loop) by differentiating their occurrence during inspiration and expiration. Reverse trigger with sufficient inspiratory effort and duration can result in an additional ventilator-delivered stacked breath, which can cause large tidal volumes and increased transpulmonary pressure. Keywords: Asynchrony, ventilator, reverse trigger, entrainment, lung injury, phenotype.

Partition of respiratory mechanics in patients with acute respiratory distress syndrome and association with outcome: a multicentre clinical study.

PurposeIn acute respiratory distress syndrome (ARDS), physiological parameters associated with outcome may help defining targets for mechanical ventilation. This study aimed to address whether transpulmonary pressures (PL), including transpulmonary driving pressure (DPL), elastance-derived plateau PL, and directly-measured end-expiratory PL, are better associated with 60-day outcome than airway driving pressure (DPaw). We also tested the combination of oxygenation and stretch index [PaO2/(FiO2*DPaw)].MethodsProspective, observational, multicentre registry of ARDS patients. Respiratory mechanics were measured early after intubation at 6 kg/ml tidal volume. We compared the predictive power of the parameters for mortality at day-60 through receiver operating characteristic (ROC) and assessed their association with 60-day mortality through unadjusted and adjusted Cox regressions. Finally, each parameter was dichotomized, and Kaplan–Meier survival curves were compared.Results385 patients were enrolled 2 [1–4] days from intubation (esophageal pressure and arterial blood gases in 302 and 318 patients). As continuous variables, DPaw, DPL, and oxygenation stretch index were associated with 60-day mortality after adjustment for age and Sequential Organ Failure Assessment, whereas elastance-derived plateau PL was not. DPaw and DPL performed equally in ROC analysis (P = 0.0835). DPaw had the best-fit Cox regression model. When dichotomizing the variables, DPaw ≥ 15, DPL ≥ 12, plateau PL ≥ 24, and oxygenation stretch index < 10 exhibited lower 60-day survival probability. Directly measured end-expiratory PL ≥ 0 was associated with better outcome in obese patients.ConclusionDPL was equivalent predictor of outcome than DPaw. Our study supports the soundness of limiting lung and airway driving pressure and maintaining positive end-expiratory PL in obese patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00134-022-06724-y.

Asymmetrical Lung Injury: Management and Outcome.

Among mechanically ventilated patients, asymmetrical lung injury is probably extremely frequent in the intensive care unit but the lack of standardized measurements does not allow to describe any prevalence among mechanically ventilated patients. Many past studies have focused only on unilateral injury and have mostly described the effect of lateral positioning. The good lung put downward might receive more perfusion while the sick lung placed upward receive more ventilation than supine. This usually results in better oxygenation but can also promote atelectasis in the healthy lung and no consensus has emerged on the clinical indication of this posture. Recently, electrical impedance tomography (EIT) has allowed for the first time to precisely describe the distribution of ventilation in each lung and to better study asymmetrical lung injury. At low positive-end-expiratory pressure (PEEP), a very heterogeneous ventilation exists between the two lungs and the initial increase in PEEP first helps to recruit the sick lung and protect the healthier lung. However, further increasing PEEP distends the less injured lung and must be avoided. The right level can be found using EIT and transpulmonary pressure. In addition, EIT can show that in the two lungs, airway closure is present but with very different airway opening pressures (AOPs) which cannot be identified on a global assessment. This may suggest a very different PEEP level than on a global assessment. Lastly, epidemiological studies suggest that in hypoxemic patients, the number of quadrants involved has a strong prognostic value. The number of quadrants is more important than the location of the unilateral or bilateral nature of the involvement for the prognosis, and hypoxemic patients with unilateral lung injury should probably be considered as requiring lung protective ventilation as classical acute respiratory distress syndrome.

Dynamic Relative Regional Lung Strain Estimated by Electrical Impedance Tomography in an Experimental Model of ARDS.

To analyze the role of PEEP on dynamic relative regional strain (DRRS) in a model of ARDS, respective maps were generated by electrical impedance tomography (EIT). Eight ARDS pigs submitted to PEEP steps of 0, 5, 10, and 15 cm H2O at fixed ventilation were evaluated by EIT images. DRRS was calculated as (VT-EIT/EELI)/(VT-EIT[15PEEP]/EELI[15PEEP]), where the tidal volume (VT)-EIT and end-expiratory lung impedance (EELI) are the tidal and end-expiratory change in lung impedance, respectively. The measurement at 15 PEEP was taken as reference (end-expiratory transpulmonary pressure > 0 cm H2O). The relationship between EIT variables (center of ventilation, EELI, and DRRS) and airway pressures was assessed with mixed-effects models using EIT measurements as dependent variables and PEEP as fixed-effect variable. At constant ventilation, respiratory compliance increased progressively with PEEP (lowest value at zero PEEP 10 ± 3 mL/cm H2O and highest value at 15 PEEP 16 ± 6 mL/cm H2O; P < .001), whereas driving pressure decreased with PEEP (highest value at zero PEEP 34 ± 6 cm H2O and lowest value at 15 PEEP 21 ± 4 cm H2O; P < .001). The mixed-effect regression models showed that the center of ventilation moved to dorsal lung areas with a slope of 1.81 (1.44-2.18) % points by each cm H2O of PEEP; P < .001. EELI increased with a slope of 0.05 (0.02-0.07) (arbitrary units) for each cm H2O of PEEP; P < .001. DRRS maps showed that local strain in ventral lung areas decreased with a slope of -0.02 (-0.24 to 0.15) with each cm H2O increase of PEEP; P < .001. EIT-derived DRRS maps showed high strain in ventral lung zones at low levels of PEEP. The findings suggest overdistention of the baby lung.

Retrospective Review of Transpulmonary Pressure Guided Positive End-Expiratory Pressure Titration for Mechanical Ventilation in Class II and III Obesity.

OBJECTIVES:Acute respiratory distress syndrome is treated by utilizing a lung protective ventilation strategy. Obesity presents with additional physiologic considerations, and optimizing ventilator settings may be limited with traditional means. Transpulmonary pressure (PL) obtained via esophageal manometry may be more beneficial to titrating positive end-expiratory pressure (PEEP) in this population. We sought to determine the feasibility and impact of implementation of a protocol for use of esophageal balloon to set PEEP in obese patients in a community ICU.DESIGN:Retrospective cohort study of obese (body mass index [BMI] ≥ 35 kg/m2) patients undergoing individualized PEEP titration with esophageal manometry. Data were extracted from electronic health record, and Wilcoxon signed rank test was performed to determine whether there were differences in the ventilatory parameters over time.SETTING:Intensive care unit in a community based hospital system in Newark, Delaware.PATIENTS:Twenty-nine mechanically ventilated adult patients with a median BMI of 45.8 kg/m2 with acute respiratory distress syndrome (ARDS).INTERVENTION:Individualized titration of PEEP via esophageal catheter obtained transpulmonary pressures.MEASUREMENTS AND MAIN RESULTS:Outcomes measured include PEEP, oxygenation, and driving pressure (DP) before and after esophageal manometry at 4 and 24 hr. Clinical outcomes including adverse events (pneumothorax and pneumomediastinum), increased vasopressor use, rescue therapies (inhaled pulmonary vasodilators, extracorporeal membrane oxygenation, and new prone position), continuous renal replacement therapy, and tracheostomy were also analyzed. Four hours after PEEP titration, median PEEP increased from 12 to 20 cm H2O (p < 0.0001) with a corresponding decrease in median DP from 15 to 13 cm H2O (p = 0.002). Subsequently, oxygenation improved as median Fio2 decreased from 0.8 to 0.6 (p < 0.0001), and median oxygen saturation/Fio2 (S/F) ratio improved from 120 to 165 (p < 0.0001). One patient developed pneumomediastinum. No pneumothoraces were identified. Improvements in oxygenation continued to be seen at 24 hr, compared with the prior 4 hr mark, Fio2 (0.6–0.45; p < 0.004), and S/F ratio (165–211.11; p < 0.001). Seven patients required an increase in vasopressor support after 4 hours. Norepinephrine and epinephrine were increased by 0.05 (± 0.04) µg/kg/min and 0.02 (± 0.01) µg/kg/min on average, respectively.CONCLUSIONS:PL-guided PEEP titration in obese patients can be used to safely titrate PEEP and decrease DP, resulting in improved oxygenation.

Ventilator management using esophageal balloon pressure measurements

Mechanical ventilation provides essential support for patients with acute respiratory failure and provides time for these patients to recover from the primary disorder. Ventilator strategies need to provide adequate oxygenation and avoid barotrauma. This trauma develops when some regions of the lungs are overinflated and develops when some regions are underinflated and have cyclical opening and closing during the respiratory cycle. The ARDS network trial demonstrated that a low tidal volume and low pressure strategy improved outcomes. Subsequent trials have tried to determine the optimal PEEP level in patients with moderate to severe ARDS. The use of esophageal balloons provides information about the transpulmonary pressure at the end of inspiration and the transpulmonary pressure at the end of expiration. However, available studies to date do not demonstrate a definite improvement in outcomes in patients with ventilator adjustments based on esophageal pressures. Beitler et al. randomized 200 patients with moderate to severe ARDS into one group in which PEEP titration was based on esophageal balloon pressure measurements, and a second group in which PEEP titration was based on a high FiO2/PEEP table studied in earlier trials. There were no differences in mortality between the two groups. Reanalysis of this information after the trial was completed suggested that transpulmonary pressures in the range of -2 to + 2 cm H2O at the end of expiration were associated with improved outcomes compared to pressures outside that range.

Risk Factors for Pulmonary Air Leak and Clinical Prognosis in Patients With COVID-19 Related Acute Respiratory Failure: A Retrospective Matched Control Study.

BackgroundThe role of excessive inspiratory effort in promoting alveolar and pleural rupture resulting in air leak (AL) in patients with SARS-CoV-2 induced acute respiratory failure (ARF) while on spontaneous breathing is undetermined.MethodsAmong all patients with COVID-19 related ARF admitted to a respiratory intensive care unit (RICU) and receiving non-invasive respiratory support, those developing an AL were and matched 1:1 [by means of PaO2/FiO2 ratio, age, body mass index-BMI and subsequent organ failure assessment (SOFA)] with a comparable population who did not (NAL group). Esophageal pressure (ΔPes) and dynamic transpulmonary pressure (ΔPL) swings were compared between groups. Risk factors affecting AL onset were evaluated. The composite outcome of ventilator-free-days (VFD) at day 28 (including ETI, mortality, tracheostomy) was compared between groups.ResultsAir leak and NAL groups (n = 28) showed similar ΔPes, whereas AL had higher ΔPL (20 [16–21] and 17 [11–20], p = 0.01, respectively). Higher ΔPL (OR = 1.5 95%CI[1–1.8], p = 0.01), positive end-expiratory pressure (OR = 2.4 95%CI[1.2–5.9], p = 0.04) and pressure support (OR = 1.8 95%CI[1.1–3.5], p = 0.03), D-dimer on admission (OR = 2.1 95%CI[1.3–9.8], p = 0.03), and features suggestive of consolidation on computed tomography scan (OR = 3.8 95%CI[1.1–15], p = 0.04) were all significantly associated with AL. A lower VFD score resulted in a higher risk (HR = 3.7 95%CI [1.2–11.3], p = 0.01) in the AL group compared with NAL. RICU stay and 90-day mortality were also higher in the AL group compared with NAL.ConclusionIn spontaneously breathing patients with COVID-19 related ARF, higher levels of ΔPL, blood D-dimer, NIV delivery pressures and a consolidative lung pattern were associated with AL onset.

Phrenic Nerve Block and Respiratory Effort in Pigs and Critically Ill Patients with Acute Lung Injury.

Strong spontaneous inspiratory efforts can be difficult to control and prohibit protective mechanical ventilation. Instead of using deep sedation and neuromuscular blockade, the authors hypothesized that perineural administration of lidocaine around the phrenic nerve would reduce tidal volume (VT) and peak transpulmonary pressure in spontaneously breathing patients with acute respiratory distress syndrome. An established animal model of acute respiratory distress syndrome with six female pigs was used in a proof-of-concept study. The authors then evaluated this technique in nine mechanically ventilated patients under pressure support exhibiting driving pressure greater than 15 cm H2O or VT greater than 10 ml/kg of predicted body weight. Esophageal and transpulmonary pressures, electrical activity of the diaphragm, and electrical impedance tomography were measured in pigs and patients. Ultrasound imaging and a nerve stimulator were used to identify the phrenic nerve, and perineural lidocaine was administered sequentially around the left and right phrenic nerves. Results are presented as median [interquartile range, 25th to 75th percentiles]. In pigs, VT decreased from 7.4 ml/kg [7.2 to 8.4] to 5.9 ml/kg [5.5 to 6.6] (P < 0.001), as did peak transpulmonary pressure (25.8 cm H2O [20.2 to 27.2] to 17.7 cm H2O [13.8 to 18.8]; P < 0.001) and driving pressure (28.7 cm H2O [20.4 to 30.8] to 19.4 cm H2O [15.2 to 22.9]; P < 0.001). Ventilation in the most dependent part decreased from 29.3% [26.4 to 29.5] to 20.1% [15.3 to 20.8] (P < 0.001). In patients, VT decreased (8.2 ml/ kg [7.9 to 11.1] to 6.0 ml/ kg [5.7 to 6.7]; P < 0.001), as did driving pressure (24.7 cm H2O [20.4 to 34.5] to 18.4 cm H2O [16.8 to 20.7]; P < 0.001). Esophageal pressure, peak transpulmonary pressure, and electrical activity of the diaphragm also decreased. Dependent ventilation only slightly decreased from 11.5% [8.5 to 12.6] to 7.9% [5.3 to 8.6] (P = 0.005). Respiratory rate did not vary. Variables recovered 1 to 12.7 h [6.7 to 13.7] after phrenic nerve block. Phrenic nerve block is feasible, lasts around 12 h, and reduces VT and driving pressure without changing respiratory rate in patients under assisted ventilation.

Effects of different positive end-expiratory pressure titration strategies during prone positioning in patients with acute respiratory distress syndrome: a prospective interventional study

BackgroundProne positioning in combination with the application of low tidal volume and adequate positive end-expiratory pressure (PEEP) improves survival in patients with moderate to severe acute respiratory distress syndrome (ARDS). However, the effects of PEEP on end-expiratory transpulmonary pressure (Ptpexp) during prone positioning require clarification. For this purpose, the effects of three different PEEP titration strategies on Ptpexp, respiratory mechanics, mechanical power, gas exchange, and hemodynamics were evaluated comparing supine and prone positioning.MethodsIn forty consecutive patients with moderate to severe ARDS protective ventilation with PEEP titrated according to three different titration strategies was evaluated during supine and prone positioning: (A) ARDS Network recommendations (PEEPARDSNetwork), (B) the lowest static elastance of the respiratory system (PEEPEstat,RS), and (C) targeting a positive Ptpexp (PEEPPtpexp). The primary endpoint was to analyze whether Ptpexp differed significantly according to PEEP titration strategy during supine and prone positioning.ResultsPtpexp increased progressively with prone positioning compared with supine positioning as well as with PEEPEstat,RS and PEEPPtpexp compared with PEEPARDSNetwork (positioning effect p < 0.001, PEEP strategy effect p < 0.001). PEEP was lower during prone positioning with PEEPEstat,RS and PEEPPtpexp (positioning effect p < 0.001, PEEP strategy effect p < 0.001). During supine positioning, mechanical power increased progressively with PEEPEstat,RS and PEEPPtpexp compared with PEEPARDSNetwork, and prone positioning attenuated this effect (positioning effect p < 0.001, PEEP strategy effect p < 0.001). Prone compared with supine positioning significantly improved oxygenation (positioning effect p < 0.001, PEEP strategy effect p < 0.001) while hemodynamics remained stable in both positions.ConclusionsProne positioning increased transpulmonary pressures while improving oxygenation and hemodynamics in patients with moderate to severe ARDS when PEEP was titrated according to the ARDS Network lower PEEP table. This PEEP titration strategy minimized parameters associated with ventilator-induced lung injury induction, such as transpulmonary driving pressure and mechanical power. We propose that a lower PEEP strategy (PEEPARDSNetwork) in combination with prone positioning may be part of a lung protective ventilation strategy in patients with moderate to severe ARDS.Trial registrationGerman Clinical Trials Register (DRKS00017449). Registered June 27, 2019. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00017449

Pediatrik aktif hastalarda asenkroninin basınç zaman ürününe etkisinin (PTP) değerlendirmesi

Aim: To reveal the effect of synchronous or asynchronous patients on these values by examining the esophageal pressure (Pes ), transpulmonary pressure (PL), and time-pressure-product (PTP) in active patients who are planned to be weaned from the mechanical ventilator and can trigger their own respiration.&#x0D; Material and Methods: Patients who are monitored on a mechanical ventilator and who can trigger their own respiration, and who are planned to be separated from the mechanical ventilator in the near future, were taken and an esophageal catheter was inserted, then the catheter filling volume was first optimized and then validated, and PL was started to be recorded by removing Pes from the airway pressure. With the recording devices on the ventilator, the mechanical ventilation parameters of the patients were recorded as both monitoring values and waveforms. Then, the mechanical ventilation settings were rearranged by the clinician at the bedside with reference to the esophageal waveform. Then, the waveforms of these patients have examined on the Matlab E2019a (Mathworks, USA) software, and each breath was marked as synchronous-asynchronous and the asynchrony index (AI) was calculated. Accordingly, the asynchronous and synchronous periods of the patient were defined, and the values of ∆Pes, ∆PL, PTP-Pes, PTP-PL, PTP-Pes-minutes, PTP-PL-minutes between the synchronous and asynchronous periods of the same patient were calculated on Matlab software, and synchronous and The changes in these values between asynchronous periods were analyzed with the SPSS statistical program. After examining the distribution of the variables by visual and analytical methods (Shapiro-Wilk), the statistical difference between the groups was examined.&#x0D; Results: When the synchronous and asynchronous periods of all patients were compared, the following differences were found between the synchronous and asynchronous groups in favor of the synchronous group. ∆Peso [5.98 (3.55-9.08)] cmH2O, ∆PL [5 (2.7-7.25]cmH2O, ∆PTP-Peso [3.70 (2.81-4.6)) ]cmH2O*s, ∆PTP-PL [3.36 (1.39-4.18)]cmH2O*s, ∆PTP-Peso/min [1.72 (1.02-2.67)]cmH2O*min , ∆PTP-PL/min [1.25 (0.30-3.01)]cmH2O*min.&#x0D; Conclusion: It has also been shown by statistical analyzes that the synchronization of active patients who are planned to be weaned from mechanical ventilator and who can trigger their own respiration causes a decrease in the values of ∆Peso, ∆Ptranspulmonary, PTP-Peso,PTP-Ptranspulmonary, PTP-Peso-minute, PTP-Ptranspulmonary-minute. When this information about synchronization is correlated with the literature, Pes monitoring in patients and synchronization of patients prevent mechanical ventilation-related lung damage that may occur in these patients, and thus the duration of hospital stay due to asynchrony, failure to wean from the ventilator, and the consequences that may occur. It is a method that can be useful in reducing mortality and morbidity.

High-Flow Nasal Cannula Reduces Effort of Breathing But Not Consistently via Positive End-Expiratory Pressure

High-flow nasal cannula (HFNC) therapy reduces the effort of breathing in patients with bronchiolitis, but the mechanisms are not understood. Theorized mechanisms include dead space washout and positive end-expiratory pressure (PEEP) application. What are the mechanisms of action of HFNC therapy in patients with bronchiolitis? Prospective, single-center study of children 3 years of age or younger with bronchiolitis from January 2020 through March 2021. Flow was titrated between 0.5 and 2 L/kg/min. Electrical impedance tomography measured end-expiratory lung impedance (EELZ) change as an end-expiratory lung volume (EELV) change surrogate and change in tidal impedance difference (ΔZ) as a tidal volume (VT) surrogate. A subset showed manometry measuring esophageal pressure change (ΔPes; transpulmonary pressure surrogate) and pressure rate product (PRP; effort of breathing metric). We hypothesized that EELV and VT would not change and that effort would reduce via respiratory rate (not ΔPes). Measurements were reported as the difference from 0.5 L/kg/min. We studied 22 patients in total, 10 with esophageal manometry. Median EELZ increased by 0.36 arbitrary unit (AU), 2.42 AU, and 4.8 AU at 1 L/kg/min, 1.5 L/kg/min, and 2 L/kg/min (P= .01, 2 L/kg/min vs0.5 L/kg/min), which corresponded to a median increase in EELV of 1.8mL/kg between 0.5 and 2 L/kg/min. Seven patients showed an increase in EELZ of > 5 AU, 12 showed no change in EELZ (± 5 AU), and three showed a decrease in EELZ of > 5 AU. ΔZ (ie, VT) did not change from 0.5 L/kg/min to 2 L/kg/min (median change, 0.29 AU; P= .48). Median PRP decreased by 78cm H2O/min from 0.5 L/kg/min to 2 L/kg/min (P= .02), with all patients demonstrating a reduction in PRP, with a nonsignificant change in ΔPes (P= .68). Increasing HFNC in children with bronchiolitis reduces the effort of breathing, but no consistent increase occurs in end-expiratory lung volume and no significant change occurs in VT or transpulmonary pressure. This suggests that PEEP application is not the primary mechanism of action of HFNC in children with bronchiolitis.

Right Ventricular Loading by Lung Inflation during Controlled Mechanical Ventilation.

Rationale: The inspiratory rise in transpulmonary pressure during mechanical ventilation increases right ventricular (RV) afterload. One mechanism is that when Palv exceeds left atrial pressure, West zone 1 or 2 (non-zone 3) conditions develop, and Palv becomes the downstream pressure opposing RV ejection. The Vt at which this impact on the right ventricle becomes hemodynamically evident is not well established. Objectives: To determine the magnitude of RV afterload and prevalence of significant non-zone 3 conditions during inspiration across the range of Vt currently prescribed in clinical practice. Methods: In postoperative passively ventilated cardiac surgery patients, we measured right atrial, right ventricle, pulmonary artery, pulmonary artery occlusion pressure, plateau pressure, and esophageal pressure during short periods of controlled ventilation, with Vt increments ranging between 2 and 12 ml/kg predicted body weight (PBW). The inspiratory increase in RV afterload was evaluated hemodynamically and echocardiographically. The prevalence of non-zone 3 conditions was determined using two definitions based on changes in esophageal pressure, pulmonary artery occlusion pressure, and plateau pressure. Measurements and Main Results: Fifty-one patients were studied. There was a linear relationship between Vt, driving pressure, transpulmonary pressure, and the inspiratory increase in the RV isovolumetric contraction pressure. Echocardiographically, increasing Vt was associated with a greater inspiratory increase in markers of afterload and a decrease in stroke volume. Non-zone 3 conditions were present in >50% of subjects at a Vt ⩾ 6 ml/kg PBW. Conclusions: In the Vt range currently prescribed, RV afterload increases with increasing Vt. A mechanical ventilation strategy that limits Vt and driving pressure is cardioprotective.

Anesthetic management of a single-ventricle pediatric patient with scoliosis: A case report

Single ventricle is a complex cardiac disease which carry high morbidity and mortality and the average 3 years survival rate without Fontan procedure was approximated to be 75%. The most common etiologies are: hypoplastic left heart syndrome and tricuspid atresia. When those patient plan to go for surgery, it’s very essential for anesthetist to understand how the physiology is affected rather than etiology. BT shunt patency, right ventricular function and pulmonary artery pressure should be evaluated before any procedure under anesthesia. Scoliosis corrective surgery is a procedure that has its special considerations related to restrictive pulmonary disease, prone positioning, and major bleeding that may occur, which altogether will add to the risk when being conducted in a single-ventricle patient and will necessitate vigilance and special care during monitoring intraoperatively. Here, we report a simple way to monitor the transpulmonary pressure gradient through two central lines in the femoral and jugular veins as part of the patient’s anesthesia management.

Positive end-expiratory pressure setting based on transpulmonary pressure during robot-assisted laparoscopic prostatectomy: an observational intervention study

BackgroundIn robot-assisted laparoscopic prostatectomy (RALP), concerns include the formation of atelectasis and reduced functional residual capacity. The present study aimed to examine the feasibility of positive end-expiratory pressure (PEEP) setting based on transpulmonary pressure (Ptp) as well as the effects of incremental PEEP on respiratory mechanics, blood gases, cerebral oxygenation (rSO2), and hemodynamics.MethodsFourteen male patients who were scheduled to receive RALP were recruited. Patients received mechanical ventilation (tidal volume of 6 mL kg−1) and were placed in Trendelenburg position with positive-pressure capnoperitoneum. PEEP levels were increased from 0 to 15 cmH2O (5 cmH2O per increase) every 30 min. PEEP levels were assessed where end-expiratory Ptp levels of ≥0 cmH2O were achieved (PtpEEP0). Airway pressure, esophageal pressure, cardiac index, and blood gas and rSO2 values were measured after 30 min at each PEEP step and respiratory mechanics were calculated.ResultsWith increasing PEEP levels from 0 to 15 cmH2O or PtpEEP0, the values of PaO2 and respiratory system compliance increased, and the values of driving pressure decreased. The median PEEP level associated with PtpEEP0 was 15 cmH2O. Respiratory system compliance values were higher at PtpEEP0 than those at PEEP5 (P = 0.02). Driving pressure was significantly lower at PtpEEP0 than at PEEP5 (P = 0.0036). The cardiac index remained unchanged, and the values of rSO2 were higher at PtpEEP0 than at PEEP0 (right; P = 0.0019, left; P = 0.036).ConclusionsPEEP setting determined by transpulmonary pressure can help achieve higher respiratory system compliance values and lower driving pressure without disturbing hemodynamic parameters.

Lung- and Diaphragm-Protective Ventilation by Titrating Inspiratory Support to Diaphragm Effort: A Randomized Clinical Trial.

Lung- and diaphragm-protective ventilation is a novel concept that aims to limit the detrimental effects of mechanical ventilation on the diaphragm while remaining within limits of lung-protective ventilation. The premise is that low breathing effort under mechanical ventilation causes diaphragm atrophy, whereas excessive breathing effort induces diaphragm and lung injury. In a proof-of-concept study, we aimed to assess whether titration of inspiratory support based on diaphragm effort increases the time that patients have effort in a predefined "diaphragm-protective" range, without compromising lung-protective ventilation. Randomized clinical trial. Mixed medical-surgical ICU in a tertiary academic hospital in the Netherlands. Patients (n = 40) with respiratory failure ventilated in a partially-supported mode. In the intervention group, inspiratory support was titrated hourly to obtain transdiaphragmatic pressure swings in the predefined "diaphragm-protective" range (3-12 cm H2O). The control group received standard-of-care. Transdiaphragmatic pressure, transpulmonary pressure, and tidal volume were monitored continuously for 24 hours in both groups. In the intervention group, more breaths were within "diaphragm-protective" range compared with the control group (median 81%; interquartile range [64-86%] vs 35% [16-60%], respectively; p < 0.001). Dynamic transpulmonary pressures (20.5 ± 7.1 vs 18.5 ± 7.0 cm H2O; p = 0.321) and tidal volumes (7.56 ± 1.47 vs 7.54 ± 1.22 mL/kg; p = 0.961) were not different in the intervention and control group, respectively. Titration of inspiratory support based on patient breathing effort greatly increased the time that patients had diaphragm effort in the predefined "diaphragm-protective" range without compromising tidal volumes and transpulmonary pressures. This study provides a strong rationale for further studies powered on patient-centered outcomes.

Serum Surfactant Protein-D (SP-D) Level: Does it Correlates with Pulmonary Compliance and ARDS in Severe Cases of COVID-19?

Acute Respiratory Distress Syndrome (ARDS) happens to 67% of all severe COVID-19 cases with mortality rate of 50-94%. Main characteristics of ARDS are poor oxygenation and non-compliant lungs. The lungs are like inflatable balloons that are actively inflated by the positive pressure within and/or the negative pressure created in the pleural cavity. Compliance is the ability of the lungs to distend at a certain level of transpulmonary pressure. Surfactant lowers the surface tension of the alveoli so that end-expiratory pulmonary collapse could be prevented and pulmonary compliance could be maintained. Surfactants also play an important role in the host's defense against infection. Surfactants comprise of phospholipids, cholesterol and surfactant proteins (SP) SP-A, -B, -C and –D. Previous study showed that concentration of SP-D was significantly higher in ARDS patients. Higher serum SP-D concentrations were associated with a greater risk of death, fewer ventilator-free days, and fewer organ failure-free days. This review highlights the role of surfactant especially SP-D in pulmonary compliance and ARDS in COVID-19.

Interpretation and use of intraoperative protective ventilation parameters: a scoping review.

Thirty years ago, the traditional approach to mechanical ventilation consisted of the normalization of PaCO2 and pH at the expense of using a tidal volume (VT) of 10-15 mL kg-1. But then, the use of 6-8 mL kg-1 became a dogma for ventilating patients either with acute respiratory distress syndrome (ARDS) or without lung disease in the operating theatre. It is currently recognized that even low tidal volumes may be excessive for some patients and insufficient for others, depending on its distribution in the aerated lung parenchyma. To carry out intraoperative protective mechanical ventilation, medical literature has focused on positive end expiratory pressure (PEEP), plateau pressure (Paw plateau), and airway driving pressure (ΔPaw). However, considering its limitations, other parameters have emerged that represent a better reflection of isolated lung stress, such as transpulmonary pressure (PL) and transpulmonary driving pressure (ΔPL). These parameters are less generalized in clinical practice due to the requirement of an oeso-phageal balloon for their measurement and therefore their cumbersome application in the operating theatre. However, its study helps in the interpretation of the rest of the ventilator pressures to optimize intraoperative mechanical ventilation. This article defines and develops protective ventilation parameters, breaks down their determinants, mentions their limitations, and offers recommendations for their use intraoperatively.

New insights in mechanical ventilation and adjunctive therapies in ARDS

Patients with acute respiratory distress syndrome (ARDS) often require mechanical ventilation (MV) and may experience high morbidity and mortality. The ventilatory management of ARDS patients has changed over the years to mitigate the risk of ventilator-induced lung injury (VILI) and improve outcomes. Current recommended MV strategies include the use of low tidal volume (VT) at 4–6 mL/kg of predicted body weight (PBW) and plateau pressure (PPLAT ) below 27 cmH2O. Some patients achieve better outcomes with low VT than others, and several strategies have been proposed to individualize VT , including standardization for end-expiratory lung volume or inspiratory capacity. To date, no strategy for individualizing positive-end expiratory pressure (PEEP) based on oxygenation, recruitment, respiratory mechanics, or hemodynamics has proven superior for improving survival. Driving pressure, transpulmonary pressure, and mechanical power have been proposed as markers to quantify risk of VILI and optimize ventilator settings. Several rescue therapies, including neuromuscular blockade, prone positioning, recruitment maneuvers (RMs), vasodilators, and extracorporeal membrane oxygenation (ECMO), may be considered in severe ARDS. New ventilator strategies such as airway pressure release ventilation (APRV) and time-controlled adaptive ventilation (TCAV) have demonstrated potential benefits to reduce VILI, but further studies are required to evaluate their clinical relevance. This review aims to discuss the cornerstones of MV and new insights in ARDS ventilatory management, as well as their rationales, to guide the physician in an individually tailored rather than a fixed, sub-physiological approach. We recommend that MV be individualized based on physiological targets to achieve optimal ventilatory settings for each patient.

Reproducible determination of transpulmonary pressures

Oesophageal pressures, as measured in an oesophageal balloon catheter, are a validated substitute for pleural pressures.Transpulmonary pressures, indispensable to improve our understanding of ventilatory physiology, are therefore typically calculated as the difference between airway and oesophageal pressures.The oesophageal pressure signal, however, features a superimposed oscillation due to cardiac motion, not representative for pleural pressure. Additionally, oesophageal contractions or surgical manipulation can alter the signal. In practice, transpulmonary pressures are therefore manually determined from the pressure-time graphic by visual inspection of the waves and averaging a limited number of samples.We suggest an approach to extract the end-expiratory transpulmonary pressure from the raw monitoring data.•Our approach reproducibly determines end-expiratory transpulmonary pressures at a given level of set positive end-expiratory pressure at the ventilator.•Our approach ignores surgical disturbance and cardiac oscillations in the oesophageal pressure signal.