PEEP Levels Research Articles

Frequency of Screening and Spontaneous Breathing Trial Techniques

The optimal screening frequency and spontaneous breathing trial (SBT) technique to liberate adults from ventilators are unknown. To compare the effects of screening frequency (once-daily screening vs more frequent screening) and SBT technique (pressure-supported SBT with a pressure support level that was >0-≤8 cm H2O and a positive end-expiratory pressure [PEEP] level that was >0-≤5 cm H2O vs T-piece SBT) on the time to successful extubation. Randomized clinical trial with a 2 × 2 factorial design including critically ill adults who were receiving invasive mechanical ventilation for at least 24 hours, who were capable of initiating spontaneous breaths or triggering ventilators, and who were receiving a fractional concentration of inspired oxygen that was 70% or less and a PEEP level of 12 cm H2O or less. Recruitment was between January 2018 and February 2022 at 23 intensive care units in North America; last follow-up occurred October 18, 2022. Participants were enrolled early to enable protocolized screening (more frequent vs once daily) to identify the earliest that patients met criteria to undergo pressure-supported or T-piece SBT lasting 30 to 120 minutes. Time to successful extubation (time when unsupported, spontaneous breathing began and was sustained for ≥48 hours after extubation). Of 797 patients (198 in the once-daily screening and pressure-supported SBT group, 204 in once-daily screening and T-piece SBT, 195 in more frequent screening and pressure-supported SBT, and 200 in more frequent screening and T-piece SBT), the mean age was 62.4 (SD, 18.4) years and 472 (59.2%) were men. There were no statistically significant differences by screening frequency (hazard ratio [HR], 0.88 [95% CI, 0.76-1.03]; P = .12) or by SBT technique (HR, 1.06 [95% CI, 0.91-1.23]; P = .45). The median time to successful extubation was 2.0 days (95% CI, 1.7-2.7) for once-daily screening and pressure-supported SBT, 3.1 days (95% CI, 2.7-4.8) for once-daily screening and T-piece SBT, 3.9 days (95% CI, 2.9-4.7) for more frequent screening and pressure-supported SBT, and 2.9 days (95% CI, 2.0-3.1) for more frequent screening and T-piece SBT. An unexpected interaction between screening frequency and SBT technique required pairwise contrasts that revealed more frequent screening (vs once-daily screening) and pressure-supported SBT increased the time to successful extubation (HR, 0.70 [95% CI, 0.50-0.96]; P = .02). Once-daily screening and pressure-supported SBT (vs T-piece SBT) did not reduce the time to successful extubation (HR, 1.30 [95% CI, 0.98-1.70]; P = .08). Among critically ill adults who received invasive mechanical ventilation for more than 24 hours, screening frequency (once-daily vs more frequent screening) and SBT technique (pressure-supported vs T-piece SBT) did not change the time to successful extubation. However, an unexpected and statistically significant interaction was identified; protocolized more frequent screening combined with pressure-supported SBTs increased the time to first successful extubation. ClinicalTrials.gov Identifiers: NCT02399267 and NCT02969226.

Lung ultrasound assessment of atelectasis following different anesthesia induction techniques in pediatric patients: a propensity score-matched, observational study

IntroductionAtelectasis is a well-documented complication in pediatric patients undergoing general anesthesia. Its incidence varies significantly based on surgical procedures and anesthesia techniques. Inhalation induction, commonly used to avoid the discomfort of venipuncture, is suspected to cause higher rates of respiratory complications, including atelectasis, compared to intravenous induction. This study aimed to evaluate the impact of inhalation versus intravenous anesthesia induction on atelectasis formation in pediatric patients, as assessed by lung ultrasound (LUS).MethodsThis propensity score-matched observational study was conducted at a tertiary pediatric hospital in Milan, Italy. Inclusion criteria were children ≤ 18 years undergoing elective surgery with general anesthesia. Patients were divided into inhalation and intravenous induction groups. LUS was performed before and after anesthesia induction to assess lung aeration. The primary endpoint was the global LUS score post-induction, with secondary endpoints including the incidence and distribution of atelectasis.ResultsOf the 326 patients included, 65% underwent inhalation induction and 35% intravenous induction. The global LUS score was significantly higher in the inhalation group (12.0 vs. 4.0, p < 0.001). After propensity score matching (for age, presence of upper respiratory tract infection, duration of induction, and PEEP levels at induction), average treatment effect (ATE) of mask induction was 5.89 (95% CI, 3.21–8.58; p < 0.001) point on LUS global score and a coefficient of 0.35 (OR 1.41) for atelectasis.DiscussionInhalation induction is associated with a higher incidence of atelectasis in pediatric patients also when we adjusted for clinically relevant covariates.Trial registrationClinicalTrials.gov identifier: NCT06069414.

Risk of pulmonary complications after video-assisted thoracoscopic pulmonary resection in children.

Postoperative pulmonary complications (PPCs) are associated with high mortality and morbidity rates. Children are more susceptible to PPCs owing to smaller functional residual capacity and greater closing volume. Risk factors of PPCs in children undergoing lung resection remain unclear. This retrospective study enrolled children who underwent video-assisted thoracoscopic surgery between January 2018 and February 2023. The primary outcome was PPC occurrence. Multivariate logistic regression was used to analyze risk factors for PPCs. Overall, 640 children were analyzed; their median age was 7 (interquartile range: 5-11) months, and the median tidal volume was 7.66 (6.59-8.49) mL/kg. One hundred and seventeen (18.3%) developed PPCs. PPCs were independently associated with male sex (odds ratio [OR], 1.83; 95% confidence interval [CI], 1.17-2.88; P=0.008), longer OLV duration (OR, 1.01; 95% CI, 1.0-1.01; P=0.001), and less surgeon's experience (OR, 1.67; 95% CI, 1.03-2.7; P=0.036). When low-tidal-volume cutoff was defined as <8 mL/kg, PEEP level was a protective factor for PPCs (OR, 0.83; 95% CI, 0.69-1.00; P=0.046). Additionally, PPCs were associated with increased hospital stay (P<0.001). Male sex, longer OLV duration, less surgeon's experience, and lower PEEP were risk factors of PPCs in children undergoing video-assisted thoracoscopic surgery. Our findings may serve as targets for prospective studies investigating specific ventilation strategies for children.

Acute renal response to changes in carbon dioxide in mechanically ventilated female pigs.

Kidney response to acute and mechanically induced variation in ventilation associated with different levels of PEEP has not been investigated. We aimed to quantify the effect of ventilatory settings on renal acid-base compensation. Forty-one pigs undergoing hypo- (<0.2 Lkg-1 min-1, PEEP 25 cmH2O), intermediate (0.2-0.4 Lkg-1 min-1 with either PEEP 5 or 25 cmH2O), or hyper-ventilation (>0.4 Lkg-1 min-1, PEEP 5 cmH2O) for 48 h were retrospectively included. The decrease in pH paralleled the decrease in plasma strong ion difference (SID) in hyper- and intermediately ventilated groups with lower PEEP. In contrast, the plasma SID remained nearly constant in hypo- and intermediately ventilated groups with higher PEEP. Changes in plasma chloride concentration accounted for the changes in plasma SID (conditional R2 = 0.86). The plasma SID changes were paralleled by mirror changes in urinary SID. Higher PEEP (25 cmH2O), compared to lower PEEP (5 cmH2O) dampened or abolished the renal compensation through its effect on hemodynamics (higher central venous and mean pulmonary pressures), irrespective of minute ventilation. During mechanical ventilation, the compensatory renal response to respiratory derangement is immediate and progressive but can be dampened by high PEEP levels.

The Impact of Increased PEEP on Hemodynamics, Respiratory Mechanics, and Oxygenation in Pediatric ARDS.

PEEP is a cornerstone treatment for children with pediatric ARDS. Unfortunately, its titration is often performed solely by evaluating oxygen saturation, which can lead to inadequate PEEP level settings and consequent adverse effects. This study aimed to assess the impact of increasing PEEP on hemodynamics, respiratory system mechanics, and oxygenation in children with ARDS. Children receiving mechanical ventilation and on pressure-controlled volume-guaranteed mode were prospectively assessed for inclusion. PEEP was sequentially changed to 5, 12, 10, 8 cm H2O, and again to 5 cm H2O. After 10 min at each PEEP level, hemodynamic, ventilatory, and oxygenation variables were collected. A total of 31 subjects were included, with median age and weight of 6 months and 6.3 kg, respectively. The main reasons for pediatric ICU admission were respiratory failure caused by acute viral bronchiolitis (45%) and community-acquired pneumonia (32%). Most subjects had mild or moderate ARDS (45% and 42%, respectively), with a median (interquartile range) oxygenation index of 8.4 (5.8-12.7). Oxygen saturation improved significantly when PEEP was increased. However, although no significant changes in blood pressure were observed, the median cardiac index at PEEP of 12 cm H2O was significantly lower than that observed at any other PEEP level (P = .001). Fourteen participants (45%) experienced a reduction in cardiac index of > 10% when PEEP was increased to 12 cm H2O. Also, the estimated oxygen delivery was significantly lower, at 12 cm H2O PEEP. Finally, respiratory system compliance significantly reduced when PEEP was increased. At a PEEP of 12 cm H2O, static compliance had a median reduction of 25% in relation to the initial assessment (PEEP of 5 cm H2O). Although it may improve arterial oxygen saturation, inappropriately high PEEP levels may reduce cardiac output, oxygen delivery, and respiratory system compliance in pediatric subjects with ARDS with low potential for lung recruitability.

The Impact of PEEP on Ventilation Distribution in ARDS.

The first aim of this study was to evaluate the capacity of electrical impedance tomography (EIT) to identify the effect of PEEP on regional ventilation distribution and the regional risk of collapse, overdistention, hypoventilation, and pendelluft in mechanically ventilated patients. The second aim was to evaluate the feasibility of EIT for estimating airway opening pressure (AOP). The EIT signal was recorded both during baseline cyclic ventilation and slow insufflation for one breath for 9 subjects with moderate-to-severe ARDS. From these data, the AOP and volumes insufflated to lung regions with or without the risk of either collapse, overdistention, hypoventilation, or pendelluft were assessed at 3 PEEP levels (5, 10, and 15 cm H2O). PEEP levels were compared by Friedman analysis of variance and the AOP measured by EIT evaluated using an F-test and the Bland and Altman method. The volume for which there was no specific risk significantly decreased at the highest PEEP from 55 ± 31% tidal volume (VT) at PEEP 5 or 82 ± 18% VT at PEEP 10 to 10 ± 30% VT at PEEP 15 (P = .038 between PEEP 5 vs PEEP 15; P = .01 between PEEP 10 vs PEEP 15). The volume associated with overdistention significantly increased with increasing PEEP, whereas that associated with atelectrauma significantly decreased. Pendelluft significantly decreased with increasing PEEP: VT of 8.9 ± 18.6%, 3.6 ± 7.0%, and 3.2 ± 7.1% for PEEP 5, PEEP 10, and PEEP 15, respectively. The center of ventilation tended to increase in the dependent direction with higher PEEP. The AOPs assessed by EIT and from the pressure-volume curve were in good agreement (bias 0.48 cm H2O). Our results suggest that EIT could aid clinicians in making personalized and reasoned choices in setting the PEEP for subjects with ARDS.

Advanced waveform analysis of diaphragm surface EMG allows for continuous non-invasive assessment of respiratory effort in critically ill patients at different PEEP levels

BackgroundRespiratory effort should be closely monitored in mechanically ventilated ICU patients to avoid both overassistance and underassistance. Surface electromyography of the diaphragm (sEMGdi) offers a continuous and non-invasive modality to assess respiratory effort based on neuromuscular coupling (NMCdi). The sEMGdi derived electrical activity of the diaphragm (sEAdi) is prone to distortion by crosstalk from other muscles including the heart, hindering its widespread use in clinical practice. We developed an advanced analysis as well as quality criteria for sEAdi waveforms and investigated the effects of clinically relevant levels of PEEP on non-invasive NMCdi.MethodsNMCdi was derived by dividing end-expiratory occlusion pressure (Pocc) by sEAdi, based on three consecutive Pocc manoeuvres at four incremental (+ 2 cmH2O/step) PEEP levels in stable ICU patients on pressure support ventilation. Pocc and sEAdi quality was assessed by applying a novel, automated advanced signal analysis, based on tolerant and strict cut-off criteria, and excluding inadequate waveforms. The coefficient of variations (CoV) of NMCdi after basic manual and automated advanced quality assessment were evaluated, as well as the effect of an incremental PEEP trial on NMCdi.Results593 manoeuvres were obtained from 42 PEEP trials in 17 ICU patients. Waveform exclusion was primarily based on low sEAdi signal-to-noise ratio (Ntolerant = 155, 37%, Nstrict = 241, 51% waveforms excluded), irregular or abrupt cessation of Pocc (Ntolerant = 145, 35%, Nstrict = 145, 31%), and high sEAdi area under the baseline (Ntolerant = 94, 23%, Nstrict = 79, 17%). Strict automated assessment allowed to reduce CoV of NMCdi to 15% from 37% for basic quality assessment. As PEEP was increased, NMCdi decreased significantly by 4.9 percentage point per cmH2O.ConclusionAdvanced signal analysis of both Pocc and sEAdi greatly facilitates automated and well-defined identification of high-quality waveforms. In the critically ill, this approach allowed to demonstrate a dynamic NMCdi (Pocc/sEAdi) decrease upon PEEP increments, emphasising that sEAdi-based assessment of respiratory effort should be related to PEEP dependent diaphragm function. This novel, non-invasive methodology forms an important methodological foundation for more robust, continuous, and comprehensive assessment of respiratory effort at the bedside.

Efficacy and Safety of High PEEP NIV in COVID-19 Patients.

To investigate the efficacy and safety of non-invasive ventilation (NIV) with high PEEP levels application in patients with COVID-19-related acute respiratory distress syndrome (ARDS). This is a retrospective cohort study with data collected from 95 patients who were administered NIV as part of their treatment in the COVID-19 intensive care unit (ICU) at University Hospital Centre Zagreb between October 2021 and February 2022. The definite outcome was NIV failure. High PEEP NIV was applied in all 95 patients; 54 (56.84%) patients could be kept solely on NIV, while 41 (43.16%) patients required intubation. ICU mortality of patients solely on NIV was 3.70%, while total ICU mortality was 35.79%. The most significant difference in the dynamic of respiratory parameters between 2 patient groups was visible on Day 3 of ICU stay: By that day, patients kept solely on NIV required significantly lower PEEP levels and had better improvement in PaO2, P/F ratio, and HACOR score. High PEEP applied by NIV was a safe option for the initial respiratory treatment of all patients, despite the severity of ARDS. For some patients, it was also shown to be the only necessary form of oxygen supplementation.

Perioperative use of high flow nasal cannula

High flow nasal cannula (HFNC) is an innovative oxygen therapy system that has gained increasing popularity in recent decades, particularly in the field of critical care medicine. The device provides a more constant and higher FiO2, generates low levels of PEEP, reduces dead space ventilation, and conditions the inspired gas, which collectively results in a reduction in work of breathing (WOB) and improved patient comfort. While the application of HFNC in critically ill patients is well-established and supported by a large body of evidence, studies of HFNC during the perioperative period are limited. However, the working mechanisms of HFNC align with physiological demands across various anesthetic processes. Consequently, this system could potentially serve as an alternative oxygen delivery system for surgical patients during perioperative care. In this article, we summarize the working principles and the effects provided by HFNC, review its implementation during the perioperative period, and discuss the current evidence regarding its use.

Association of chest computed tomography severity score at ICU admission and respiratory outcomes in critically ill COVID-19 patients.

To evaluate the association of a validated chest computed tomography (Chest-CT) severity score in COVID-19 patients with their respiratory outcome in the Intensive Care Unit. A single-center, prospective study evaluated patients with positive RT-PCR for COVID-19, who underwent Chest-CT and had a final COVID-19 clinical diagnosis needing invasive mechanical ventilation in the ICU. The admission chest-CT was evaluated according to a validated Chest-CT Severity Score in COVID-19 (Chest-CTSS) divided into low ≤50% (<14 points) and >50% high (≥14 points) lung parenchyma involvement. The association between the initial score and their pulmonary clinical outcomes was evaluated. 121 patients were clustered into the > 50% lung involvement group and 105 patients into the ≤ 50% lung involvement group. Patients ≤ 50% lung involvement (<14 points) group presented lower PEEP levels and FiO2 values, respectively GEE P = 0.09 and P = 0.04. The adjusted COX model found higher hazard to stay longer on invasive mechanical ventilation HR: 1.69, 95% CI, 1.02-2.80, P = 0.042 and the adjusted logistic regression model showed increased risk ventilator-associated pneumonia OR = 1.85 95% CI 1.01-3.39 for COVID-19 patients with > 50% lung involvement (≥14 points) on Chest-CT at ICU admission. COVID-19 patients with >50% lung involvement on Chest-CT admission presented higher chances to stay longer on invasive mechanical ventilation and more chances to developed ventilator-associated pneumonia.

Effect of different positive end expiratory pressure levels on optic nerve sheath diameter in patients with or without midline shift who are undergoing supratentorial craniotomy

PurposeIn general, high levels of PEEP application is avoided in patients undergoing craniotomy to prevent a rise in ICP. But that approach would increase the risk of secondary brain injury especially in hypoxemic patients. Because the optic nerve sheath is distensible, a rise in ICP is associated with an increase in the optic nerve sheath diameter (ONSD). The cutoff value for elevated ICP assessed by ONSD is between 5.6 and 6.3 mm. We aimed to evaluate the effect of different PEEP levels on ONSD and compare the effect of different PEEP levels in patients with and without intracranial midline shift.MethodsThis prospective observational study was performed in aged 18–70 years, ASA I–III, 80 patients who were undergoing supratentorial craniotomy. After the induction of general anesthesia, the ONSD’s were measured by the linear transducer from 3 mm below the globe at PEEP values of 0–5–10 cmH2O. The ONSD were compered between patients with (n = 7) and without midline shift (n = 73) at different PEEP values.ResultsThe increases in ONSD due to increase in PEEP level were determined (p < 0.001). No difference was found in the comparison of ONSD between patients with and without midline shift in different PEEP values (p = 0.329, 0.535, 0.410 respectively). But application of 10 cmH2O PEEP in patients with a midline shift increased the mean ONSD value to 5.73 mm. This value is roughly 0.1 mm higher than the lower limit of the ONSD cutoff value.ConclusionsThe ONSD in adults undergoing supratentorial tumor craniotomy, PEEP values up to 5 cmH2O, appears not to be associated with an ICP increase; however, the ONSD exceeded the cutoff for increased ICP when a PEEP of 10 cmH2O was applied in patients with midline shift.

Clinical case of treatment of true drowning in fresh water

Drowning is the third leading cause of unintentional injury death worldwide. The largest number of victims of drowning falls on the young able- bodied population.Objective. There are no recent intensive care protocols for drowning, it is relevant to formulate guidelines for the treatment of drowning. Clinical observation. A 25-year-old female patient was taken by an ambulance team to the intensive care unit with a directional diagnosis ‘drowning in fresh water’ of three degree of severity. The patient had got on ventilator with closed aspiration system. Emergency bronchoscopy was performed during which 200 ml of fluid aspirated into the lungs was removed. Respiratory support was determined by stepwise increase of the PEEP level and decrease in FiO2 level taking into account respiratory index. Given the development of a pro-inflammatory mediator response, lactatacidosis, hemolysis, hyperhydration, a high risk of infectious complications, it was decided to start extracorporeal treatment early by continuous veno-venous hemodiafiltration and de-escalation of systemic antibacterial therapy with meropenem by prolonged infusion. Against the background of the ongoing treatment, we managed to achieve target respiratory parameters and stabilize central hemodynamic parameters by the end of the first day, prevent the development of renal damage, correct water-electrolyte and metabolic disorders, and avoid severe septic complications. Vasopressor support was discontinued on the 4th day, and on the 5th day the patient was switched to independent breathing. The patient`s stay in the intensive care unit was 6 days.Conclusions. Stepwise respiratory therapy using closed suction systems and urgent bronchoscopy prevent direct damage to the alveoli and ongoing translocation of fluid into the vascular bed. Prescribing broad-spectrum antibiotics prior to the growth of clinical and laboratory signs of infectious lung lesions allows to reduce the risk of severe septic complications with pulmonary destruction parenchyma. Early onset extracorporeal treatment by CVVHDF allows to correct homeostasis disorders, eliminate hypervolemia, prevent the development of acute renal damage as a result of hemolysis.

Pressure-support compared with pressure-controlled ventilation mitigates lung and brain injury in experimental acute ischemic stroke in rats

BackgroundWe aimed to evaluate the pulmonary and cerebral effects of low-tidal volume ventilation in pressure-support (PSV) and pressure-controlled (PCV) modes at two PEEP levels in acute ischemic stroke (AIS).MethodsIn this randomized experimental study, AIS was induced by thermocoagulation in 30 healthy male Wistar rats. After 24 h, AIS animals were randomly assigned to PSV or PCV with VT = 6 mL/kg and PEEP = 2 cmH2O (PSV-PEEP2 and PCV-PEEP2) or PEEP = 5 cmH2O (PSV-PEEP5 and PCV-PEEP5) for 2 h. Lung mechanics, arterial blood gases, and echocardiography were evaluated before and after the experiment. Lungs and brain tissue were removed for histologic and molecular biology analysis. The primary endpoint was diffuse alveolar damage (DAD) score; secondary endpoints included brain histology and brain and lung molecular biology markers.ResultsIn lungs, DAD was lower with PSV-PEEP5 than PCV-PEEP5 (p < 0.001); interleukin (IL)-1β was lower with PSV-PEEP2 than PCV-PEEP2 (p = 0.016) and PSV-PEEP5 than PCV-PEEP5 (p = 0.046); zonula occludens-1 (ZO-1) was lower in PCV-PEEP5 than PCV-PEEP2 (p = 0.042). In brain, necrosis, hemorrhage, neuropil edema, and CD45 + microglia were lower in PSV than PCV animals at PEEP = 2 cmH2O (p = 0.036, p = 0.025, p = 0.018, p = 0.011, respectively) and PEEP = 5 cmH2O (p = 0.003, p = 0.003, p = 0.007, p = 0.003, respectively); IL-1β was lower while ZO-1 was higher in PSV-PEEP2 than PCV-PEEP2 (p = 0.009, p = 0.007, respectively), suggesting blood–brain barrier integrity. Claudin-5 was higher in PSV-PEEP2 than PSV-PEEP5 (p = 0.036).ConclusionIn experimental AIS, PSV compared with PCV reduced lung and brain injury. Lung ZO-1 reduced in PCV with PEEP = 2 versus PEEP = 5 cmH2O, while brain claudin-5 increased in PSV with PEEP = 2 versus PEEP = 5 cmH2O.

Electrical Impedance Tomography during Abdominal Laparoscopic Surgery: A Physiological Pilot Study

Background: Both general anesthesia and pneumoperitoneum insufflation during abdominal laparoscopic surgery can lead to atelectasis and impairment in oxygenation. Setting an appropriate level of external PEEP could reduce the occurrence of atelectasis and induce an improvement in gas exchange. However, in clinical practice, it is common to use a fixed PEEP level (i.e., 5 cmH2O), irrespective of the dynamic respiratory mechanics. We hypothesized setting a PEEP level guided by EIT in order to obtain an improvement in oxygenation and respiratory system compliance in lung-healthy patients than can benefit a personalized approach. Methods: Twelve consecutive patients scheduled for abdominal laparoscopic surgery were enrolled in this prospective study. The EIT Timpel Enlight 1800 was applied to each patient and a dedicated pneumotachograph and a spirometer flow sensor, integrated with EIT, constantly recorded respiratory mechanics. Gas exchange, respiratory mechanics and hemodynamics were recorded at five time points: T0, baseline; T1, after induction; T2, after pneumoperitoneum insufflation; T3, after a recruitment maneuver; and T4, at the end of surgery after desufflation. Results: A titrated mean PEEP of 8 cmH2O applied after a recruitment maneuver was successfully associated with the “best” compliance (58.4 ± 5.43 mL/cmH2O), with a low percentage of collapse (10%), an acceptable level of hyperdistention (0.02%). Pneumoperitoneum insufflation worsened respiratory system compliance, plateau pressure, and driving pressure, which significantly improved after the application of the recruitment maneuver and appropriate PEEP. PaO2 increased from 78.1 ± 9.49 mmHg at T0 to 188 ± 66.7 mmHg at T4 (p &lt; 0.01). Other respiratory parameters remained stable after abdominal desufflation. Hemodynamic parameters remained unchanged throughout the study. Conclusions: EIT, used as a non-invasive intra-operative monitor, enables the rapid assessment of lung volume and regional ventilation changes in patients undergoing laparoscopic surgery and helps to identify the “optimal” PEEP level in the operating theatre, improving ventilation strategies.

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

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

INCIDENCE OF PNEUMOTHORAX IN CASES WITH ARDS REQUIRING PEEP &gt; 10 mmHg

This study aimed to determine the incidence of pneumothorax in patients with ARDS who require PEEP levels higher than ten mmHg. The study was conducted at the Department of Pulmonology and Critical Care, Central Park Teaching Hospital in Lahore, from January 2022 to June 2023. One hundred thirty-eight patients were enrolled in this cross-sectional study, and informed consent was obtained from all patients and their guardians. All patients underwent chest radiography or point of care ultrasound (POCUS) to identify pneumothorax. The results showed that 35 out of 138 patients (25.4%) had pneumothorax, and the mean PEEP value was 11.05±1.05. The study also found that male patients were more commonly affected than female patients (56.5% vs 42.8%). The practical implication of this study is that the diagnosis of pneumothorax is crucial in patients with ARDS, especially in the early stages, as this condition can lead to high mortality rates. The study can help pulmonologists choose better patient treatment options and avoid comorbidities. Conservative management may be recommended to patients if there are no clinical signs or symptoms of a severe condition and if the pneumothorax size is small. In conclusion, this study shows that patients with ARDS requiring PEEP levels higher than ten mmHg are at a higher risk of developing pneumothorax. Thus, early diagnosis and proper management are essential to improve patient outcomes.

Physiological effects of lung-protective ventilation in patients with lung fibrosis and usual interstitial pneumonia pattern versus primary ARDS: a matched-control study

BackgroundAlthough patients with interstitial pneumonia pattern (ILD-UIP) and acute exacerbation (AE) leading to severe acute respiratory failure may require invasive mechanical ventilation (MV), physiological data on lung mechanics during MV are lacking. We aimed at describing the physiological effect of lung-protective ventilation in patients with AE-ILD-UIP compared with primary ARDS.MethodsPartitioned lung and chest wall mechanics were assessed in a series of AE-ILD-UIP patients matched 1:1 with primary ARDS as controls (based on BMI and PaO2/FiO2 ratio). Three PEEP levels (zero = ZEEP, 4–8 cmH2O = PEEPLOW, and titrated to achieve positive end-expiratory transpulmonary pressure PL,EE = PEEPTITRATED) were used for measurements.ResultsTen AE-ILD-UIP patients and 10 matched ARDS were included. In AE-ILD-UIP median PL,EE at ZEEP was − 4.3 [− 7.6– − 2.3] cmH2O and lung elastance (EL) 44 [40–51] cmH2O/L. At PEEPLOW, PL,EE remained negative and EL did not change (p = 0.995) versus ZEEP. At PEEPTITRATED, PL,EE increased to 0.8 [0.3–1.5] cmH2O and EL to 49 [43–59] (p = 0.004 and p < 0.001 compared to ZEEP and PEEPLOW, respectively). ΔPL decreased at PEEPLOW (p = 0.018) and increased at PEEPTITRATED (p = 0.003). In matched ARDS control PEEP titration to obtain a positive PL,EE did not result in significant changes in EL and ΔPL.ConclusionsIn mechanically ventilated AE-ILD-UIP patients, differently than in patients with primary ARDS, PEEP titrated to obtain a positive PL,EE significantly worsened lung mechanics.

The effect intraoperative positive end expiratory pressure and tidal volume on postoperative acute kidney injury after orthopedic surgery.

To test whether higher intraoperative PEEP levels and/or higher TV levels are associated with higher incidence of postoperative AKI within the first postoperative week, in adult patients having orthopedic surgeries under general anesthesia. We conducted a sub analysis of a non-randomized alternating intervention cross over study performed in patients undergoing orthopedic surgery under general anesthesia at Cleveland Clinic, Cleveland, OH. We included four different combinations of PEEP (5 or 8 cm H2 O) and TV (6 or 10 mL/kg of PBW) that alternated each week in the six orthopedic operating rooms. Our primary outcome was postoperative AKI defined by the KDIGO criteria with baseline creatinine as the closest preoperative value to the time of surgery obtained within 30 days and postoperative value as the highest creatinine value within 7 days after surgery. Secondary outcome was the maximum postoperative in-hospital creatinine level within seven postoperative days. A total of 1933 patients were included in the analysis. The incidence of AKI was 6.8% in the study population and similar in high TV versus low TV group and high PEEP versus low PEEP group. Neither TV nor PEEP significantly impacted AKI incidence. The estimated odds ratio of AKI comparing TV = 6 mL/kg to TV = 10 mL/kg was 0.96 (97.5% CI: 0.63, 1.46; p = .811); while the estimated odds ratio of AKI comparing PEEP = 5cm H2 O to PEEP = 8cm H2 O was 0.92 (97.5% CI: 0.60, 1.39; p = .623). No interaction was found between TV and PEEP on AKI. Additionally, neither TV nor PEEP had a significant effect on the seven postoperative day creatinine levels. Higher levels of PEEP or TV during mechanical ventilation in adult patients undergoing orthopedic surgeries under general anesthesia do not increase the odds of developing postoperative AKI within the narrow limits studied.

The intraoperative management of robotic-assisted laparoscopic prostatectomy.

Robotic-assisted laparoscopic radical prostatectomy has become the second most commonly performed robotic surgical procedure worldwide, therefore, anesthesiologists should be aware of the intraoperative pathophysiological consequences. The aim of this narrative review is to report the most recent updates regarding the intraoperative management of anesthesia, ventilation, hemodynamics and central nervous system, during robotic-assisted laparoscopic radical prostatectomy. Surgical innovations and the advent of new technologies make it imperative to optimize the anesthesia management to provide the most holistic approach possible. In addition, an ageing population with an increasing burden of comorbidities requires multifocal attention to reduce the surgical stress. Total intravenous anesthesia (TIVA) and balanced general anesthesia are similar in terms of postoperative complications and hospital stay. Reversal of rocuronium is associated with shorter hospital stay and postanesthesia recovery time. Adequate PEEP levels improve oxygenation and driving pressure, and the use of a single recruitment maneuver after the intubation reduces postoperative pulmonary complications. Restrictive intravenous fluid administration minimizes bladder-urethra anastomosis complications and facial edema. TIVA maintains a better autoregulation compared with balanced general anesthesia. Anesthesiologists should be able to optimize the intraoperative management to improve outcomes.

Electrical Impedance Tomography Identifies Evolution of Regional Perfusion in a Porcine Model of Acute Respiratory Distress Syndrome.

Bedside electrical impedance tomography could be useful to visualize evolving pulmonary perfusion distributions when acute respiratory distress syndrome worsens or in response to ventilatory and positional therapies. In experimental acute respiratory distress syndrome, this study evaluated the agreement of electrical impedance tomography and dynamic contrast-enhanced computed tomography perfusion distributions at two injury time points and in response to increased positive end-expiratory pressure (PEEP) and prone position. Eleven mechanically ventilated (VT 8 ml · kg-1) Yorkshire pigs (five male, six female) received bronchial hydrochloric acid (3.5 ml · kg-1) to invoke lung injury. Electrical impedance tomography and computed tomography perfusion images were obtained at 2 h (early injury) and 24 h (late injury) after injury in supine position with PEEP 5 and 10 cm H2O. In eight animals, electrical impedance tomography and computed tomography perfusion imaging were also conducted in the prone position. Electrical impedance tomography perfusion (QEIT) and computed tomography perfusion (QCT) values (as percentages of image total) were compared in eight vertical regions across injury stages, levels of PEEP, and body positions using mixed-effects linear regression. The primary outcome was agreement between QEIT and QCT, defined using limits of agreement and Pearson correlation coefficient. Pao2/Fio2 decreased over the course of the experiment (healthy to early injury, -253 [95% CI, -317 to -189]; early to late injury, -88 [95% CI, -151 to -24]). The limits of agreement between QEIT and QCT were -4.66% and 4.73% for the middle 50% quantile of average regional perfusion, and the correlation coefficient was 0.88 (95% CI, 0.86 to 0.90]; P < 0.001). Electrical impedance tomography and computed tomography showed similar perfusion redistributions over injury stages and in response to increased PEEP. QEIT redistributions after positional therapy underestimated QCT in ventral regions and overestimated QCT in dorsal regions. Electrical impedance tomography closely approximated computed tomography perfusion measures in experimental acute respiratory distress syndrome, in the supine position, over injury progression and with increased PEEP. Further validation is needed to determine the accuracy of electrical impedance tomography in measuring perfusion redistributions after positional changes.