Predictive role of regional thigh tissue oxygen saturation monitoring during cardiopulmonary bypass in lung injury after cardiac surgery

Acute respiratory distress syndrome (ARDS) is a serious complication following cardiac surgery mainly associated with the use of cardiopulmonary bypass (CPB), which could increase the risk of mortality and morbidity. This study investigated the association of regional oxygen saturation (rSO2) during CPB with postoperative outcomes, including respiratory function. Patients who underwent cardiac surgery with CPB from 2015 to 2019 were included. Near-infrared spectroscopy was used to monitor rSO2 at the forehead, abdomen, and thighs throughout the surgery. Postoperative markers associated with CPB were assessed for correlations with PaO2/FiO2 (P/F) ratios at intensive care unit (ICU) admission. Postoperative lung injury (LI) was defined as moderate or severe ARDS based on the Berlin criteria, and its incidence was 29.9% (20/67). On multiple regression analysis, the following were associated with P/F ratios at ICU admission: vasoactive-inotropic scores at CPB induction (P = 0.03), thigh rSO2 values during CPB (P = 0.04), and body surface area (P < 0.001). A thigh rSO2 of 71% during CPB was significantly predictive of postoperative LI with an area under the curve of 0.71 (P = 0.03), sensitivity of 0.70, and specificity of 0.68. Patients with postoperative LI had longer ventilation time and ICU stays. Thigh rSO2 values during CPB were a potential predictor of postoperative pulmonary outcomes.

Association between cardiopulmonary bypass time and mortality among patients with acute respiratory distress syndrome after cardiac surgery

BACKGROUND

Cardiopulmonary bypass (CPB) can lead to lung injury and even acute respiratory distress syndrome (ARDS) through triggering systemic inflammatory response. The objective of this study was to investigate the impact of CPB time on clinical outcomes in patients with ARDS after cardiac surgery.

METHODS

Totally, patients with ARDS after cardiac surgery in Beijing Anzhen Hospital from January 2005 to December 2015 were retrospectively included and were further divided into three groups according to the median time of CPB. The primary endpoints were the ICU mortality and in-hospital mortality, and ICU and hospital stay. Restricted cubic spline (RCS), logistic regression, cox regression model, and receiver operating characteristic (ROC) curve were adopted to explore the relationship between CPB time and clinical endpoints.

RESULTS

A total of 54,217 patients underwent cardiac surgery during the above period, of whom 210 patients developed ARDS after surgery and were finally included. The ICU mortality and in-hospital mortality were 21.0% and 41.9% in all ARDS patients after cardiac surgery respectively. Patients with long CPB time (CPB time ≥ 173 min) had longer length of ICU stay (P = 0.011), higher ICU (P < 0.001) mortality and in-hospital(P = 0.002) mortality compared with non-CPB patients (CPB = 0). For each ten minutes increment in CPB time, the hazards of a worse outcome increased by 13.3% for ICU mortality and 9.3% for in-hospital mortality after adjusting for potential factors. ROC curves showed CPB time presented more satisfactory power to predict mortality compared with APCHEII score. The optimal cut-off value of CPB time were 160.5 min for ICU mortality and in-hospital mortality.

CONCLUSIONS

Our findings demonstrated the significant prognostic value of CPB time in patients with ARDS after cardiac surgery. Longer time of CPB was associated with poorer clinical outcomes, and could be served as an indicator to predict short-term mortality in patients with ARDS after cardiac surgery.

Postoperative acute respiratory distress syndrome in randomized controlled trials

BACKGROUND

Acute respiratory distress syndrome is a potentially fatal postoperative complication. We aimed to estimate temporal trends of the representation of patients with postoperative acute respiratory distress syndrome in clinical trials, determine their distinct clinical features, and identify predictors of mortality.

METHODS

This is a secondary analysis of 7 randomized controlled clinical trials conducted by the Acute Respiratory Distress Syndrome Network and the Clinical Trials Network for the Prevention and Early Treatment of Acute Lung Injury. Patients with acute respiratory distress syndrome were classified into a postoperative acute respiratory distress syndrome group (ie, patients who had undergone elective surgery in the immediate period before trial enrollment) and a non-postoperative acute respiratory distress syndrome group.

RESULTS

Out of 5,316 patients with acute respiratory distress syndrome, 256 (4.8%) had postoperative acute respiratory distress syndrome. Representation of postoperative acute respiratory distress syndrome in trials gradually declined from 2000 to 2011, but it remained stable afterward at 2.7%. Postoperative acute respiratory distress syndrome was associated with lower 90-day mortality (24.6% vs 30.9%, P = .032) than non-postoperative acute respiratory distress syndrome, even after adjusting for age, acute respiratory distress syndrome severity, usage of vasopressors at baseline, and the study publication year (hazard ratio 0.63, 95% confidence interval 0.49-0.82). Age (odds ratio 1.07, 95% confidence interval 1.04-1.09), immunosuppression (odds ratio 4.12, 95% confidence interval 1.43-11.86), and positive fluid balance (odds ratio 1.09, 95% confidence interval 1.04-1.14) were associated with 90-day mortality among patients with postoperative acute respiratory distress syndrome.

CONCLUSION

Representation of postoperative acute respiratory distress syndrome in trials of the Acute Respiratory Distress Syndrome Network and the Clinical Trials Network for the Prevention and Early Treatment of Acute Lung Injury gradually declined from 2000 to 2011 but remained stable afterward. Postoperative acute respiratory distress syndrome was associated with lower mortality than non-postoperative acute respiratory distress syndrome. These findings may put both temporal trends and the prognosis of postoperative acute respiratory distress syndrome in perspective. Also, positive fluid balance was associated with the mortality of patients with postoperative acute respiratory distress syndrome.

Rescue high-frequency oscillatory ventilation combined with intermittent mandatory ventilation for infants with acute respiratory distress syndrome after congenital heart surgery

BACKGROUND

This study aimed to evaluate the efficacy and safety of high-frequency oscillation ventilation combined with intermittent mandatory ventilation in infants with acute respiratory distress syndrome after congenital heart surgery.

METHODS

We retrospectively analysed the clinical data of 32 infants who were ventilated due to acute respiratory distress syndrome after congenital heart surgery between January, 2020 and January, 2022. We adopted high-frequency oscillation ventilation combined with intermittent mandatory ventilation as the rescue ventilation mode for infants who were failing conventional mechanical ventilation.

RESULTS

After rescue high-frequency oscillation ventilation combined with intermittent mandatory ventilation, the dynamic compliance (Cdyn), PaO2 and PaO2/FiO2 ratio of the infants improved compared with conventional mechanical ventilation (p < 0.05). Moreover, high-frequency oscillation ventilation combined with intermittent mandatory ventilation resulted in a significant decrease in arterial-alveolar oxygen difference (AaDO2), FiO2, and oxygenation index (p < 0.05). No significant effect on haemodynamic parameters was observed. Moreover, no serious complications occurred in the two groups.

CONCLUSION

Rescue high-frequency oscillation ventilation combined with intermittent mandatory ventilation significantly improved oxygenation in infants who failed conventional mechanical ventilation for acute respiratory distress syndrome after congenital heart surgery. Thus, this strategy is considered safe and feasible. However, further studies must be conducted to confirm the efficacy and safety of high-frequency oscillation ventilation combined with intermittent mandatory ventilation as a rescue perioperative respiratory support strategy for CHD.

Subversion of autophagy machinery and organelle-specific autophagy by SARS-CoV-2 and coronaviruses

As a new emerging severe coronavirus, the knowledge on the SARS-CoV-2 and COVID-19 remains very limited, whereas many concepts can be learned from the homologous coronaviruses. Macroautophagy/autophagy is finely regulated by SARS-CoV-2 infection and plays important roles in SARS-CoV-2 infection and pathogenesis. This review will explore the subversion and mechanism of the autophagy-related machinery, vacuoles and organelle-specific autophagy during infection of SARS-CoV-2 and coronaviruses to provide meaningful insights into the autophagy-related therapeutic strategies for infectious diseases of SARS-CoV-2 and coronaviruses.

Short-term prone positioning for severe acute respiratory distress syndrome after cardiopulmonary bypass: A case report and literature review

BACKGROUND

Aortic dissection is a complex and dangerous cardiovascular disease, with many complications in the perioperative period, including severe acute respiratory distress syndrome (ARDS), which affects prognosis and increases mortality. Despite the effect of prone positioning (PP) in improving oxygenation in patients with severe ARDS, reports about PP early after cardiac surgery are few and such an option may be an issue in cardiac surgery patients because of the recent sternotomy.

CASE SUMMARY

A 40-year-old male patient diagnosed with acute type A aortic dissection on October 22, 2021 underwent ascending artery replacement plus total aortic arch replacement plus stent elephant trunk implantation under cardiopulmonary bypass. Unfortunately, he developed ARDS on postoperative day 1. Despite comprehensive treatment with aggressive pulmonary protective ventilation, fluid management with continuous renal replacement therapy, the condition continued to deteriorate and rapidly progressed to severe ARDS with a minimum oxygenation index of 51. We are ready to implement salvage therapy, including PP and extracorporeal membrane oxygenation (ECMO). Due to the large amount of pericardial mediastinal and thoracic drainage after thoracotomy, ECMO may result in massive postoperative bleeding. Prolonged prone ventilation is often inappropriate after thoracotomy. Therefore, we chose short-term PP for < 6 h. Finally, the oxygenation index greatly improved and the diffuse exudation in both lungs of the patient was significantly reduced with short-term prone positioning.

CONCLUSION

Intermittent short-term PP can improve early postoperative severe ARDS after acute aortic dissection.

Serum level of calpains product as a novel biomarker of acute lung injury following cardiopulmonary bypass

OBJECTIVE

The aim of this study was to test the hypothesis whether serum level of calpains could become a meaningful biomarker for diagnosis of acute lung injury (ALI) in clinical after cardiac surgery using cardiopulmonary bypass (CPB) technology.

METHODS AND RESULTS

Seventy consecutive adults underwent cardiac surgery with CPB were included in this prospective study. Based on the American-European Consensus Criteria (AECC), these patients were divided into ALI (n = 20, 28.57%) and non-ALI (n = 50, 71.43%) groups. Serum level of calpains in terms of calpains' activity which was expressed as relative fluorescence unit (RFU) per microliter and measured at beginning of CPB (baseline), 1 h during CPB, end of CPB as well as 1, 12, and 24 h after CPB. Difference of serum level of calpains between two groups first appeared at the end of CPB and remained different at subsequent test points. Univariate and multivariate logistic regression analysis indicated that serum level of calpains 1 h after CPB was an independent predictor for postoperative ALI (OR 1.011, 95% CI 1.001, 1.021, p = 0.033) and correlated with a lower PaO₂/FiO₂ ratio in the first 2 days (The first day: r = -0.389, p < 0.001 and the second day: r = -0.320, p = 0.007) as well as longer mechanical ventilation time (r = 0.440, p < 0.001), intensive care unit (ICU) length of stay (LOS) (r = 0.419, p < 0.001) and hospital LOS (r = 0.297, p = 0.013).

CONCLUSION

Elevated serum level of calpains correlate with impaired lung function and poor clinical outcomes, indicating serum level of calpains could act as a potential biomarker for postoperative ALI following CPB in adults.

CLINICAL TRIAL REGISTRATION

[https://clinicaltrials.gov/show/NCT05610475], identifier [NCT05610475].

Prone positioning in extubated patients with hypoxemic respiratory failure after cardiac surgery: A retrospective study

BACKGROUND

Hypoxemic respiratory failure is a serious complication that can occur at any stage after cardiac surgery. Prone positioning (PP) is safe and effective for patients receiving invasive ventilation after hypoxemic respiratory failure; however, few related studies have focused on its use with extubated cardiac surgery patients. Researchers recently reported beneficial effects of PP for hypoxemic patients with COVID-19 and those with moderate ARDS (acute respiratory distress syndrome,ARDS). PP may also improve oxygenation in extubated cardiac surgery patients.

OBJECTIVE

In this study, we aimed to assess the safety and effectiveness of PP in extubated cardiac surgery patients to determine whether PP can improve oxygenation and respiratory status or reduce secondary intubation.

METHODS

We reviewed our institutional database between August 2018 and August 2020 and identified 22 cardiac surgery patients who had undergone PP for hypoxemic respiratory failure after extubation. From the medical and nursing records, we extracted the following data recorded before PP, during PP, and after PP for each patient, arterial blood gas analyses, hemodynamic records, laboratory reports, and respiratory function training records.

RESULTS

Twenty-two extubated patients underwent 74 PP. Each patient underwent a median of 3.5 (2-5) procedures, and the median duration of each PP was 10 h. PP was implemented on the 4.5th postoperative day (median). All patients were discharged from the hospital, and none died. No complications were observed. PP improved the P/F ratio (182.65 ± 60.17, 301.53 ± 61.31, and 246.76 ± 65.68, before PP, during PP, and after PP, respectively, p < 0.001). Additionally, the respiratory rate, Forced Vital Capacity (FVC) and PaCO2 also improved, and hemodynamics showed no significant change.

CONCLUSION

PP may be effective and safe for treating patients who are extubated following cardiac surgery with hypoxemic respiratory failure. For these patients, PP is associated with oxygenation and respiratory condition improvements and low secondary intubation rates.

Acute Respiratory Distress Syndrome in the Perioperative Period of Cardiac Surgery: Predictors, Diagnosis, Prognosis, Management Options, and Future Directions

Acute respiratory distress syndrome (ARDS) after cardiac surgery is reported with a widely variable incidence (from 0.4%-8.1%). Cardiac surgery patients usually are affected by several comorbidities, and the development of ARDS significantly affects their prognosis. Herein, evidence regarding the current knowledge in the field of ARDS in cardiac surgery is summarized and is followed by a discussion on therapeutic strategies, with consideration of the peculiar aspects of ARDS after cardiac surgery. Prevention of lung injury during and after cardiac surgery remains pivotal. Blood product transfusions should be limited to minimize the risk, among others, of lung injury. Open lung ventilation strategy (ventilation during cardiopulmonary bypass, recruitment maneuvers, and the use of moderate positive end-expiratory pressure) has not shown clear benefits on clinical outcomes. Clinicians in the intraoperative and postoperative ventilatory settings carefully should consider the effect of mechanical ventilation on cardiac function (in particular the right ventricle). Driving pressure should be kept as low as possible, with low tidal volumes (on predicted body weight) and optimal positive end-expiratory pressure. Regarding the therapeutic options, management of ARDS after cardiac surgery challenges the common approach. For instance, prone positioning may not be easily applicable after cardiac surgery. In patients who develop ARDS after cardiac surgery, extracorporeal techniques may be a valid choice in experienced hands. The use of neuromuscular blockade and inhaled nitric oxide can be considered on a case-by-case basis, whereas the use of aggressive lung recruitment and oscillatory ventilation should be discouraged.

Role of Intensified Lung Physiotherapy Bundle on the Occurrence of Pneumonia After Cardiac Surgery

Objective

The role of intensified lung physiotherapy bundle after cardiac surgery was investigated.

Methods

A before- and after-surgery comparison was conducted between the study from January 1, 2018 to December 31, 2019 (control group), when traditional lung physiotherapy bundle was used, and from January 1, 2020 to May 1, 2021 (study group), when the intensified bundle was used. The baseline data, clinical features, incidence of postoperative pneumonia, and prognoses of all the enrolled cardiac surgery patients were analyzed.

Results

In accordance with the study criteria, 358 patients were enrolled. The incidence rate of postoperative pneumonia was significantly lower in the study group than in the control group (14.2 vs. 22.7%, P = 0.037), as was in-hospital mortality (1.5 vs. 5.2%, P = 0.043). Patients receiving the intensified lung physiotherapy bundle had much shorter mechanical ventilation time (92 vs. 144 h, P < 0.0001), much shorter intensive care unit (ICU) stay (5 vs. 7 days, P < 0.001), and much shorter hospital stay (17 vs. 18.5 days, P = 0.022). The intensified lung physiotherapy bundle was an independent protective factor enabling the reduced occurrence of pneumonia (P = 0.007). On univariate analysis, this bundle significantly improved in-hospital mortality (P = 0.043).

Conclusions

Our intensified lung physiotherapy bundle potentially reduces the rate of postoperative pneumonia after cardiac surgery. This bundle might also be adopted as a suitable reference guide for the prevention of other postoperative pulmonary complications.

Nomogram Models to Predict Postoperative Hyperlactatemia in Patients Undergoing Elective Cardiac Surgery

Objectives: Postoperative hyperlactatemia (POHL) is common in patients undergoing cardiac surgery and is associated with poor outcomes. The purpose of this study was to develop and validate two predictive models for POHL in patients undergoing elective cardiac surgery (ECS).

Methods: We conducted a multicenter retrospective study enrolling 13,454 adult patients who underwent ECS. All patients involved in the analysis were randomly assigned to a training set and a validation set. Univariate and multivariate analyses were performed to identify risk factors for POHL in the training cohort. Based on these independent predictors, the nomograms were constructed to predict the probability of POHL and were validated in the validation cohort.

Results: A total of 1,430 patients (10.6%) developed POHL after ECS. Age, preoperative left ventricular ejection fraction, renal insufficiency, cardiac surgery history, intraoperative red blood cell transfusion, and cardiopulmonary bypass time were independent predictors and were used to construct a full nomogram. The second nomogram was constructed comprising only the preoperative factors. Both models showed good predictive ability, calibration, and clinical utility. According to the predicted probabilities, four risk groups were defined as very low risk (<0.05), low risk (0.05–0.1), medium risk (0.1–0.3), and high risk groups (>0.3), corresponding to scores of ≤ 180 points, 181–202 points, 203–239 points, and >239 points on the full nomogram, respectively.

Conclusions: We developed and validated two nomogram models to predict POHL in patients undergoing ECS. The nomograms may have clinical utility in risk estimation, risk stratification, and targeted interventions.

Global Pandemic as a Result of Severe Acute Respiratory Syndrome Coronavirus 2 Outbreak: A Biomedical Perspective

In December 2019, a novel coronavirus had emerged in Wuhan city, China that led to an outbreak resulting in a global pandemic, taking thousands of lives. The infectious virus was later classified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Individuals infected by this novel virus initially exhibit nonspecific symptoms such as dry cough, fever, dizziness and many more bodily complications. From the “public health emergency of international concern” declaration by the World Health Organisation (WHO), several countries have taken steps in controlling the transmission and many researchers share their knowledge on the SARS-COV-2 characteristics and viral life cycle, that may aid in pharmaceutical and biopharmaceutical companies to develop SARS-CoV-2 vaccine and antiviral drugs that interfere with the viral life cycle. In this literature review the origin, classification, aetiology, life cycle, clinical manifestations, laboratory diagnosis and treatment are all reviewed.

The Impact of Comorbidities on the Outcomes of Egyptian COVID-19 Patients: A Follow-Up Study

Objectives

This study evaluated the clinical manifestation of COVID-19 and adverse outcomes in patients with comorbidities (outcome: death).

Methods

A comparative follow-up investigation involving 148 confirmed cases of COVID-19 was performed for a month (between April and May 2020) at Qaha Hospital to describe the clinical characteristics and outcomes resulting from comorbidities. Participants were divided into two clusters based on the presence of comorbidities. Group I comprised cases with comorbidities, and Group II included subjects without comorbidity. Survival distributions were outlined for the group with comorbidities after the follow-up period.

Results

Fever (74.3%), headache (78.4%), cough (78.4%), sore throat (78.4%), fatigue (78.4%), and shortness of breath (86.5%) were the most prevalent symptoms observed in COVID-19 patients with comorbidities. Such patients also suffered from acute respiratory distress syndrome (37.8%) and pneumonia three times more than patients without comorbidities. The survival distributions were statistically significant (chi-square = 26.06, p ≤ 0.001).

Conclusion

Multiple comorbidities in COVID-19 patients are linked to severe clinical symptoms, disease complications, and critical disease progression. The presence of one or more comorbidities worsened the survival rate of patients.

Lung Injury After Neonatal Congenital Cardiac Surgery Is Mild and Modifiable by Corticosteroids

OBJECTIVES

The present study was performed to determine whether lung injury manifests as lung edema in neonates after congenital cardiac surgery and whether a stress-dose corticosteroid (SDC) regimen attenuates postoperative lung injury in neonates after congenital cardiac surgery.

DESIGN

A supplementary report of a randomized, double-blinded, placebo-controlled clinical trial.

SETTING

A pediatric tertiary university hospital.

PARTICIPANTS

Forty neonates (age ≤28 days) undergoing congenital cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

After anesthesia induction, patients were assigned randomly to receive intravenously either 2 mg/kg methylprednisolone or placebo b, which was followed by hydrocortisone or placebo bolus six hours after weaning from CPB for five days as follows: 0.2 mg/kg/h for 48 hours, 0.1 mg/kg/h for the next 48 hours, and 0.05 mg/kg/h for the following 24 hours.

MEASUREMENTS AND MAIN RESULTS

The chest radiography lung edema score was lower in the SDC than in the placebo group on the first postoperative day (POD one) (p = 0.03) and on PODs two and three (p = 0.03). Furthermore, a modest increase in the edema score of 0.9 was noted in the placebo group, whereas the edema score remained at the preoperative level in the SDC group. Postoperative dynamic respiratory system compliance was higher in the SDC group until POD three (p < 0.01). However, postoperative oxygenation; length of mechanical ventilation; and tracheal aspirate biomarkers of inflammation and oxidative stress, namely interleukin-6, interleukin-8, resistin, and 8-isoprostane, showed no differences between the groups.

CONCLUSIONS

The SDC regimen reduced the development of mild and likely clinically insignificant radiographic lung edema and improved postoperative dynamic respiratory system compliance without adverse events, but it failed to improve postoperative oxygenation and length of mechanical ventilation.

Coronavirus disease-2019 and its current scenario – A review

Coronaviruses are enveloped non-segmented positive-sense RNA viruses belonging to the family Coronaviridae. The human coronavirus infections are mild; the epidemics of the two β-coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) have caused more than ten thousand cumulative cases in the past twodecades. There is a new public health crisis threatening the world with the emergence and spread of 2019 novel coronavirus (2019-nCoV). The virus originated in bats and was transmitted to humans through yet unknown intermediary animals in Wuhan, Hubei province in China during the month of December 2019. Till date around 7,823,289 reported cases of coronavirus disease 2019 (COVID-2019) and 431,541 reported deaths till date. The disease is transmitted by inhalation or contact with infected droplets with incubation period of 2–14 days. The symptoms are usually fever, sore throat, dry cough, breathlessness, fatigue while many people are asymptomatic. Coronavirus (2019-nCoV) may progress to pneumonia, acute respiratory distress syndrome (ARDS) and can cause multi-organ dysfunction. Currently diagnosis is done by demonstration of the virus in respiratory secretions by special molecular tests like real-time reverse-transcription–polymerase-chain-reaction (RT-PCR), Radiological examinations (chest CT). Common laboratory tests like white cell counts and C-reactive protein (CRP) and measure symptoms can be used as preliminary screening at large scale after lock down the area or country. Treatment is essentially supportive; role of antiviral agents is yet to be established. It is paramount to implement infection control practices by infection source controlling, transmission route blocking, and susceptible population protection. Early preventive measures can be home isolation of suspected cases and those with mild illnesses and strict infection control measures at hospitals that include contact and droplet precautions. The worldwide impact of this Coronavirus new epidemic is yet uncertain.

Coronavirus disease 2019 (COVID-19): Insights into the recent trends and the role of the primary care in diabetic patients

Diseases with viral etiology continue to emerge in the last years and may represent serious problems that affect various aspects of life. Coronaviruses are a large family of RNA viruses that cause illness affecting the respiratory tract ranging from common cold to severe respiratory distress syndrome. In the last weeks of 2019, enormous cases of unexplained pneumonia were reported in China. Few days later, a novel type of coronavirus was identified as the causative agent of these cases and the disease was named as coronavirus disease 2019 (COVID-19) by the World Health Organization. The disease was rapidly spreading in China and all over the world and now it is considered as pandemic catastrophe. It can be transmitted from animals to human and from human to human. Diabetes mellitus may represent a potential risk factor for the development of COVID-19, possibly due to the relative state of immunosuppression frequently encountered in diabetic patients. This review sheds light on COVID-19 based on the currently available data with reference to the role of the primary care in diabetic patients.

PEEP guided by electrical impedance tomography during one-lung ventilation in elderly patients undergoing thoracoscopic surgery

Background

To examine the influence of positive end-expiratory pressure (PEEP) settings on lung mechanics and oxygenation in elderly patients undergoing thoracoscopic surgery.

Methods

One hundred patients aged >65 years were randomly allocated into either the PEEP₅ or the electrical impedance tomography (EIT) group (PEEP_EIT). Each group underwent volume-controlled ventilation (tidal volume 6 mL/kg predicted body weight) with the PEEP either fixed at 5 cmH₂O or set at an individualized EIT setting. The primary endpoint was the ratio of the arterial oxygen partial pressure to the fractional inspired oxygen (PaO₂/FiO₂). The secondary endpoints included the driving pressure, and dynamic respiratory system compliance (C_dyn). Other outcomes, such as the mean airway pressure (P_mean), mean arterial pressure (MAP), lung complications and the length of hospital stay were explored.

Results

The optimal PEEP set by EIT was significantly higher (range from 9-13 cmH₂O) than the fixed PEEP. PaO₂/FiO₂ was 47 mmHg higher (95% CI: 7-86 mmHg; P=0.021), C_dyn was 4.3 mL/cmH₂O higher (95% CI: 2.1-6.7 cmH₂O; P<0.001), and the driving pressure was 3.7 cmH₂O lower (95% CI: 2.2-5.1 mmH₂O; P<0.001) at 0.5 h during one-lung ventilation (OLV) in the PEEP_EIT group than in the PEEP₅ group. At 1 h during OLV, PaO₂/FiO₂ was 93 mmHg higher (95% CI: 58-128 mmHg; P<0.001), C_dyn was 4.4 mL/cmH₂O higher (95% CI: 1.9-6.9 mL/cmH₂O; P=0.001), and the driving pressure was 4.9 cmH₂O lower (95% CI: 3.8-6.1 cmH₂O; P<0.001) in the PEEP_EIT group than in the PEEP₅ group. PaO₂/FiO₂ was 107 mmHg higher (95% CI: 56-158 mmHg; P<0.001) in the PEEP_EIT group than in the PEEP₅ group during double-lung ventilation at the end of surgery.

Conclusions

PEEP values determined with EIT effectively improved oxygenation and lung mechanics during one lung ventilation in elderly patients undergoing thoracoscopic surgery.