Electrical Impedance Tomography-based Ventilation Patterns in Patients after Major Surgery.

Rationale: General anesthesia and mechanical ventilation have negative impacts on the respiratory system, causing heterogeneous distribution of lung aeration, but little is known about the ventilation patterns of postoperative patients and their association with clinical outcomes. Objectives: To clarify the phenotypes of ventilation patterns along a gravitational direction after surgery by using electrical impedance tomography (EIT) and to evaluate their association with postoperative pulmonary complications (PPCs) and other relevant clinical outcomes. Methods: Adult postoperative patients at high risk for PPCs, receiving mechanical ventilation on ICU admission (N = 128), were prospectively enrolled between November 18, 2021 and July 18, 2022. PPCs were prospectively scored until hospital discharge, and their association with phenotypes of ventilation patterns was studied. The secondary outcomes were the times to wean from mechanical ventilation and oxygen use and the length of ICU stay. Measurements and Main Results: Three phenotypes of ventilation patterns were revealed by EIT: phenotype 1 (32% [n = 41], a predominance of ventral ventilation), phenotype 2 (41% [n = 52], homogeneous ventilation), and phenotype 3 (27% [n = 35], a predominance of dorsal ventilation). The median PPC score was higher in phenotype 1 and phenotype 3 than in phenotype 2. The median time to wean from mechanical ventilation was longer in phenotype 1 versus phenotype 2. The median duration of ICU stay was longer in phenotype 1 versus phenotype 2. The median time to wean from oxygen use was longer in phenotype 1 and phenotype 3 than in phenotype 2. Conclusions: Inhomogeneous ventilation patterns revealed by EIT on ICU admission were associated with PPCs, delayed weaning from mechanical ventilation and oxygen use, and a longer ICU stay.

Time definition of reintubation most relevant to patient outcomes in critically ill patients: a multicenter cohort study.

BACKGROUND: Reintubation is a common complication in critically ill patients requiring mechanical ventilation. Although reintubation has been demonstrated to be associated with patient outcomes, its time definition varies widely among guidelines and in the literature. This study aimed to determine the association between reintubation and patient outcomes as well as the consequences of the time elapsed between extubation and reintubation on patient outcomes. METHODS: This was a multicenter retrospective cohort study of critically ill patients conducted between April 2015 and March 2021. Adult patients who underwent mechanical ventilation and extubation in intensive care units (ICUs) were investigated utilizing the Japanese Intensive Care PAtient Database. The primary and secondary outcomes were in-hospital and ICU mortality. The association between reintubation and clinical outcomes was studied using Cox proportional hazards analysis. Among the patients who underwent reintubation, a Cox proportional hazard analysis was conducted to evaluate patient outcomes according to the number of days from extubation to reintubation. RESULTS: Overall, 184,705 patients in 75 ICUs were screened, and 1849 patients underwent reintubation among 48,082 extubated patients. After adjustment for potential confounders, multivariable analysis revealed a significant association between reintubation and increased in-hospital and ICU mortality (adjusted hazard ratio [HR] 1.520, 95% confidence interval [CI] 1.359-1.700, and adjusted HR 1.325, 95% CI 1.076-1.633, respectively). Among the reintubated patients, 1037 (56.1%) were reintubated within 24 h after extubation, 418 (22.6%) at 24-48 h, 198 (10.7%) at 48-72 h, 111 (6.0%) at 72-96 h, and 85 (4.6%) at 96-120 h. Multivariable Cox proportional hazard analysis showed that in-hospital and ICU mortality was highest in patients reintubated at 72-96 h (adjusted HR 1.528, 95% CI 1.062-2.197, and adjusted HR 1.334, 95% CI 0.756-2.352, respectively; referenced to reintubation within 24 h). CONCLUSIONS: Reintubation was associated with a significant increase in in-hospital and ICU mortality. The highest mortality rates were observed in patients who were reintubated between 72 and 96 h after extubation. Further studies are warranted for the optimal observation of extubated patients in clinical practice and to strengthen the evidence for mechanical ventilation.

Personalized ventilatory strategy based on lung recruitablity in COVID-19-associated acute respiratory distress syndrome: a prospective clinical study.

BACKGROUND: Heterogeneity is an inherent nature of ARDS. Recruitment-to-inflation ratio has been developed to identify the patients who has lung recruitablity. This technique might be useful to identify the patients that match specific interventions, such as higher positive end-expiratory pressure (PEEP) or prone position or both. We aimed to evaluate the physiological effects of PEEP and body position on lung mechanics and regional lung inflation in COVID-19-associated ARDS and to propose the optimal ventilatory strategy based on recruitment-to-inflation ratio. METHODS: Patients with COVID-19-associated ARDS were consecutively enrolled. Lung recruitablity (recruitment-to-inflation ratio) and regional lung inflation (electrical impedance tomography [EIT]) were measured with a combination of body position (supine or prone) and PEEP (low 5 cmH2O or high 15 cmH2O). The utility of recruitment-to-inflation ratio to predict responses to PEEP were examined with EIT. RESULTS: Forty-three patients were included. Recruitment-to-inflation ratio was 0.68 (IQR 0.52-0.84), separating high recruiter versus low recruiter. Oxygenation was the same between two groups. In high recruiter, a combination of high PEEP with prone position achieved the highest oxygenation and less dependent silent spaces in EIT (vs. low PEEP in both positions) without increasing non-dependent silent spaces in EIT. In low recruiter, low PEEP in prone position resulted in better oxygenation (vs. both PEEPs in supine position), less dependent silent spaces (vs. low PEEP in supine position) and less non-dependent silent spaces (vs. high PEEP in both positions). Recruitment-to-inflation ratio was positively correlated with the improvement in oxygenation and respiratory system compliance, the decrease in dependent silent spaces, and was inversely correlated with the increase in non-dependent silent spaces, when applying high PEEP. CONCLUSIONS: Recruitment-to-inflation ratio may be useful to personalize PEEP in COVID-19-associated ARDS. Higher PEEP in prone position and lower PEEP in prone position decreased the amount of dependent silent spaces (suggesting lung collapse) without increasing the amount of non-dependent silent spaces (suggesting overinflation) in high recruiter and in low recruiter, respectively.

Positive end-expiratory pressure and prone position alter the capacity of force generation from diaphragm in acute respiratory distress syndrome: an animal experiment.

BACKGROUND: Spontaneous breathing potentially injures lungs and diaphragm when spontaneous effort is vigorous in acute respiratory distress syndrome (ARDS) while immobility also has risks of Intensive Care Unit (ICU) acquired weakness and diaphragm atrophy. Thus, ventilatory strategy to mitigate strong spontaneous effort should be promptly established without a systemic use of neuromuscular blocking agent. Here, we investigated the impacts of positive end-expiratory pressure (PEEP) and body position on the capacity of force generation from diaphragm following bilateral phrenic nerve stimulations in a rabbit ARDS model. METHODS: Using lung-injured rabbits, we measured 1) transdiaphragmatic pressure by bilateral phrenic nerve stimulation and 2) end-expiratory lung volume using computed tomography, under two different levels of PEEP (high, low) and body positions (supine, prone). RESULTS: Overall, transdiaphragmatic pressure was the highest at low PEEP in supine position and the lowest at high PEEP in prone position. Compared to values in low PEEP + supine, transdiaphragmatic pressure was significantly reduced by either prone alone (the same PEEP) or increasing PEEP alone (the same position) or both combinations. End-expiratory lung volume was significantly increased with increasing PEEP in both positions, but it was not altered by body position. INTERPRETATION: The capacity of force generation from diaphragm was modulated by PEEP and body position during mechanical ventilation in ARDS. Higher PEEP or prone position per se or both was effective to decrease the force generation from diaphragm.

Individualized ventilatory management in patients with COVID-19-associated acute respiratory distress syndrome.

Due to the coronavirus disease 2019 pandemic, the number of coronavirus disease 2019-associated acute respiratory distress syndrome is rapidly increasing. The heterogeneity of coronavirus disease 2019-associated acute respiratory distress syndrome contributes to the complexity of managing patients. Here we described two patients with coronavirus disease 2019-associated acute respiratory distress syndrome showing that the bedside physiological approach including careful evaluation of respiratory system mechanics and visualization of ventilation with electrical impedance tomography was useful to individualize ventilatory management.

Association Between Post-procedure Intracardiac Pressures and the Use of Temporary Epicardial Pacing Wires After Pediatric Cardiac Surgery.

The indications for using temporary epicardial pacing wires after pediatric cardiac surgery remain unclear. Post-procedure intracardiac pressure is valuable for detecting circulatory disturbances and residual lesions. This study aimed to examine the association between post-procedure intracardiac pressures and the use of temporary epicardial pacing wires. We performed a retrospective, case-control study at the pediatric intensive care unit of an urban regional tertiary hospital that included patients who had undergone congenital heart surgery between January 2015 and December 2016. We measured post-procedure intracardiac pressures, and data regarding baseline characteristics, procedures performed, and intraoperative variables were collected as covariates. Of the 186 included patients, 34 (18.3%) were treated using temporary epicardial pacing wires. The optimal cutoff values used to predict the use of pacing wires for central venous pressure, left atrial pressure, pulmonary arterial pressure/systemic blood pressure ratio, and right ventricular pressure/left ventricular pressure ratio were 11 mmHg (55.6% sensitivity, 86.2% specificity), 13 mmHg (50% sensitivity, 84.6% specificity), 0.39 (69.6% sensitivity, 78.7% specificity), and 0.51 (74.1% sensitivity, 64.2% specificity), respectively. Multivariable logistic regression analyses showed that the use of temporary epicardial pacing wires was significantly associated with left atrial pressure ≥ 11 mmHg (odds ratio 4.4; 95% confidence interval 1.01-18.9), and a pulmonary arterial pressure/systemic blood pressure ratio ≥ 0.39 (odds ratio 6.3; 95% confidence interval 1.3-31.4). High post-procedure intracardiac pressures were associated with the use of temporary epicardial pacing wires. These data can aid in the decision-making for the proper use of temporary epicardial pacing wires.

Cardiac arrest caused by rapidly increasing ascites in a patient with TAFRO syndrome: a case report.

Case: Thrombocytopenia, anasarca, fever, renal insufficiency, and organomegaly (TAFRO) syndrome is a newly defined systemic inflammatory disorder with gradual progression of symptoms. A 59-year-old man with fever and ascites of unknown cause developed sudden-onset shock and respiratory failure in the general ward. Cardiac arrest immediately followed. Although he was resuscitated, frequent administration of adrenaline was required to maintain his blood pressure. His circulation was most effectively stabilized by drainage of fluid from his distended abdomen. The volume of discharged ascites reached 4,000 mL at that time, and several liters continued to be discharged for >1 month. The diagnosis of TAFRO syndrome was based on the clinical features and laboratory and histological findings. Outcome: The ascites volume and concentrations of inflammatory parameters decreased with treatment using several immunosuppressive agents. Conclusion: The newly defined TAFRO syndrome may be life-threatening. Patients should be monitored for progression to shock and cardiac arrest, especially those with rapidly increasing ascites.