Neutrophil reduction attenuates the severity of lung injury in the early phase of pneumococcal pneumonia in mice.

Neutrophils are the first leukocytes to be recruited to sites of inflammation in response to chemotactic factors released by activated macrophages and pulmonary epithelial and endothelial cells in bacterial pneumonia, a common cause of acute respiratory distress syndrome (ARDS). Although neutrophilic inflammation facilitates the elimination of pathogens, neutrophils also may cause bystander tissue injury. Even though the presence of neutrophils in alveolar spaces is a key feature of acute lung injury and ARDS especially from pneumonia, their contribution to the pathogenesis of lung injury is uncertain. The goal of this study was to elucidate the role of neutrophils in a clinically relevant model of bacterial pneumonia. We investigated the effect of reducing neutrophils in a mouse model of pneumococcal pneumonia treated with antibiotics. Neutrophils were reduced with anti-lymphocyte antigen 6 complex locus G6D (Ly6G) monoclonal antibody 24 h before and immediately preceding infection. Mice were inoculated intranasally with Streptococcus pneumoniae and received ceftriaxone 12 h after bacterial inoculation. Neutrophil reduction in mice treated with ceftriaxone attenuated hypoxemia, alveolar permeability, epithelial injury, pulmonary edema, and inflammatory biomarker release induced by bacterial pneumonia, even though bacterial loads in the distal air spaces of the lung were modestly increased as compared with antibiotic treatment alone. Thus, when appropriate antibiotics are administered, lung injury in the early phase of bacterial pneumonia is mediated in part by neutrophils. In the early phase of bacterial pneumonia, neutrophils contribute to the severity of lung injury, although they also participate in host defense.NEW & NOTEWORTHY Neutrophil accumulation is a key feature of ARDS, but their contribution to the pathogenesis is still uncertain. We investigated the effect of reducing neutrophils in a clinically relevant mouse model of pneumococcal pneumonia treated with antibiotics. When appropriate antibiotics were administered, neutrophil reduction with Ly6G antibody markedly attenuated lung injury and improved oxygenation. In the early phase of bacterial pneumonia, neutrophils contribute to the severity of lung injury, although they also participate in host defense.

Biological effects of corticosteroids on pneumococcal pneumonia in Mice-translational significance.

BACKGROUND: Streptococcus pneumoniae is the most common bacterial cause of community acquired pneumonia and the acute respiratory distress syndrome (ARDS). Some clinical trials have demonstrated a beneficial effect of corticosteroid therapy in community acquired pneumonia, COVID-19, and ARDS, but the mechanisms of this benefit remain unclear. The primary objective of this study was to investigate the effects of corticosteroids on the pulmonary biology of pneumococcal pneumonia in a mouse model. A secondary objective was to identify shared transcriptomic features of pneumococcal pneumonia and steroid treatment in the mouse model and clinical samples. METHODS: We carried out comprehensive physiologic, biochemical, and histological analyses in mice to identify the mechanisms of lung injury in Streptococcus pneumoniae with and without adjunctive steroid therapy. We also studied lower respiratory tract gene expression from a cohort of 15 mechanically ventilated patients (10 with Streptococcus pneumoniae and 5 controls) to compare with the transcriptional studies in the mice. RESULTS: In mice with pneumonia, dexamethasone in combination with ceftriaxone reduced (1) pulmonary edema formation, (2) alveolar protein permeability, (3) proinflammatory cytokine release, (4) histopathologic lung injury score, and (5) hypoxemia but did not increase bacterial burden. Transcriptomic analyses identified effects of steroid therapy in mice that were also observed in the clinical samples. CONCLUSIONS: In combination with appropriate antibiotic therapy in mice, treatment of pneumococcal pneumonia with steroid therapy reduced hypoxemia, pulmonary edema, lung permeability, and histologic criteria of lung injury, and also altered inflammatory responses at the protein and gene expression level. The transcriptional studies in patients suggest that the mouse model replicates some of the features of pneumonia in patients with Streptococcus pneumoniae and steroid treatment. Overall, these studies provide evidence for the mechanisms that may explain the beneficial effects of glucocorticoid therapy in patients with community acquired pneumonia from Streptococcus Pneumoniae.

Biological Effects of Corticosteroids on Pneumococcal Pneumonia in Mice and Humans.

Background: Streptococcus pneumoniae is the most common bacterial cause of community acquired pneumonia and the acute respiratory distress syndrome (ARDS). Some clinical trials have demonstrated a beneficial effect of corticosteroid therapy in community acquired pneumonia, COVID-19, and ARDS, but the mechanisms of this benefit remain unclear. The objective of this study was to investigate the effects of corticosteroids on the pulmonary biology of pneumococcal pneumonia in an observational cohort of mechanically ventilated patients and in a mouse model of bacterial pneumonia with Streptococcus pneumoniae. Methods: We studied gene expression with lower respiratory tract transcriptomes from a cohort of mechanically ventilated patients and in mice. We also carried out comprehensive physiologic, biochemical, and histological analyses in mice to identify the mechanisms of lung injury in Streptococcus pneumoniae with and without adjunctive steroid therapy. Results: Transcriptomic analysis identified pleiotropic effects of steroid therapy on the lower respiratory tract in critically ill patients with pneumococcal pneumonia, findings that were reproducible in mice. In mice with pneumonia, dexamethasone in combination with ceftriaxone reduced (1) pulmonary edema formation, (2) alveolar protein permeability, (3) proinflammatory cytokine release, (4) histopathologic lung injury score, and (5) hypoxemia but did not increase bacterial burden. Conclusions: The gene expression studies in patients and in the mice support the clinical relevance of the mouse studies, which replicate several features of pneumococcal pneumonia and steroid therapy in humans. In combination with appropriate antibiotic therapy in mice, treatment of pneumococcal pneumonia with steroid therapy reduced hypoxemia, pulmonary edema, lung permeability, and histologic criteria of lung injury, and also altered inflammatory responses at the protein and gene expression level. The results from these studies provide evidence for the mechanisms that may explain the beneficial effects of glucocorticoid therapy in patients with community acquired pneumonia from Streptococcus Pneumoniae.

Evidence for lung barrier regeneration by differentiation prior to binucleated and stem cell division.

With each breath, oxygen diffuses across remarkably thin alveolar type I (AT1) cells into underlying capillaries. Interspersed cuboidal AT2 cells produce surfactant and act as stem cells. Even transient disruption of this delicate barrier can promote capillary leak. Here, we selectively ablated AT1 cells, which uncovered rapid AT2 cell flattening with near-continuous barrier preservation, culminating in AT1 differentiation. Proliferation subsequently restored depleted AT2 cells in two phases, mitosis of binucleated AT2 cells followed by replication of mononucleated AT2 cells. M phase entry of binucleated and S phase entry of mononucleated cells were both triggered by AT1-produced hbEGF signaling via EGFR to Wnt-active AT2 cells. Repeated AT1 cell killing elicited exuberant AT2 proliferation, generating aberrant daughter cells that ceased surfactant function yet failed to achieve AT1 differentiation. This hyperplasia eventually resolved, yielding normal-appearing alveoli. Overall, this specialized regenerative program confers a delicate simple epithelium with functional resiliency on par with the physical durability of thicker, pseudostratified, or stratified epithelia.

Asynchrony Injures Lung and Diaphragm in Acute Respiratory Distress Syndrome.

OBJECTIVES: Patient-ventilator asynchrony is often observed during mechanical ventilation and is associated with higher mortality. We hypothesized that patient-ventilator asynchrony causes lung and diaphragm injury and dysfunction. DESIGN: Prospective randomized animal study. SETTING: University research laboratory. SUBJECTS: Eighteen New Zealand White rabbits. INTERVENTIONS: Acute respiratory distress syndrome (ARDS) model was established by depleting surfactants. Each group (assist control, breath stacking, and reverse triggering) was simulated by phrenic nerve stimulation. The effects of each group on lung function, lung injury (wet-to-dry lung weight ratio, total protein, and interleukin-6 in bronchoalveolar lavage), diaphragm function (diaphragm force generation curve), and diaphragm injury (cross-sectional area of diaphragm muscle fibers, histology) were measured. Diaphragm RNA sequencing was performed using breath stacking and assist control ( n = 2 each). MEASUREMENTS AND MAIN RESULTS: Inspiratory effort generated by phrenic nerve stimulation was small and similar among groups (esophageal pressure swing ≈ -2.5 cm H 2 O). Breath stacking resulted in the largest tidal volume (>10 mL/kg) and highest inspiratory transpulmonary pressure, leading to worse oxygenation, worse lung compliance, and lung injury. Reverse triggering did not cause lung injury. No asynchrony events were observed in assist control, whereas eccentric contractions occurred in breath stacking and reverse triggering, but more frequently in breath stacking. Breath stacking and reverse triggering significantly reduced diaphragm force generation. Diaphragmatic histology revealed that the area fraction of abnormal muscle was ×2.5 higher in breath stacking (vs assist control) and ×2.1 higher in reverse triggering (vs assist control). Diaphragm RNA sequencing analysis revealed that genes associated with muscle differentiation and contraction were suppressed, whereas cytokine- and chemokine-mediated proinflammatory responses were activated in breath stacking versus assist control. CONCLUSIONS: Breath stacking caused lung and diaphragm injury, whereas reverse triggering caused diaphragm injury. Thus, careful monitoring and management of patient-ventilator asynchrony may be important to minimize lung and diaphragm injury from spontaneous breathing in ARDS.

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.

Mechanisms of impaired alveolar fluid clearance.

Impaired alveolar fluid clearance (AFC) is an important cause of alveolar edema fluid accumulation in patients with acute respiratory distress syndrome (ARDS). Alveolar edema leads to insufficient gas exchange and worse clinical outcomes. Thus, it is important to understand the pathophysiology of impaired AFC in order to develop new therapies for ARDS. Over the last few decades, multiple experimental studies have been done to understand the molecular, cellular, and physiological mechanisms that regulate AFC in the normal and the injured lung. This review provides a review of AFC in the normal lung, focuses on the mechanisms of impaired AFC, and then outlines the regulation of AFC. Finally, we summarize ongoing challenges and possible future research that may offer promising therapies for ARDS.

Fluid dynamic assessment of positive end-expiratory pressure in a tracheostomy tube connector during respiration.

High-flow oxygen therapy using a tracheostomy tube is a promising clinical approach to reduce the work of breathing in tracheostomized patients. Positive end-expiratory pressure (PEEP) is usually applied during oxygen inflow to improve oxygenation by preventing end-expiratory lung collapse. However, much is still unknown about the geometrical effects of PEEP, especially regarding tracheostomy tube connectors (or adapters). Quantifying the degree of end-expiratory pressure (EEP) that takes patient-specific spirometry into account would be useful in this regard, but no such framework has been established yet. Thus, a platform to assess PEEP under respiration was developed, wherein three-dimensional simulation of airflow in a tracheostomy tube connector is coupled with a lumped lung model. The numerical model successfully reflected the magnitude of EEP measured experimentally using a lung phantom. Numerical simulations were further performed to quantify the effects of geometrical parameters on PEEP, such as inlet angles and rate of stenosis in the connector. Although sharp inlet angles increased the magnitude of EEP, they cannot be expected to achieve clinically reasonable PEEP. On the other hand, geometrical constriction in the connector can potentially result in PEEP as obtained with conventional nasal cannulae.

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.

Perioperative factors related to the severity of vocal cord paralysis after thoracic cardiovascular surgery: A retrospective review.

BACKGROUND: Vocal cord paralysis (VCP) is a rare complication of thoracic cardiovascular surgery. In severe cases, life-threatening airway obstruction may occur. OBJECTIVE: To evaluate the incidence and severity of VCP among patients who underwent thoracic cardiovascular surgery and to identify possible risk factors. DESIGN: Single-centre retrospective review of adult patients. SETTING: Osaka University Hospital, Suita, Japan, from January 2013 to August 2015. PATIENTS: We included 688 patients in the final analysis. Preoperative, intraoperative and postoperative data were collected from medical records. Patients with preoperative VCP or tracheostomy prior to extubation were excluded. The VCP severity in relation to functional recovery was graded using the following categories: absent; mild, remission at 6 months; moderate, partial or persistent VCP at 6 months; or severe, airway obstruction after extubation requiring reintubation. An otolaryngologist diagnosed all VCP cases. MAIN OUTCOME MEASURES: The incidence and severity of VCP after extubation. RESULTS: The incidence (number) of VCP was 4.7% (32), with those of mild, moderate and severe VCP being 1.7% (12), 1.5% (10) and 1.5% (10), respectively. The ICU stay was significantly longer in patients with severe VCP than in patients without VCP [12.5 days (interquartile range 5.5 to 25.5) vs. 3 days (interquartile range 2 to 5), P = 0.0002]. In our multivariable analysis, type 2 diabetes mellitus [odds ratio (OR) 1.853, P = 0.009], intubation period (OR per 24 h 1.136, P = 0.014), ascending aortic arch surgery with brachiocephalic artery reconstruction (OR 8.708, P < 0.001) and ventricular assist device implantation (OR 3.460, P = 0.005) were independent predictors for VCP. CONCLUSION: The identification of these risk factors may facilitate screening for VCP before extubation and possibly help anaesthesia personnel to be prepared to treat VCP-related airway obstruction should it occur.

[Anesthetic Management of Off-pump Coronary Artery Bypass Grafting in a Patient with Adrenal Pheochromocytoma].

A 64-year-old male patient with pheochromocytoma underwent an off-pump coronary artery bypass graft- ing. Determination of order of surgeries, preoperative medical management and intraoperative hemodynamic management are important in these cases. Al- though bolus administration of phenylephrine showed poor response, the surgery was uneventful and the patient remained hemodynamically stable throughout the procedure and perioperative period.

Right ventricular functional assessment by three-dimensional transesophageal echocardiography is useful for withdrawal from a right ventricular assist device: a case report.

Right ventricular assist device (RVAD) implantation is one type of surgical treatment used for right heart failure. It is important to assess right ventricular (RV) function precisely when RVAD withdrawal is considered. Although assessment of RV function is difficult due to its complicated shape and contraction pattern, the volumetric analysis method of three-dimensional (3D) transesophageal echocardiography (TEE) has been developed and is useful for this task. We report the case of a 79-year-old man who successfully underwent RVAD withdrawal and evaluation using 3D TEE. 3D TEE had an important role in determining the timing of withdrawal from RVAD in this case.

Successful pulmonary embolectomy for massive pulmonary embolism during pregnancy: a case report.

BACKGROUND: Pulmonary embolism (PE) resulting from venous thromboembolism is a leading cause of maternal mortality in pregnancy. In patients with massive PE and hemodynamic instability, the treatment options often considered are thrombolytics, inferior vena caval filters, or embolectomy. We report here the case of a patient with massive PE at 28 weeks' gestation, who underwent emergency pulmonary embolectomy via cardiopulmonary bypass. CASE PRESENTATION: A 35-year old primigravida with a history of massive PE at 25 weeks of gestation was referred to our hospital at 28 weeks of gestation, following treatment failure after insertion of an inferior vena cava filter and heparin administration. Emergency thrombectomy was performed, and intracardiac echography was used for intraoperative fetal heart rate monitoring. However, the patient developed hemodynamic collapse following anesthesia induction; hence, emergency cardiopulmonary bypass (CPB) was performed via median sternotomy. Thrombectomy and tricuspid valve plication were performed under cardiac arrest. After confirming postoperative hemostasis, heparin administration was resumed. At 40 weeks of gestation, labor was induced under epidural analgesia. Both mother and child were discharged with no complications. CONCLUSION: In conclusion, intracardiac echography is useful for fetal heart rate monitoring during emergency cardiac surgery in pregnancy. Careful CPB management is important to maintain uteroplacental blood flow. Although there is no consensus on the delivery methods in such cases, epidural analgesia during labor was useful in reducing cardiac load and wound traction.

[A case of colonoscopy release of intussusception due to sigmoid colon cancer].

A 53-year-old woman with recurrent abdominal pain was referred to our hospital. Based on the enhanced abdominal computed tomographic (CT) finding, she was diagnosed with intussusception of the sigmoid colon. Colonoscopy was performed to release the intussusception, and a lead point lesion was detected. An advanced cancer was found in the rectum, which could be pushed back into the sigmoid colon easily using pressurized air. A more-advanced colon cancer was also detected on the oral side of the lesion. The patient was diagnosed with double cancer of the sigmoid colon and was treated with laparoscopic sigmoidectomy with lymph node resection (D3). Preliminary reduction by colonoscopy prior to surgery is an effective option in cases of adult intussusception. Colonoscopy can be used to perform definitive and qualitative diagnoses.

Comparison of the effects of angiotensin II receptor antagonist monotherapy and combination therapy with a diuretic on cardiac function in spontaneously hypertensive rats.

OBJECTIVE: Losartan, an angiotensin II receptor blocker (ARB), has been reported to promote sodium excretion and show an enhanced antihypertensive effect when used in combination with hydrochlorothiazide (HCTZ). We investigated the effects of losartan monotherapy and combination therapy together with HCTZ on cardiac function in hypertensive rats using echocardiography. METHODS: Spontaneously hypertensive rats (n = 21) fed on high-salt diet (8 % NaCl) for 13 weeks were randomly assigned to rats without medication (HS, n = 7), those medicated with ARB (ARB, losartan 30 mg/kg/day, n = 8), and those with ARB and HCTZ (ARB + HCTZ, losartan 30 mg/kg/day + HCTZ 10 mg/kg/day, n = 6). Blood pressure measurements and echocardiography were performed at 13, 17, and 29 weeks of age. After the end of the protocol, the proportion of cardiac muscle fibrosis was measured histologically. RESULTS: In the HS group, blood pressure and left ventricular mass/body weight (LV mass/BW) increased, and % fractional shortening (%FS) and early diastolic mitral annular velocity (e') decreased significantly with age. In the ARB group, although blood pressure and %FS were maintained, LV mass/BW increased with age as in the HS group, and e' decreased. In the ARB + HCTZ group, blood pressure decreased and LV mass/BW, %FS, and e' were maintained. The progression of myocardial fibrosis was clearly prevented in rats treated with ARB. CONCLUSION: ARB was shown to inhibit systolic disorder and myocardial fibrosis in hypertensive rats. Combination therapy proved to be more effective than monotherapy and is also effective in inhibiting diastolic disorders.