Combined Use of Alkaline Agents With Low-Flow Extracorporeal Carbon Dioxide Removal in Carbon Dioxide Inhalation Models Preserving Inspiratory Efforts

Background

Low-flow extracorporeal CO 2 removal (ECCO 2 R), managed using a renal replacement platform, is useful in achieving lung-protective ventilation with low tidal volume. However, its capacity for CO 2 elimination is limited. Whether this system is valuable in reducing strong inspiratory efforts in respiratory failure is unclear. The combined use of alkaline agents with low-flow ECCO 2 R might be useful in hypercapnic subjects preserving inspiratory efforts.

Methods

This study examined the effects of low-flow ECCO 2 R on respiratory status and investigated the effects of NaHCO 3 , trometamol, and saline on respiratory status during low-flow ECCO 2 R in CO 2 inhalation models.

Results

Although low-flow ECCO 2 R did not significantly change the respiratory rate (92.2% ± 24.3% [mean ± standard deviation] of that before ECCO 2 R), it reduced minute ventilation (MV) (78.9% ± 13.5% of that before ECCO 2 R). The addition of NaHCO 3 improved acidemia but did not change MV compared with that of the saline group (0.451 ± 0.026 L/min/kg body weight [BW] vs. 0.556 ± 0.138 L/min/kg BW, respectively). The addition of trometamol improved acidemia and reduced MV compared with that of the saline group (0.381 ± 0.050 L/min/kg BW vs. 0.556 ± 0.138 L/min/kg BW, respectively). The total amounts of CO 2 removed during ECCO 2 R in the NaHCO 3 group were lower than those in the saline and trometamol groups.

Conclusion

The low-flow ECCO 2 R reduced MV in subjects preserving spontaneous breathing efforts with CO 2 overload. The addition of NaHCO 3 improved acidemia but did not change MV, whereas the addition of trometamol improved acidemia and reduced MV.

Dysbiosis of gut microbiota in patients with severe COVID-19

Aim

Altered gut microbiota has been proposed as one of the causes of exacerbation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2/COVID-19) from the perspective of the gut-lung axis. We aimed to evaluate gut microbiota in mechanically ventilated patients with COVID-19 prior to using antibiotics.

Methods

We retrospectively selected for enrollment COVID-19 patients who required mechanical ventilation on admission but who had not used antibiotics before admission to observe the influence of SARS-Cov-2 on gut microbiota. Fecal samples were collected serially on admission and were evaluated by 16S rRNA gene deep sequencing.

Results

The phylum of Bacteroidetes decreased, and those of Firmicutes and Actinobacteria increased in COVID-19 patients compared with those in healthy controls (p < 0.001). The main commensals of Bacteroides, Faecalibacterium, and Blautia at the genus level were significantly decreased in the COVID-19 patients, and opportunistic bacteria including Corynebacterium, Anaerococcus, Finegoldia Peptoniphilus, Actinomyces, and Enterococcus were increased (p < 0.001). α-Diversity and β-diversity in COVID-19 patients significantly changed compared with those in the healthy controls.

Conclusion

The commensal gut microbiota were altered, and opportunistic bacteria increased in patients with severe COVID-19 who required mechanical ventilation on admission.

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.

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.

Factors Associated With Prolonged Ventilation in Patients Receiving Prone Positioning Protocol With Muscle Relaxants for Severe COVID-19 Pneumonia

BACKGROUND

Prone positioning and neuromuscular blocking agents (NMBAs) are frequently used to treat severe respiratory failure from COVID-19 pneumonia. Prone positioning has shown to improve mortality, whereas NMBAs are used to prevent ventilator asynchrony and reduce patient self-inflicted lung injury. However, despite the use of lung-protective strategies, high death rates in this patient population have been reported.

METHODS

We retrospectively examined the factors affecting prolonged mechanical ventilation in patients receiving prone positioning plus muscle relaxants. The medical records of 170 patients were reviewed. Subjects were divided into 2 groups according to ventilator-free days (VFDs) at day 28. Whereas subjects with VFDs < 18 d were defined as prolonged mechanical ventilation, subjects with VFDs ≥18 d were defined as short-term mechanical ventilation. Subjects' baseline status, status at ICU admission, therapy before ICU admission, and treatment in the ICU were studied.

RESULTS

Under the proning protocol for COVID-19, the mortality rate in our facility was 11.2%. The prognosis may be improved by avoiding lung injury in the early stages of mechanical ventilation. According to multifactorial logistic regression analysis, persistent SARS-CoV-2 viral shedding in blood (P = .027), higher daily corticosteroid use before ICU admission (P = .007), delayed recovery of lymphocyte count (P < .001), and higher maximal fibrinogen degradation products (P = .039) were associated with prolonged mechanical ventilation. A significant relationship was found between daily corticosteroid use before admission and VFDs by squared regression analysis (y = -0.00008522x² + 0.01338x + 12.8; x: daily corticosteroids dosage before admission [prednisolone mg/d]; y: VFDs/28 d, R² = 0.047, P = .02). The peak point of the regression curve was 13.4 d at 78.5 mg/d of the equivalent prednisolone dose, which corresponded to the longest VFDs.

CONCLUSIONS

Persistent SARS-CoV-2 viral shedding in blood, high corticosteroid dose from the onset of symptoms to ICU admission, slow recovery of lymphocyte counts, and high levels of fibrinogen degradation products after admission were associated with prolonged mechanical ventilation in subjects with severe COVID-19 pneumonia.

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.

Association between tracheostomy and survival in patients with coronavirus disease 2019 who require prolonged mechanical ventilation for more than 14 days: A multicenter cohort study

OBJECTIVE

Tracheostomy is a common procedure with potential prognostic advantages for patients who require prolonged mechanical ventilation (PMV). Early recommendations for patients with coronavirus disease 2019 (COVID-19) suggested delayed or limited tracheostomy considering the risk for viral transmission to clinicians. However, updated guidelines for tracheostomy with appropriate personal protective equipment have revised its indications. This study aimed to evaluate the association between tracheostomy and prognosis in patients with COVID-19 requiring PMV.

METHODS

This was a multicenter, retrospective cohort study using data from the nationwide Japanese Intensive Care PAtient Database. We included adult patients aged ≥16 years who were admitted to the intensive care unit (ICU) due to COVID-19 and who required PMV (for >14 days or until performance of tracheostomy). The primary outcome was hospital mortality, and the association between implementation of tracheostomy and patient prognosis was assessed using weighted Cox proportional hazards regression analysis with inverse probability of treatment weighting (IPTW) using the propensity score to address confounders.

RESULTS

Between January 2020 and February 2021, 453 patients with COVID-19 were observed. Data from 109 patients who required PMV were analyzed: 66 (60.6%) underwent tracheostomy and 38 (34.9%) died. After adjusting for potential confounders using IPTW, tracheostomy implementation was found to significantly reduce hospital mortality (hazard ratio [HR]: 0.316, 95% confidence interval [CI]: 0.163-0.612). Patients who underwent tracheostomy had a similarly decreased ICU and 28-day mortality (HR: 0.269, 95% CI: 0.124-0.581; HR 0.281, 95% CI: 0.094-0.839, respectively). A sensitivity analysis using different definitions of PMV duration consistently showed reduced mortality in patients who underwent tracheostomy.

CONCLUSION

The implementation of tracheostomy was associated with favorable patient prognosis among patients with COVID-19 requiring PMV. Our findings support proactive tracheostomy in critically ill patients with COVID-19 requiring mechanical ventilation for >14 days.

Secondary subcutaneous abscess due to mixed infections by Peptoniphilus olsenii and Gleimia europaea after COVID-19

This report described a rare case of subcutaneous anaerobic bacterial abscess due to Peptoniphilus olsenii and Gleimia europaea after COVID-19. The patient received incision and drainage of the abscess and antibiotics, thereby achieving recovery. Immunodeficiency related to COVID-19 and its treatment might contribute to secondary skin and subcutaneous bacterial infections.

Establishment and clinical application of SARS-CoV-2 catch column

BACKGROUND

A certain number of patients with coronavirus disease 2019 (COVID-19), particularly those who test positive for SARS-CoV-2 in the serum, are hospitalized. Further, some even die. We examined the effect of blood adsorption therapy using columns that can eliminate SARS-CoV-2 on the improvement of the prognosis of severe COVID-19 patients.

METHODS

This study enrolled seven patients receiving mechanical ventilation. The patients received viral adsorption therapy using SARS-catch column for 3 days. The SARS-catch column was developed by immobilizing a specific peptide, designed based on the sequence of human angiotensin-converting enzyme 2 (hACE2), to an endotoxin adsorption column (PMX). In total, eight types of SARS-CoV-2-catch (SCC) candidate peptides were developed. Then, a clinical study on the effects of blood adsorption therapy using the SARS-catch column in patients with severe COVID-19 was performed, and the data in the present study were compared with historical data of severe COVID-19 patients.

RESULTS

Among all SCC candidate peptides, SCC-4N had the best adsorption activity against SARS-CoV-2. The SARS-catch column using SCC-4N removed 65% more SARS-CoV-2 than PMX. Compared with historical data, the weaning time from mechanical ventilation was faster in the present study. In addition, the rate of negative blood viral load in the present study was higher than that in the historical data.

CONCLUSION

The timely treatment with virus adsorption therapy may eliminate serum SARS-CoV-2 and improve the prognosis of patients with severe COVID-19. However, large-scale studies must be performed in the future to further assess the finding of this study (jRCTs052200134).

Timing of tracheostomy and patient outcomes in critically ill patients requiring extracorporeal membrane oxygenation: a single-center retrospective observational study

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is an integral method of life support in critically ill patients with severe cardiopulmonary failure; however, such patients generally require prolonged mechanical ventilation and exhibit high mortality rates. Tracheostomy is commonly performed in patients on mechanical ventilation, and its early implementation has potential advantages for favorable patient outcomes. This study aimed to investigate the association between tracheostomy timing and patient outcomes, including mortality, in patients requiring ECMO.

METHODS

We conducted a single-center retrospective observational study of consecutively admitted patients who were supported by ECMO and underwent tracheostomy during intensive care unit (ICU) admission at a tertiary care center from April 2014 until December 2021. The primary outcome was hospital mortality. Using the quartiles of tracheostomy timing, the patients were classified into four groups for comparison. The association between the quartiles of tracheostomy timing and mortality was explored using multivariable logistic regression models.

RESULTS

Of the 293 patients treated with ECMO, 98 eligible patients were divided into quartiles 1 (≤ 15 days), quartile 2:16-19 days, quartile 3:20-26 days, and 4 (> 26 days). All patients underwent surgical tracheostomy and 35 patients underwent tracheostomy during ECMO. The complications of tracheostomy were comparable between the groups, whereas the duration of ECMO and ICU length of stay increased significantly as the quartiles of tracheostomy timing increased. Patients in quartile 1 had the lowest hospital mortality rate (19.2%), whereas those in quartile 4 had the highest mortality rate (50.0%). Multivariate logistic regression analysis showed a significant association between the increment of the quartiles of tracheostomy timing and hospital mortality (adjusted odds ratio for quartile increment:1.55, 95% confidence interval 1.03-2.35, p for trend = 0.037).

CONCLUSIONS

The timing of tracheostomy in patients requiring ECMO was significantly associated with patient outcomes in a time-dependent manner. Further investigation is warranted to determine the optimal timing of tracheostomy in terms of mortality.

Control of blood glucose levels by an artificial pancreas in patients with severe coronavirus disease 2019 pneumonia

BACKGROUND

Many patients with severe coronavirus disease 2019 (COVID-19) pneumonia experience hyperglycemia. It is often difficult to control blood glucose (BG) levels in such patients using standard intravenous insulin infusion therapy. Therefore, we used an artificial pancreas. This study aimed to compare the BG status of the artificial pancreas with that of standard therapy.

METHODS

Fifteen patients were included in the study. BG values and the infusion speed of insulin and glucose by the artificial pancreas were collected. Arterial BG and administration rates of insulin, parenteral sugar, and enteral sugar were recorded during the artificial pancreas and standard therapy. The target BG level was 200 mg/dl.

RESULTS

Arterial BG was highly correlated with BG data from the artificial pancreas. A higher BG slightly increased the difference between the BG data from the artificial pancreas and arterial BS. No significant difference in arterial BG was observed between the artificial pancreas and standard therapy. However, the standard deviation with the artificial pancreas was smaller than that under standard therapy (p < 0.0001). More points within the target BG range were achieved with the artificial pancreas (180-220 mg/dl) than under standard therapy. The hyperglycemic index of the artificial pancreas (8.7 ± 15.6 mg/dl) was lower than that of standard therapy (16.0 ± 21.5 mg/dl) (p = 0.0387). No incidence of hypoglycemia occurred under the artificial pancreas.

CONCLUSIONS

The rate of achieving target BG was higher using artificial pancreas than with standard therapy. An artificial pancreas helps to control BG in critically ill patients.

Ischemic Stroke Due to Heparin-induced Thrombocytopenia during Severe COVID-19 Infection

A 53-year-old woman with severe coronavirus disease 2019 (COVID-19) pneumonia was admitted and treated with intravenous unfractionated heparin for thromboprophylaxis under general anesthesia with mechanical ventilation. She developed right hemiparesis after hospitalization due to a large hemorrhagic infarction. Her platelet count decreased from 243,000/μL at administration to 121,000/μL. Anti-platelet factor 4-heparin antibody testing was positive according to a latex immunoturbidimetric assay. She was therefore diagnosed with heparin-induced thrombocytopenia. We immediately stopped the heparin and started argatroban; the platelet count recovered, and thrombosis did not relapse. Physicians should consider heparin-induced thrombocytopenia as a cause of ischemic stroke in patients with COVID-19 infection.

Prediction Model of Extubation Outcomes in Critically Ill Patients: A Multicenter Prospective Cohort Study

Liberation from mechanical ventilation is of great importance owing to related complications from extended ventilation time. In this prospective multicenter study, we aimed to construct a versatile model for predicting extubation outcomes in critical care settings using obtainable physiological predictors. The study included patients who had been extubated after a successful 30 min spontaneous breathing trial (SBT). A multivariable logistic regression model was constructed to predict extubation outcomes (successful extubation without reintubation and uneventful extubation without reintubation or noninvasive respiratory support) using eight parameters: age, heart failure, respiratory disease, rapid shallow breathing index (RSBI), PaO2/FIO2, Glasgow Coma Scale score, fluid balance, and endotracheal suctioning episodes. Of 499 patients, 453 (90.8%) and 328 (65.7%) achieved successful and uneventful extubation, respectively. The areas under the curve for successful and uneventful extubation in the novel prediction model were 0.69 (95% confidence interval (CI), 0.62−0.77) and 0.70 (95% CI, 0.65−0.74), respectively, which were significantly higher than those in the conventional model solely using RSBI (0.58 (95% CI, 0.50−0.66) and 0.54 (95% CI, 0.49−0.60), p = 0.004 and <0.001, respectively). The model was validated using a bootstrap method, and an online application was developed for automatic calculation. Our model, which is based on a combination of generally obtainable parameters, established an accessible method for predicting extubation outcomes after a successful SBT.

Association between early tracheostomy and patient outcomes in critically ill patients on mechanical ventilation: a multicenter cohort study

Background

Tracheostomy is commonly performed in critically ill patients because of its clinical advantages over prolonged translaryngeal endotracheal intubation. Early tracheostomy has been demonstrated to reduce the duration of mechanical ventilation and length of stay. However, its association with mortality remains ambiguous. This study aimed to evaluate the association between the timing of tracheostomy and mortality in patients receiving mechanical ventilation.

Methods

We performed a retrospective cohort analysis of adult patients who underwent tracheostomy during their intensive care unit (ICU) admission between April 2015 and March 2019. Patients who underwent tracheostomy before or after 29 days of ICU admission were excluded. Data were collected from the nationwide Japanese Intensive Care Patient Database. The primary outcome was hospital mortality. The timing of tracheostomy was stratified by quartile, and the association between patient outcomes was evaluated using regression analysis.

Results

Among the 85558 patients admitted to 46 ICUs during the study period, 1538 patients were included in the analysis. The quartiles for tracheostomy were as follows: quartile 1, ≤ 6 days; quartile 2, 7–10 days; quartile 3, 11–14 days; and quartile 4, > 14 days. Hospital mortality was significantly higher in quartile 2 (adjusted odds ratio [aOR]: 1.52, 95% confidence interval [CI]: 1.08–2.13), quartile 3 (aOR: 1.82, 95% CI: 1.28–2.59), and quartile 4 (aOR: 2.26, 95% CI: 1.61–3.16) (p for trend < 0.001) than in quartile 1. A similar trend was observed in the subgroup analyses of patients with impaired consciousness (Glasgow Coma Scale score < 8) and respiratory failure (PaO₂:FiO₂ ≤ 300) at ICU admission (p for trend = 0.081 and 0.001, respectively).

Conclusions

This multi-institutional observational study demonstrated that the timing of tracheostomy was significantly and independently associated with hospital mortality in a stepwise manner. Thus, early tracheostomy may be beneficial for patient outcomes, including mortality, and warrants further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40560-022-00610-x.

COVID‐19 in a human T‐cell lymphotropic virus type‐1 carrier

This is the first report of COVID‐19 in a human T‐cell lymphotropic virus type‐1 (HTLV‐1) carrier. HTLV‐1 infection can cause immune dysfunction even in asymptomatic carriers. This case highlights the need for guidance on management of COVID‐19‐HTLV‐1 coinfection, specifically on the appropriate use of corticosteroid treatment while considering secondary infection.

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background

Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies.

Methods

In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality.

Findings

Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference –1·69 [–9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5–8] vs 6 [5–8] cm H₂O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52–23·52]; p<0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75–0·86]; p<0·0001).

Interpretation

Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status.

Funding

No funding.

Ivermectin administration is associated with lower gastrointestinal complications and greater ventilator-free days in ventilated patients with COVID-19: A propensity score analysis

Introduction

COVID-19 patients have been reported to have digestive symptoms with poor outcome. Ivermectin, an antiparasitic drug, has been used in COVID-19 patients. The objective of this study was to evaluate whether ivermectin has effects on gastrointestinal complications and ventilator-free days in ventilated patients with COVID-19.

Methods

COVID-19 patients who were mechanically ventilated in the ICU were included in this study. The ventilated patients who received ivermectin within 3 days after admission were assigned to the Ivermectin group, and the others were assigned to the Control group. Patients in the Ivermectin group received ivermectin 200 μg/kg via nasal tube. The incidence of gastrointestinal complications and ventilator-free days within 4 weeks from admission were evaluated as clinical outcomes using a propensity score with the inverse probability weighting method.

Results

We included 88 patients in this study, of whom 39 patients were classified into the Ivermectin group, and 49 patients were classified into the Control group. The hazard ratio for gastrointestinal complications in the Ivermectin group as compared with the Control group was 0.221 (95% confidence interval [CI], 0.057 to 0.855; p = 0.029) in a Cox proportional-hazard regression model. The odds ratio for ventilator-free days as compared with the Control group was 1.920 (95% CI, 1.076 to 3.425; p = 0.027) in a proportional odds logistic regression model.

Conclusions

Ivermectin improved gastrointestinal complications and the number of ventilator-free days in severe COVID-19 patients undergoing mechanical ventilation. Prevention of gastrointestinal symptoms by SARS-Cov-2 might be associated with COVID-19 outcome.

Outcomes of severe peripartum cardiomyopathy and mechanical circulatory support: a case series

Background

We present three cases of severe peripartum cardiomyopathy (PPCM) that required mechanical circulatory supports.

Case presentation

Case 1: A 33-year-old woman developed acute heart failure (AHF) after normal spontaneous delivery. Intra-aortic balloon pump (IABP) was inserted on postpartum day (PD) 10 with a peripartum cardiomyopathy (PPCM), which was withdrawn on PD 30 after medical treatment including anti-prolactin drugs.

Case 2: A 44-year-old woman developed AHF 1 month after vaginal delivery. IABP or extra-corporeal membrane oxygenation (ECMO) was not effective and a biventricular assist device was inserted. It was withdrawn on PD 85 after improvement of left ventricular ejection fraction (LVEF).

Case3: A 37-year-old woman was transferred with a diagnosis of PPCM. Cardiac function unimproved by IABP or ECMO, and a left ventricular assist device was implanted. It was withdrawn on PD 386 after recovery of LVEF.

Conclusion

All the cases with PPCM recovered after mechanical circulatory supports and resumed social lives.

Prolonged corticosteroid therapy and cytomegalovirus infection in patients with severe COVID-19

Systemic corticosteroid therapy is frequently used to treat coronavirus disease 2019 (COVID‐19). However, its maximum duration without secondary infections remains unclear. We aimed to evaluate the utility of monitoring cytomegalovirus (CMV) infection in patients with COVID‐19 and estimate the maximum duration of systemic corticosteroid therapy without secondary infections. We included 59 patients with severe COVID‐19 without CMV infection on admission to the intensive care unit (ICU). All patients received systemic corticosteroid therapy under invasive mechanical ventilation, with examination for plasma CMV‐deoxyribonucleic acid (DNA) levels during the ICU stay. We analyzed the correlations among patient characteristics, CMV infection, diseases, and patient mortality. CMV infections were newly identified in 15 (25.4%) patients; moreover, anti‐CMV treatment was administered to six (10.2%) patients during the ICU stay. Four (6.8%) patients had secondary infection‐related mortality. The cumulative incidences of CMV infection and anti‐CMV treatment during the ICU stay were 26.8% (95% confidence interval [CI], 15.8%–39.0%) and 12.3% (95% CI, 4.8%–23.4%), respectively. Furthermore, the median duration of systemic corticosteroid therapy without CMV infection was 15 days (95% CI, 13–16 days). The presence of CMV infection was associated with mortality during the ICU stay (p = 0.003). Monitoring plasma CMV‐DNA levels could facilitate the detection of secondary CMV infection due to prolonged systemic corticosteroid therapy. The duration of systemic corticosteroid therapy for COVID‐19 should be limited.

Predictors of post-extubation stridor in patients on mechanical ventilation: a prospective observational study

The cuff leak test (CLT) has been widely accepted as a simple and noninvasive method for predicting post-extubation stridor (PES). However, its accuracy and clinical impact remain uncertain. We aimed to evaluate the reliability of CLT and to assess the impact of pre-extubation variables on the incidence of PES. A prospective observational study was performed on adult critically ill patients who required mechanical ventilation for more than 24 h. Patients were extubated after the successful spontaneous breathing trial, and CLT was conducted before extubation. Of the 191 patients studied, 26 (13.6%) were deemed positive through CLT. PES developed in 19 patients (9.9%) and resulted in a higher reintubation rate (8.1% vs. 52.6%, p < 0.001) and longer intensive care unit stay (8 [4.5-14] vs. 12 [8-30.5] days, p = 0.01) than patients without PES. The incidence of PES and post-extubation outcomes were similar in patients with both positive and negative CLT results. Compared with patients without PES, patients with PES had longer durations of endotracheal intubation and required endotracheal suctioning more frequently during the 24-h period prior to extubation. After adjusting for confounding factors, frequent endotracheal suctioning more than 15 times per day was associated with an adjusted odds ratio of 2.97 (95% confidence interval, 1.01-8.77) for PES. In conclusion, frequent endotracheal suctioning before extubation was a significant PES predictor in critically ill patients. Further investigations of its impact on the incidence of PES and patient outcomes are warranted.

Fatal cytomegalovirus pneumonia in a critically ill patient with COVID-19

Coronavirus disease 2019 (COVID-19) can cause severe lymphopenia and respiratory failure requiring prolonged invasive mechanical ventilation (MV). COVID-19 patients with severe lymphopenia or respiratory failure are at risk of developing secondary infections. Here, we present the needle autopsy findings of a critically ill patient with COVID-19 who required reintubation and prolonged MV, and eventually died of secondary cytomegalovirus (CMV) pneumonia. This case highlights the potential risk of long-term steroid use and the need for routine monitoring for CMV infection in critically ill patients with COVID-19.

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.

Advanced cuff pressure control ventilation (ACPCV); a bench study of a new concept of mechanical ventilation

The concept of advanced cuff pressure control ventilation (ACPCV) is that the endotracheal tube (ETT) cuff volume could be controlled and allowed to exhale the gas through the vocal cords. The potential advantages of ACPCV are reduction of dead space, reduction of expiratory airway resistance, and preservation of vocal cord function. We developed the ACPCV system and investigated its performance in bench studies. The ETT cuff volume was regulated via four steps, depending on airway pressure and tracheal pressure. Two ventilatory settings were examined under several rates of spontaneous breathing efforts. Imposed expiratory resistance (R_E), imposed expiratory work of breathing (WOB), and auto-PEEP of ACPCV were compared with continuous mandatory ventilation (CMV). R_E of ACPCV (2.6 ± 0.5 cm H₂O/l/s) was significantly lower than that of CMV (11.6 ± 1.6 cm H₂O/l/s) (p < 0.001). Expiratory WOB of ACPCV (0.25 ± 0.02 J/l) was significantly lower than that of CMV (0.54 ± 0.10 J/l) (p < 0.001). Auto-PEEP of ACPCV (-0.6 ± 0.2 cm H₂O) was significantly lower than that of CMV (1.1 ± 0.7 cm H₂O) (p < 0.001). ACPCV can significantly reduce R_E and expiratory WOB by controlling the ETT cuff volume in synchronisation with mechanical ventilation.

Effects of Ventilatory Settings on Pendelluft Phenomenon During Mechanical Ventilation

BACKGROUND

Pendelluft phenomenon is defined as the displacement of gas from a more recruited nondependent (ND) lung region to a less recruited dependent (D) lung region. This phenomenon may cause lung injury. Thus, a lung model for pendelluft was established, and the effects of ventilatory settings on pendelluft were examined.

METHODS

Two sets of the twin-bellows-type training test lung (TTL) model were utilized. One set of bellows simulated the diaphragm, and the other simulated the lung. One TTL model represented the ND region, and the other represented the D region. The lung bellows were connected to each other and were ventilated with 1 ventilator. The diaphragm bellows were ventilated with 2 synchronized ventilators that regulated pleural pressure levels. We simulated pendelluft by applying different pleural pressure levels to the D and ND bellows. The increment of the tidal volume in the D region from the "no breathing effort" condition was defined as the pendelluft volume. The effects of ventilator settings, such as ventilatory modes, triggering sensitivity, inspiratory pressurization, and inspiratory cycling-off, were examined. The changes in tidal volumes in the D region based on the control settings were compared to assess the severity of pendelluft.

RESULTS

The gas flow from the D region to the ND region was found to be essential in pendelluft, but the severity of this phenomenon was not always proportional to gas flows. The severity increased with the increase in the differences in pleural pressure levels between the ND and D regions, and it was amplified by the difference in lung mechanics between the ND and D regions. However, the ventilator settings had minimal effect on the severity of pendelluft.

CONCLUSIONS

The pendelluft was affected by the heterogeneity of lung mechanics and pleural pressure. Furthermore, a minimal association was observed between the ventilator settings and the severity of pendelluft.

Control system for the new RIKEN 28-GHz superconducting electron cyclotron resonance ion source for SRILAC

A new RIKEN 28-GHz superconducting electron cyclotron resonance ion source (SC-ECRIS) has been installed for the superconducting RIKEN linear accelerator (SRILAC). The new SC-ECRIS control system mainly consists of programmable logic controllers (PLCs) embedded with the Experimental Physics and Industrial Control System. To improve the reliability as compared with previous control systems, two types of PLC central processing units, sequential and Linux, have been installed in the same unit. Past experience has shown that new types of designs that can rapidly respond to system scalability are key. By connecting PLC stations using star-topology field buses, their rapid and cost-effective response to system changes is realized for the new devices. Furthermore, a unique data acquisition system employing a 920-MHz-band radio was developed to measure analog data such as the temperature at the high-voltage stage.

High intensity vanadium beam for synthesis of new superheavy elements with well-controlled emittance by using "slit triplet"

To provide a very powerful vanadium (V) beam with an intensity of at least 6 particle μA for synthesizing a new superheavy element (SHE) with atomic number Z = 119, we have developed a high-temperature oven (HTO) system to evaporate the metallic V powder inside the new superconducting (SC) electron cyclotron ion source. We successfully extracted a V¹³⁺ beam with a maximum beam intensity of 600 eμA with 2.8-kW microwave power and 900-W heating power of the HTO. Furthermore, from a systematic study of the dependence of the beam intensity on the microwave power and the HTO power, we successfully produced a V¹³⁺ beam of 300 eμA at a consumption rate of 3 mg/h, allowing a one-month duration continuous beam to carry out the SHE synthesis. In addition, to avoid serious damage to newly introduced SC acceleration cavities by beam losses, the beam should be transported with a well-controlled emittance. To efficiently limit the beam emittance, we employed a slit triplet consisting of three pairs of slits installed around the focus point of the low-energy beam transport. The first result of the emittance reduction was observed by a pepper-pot type emittance meter as a function of the acceptance of the slit triplet.

High Positive End-Expiratory Pressure Renders Spontaneous Effort Noninjurious

RATIONALE

In acute respiratory distress syndrome (ARDS), atelectatic solid-like lung tissue impairs transmission of negative swings in pleural pressure (Ppl) that result from diaphragmatic contraction. The localization of more negative Ppl proportionally increases dependent lung stretch by drawing gas either from other lung regions (e.g., nondependent lung [pendelluft]) or from the ventilator. Lowering the level of spontaneous effort and/or converting solid-like to fluid-like lung might render spontaneous effort noninjurious.

OBJECTIVES

To determine whether spontaneous effort increases dependent lung injury, and whether such injury would be reduced by recruiting atelectatic solid-like lung with positive end-expiratory pressure (PEEP).

METHODS

Established models of severe ARDS (rabbit, pig) were used. Regional histology (rabbit), inflammation (positron emission tomography; pig), regional inspiratory Ppl (intrabronchial balloon manometry), and stretch (electrical impedance tomography; pig) were measured. Respiratory drive was evaluated in 11 patients with ARDS.

MEASUREMENTS AND MAIN RESULTS

Although injury during muscle paralysis was predominantly in nondependent and middle lung regions at low (vs. high) PEEP, strong inspiratory effort increased injury (indicated by positron emission tomography and histology) in dependent lung. Stronger effort (vs. muscle paralysis) caused local overstretch and greater tidal recruitment in dependent lung, where more negative Ppl was localized and greater stretch was generated. In contrast, high PEEP minimized lung injury by more uniformly distributing negative Ppl, and lowering the magnitude of spontaneous effort (i.e., deflection in esophageal pressure observed in rabbits, pigs, and patients).

CONCLUSIONS

Strong effort increased dependent lung injury, where higher local lung stress and stretch was generated; effort-dependent lung injury was minimized by high PEEP in severe ARDS, which may offset need for paralysis.

Predictors of Successful Extubation in Reintubated Patients: The Impact of Fluid Balance during the 24 Hours Prior to Extubation

How to cite this article: Tanaka A, Yamashita T, Koyama Y, Uchiyama A, Fujino Y. Predictors of Successful Extubation in Reintubated Patients: The Impact of Fluid Balance during the 24 Hours Prior to Extubation. Indian J Crit Care Med 2019;23(7):344–345.

Attaining Low Tidal Volume Ventilation During Patient Triggered Ventilation in Sedated Subjects

BACKGROUND

Low tidal volume (V_T) ventilation has become the preferred approach in patients in the ICU. Sedation reduces V_T by attenuating respiratory drive. Even in deep sedation, some patients exhibit high V_T. We aimed to determine factors associated with low V_T ventilation in deeply sedated subjects who exhibited an inspiratory effort by examination of the acid/base balance using the Stewart model.

METHODS

The medical records of 630 consecutive subjects admitted to the ICU over 1 y were reviewed retrospectively, and daily data sets of patients with a persistent inspiratory effort, P_aO2 /F_IO2 < 300 mm Hg, PEEP > 5 cm H₂O, and a Richmond Agitation Sedation Scale score of -4 or -5 who received assisted pressure-regulated ventilation were collected. The data sets were stratified into high V_T (≥ 8 mL/kg predicted body weight [PBW]) and low V_T (> 8 mL/kg PBW) groups.

RESULTS

Among 235 matched data sets from 100 subjects, 101 and 134 data sets were in the low V_T and high V_T groups, respectively. Set pressure was not different between the groups. PEEP was lower in the low V_T group, and opioids were more frequently used in the high V_T group. Strong ion difference (SID) was higher in the low V_T group. Multivariate analysis revealed that higher SID, lower total nonvolatile weak anion (A_TOT), and absence of opioid administration were associated with attaining low V_T ventilation. Furthermore, V_T/PBW and SID demonstrated a weak inverse correlation, whereas V_T/PBW and A_TOT exhibited a weak correlation. V_T/PBW was lower in the group with higher SID and lower A_TOT, indicating a tendency of metabolic alkalosis.

CONCLUSIONS

Despite weak effects of high SID and low A_TOT, efficient management of the buffering function might be a feasible strategy to achieve low V_T ventilation.

Effective multiple sideband generation using an electro-optic modulator for a multiple isotope magneto-optical trap

Herein, we report an effective method for the generation of radio-frequency (RF) sidebands in an electro-optic modulator for the simultaneous magneto-optical trapping of two isotopes. This is achieved by switching the RF signals alternately, which suppresses the generation of unwanted frequency signals and improves the laser power per sideband. The generated sidebands are successfully applied to a dual-rubidium-isotope magneto-optical trap (MOT), which results in an increased number of trapped atoms. This simple, flexible, and robust technique can be implemented in experiments that require a large number of atoms in multiple-isotope MOTs and for various applications.

Perioperative Enteral Nutrition After Left Ventricular Assist Device Implantation

Objective:

We assessed what predicts nutritional adequacy at day 14 following implantation of left ventricular assist device (LVAD).

Method:

We retrospectively reviewed the cases of 97 adult patients who underwent LVAD implantation at our institution from June 2011 to June 2016. We divided the patients into two groups based on the administered enteral nutrition (EN) calories on post-operative day (POD) 14: the EN calories of group SEN (sufficient enteral nutrition) were >80% of their total target calories, or the EN calories of group IEN (insufficient enteral nutrition) were <80% of their total target calories. We compared the two groups in terms of the perioperative factors within 1 week after surgery.

Results:

Groups SEN and IEN consisted of 53 and 44 patients, respectively. The mean doses of adrenaline and noradrenaline, mean central venous pressure (CVP), duration of nitric oxide administration, and mean residual gastric volume during 1 week after surgery in group SEN were significantly lower than those in group IEN (P < .05). In multivariate analysis, higher CVP during 1 week after surgery was identified as an independent risk factor for delayed EN on POD14 (odds ratio, 1.40; 95% confidence interval, 1.11-1.66; P = .0037). Total bilirubin, occurrence of acute kidney injury, and mixed venous blood saturation during 1 week after surgery were not significant predictors for EN on POD14.

Conclusions:

Increased CVP within 1 week after LVAD implantation was an independent factor for reduced EN feeding.

A Comparison of the Adjustable Ranges of Inspiratory Pressurization During Pressure Controlled Continuous Mandatory Ventilation of 5 ICU Ventilators

BACKGROUND

Faster inspiratory pressurization can improve patient-ventilator synchrony and reduce the patient's work of breathing during pressure controlled continuous mandatory (PC-CMV) ventilation. The characteristics of the pressurization ramp settings are not standardized across ventilators from different manufacturers. We performed a bench test of 5 models of ICU ventilators to examine the effects of pressurization ramp settings on the actual pressurization.

METHODS

A twin-bellows lung model was used, in which one bellow simulates inspiratory muscle activity and the other simulates an adult normal lung model. We made the inspiratory effort by changing the tidal volume of the inspiratory muscle bellow. The effect of pressurization ramp settings on the performance of each ventilator was examined at 3 inspiratory effort levels (ie, none, ordinary, and strong). The pressurization ramp was set at 4 or 5 evenly divided steps from the minimum to maximum for each ventilator. The following parameters were measured: tidal volume, mean airway pressure, maximal inspiratory flow, time to maximal flow, and pressure-time products at 0.3 s (PTP_0.3) and 0.5 s (PTP_0.5) from the beginning of inspiration. PTP_0.3 and PTP_0.5 indicated levels of inspiratory pressurization.

RESULTS

A proportional increase in PTP_0.3 and PTP_0.5 was observed with an increase in the pressurization ramp settings of the recent models of ventilators. PTP_0.3 and PTP_0.5 at ordinary and strong effort levels were similar in the recent models of ventilators. The actual adjustable ranges of PTP_0.3 and PTP_0.5 associated with change in the pressurization ramp settings differed between the 5 ventilators.

CONCLUSIONS

The adjustable ranges of the pressurization were largely different among the different types of ventilators. The actual absolute inspiratory pressurization during PC-CMV varied between the different ventilators even at similar pressurization ramp settings. Users should be mindful of the differences in the pressurization ramp settings.

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.

Nonlinear Analysis of Visual Evoked Potentials Elicited by Color Stimulation

The relationship between chromatically modulated stimuli and visual evoked potentials (VEPs) was considered. VEPs of normal subjects elicited by chromatically modulated stimuli were measured under several color adaptations, and their binary kernels were estimated. Up to the second-order, binary kernels obtained from VEPs were so characteristic that the VEP-chromatic modulation system showed second-order nonlinearity. First-order binary kernels depended on the color of the stimulus and adaptation, whereas second-order kernels showed almost no difference. This result indicates that the waveforms of first-order binary kernels reflect perceived color (hue). This supports the suggestion that kernels of VEPs include color responses, and could be used as a probe with which to examine the color visual system.

Subjective Symptoms Acquisition System in a Health Promotion System for the Elderly

A previous report was concerned with the evaluation of quality of life using a Health Promotion System for the Elderly. In the present report, we describe one part of that system: a subjective symptoms acquisition and reporting system.

The main purpose of this system is to permit any physician or nurse to uniformly employ questionnaires to acquire accurate subjective symptoms. This system is applied in three steps. First, the subjective answers to 21 questions displayed on a personal computer are obtained. These answers correspond to the basic subjective symptoms. Second, if a basic subjective symptom is “positive”, more detailed questions are automatically generated. Finally, clear sentences regarding subjective symptoms are generated and output as a “finding report”.

This information is helpful to physicians and nurses in their health-counseling work. An artificial intelligence (AI) program based on “XpertRule” produces detailed questions which are generated by an interactive questionnaire using branching logical rules.

Monitoring diaphragm function in a patient with myasthenia gravis: electrical activity of the diaphragm vs. maximal inspiratory pressure

Background

Maximal inspiratory pressure (MIP) is used to assess respiratory muscle strength of patients with myasthenia gravis (MG) requiring ventilatory support. Electrical activity of the diaphragm (E-di) has been used to guide weaning.

Case presentation

The MIP and tidal volume/ΔE-di (the patient-to-ventilator breath contribution) were monitored in a 12-year-old girl with MG requiring ventilator support. The same ventilatory settings were maintained until extubation. During weaning, MIP increased slightly, but varied unpredictably. Tidal volume/ΔE-di decreased at a constant rate as muscle strength recovered.

Conclusion

In this patient with muscle weakness, E-di was a reliable tool to monitor weaning from mechanical ventilation.

Characterisation of a sucrose-independent in vitro biofilm model of supragingival plaque

OBJECTIVES

Sugar consumption has been decreasing in Japan, suggesting higher rates of sucrose-independent supragingival plaque formation. For developing an in vitro biofilm model of sucrose-independent supragingival plaque, this study aimed to investigate the compositions and functions on contributing to cariogenicity in comparison with sucrose-dependent biofilm.

MATERIALS AND METHODS

An in vitro multispecies biofilm containing Actinomyces naeslundii, Streptococcus gordonii, S. mutans, Veillonella parvula and Fusobacterium nucleatum was formed on 24-well plates in the absence or presence of 1% sucrose. Compositions were assessed by plate culture, scanning electron microscopy and confocal laser scanning microscopy after fluorescent in situ hybridisation or labelling of extracellular polymeric substances (EPS). Functions were assessed by acidogenicity, adherence strength and sensitivities to anticaries agents.

RESULTS

Although both biofilms exhibited a Streptococcus predominant bacterial composition, there were differences in bacterial and EPS compositions; in particular, little glucan EPS was observed in sucrose-independent biofilm. Compared with sucrose-dependent biofilm, acidogenicity, adherence strength and antimicrobial resistance of sucrose-independent biofilm were only slightly lower. However, dextranase degradation was substantially lower in sucrose-independent biofilm.

CONCLUSION

Our findings suggest that sucrose-independent biofilm may have cariogenicity as with sucrose-dependent biofilm. These in vitro models can help further elucidate plaque-induced caries aetiology and develop new anticaries agents.

Volume-controlled Ventilation Does Not Prevent Injurious Inflation during Spontaneous Effort

RATIONALE

Spontaneous breathing during mechanical ventilation increases transpulmonary pressure and Vt, and worsens lung injury. Intuitively, controlling Vt and transpulmonary pressure might limit injury caused by added spontaneous effort.

OBJECTIVES

To test the hypothesis that, during spontaneous effort in injured lungs, limitation of Vt and transpulmonary pressure by volume-controlled ventilation results in less injurious patterns of inflation.

METHODS

Dynamic computed tomography was used to determine patterns of regional inflation in rabbits with injured lungs during volume-controlled or pressure-controlled ventilation. Transpulmonary pressure was estimated by using esophageal balloon manometry [Pl(es)] with and without spontaneous effort. Local dependent lung stress was estimated as the swing (inspiratory change) in transpulmonary pressure measured by intrapleural manometry in dependent lung and was compared with the swing in Pl(es). Electrical impedance tomography was performed to evaluate the inflation pattern in a larger animal (pig) and in a patient with acute respiratory distress syndrome.

MEASUREMENTS AND MAIN RESULTS

Spontaneous breathing in injured lungs increased Pl(es) during pressure-controlled (but not volume-controlled) ventilation, but the pattern of dependent lung inflation was the same in both modes. In volume-controlled ventilation, spontaneous effort caused greater inflation and tidal recruitment of dorsal regions (greater than twofold) compared with during muscle paralysis, despite the same Vt and Pl(es). This was caused by higher local dependent lung stress (measured by intrapleural manometry). In injured lungs, esophageal manometry underestimated local dependent pleural pressure changes during spontaneous effort.

CONCLUSIONS

Limitation of Vt and Pl(es) by volume-controlled ventilation could not eliminate harm caused by spontaneous breathing unless the level of spontaneous effort was lowered and local dependent lung stress was reduced.