Effect of invasive mechanical ventilation on the diversity of the pulmonary microbiota.

Pulmonary microbial diversity may be influenced by biotic or abiotic conditions (e.g., disease, smoking, invasive mechanical ventilation (MV), etc.). Specially, invasive MV may trigger structural and physiological changes in both tissue and microbiota of lung, due to gastric and oral microaspiration, altered body posture, high O2 inhalation-induced O2 toxicity in hypoxemic patients, impaired airway clearance and ventilator-induced lung injury (VILI), which in turn reduce the diversity of the pulmonary microbiota and may ultimately lead to poor prognosis. Furthermore, changes in (local) O2 concentration can reduce the diversity of the pulmonary microbiota by affecting the local immune microenvironment of lung. In conclusion, systematic literature studies have found that invasive MV reduces pulmonary microbiota diversity, and future rational regulation of pulmonary microbiota diversity by existing or novel clinical tools (e.g., lung probiotics, drugs) may improve the prognosis of invasive MV treatment and lead to more effective treatment of lung diseases with precision.

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review.

COVID-19 pneumonia is associated with hypoxaemic respiratory failure, ranging from mild to severe. Because of the worldwide shortage of ICU beds, a relatively high number of patients with respiratory failure are receiving prolonged noninvasive respiratory support, even when their clinical status would have required invasive mechanical ventilation. There are few experimental and clinical data reporting that vigorous breathing effort during spontaneous ventilation can worsen lung injury and cause a phenomenon that has been termed patient self-inflicted lung injury (P-SILI). The aim of this narrative review is to provide an overview of P-SILI pathophysiology and the role of noninvasive respiratory support in COVID-19 pneumonia. Respiratory mechanics, vascular compromise, viscoelastic properties, lung inhomogeneity, work of breathing, and oesophageal pressure swings are discussed. The concept of P-SILI has been widely investigated in recent years, but controversies persist regarding its mechanisms. To minimise the risk of P-SILI, intensivists should better understand its underlying pathophysiology to optimise the type of noninvasive respiratory support provided to patients with COVID-19 pneumonia, and decide on the optimal timing of intubation for these patients.

Barotrauma during non-invasive ventilation for acute respiratory distress syndrome caused by COVID-19: a balance between risks and benefits.

Ventilatory support is vital for the management of severe forms of COVID-19. Non-invasive ventilation is often used in patients who do not meet criteria for intubation or when invasive ventilation is not available, especially in a pandemic when resources are limited. Despite non-invasive ventilation providing effective respiratory support for some forms of acute respiratory failure, data about its effectiveness in patients with viral-related pneumonia are inconclusive. Acute respiratory distress syndrome caused by severe acute respiratory syndrome-coronavirus 2 infection causes life-threatening respiratory failure, weakening the lung parenchyma and increasing the risk of barotrauma. Pulmonary barotrauma results from positive pressure ventilation leading to elevated transalveolar pressure, and in turn to alveolar rupture and leakage of air into the extra-alveolar tissue. This article reviews the literature regarding the use of non-invasive ventilation in patients with acute respiratory failure associated with COVID-19 and other epidemic or pandemic viral infections and the related risk of barotrauma.

The epidemiology and clinical outcomes of ventilator-associated events among 20,769 mechanically ventilated patients at intensive care units: an observational study.

BACKGROUND: Ventilator-associated pneumonia (VAP) is the most common hospital-acquired infection (HAI) in intensive care units (ICUs). Ventilator-associated event (VAE), a more objective definition, has replaced traditional VAP surveillance and is now widely used in the USA. However, the adoption outside the USA is limited. This study aims to describe the epidemiology and clinical outcomes of VAEs in China, based on a prospectively maintained registry. METHODS: An observational study was conducted using an ICU-HAI registry in west China. Patients that were admitted to ICUs and underwent mechanical ventilation (MV) between April 1, 2015, and December 31, 2018, were included. The characteristics and outcomes were compared between patients with and without VAEs. The rates of all VAEs dependent on different ICUs were calculated, and the pathogen distribution of patients with possible VAP (PVAP) was described. RESULTS: A total of 20,769 ICU patients received MV, accounting for 21,723 episodes of mechanical ventilators and 112,697 ventilator-days. In all, we identified 1882 episodes of ventilator-associated condition (VAC) events (16.7 per 1000 ventilator-days), 721 episodes of infection-related ventilator-associated complications (IVAC) events (6.4 per 1000 ventilator-days), and 185 episodes of PVAP events (1.64 per 1000 ventilator-days). The rates of VAC varied across ICUs with the highest incidence in surgical ICUs (23.72 per 1000 ventilator-days). The median time from the start of ventilation to the onset of the first VAC, IVAC, and PVAP was 5 (3-8), 5 (3-9), and 6 (4-13) days, respectively. The median length of hospital stays was 28.00 (17.00-43.00), 30.00 (19.00-44.00), and 30.00 (21.00-46.00) days for the three VAE tiers, which were all longer than that of patients without VAEs (16.00 [12.00-23.00]). The hospital mortality among patients with VAEs was more than three times of those with non-VAEs. CONCLUSIONS: VAE was common in ICU patients with ≥ 4 ventilator days. All tiers of VAEs were highly correlated with poor clinical outcomes, including longer ICU and hospital stays and increased risk of mortality. These findings highlight the importance of VAE surveillance and the development of new strategies to prevent VAEs.

Males Receive Low-Tidal Volume Component of Lung Protective Ventilation More Frequently than Females in the Emergency Department.

INTRODUCTION: Mechanical ventilation is a commonly performed procedure in the emergency department (ED). Approximately 240,000 patients per year receive mechanical ventilation in the ED representing 0.23% of ED visits. An ED-based trial published in 2017 showed that a bundle of interventions in mechanically ventilated patients, including low tidal volume ventilation, reduced the development of acute respiratory distress syndrome by nearly 50%. Prior literature has shown that as many as 40% of ED patients do not receive lung protective ventilation. Our goal was to determine whether differences exist between the percent of males vs females who are ventilated at ≥ 8 milliliters per kilogram (mL/kg) of predicted body weight. METHODS: We conducted this study at Temple University Hospital, a tertiary care center located in Philadelphia, Pennsylvania. This was a planned subgroup analysis of study looking at interventions to improve adherence to recommended tidal volume settings. We used a convenience sample of mechanically ventilated patients in our ED between September 1, 2017, and September 30, 2018. All adult patient > 18 years old were eligible for inclusion in the study. Our primary outcome measure was the number of patients who had initial tidal volumes set at > 8 mL/kg of predicted body weight. Our secondary outcome was the number of patients who had tidal volumes set at ≥ 8 mL/kg at 60 minutes after initiation of mechanical ventilation. RESULTS: A total of 130 patients were included in the final analysis. We found that significantly more females were initially ventilated with tidal volumes ≥ 8 mL/kg compared to men: 56% of females vs 9% of males (p=<0.001). Data was available for 107 patients (82%) who were in the ED at 60 minutes after initiation of mechanical ventilation. Again, a significantly larger percentage of females were ventilated with tidal volumes ≥ 8 mL/kg at 60 minutes: 56% of females vs 10% of males (p<0.001). CONCLUSION: The vast majority of tidal volumes ≥ 8 mL/kg during mechanical ventilation occurs in females. We suggest that objective measurements, such as a tape measure and tidal volume card, be used when setting tidal volumes for all patients, especially females.

Effects of a national quality improvement program on ICUs in China: a controlled pre-post cohort study in 586 hospitals.

INTRODUCTION: Patient safety and critical care quality remain a challenging issue in the ICU. However, the effects of the national quality improvement (QI) program remain unknown in China. METHODS: A national ICU QI program was implemented in a controlled cohort of 586 hospitals from 2016 to 2018. The effects of the QI program on critical care quality were comprehensively investigated. MAIN RESULTS: A total of 81,461,554 patients were enrolled in 586 hospitals, and 1,587,724 patients were admitted to the ICU over 3 years. In 2018, there was a significantly higher number of ICU beds (2016 vs. 2018: 10668 vs. 13,661, P = 0.0132) but a lower doctor-to-bed ratio (2016 vs. 2018: 0.64 (0.50, 0.83) vs. 0.60 (0.45, 0.75), P = 0.0016) and nurse-to-bed ratio (2016 vs. 2018: 2.00 (1.64, 2.50) vs. 2.00 (1.50, 2.40), P = 0.031) than in 2016. Continuous and significant improvements in the ventilator-associated pneumonia (VAP) incidence rate, microbiology detection rate before antibiotic use and deep vein thrombosis (DVT) prophylaxis rate were associated with the implementation of the QI program (VAP incidence rate (per 1000 ventilator-days), 2016 vs. 2017 vs. 2018: 11.06 (4.23, 22.70) vs. 10.20 (4.25, 23.94) vs. 8.05 (3.13, 17.37), P = 0.0002; microbiology detection rate before antibiotic use (%), 2016 vs. 2017 vs. 2018: 83.91 (49.75, 97.87) vs. 84.14 (60.46, 97.24) vs. 90.00 (69.62, 100), P < 0.0001; DVT prophylaxis rate, 2016 vs. 2017 vs. 2018: 74.19 (33.47, 96.16) vs. 71.70 (38.05, 96.28) vs. 83.27 (47.36, 97.77), P = 0.0093). Moreover, the 6-h SSC bundle compliance rates in 2018 were significantly higher than those in 2016 (6-h SSC bundle compliance rate, 2016 vs. 2018: 64.93 (33.55, 93.06) vs. 76.19 (46.88, 96.67)). A significant change trend was not found in the ICU mortality rate from 2016 to 2018 (ICU mortality rate (%), 2016 vs. 2017 vs. 2018: 8.49 (4.42, 14.82) vs. 8.95 (4.89, 15.70) vs. 9.05 (5.12, 15.80), P = 0.1075). CONCLUSIONS: The relationship between medical human resources and ICU overexpansion was mismatched during the past 3 years. The implementation of a national QI program improved ICU performance but did not reduce ICU mortality.

Changes in ventilator settings and ventilation-induced lung injury in burn patients-A systematic review.

OBJECTIVE: Ventilation strategies aiming at prevention of ventilator-induced lung injury (VILI), including low tidal volumes (VT) and use of positive end-expiratory pressures (PEEP) are increasingly used in critically ill patients. It is uncertain whether ventilation practices changed in a similar way in burn patients. Our objective was to describe applied ventilator settings and their relation to development of VILI in burn patients. DATA SOURCES: Systematic search of the literature in PubMed and EMBASE using MeSH, EMTREE terms and keywords referring to burn or inhalation injury and mechanical ventilation. STUDY SELECTION: Studies reporting ventilator settings in adult or pediatric burn or inhalation injury patients receiving mechanical ventilation during the ICU stay. DATA EXTRACTION: Two authors independently screened abstracts of identified studies for eligibility and performed data extraction. DATA SYNTHESIS: The search identified 35 eligible studies. VT declined from 14 ml/kg in studies performed before to around 8 ml/kg predicted body weight in studies performed after 2006. Low-PEEP levels (<10 cmH2O) were reported in 70% of studies, with no changes over time. Peak inspiratory pressure (PIP) values above 35 cmH2O were frequently reported. Nevertheless, 75% of the studies conducted in the last decade used limited maximum airway pressures (≤35 cmH2O) compared to 45% of studies conducted prior to 2006. Occurrence of barotrauma, reported in 45% of the studies, ranged from 0 to 29%, and was more frequent in patients ventilated with higher compared to lower airway pressures. CONCLUSION: This systematic review shows noticeable trends of ventilatory management in burn patients that mirrors those in critically ill non-burn patients. Variability in available ventilator data precluded us from drawing firm conclusions on the association between ventilator settings and the occurrence of VILI in burn patients.

Noninvasive Ventilation Device-Related Pressure Injury in a Children's Hospital.

BACKGROUND: Noninvasive ventilation (NIV) contributes to the development of pressure injury in a significant number of hospitalized patients. Pressure injuries contribute to increased length of hospital stay, pain, infection, and disfigurement. This study examined the relationship between NIV use and pressure injuries in hospitalized subjects. METHODS: We retrospectively reviewed all patients on NIV at a tertiary-care children's hospital over a 2-y period. We studied the relationship between the characteristics of NIV use and measures of pressure injury severity. RESULTS: A total of 255 subjects, mean ± SD age 11.3 ± 5.8 y with 343 episodes of NIV use were evaluated, 7.2% (25/343) of which were associated with pressure injury. In univariate analysis, the presence of pressure injury was associated with older age (P = .01), maximum leak (P = .01), 95th percentile leak (P = .01), the log duration of time on NIV until pressure injury formation (P = .01), and maximum inspiratory positive airway pressure level (P = .01). Maximum leak remained statistically significant after multivariable analysis. CONCLUSIONS: After multivariate analysis, only high mask leak was significantly associated with developing a pressure injury. Identifying risk factors that correlate with NIV device-related hospital acquired pressure injuries in children can direct procedures to prevent pressure injury in hospitalized children at high risk.

The time-controlled adaptive ventilation protocol: mechanistic approach to reducing ventilator-induced lung injury.

Airway pressure release ventilation (APRV) is a ventilator mode that has previously been considered a rescue mode, but has gained acceptance as a primary mode of ventilation. In clinical series and experimental animal models of extrapulmonary acute respiratory distress syndrome (ARDS), the early application of APRV was able to prevent the development of ARDS. Recent experimental evidence has suggested mechanisms by which APRV, using the time-controlled adaptive ventilation (TCAV) protocol, may reduce lung injury, including: 1) an improvement in alveolar recruitment and homogeneity; 2) reduction in alveolar and alveolar duct micro-strain and stress-risers; 3) reduction in alveolar tidal volumes; and 4) recruitment of the chest wall by combating increased intra-abdominal pressure. This review examines these studies and discusses our current understanding of the pleiotropic mechanisms by which TCAV protects the lung. APRV set according to the TCAV protocol has been misunderstood and this review serves to highlight the various protective physiological and mechanical effects it has on the lung, so that its clinical application may be broadened.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review.

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.

Adoption of Lung Protective ventilation IN patients undergoing Emergency laparotomy: the ALPINE study. A prospective multicentre observational study.

BACKGROUND: Emergency abdominal surgery is associated with a high risk of postoperative pulmonary complications (PPCs). The primary aim of this study was to determine whether patients undergoing emergency laparotomy are ventilated using a lung-protective ventilation strategy employing tidal volume ≤8 ml kg-1 ideal body weight-1, PEEP >5 cm H2O, and recruitment manoeuvres. The secondary aim was to investigate the association between ventilation factors (lung-protective ventilation strategy, intraoperative FiO2, and peak inspiratory pressure) and the occurrence of PPCs. METHODS: Data were collected prospectively in 28 hospitals across London as part of routine National Emergency Laparotomy Audit (NELA). Patients were followed for 7 days. Complications were defined according to the European Perioperative Clinical Outcome definition. RESULTS: Data were collected from 568 patients. The median [inter-quartile range (IQR)] tidal volume observed was 500 ml (450-540 ml), corresponding to a median tidal volume of 8 ml kg-1 ideal body weight-1 (IQR: 7.2-9.1 ml). A lung-protective ventilation strategy was employed in 4.9% (28/568) of patients, and was not protective against the occurrence of PPCs in the multivariable analysis (hazard ratio=1.06; P=0.69). Peak inspiratory pressure of <30 cm H2O was protective against development of PPCs (hazard ratio=0.46; confidence interval: 0.30-0.72; P=0.001). Median FiO2 was 0.5 (IQR: 0.44-0.53), and an increase in FiO2 by 5% increased the risk of developing a PPC by 8% (2.6-14.1%; P=0.008). CONCLUSIONS: Both intraoperative peak inspiratory pressure and FiO2 are independent factors significantly associated with development of a postoperative pulmonary complication in emergency laparotomy patients. Further studies are required to identify causality and to demonstrate if their manipulation could lead to better clinical outcomes.

Using Objective Fluid Balance Data to Identify Pulmonary Edema in Subjects With Ventilator-Associated Events.

BACKGROUND: A ventilator-associated events (VAEs) algorithm was developed to detect events in mechanically ventilated subjects using objective parameters, and we aimed to use objective data of fluid balance to identify pulmonary edema-associated VAEs. METHODS: This single-center retrospective cohort study was conducted in a medical ICU and enrolled all mechanically ventilated patients between July 2016 and June 2017. Electronic medical records were reviewed to obtain data regarding ventilator-associated conditions (VACs), infection-related ventilator-associated complications (IVACs), possible ventilator-associated pneumonia (VAP), and traditionally defined VAP. RESULTS: Of the 1,158 mechanically ventilated subjects, 85 (7.3%) subjects developed VAEs with a corresponding incidence rate of 7.7 events per 1,000 ventilator days. Among the 85 subjects with VAEs, 52 (61.2%) were classified as IVACs, while 23 (27.1%) had possible VAP. Notably, pulmonary edema was the main etiology (29.0%) for VAEs in the 62 subjects with non-possible VAP VAEs. Compared with those without pulmonary edema, subjects with pulmonary edema had a higher positive fluid balance 2 d before (+1,228 vs +173.5 mL, P = .005) and 1 d before (+1,622 vs +313 mL, P = .002) the diagnosis of VAE. In the multivariate logistic regression analysis (adjusted odds ratio [OR]) adjusted for potential confounders, an older age (adjusted OR 1.072, 95% CI 1.001-1.147), receiving renal replacement therapy (adjusted OR 8.906, 95% CI 1.454-54.558), and a positive cumulative difference between fluid balance 2 d and 1 d before VAE indexing (adjusted OR 1.527 per L positive, 95% CI 1.153-2.023) were independently associated with pulmonary edema in subjects with VAEs. CONCLUSION: These findings provide epidemiological evidence of VAEs in a medical ICU and showed that fluid balance may be used to identify pulmonary edema-associated VAEs. Further studies are warranted to validate and translate these findings into an automated surveillance system for VAEs.

Real-Time, Automated Detection of Ventilator-Associated Events: Avoiding Missed Detections, Misclassifications, and False Detections Due to Human Error.

OBJECTIVETo validate a system to detect ventilator associated events (VAEs) autonomously and in real time.DESIGNRetrospective review of ventilated patients using a secure informatics platform to identify VAEs (ie, automated surveillance) compared to surveillance by infection control (IC) staff (ie, manual surveillance), including development and validation cohorts.SETTINGThe Massachusetts General Hospital, a tertiary-care academic health center, during January-March 2015 (development cohort) and January-March 2016 (validation cohort).PATIENTSVentilated patients in 4 intensive care units.METHODSThe automated process included (1) analysis of physiologic data to detect increases in positive end-expiratory pressure (PEEP) and fraction of inspired oxygen (FiO2); (2) querying the electronic health record (EHR) for leukopenia or leukocytosis and antibiotic initiation data; and (3) retrieval and interpretation of microbiology reports. The cohorts were evaluated as follows: (1) manual surveillance by IC staff with independent chart review; (2) automated surveillance detection of ventilator-associated condition (VAC), infection-related ventilator-associated complication (IVAC), and possible VAP (PVAP); (3) senior IC staff adjudicated manual surveillance-automated surveillance discordance. Outcomes included sensitivity, specificity, positive predictive value (PPV), and manual surveillance detection errors. Errors detected during the development cohort resulted in algorithm updates applied to the validation cohort.RESULTSIn the development cohort, there were 1,325 admissions, 479 ventilated patients, 2,539 ventilator days, and 47 VAEs. In the validation cohort, there were 1,234 admissions, 431 ventilated patients, 2,604 ventilator days, and 56 VAEs. With manual surveillance, in the development cohort, sensitivity was 40%, specificity was 98%, and PPV was 70%. In the validation cohort, sensitivity was 71%, specificity was 98%, and PPV was 87%. With automated surveillance, in the development cohort, sensitivity was 100%, specificity was 100%, and PPV was 100%. In the validation cohort, sensitivity was 85%, specificity was 99%, and PPV was 100%. Manual surveillance detection errors included missed detections, misclassifications, and false detections.CONCLUSIONSManual surveillance is vulnerable to human error. Automated surveillance is more accurate and more efficient for VAE surveillance.Infect Control Hosp Epidemiol 2018;826-833.

High-Fat Feeding Protects Mice From Ventilator-Induced Lung Injury, Via Neutrophil-Independent Mechanisms.

OBJECTIVE: Obesity has a complex impact on acute respiratory distress syndrome patients, being associated with increased likelihood of developing the syndrome but reduced likelihood of dying. We propose that such observations are potentially explained by a model in which obesity influences the iatrogenic injury that occurs subsequent to intensive care admission. This study therefore investigated whether fat feeding protected mice from ventilator-induced lung injury. DESIGN: In vivo study. SETTING: University research laboratory. SUBJECTS: Wild-type C57Bl/6 mice or tumor necrosis factor receptor 2 knockout mice, either fed a high-fat diet for 12-14 weeks, or age-matched lean controls. INTERVENTIONS: Anesthetized mice were ventilated with injurious high tidal volume ventilation for periods up to 180 minutes. MEASUREMENTS AND MAIN RESULTS: Fat-fed mice showed clear attenuation of ventilator-induced lung injury in terms of respiratory mechanics, blood gases, and pulmonary edema. Leukocyte recruitment and activation within the lungs were not significantly attenuated nor were a host of circulating or intra-alveolar inflammatory cytokines. However, intra-alveolar matrix metalloproteinase activity and levels of the matrix metalloproteinase cleavage product soluble receptor for advanced glycation end products were significantly attenuated in fat-fed mice. This was associated with reduced stretch-induced CD147 expression on lung epithelial cells. CONCLUSIONS: Consumption of a high-fat diet protects mice from ventilator-induced lung injury in a manner independent of neutrophil recruitment, which we postulate instead arises through blunted up-regulation of CD147 expression and subsequent activation of intra-alveolar matrix metalloproteinases. These findings may open avenues for therapeutic manipulation in acute respiratory distress syndrome and could have implications for understanding the pathogenesis of lung disease in obese patients.

The endothelial glycocalyx and perioperative lung injury.

PURPOSE OF REVIEW: Ventilator-induced lung injury is a major contributor to perioperative lung injury. The end-expiratory lung volume, regional lung overdistension, and tidal recruitment are known to be the main factors causing subsequent alveolar damage and inflammation. The alveolar-capillary membrane including the endothelial glycocalyx as an integral part of the vascular endothelium seems to play a major role in different kinds of lung injury. RECENT FINDINGS: Recent studies underline the pivotal importance of the endothelial glycocalyx in lung injury. The glycocalyx regulates and modulates plasma endothelial cell interactions. Several triggers are known to deteriorate the gylcocalyx such as fluid overload, ischemia, and TRALI. The clinical manifestation is inflammation, capillary leak, and edema formation. Breakdown of the endothelial gylcocalyx is of gaining importance in the context of one-lung ventilation, known to be a major risk factor for postoperative lung injury. Studies suggest that volatile anesthetics may have a protective influence on the endothelial glycocalyx of pulmonary capillaries and reduce ischemia-reperfusion injury. This might be of clinical relevance for postoperative outcome. SUMMARY: This review focuses on the involvement of the pulmonary endothelial glycocalyx in the context of perioperative lung injury. The pathophysiological mechanisms and trigger factors of glycocalyx deterioration are discussed, and prevention strategies are taken into consideration.

Use of a Shared Canister Protocol for the Delivery of Metered-Dose Inhalers in Mechanically Ventilated Subjects.

BACKGROUND: Mechanically ventilated patients often need bronchodilators administered via a metered-dose inhaler (MDI). Unfortunately, there are no data examining the impact of shared canister delivery of MDI therapy in mechanically ventilated patients. METHODS: A prospective trial was conducted with subjects assigned to shared canister MDI therapy or single-patient canister MDI therapy. Outcomes assessed were occurrence of ventilator-associated pneumonia (VAP), hospital mortality, length of stay, ventilator-associated events, and MDI costs. RESULTS: Among 486 screened patients, 353 were included for analysis of which 201 (56.9%) received shared canister MDI therapy and 152 (43.1%) received single-patient canister therapy. VAP (7.0% vs 4.6%, P = .35), hospital mortality (21.9% vs 20.4%, P = .73), and ventilator days (median [interquartile range] 3.1 [0.9-7.5] d vs 2.7 [1.2-7.1] d, P = .62) were similar between the shared canister and single-patient canister groups. We did not observe clinically important differences for ventilator-associated events between study groups in our logistic regression analysis (P = .07). There was a savings of $217/subject in the shared canister group due to the use of 299 fewer MDIs. CONCLUSIONS: Our study found that shared canister MDI therapy compared with single-patient MDI use was associated with a significant cost savings and similar rates of VAP, hospital mortality, and length of stay but a greater prevalence of ventilator-associated events. This finding suggests that shared canister delivery of MDIs may be a cost-effective practice in mechanically ventilated patients. Based on our findings, further studies examining the overall safety of shared canister use in mechanically ventilated patients seem warranted before recommending their routine use. (ClinicalTrials.gov registration NCT01935388.).

Spontaneous Effort During Mechanical Ventilation: Maximal Injury With Less Positive End-Expiratory Pressure.

OBJECTIVES: We recently described how spontaneous effort during mechanical ventilation can cause "pendelluft," that is, displacement of gas from nondependent (more recruited) lung to dependent (less recruited) lung during early inspiration. Such transfer depends on the coexistence of more recruited (source) liquid-like lung regions together with less recruited (target) solid-like lung regions. Pendelluft may improve gas exchange, but because of tidal recruitment, it may also contribute to injury. We hypothesize that higher positive end-expiratory pressure levels decrease the propensity to pendelluft and that with lower positive end-expiratory pressure levels, pendelluft is associated with improved gas exchange but increased tidal recruitment. DESIGN: Crossover design. SETTING: University animal research laboratory. SUBJECTS: Anesthetized landrace pigs. INTERVENTIONS: Surfactant depletion was achieved by saline lavage in anesthetized pigs, and ventilator-induced lung injury was produced by ventilation with high tidal volume and low positive end-expiratory pressure. Ventilation was continued in each of four conditions: positive end-expiratory pressure (low or optimized positive end-expiratory pressure after recruitment) and spontaneous breathing (present or absent). Tidal recruitment was assessed using dynamic CT and regional ventilation/perfusion using electric impedance tomography. Esophageal pressure was measured using an esophageal balloon manometer. MEASUREMENTS AND RESULTS: Among the four conditions, spontaneous breathing at low positive end-expiratory pressure not only caused the largest degree of pendelluft, which was associated with improved ventilation/perfusion matching and oxygenation, but also generated the greatest tidal recruitment. At low positive end-expiratory pressure, paralysis worsened oxygenation but reduced tidal recruitment. Optimized positive end-expiratory pressure decreased the magnitude of spontaneous efforts (measured by esophageal pressure) despite using less sedation, from -5.6 ± 1.3 to -2.0 ± 0.7 cm H2O, while concomitantly reducing pendelluft and tidal recruitment. No pendelluft was observed in the absence of spontaneous effort. CONCLUSIONS: Spontaneous effort at low positive end-expiratory pressure improved oxygenation but promoted tidal recruitment associated with pendelluft. Optimized positive end-expiratory pressure (set after lung recruitment) may reverse the harmful effects of spontaneous breathing by reducing inspiratory effort, pendelluft, and tidal recruitment.

Intraoperative mechanical ventilation for the pediatric patient.

Invasive mechanical ventilation is required when children undergo general anesthesia for any procedure. It is remarkable that one of the most practiced interventions such as pediatric mechanical ventilation is hardly supported by any scientific evidence but rather based on personal experience and data from adults, especially as ventilation itself is increasingly recognized as a harmful intervention that causes ventilator-induced lung injury. The use of low tidal volume and higher levels of positive end-expiratory pressure became an integral part of lung-protective ventilation following the outcomes of clinical trials in critically ill adults. This approach has been readily adopted in pediatric ventilation. However, a clear association between tidal volume and mortality has not been ascertained in pediatrics. In fact, experimental studies have suggested that young children might be less susceptible to ventilator-induced lung injury. As such, no recommendations on optimal lung-protective ventilation strategy in children with or without lung injury can be made.