Acute respiratory distress syndrome: frequency, clinical course, and costs of care

Early time-course of respiratory mechanics, mechanical power and gas exchange in ARDS patients

PURPOSE

To describe the clinical course of ARDS during the first three days of mechanical ventilation, to compare ventilatory setting, respiratory mechanics and gas exchange variables collected during the first three days of mechanical ventilation between patients who survived and died during intensive care unit (ICU) stay and to investigate the variables associated with mortality at ICU admission and throughout the first three days of mechanical ventilation.

MATERIALS AND METHODS

Prospective observational study. Mechanically ventilated ARDS patients were studied at ICU admission and for the following three days. Univariate logistic regression models were performed for PaO2/FiO2 ratio, driving pressure and alveolar dead space fraction and for mechanical power and mechanical power ratio.

RESULTS

Mechanical power ratio was higher in non survivors at ICU admission and over time; PaO2/FiO2 ratio was higher in survivors with a similar behavior over time in the two groups while alveolar dead space fraction was similar at ICU admission and over time between groups. Mechanical power ratio was the only physiological variable which remained consistently associated with ICU mortality throughout the study.

CONCLUSIONS

The alteration in oxygenation, dead space, and mechanical power ratio should be assessed not at intensive care admission, but during the first days of mechanical ventilation to better predict outcome.

The PANDORA Study: Prevalence and Outcome of Acute Hypoxemic Respiratory Failure in the Pre-COVID-19 Era

OBJECTIVES:

To establish the epidemiological characteristics, ventilator management, and outcomes in patients with acute hypoxemic respiratory failure (AHRF), with or without acute respiratory distress syndrome (ARDS), in the era of lung-protective mechanical ventilation (MV).

DESIGN:

A 6-month prospective, epidemiological, observational study.

SETTING:

A network of 22 multidisciplinary ICUs in Spain.

PATIENTS:

Consecutive mechanically ventilated patients with AHRF (defined as Pao₂/Fio₂ ≤ 300 mm Hg on positive end-expiratory pressure [PEEP] ≥ 5 cm H₂O and Fio₂ ≥ 0.3) and followed-up until hospital discharge.

INTERVENTIONS:

None.

MEASUREMENTS AND MAIN RESULTS:

Primary outcomes were prevalence of AHRF and ICU mortality. Secondary outcomes included prevalence of ARDS, ventilatory management, and use of adjunctive therapies. During the study period, 9,803 patients were admitted: 4,456 (45.5%) received MV, 1,271 (13%) met AHRF criteria (1,241 were included into the study: 333 [26.8%] met Berlin ARDS criteria and 908 [73.2%] did not). At baseline, tidal volume was 6.9 ± 1.1 mL/kg predicted body weight, PEEP 8.4 ± 3.1 cm H₂O, Fio₂ 0.63 ± 0.22, and plateau pressure 21.5 ± 5.4 cm H₂O. ARDS patients received higher Fio₂ and PEEP than non-ARDS (0.75 ± 0.22 vs 0.59 ± 0.20 cm H₂O and 10.3 ± 3.4 vs 7.7 ± 2.6 cm H₂O, respectively [p < 0.0001]). Adjunctive therapies were rarely used in non-ARDS patients. Patients without ARDS had higher ventilator-free days than ARDS (12.2 ± 11.6 vs 9.3 ± 9.7 d; p < 0.001). All-cause ICU mortality was similar in AHRF with or without ARDS (34.8% [95% CI, 29.7–40.2] vs 35.5% [95% CI, 32.3–38.7]; p = 0.837).

CONCLUSIONS:

AHRF without ARDS is a very common syndrome in the ICU with a high mortality that requires specific studies into its epidemiology and ventilatory management. We found that the prevalence of ARDS was much lower than reported in recent observational studies.

The Cost of ARDS: A Systematic Review

BACKGROUND

ARDS is an inflammatory condition of the lungs and is a common condition in adult ICUs. The resources required and costs of care for patients with ARDS are significant because of the severity of the illness and extended ICU lengths of stay.

RESEARCH QUESTION

What are the costs associated with ARDS?

STUDY DESIGN AND METHODS

We systematically searched the literature through April 29, 2021, for articles relevant to ARDS and costs. MEDLINE, Embase, Central, and EconLit databases were searched, and articles that reported on cost data from an original publication in adult patients with ARDS were included. Two authors independently assessed articles for inclusion and extracted data elements related to costs, methodology, health-care system type, economic perspective, and clinical data. Publication quality was assessed using a modified version of the Quality of Health Economic Studies Instrument.

RESULTS

Four thousand six hundred sixty-three publications were found, of which 110 were included for full-text review (κ = 0.72). A total of 22 publications (49,483 patients) were suitable for data extraction. The publications represented a broad range of health-care systems, economic perspectives, costing methodology, and time frames. Mean inpatient costs ranged from $8,476 (2021 US dollars [USD]) to $547,974 (2021 USD) and were highest in publications of lower quality and in American health systems and were associated with trauma cohorts. Outpatient costs were highest in publications with higher readmission rates, longer durations of follow-up, and in American health systems.

INTERPRETATION

A wide range of costing data is available for ARDS. A comprehensive synthesis of this literature frames the reasons for this and allows estimates to reflect the context in which they were assessed. This information will be of value to researchers and administrators interested in the economics of caring for patients with ARDS.

TRIAL REGISTRY

PROSPERO; No.: CRD42020192487.

SSRIs: Applications in inflammatory lung disease and implications for COVID-19

Selective serotonin reuptake inhibitors (SSRIs) have anti-inflammatory properties that may have clinical utility in treating severe pulmonary manifestations of COVID-19. SSRIs exert anti-inflammatory effects at three mechanistic levels: (a) inhibition of proinflammatory transcription factor activity, including NF-κB and STAT3; (b) downregulation of lung tissue damage and proinflammatory cell recruitment via inhibition of cytokines, including IL-6, IL-8, TNF-α, and IL-1β; and (c) direct suppression inflammatory cells, including T cells, macrophages, and platelets. These pathways are implicated in the pathogenesis of COVID-19. In this review, we will compare the pathogenesis of lung inflammation in pulmonary diseases including COVID-19, ARDS, and chronic obstructive pulmonary disease (COPD), describe the anti-inflammatory properties of SSRIs, and discuss the applications of SSRIS in treating COVID-19-associated inflammatory lung disease.

National incidence rate and related mortality for acute respiratory distress syndrome in France

INTRODUCTION

Despite many efforts to improve mechanical ventilation strategies and the use of rescue strategies, ARDS-related mortality remains high. The primary objective of this study was to determine the incidence and 90-day mortality of ARDS patients admitted to all French ICUs following the introduction of the Berlin definition of ARDS.

PATIENTS AND METHODS

The data source for this nationwide cohort study was the French national hospital database (Programme de Médicalisation des Systèmes d'Information (PMSI)), which systematically collects administrative and medical information related to all patients hospitalised and hospital stays. Patient-level data were obtained from the PMSI database for all patients admitted to an ICU from the 1^st of January 2017, through the 31^st of December 2017. The inclusion criteria were as follows: ICU patients ≥ 18 years old with at least one International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10) diagnosis code of J80 (ARDS), either as a primary diagnosis or a secondary diagnosis, during their ICU stay.

RESULTS

A total of 12,846 ICU adult patients with ARDS were included. The crude incidence of ARDS was 24.6 per 100,000 person-years, varying with age from 6.7 per 100,000 person-years for those 18 through 40 years of age to 51.9 per 100,000 person-years for those 68 through 76 years of age. The in-hospital mortality rate was 51.1%. Day-90 mortality (day-1 being the ICU admission) was 51.2% and increased with age from 29.0% for patients 18 through 40 years of age to 69.3% for patients 77 years of age or older (p < 0.001). Only 53.9% of the survivors were transferred home directly after hospital discharge.

CONCLUSIONS

The incidence and mortality of ARDS in adults in France are higher than that generally reported in other countries.

Prevalence and Outcomes of Acute Hypoxaemic Respiratory Failure in Wales: The PANDORA-WALES Study

BACKGROUND

We aimed to identify the prevalence of acute hypoxaemic respiratory failure (AHRF) in the intensive care unit (ICU) and its associated mortality. The secondary aim was to describe ventilatory management as well as the use of rescue therapies.

METHODS

Multi-centre prospective study in nine hospitals in Wales, UK, over 2-month periods. All patients admitted to an ICU were screened for AHRF and followed-up until discharge from the ICU. Data were collected from patient charts on patient demographics, clinical characteristics, management and outcomes.

RESULTS

Out of 2215 critical care admissions, 886 patients received mechanical ventilation. A total of 197 patients met inclusion criteria and were recruited. Seventy (35.5%) were non-survivors. Non-survivors were significantly older, had higher SOFA scores and received more vasopressor support than survivors. Twenty-five (12.7%) patients who fulfilled the Berlin definition of acute respiratory distress syndrome (ARDS) during the ICU stay without impact on overall survival. Rescue therapies were rarely used. Analysis of ventilation showed that median Vt was 7.1 mL/kg PBW (IQR 5.9-9.1) and 21.3% of patients had optimal ventilation during their ICU stay.

CONCLUSIONS

One in four mechanically ventilated patients have AHRF. Despite advances of care and better, but not optimal, utilisation of low tidal volume ventilation, mortality remains high.

Validation of age, PaO2/FlO2 and plateau pressure score in Korean patients with acute respiratory distress syndrome: a retrospective cohort study

Background

A predictive scoring system for acute respiratory distress syndrome (ARDS) patients, which incorporates age, PaO₂/FlO₂, and plateau pressure, APPS, was developed recently. It was validated externally in a Caucasian population but has not been studied in Asian populations. The aim of this study was to validate APPS in Korean ARDS patients.

Methods

We retrospectively reviewed the medical records of patients who were diagnosed with ARDS using the Berlin criteria and admitted to the medical ICU at Seoul National University Hospital from January 2015 to December 2016. The validation of the APPS was performed by evaluating its calibration and predictive accuracy. Its calibration was plotted and quantified using the Hosmer–Lemeshow test. Its predictive accuracy was assessed by calculating the area under the receiver operating characteristics (AUC–ROC) curve.

Results

A total of 116 patients were analyzed, 32 of whom survived. Of the 116 patients, 11 (9.5%) were classified as APPS grade 1 (score 3–4), 88 (75.9%) as grade 2 (score 5–7) and 17 (14.6%) as grade 3 (score 8–9). In-hospital mortality was 27.3% for grade 1, 73.9% for grade 2 and 94.1% for grade 3 (P for trend < 0.001). The APPS was well calibrated (Hosmer–Lemeshow test, P = 0.578) and its predictive accuracy was acceptable (AUC–ROC 0.704, 95% confidence interval 0.599–0.809).

Conclusions

The APPS predicted in-hospital mortality in Korean patients with ARDS with similar power to its application in a Western population and with acceptable predictive accuracy.

Trial registration

Retrospectively registered.

Pharmacological Effects of Verticine: Current Status

Verticine is the major bioactive constituent of Fritillaria as a kind of Traditional Chinese Medicine. Pharmacological researches have reported various benefits of verticine, including anticancer, anti-inflammatory, protecting against acute lung injury, tracheobronchial relaxation, antitussive, expectorant, sedative, and analgesic activities, in addition to inhibiting proliferation of cultured orbital fibroblast, angiotensin converting enzyme (ACE), and acetylcholinesterase (AChE) and inhibiting hERG potassium channels. The underlying mechanisms of verticine are still under investigation. This review will comprehensively summarize the metabolism, biological activities, and possible mechanism of verticine.

Severe acute respiratory distress syndrome (ARDS) induced by human adenovirus B21: Report on 2 cases and literature review

Severe pneumonia and ARDS caused by human adenovirus B21 infections (HAdV-B21) is a rare, but a devastating disease with rapid progression to multiorgan failure and death. However, only a few cases were reported so far.

Infections appear associated with increased disease severity and higher mortality in infected critically ill patients. Possible factors contributing to infection are underlying psychiatric disease resulting in institutionalization of respective patients, and polytoxicomania. Controlled data on the therapy of severe adenovirus infections are lacking and remains experimental.

In conclusion, data on HAdV-B21 infections causing severe pneumonia or ARDS are scarce. Controlled clinical trials on the therapy of adenovirus pneumonia are non existent and thus there is no established therapy so far. ICU physicians should be aware of this potentially devastating disease and further studies are needed.

Factors determining outcomes in adult patient undergoing mechanical ventilation: A "real-world" retrospective study in an Indian Intensive Care Unit

Background:

Characteristics of patients admitted to intensive care units with respiratory failure (RF) and undergoing mechanical ventilation (MV) have been described for particular indications and diseases, but there are few studies in the general Intensive Care Unit (ICU) population and even lesser from developing countries.

Objective:

This study aims to study clinical characteristics, outcomes, and factors affecting outcomes in adult patients with RF on MV admitted to ICU.

Methods:

A retrospective study of medical records of all patients admitted to ICU between January 1, 2015, and March 31, 2016. Patients receiving MV for more than 6 h were included in the study. Patients younger than 12 years were excluded. Data were recorded of all patients receiving MV during this period regarding demographics, indications for MV, type and characteristics of ventilation, concomitant complications and treatment, and outcomes. Data were recorded at the initiation of MV and daily all throughout the course of MV. The main outcome measure was all-cause mortality at the end of ICU stay.

Results:

Of the 500 patients admitted to the ICU during the period of the study, a total of 122 patients received MV (and were included in study) for mean (standard deviation [SD]) duration of 4 (3.4) days. The mean (SD) stay in ICU and hospital was 4.49 (3.52) and 6.4 (3.6), respectively. Overall mortality for the unselected general ICU patients on MV was 67.21% while that for ARDS patients was 76.1%. The main factors independently associated with increased mortality were (i) pre-MV factors: age, Apache II scores, heart failure (odds ratio [OR], 1.42; 95% confidence interval [CI], 0.54–3.73; P < 0.001); (ii) patient management factors: positive end-expiratory pressure (OR, 2.69; 95% CI, 0.84–8.61; P < 0.001); (iii) Factors occurring over the course of MV: PaO₂/FiO₂ ratio < 100 (OR, 1.66; 95% CI, 0.67–4.11; P < 0.001) and development of renal failure (OR, 2.33; 95% CI, 2.05–2.42; P < 0.001) and hepatic failure (OR, 2.07; 95% CI, 1.91–2.24; P < 0.001) after initiation of MV.

Conclusions:

Outcomes of patients undergoing MV are dependent on various factors (including patient demographics, nature of associated morbidity, characteristics of the MV received, and conditions developing over course of MV) and these factors may be present before or develop after initiation of MV.

Advances in Stem Cell and Cell-Based Gene Therapy Approaches for Experimental Acute Lung Injury: A Review of Preclinical Studies

Given the failure of pharmacological interventions in acute respiratory distress syndrome (ARDS), researchers have been actively pursuing novel strategies to treat this devastating, life-threatening condition commonly seen in the intensive care unit. There has been considerable research on harnessing the reparative properties of stem and progenitor cells to develop more effective therapeutic approaches for respiratory diseases with limited treatment options, such as ARDS. This review discusses the preclinical literature on the use of stem and progenitor cell therapy and cell-based gene therapy for the treatment of preclinical animal models of acute lung injury (ALI). A variety of cell types that have been used in preclinical models of ALI, such as mesenchymal stem cells, endothelial progenitor cells, and induced pluripotent stem cells, were evaluated. At present, two phase I trials have been completed and one phase I/II clinical trial is well underway in order to translate the therapeutic benefit gleaned from preclinical studies in complex animal models of ALI to patients with ARDS, paving the way for what could potentially develop into transformative therapy for critically ill patients. As we await the results of these early cell therapy trials, future success of stem cell therapy for ARDS will depend on selection of the most appropriate cell type, route and timing of cell delivery, enhancing effectiveness of cells (i.e., potency), and potentially combining beneficial cells and genes (cell-based gene therapy) to maximize therapeutic efficacy. The experimental models and scientific methods exploited to date have provided researchers with invaluable knowledge that will be leveraged to engineer cells with enhanced therapeutic capabilities for use in the next generation of clinical trials.

The Effect of ARDS on Survival: Do Patients Die From ARDS or With ARDS?

OBJECTIVE:

To investigate the contribution of acute respiratory distress syndrome (ARDS) in of itself to mortality among ventilated patients.

DESIGN AND SETTING:

A longitudinal retrospective study of ventilated intensive care unit (ICU) patients.

PATIENTS:

The analysis included patients ventilated for more than 48 hours. Patients were classified as having ARDS on admission (early-onset ARDS), late-onset ARDS (ARDS not present during the first 24 hours of admission), or no ARDS. Primary outcomes were mortality at 28 days, and secondary outcomes were 2-year mortality rate from ICU admission.

RESULTS:

A total of 1411 ventilated patients were enrolled: 41% had ARDS on admission, 28.5% developed ARDS during their ICU stay, and 30.5% did not meet the ARDS criteria prior to ICU discharge or death. The non-ARDS group was used as the control. We also divided the cohort based on the severity of ARDS. After adjusting for covariates, mortality risk at 28 days was not significantly different among the different groups. Both early- and late-onset ARDS as well as the severity of ARDS were found to be significant risk factors for 2 years from ICU survival.

CONCLUSION:

Among patients who were ventilated on ICU admission, neither the presence, the severity, or the timing of ARDS contribute independently to the short-term mortality risk. However, acute respiratory distress syndrome does contribute significantly to 2-year mortality risk. This suggests that patients may not die acutely from ARDS itself but rather from the primary disease, and during the acute phase of ARDS, clinicians should focus on improving treatment strategies for the diseases that led to ARDS.

National survey of outcomes and practices in acute respiratory distress syndrome in Singapore

INTRODUCTION

In the past 20 years, our understanding of acute respiratory distress syndrome (ARDS) management has improved, but the worldwide incidence and current outcomes are unclear. The reported incidence is highly variable, and no studies specifically characterise ARDS epidemiology in Asia. This observation study aims to determine the incidence, mortality and management practices of ARDS in a high income South East Asian country.

METHODS

We conducted a prospective, population based observational study in 6 public hospitals. During a one month period, we identified all ARDS patients admitted to public hospital intensive care units (ICU) in Singapore, according to the Berlin definition. Demographic information, clinical management data and ICU outcome data was collected.

RESULTS

A total of 904 adult patients were admitted to ICU during the study period and 15 patients met ARDS criteria. The unadjusted incidence of ARDS was 4.5 cases per 100,000 population, accounting for 1.25% of all ICU patients. Most patients were male (75%), Chinese (62%), had pneumonia (73%), and were admitted to a Medical ICU (56%). Management strategies varied across all ICUs. In-hospital mortality was 40% and median length of ICU stay was 7 days.

CONCLUSION

The incidence of ARDS in a developed S.E Asia country is comparable to reported rates in European studies.

Epidemiological characteristics, practice of ventilation, and clinical outcome in patients at risk of acute respiratory distress syndrome in intensive care units from 16 countries (PRoVENT): an international, multicentre, prospective study

BACKGROUND

Scant information exists about the epidemiological characteristics and outcome of patients in the intensive care unit (ICU) at risk of acute respiratory distress syndrome (ARDS) and how ventilation is managed in these individuals. We aimed to establish the epidemiological characteristics of patients at risk of ARDS, describe ventilation management in this population, and assess outcomes compared with people at no risk of ARDS.

METHODS

PRoVENT (PRactice of VENTilation in critically ill patients without ARDS at onset of ventilation) is an international, multicentre, prospective study undertaken at 119 ICUs in 16 countries worldwide. All patients aged 18 years or older who were receiving mechanical ventilation in participating ICUs during a 1-week period between January, 2014, and January, 2015, were enrolled into the study. The Lung Injury Prediction Score (LIPS) was used to stratify risk of ARDS, with a score of 4 or higher defining those at risk of ARDS. The primary outcome was the proportion of patients at risk of ARDS. Secondary outcomes included ventilatory management (including tidal volume [V_T] expressed as mL/kg predicted bodyweight [PBW], and positive end-expiratory pressure [PEEP] expressed as cm H₂O), development of pulmonary complications, and clinical outcomes. The PRoVENT study is registered at ClinicalTrials.gov, NCT01868321. The study has been completed.

FINDINGS

Of 3023 patients screened for the study, 935 individuals fulfilled the inclusion criteria. Of these critically ill patients, 282 were at risk of ARDS (30%, 95% CI 27-33), representing 0·14 cases per ICU bed over a 1-week period. V_T was similar for patients at risk and not at risk of ARDS (median 7·6 mL/kg PBW [IQR 6·7-9·1] vs 7·9 mL/kg PBW [6·8-9·1]; p=0·346). PEEP was higher in patients at risk of ARDS compared with those not at risk (median 6·0 cm H₂O [IQR 5·0-8·0] vs 5·0 cm H₂O [5·0-7·0]; p<0·0001). The prevalence of ARDS in patients at risk of ARDS was higher than in individuals not at risk of ARDS (19/260 [7%] vs 17/556 [3%]; p=0·004). Compared with individuals not at risk of ARDS, patients at risk of ARDS had higher in-hospital mortality (86/543 [16%] vs 74/232 [32%]; p<0·0001), ICU mortality (62/533 [12%] vs 66/227 [29%]; p<0·0001), and 90-day mortality (109/653 [17%] vs 88/282 [31%]; p<0·0001). V_T did not differ between patients who did and did not develop ARDS (p=0·471 for those at risk of ARDS; p=0·323 for those not at risk).

INTERPRETATION

Around a third of patients receiving mechanical ventilation in the ICU were at risk of ARDS. Pulmonary complications occur frequently in patients at risk of ARDS and their clinical outcome is worse compared with those not at risk of ARDS. There is potential for improvement in the management of patients without ARDS. Further refinements are needed for prediction of ARDS.

FUNDING

None.

Intensive care and invasive ventilation in the elderly patient, implications of chronic lung disease and comorbidities

Aims: Elderly patients have an increasing prevalence of illness that requires consideration of critical care and invasive ventilatory support. Although critical care of even the very elderly can provide value, with increasing age the potential risks of treatment and diminishing returns with respect to quality and quantity of life result in a need for careful evaluation. Variable combinations of impaired organ function, active disease and residual pathology from past disease and injury all affect critical care, with the consequence that the elderly are a very heterogeneous population. Recognizing that critical care is a limited resource, it is important to identify patients who may be at increased risk or least likely to benefit from treatment. Patients with functional impairments, nutritional deficiencies and multiple comorbidities may be at highest risk of poor outcomes. Those with very severe disease, extreme age and requirements for prolonged ventilatory support have high in-hospital mortality. Functional impairments, comorbidities and severity of illness are usually more important considerations than chronologic age. The objective of this review is to identify how common problems of the elderly affect critical care and decisions concerning use of invasive ventilatory support.

One-year resource utilisation, costs and quality of life in patients with acute respiratory distress syndrome (ARDS): secondary analysis of a randomised controlled trial

Background

The long-term economic and quality-of-life outcomes of patients admitted to intensive care unit (ICU) with acute respiratory distress syndrome are not well understood. In this study, we investigate 1-year costs, survival and quality of life following ICU admission in patients who required mechanical ventilation for acute respiratory distress syndrome.

Methods

Economic analysis of data collected alongside a UK-based multi-centre randomised, controlled trial, aimed at comparing high-frequency oscillatory ventilation with conventional mechanical ventilation. The study included 795 critically ill patients admitted to ICU. Hospital costs were assessed using daily data. Post-hospital healthcare costs, patient out-of-pocket expenses, lost earnings of survivors and their carers and health-related quality of life were assessed using follow-up surveys.

Results

The mean cost of initial ICU stay was £26,857 (95 % CI £25,222–£28,491), and the average daily cost in ICU was £1738 (CI £1667–£1810). Following hospital discharge, the average 1-year cost among survivors was £7523 (CI £5692–£9354). The mean societal cost at 1 year was £44,077 (£41,168–£46,985), and the total societal cost divided by the number of 1-year survivors was £90,206. Survivors reported significantly lower health-related quality of life than the age- and sex-matched reference population, and this difference was more marked in younger patients.

Conclusions

Given the high costs and low health-related quality of life identified, there is significant scope for further research aimed at improving care in this in-need patient group.

Trial registration

ISRCTN10416500

Lung complications are common in intensive care treated patients with pelvis fractures: a retrospective cohort study

Background

The incidence of severe respiratory complications in patients with pelvis fractures needing intensive care have not previously been studied. Therefore, the aims of this registry study were to 1) determine the number of ICU patients with pelvis fractures who had severe respiratory complications 2) whether the surgical intervention in these patients is associated with the pulmonary condition and 3) whether there is an association between lung complications and mortality. We hypothesized that acute hypoxic failure (AHF) and acute respiratory distress syndrome (ARDS) 1) are common in ICU treated patients with pelvis fractures, 2) are not related to the reconstructive surgery, or to 3) to mortality.

Methods

All patients in the database cohort (n = 112), scheduled for surgical stabilization of pelvis ring and/or acetabulum fractures, admitted to the general ICU at Uppsala University Hospital between 2007 and 2014 for intensive care were included.

Results

The incidence of AHF/ARDS was 67 % (75/112 patients), i.e., the percentage of patients that at any period during the ICU stay fulfilled the AHF/ARDS criteria. The incidence of AHF was 44 % and incidence of ARDS was 23 %. The patients with AHF/ARDS had more lung contusions and pneumonia than the patients without AHF/ARDS. Overall, there were no significant changes in oxygenation variables associated with surgery. However, 23 patients with pre-operative normal lung status developed AHF/ARDS in relation to the surgical procedure, whereas 12 patients with AHF/ARDS normalized their lung condition. The patients who developed AHF/ARDS had a higher incidence of lung contusion (P = 0.04) and the surgical stabilization was performed earlier (5 versus 10 days) in these patients (P = 0.03).

Conclusions

We found that the incidence of respiratory failure in ICU treated patients with pelvis fractures was high, that the procedure around surgical stabilization seems to be associated with a worsening in the respiratory function in patients with lung contusion, and that mortality was low and was probably not related to the respiratory condition.

Trial registration

Study was registered at ISRCTN.org number, ISRCTN10335587.

Lung Injury Prediction Score Is Useful in Predicting Acute Respiratory Distress Syndrome and Mortality in Surgical Critical Care Patients

Background. Lung injury prediction score (LIPS) is valuable for early recognition of ventilated patients at high risk for developing acute respiratory distress syndrome (ARDS). This study analyzes the value of LIPS in predicting ARDS and mortality among ventilated surgical patients. Methods. IRB approved, prospective observational study including all ventilated patients admitted to the surgical intensive care unit at a single tertiary center over 6 months. ARDS was defined using the Berlin criteria. LIPS were calculated for all patients and analyzed. Logistic regression models evaluated the ability of LIPS to predict development of ARDS and mortality. A receiver operator characteristic (ROC) curve demonstrated the optimal LIPS value to statistically predict development of ARDS. Results. 268 ventilated patients were observed; 141 developed ARDS and 127 did not. The average LIPS for patients who developed ARDS was 8.8 ± 2.8 versus 5.4 ± 2.8 for those who did not (p < 0.001). An ROC area under the curve of 0.79 demonstrates LIPS is statistically powerful for predicting ARDS development. Furthermore, for every 1-unit increase in LIPS, the odds of developing ARDS increase by 1.50 (p < 0.001) and odds of ICU mortality increase by 1.22 (p < 0.001). Conclusion. LIPS is reliable for predicting development of ARDS and predicting mortality in critically ill surgical patients.

Acute respiratory distress syndrome and pneumothorax

Acute respiratory distress syndrome (ARDS) can occur during the treatment of several diseases and in several interventional procedures as a complication. It is a difficult situation to handle and special care should be applied to the patients. Mechanical ventilation is used for these patients and several parameters are changed constantly until compliance is achieved. However, a complication that is observed during the application of positive airway pressure is pneumothorax. In our current work we will present definition and causes of pneumothorax in the setting of intensive care unit (ICU). We will identify differences and similarities of this situation and present treatment options.

Incidence and outcome of acute lung injury and acute respiratory distress syndrome in the surgical intensive care unit

Introduction:

To determine the incidence and mortality of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) in a cohort of patients with risk factors admitted to the Surgical Intensive Care Unit (SICU).

Materials and Methods:

A prospective observational inception cohort study with no intervention was conducted over 12 months. All patients with at least one known risk factor for ALI/ARDS admitted to the SICU were included in the study. The APACHE II severity of disease classification system scoring was performed within 1 h of admission. The ventilatory parameters and chest radiographs were recorded every 24 h. The P/F ratio, PEEP and Lung Injury Score were calculated each day until the day of discharge from the Intensive Care Unit or for the first 7 days of admission, whichever was shorter.

Results:

The incidence of ARDS among those who were mechanically ventilated was 11.4%. Sepsis was the most common (34.6%) etiology. Among those with risk factors, the incidence of ARDS was 30% and that of ALI was 32.7%. The mortality in those with ARDS was 41.8%. Those who develop ARDS had higher APACHE II scores, lower pH and higher PaCO₂ at admission compared with those who developed ALI or no lung injury.

Conclusion:

The incidence and mortality of ARDS was similar to other studies. Identifying those with risk factors for ARDS or mortality will enable appropriate interventional measures.

Evolving epidemiology and definitions of the acute respiratory distress syndrome and early acute lung injury

This article reviews the evolving definitions and epidemiology of the acute respiratory distress syndrome (ARDS) and highlights current efforts to improve identification of high-risk patients, thus to target prevention and early treatment before progression to ARDS. This information will be important for general practitioners and intensivists interested in improving the care of patients at risk for ARDS, and clinical researchers interested in designing clinical trials targeting the prevention and early treatment of acute lung injury.

Geographic access to high capability severe acute respiratory failure centers in the United States

OBJECTIVE

Optimal care of adults with severe acute respiratory failure requires specific resources and expertise. We sought to measure geographic access to these centers in the United States.

DESIGN

Cross-sectional analysis of geographic access to high capability severe acute respiratory failure centers in the United States. We defined high capability centers using two criteria: (1) provision of adult extracorporeal membrane oxygenation (ECMO), based on either 2008-2013 Extracorporeal Life Support Organization reporting or provision of ECMO to 2010 Medicare beneficiaries; or (2) high annual hospital mechanical ventilation volume, based 2010 Medicare claims.

SETTING

Nonfederal acute care hospitals in the United States.

MEASUREMENTS AND MAIN RESULTS

We defined geographic access as the percentage of the state, region and national population with either direct or hospital-transferred access within one or two hours by air or ground transport. Of 4,822 acute care hospitals, 148 hospitals met our ECMO criteria and 447 hospitals met our mechanical ventilation criteria. Geographic access varied substantially across states and regions in the United States, depending on center criteria. Without interhospital transfer, an estimated 58.5% of the national adult population had geographic access to hospitals performing ECMO and 79.0% had geographic access to hospitals performing a high annual volume of mechanical ventilation. With interhospital transfer and under ideal circumstances, an estimated 96.4% of the national adult population had geographic access to hospitals performing ECMO and 98.6% had geographic access to hospitals performing a high annual volume of mechanical ventilation. However, this degree of geographic access required substantial interhospital transfer of patients, including up to two hours by air.

CONCLUSIONS

Geographic access to high capability severe acute respiratory failure centers varies widely across states and regions in the United States. Adequate referral center access in the case of disasters and pandemics will depend highly on local and regional care coordination across political boundaries.

Effects of clinically relevant acute hypercapnic and metabolic acidosis on the cardiovascular system: an experimental porcine study

INTRODUCTION

Hypercapnic acidosis (HCA) that accompanies lung-protective ventilation may be considered permissive (a tolerable side effect), or it may be therapeutic by itself. Cardiovascular effects may contribute to, or limit, the potential therapeutic impact of HCA; therefore, a complex physiological study was performed in healthy pigs to evaluate the systemic and organ-specific circulatory effects of HCA, and to compare them with those of metabolic (eucapnic) acidosis (MAC).

METHODS

In anesthetized, mechanically ventilated and instrumented pigs, HCA was induced by increasing the inspired fraction of CO2 (n = 8) and MAC (n = 8) by the infusion of HCl, to reach an arterial plasma pH of 7.1. In the control group (n = 8), the normal plasma pH was maintained throughout the experiment. Hemodynamic parameters, including regional organ hemodynamics, blood gases, and electrocardiograms, were measured in vivo. Subsequently, isometric contractions and membrane potentials were recorded in vitro in the right ventricular trabeculae.

RESULTS

HCA affected both the pulmonary (increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR)) and systemic (increase in mean arterial pressure (MAP), decrease in systemic vascular resistance (SVR)) circulations. Although the renal perfusion remained unaffected by any type of acidosis, HCA increased carotid, portal, and, hence, total liver blood flow. MAC influenced the pulmonary circulation only (increase in MPAP and PVR). Both MAC and HCA reduced the stroke volume, which was compensated for by an increase in heart rate to maintain (MAC), or even increase (HCA), the cardiac output. The right ventricular stroke work per minute was increased by both MAC and HCA; however, the left ventricular stroke work was increased by HCA only. In vitro, the trabeculae from the control pigs and pigs with acidosis showed similar contraction force and action-potential duration (APD). Perfusion with an acidic solution decreased the contraction force, whereas APD was not influenced.

CONCLUSIONS

MAC preferentially affects the pulmonary circulation, whereas HCA affects the pulmonary, systemic, and regional circulations. The cardiac contractile function was reduced, but the cardiac output was maintained (MAC), or even increased (HCA). The increased ventricular stroke work per minute revealed an increased work demand placed by acidosis on the heart.

Acute respiratory distress syndrome: nationwide changes in incidence, treatment and mortality over 23 years

INTRODUCTION

The aim of this study was to assess population-based changes in incidence, treatment, and in short- and long-term survival of patients with acute respiratory distress syndrome (ARDS) over 23 years.

MATERIALS AND METHODS

Analysis of all patients in Iceland who fulfilled the consensus criteria for ARDS in 1988-2010. Demographic variables, Acute Physiology and Chronic Health Evaluation II (APACHE II) scores and ventilation parameters were collected from hospital charts.

RESULTS

The age-standardised incidence of ARDS during the study period was 7.2 cases per 100,000 person-years and was increased by 0.2 cases per year (P < 0.001). The most common causes of ARDS were pneumonia (29%) and sepsis (29%). The use of pressure-controlled ventilation became almost dominant from 1993. The peak inspiratory pressure (PIP) has significantly decreased (-0.5 cmH(2) O/year), but the peak end-expiratory pressure (PEEP) has increased (0.1 cmH(2) O/year) during the study period. The hospital mortality decreased by 1% per year (P = 0.03) during the study period, from 50% in 1988-1992 to 33% in 2006-2010. A multivariable logistic regression model revealed that higher age and APACHE II score increased the odds of hospital mortality, while a higher calendar year of diagnosis reduced the odds of mortality. This was unchanged when dominant respiratory treatment, PIP and PEEP were added to the model. The 10-year survival of ARDS survivors was 68% compared with 90% survival of a reference population (P < 0.001).

CONCLUSION

The incidence of ARDS has almost doubled, but hospital mortality has decreased during the 23 years of observation. The 10-year survival of ARDS survivors is poor compared with the reference population.

Association between inhaled nitric oxide treatment and long-term pulmonary function in survivors of acute respiratory distress syndrome

Introduction

Assessment of treatments for acute respiratory distress syndrome (ARDS) has focused on short-term outcomes (for example, mortality); little information exists regarding long-term effects of ARDS treatment. Survivors of ARDS episodes may have long-term obstructive/restrictive pulmonary abnormalities and pulmonary gas exchange impairment. A 2004 prospective randomized placebo-controlled trial assessed the efficacy and safety of inhaled nitric oxide (iNO) in patients with non-septic ARDS; the primary endpoint was days alive and off assisted breathing. This analysis examined potential effects of iNO or placebo on pulmonary function six months post-treatment in ARDS survivors from that original study.

Methods

ARDS survivors (N = 92) from a large-scale randomized, placebo-controlled study evaluating mortality after either 5 ppm iNO or placebo for up to 28 days were assessed six months post-treatment. Pulmonary function testing across seven parameters was conducted.

Results

At 6 months post-treatment, results indicated significantly better absolute values for iNO versus placebo for mean ± SD total lung capacity (TLC, 5.54 ± 1.42 vs. 4.81 ± 1.00; P = 0.026). There were also significantly better values for mean ± SD percent predicted values for a) forced expiratory volume in 1 second (FEV₁, 80.23 ± 21.21 vs. 69.51 ± 28.97; P = 0.042), b) forced vital capacity (FVC, 83.78 ± 19.37 vs. 69.84 ± 27.40; P = 0.019), c) FEV₁/FVC (96.14 ± 13.79 vs. 87.92 ± 19.77; P = 0.033), and d) TLC (93.33 ± 18.21 vs. 76.10 ± 21.84; P < 0.001). Nonsignificant differences were found in absolute FEV1, FEV1/FVC, FVC, forced expiratory flow from 25% to 75% of FVC, functional residual capacity, and CO diffusion.

Conclusions

ARDS patients surviving after treatment with low-dose iNO had significantly better values for select pulmonary function tests at six months post-treatment than placebo-treated patients. Further trials are warranted to determine the effects of iNO on chronic lung function in ARDS survivors, a factor in long-term morbidity and quality of life in this population.

Trial Registration

A Double-blind, Randomized, Placebo-controlled, Dose-response Study of Inhaled Nitric Oxide in the Treatment of Acute Respiratory Distress Syndrome. NCT number: ISRCTN53268296

Normal-range blood lactate concentration in septic shock is prognostic and predictive

We hypothesized that lactate levels even within the normal range are prognostic and that low lactate levels predict a beneficial response to vasopressin infusion in septic shock. We conducted a retrospective analysis using the Vasopressin in Septic Shock Trial (VASST) as a derivation cohort (n = 665), then validated using another single-center septic shock cohort, St Paul's Hospital (SPH) cohort (n = 469). Lactate levels were divided into quartiles. The primary outcome variable was 28-day mortality in both cohorts. We used receiver operating characteristic (ROC) curve analysis to compare the prognostic value of lactate concentrations versus Acute Physiology and Chronic Health Evaluation II scores. We then explored whether lactate concentrations might predict beneficial response to vasopressin compared with noradrenaline in VASST. Normal lactate range is less than 2.3 mmol/L. At enrollment, patients in the second quartile (1.4 < lactate < 2.3 mmol/L) had significantly increased mortality and organ dysfunction compared with patients who had lactate ≤ 1.4 mmol/L (quartile 1) (P < 0.0001). Quartile 2 outcomes were as severe as quartile 3 (2.3 ≤ lactate < 4.4 mmol/L) outcomes. Baseline lactate values (ar ea under the ROC curve = 0.63, 0.66; VASST, SPH) were as good as Acute Physiology and Chronic Health Evaluation II scores (area under the ROC curve = 0.66, 0.73; VASST, SPH) as prognostic indicators of 28-day mortality. Lactate concentrations of 1.4 mmol/L or less predicted a beneficial response in those randomized to vasopressin compared with noradrenaline in VASST (P < 0.05). Lactate concentrations within the "normal" range can be a useful prognostic indicator in septic shock. Furthermore, patients whose lactate level is less than or equal to 1.4 mmol/L may benefit from vasopressin infusion.

Peripheral leukocytapheresis attenuates acute lung injury induced by lipopolysaccharide in vivo

The mortality of acute lung injury and acute respiratory distress syndrome (ALI/ARDS) remains high and efforts for prevention and treatments have shown little improvement over the past decades. The present study investigated the efficacy and mechanism of leukocytapheresis (LCAP) to partially eliminate peripheral neutrophils and attenuate lipopolysaccharide (LPS)-induced lung injury in dogs. A total of 24 healthy male mongrel dogs were enrolled and randomly divided into LPS, LCAP and LCAP-sham groups. All animals were injected with LPS to induce endotoxemia. The serum levels of leucocytes, neutrophil elastase, arterial blood gas, nuclear factor-kappa B (NF-κB) subunit p65 in lung tissues were measured. The histopathology and parenchyma apoptosis of lung tissues were examined. We found that 7, 3, and 7 animals in the LPS, LCAP, and sham-LCAP groups, respectively, developed ALI 36 h after LPS infusion. The levels of NF-κB p65 in lung tissue, neutrophils and elastase in blood, decreased significantly following LCAP. LCAP also alleviated apoptosis, and NF-κB p65 in lung tissues. Collectively, our results show that partial removal of leucocytes from peripheral blood decreases elastase level in serum. This, in turn, attenuates lung injuries and may potentially decrease the incidence of ALI.

Recovery and long-term outcome in acute respiratory distress syndrome

Interest in longer-term outcomes after acute respiratory distress syndrome (ARDS) and the understanding of patterns of recovery have increased enormously over the past 10 years. This article highlights important advances in outcomes after ARDS and describes pulmonary outcomes, the most recent data on functional and neuropsychological disability in patients, health care cost, family caregivers, and early models of rehabilitation and intervention.

The ALIEN study: incidence and outcome of acute respiratory distress syndrome in the era of lung protective ventilation

PURPOSE

While our understanding of the pathogenesis and management of acute respiratory distress syndrome (ARDS) has improved over the past decade, estimates of its incidence have been controversial. The goal of this study was to examine ARDS incidence and outcome under current lung protective ventilatory support practices before and after the diagnosis of ARDS.

METHODS

This was a 1-year prospective, multicenter, observational study in 13 geographical areas of Spain (serving a population of 3.55 million at least 18 years of age) between November 2008 and October 2009. Subjects comprised all consecutive patients meeting American-European Consensus Criteria for ARDS. Data on ventilatory management, gas exchange, hemodynamics, and organ dysfunction were collected.

RESULTS

A total of 255 mechanically ventilated patients fulfilled the ARDS definition, representing an incidence of 7.2/100,000 population/year. Pneumonia and sepsis were the most common causes of ARDS. At the time of meeting ARDS criteria, mean PaO(2)/FiO(2) was 114 ± 40 mmHg, mean tidal volume was 7.2 ± 1.1 ml/kg predicted body weight, mean plateau pressure was 26 ± 5 cmH(2)O, and mean positive end-expiratory pressure (PEEP) was 9.3 ± 2.4 cmH(2)O. Overall ARDS intensive care unit (ICU) and hospital mortality was 42.7% (95%CI 37.7-47.8) and 47.8% (95%CI 42.8-53.0), respectively.

CONCLUSIONS

This is the first study to prospectively estimate the ARDS incidence during the routine application of lung protective ventilation. Our findings support previous estimates in Europe and are an order of magnitude lower than those reported in the USA and Australia. Despite use of lung protective ventilation, overall ICU and hospital mortality of ARDS patients is still higher than 40%.

Overexpression of pulmonary extracellular superoxide dismutase attenuates endotoxin-induced acute lung injury

PURPOSE

Superoxide is produced by activated neutrophils during the inflammatory response to stimuli such as endotoxin, can directly or indirectly injure host cells, and has been implicated in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). We wished to determine the potential for pulmonary overexpression of the extracellular isoform of superoxide dismutase (EC-SOD) to reduce the severity of endotoxin-induced lung injury.

METHODS

Animals were randomly allocated to undergo intratracheal instillation of (1) surfactant alone (vehicle); (2) adeno-associated virus (AAV) vectors containing a null transgene (AAV-null); and (3) adeno-associated virus vectors containing the EC-SOD transgene (AAV-EC-SOD) and endotoxin was subsequently administered intratracheally. Two additional groups were randomized to receive (1) vehicle or (2) AAV-EC-SOD, and to undergo sham (vehicle) injury. The severity of the lung injury was assessed in all animals 24 h later.

RESULTS

Endotoxin produced a severe lung injury compared to sham injury. The AAV vector encoding EC-SOD increased lung EC-SOD concentrations, and enhanced the antioxidant capacity of the lung. EC-SOD overexpression decreased the severity of endotoxin-induced ALI, reducing the decrement in systemic oxygenation and lung compliance, decreasing lung permeability and decreasing histologic injury. EC-SOD attenuated pulmonary inflammation, decreased bronchoalveolar lavage neutrophil counts, and reduced interleukin-6 and CINC-1 concentrations. The AAV vector itself did not contribute to inflammation or to lung injury.

CONCLUSIONS

Pulmonary overexpression of EC-SOD protects the lung against endotoxin-induced ALI.

Lower incidence of acute respiratory distress syndrome in community-acquired pneumonia patients aged 85 years or older

Clinical variables and laboratory data were compared to elucidate the risk factors associated with the development of ARDS among elderly patients with community-acquired pneumonia (CAP). The predictors for ARDS appeared to differ from the determinants of severity of CAP. ARDS developed less frequently among patients aged>or=85 years.

BACKGROUND AND OBJECTIVE

The incidence of and risk factors for ARDS among elderly patients with community-acquired pneumonia (CAP) have not been well characterized.

METHODS

The clinical details of 221 consecutive patients aged>or=65 years, who were admitted with CAP during the period April 2006 to June 2008, were investigated by review of patient charts. Clinical variables and laboratory data at admission for CAP were compared between patients with and without ARDS.

RESULTS

Eighteen patients (8.1%) developed ARDS 1-5 days after admission. The mortality rate was 44% in patients with ARDS and 10.3% in those without ARDS (P<0.001). The incidence of ARDS was 8.5-20% among patients aged<85 years and 1.1% in patients aged>or=85 years (P<0.001), while overall mortality rates were not significantly different among the age groups. Predictors for the development of ARDS included higher serum levels of CRP and glucose, lower PaO2/fraction of inspired O2 (FiO2), PaCO2 and HCO3-, and the presence of systemic inflammatory response syndrome at admission. ARDS developed less frequently among patients with pneumonia associated with oropharyngeal aspiration (AP). Multivariate analysis indicated that lower age, serum glucose, pre-existence of systemic inflammatory response syndrome and non-oropharyngeal AP were significant risk factors for ARDS. The Pneumonia Severity Index and confusion, urea, respiratory rate, blood pressure, age>or=65 score were not correlated with the incidence of ARDS.

CONCLUSIONS

Predictors for ARDS appeared to differ from the determinants of severity of CAP in the elderly. ARDS developed less frequently in patients aged>or=85 years and in those with oropharyngeal AP. It is important to identify subjects at high risk for ARDS upon admission and to observe them closely.

Diagnosing acute lung injury in the critically ill: a national survey among critical care physicians

BACKGROUND

Incidence reports on acute lung injury (ALI) vary widely. An insight into the diagnostic preferences of critical care physicians when diagnosing ALI may improve identification of the ALI patient population.

METHODS

Critical care physicians in the Netherlands were surveyed using vignettes involving hypothetical patients and a questionnaire. The vignettes varied in seven diagnostic determinants based on the North American European Consensus Conference and the lung injury score. Preferences were analyzed using a mixed-effects logistic regression model and presented as an odds ratio (OR) with a 95% confidence interval.

RESULTS

From 243 surveys sent to 30 hospitals, 101 were returned (42%). ORs were as follows: chest X-ray consistent with ALI: OR 1.7 (1.3-2.3), high positive end-expiratory pressure (PEEP) (15 cmH(2)O): OR 5.0 (3.9-6.6), low pulmonary artery occlusion pressures (PAOP) (<18 mmHg): OR 4.7 (3.6-6.1), low compliance (30 ml/cmH(2)O): OR 0.7 (0.5-0.9), low PaO(2)/FiO(2) (<250 mmHg): OR 9.2 (6.9-12.3), absence of heart failure: OR 1.2 (0.9-1.5), presence of a risk factor for ALI (sepsis): OR 1.0 (0.8-1.3). The questionnaire revealed that critical care physicians with an anesthesiology background differed from physicians with an internal medicine background with regard to hemodynamic variables when considering an ALI diagnosis (P<0.05).

CONCLUSIONS

Dutch critical care physicians consider the PEEP level, but not the presence of a risk factor for ALI, as an important factor to diagnose ALI. Background specialty of critical care physicians influences diagnostic preferences and may account for variance in the reported incidence of ALI.

Hypercapnic acidosis attenuates severe acute bacterial pneumonia-induced lung injury by a neutrophil-independent mechanism

OBJECTIVE

Deliberate induction of hypercapnic acidosis protects against lung injury after nonseptic lung injury. In contrast, concerns exist regarding the effects of hypercapnic acidosis in the setting of severe pulmonary sepsis. The potential for the effects of hypercapnic acidosis to be neutrophil-mediated remains to be determined. We investigated whether hypercapnic acidosis--induced by adding CO2 to inspired gas--would protect against severe acute lung injury induced by pulmonary Escherichia coli instillation and the role of neutrophils in mediating this effect.

DESIGN

Prospective randomized animal study.

SETTING

University Research Laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

In series 1, after induction of anesthesia and tracheostomy placement, animals were randomized to normocapnia (FICO2 0.00, n = 12) or hypercapnic acidosis (FICO2 0.05, n = 12). E. coli (0.5-3.0 x 10(15) colony-forming units) was instilled intratracheally and the animals were ventilated for 6 hrs to allow a severe acute lung injury to evolve. In series 2, animals were randomized to neutrophil depletion or nondepletion before bacterial instillation, in a three-group design: normocapnia alone (Normo + polymorphonuclear neutrophils [PMN], n = 9), normocapnia with neutrophil depletion (Normo - PMN, n = 9), or hypercapnic acidosis with neutrophil depletion (hypercapnic acidosis - PMN, n = 9). After intratracheal E. coli administration these animals were also ventilated for 6 hrs.

RESULTS

Hypercapnic acidosis protected against evolving pneumonia-induced acute lung injury, attenuating the increase in airway pressure, and the decrement in lung compliance and arterial PO2. However, hypercapnic acidosis did not reduce histologic injury. Hypercapnic acidosis also protected against evolving pneumonia-induced acute lung injury in the presence of neutrophil depletion, reducing both physiologic and histologic indices of lung injury.

CONCLUSIONS

Hypercapnic acidosis reduces indices of intratracheal E. coli induced lung injury by a mechanism that seems to be neutrophil-independent.

Acute respiratory distress syndrome 40 years later: time to revisit its definition

OBJECTIVE

Acute respiratory distress syndrome is a common disorder associated with significant mortality and morbidity. The aim of this article is to critically evaluate the definition of acute respiratory distress syndrome and examine the impact the definition has on clinical practice and research.

DATA SOURCES

Articles from a MEDLINE search (1950 to August 2007) using the Medical Subject Heading respiratory distress syndrome, adult, diagnosis, limited to the English language and human subjects, their relevant bibliographies, and personal collections, were reviewed.

DATA SYNTHESIS

The definition of acute respiratory distress syndrome is important to researchers, clinicians, and administrators alike. It has evolved significantly over the last 40 years, culminating in the American-European Consensus Conference definition, which was published in 1994. Although the American-European Consensus Conference definition is widely used, it has some important limitations that may impact on the conduct of clinical research, on resource allocation, and ultimately on the bedside management of such patients. These limitations stem partially from the fact that as defined, acute respiratory distress syndrome is a heterogeneous entity and also involve the reliability and validity of the criteria used in the definition. This article critically evaluates the American-European Consensus Conference definition and its limitations. Importantly, it highlights how these limitations may contribute to clinical trials that have failed to detect a potential true treatment effect. Finally, recommendations are made that could be considered in future definition modifications with an emphasis on the significance of accurately identifying the target population in future trials and subsequently in clinical care.

CONCLUSION

How acute respiratory distress syndrome is defined has a significant impact on the results of randomized, controlled trials and epidemiologic studies. Changes to the current American-European Consensus Conference definition are likely to have an important role in advancing the understanding and management of acute respiratory distress syndrome.

The impact of development of acute lung injury on hospital mortality in critically ill trauma patients

OBJECTIVE

The additional impact of development of acute lung injury on mortality in severely-injured trauma patients beyond baseline severity of illness has been questioned. We assessed the contribution of acute lung injury to in-hospital mortality in critically ill trauma patients.

DESIGN

Prospective cohort study. The contribution of acute lung injury to in-hospital mortality was evaluated in two ways. First, multivariable logistic regression models were used to test the independent association of acute lung injury with in-hospital mortality while adjusting for baseline confounding variables. Second, causal pathway models were used to estimate the amount of the overall association of baseline severity of illness with in-hospital mortality that is attributable to the interval development of acute lung injury.

SETTING

Academic level 1 trauma center.

PATIENTS

Two hundred eighty-three critically ill trauma patients without isolated head injury and with an Injury Severity Score > or = 16 were evaluated for development of acute lung injury in the first 5 days after trauma.

MEASUREMENTS AND MAIN RESULTS

Of the 283 patients, 38 (13.4%) died. The unadjusted mortality rate was nearly three-fold greater in the acute lung injury group (23.9% vs. 8.4%; odds ratio = 3.36; 95% confidence interval 1.67-6.77; p = 0.001). Acute lung injury remained an independent risk factor for death after adjustment for age, baseline Acute Physiologic and Chronic Health Evaluation III score, Injury Severity Score, and blunt mechanism of injury (odds ratio = 2.87; 95% confidence interval 1.29-6.37; p = 0.010). Forty percent of the total association of the baseline Acute Physiologic and Chronic Health Evaluation III score with mortality occurred via an indirect association through acute lung injury, and the remaining 60% via a direct effect.

CONCLUSIONS

Development of acute lung injury in critically ill trauma patients without isolated head injury contributes independently to in-hospital mortality beyond baseline severity of illness measures. In addition, a significant portion of the association between baseline illness severity and risk of death in these patients might be explained by the interval development of acute lung injury.

The analysis of risk factors of impacting mortality rate in severe multiple trauma patients with posttraumatic acute respiratory distress syndrome

OBJECTIVE

We hypothesize that not all of the traditional risk factors of impacting mortality rate in commonly traumatic populations with posttraumatic acute respiratory distress syndrome (ARDS) are independently associated with those patient populations identified with severe multiple trauma. Rather, we postulate that there may exist significantly different impacting degrees of specific risk factors in stratified patients (surviving beyond 24 and 96 hours)--more severe multiple trauma with higher injury score and long-term mechanical ventilation as well.

METHODS

This is a retrospective cohort study regarding trauma as a single cause for emergency intensive care unit admission. Twenty-two items of potential risk factors of impacting mortality rate were calculated by univariate and multivariate logistic analyses to find distinctive items in these severe multiple trauma patients.

RESULTS

The unadjusted odds ratio and 95% confidence intervals of mortality rate were found to be associated with 6 (out of 22) risk factors, namely, (1) Acute Physiology and Chronic Health Evaluation II score, (2) duration of trauma factor, (3) aspiration of gastric contents, (4) sepsis, (5) pulmonary contusion, and (6) duration of mechanical ventilation. Significant results also appeared in stratified patients.

CONCLUSIONS

Impact of pulmonary contusion and Acute Physiology and Chronic Health Evaluation II score contributing to prediction of mortality may exist in the early phase after trauma. Sepsis is still a vital risk factor referring to systemic inflammatory response syndrome, infection, secondary multiple organ dysfunction, etc. Discharging trauma factors as early as possible becomes the critical therapeutic measure. Aspiration of gastric contents in emergency intensive care unit admission could lead to incremental mortality rate due to aspiration pneumonia. Long-standing mechanical ventilation should be constrained because it is likely to cause severe refractory complications.

Mortality rates for patients with acute lung injury/ARDS have decreased over time

BACKGROUND

Over the last decade, several studies have suggested that survival rates for patients with acute lung injury (ALI) or ARDS may have improved. We performed a systematic analysis of the ALI/ARDS literature to document possible trends in mortality between 1994 and 2006.

METHODS

We used the Medline database to select studies with the key words "acute lung injury," "ARDS," "acute respiratory failure," and "mechanical ventilation." All studies that reported mortality rates for patients with ALI/ARDS defined according to the criteria of the American European Consensus Conference were selected. We excluded studies with < 30 patients and studies limited to specific subgroups of ARDS patients such as sepsis, trauma, burns, or transfusion-related ARDS.

RESULTS

Seventy-two studies were included in the analysis. There was a wide variation in mortality rates among the studies (15 to 72%). The overall pooled mortality rate for all studies was 43% (95% confidence interval, 40 to 46%). Metaregression analysis suggested a significant decrease in overall mortality rates of approximately 1.1%/yr over the period analyzed (1994 to 2006). The mortality reduction was also observed for hospital but not for ICU or 28-day mortality rates.

CONCLUSIONS

In this literature review, the data are consistent with a reduction in mortality rates in general populations of patients with ALI/ARDS over the last 10 years.

Modelling survival in acute severe illness: Cox versus accelerated failure time models

BACKGROUND

The Cox model has been the mainstay of survival analysis in the critically ill and time-dependent covariates have infrequently been incorporated into survival analysis.

OBJECTIVES

To model 28-day survival of patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), and compare the utility of Cox and accelerated failure time (AFT) models.

METHODS

Prospective cohort study of 168 adult patients enrolled at diagnosis of ALI in 21 adult ICUs in three Australian States with measurement of survival time, censored at 28 days. Model performance was assessed as goodness-of-fit [GOF, cross-products of quantiles of risk and time intervals (P > or = 0.1), Cox model] and explained variation ('R2', Cox and ATF).

RESULTS

Over a 2-month study period (October-November 1999), 168 patients with ALI were identified, with a mean (SD) age of 61.5 (18) years and 30% female. Peak mortality hazard occurred at days 7-8 after onset of ALI/ARDS. In the Cox model, increasing age and female gender, plus interaction, were associated with an increased mortality hazard. Time-varying effects were established for patient severity-of-illness score (decreasing hazard over time) and multiple-organ-dysfunction score (increasing hazard over time). The Cox model was well specified (GOF, P > 0.34) and R2 = 0.546, 95% CI: 0.390, 0.781. Both log-normal (R2 = 0.451, 95% CI: 0.321, 0.695) and log-logistic (R2 0.470, 95% CI: 0.346, 0.714) AFT models identified the same predictors as the Cox model, but did not demonstrate convincingly superior overall fit.

CONCLUSIONS

Time dependence of predictors of survival in ALI/ARDS exists and must be appropriately modelled. The Cox model with time-varying covariates remains a flexible model in survival analysis of patients with acute severe illness.

The presence of the adult respiratory distress syndrome does not worsen mortality or discharge disability in blunt trauma patients with severe traumatic brain injury

PURPOSE

To evaluate the prevalence of the acute respiratory distress syndrome (ARDS) among blunt trauma patients with severe traumatic brain injury (TBI) and to determine if ARDS is associated with higher mortality, morbidity and worse discharge outcome.

METHODS

Blunt trauma patients with TBI (head abbreviated injury score (AIS)> or =4) who developed predefined ARDS criteria between January 2000 and December 2004 were prospectively collected as part of an ongoing ARDS database. Each patient in the TBI+ARDS group was matched with two control TBI patients based on age, injury severity score (ISS) and head AIS. Outcomes including complications, mortality and discharge disability were compared between the two groups.

RESULTS

Among 362 TBI patients, 28 (7.7%) developed ARDS. There were no differences between the two groups with respect to age, sex, ISS, Glasgow coma score (GCS), head, abdomen and extremity AIS. The TBI+ARDS group had significantly more patients with chest AIS> or =3 (57.1% versus 32.1%, p=0.03). There was no difference with respect to overall mortality between the TBI+ARDS group (50.0%) and the TBI group (51.8%) (OR 0.79: 95% CI 0.31-2.03, p=0.63). There was no significant difference with respect to discharge functional capacity between the two groups. There were significantly more overall complications in the TBI+ARDS group (42.9%) compared to the TBI group (16.1%) (OR 3.66: 95% CI 1.19-11.24, p=0.02). The TBI+ARDS group had an overall mean intensive care unit (ICU) length of stay of 15.6 days, versus 8.4 days in the TBI group (p<0.01). The TBI+ARDS group had significantly higher hospital charges than the TBI group ($210,097 versus $115,342, p<0.01).

CONCLUSION

The presence of ARDS was not associated with higher mortality or worse discharge disability. It was, however, associated with higher hospital morbidity, longer ICU and hospital length of stay.

Epidemiology of acute lung injury and acute respiratory distress syndrome in The Netherlands: A survey

BACKGROUND

The characteristics, incidence and risk factors for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) may depend on definitions and geography.

METHODS

A prospective, 3-day point-prevalence study was performed by a survey of all intensive care units (ICU) in the Netherlands (n=96). Thirty-six ICU's responded (37%), reporting on 266 patients, of whom 151 were mechanically ventilated. The questionnaire included criteria and potential risk factors for ALI/ARDS, according to the North American-European Consensus Conference (NAECC) or the lung injury score (LIS>or=2.5).

RESULTS

Agreement between definitions was fair (kappa 0.31-0.42, P=0.001). ALI/ARDS was characterized, regardless of definition, by radiographic densities, low oxygenation ratios, high inspiratory O(2) and airway pressure requirements. Depending on definitions, ALI and ARDS accounted for about 12-33% and 7-9% of ICU admissions per year, respectively, constituting 21-58% (ALI) and 13-16% (ARDS) of all mechanically ventilated patients. The annual incidences of ALI and ARDS are 29.3 (95%CI 18.4-40.1) and 24.0 (95%CI 14.2-33.8) by NAECC, respectively, and are, respectively, 83.6 (95%CI 65.3-101.9) and 20.9 (95%CI 11.7-30.1) by LIS per 100,000. Risk factors for ALI/ARDS were aspiration, pneumonia, sepsis and chronic alcohol abuse (the latter only by NAECC).

CONCLUSION

The effect of definitions of ALI/ARDS on mechanical ventilation in the Netherlands is small. Nevertheless, the incidence of ALI/ARDS may be higher than in other European countries but lower than in the USA, and the incidence of ALI by LIS may overestimate compared to that by NAECC. Aspiration, pneumonia, sepsis and chronic alcohol abuse are major risk factors, largely independent of definitions.

Acute lung injury and the acute respiratory distress syndrome: a clinical review

Acute respiratory distress syndrome and acute lung injury are well defined and readily recognised clinical disorders caused by many clinical insults to the lung or because of predispositions to lung injury. That this process is common in intensive care is well established. The mainstay of treatment for this disorder is provision of excellent supportive care since these patients are critically ill and frequently have coexisting conditions including sepsis and multiple organ failure. Refinements in ventilator and fluid management supported by data from prospective randomised trials have increased the methods available to effectively manage this disorder.

Why do patients who have acute lung injury/acute respiratory distress syndrome die from multiple organ dysfunction syndrome? Implications for management

Acute respiratory distress syndrome (ARDS) affects some 10% to 15% of ICU patients and is associated with mortality rates of 40% to 50%. Although ARDS is the most severe form of acute respiratory failure, refractory hypoxia is an uncommon cause of death in these patients. The majority of patients who have ARDS die from multiple-organ dysfunction syndrome (MODS), and ARDS should, therefore, be seen as a systemic disease. Improved understanding of the systemic factors involved in the development and evolution of ARDS and MODS should facilitate the development of new therapeutic agents that will improve outcomes in these patients.

Clinical epidemiology of acute lung injury and acute respiratory distress syndrome: incidence, diagnosis, and outcomes

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are clinical syndromes characterized by the sudden onset of severe hypoxemia and diffuse bilateral pulmonary infiltrates in the absence of left atrial hypertension. Although advances have been made in the understanding of the etiology, pathophysiology, and epidemiology of both entities, many questions remain regarding their incidence, diagnosis, and outcomes. This article reviews the currently used definition of ARDS and ALI, different studies that have advanced the understanding of the epidemiology and outcomes of these entities, and several diagnostic issues that are important for both clinicians and researchers.