Increased survival of ARDS patients with severe hypoxemia (ECMO criteria)

Extracorporeal carbon dioxide removal in acute hypoxaemic respiratory failure: a systematic review, Bayesian meta-analysis and trial sequential analysis

Purpose:

To assess the safety and efficacy of extracorporeal carbon dioxide removal (ECCO2R)versusstandard care in patients with acute hypoxaemic respiratory failure (AHRF).

Methods:

MEDLINE, Embase and clinical trial registries were searched from 1994 to 31 December 2021. We included randomised controlled trials (RCTs) and observational studies. Pairs of reviewers independently extracted data and assessed the risk of bias. The primary outcome was mortality. Secondary outcomes included ventilator-free days, length of stay, safety and adverse events and physiological changes. As a primary analysis, we performed a meta-analysis of mortality until day 30 using a Bayesian random effects model. We then performed a trial sequential analysis of RCTs.

Results:

21 studies met inclusion criteria: three RCTs, enrolling 531 patients, and 18 observational studies. In a pooled analysis of RCTs, the posterior probability of increased mortality with the use of ECCO2R was 73% (relative risk 1.19, 95% credible interval 0.70–2.29). There was substantial heterogeneity in the reporting of safety and adverse events. However, the incidence of extra and intracranial haemorrhage was higher (relative risk 3.00, 95% credible interval 0.41–20.51) among those randomised to ECCO2R. Current trials have accumulated 80.8% of the diversity-adjusted required information size and the lack of effect reaches futility for a 10% absolute risk reduction in mortality.

Conclusions:

The use of ECCO2R in patients with AHRF is not associated with improvements in clinical outcomes. Furthermore, it is likely that further trials of ECCO2R aiming to achieve an absolute risk reduction in mortality of ≥10% are futile.

Platelet transfusion is associated with 90-day and 1-year mortality for adult patients requiring veno-arterial extracorporeal membrane oxygenation

BACKGROUND

Studies examining one-year mortality respecting component blood transfusion are sparse. We hypothesize that component blood product transfusions are negatively associated with 90-day and 1-year survival for all patients requiring veno-arterial (VA) or veno-venous (VV) ECMO.

STUDY DESIGN AND METHODS

This was an IRB-approved retrospective cohort analysis of 676 consecutive patients requiring ECMO at the University of Pittsburgh between 2005 and 2016. Patients were analysed both as an entire cohort and as two subsets with respect to ECMO modality (VA vs. VV). Additional data collected and analysed included patient characteristics, laboratory values and blood product transfusion.

RESULTS

Multivariable analysis revealed that platelet transfusion was associated with 90-day mortality (OR: 1·05, P = 0·037) and one-year mortality for the entire cohort (OR = 1·05, P = 0·046,). Platelet transfusion volume was also associated with mortality in the VA-ECMO subset of patients at both 90 days (OR = 1·08, P = 0·03) and one year (OR: 1·11, P = 0·014). Age, peak International Normalized Raton ECMO, nadir haemoglobin (on ECMO) and final haemoglobin (after ECMO) were significantly associated with mortality for patients requiring VA-ECMO. For VV-ECMO patients, age, INR and peak creatinine on ECMO were associated with mortality. No individual component blood product was associated with one-year mortality for patients requiring VV-ECMO.

CONCLUSION

Platelet transfusion was associated with increased 90-day and 1-year mortality for patients requiring VA-ECMO.

The use of double lumen cannula for veno-venous ECMO in trauma patients with ARDS

Background

The use of a double lumen cannula for veno-venous extracorporeal membrane oxygenation (v.v. ECMO) offers several advantages such as cannulation with only one cannula, patient comfort and the earlier mobilization and physiotherapy. The cannulation should be performed under visual wire and cannula placement into the right atrium, which is associated with risks of malposition and right ventricular perforation. The aim of this patient series is to describe the use of double lumen cannula in trauma patients with posttraumatic ARDS.

Material and methods

Criteria for the v.v ECMO treatment were defined as hypoxaemia (pO2/FiO2 < 200 mmHg, FiO2 0.8-1,0); tidal volume >4-6 ml/kg ideal body weight; mean inspiratory pressure (Pinsp) >32-34 mmHg; respiratory acidosis pH <7.25; and arterial saturation (SaO2) <90%. The analysis included the Injury Severity Score (ISS), the types of injury, time of treatment, complications and outcomes.

Results

A total of 24 patients with major trauma were treated for posttraumatic ARDS with v.v. ECMO. The double lumen cannula (Avalon®, Fa. Maquet, Rastatt, Germany) was used in six male patients. The mean ISS was 31 (20–48). The ECMO therapy was started in an average on the third day after trauma. The mean ECMO run time was 7 days ± 5 (6–18), and the hospital stay was in mean of 60 days ± 34 (21–105).

Conclusion

The use of double lumen cannula for v.v ECMO therapy in trauma patients is a feasible treatment option. No higher risk of bleeding could be found in this case series. A PTT-controlled heparinization is recommended using double lumen cannula. Therefore the use of this cannula type in trauma patients with high risk of bleeding is to discuss controversially.

Use of extracorporeal membrane oxygenation in combination with high-frequency oscillatory ventilation in post-traumatic ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening complications in trauma patients. Despite the implantation of a veno-venous extracorporeal membrane oxygenation (vv ECMO), sufficient oxygenation (arterial SaO(2)  > 90%) is not always achieved. The additive use of high-frequency oscillation ventilation (HFOV) and ECMO in the critical phase after trauma could prevent the occurrence of life-threatening hypoxaemia and multi-organ failure. We report on a 26-year-old female (Injury Severity Score 29) who had multiple injuries as follows: an unstable pelvic fracture, a blunt abdominal trauma, a blunt trauma of the left thigh, and a thoracic injury. Three days after admission, the patient developed fulminant ARDS (Murray lung injury score of 11 and Horovitz-Index <80 mmHg), and vv ECMO therapy was initiated. The Horovitz-Index was <80 mm Hg, and the lung compliance was minimal. With HFOV, almost complete recruitment of the lung was achieved, and the fraction of inspired oxygen (FiO(2) ) was significantly reduced. The pelvic fracture was treated non-operatively. The HFOV was terminated after 3 days, and the ECMO was stopped after 19 days.

Extracorporeal life support for pancreatitis-induced acute respiratory distress syndrome

OBJECTIVE

Adult respiratory distress syndrome (ARDS) secondary to acute pancreatitis is associated with a poor prognosis. We hypothesized that extracorporeal life support (ECLS) may be an effective treatment option for the most severe cases of pancreatitis-induced ARDS.

METHODS

We reviewed 8 cases of pancreatitis-induced ARDS that were treated with ECLS at our institution. We collected data on demographics, comorbidities, hemodynamic parameters, and ventilatory support used before ECLS. Our outcome measures for this study included survival to discharge, length of ECLS run, days undergoing mechanical ventilation, days in an intensive care unit, total length of hospital stay, adjunct therapies and procedures, and complications.

RESULTS

Overall, 5 of the 8 patients (63%) survived to discharge. Seven of the 8 patients underwent venovenous ECLS, and 1 underwent venoarterial ECLS. The overall mean length of ECLS was 9.7 ± 10.7 days. However, the mean ECLS run length in survivors was 4.3 ± 1.8 days and the longest ECLS run in a survivor was 7.25 days. Two of the 3 patients who died had very long run lengths (28.8 and 24.7 days, respectively), whereas 1 patient had a short run (2.4 days). Five of the 8 patients (63%), including all of the 3 who died, experienced a bleeding complication of some kind. Two patients required continuous venovenous hemofiltration, 1 of whom died and 1 of whom survived. Six patients underwent tracheostomy on ECLS, 1 patient already had undergone tracheostomy, and 1 patient did not undergo tracheostomy.

CONCLUSIONS

ECLS is useful in treating severe pancreatitis-induced ARDS. Pancreatic debridement can be performed during ECLS, using a comprehensive protocol to minimize bleeding complications.

The advent of ECMO and pumpless extracorporeal lung assist in ARDS

Despite advances in critical care facilities and ventilation therapies acute respiratory distress syndrome (ARDS) is associated with high mortality rates. The condition can stem from a multitude of causes including pneumonia, septicemia and trauma ultimately resulting in ARDS. ARDS is characterized by respiratory insufficiency with severe hypoxemia or hypercapnia. The treatment strategy depends on the knowledge of the underlying disease. But lung-protective ventilation with adjusted positive end-expiratory pressure remains the most effective therapeutic tool despite advances in prone positioning, inhalation of nitric oxide and the use of steroids. Newer modalities including extracorporeal membrane oxygenation (ECMO) and pumpless extracorporeal lung assist (PECLA) are being increasingly introduced in critical care settings as rescue therapies in patients who fail to respond to conservative measures. We describe here the introduction and advances of both ECMO and PECLA in the management of ARDS.

Use of extracorporeal life support to support patients with acute respiratory distress syndrome due to H1N1/2009 influenza and other respiratory infections

A large proportion of critically ill H1N1/2009 patients with respiratory failure subsequently developed ARDS and, to date, about 400 patients receiving extracorporeal life support (ECLS) have been accounted for globally, with a reported survival rate from 63% to 79%. The survival rates of patients with ARDS due to non-H1N1/2009 infections are similar. There is no definite evidence to suggest that patient outcomes are changed by ECLS, but its use is associated with serious short-term complications. ECLS relies on an extracorporeal circuit, with extracorporeal membrane oxygenation (ECMO) and pumpless interventional lung assist (ILA) being the two major types employed in ARDS. Both have the potential to correct respiratory failure and related haemodynamic instability. There are only a very limited number of clinical trials to test either and, although ECLS has been used in treating H1N1/2009 patients with ARDS with some success, it should only be offered in the context of clinical trials and in experienced centres.

Optimal time for initiating extracorporeal membrane oxygenation

The technical evolution of extracorporeal membrane oxygenation (ECMO) coincides with the vast improvement in intensive care medicine of the past 4 decades. Extracorporeal circulatory technology substitutes for acutely failed cardiac or pulmonary function until these organs regain sustainable function through goal-oriented intensive care practice. The technology has been validated to improve survival in select patients who would otherwise have 100% mortality. This is by far the most complex life-sustaining technology employed and thus can contribute significant risks such that the decision to institute ECMO requires prompt risk and benefit analysis. Delaying the institution of ECMO may cause irreversible pulmonary and cardiac injuries in addition to other organs. Therefore, the optimal time of initiating ECMO support is crucial to the survival of a critically ill patient.

Brain atrophy and cognitive impairment in survivors of acute respiratory distress syndrome

PRIMARY OBJECTIVES

Acute Respiratory Distress Syndrome (ARDS) is characterized by severe acute lung injury, hypoxemia and is associated with neurological and cognitive impairments. This study assessed quantitative brain and ventricular volumes in survivors of ARDS with brain computed tomography (CT) scans compared to normal controls. It also compared the medical and cognitive outcome data of patients with ARDS with and without CT scans.

RESEARCH DESIGN

Observational cohort study.

METHODS

Sixty-six consecutive acute respiratory distress patients, of which 15 patients with ARDS underwent brain CT and 51 patients had no brain imaging. Brain CT scans from 15 survivors of ARDS were compared to age- and sex-matched normal controls. Clinical radiological findings and ventricular volumes, brain volume and generalized brain atrophy.

RESULTS

The patients with ARDS and brain imaging had cognitive impairments, significant brain atrophy, ventricular enlargement and 53% had atrophy or lesions by radiological report.

CONCLUSIONS

Clinicians need to be aware that ARDS can cause significant long-term brain-related morbidity manifest by brain atrophy, lesions and neurocognitive impairments.

Blood product transfusions and clinical outcomes in pediatric patients with acute lung injury

OBJECTIVE

There are data suggesting that blood product transfusions increase the risk of developing acute lung injury (ALI) in adults, and may be associated with increased mortality in adults with ALI. A possible association between transfusions and adverse outcomes of pediatric patients with ALI has not been studied previously. We tested the hypothesis that blood product transfusions to pediatric patients with ALI within the first 72 hours of the diagnosis would be associated with increased mortality and prolonged mechanical ventilation.

DESIGN

An epidemiologic database of pediatric ALI prospectively gathered from July 1996 to May 2000 was analyzed.

SETTING

Children were enrolled from both a tertiary referral hospital and a major community children's hospital.

PATIENTS

Three hundred fifteen patients who met the 1994 American European Consensus Committee definition of ALI between the ages of 36 weeks corrected gestational age and 18 years.

MAIN OUTCOME MEASURE

Mortality in the pediatric intensive care unit.

RESULTS

Multivariate analyses indicated that the transfusion of fresh-frozen plasma (FFP) was associated with increased mortality, independent of the severity of hypoxemia (Pao2/Fio2), presence of multiple organ system failure or disseminated intravascular coagulation (odds ratio = 1.08, 95% confidence interval = 1.00-1.17, p = 0.04). FFP transfusion was analyzed as a continuous variable, so that for each milliliter of FFP transfused per kilogram patient body weight per day, the odds of death increased by 1.08. There was a trend toward an association of the transfusion of FFP with a fewer number of days of unassisted ventilation (regression coefficient = -0.21, 95% confidence interval = -0.42-0.01, p = 0.06).

CONCLUSIONS

The transfusion of FFP is associated with an increased risk of mortality in children with ALI. The association between FFP and mortality in children with ALI should be investigated further.

Patients with respiratory failure increase ambulation after transfer to an intensive care unit where early activity is a priority

OBJECTIVE

Ambulation of patients with acute respiratory failure may be unnecessarily limited in the acute intensive care setting. We hypothesized that ambulation of patients with acute respiratory failure would increase with transfer to an intensive care unit where activity is a key component of patient care.

DESIGN

Pre-post cohort study of respiratory failure patients.

SETTING

Adult intensive care units at LDS Hospital.

PATIENTS

Respiratory failure patients requiring >4 days of mechanical ventilation who were transferred from other LDS Hospital intensive care units to the respiratory intensive care unit.

INTERVENTIONS

We prospectively applied an early activity protocol to all consecutive respiratory failure patients transferred to the respiratory intensive care unit.

MEASUREMENTS AND MAIN RESULTS

We studied 104 respiratory failure patients who required mechanical ventilation for >4 days. Transferring a patient to the respiratory intensive care unit substantially increased the probability of ambulation (p < .0001). After 2 days in the respiratory intensive care unit, the number of patients ambulating had increased three-fold compared with pretransfer rates. Female gender (p = .019), the absence of sedatives (p = .009), and lower Acute Physiology and Chronic Health Evaluation II scores (p = .017) also predicted an increased probability of ambulation. Improvements in ambulation with transfer to the respiratory intensive care unit remained significant after adjustment for Acute Physiology and Chronic Health Evaluation II scores and other covariates.

CONCLUSIONS

Transfer of acute respiratory failure patients to the respiratory intensive care unit substantially improved ambulation, independent of the underlying pathophysiology. The intensive care environment may contribute unnecessary immobilization throughout the course of acute respiratory failure. Sedatives, even given intermittently, substantially reduce the likelihood of ambulation. Controlled studies are needed to determine whether intensive care unit immobilization contributes to long-term neuromuscular dysfunction or whether early intensive care unit activity improves outcomes.

Application of ECMO in multitrauma patients with ARDS as rescue therapy

BACKGROUND

Despite recent advances in critical care management, the mortality of acute respiratory distress syndrome (ARDS) remains high. The final rescue therapy for patients with severe hypoxia refractory to conventional therapy modalities is the extracorporeal gas exchange.

METHODS

We report the management of three polytraumatized patients with life-threatening injuries, severe blunt thoracic trauma, and consecutive ARDS treating by extracorporeal membrane oxygenation (ECMO). Two patients suffered a car accident with severe lung contusion and parenychmal bleeding. Bronchial rupture and mediastinal emphysema was found in one of them. Another patient developed ARDS after attempted suicide with multiple fractures together with blunt abdominal and thoracic trauma.

RESULTS

All patients were placed on ECMO and could be rapidly stabilized. They were weaned from ECMO after a mean of 114 +/- 27 hours of support without complications, respectively. Mean duration of ICU stay was 37 +/- 23 days.

CONCLUSIONS

Quick encouragement of ECMO for the temporary management of gas exchange may increase survival rates in trauma patients with ARDS.

Alpha glucocorticoid receptor expression in different experimental rat models of acute lung injury

BACKGROUND AND OBJECTIVES

Acute respiratory distress syndrome (ARDS) is a frequent form of hypoxiemic respiratory failure caused by the acute development of diffuse lung inflammation. Dysregulated systemic inflammation with persistent elevation of circulating inflammatory cytokines is the pathogenetic mechanism for pulmonary and extrapulmonary organ dysfunction in patients with ARDS. Glucocorticoids (GCs) have a broad range of inhibitory inflammatory effects, including inhibition of cytokines transcription, cellular activation and growth factor production. They inhibit the inflammatory pathways through two specific intracellular glucocorticoid receptors (GRs), named GR alpha and GR beta. The aim of our study was to evaluate the histologic evidence of inflammatory injury and the GR alpha uptake of resident and inflammatory cells in different experimental models of acute lung injury (ALI).

METHODS

We studied four groups of rats: three different experimental rat models of lung injury and a control group. The ALI was caused by barotrauma (due to an overventilation), oleic acid injection and mechanical ventilation. Results were compared to nonventilated rat control group. The duration of mechanical ventilation was of 2.5h. At the end of each experiment, rats were sacrificed. Lung biopsies were evaluated for morphologic changes. The immunohistochemistry was performed to study GR alpha expression.

RESULTS

Histologic evidence of lung injury (alveolar and interstitial edema, vascular congestion, alveolar haemorrhage, emphysema, number of interstitial cells and neutrophils, and destruction of alveolar attachments) were present in all ventilated groups. Barotrauma lead to an additional inflammatory response. GR alpha expression significantly increased in the three ventilated groups compared with nonventilated groups. GR alpha expression was highest in barotrauma group.

CONCLUSIONS

These data indicate that ALI is associated with diffuse alveolar damage, up-regulation of the inflammatory response and GR alpha overexpression. Barotrauma is the most effective mechanism inducing acute lung inflammation and GR alpha overexpression.

Early activity is feasible and safe in respiratory failure patients*

OBJECTIVE

To determine whether early activity is feasible and safe in respiratory failure patients.

DESIGN

Prospective cohort study.

SETTING

From June 1, 2003, through December 31, 2003, we assessed safety and feasibility of early activity in all consecutive respiratory failure patients who required mechanical ventilation for >4 days admitted to our respiratory intensive care unit (RICU). A majority of patients were treated in another intensive care unit (ICU) before RICU admission. We excluded patients who required mechanical ventilation for < or =4 days.

PATIENTS

Eight-bed RICU at LDS Hospital.

INTERVENTIONS

We assessed patients for early activity as part of routine respiratory ICU care. We prospectively recorded activity events and adverse events. We defined three activity events as sit on bed, sit in chair, and ambulate. We defined six activity-related adverse events as fall to knees, tube removal, systolic blood pressure >200 mm Hg, systolic blood pressure <90 mm Hg, oxygen desaturation <80%, and extubation.

MEASUREMENTS AND MAIN RESULTS

During the study period, we conducted a total of 1,449 activity events in 103 patients. The activity events included 233 (16%) sit on bed, 454 (31%) sit in chair, and 762 (53%) ambulate. In patients with an endotracheal tube in place, there were a total of 593 activity events, of which 249 (42%) were ambulation. There were <1% activity-related adverse events, including fall to the knees without injury, feeding tube removal, systolic blood pressure >200 mm Hg, systolic blood pressure <90 mm Hg, and desaturation <80%. No patient was extubated during activity.

CONCLUSIONS

We conclude that early activity is feasible and safe in respiratory failure patients. A majority of survivors (69%) were able to ambulate >100 feet at RICU discharge. Early activity is a candidate therapy to prevent or treat the neuromuscular complications of critical illness.

[Cohort study on incidence of ARDS in patients admitted to the ICU and prognostic factors of mortality]

OBJECTIVE

Analyze acute respiratory distress syndrome (ARDS) in patients admitted to an Intensive Care Medicine Service (ICMS) and prognostic factors of mortality in these patients.

DESIGN

Prospective study of all the patients admitted consecutively in the ICMS from January 1998 to February 2003.

SCOPE

ICMS of a third level university site with 32 beds in its General Area and 10 beds in the Traumatology Area.

PATIENTS

Patients who met the ARDS criteria of the European-North American Consensus Conference at any time during admission in ICMS. ENDPOINTS OF INTEREST: Mortality at 28 days.

RESULTS

One hundred and ninety-one patients (3.4 of all the admissions in ICMS) had ARDS criteria. The origin of ARDS was intrapulmonary in 63%. A total of 77% of the patients had multiorgan dysfunction and 26% respiratory superinfection. Median stay in the ICMS was 20 days. Mortality at 28 days was 48% and hospital mortality 58%. Multivariant analysis showed that the variables associated independently with an increase in mortality were the following: APACHE II > 22 (odds ratio [OR] 2.7; 95% CI: 1.3-5.8; p = 0.007), minimum PaO2/FIO2 during evolution of ARDS < 81 mmHg (odds ratio 5.5; 95% CI: 2.6-11.9; p < 0.0001), dysfunction > or = 3 organs (odds ratio 11.8; 95% CI: 2.5-55.4; p = 0.002).

CONCLUSIONS

ARDS is an entity with elevated mortality whose prognosis is associated not only with the seriousness of pulmonary function deterioration but also of systemic function, on which some treatment could modulate its evolution.

Life-threatening pulmonary hypertension and right ventricular failure complicating calcium and phosphate replacement in the intensive care unit

A 43-year-old man developed septic shock and acute lung injury after surgery to drain an ischiorectal abscess. In the intensive care unit he initially improved but developed severe hypoxaemia, right ventricular failure and pulmonary hypertension 90 min after receiving intravenous calcium gluconate and potassium phosphate, best explained by the formation of a calcium-phosphate precipitant that resulted in aggregate anaphylaxis. His rapid deterioration and lack of response to conventional therapies necessitated support with extracorporeal membrane oxygenation that was life saving. This adverse event has altered local practice regarding calcium and phosphate replacement and has implications for all intensive care units.

Two-Year Cognitive, Emotional, and Quality-of-Life Outcomes in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) has a high mortality and is associated with significant morbidity. Prior outcome studies have focused predominant on short-term outcomes (6-12 months). We assessed longitudinal neurocognitive, emotional, and quality of life in ARDS survivors at hospital discharge, and 1 and 2 years after hospital discharge using neuropsychologic tests and emotional and quality-of-life questionnaires. Neurocognitive sequelae occurred in 73% (54 of 74) of ARDS survivors at hospital discharge, 46% (30 of 66) at 1 year, and 47% (29 of 62) at 2 years. ARDS survivors report moderate to severe depression (16% and 23%) and anxiety (24% and 23%) at 1 and 2 years, respectively. The ARDS survivors had decreased quality of life, with the physical domains improving at 1 year, with no additional change at 2 years. Role emotional, pain, and general health did not change from hospital discharge to 2 years. Mental health improved during the first year and declined at 2 years. ARDS results in significant neurocognitive and emotional morbidity and decreased quality of life that persists at least 2 years after hospital discharge. ARDS can cause significant long-term, brain-related morbidity manifest by neurocognitive impairments and decreased quality of life.

Pediatric acute lung injury: prospective evaluation of risk factors associated with mortality

RATIONALE

The 1994 American European Consensus Committee definitions of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) have not been applied systematically in the pediatric population.

OBJECTIVES

The purpose of this study was to evaluate prospectively the epidemiology and clinical risk factors associated with death and prolonged mechanical ventilation in all pediatric patients admitted to two large, pediatric intensive care units with ALI/ARDS using Consensus criteria.

METHODS

All pediatric patients meeting Consensus Committee definitions for ALI were prospectively identified and included in a relational database.

MEASUREMENTS AND MAIN RESULTS

There were 328 admissions for ALI/ARDS with a mortality of 22%. Multivariate logistic regression analyses revealed (1) the initial severity of oxygenation defect, as measured by the Pa(O2)/FI(O2) ratio; (2) the presence of nonpulmonary and non-central nervous system (CNS) organ dysfunction; and (3) the presence of CNS dysfunction were independently associated with mortality and prolonged mechanical ventilation. A substantial fraction of patients (28%) did not require mechanical ventilation at the onset of ALI; 46% of these patients eventually required intubation for worsening ALI.

CONCLUSIONS

Mortality in pediatric ALI/ARDS is high and several risk factors have major prognostic value. In contrast to ALI/ARDS in adults, the initial severity of arterial hypoxemia in children correlates well with mortality. A significant fraction of patients with pediatric ALI/ARDS can be identified before endotracheal intubation is required. These patients provide a valuable group in whom new therapies can be tested.

Quality of life, emotional, and cognitive function following acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) is characterized by lung injury and hypoxemia, has a high mortality rate, and is associated with significant morbidity including cognitive and emotional sequelae and decreased quality of life. There is limited information regarding which of these factors are associated with decreased quality of life. This study assessed the relationships between quality of life, cognitive and emotional function in ARDS survivors at 1-year post-hospital discharge. Sixty-six ARDS survivors were administered a battery of neuropsychological tests, measures of emotional function and quality of life 1 year post-hospital discharge. At 1 year 45% of the ARDS patients had cognitive sequelae and 29% had mild to moderate symptoms of depression and anxiety. Depression, anxiety, and intensive care unit length of stay were significantly correlated with decreased quality of life. Cognitive impairments did not correlate with decreased quality of life. Illness severity and emotional function, but not cognitive sequelae, are associated with decreased quality of life 1 year following ARDS. ARDS is common and may result in significant cognitive and emotional morbidity and decreased quality of life.

Extracorporeal gas exchange with the DeltaStream rotary blood pump in experimental lung injury

In most severe cases of the acute respiratory distress syndrome, veno-venous extracorporeal membrane oxygenation (ECMO) can be used to facilitate gas exchange. However, the clinical use is limited due to the size and the concomitant risk of severe adverse events of conventionally-used centrifugal blood pumps with high extracorporeal blood volumes. The DeltaStream blood pump is a small-sized rotary blood pump that may reduce extracorporeal blood volume, foreign surfaces, contact activation of the coagulation system, and blood trauma. The aim of the present study was to test the safety and efficacy of the DeltaStream pump for ECMO in animals with normal lung function and experimental acute lung injury (ALI). Therefore, veno-venous ECMO was performed for 6 hours in mechanically ventilated pigs with normal lung function (n=6) and with ALI induced by repeated lung lavage (n=6) with a blood flow of 30% of the cardiac output. Gas flow with a FiO2 of 1.0 was set to equal blood flow. With a mean activated clotting time of 121 +/- 22 s, no circulatory impairment or thrombus formation was revealed during ECMO. Furthermore, free plasma Hb did not increase. In controls, hemodynamics and gas exchange remained unchanged. In animals with ALI, hemodynamics remained stable and gas transfer across the extracorporeal oxygenators was optimal, but only in 2 animals was a marked increase in PaO2 observed. CO2 removal was efficacious in all animals. We concluded that the DeltaStream blood pump may be used for veno-venous ECMO without major blood damage or hemodynamic impairment.

Pulmonary function and health-related quality of life in survivors of acute respiratory distress syndrome

Although survival rates for acute respiratory distress syndrome have increased, there is only limited information regarding the quality of life and the relationship between quality of life and pulmonary function after survival. We prospectively measured pulmonary function, emotional function, and health-related quality of life in a cohort of acute respiratory distress syndrome survivors recruited from patients who were enrolled in a randomized clinical trial of high versus low tidal volume mechanical ventilation at 1 year after their recovery. No significant differences were found between the patients treated with high and low tidal volumes on any pulmonary function measure. Approximately 80% of the patients in both groups demonstrated reduced diffusing capacity; 20% had airflow obstruction, and 20% had chest restriction. Scores on measures of depression and anxiety were within the normal ranges, suggesting that they did not have significant affective symptoms. However, both groups reported decreased health-related quality of life in physical functioning, physical ability to maintain their roles (role-physical), bodily pain, general health, and vitality (energy) on the Medical Outcome Study Short Form Health Survey with similar physical limitations reported on the Sickness Impact Profile questionnaire. The pulmonary function abnormalities correlated with decreased health-related quality of life for domains reflecting physical function. Acute respiratory distress syndrome survivors treated with high and low tidal volumes have abnormal pulmonary function that was related to decreased health-related quality of life 1 year after hospital discharge.

Computerized decision support for mechanical ventilation of trauma induced ARDS: results of a randomized clinical trial

BACKGROUND

Variability and logistic complexity of mechanical ventilatory support of acute respiratory distress syndrome, and need to standardize care among all clinicians and patients, led University of Utah/LDS Hospital physicians, nurses, and engineers to develop a comprehensive computerized protocol. This bedside decision support system was the basis of a multicenter clinical trial (1993-1998) that showed ability to export a computerized protocol to other sites and improved efficacy with computer- versus physician-directed ventilatory support. The Memorial Hermann Hospital Shock Trauma intensive care unit (ICU) (Houston, TX; a Level I trauma center and teaching affiliate of The University of Texas Houston Medical School) served as one of the 10 trial sites and recruited two thirds of the trauma patients. Results from the trauma patient subgroup at this site are reported to answer three questions: Can a computerized protocol be successfully exported to a trauma ICU? Was ventilator management different between study groups? Was patient outcome affected?

METHODS

Sixty-seven trauma patients were randomized at the Memorial Hermann Shock Trauma ICU site. "Protocol" assigned patients had ventilatory support directed by the bedside respiratory therapist using the computerized protocol. "Nonprotocol" patients were managed by physician orders.

RESULTS

Of the 67 trauma patients randomized, 33 were protocol (age 40 +/- 3; Injury Severity Score [ISS] 26 +/- 3; 73% blunt) and 34 were nonprotocol (age 38 +/- 2; ISS 25 +/- 2; 76% blunt). For the protocol group, the computerized protocol was used 96% of the time of ventilatory support and 95% of computer-generated instructions were followed by the bedside respiratory therapist. Outcome measures (i.e., survival, ICU length of stay, morbidity, and barotrauma) were not significantly different between groups. Fio2 > or = 0.6 and Pplateau > or = 35 cm H2O exposures were less for the protocol group.

CONCLUSION

A computerized protocol for bedside decision support was successfully exported to a trauma center, and effectively standardized mechanical ventilatory support of trauma-induced acute respiratory distress syndrome without adverse effect on patient outcome.

Emerging trends in ICU management and staffing

It is likely that greater on-site intensivist coverage in critical care units will be observed in the future. Regionalization of critical care services will make this a financial reality because this level of expertise cannot realistically be provided to all hospitals. Perhaps units above a certain size will warrant this level of coverage and smaller community hospitals will transfer patients in need of a very high level of service, which can be provided only by intensivists on site. Community hospitals may rely on specially trained nurse practitioners or physician assistants to provide more on-site coverage during off hours. As technology advances, telemedicine will play a greater role in providing intensivist coverage to ICUs during off hours or to community hospitals in remote areas. Advanced technology and reorganization of critical care services offer opportunities for creative and nontraditional ways to deliver improved care to patients.

Mechanical ventilation in acute lung injury and acute respiratory distress syndrome

Mechanical ventilation provides life-sustaining support for most patients with acute lung injury and acute respiratory distress syndrome; however, traditional approaches to mechanical ventilation may cause ventilator-associated lung injury, which could exacerbate or perpetuate respiratory failure caused initially by conditions such as pneumonia, sepsis, and trauma. This article reviews the theory, laboratory data, and results of recent clinical trials that suggest that modified ventilator strategies can reduce ventilator-associated lung injury and improve clinical outcomes.

Thirty years of clinical trials in acute respiratory distress syndrome

OBJECTIVE

To systematically review clinical trials in acute respiratory distress syndrome (ARDS).

DATA SOURCES

Computerized bibliographic search of published research and citation review of relevant articles.

STUDY SELECTION

All clinical trials of therapies for ARDS were reviewed. Therapies that have been compared in prospective, randomized trials were the focus of this analysis.

DATA EXTRACTION

Data on population, interventions, and outcomes were obtained by review. Studies were graded for quality of scientific evidence.

MAIN RESULTS

Lung protective ventilator strategy is supported by improved outcome in a single large, prospective trial and a second smaller trial. Other therapies for ARDS, including noninvasive positive pressure ventilation, inverse ratio ventilation, fluid restriction, inhaled nitric oxide, almitrine, prostacyclin, liquid ventilation, surfactant, and immune-modulating therapies, cannot be recommended at this time. Results of small trials using corticosteroids in late ARDS support the need for confirmatory large clinical trials.

CONCLUSIONS

Lung protective ventilator strategy is the first therapy found to improve outcome in ARDS. Trials of prone ventilation and fluid restriction in ARDS and corticosteroids in late ARDS support the need for large, prospective, randomized trials.

Extracorporeal membrane oxygenation: a ten-year experience

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a supportive therapy used for severe acute respiratory distress syndrome (ARDS). We present outcome, clinical parameters, and complications in a cohort of 245 ARDS patients of whom 62 were treated with ECMO.

METHODS

Data of all ARDS patients were prospectively collected between 1991 and 1999. Outcome and clinical parameters of patients treated with and without ECMO were evaluated.

RESULTS

One hundred thirty-eight patients were referred from other hospitals, 107 were primarily located in our hospital. About one fourth of these patients were treated with ECMO. The survival rate was 55% in ECMO patients and 61% in non-ECMO patients.

CONCLUSIONS

ECMO is a therapeutic option for patients with severe ARDS, likely to increase survival. However, a randomized controlled study proving its benefit is still awaited. Until the development of a causal or otherwise superior therapy ECMO should be used in selected patients.

Interhospital transport of the extremely ill patient: the mobile intensive care unit

BACKGROUND

Critically ill patients may require specialized care that is offered only at tertiary referral centers. As regionalization and specialization of critical care become more common, transportation of critically ill patients must be refined. Transportation of critically ill patients within a hospital, much less outside the hospital, is often deemed unsafe because of medical instability. We report, here, our results from 2 yrs' experience of transporting extremely ill patients with respiratory failure via a ground critical care transport service.

METHODS

A mobile intensive care unit was equipped and staffed to nearly recreate the intensive care environment. Staffing included a physician, nurse, respiratory therapist, and driver--all with extensive critical care experience. The mobile intensive care unit was equipped with a full pharmacy, advanced ventilatory equipment, and capability for full invasive hemodynamic monitoring. Data were analyzed by retrospective review. The predicted mortality rate, based on Pao2/Fio2 ratios, was compared with the actual mortality rate.

RESULTS

During a 2-yr period, 39 critically ill patients were transported. Thirty-six of the 39 were candidates for extracorporeal lung assist, with a mean positive end-expiratory pressure requirement of 15.9, a mean Fio2 requirement of .93, and a mean Pao2/Fio2 ratio of 59.8. Pulmonary arterial catheters and peripheral arterial catheters were in place in 66.6% and 72% of patients, respectively. Vasoactive medications were being infused in 56%, and 74% were receiving medical paralytics. One patient died during movement from the bed to the transport gurney. Other than one episode of transient hypotension, there were no complications or untoward outcomes related to transport. Unique therapeutic interventions were performed at the receiving facility on 34 of 39 patients. The predicted mortality rate, based on indicators of lung dysfunction, was 68% to 100%; the actual subsequent hospital mortality rate was 43%.

CONCLUSIONS

When a mobile intensive care unit is properly staffed and equipped and patient stabilization is performed before transfer, severely ill patients with respiratory failure can be transferred safely. For patients with respiratory failure, there may be a survival advantage in transfer to regional centers of expertise.

Prospective, randomized, controlled clinical trial comparing traditional versus reduced tidal volume ventilation in acute respiratory distress syndrome patients

OBJECTIVE

To assess the safety and potential efficacy of a mechanical ventilation strategy designed to reduce stretch-induced lung injury in acute respiratory distress syndrome.

DESIGN

Prospective, randomized, controlled clinical trial.

SETTING

Eight intensive care units in four teaching hospitals.

PATIENTS

Fifty-two patients with acute respiratory distress syndrome.

INTERVENTIONS

Traditional tidal volume patients: tidal volume 10-12 mL/kg ideal body weight, reduced if inspiratory plateau pressure was > 55 cm H2O (7.3 kPa). Small tidal volume patients: tidal volume 5-8 mL/kg ideal body weight, to keep plateau pressure < 30 cm H2O (4.0 kPa).

MEASUREMENTS AND MAIN RESULTS

Mean tidal volumes during the first 5 days in traditional and small tidal volume patients were 10.2 and 7.3 mL/kg, respectively (p < .001), with mean plateau pressure = 30.6 and 24.9 cm H2O (3.3 kPa), respectively (p < .001). There were no significant differences in requirements for positive end-expiratory pressure or FIO2, fluid intakes/outputs, requirements for vasopressors, sedatives, or neuromuscular blocking agents, percentage of patients that achieved unassisted breathing, ventilator days, or mortality.

CONCLUSIONS

The reduced tidal volume strategy used in this study was safe. Failure to observe beneficial effects of small tidal volume ventilation treatment in important clinical outcome variables may have occurred because a) the sample size was too small to discern small treatment effects; b) the differences in tidal volumes and plateau pressures were modest; or c) reduced tidal volume ventilation is not beneficial.

Ventilation in the trauma and surgical patient

Changes in the understanding of the pathophysiology of ARDS and effects of mechanical ventilation with high pressures have led to treatment strategies that resulted in improved survival rates. The central principle in these strategies is to avoid ventilation induced lung injury by allowing the lungs to rest. A number of promising new treatments emphasizing this principle are under investigation. Physicians caring for patients who develop ARDS should make every effort to avoid alveolar overdistention by ventilating patients in the compliant portion of pressure-flow loop and avoid peak inspiratory pressures in excess of 40 cm H2O.

Acute lung injury in the medical ICU: comorbid conditions, age, etiology, and hospital outcome

The independent effects of chronic disease, age, severity of illness, lung injury score (LIS) and etiology, and preceding nonpulmonary organ-system dysfunction (OSD) on the outcome of acute lung injury (ALI) have not been examined in an exclusively medical-intensive-care-unit (MICU) population. Therefore, 107 consecutive MICU patients with ALI (76% with acute respiratory distress syndrome [ARDS]) were prospectively investigated. The impact of comorbidities, age > 65 yr, acute physiology score (APS), LIS, etiology of ALI, and OSD on hospital survival were studied. The overall mortality was 62 of 107 patients (58%), including 47 (58%) with ARDS. With univariate analysis, age > 65 yr, organ transplantation, human immunodeficiency virus (HIV) infection, active malignancy, chronic steroid use, and a septic or aspiration-related etiology of ALI were associated with a > or = 1.2-fold greater relative risk (RR) of hospital mortality. With multiple logistic regression, independent predictors of hospital death were age > 65 yr, organ transplantation, HIV infection, cirrhosis, active malignancy, and sepsis. APS, LIS, aspiration-related etiology of ALI, preceding OSD, and other comorbidities were not independently predictive of hospital death. Multivariate analysis of the ARDS cohort showed similar results, although cirrhosis and malignancy did not reach statistical significance. We conclude that comorbid conditions, older age, and sepsis etiology are independent predictors of hospital death in exclusively MICU patients with ALI (76% of whom satisfied criteria for ARDS). These factors should be considered in analyzing studies of new therapies and interpreting trends in mortality for ALI and ARDS.

An approach to the treatment of severe adult respiratory failure

OBJECTIVES

The purpose of this article is to evaluate outcome in adult patients with severe respiratory failure managed with an approach using (1) limitation of end inspiratory pressure, (2) inverse ratio ventilation, (3) titration of PEEP by SvO2, (4) intermittent prone positioning, (5) limitation of FiO2, (6) diuresis, (7) transfusion, and (8) extracorporeal life support (ECLS) if patients failed to respond.

PATIENTS AND METHODS

This study was designed as a retrospective review in the intensive care unit of a tertiary referral hospital. One-hundred forty-one consecutive patients with hypoxic (n = 135) or hypercarbic (n = 6) respiratory failure referred for consideration of ECLS between 1990 and 1996. Overall, initial PaO2/FiO2 (P/F) ratio was 75+/-5 (median = 66).

RESULTS

Lung recovery occurred in 67% of patients and 62% survived. Forty-one patients improved without ECLS (83% survived); 100 did not and were supported with ECLS (54% survived). Survival was greater in patients cannulated within 12 hours of arrival (59%) compared with those cannulated after 12 hours (40%, P < .05). Multiple logistic regression identified age, duration of mechanical ventilation before transfer, four or more dysfunctional organs, and the requirement for ECLS as independent predictors of mortality.

CONCLUSIONS

An approach that emphasizes lung protection and early implementation of extracorporeal life support is associated with high rates of survival in patients with severe respiratory failure.

The relation of pneumothorax and other air leaks to mortality in the acute respiratory distress syndrome

BACKGROUND

In patients with the acute respiratory distress syndrome, pneumothorax and other air leaks - any extrusion of air outside the tracheobronchial tree - have been attributed to high ventilatory pressures or volumes and linked to increased mortality.

METHODS

We analyzed data from a prospective trial of aerosolized synthetic surfactant in 725 patients with the acute respiratory distress syndrome induced by sepsis. We compared the ventilatory pressures and volumes in the patients without any air leaks (the highest values during the five-day study) with the pressures and volumes in those with pneumothorax or with any air leaks (the highest values during the 16- and 24-hour periods before the complication developed).

RESULTS

Fifty patients (6.9 percent) had pneumothorax and 77 (10.6 percent) had pneumothorax or other air leaks. There were no significant differences between patients with air leaks and those without air leaks in any pressure or volume examined. Overall mortality at 30 days was 40.0 percent (95 percent confidence interval, 36.4 to 43.6); among the patients with pneumothorax, it was 46.0 percent (95 percent confidence interval, 32.2 to 59.8), and among those without pneumothorax, it was 39.3 percent (95 percent confidence interval, 35.6 to 43.0; P=0.35). The mortality rate was 45.5 percent (95 percent confidence interval, 34.4 to 56.6) in the group with any air leaks and 39.0 percent (95 percent confidence interval, 35.3 to 42.8) in the group without air leaks (P=0.28).

CONCLUSIONS

In patients with sepsis-induced acute respiratory distress syndrome who were receiving mechanical ventilation with conventional pressures and volumes, there were no significant correlations between high ventilatory pressures or volumes and the development of pneumothorax or other air leaks. Pneumothorax or other air leaks were not associated with a significantly increased mortality rate.

Acute lung injury and the acute respiratory distress syndrome

OBJECTIVE

To review acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) in light of recent information about the definitions, epidemiology, pathophysiology, management, and outcome of these conditions.

DATA SOURCES

The author's personal files as well as the computerized MEDLINE database. STUDY SOLUTION: Studies were selected for their relevance to the conditions of ALI and ARDS.

DATA EXTRACTION

The author extracted all applicable data.

DATA SYNTHESIS

The diagnostic criteria for ALI and ARDS include a) acute onset; b) bilateral chest radiographic infiltrates; c) a pulmonary artery occlusion pressure of < or =18 mm Hg or no evidence of left atrial hypertension; and d) impaired oxygenation manifested by a PaO2/FIO2 ratio of < or =300 torr (< or =40 kPa) for ALI and < or =200 torr (< or =27 kPa) for ARDS. The incidence of ALI and ARDS are approximately 70 and 7 patients out of 100,000 of the total U.S. population per year, respectively. The conditions result from direct or indirect injury to the pulmonary epithelium and endothelium that causes edema, atelectasis, inflammation, and fibrosis. This "diffuse alveolar damage" is actually patchy in many patients. Therapy of ALI and ARDS is largely supportive, although new approaches in mechanical ventilation, patient positioning, and pharmacologic therapy have been introduced. The mortality rate of ARDS has improved to <50%, but the reasons for this improvement are unclear.

CONCLUSION

ALI and ARDS are better defined and understood than ever before, and their outcome has improved for unclear reasons.

Effects of inhaled nitric oxide and extracorporeal membrane oxygenation on pulmonary hemodynamics and lymph flow in oleic acid lung injury in sheep

OBJECTIVE

To compare the effects of inhaled nitric oxide (NO) and extracorporeal membrane oxygenation (ECMO) on oxygenation, hemodynamics, and lymphatic drainage in an oleic acid lung injury model in sheep.

DESIGN

Prospective, randomized study.

SETTING

Animal research laboratory.

ANIMALS

Thirty female sheep, weighing 35 to 40 kg.

INTERVENTIONS

Acute lung injury was induced by central venous injection of oleic acid (0.5 mL/kg body weight). A chronic lymph fistula had been prepared through a right thoracotomy 3 days before the experiment. Animals were assigned randomly to the NO group (n = 14) or the ECMO group (n = 16). When a lung injury score of > 2.5 was achieved, the animals were given NO in dosage increments of 2, 5, 10, 20, and 40 parts per million (ppm), or placed on ECMO with an FIO2 of 0.21 (ECMO-21) and then 1.0 (ECMO-100) at the oxygenator. Mechanical ventilator parameters were kept constant to isolate the effects of NO and ECMO on systemic and pulmonary hemodynamics, cardiac output, oxygenation parameters, lymph/plasma protein ratio, and lymph flow. Measurements and calculations were performed after 1 hr at each individual step of NO concentration or FIO2.

MEASUREMENTS AND MAIN RESULTS

In the ECMO group, PVRI and MPAP did not change and were significantly different from the NO group. In the NO group, there was a dose-dependent decrease in venous admixture, maximal at 10 ppm NO and decreasing from 40 +/- 6% to 23 +/- 10% (p < .05). This decrease was significantly different from the ECMO group, where there was no change. There was a significant increase in PaO2/FIO2 in the NO group, maximal at 10 ppm NO (84 +/- 11 to 210 +/- 90, p < .05), but a greater increase in PaO2/FIO2 on ECMO-21 (81 +/- 14 to 265 +/- 63) and a further increase on ECMO-100 (398 +/- 100) (p < .05). The lymph/plasma protein ratio remained unchanged in both groups after induction of lung injury by oleic acid. However, lymph flow decreased by 11 +/- 6% in the NO group, whereas it increased by 14 +/- 17% in the ECMO group (p < .05).

CONCLUSIONS

In an oleic acid-induced sheep model of acute lung injury, there were significant differences between the effects of NO and ECMO on acute pulmonary hypertension, hypoxemia, hypercarbia, and lymph flow. NO significantly decreases pulmonary hypertension, whereas pulmonary hemodynamics were not substantially affected by ECMO. Both interventions reversed hypoxemia, but ECMO did so to a greater degree, and only ECMO improved hypercarbia. Only NO decreased lymph flow, possibly as an effect of decreased microvascular filtration pressure. This study did not attempt to evaluate the impact of these interventions on ventilatory requirements, barotrauma, or outcome. However, this model suggests that NO therapy may moderate pulmonary hypertension and improve lymph flow in acute lung injury. Clinical studies are needed to assess whether NO therapy might be beneficial in treatment of severe acute lung injury in older children and adults.

Extracorporeal life support for 100 adult patients with severe respiratory failure

OBJECTIVE

The authors retrospectively reviewed their experience with extracorporeal life support (ECLS) in 100 adult patients with severe respiratory failure (ARF) to define techniques, characterize its efficacy and utilization, and determine predictors of outcome.

SUMMARY BACKGROUND DATA

Extracorporeal life support maintains gas exchange during ARF, providing diseased lungs an optimal environment in which to heal. Extracorporeal life support has been successful in the treatment of respiratory failure in infants and children. In 1990, the authors instituted a standardized protocol for treatment of severe ARF in adults, which included ECLS when less invasive methods failed.

METHODS

From January 1990 to July 1996, the authors used ECLS for 100 adults with severe acute hypoxemic respiratory failure (n = 94): paO2/FiO2 ratio of 55.7+/-15.9, transpulmonary shunt (Qs/Qt) of 52+/-22%, or acute hypercarbic respiratory failure (n = 6): paCO2 84.0+/-31.5 mmHg, despite and after maximal conventional ventilation. The technique included venovenous percutaneous access, lung "rest," transport on ECLS, minimal anticoagulation, hemofiltration, and optimal systemic oxygen delivery.

RESULTS

Overall hospital survival was 54%. The duration of ECLS was 271.9+/-248.6 hours. Primary diagnoses included pneumonia (49 cases, 53% survived), adult respiratory distress syndrome (45 cases, 51 % survived), and airway support (6 cases, 83% survived). Multivariate logistic regression modeling identified the following pre-ECLS variables significant independent predictors of outcome: 1) pre-ECLS days of mechanical ventilation (p = 0.0003), 2) pre-ECLS paO2/FiO2 ratio (p = 0.002), and 3) age (years) (p = 0.005). Modeling of variables during ECLS showed that no mechanical complications were independent predictors of outcome, and the only patient-related complications associated with outcome were the presence of renal failure (p < 0.0001) and significant surgical site bleeding (p = 0.0005).

CONCLUSIONS

Extracorporeal life support provides life support for ARF in adults, allowing time for injured lungs to recover. In 100 patients selected for high mortality risk despite and after optimal conventional treatment, 54% survived. Extracorporeal life support is extraordinary but reasonable treatment in severe adult respiratory failure. Predictors of survival exist that may be useful for patient prognostication and design of future prospective studies.

Extracorporeal membrane oxygenation for adult respiratory failure

OBJECTIVES

To review the first 50 patients to receive extracorporeal membrane oxygenation (ECMO) for respiratory failure at Glenfield Hospital, and to compare them with published series of patients receiving positive pressure ventilation.

DESIGN

Retrospective chart review.

SETTING

Extracorporeal Life Support Organization/European Extracorporeal Life Support Organization recognized ECMO center.

PATIENTS

Fifty consecutive patients referred for ECMO with respiratory failure refractory to conventional management between 1989 and 1995.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Primary end point was survival to hospital discharge, 66%. Other data (mean and SD): Murray Lung Injury Score, 3.4 (0.5); ratio of PaO2 to fraction of inspired oxygen, 65 (36.9) mm Hg; duration of ventilation pre-ECMO, 76.5 (83.7 h); peak airway pressure, 39.6 (7.4) cm H2O; end-expiratory pressure, 10 (3.3) cm H2O; minute ventilation, 12.6 (3.32) L/min; age, 30.1 (10.8) years; duration of ECMO, 207.4 (177.8) h; and units of blood transfused, 19 (17.3). Survival was significantly better than two previously reported series of patients receiving positive pressure ventilation (55.6% and 42% survival), p=0.036 and p=0.0006. Odds ratio for improved survival was 0.46 (95% confidence interval, 0.22 to 0.97, p=0.036).

CONCLUSIONS

Survival with ECMO is 66% for adults with severe respiratory failure. ECMO should be considered in patients who remain hypoxic despite maximal positive pressure ventilation.

Increased mortality of older patients with acute respiratory distress syndrome

OBJECTIVE

To examine the relationship between age and mortality in ARDS patients and evaluate the importance of factors that increase the mortality of older ARDS patients.

DESIGN

Prospective inception cohort study.

SETTING

Community-based referral hospital.

PATIENTS

Two hundred fifty-six ARDS patients identified from May 1987 to December 1990. ARDS was defined by the following: (1) PaO2/PAO2 < or = 0.2; (2) pulmonary capillary wedge pressure < or = 15 mm Hg; (3) total static thoracic compliance < or = 50 mL/cm H2O; (4) bilateral infiltrates on chest radiograph; and (5) an appropriate clinical setting for ARDS.

MAIN OUTCOME MEASURES

Comparison of organ failure, incidence of sepsis, patient demographics, arterial oxygenation, and level of support in those 55 years and younger and those older than 55 years of age. Withdrawal of support in patients who died.

RESULTS

Seventy-two of 112 patients older than 55 years (64%) died vs 65 of 144 patients 55 years and younger (45%) (p = 0.002). Examination of patient groups using age identified older than 55 years as a "cutpoint" above which mortality was greater (p = 0.002). Older nonsurvivors did not differ from nonsurvivors 55 years or younger with respect to gender, smoking history, ARDS risk factors, ARDS identifying characteristics, APACHE II (acute physiology and chronic health evaluation), number of organ failures, or the incidence of sepsis. In the 48 h prior to death, nonsurvivors 55 years and younger had more organ failure (3.4 +/- 0.2 vs 2.8 +/- 0.2; p = 0.03), higher fraction of inspired oxygen (0.82 +/- 0.03 vs 0.68 +/- 0.03; p = 0.008), and higher positive end-expiratory pressure levels (13 +/- 1 vs 8 +/- 1; p = 0.001) than older nonsurvivors. Despite more severe expression of disease, only 32 (50%) nonsurvivors 55 years and younger had support withdrawn. Significantly more nonsurvivors older than 55 years (73%) had support withdrawn (p = 0.009). Even in the absence of chronic disease states, withdrawal was more likely for patients older than 55 years (21/51) than in those 55 years and younger (3/32; p < 0.001).

CONCLUSIONS

Mortality is significantly higher for patients with ARDS older than 55 years. Decisions to withdraw support are made more often in ARDS patients older than 55 years. These data suggest that age bias may influence decisions to withdraw support.

Alveolar overdistension is an important mechanism of persistent lung damage following severe protracted ARDS

It is now widely accepted that mechanical ventilation may damage the lung, but the mechanism of lung damage is not clear. Possible causes include overdistension of aerated alveoli by inappropriately large tidal volumes (volutrauma), shear stresses generated during the recruitment and de-recruitment of lung units at the junction of aerated and collapsed lung, and infective or ischaemic necrosis of persistently collapsed lung. Computerized tomography allows noninvasive assessment of lung structure during and after acute lung injury, and may provide insight into the mechanism of lung damage. Using serial high resolution computed tomography we documented lung structure one month after recovery from severe protracted adult respiratory distress syndrome (ARDS) in three patients who required mechanical ventilation for between 86 and 97 days; the computed tomograms were repeated at between 5 and 14 months. All three patients had persistent abnormalities of lung structure which were most marked in the anterior regions of the lung. These findings suggest that overdistension of non-dependent lung regions in the main mechanism of lung damage persisting after recovery from severe protracted ARDS.