The acute respiratory distress syndrome is a common, devastating clinical syndrome of acute lung injury that affects both medical and surgical patients. Since the last review of this syndrome appeared in the Journal, 1 more uniform definitions have been devised and important advances have occurred in the understanding of the epidemiology, natural history, and pathogenesis of the disease, leading to the design and testing of new treatment strategies. This article provides an overview of the definitions, clinical features, and epidemiology of the acute respiratory distress syndrome and discusses advances in the areas of pathogenesis, resolution, and treatment. Historical Perspective and Definitions . . .

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The acute respiratory distress syndrome

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(09)61069-2.pdf

Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial.

Introduction: Ventilator-induced Lung Injury: Not Only Air Leaks Ventilation-induced Pulmonary Edema and Related Findings: A Historical Perspective Ventilation-induced Pulmonary Edema: Hydrostatic or Permeability Edema? Experimental Evidence for Increased Vascular Transmural Pressure Evidence for Alterations in Alveolar–Capillary Permeability Contributions of the Static and Dynamic Lung Volume Components to Ventilator-induced Edema High-volume Lung Edema Low Lung Volume Injury Effects of High-volume Ventilation on Abnormal Lungs Effects of High-volume Ventilation on Injured Lungs Interaction between Severe Alveolar Flooding and Mechanical Ventilation Effects of Resting the Lung on Ventilator-induced Lung Injury Possible Mechanisms of Ventilation-induced Lung Injury Mechanisms of Increased Vascular Transmural Pressure Mechanisms of Altered Permeability Clinical Relevance

Ventilator-induced lung injury: lessons from experimental studies.

Background As more patients survive the acute respiratory distress syndrome, an understanding of the long-term outcomes of this condition is needed. Methods We evaluated 109 survivors of the acute respiratory distress syndrome 3, 6, and 12 months after discharge from the intensive care unit. At each visit, patients were interviewed and underwent a physical examination, pulmonary-function testing, a six-minute–walk test, and a quality-of-life evaluation. Results Patients who survived the acute respiratory distress syndrome were young (median age, 45 years) and severely ill (median Acute Physiology, Age, and Chronic Health Evaluation score, 23) and had a long stay in the intensive care unit (median, 25 days). Patients had lost 18 percent of their base-line body weight by the time they were discharged from the intensive care unit and stated that muscle weakness and fatigue were the reasons for their functional limitation. Lung volume and spirometric measurements were normal by 6 months, but carbon monoxide d...

https://www.nejm.org/doi/pdf/10.1056/NEJMoa022450

One-Year Outcomes in Survivors of the Acute Respiratory Distress Syndrome

The impact of a new therapy that includes pressure-controlled inverse ratio ventilation followed by extracorporeal CO2 removal on the survival of patients with severe ARDS was evaluated in a randomized controlled clinical trial. Computerized protocols generated around-the-clock instructions for management of arterial oxygenation to assure equivalent intensity of care for patients randomized to the new therapy limb and those randomized to the control, mechanical ventilation limb. We randomized 40 patients with severe ARDS who met the ECMO entry criteria. The main outcome measure was survival at 30 days after randomization. Survival was not significantly different in the 19 mechanical ventilation (42%) and 21 new therapy (extracorporeal) (33%) patients (p = 0.8). All deaths occurred within 30 days of randomization. Overall patient survival was 38% (15 of 40) and was about four times that expected from historical data (p = 0.0002). Extracorporeal treatment group survival was not significantly different from other published survival rates after extracorporeal CO2 removal. Mechanical ventilation patient group survival was significantly higher than the 12% derived from published data (p = 0.0001). Protocols controlled care 86% of the time. Average PaO2 was 59 mm Hg in both treatment groups. Intensity of care required to maintain arterial oxygenation was similar in both groups (2.6 and 2.6 PEEP changes/day; 4.3 and 5.0 FIO2 changes/day). We conclude that there was no significant difference in survival between the mechanical ventilation and the extracorporeal CO2 removal groups. We do not recommend extracorporeal support as a therapy for ARDS. Extracorporeal support for ARDS should be restricted to controlled clinical trials.

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome.

The impact of a new therapy that includes pressure-controlled inverse ratio ventilation followed by extracorporeal CO 2 removal on the survival of patients with severe ARDS was evaluated in a randomized controlled clinical trial. Computerized protocols generated around-the-clock instructions for management of arterial oxygenation to assure equivalent intensity of care for patients randomized to the new therapy limb and those randomized to the control, mechanical ventilation limb. We randomized 40 patients with severe ARDS who met the ECMO entry criteria. The main outcome measure was survival at 30 days after randomization

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome

To determine if measures of ARDS severity during the acute illness correlate with lung function after recovery from ARDS, we regressed lowest total thoracic compliance (CTH), initial intrapulmonary shunt fraction (Qsp/Qt), initial mean pulmonary artery pressure (PAP), maximal level of positive end-expiratory pressure (PEEP), time ventilated (Tvent), and time with FlO2 greater than 0.6 (TO2) against the percent of predicted FVC, TLC, and DLCO of 16 previously healthy, nonsmoking ARDS survivors. Pulmonary function tests were performed more than 1 yr after ARDS. Percent of predicted FVC correlated with CTH (r = 0.66, p less than 0.01) and PAP (r = 0.53, p less than 0.05), and percent of predicted TLC correlated with CTH (r = 0.71, p less than 0.01), PEEP (r = -0.55, p less than 0.05), and Qsp/Qt (r = -0.53, p less than 0.05). Only TO2 correlated with percent of predicted DLCO (r = -0.53, p less than 0.05). Five of 7 ARDS survivors with an abnormal DLCO were supported at FlO2 greater than 0.6 for more than 24 h, whereas all of 9 survivors with a normal DLCO received FlO2 greater than 0.6 for less than 24 h. We conclude that physiologic markers of ARDS severity during the acute illness correlate with residual pulmonary dysfunction after recovery from ARDS. Support with FlO2 greater than 0.6 for more than 24 h appears to be a sensitive and specific predictor of an abnormally reduced DLCO more than 1 yr after ARDS.

Prediction of pulmonary function abnormalities after adult respiratory distress syndrome (ARDS).

Open lung biopsy does not correlate with pulmonary function after the adult respiratory distress syndrome.

Ethical issues related to the use of computerized protocols to control mechanical ventilation of patients with Acute Respiratory Distress Syndrome (ARDS) are identical to the ethical issues surrounding the use of any therapy or intervention. Four ethical principles must be considered: nonmaleficence, beneficence, autonomy, and distributed justice. The major ethical challenges to computerized protocol use as a specific application of clinical decision support tools are found within the principles of nonmaleficence and of beneficence. The absence of credible outcome data on which ARDS patient survival probabilities with different therapeutic options could be based is a constraint common to most ICU clinical decision making. Clinicians are thus deprived of the knowledge necessary to define benefit and are limited to beneficent intention in clinical decisions. Computerized protocol controlled decision making for the clinical management of mechanical ventilation for ARDS patients is ethically defensible. It is as well supported as most ICU therapy options.

B Rasmusson

Papers

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome.

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome

Prediction of pulmonary function abnormalities after adult respiratory distress syndrome (ARDS).

Open lung biopsy does not correlate with pulmonary function after the adult respiratory distress syndrome.

Ethical implications of standardization of ICU care with computerized protocols.