Alan H. Morris

Report of the American-European Consensus Conference on acute respiratory distress syndrome: Definitions, mechanisms, relevant outcomes, and clinical trial coordination

The acute respiratory distress syndrome (ARDS), a process of nonhydrostatic pulmonary edema and hypoxemia associated with a variety of etiologies, carries a high morbidity rate, mortality rate (10% to 90%), and financial cost. The reported annual incidence in the United States is 150,000 cases, but this figure has been challenged and may be different in Europe. Part of the reason for these uncertainties is the heterogeneity of diseases underlying ARDS and the lack of uniform definitions for ARDS. Thus, those who wish to know the true incidence and outcome of this clinical syndrome are stymied. The European American Consensus Committee on ARDS was formed to focus on these issues and on the pathophysiologic mechanisms of the process. It was felt that international coordination between North America and Europe in clinical studies of ARDS was becoming increasingly important to address the recent plethora of potential therapeutic agents for the prevention and treatment of ARDS.

Effects of recruitment maneuvers in patients with acute lung injury and acute respiratory distress syndrome ventilated with high positive end-expiratory pressure.

ObjectivePositive end-expiratory pressure (PEEP) and recruitment maneuvers (RMs) may partially reverse atelectasis and reduce ventilation-associated lung injury. The purposes of this study were to assess a) magnitude and duration of RM effects on arterial oxygenation and on requirements for oxygenation support (Fio2/PEEP) in patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS) receiving ventilation with low tidal volumes and high levels of PEEP; and b) frequency of adverse respiratory and circulatory events attributable to RMs. DesignProspective, randomized, crossover study. SettingThirty-four intensive care units at 19 hospitals. PatientsSeventy-two patients with early ALI/ARDS. Baseline PEEP and Fio2 were 13.8 ± 3.0 cm H2O and 0.39 ± 0.10, respectively (mean ± sd). InterventionsWe conducted RMs by applying continuous positive airway pressure of 35–40 cm H2O for 30 secs. We conducted sham RMs on alternate days. We monitored oxyhemoglobin saturation by pulse oximetry (SpO2), Fio2/PEEP, blood pressure, and heart rate for 8 hrs after RMs and sham RMs. We examined chest radiographs for barotrauma. Measurements and Main ResultsResponses to RMs were variable. Greatest increments from baseline SpO2 within 10 mins after RMs were larger than after sham RMs (1.7 ± 0.2 vs. 0.6 ± 0.3 %, mean ± sem, p < .01). Systolic blood pressure decreased more within 10 mins after RMs (9.4 ± 1.1 vs. 3.1 ± 1.1 mm Hg, p < .01). Changes in Fio2/PEEP requirements were not significantly different at any time after RMs vs. sham RMs. Barotrauma was apparent on first radiographs after one RM and one sham RM. ConclusionsIn ALI/ARDS patients receiving mechanical ventilation with low tidal volumes and high PEEP, short-term effects of RMs as conducted in this study are variable. Beneficial effects on gas exchange in responders appear to be of brief duration. More information is needed to determine the role of recruitment maneuvers in the management of ALI/ARDS.

Is informed consent always necessary for randomized, controlled trials? .

Consider this paradox: if a physician reads a case report about a novel method of ventilation for critically ill patients and wants to try it in the next several patients with respiratory failure h...

A mathematical model of diamagnetic line broadening in lung tissue and similar heterogeneous systems: Calculations and measurements

Abstract In order to explain recently observed internal inhomogeneous broadening in lung tissue, we constructed and calculated diamagnetic field shifts for models consisting of a spherical shell of water and a hexagonally packed array of spherical air bubbles in water. For the spherical-shell model, the field equations were solved exactly for an arbitrary number of concentric shells. In contrast, in the hexagonal model, a Monte Carlo algorithm was used to pick points within the specimen at which the field was calculated to first order by adding together contributions from all the spheres. The linewidth calculated for the spherical-shell model agrees well with the results of our experimental measurements. Furthermore, the hexagonal model accurately predicts the observed linewidth in rat lung. These models can be used in correlating the NMR linewidth with the state of inflation or injury of the lung. They also may have application in a broad class of heterogeneous systems (e.g., slurries, bone).

Treatment algorithms and protocolized care.

Purpose of reviewExcess information in complex ICU environments exceeds human decision-making limits and likely contributes to unnecessary variation in clinical care, increasing the likelihood of clinical errors. I reviewed recent critical care clinical trials searching for information about the impact of protocol use on clinically pertinent outcomes. Recent findingsSeveral recently published clinical trials illustrate the importance of distinguishing efficacy and effectiveness trials. One of these trials illustrates the danger of conducting effectiveness trials before the efficacy of an intervention is established. The trials also illustrate the importance of distinguishing guidelines and inadequately explicit protocols from adequately explicit protocols. Only adequately explicit protocols contain enough detail to lead different clinicians to the same decision when faced with the same clinical scenario. SummaryDifferences between guidelines and protocols are important. Guidelines lack detail and provide general guidance that requires clinicians to fill in many gaps. Computerized or paper-based protocols are detailed and, when used for complex clinical ICU problems, can generate patient-specific, evidence-based therapy instructions that can be carried out by different clinicians with almost no interclinician variability. Individualization of patient therapy can be preserved by these protocols when they are driven by individual patient data. Explicit decision-support tools (eg, guidelines and protocols) have favorable effects on clinician and patient outcomes and can reduce the variation in clinical practice. Guidelines and protocols that aid ICU decision makers should be more widely distributed.

Progressive pulmonary insufficiency and other pulmonary complications of thermal injury

Progressive pulmonary insufficiency appears to be a universal response to the lung to a variety of injuries which damage the pulmonary-capillary emdothelium. Persistent hyperventilation, unresponsive to the administration of oxygen, is the earliest clinical sign of this complication of trauma and should prompt close monitoring of pulmonary function (measurement of arterial blood gas and pH levels, Vd/Vt A-aDo2, minute ventilation, vital capacity and inspiratory force) to assess the severity of the disease, the need for mechanical ventilatory support and the effectiveness of treatment. Other pulmonary complications of burn injury range from carbon monoxide poisoning and narcotics overdosage in the immediate postburn period through marked hyperventilation directly related to burn size occurring in the absence of significant parenchymal change to later occurring hematogenous and airborne pneumonia. Inhalation injury, a chemical tracheobronchitis which significantly increases the mortality of a given-sized burn, may be present immediately postburn but clinically inapparent for 48-72 hours. 133Xenon lung scans permit early diagnosis of this pulmonary injury and the timely institution of a graduated therapeutic response keyed to the severity of pulmonary disability. Knowledge of the pathogenesis of each of these complications is requisite for the physician caring for burn patients and permits the employment of rational preventive and therapeutic measures.

A replicable method for blood glucose control in critically Ill patients.

Context:To ensure interpretability and replicability of clinical experiments, methods must be adequately explicit and should elicit the same decision from different clinicians who comply with the study protocol. Objective:The objective of this study was to determine whether clinician compliance with protocol recommendations exceeds 90%. Design:We developed an adequately explicit computerized protocol (eProtocol-insulin) for managing critically ill adult patient blood glucose. We monitored clinician compliance with eProtocol-insulin recommendations in four intensive care units in four hospitals and compared blood glucose distributions with those of a simple clinical guideline at one hospital and a paper-based protocol at another. All protocols and the guideline used intravenous insulin and 80 to 110 mg/dL (4.4–6.1 mmol/L) blood glucose targets. Setting:The setting for this study was four academic hospital intensive care units. Patients:This study included critically ill adults requiring intravenous insulin. Intervention:Intervention used in this study was a bedside computerized protocol for managing blood glucose. Main Outcome Measure:The main outcome measure was clinician compliance with eProtocol-insulin recommendations. Results:The number of patients was 31 to 458 and the number of blood glucose measurements was 2,226 to 19,925 among the four intensive care units. Clinician compliance with eProtocol-insulin recommendations was 91% to 98%. Blood glucose distributions were similar in the four hospitals (generalized linear model p = .18). Compared with the simple guideline, eProtocol-insulin glucose measurements within target increased from 21% to 39%, and mean blood glucose decreased from 142 to 115 mg/dL (generalized linear model p < .001). Compared with the paper-based protocol, eProtocol-insulin glucose measurements within target increased from 28% to 42%, and mean blood glucose decreased from 134 to 116 mg/dL (generalized linear model p = .001). Conclusions:The 91% to 98% clinician compliance indicates eProtocol-insulin is an exportable instrument that can establish a replicable experimental method for clinical trials of blood glucose management in critically ill adults. Control of blood glucose was better with eProtocol-insulin than with a simple clinical guideline or a paper-based protocol.

Decision support and safety of clinical environments

Safety in the clinical environment is based on structures that reduce the probability of harm, on evidence that enhances the likelihood of actions that increase favourable outcomes, and on explicit directions that lead to decisions to implement the actions dictated by this evidence. A clinical decision error rate of only 1% threatens patient safety at a distressing frequency. Explicit computerised decision support tools standardise clinical decision making and lead different clinicians to the same set of diagnostic or therapeutic instructions. They have favourable impacts on patient outcome. Simple computerised algorithms that generate reminders, alerts, or other information, and protocols that incorporate more complex rules reduce the clinical decision error rate. Decision support tools are not new; it is the new attributes of explicit computerised decision support tools that deserve identification. When explicit computerised protocols are driven by patient data, the protocol output (instructions) is patient specific, thus preserving individualised treatment while standardising clinical decisions. The expected decrease in variation and increase in compliance with evidence-based recommendations should decrease the error rate and enhance patient safety.

A Strategy for Development of Computerized Critical Care Decision Support Systems

It is not enough to merely manage medical information. It is difficult to justify the cost of hospital information systems (HIS) or intensive care unit (ICU) patient data management systems (PDMS) on this basis alone. The real benefit of an integrated HIS or PDMS is in decision support. Although there are a variety of HIS and ICU PDMS systems available there are few that provide ICU decision support. The HELP system at the LDS Hospital is an example of a HIS which provides decision support on many different levels. In the ICU there are decision support tools for antibiotic therapy, nutritional management, and management of mechanical ventilation. Computer protocols for the management of mechanical ventilation (respiratory evaluation, ventilation, oxygenation, weaning and extubation) in patients with adult respiratory distress syndrome ((ARDS) have already been developed and clinically validated at the LDS Hospital. These protocols utilize the bedside intensive care unit (ICU) computer terminal to prompt the clinical care team with therapeutic and diagnostic suggestions. The protocols (in paper flow diagram and computerized form) have been used for over 40,000 hours in more than 125 adult respiratory distress syndrome (ARDS) patients. The protocols controlled care for 94% of the time. The remainder of the time patient care was not protocol controlled was a result of the patient being in states not covered by current protocollogic (e.g. hemodynamic instability, or transport for X-Ray studies). 52 of these ARDS patients met extra corporal membrane oxygenation (ECMO) criteria. The survival of the ECMO criteria ARDS patients was 41%, four times that expected (9%) from historical data (p<0.0002). The success of these computer protocols and their acceptance by the clinical staff clearly establishes the feasibility of controlling the therapy of severely ill patients.Over the last four years we have refined the process which we use for generating computerized protocols. The purpose of this paper is to present the six step development strategy which we are successfully using to produce computerized critical care protocols.

Implementation of a computerized patient advice system using the HELP clinical information system

A COMputerized Patient Advice System (COMPAS) was designed to test the feasibility of using the HELP clinical information system to direct the respiratory therapy of intensive care (ICU) patients acutely ill with adult respiratory distress syndrome. A modified black-board control architecture allowed the application of knowledge in either a forward or a backward chaining mode. Expert clinicians recommended decision logic and actions for five different modes of ventilatory support. The clinical staff used COMPAS to manage the ICU ventilatory support of five patients for a total of 624 hr. During that time there were 407 decision-making opportunities. COMPAS automatically generated therapy suggestions 379 (93.1%) times and the clinical staff accepted COMPASs recommendation in 320 (84.4%) of these cases. These results suggest that the ventilatory support of severely ill ICU patients can be managed by a clinical information system using a blackboard control architecture.