Interobserver variation in interpreting chest radiographs for the diagnosis of acute respiratory distress syndrome

Limitations of clinical trials in acute lung injury and acute respiratory distress syndrome

PURPOSE OF REVIEW

To review the challenges and limitations of randomized clinical trials in acute respiratory distress syndrome, with special emphasis on those pertaining to ventilatory management.

RECENT FINDINGS

Superbly executed randomized trials of ventilatory strategy have garnered deserved attention from the critical care community and yet have illustrated the limitations of our current approach to clinical research in this area. Inexact definitions, incomplete mechanistic understanding of complex pathophysiology, inappropriate outcome variables, diverse therapeutic environments, lengthy data acquisition time and ethical constraints on trial design limit the applicability of randomized control trial methodology to acute respiratory distress syndrome and acute lung injury. As yet, clinical practice does not seem to have been greatly impacted by the implications of completed randomized controlled trials per se. Recent issues, both ethical and interpretive, regarding control group participants have raised troubling and theoretically important issues that are yet to be fully resolved.

SUMMARY

Without tighter definitions of the condition under treatment, more specific targets for interventions to act upon, stratification that recognizes key interactive elements, and cointerventions based on better mechanistic understanding, randomized controlled trials of new drugs, ventilatory strategy, and other management approaches in acute respiratory distress syndrome are likely to remain a blunt instrument for investigation. As valuable as they are for calling important therapeutic principles to attention and for helping to suggest general guidelines for care, the limitations of randomized controlled trials for treating the individual with acute respiratory distress syndrome must be acknowledged.

Radiographic measures of intravascular volume status: the role of vascular pedicle width

PURPOSE OF REVIEW

A valid, low-cost, high-yield instrument to assess intravascular volume status in critically ill patients does not exist. The portable chest X-ray is a common part of any intensivist's or chest clinician's daily rounds.

RECENT FINDINGS

A simple, objective, valid measure of intravascular volume status, the vascular pedicle width, remains underappreciated in the medical literature. While more invasive, more expensive, and less common technologies are looked upon to assist in the clinical evaluation of volume status among critically ill patients, the vascular pedicle width stands alone in its low-cost, nearly risk-free potential to impact clinical practice. Even as the daily chest X-ray has become less common in practice, the role of measuring vascular pedicle width is potentially significant, particularly among mechanically ventilated patients. A standardized approach to reading the portable chest X-ray (supine or erect) is needed to facilitate interpretation of complex medical problems among the critically ill. Prospective evaluation of its appropriate use, particularly as compared with other, typically more invasive measures of intravascular volume, is warranted.

SUMMARY

Vascular pedicle width measurement using a standardized approach to daily chest X-ray interpretation represents untapped potential for improving the non-invasive assessment of volume status in critically ill patients.

The kappa statistic was representative of empirically observed inter-rater agreement for physical findings

BACKGROUND AND OBJECTIVE

To determine empirically chance agreement between different clinicians evaluating physical examination findings in children with acute abdominal pain.

MATERIALS AND METHODS

Cross-sectional study of children age 3 to 18 years treated in a pediatric emergency department for acute abdominal pain. Three different examiners were provided the same historic information and asked to predict, independently and prior to examining the patient, the presence or absence of seven different clinical findings. Agreement between pairs of observers on these predicted findings was determined, and was defined as observed chance agreement. Actual examination findings were also recorded, and expected agreement due to chance was determined from the kappa statistic calculation.

RESULTS

There were 68 pair of observations between two pediatric examiners, and 46 pair between pediatric and surgical examiners. Observed and expected chance agreement were very similar for six of the seven clinical findings. Agreement beyond chance for the actual exam findings was generally poor, with kappa less than 0.5 for all but one finding.

CONCLUSIONS

Expected chance agreement, as calculated from the kappa statistic, is a reasonable reflection of empirically observed chance agreement between clinicians.

Reliability of electrocardiogram interpretation in critically ill patients

OBJECTIVE

To assess the intrarater and interrater reliability of electrocardiogram (ECG) interpretation in critically ill patients and to assess the effect of knowledge of cardiac troponin values on these reliability estimates.

DESIGN

Prospective cohort study.

SETTING

Fifteen-bed medical-surgical intensive care unit.

PATIENTS

Consecutive adults admitted over a 2-month period.

MEASUREMENTS AND RESULTS

All consecutive 12-lead ECGs were interpreted independently by two raters for the presence of myocardial ischemia or infarction and secondarily for specific ischemic ECG abnormalities. The ECGs were first interpreted blinded to the patient's troponin levels and reinterpreted on two separate occasions, blinded and unblinded to the troponin values. Results are reported using chance-independent agreement (phi) with associated 95% confidence intervals. For the presence of ischemia or infarction, the intrarater reliability ranged from fair to moderate (phi = 0.35 [95% confidence interval = 0.16, 0.52] and 0.59 [0.33, 0.77] for the two raters, respectively); interrater reliability was slight when blinded to troponin levels (phi = 0.18 [0.03, 0.32]) and increased to moderate when the raters were unblinded to troponin values (phi = 0.52 [0.33, 0.66], p value for the difference = .004). For specific ECG changes, the intrarater and interrater reliability were low for T-wave flattening, whereas detection of a left bundle branch block showed high reliability.

CONCLUSIONS

ECG interpretation in critically ill patients for the presence of myocardial ischemia or infarction showed moderate reliability at best; however, there was high reliability for specific ECG changes. Knowledge of the patient's troponin values increased the reliability for all studied ECG changes and resulted in a statistically significant increase in the interrater reliability for diagnosing myocardial ischemia or infarction. Additional studies assessing the appropriate methods of diagnosing myocardial ischemia and infarction and assessing the reliability of these diagnostic tests in critically ill patients are required.

Incidence of acute respiratory distress syndrome and its relation to age

PURPOSE

The incidence of acute respiratory distress syndrome (ARDS) was previously considered to be relatively low, at less than 10 cases per 100,000 inhabitants per year, but recent reports suggest a higher incidence, especially in elderly patients. The objective was to determine the incidence and mortality of ARDS in our setting, both overall and by age group.

MATERIALS AND METHODS

We conducted a prospective, observational study of patients older than 14 years, admitted to the intensive care units of all hospitals in a province of southern Spain (Granada) during a 5-month period in 2001. American-European Consensus Conference criteria for ARDS were used. Patients were divided into 5 age groups, and the hospital mortality was recorded.

RESULTS

During the study period, 61 Granada-residing patients developed ARDS criteria. This represents an overall incidence of 23 cases per 100,000 inhabitants per year in the province. The incidence of ARDS in the age groups of 15 to 29, 30 to 44, 45 to 59, 60 to 74, and older than 74 years was 4.6, 13.6, 21.6, 51, and 73.9 cases per 100,000 inhabitants per year, respectively. The overall hospital mortality rate was 66%.

CONCLUSIONS

The incidence of ARDS is higher than reported a decade ago and is especially elevated in the elderly. The mortality remains high.

Acute respiratory distress syndrome: underrecognition by clinicians and diagnostic accuracy of three clinical definitions

OBJECTIVE

To determine and compare the diagnostic accuracy of three clinical definitions of acute respiratory distress syndrome (ARDS): (1) the American-European consensus conference definition; (2) the lung injury score; and (3) a recently developed Delphi definition. A second objective was to determine the accuracy of clinical diagnoses of ARDS made in daily practice.

DESIGN

Independent comparison of autopsy findings with the daily status of clinical definitions, constructed with data abstracted retrospectively from medical records.

SETTING

Tertiary intensive care unit.

PATIENTS

One hundred thirty-eight patients from the period 1995 through 2001 who were autopsied after being mechanically ventilated.

INTERVENTIONS

Clinical ARDS diagnoses were determined daily without knowledge of autopsy results. Charts were reviewed for any mention of ARDS in the clinical notes. Autopsies were reviewed independently by two pathologists for the presence of diffuse alveolar damage. The sensitivity and specificity of the definitions were determined with use of diffuse alveolar damage at autopsy as the reference standard.

MEASUREMENTS AND MAIN RESULTS

Diffuse alveolar damage at autopsy was documented in 42 of 138 cases (30.4%). Only 20 of these 42 patients (47.6%) had any mention of ARDS in their chart. Sensitivities and specificities (95% confidence intervals) were as follows: American-European definition, 0.83 (0.72-0.95), 0.51 (0.41-0.61); lung injury score, 0.74 (0.61-0.87), 0.77 (0.69-0.86); and Delphi definition, 0.69 (0.55-0.83), 0.82 (0.75-0.90). Specificity was significantly higher for both the lung injury score and Delphi definition than for the American-European definition (p < .001 for both), whereas comparisons of sensitivity, which was higher for the American-European definition, were not significantly different (p = .34 and p = .07, respectively).

CONCLUSIONS

Acute respiratory distress syndrome appears underrecognized by clinicians in patients who die with this syndrome. In this population, the specificities of existing clinical definitions vary considerably, which may be problematic for clinical trials.

Development of a clinical definition for acute respiratory distress syndrome using the Delphi technique

PURPOSE

The objective of this study is to describe the implementation of formal consensus techniques in the development of a clinical definition for acute respiratory distress syndrome.

MATERIALS AND METHODS

A Delphi consensus process was conducted using e-mail. Sixteen panelists who were both researchers and opinion leaders were systematically recruited. The Delphi technique was performed over 4 rounds on the background of an explicit definition framework. Item generation was performed in round 1, item reduction in rounds 2 and 3, and definition evaluation in round 4. Explicit consensus thresholds were used throughout.

RESULTS

Of the 16 panelists, 11 actually participated in developing a definition that met a priori consensus rules on the third iteration. New incorporations in the Delphi definition include the use of a standardized oxygenation assessment and the documentation of either a predisposing factor or decreased thoracic compliance. The panelists rated the Delphi definition as acceptable to highly acceptable (median score, 6; range, 5-7 on a 7-point Likert scale).

CONCLUSIONS

We conclude that it is feasible to consider using formal consensus in the development of future definitions of acute respiratory distress syndrome. Testing of sensibility, reliability, and validity are needed for this preliminary definition; these test results should be incorporated into future iterations of this definition.

Should parents accompany critically ill children during inter-hospital transport?

BACKGROUND

Parental accompaniment during inter-hospital transportation (retrieval) of critically ill children is not commonplace in the United Kingdom.

METHODS

A three month pilot of parental accompaniment was undertaken in 2002 (143 retrievals), after which time the policy was adopted as standard practice. A follow up audit was performed in 2004 (136 retrievals).

RESULTS

Findings were remarkably consistent between the two periods. Staff perceived little or no added stress during the majority of transfers (96% in 2002, 98% in 2004), and felt able to perform medical interventions without hindrance (98% in 2002, 100% in 2004). There was good agreement between medical and nursing staff regarding perception of stress and ability to perform interventions (phi statistic 0.57 to 1.00). Adverse events occurred during 11 (3.9%) retrievals; six of these involved a parent exclusively. Stress tended to be associated with adverse events or parental behaviour rather than disease acuity. Staff vetoed the offer of accompaniment on 11 occasions, for a variety of reasons. The majority of parents found the experience safe, beneficial, and perceived a reduction in stress as a result. These data may inform other retrieval services who are considering adopting a similar policy.

Can we abandon daily routine chest radiography in intensive care patients?

Two different schools of thought exist on the utility of daily routine chest radiographs in intensive care unit (ICU) patients: some ICU physicians argue that daily routine chest radiographs are indicated in all patients who have cardiopulmonary problems or are receiving artificial ventilation. Others state that chest radiographs should be made on indication only, for example, following a change in clinical status or change of supportive devices. Most studies on this topic have simply reported the existence of several findings on chest radiographs; some investigators tried to determine whether such findings were new and/or unexpected and whether they caused a therapy change. A restrictive strategy has been compared with a daily routine strategy in only 2 clinical trials: 1 study conducted in a pediatric ICU (pediatric ICUs usually have low mortality rates), and the other a rather small (and probably underpowered) study. The debate about discontinuing daily routine chest radiographs in the ICU is still not settled.

Inter-examiner reliability of passive assessment of intervertebral motion in the cervical and lumbar spine: A systematic review

A systematic review was conducted to determine inter-examiner reliability of passive assessment of segmental intervertebral motion in the cervical and lumbar spine as well as to explore sources of heterogeneity. Passive assessment of motion is used to decide on treatments for neck and low-back pain patients. Inter-examiner reliability has been a matter of debate, resulting in questions about professional credibility and accountability. A structured search for relevant studies in MEDLINE and CINAHL was followed by extensive reference tracing and hand searching. Studies presenting estimates of reliability for individual motion segments were included. No language restrictions were imposed. Study quality was assessed using criteria derived from the Standards for Reporting of Diagnostic Accuracy (STARD) statement and a quality assessment tool for studies of diagnostic accuracy included in systematic reviews (QUADAS). Study selection, quality assessment, and data extraction were performed by two reviewers independently. Qualitative analyses and additional subgroup analyses were conducted. Nineteen studies were included. Two studies satisfied criteria for external and internal validity, of which one found fair to moderate reliability. Assessment of motion segments C1-C2 and C2-C3 almost consistently reached at least fair reliability. Overall, inter-examiner reliability was poor to fair. However, most studies were found to be of poor methodological quality. We propose explicit recommendations for the conduct and reporting of future research.

Epidemiology of acute lung injury

PURPOSE OF REVIEW

Acute lung injury and its extreme manifestation, acute respiratory distress syndrome, complicate a wide variety of serious medical and surgical conditions, only some of which affect the lung directly. Despite recent evidence-based advances in clinical management, acute lung injury and acute respiratory distress syndrome are associated with significant mortality. Detailed epidemiology is essential in guiding the recruitment of patients into trials of new therapeutic interventions, thereby improving outcome and allowing directed allocation of scarce resources.

RECENT FINDINGS

The incidence of acute lung injury in the United States overall (17-64 per 100,000 person-years) seems to be higher than in Europe, Australia, and other developed countries (17-34 per 100, 000 person-years). The mortality rates for patients with acute respiratory distress syndrome range from 34 to 58%. The hypothesis that pulmonary and extrapulmonary acute respiratory distress syndromes are different disease entities continues to gain momentum. A genetic predisposition to acute respiratory distress syndrome may contribute to its pathogenesis and outcome.

SUMMARY

Recent epidemiologic studies of the incidence of acute lung injury and acute respiratory distress syndrome have indicated a similar incidence in developed societies, and they confirm that mortality is falling in comparison with a decade ago. The awaited publication of new consensus guidelines for the definition of acute lung injury and acute respiratory distress syndrome may render new studies necessary.

Clinical predictors of and mortality in acute respiratory distress syndrome: Potential role of red cell transfusion*

OBJECTIVE

Clinical predictors for acute respiratory distress syndrome (ARDS) have been studied in few prospective studies. Although transfusions are common in the intensive care unit, the role of submassive transfusion in non-trauma-related ARDS has not been studied. We describe here the clinical predictors of ARDS risk and mortality including the role of red cell transfusion.

DESIGN

Observational prospective cohort.

SETTING

Intensive care unit of Massachusetts General Hospital.

PATIENTS

We studied 688 patients with sepsis, trauma, aspiration, and hypertransfusion.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Two hundred twenty-one (32%) subjects developed ARDS with a 60-day mortality rate of 46%. Significant predictors for ARDS on multivariate analyses included trauma (adjusted odds ratio [ORadj] 0.22, 95% confidence interval [CI] 0.09-0.53), diabetes (ORadj 0.58, 95% CI 0.36-0.92), direct pulmonary injury (ORadj 3.78, 95% CI 2.45-5.81), hematologic failure (ORadj 1.84, 95% CI 1.05-3.21), transfer from another hospital (ORadj 2.08, 95% CI 1.33-3.25), respiratory rate >33 breaths/min (ORadj 2.39, 95% CI 1.51-3.78), hematocrit >37.5% (ORadj 1.77, 95% CI 1.14-2.77), arterial pH <7.33 (ORadj 2.00, 95% CI 1.31-3.05), and albumin </=2.3 g/dL (ORadj 1.80, 95% CI 1.18-2.73). Packed red blood cell transfusion was associated with ARDS (ORadj 1.52, 95% CI 1.00-2.31, p = .05). Significant predictors for mortality in ARDS included age (ORadj 1.96, 95% CI 1.50-2.53), Acute Physiology and Chronic Health Evaluation III score (ORadj 1.78, 95% CI 1.16-2.73), trauma (ORadj 0.075, 95% CI 0.006-0.96), corticosteroids before ARDS (ORadj 4.65, 95% CI 1.47-14.7), and arterial pH <7.22 (ORadj 2.32, 95% CI 1.02-5.25). Packed red blood cell transfusions were associated with increased mortality in ARDS (ORadj 1.10 per unit transfused; 95% CI 1.04-1.17) with a significant dose-dependent response (p = .02).

CONCLUSIONS

Important predictors for the development of and mortality in ARDS were identified. Packed red blood cell transfusion was associated with an increased development of and increased mortality in ARDS.

A comparison of client and mental health worker assessment of needs and unmet needs

This study was set up to examine agreement on needs identified by mental health clients and their primary mental health workers. Mental health workers assessed a convenience sample of clients who completed an interview about the services they receive. Data were collected from 78 client and staff dyads regarding 11 need domains. Mental health workers and clients did not agree on the number of needs (ICC = 0.42). Kappa coefficients indicated significant agreement between staff and clients for only 1 of the 11 need domains (vocational need kappa = 0.67; others ranged from 0 to 0.58). The data further revealed that mental health workers and clients disagreed about unmet needs (kappa ranged from -0.07 to 0.46). These findings show that clients and staff have divergent opinions regarding needs. Integrating clients' perspectives into treatment plans may help address this issue.

Proceedings of a Consensus Conference: Towards an Understanding of TRALI

Transfusion-related acute lung injury is a relatively uncommon transfusion-associated adverse effect occurring during or soon after an allogeneic blood transfusion. Transfusion-related acute lung injury is a complex syndrome that has many manifestations and has only recently been identified to be an important cause of transfusion-associated morbidity and mortality. But despite its increasing recognition, much about the pathogenesis, treatment, and prevention is poorly understood and often controversial. The purpose of this consensus conference was to bring together international experts in an effort to try to standardize a case definition, which could be used to enhance future understanding of transfusion-related acute lung injury including its epidemiology, pathogenesis, management, prevention, and research. These proceedings are being provided with a view to making available to the transfusion medicine community the considerable amount of important information presented at this consensus conference by the invited international panel of experts.

Inter-observer agreement in audit of quality of radiology requests and reports

AIMS

To assess the quality of the imaging procedure requests and radiologists' reports using an auditing tool, and to assess the agreement between different observers of the quality parameters.

MATERIALS AND METHODS

In an audit using a standardized scoring system, three observers reviewed request forms for 296 consecutive radiological examinations, and two observers reviewed a random sample of 150 of the corresponding radiologists' reports. We present descriptive statistics from the audit and pairwise inter-observer agreement, using the proportion agreement and kappa statistics.

RESULTS

The proportion of acceptable item scores (0 or +1) was above 70% for all items except the requesting physician's bleep or extension number, legibility of the physician's name, or details about previous investigations. For pairs of observers, the inter-observer agreement was generally high, however, the corresponding kappa values were consistently low with only 14 of 90 ratings >0.60 and 6 >0.80 on the requests/reports. For the quality of the clinical information, the appropriateness of the request, and the requested priority/timing of the investigation items, the mean percentage agreement ranged 67-76, and the corresponding kappa values ranged 0.08-0.24.

CONCLUSION

The inter-observer reliability of scores on the different items showed a high degree of agreement, although the kappa values were low, which is a well-known paradox. Current routines for requesting radiology examinations appeared satisfactory, although several problem areas were identified.

Ventilation of patients with acute lung injury and acute respiratory distress syndrome: has new evidence changed clinical practice?

OBJECTIVES

A recent randomized trial of mechanical ventilation in acute lung injury (ALI)/adult respiratory distress syndrome (ARDS) demonstrated a 22% relative reduction in mortality rate using 6 mL/kg predicted body weight tidal volume vs. 12 mL/kg predicted body weight tidal volume. We determined whether publication of these findings changed clinical practice.

DESIGN

Retrospective cohort, 12 months before (Pre) and 12 months after publication (Post) of a randomized trial supporting the use of a 6 mL/kg predicted body weight tidal volume strategy.

SETTING

Three tertiary care hospitals in northern New England.

PATIENTS

From a sample of 943 patients receiving prolonged mechanical ventilation between 1998 and 1999 (Pre) and between 2000 and 2001 (Post), 300 patients meeting the American-European Consensus Conference definition of ALI or ARDS were selected for analysis.

INTERVENTIONS

The tidal volume, tidal volume/kg predicted body weight, and proportion receiving tidal volume/kg > or =6 mL/kg and < or =12 mL/kg predicted body weight were recorded at noon the first day after the diagnosis of ALI or ARDS was established.

MEASUREMENTS AND MAIN RESULTS

Pre and Post mean tidal volume (+/- sd) size and tidal volume size/kg predicted body weight were 759 +/- 158 mL (median 750 mL) vs. 639 +/- 138 mL (median 600 mL, p <.001) and 12.3 +/- 2.7 mL/kg (median 11.7 mL/kg) vs. 10.6 +/- 2.4 mL/kg (median 10.7 mL/kg, p <.001) respectively. Pre and Post plateau pressures and peak airway pressures were similar.

CONCLUSION

Publication of a trial demonstrating large mortality reductions using small tidal volume was associated with significant reductions in tidal volume delivered to patients with ALI/ARDS. However, wide variation in practice persists, and the proportion of patients receiving tidal volumes within recommended limits (< or =8 mL/kg) remains modest.

Risk Factors for Acute Lung Injury After Thoracic Surgery for Lung Cancer

Acute lung injury (ALI) may complicate thoracic surgery and is a major contributor to postoperative mortality. We analyzed risk factors for ALI in a cohort of 879 consecutive patients who underwent pulmonary resections for non-small cell lung carcinoma. Clinical, anesthetic, surgical, radiological, biochemical, and histopathologic data were prospectively collected. The total incidence of ALI was 4.2% (n = 37). In 10 cases, intercurrent complications (bronchopneumonia, n = 5; bronchopulmonary fistula, n = 2; gastric aspiration, n = 2; thromboembolism, n = 1) triggered the onset of ALI 3 to 12 days after surgery, and this was associated with a 60% mortality rate (secondary ALI). In the remaining 27 patients, no clinical adverse event preceded the development of ALI-0 to 3 days after surgery-that was associated with a 26% mortality rate (primary ALI). Four independent risk factors for primary ALI were identified: high intraoperative ventilatory pressure index (odds ratio, 3.5; 95% confidence interval, 1.7-8.4), excessive fluid infusion (odds ratio, 2.9; 95% confidence interval, 1.9-7.4), pneumonectomy (odds ratio, 2.8; 95% confidence interval, 1.4-6.3), and preoperative alcohol abuse (odds ratio, 1.9; 95% confidence interval, 1.1-4.6). In conclusion, we describe two clinical forms of post-thoracotomy ALI: 1). delayed-onset ALI triggered by intercurrent complications and 2). an early form of ALI amenable to risk-reducing strategies, including preoperative alcohol abstinence, lung-protective ventilatory modes, and limited fluid intake.

IMPLICATIONS

In an observational study including all patients undergoing lung surgery, we describe two clinical forms of acute lung injury (ALI): a delayed-onset form triggered by intercurrent complications and an early form associated with preoperative alcohol consumption, pneumonectomy, high intraoperative pressure index, and excessive fluid intake over the first 24 h.

Impact of positive end-expiratory pressure on the definition of acute respiratory distress syndrome

OBJECTIVE

We examined whether PEEP during the first hours of ARDS can induce such a change in oxygenation that could mask fulfillment of the AECC criteria of a PaO(2)/FIO(2) </= 200 essential for ARDS diagnosis.

DESIGN AND SETTING

Observational, prospective cohort in two medical-surgical ICU in teaching hospitals.

PATIENTS

48 consecutive patients who met AECC criteria of ARDS on 0 PEEP (ZEEP) at the moment of diagnosis.

MEASUREMENTS AND RESULTS

PaO(2)/FIO(2) and lung mechanics were recorded on admission (0 h) to the ICU on ZEEP, and after 6, 12, and 24 h on PEEP levels selected by attending physicians. Lung Injury Score (LIS) was calculated at 0 and 24 h. PaO(2)/FIO(2) rose significantly from 121+/-45 on ZEEP at 0 h, to 234+/-85 on PEEP of 12.8+/-3.7 cmH(2)O after 24 h. LIS did not change significantly (2.34+/-0.53 vs. 2.42+/-0.62). These variables behaved similarly in pulmonary and extrapulmonary ARDS, and in survivors and nonsurvivors. After 24 h only 18 patients (38%) still had a PaO(2)/FIO(2) of 200 or lower. Their mortality was similar to that in the remaining patients (61% vs. 53%).

CONCLUSIONS

The use of PEEP improved oxygenation such that one-half of patients after 6 h, and most after 24 h did not fulfill AECC hypoxemia criteria of ARDS. However, LIS remained stable in the overall series. These results suggest that PEEP level should be taken into consideration for ARDS diagnosis.

Reliability of three classification systems measuring active motion in brachial plexus birth palsy

BACKGROUND

Several classification systems for the categorization of function in patients with brachial plexus birth palsy have been proposed. The purpose of this investigation was to determine the intraobserver and interobserver reliability of the modified Mallet Classification, Toronto Test Score, and Hospital for Sick Children Active Movement Scale in the evaluation of these patients.

METHODS

Eighty children with brachial plexus birth palsy were evaluated by two trained examiners on two different occasions. Intraobserver and interobserver reliability was determined with use of the kappa statistic.

RESULTS

On the basis of the kappa statistic, intraobserver reliability was good to excellent for individual elements of the modified Mallet Classification, Toronto Test Score, and Active Movement Scale in all age-groups. Interobserver reliability for individual elements of these three systems ranged from fair to excellent. When aggregate Toronto Test and modified Mallet scores were assessed, positive intraobserver and interobserver correlations were noted (Pearson r = 0.70 to 0.98, p < 0.001). Internal consistency (test-retest reliability) as determined by the Cronbach alpha for the aggregate Toronto Test and modified Mallet scores was excellent for each age-group (alpha > 0.90, p < 0.001).

CONCLUSIONS

The modified Mallet Classification, Toronto Test Score, and Active Movement Scale are reliable instruments for assessing upper-extremity function in patients with brachial plexus birth palsy. The natural history and surgical outcomes of these patients can now be conducted with use of these reliable outcomes instruments.

Lung injury severity scoring in the era of lung protective mechanical ventilation: the PaO2/FIO2 ratio

BACKGROUND

Lung protective ventilatory strategies using low tidal volume and high positive end-expiratory pressure (PEEP) have become standard practice. Such strategies, however, may invalidate measurement of lung injury severity by traditional methods that are based on plain chest radiograph findings, oxygenation, minute ventilation, lung compliance, and PEEP level, such as the Murray lung injury score (LIS). Many of these criteria are potentially therapy dependent and may change with different ventilatory strategies. The purpose of this study was to determine whether measurement of lung injury severity based simply on oxygenation criteria (PaO(2)/FIO(2)) was as accurate as the Murray LIS currently used in multiple organ failure (MOF) scoring.

METHODS

Since 1992, trauma patients at high risk for developing MOF have been prospectively identified and MOF scores calculated daily. Pulmonary dysfunction is graded from 0 to 3 on the basis of a modified Murray LIS incorporating the aforementioned parameters. Lung injury severity was redefined using the PaO(2)/FIO(2) (P/F score): Grade 0 = >250; 1 = 175 to 250; 2 = 100 to 174; and 3 = <100. The maximum (worst) score using each was compared using logistic regression and receiver operating characteristic curve analysis.

RESULTS

Five hundred thirty-nine trauma patients had lung injury severity assessed using both LIS and P/F score. The mean P/F score was over twice the mean LIS (1.9 +/-.04 vs. 0.9+/-.04, p < 0.0001). In 28% of patients, the LIS and P/F score were identical, whereas in 71%, the P/F score was greater than the LIS. Both scores were significant predictors of mortality; however, receiver operating characteristic curve analysis showed that the P/F score was superior in predicting mortality (area under the curve, 0.74+/-.03 vs. 0.67+/-.04).

CONCLUSION

The P/F score is a simple method of quantifying lung injury severity in trauma patients that better predicts mortality compared with the more complicated modified Murray lung injury score currently in use. The P/F score should replace more complex and potentially therapy-dependent scores.

Mechanical effects of airway humidification devices in difficult to wean patients

OBJECTIVE

To evaluate the influence of airway humidification devices on the efficacy of ventilation in difficult to wean patients.

DESIGN

A prospective, randomized, controlled physiologic study.

SETTING

A 22-bed medical intensive care unit in a university hospital.

PATIENTS

Chronic respiratory failure patients.

INTERVENTIONS

Performances of a heated humidifier and a heat and moisture exchanger were evaluated on diaphragmatic muscle activity, breathing pattern, gas exchange, and respiratory comfort during weaning from mechanical ventilation by using pressure support ventilation. Eleven patients with chronic respiratory failure were submitted to four pressure support ventilation sequences by using the heated humidifier and the heat and moisture exchanger at two different levels of pressure support ventilation (7 and 15 cm H(2)O).

MEASUREMENT AND MAIN RESULTS

Compared with the heated humidifier and regardless of the pressure support ventilation level used, the heat and moisture exchanger significantly increased all of the inspiratory effort variables (inspiratory work of breathing expressed in J/L and J/min, pressure time product, changes in esophageal pressure, and transdiaphragmatic pressure; p <.05) and dynamic intrinsic positive end-expiratory pressure (p <.05). Similarly, the heat and moisture exchanger produced a significant increase in Paco(2) (p <.01) responsible for severe respiratory acidosis (p <.05), which was insufficiently compensated for despite a significant increase in minute ventilation (p <.05). This resulted in respiratory discomfort for all patients with the heat and moisture exchanger (p <.01). Adverse effects were partially counterbalanced by increasing the pressure support ventilation level with the heat and moisture exchanger by >or=8 cm H(2)O.

CONCLUSIONS

The type of airway humidification device used may negatively influence the mechanical efficacy of ventilation and, unless the pressure support ventilation level is considerably increased, the use of a heat and moisture exchanger should not be recommended in difficult or potentially difficult to wean patients with chronic respiratory failure.

Epidemiology of acute lung injury

OBJECTIVE

To review the epidemiology of acute lung injury (ALI) with particular emphasis on its effect on public health.

DATA SOURCES

Published studies on the definitions, incidence, and outcomes of ALI.

DATA SUMMARY

ALI is a syndrome of acute hypoxemic respiratory failure that is not primarily cardiac in origin. The diagnostic criteria for the syndrome have not been well studied for their reliability or validity. The lack of a gold standard for the diagnosis of ALI is a challenge to clinical investigation. Recent data on the incidence of ALI (20-50 cases/105 person-years) indicate that it is more common than previous estimates for the incidence of acute respiratory distress syndrome (3-8 cases/105 person-years). There is conflicting evidence as to whether the mortality rate in the broader patient population with ALI is different from the mortality rate in acute respiratory distress syndrome. Mortality attributable to and associated with ALI in the United States is comparable to HIV infection, breast cancer, and asthma. Morbidity from impaired cognitive function, functional status, and psychiatric complications has been reported in survivors of ALI.

CONCLUSIONS

Recent studies of the epidemiology of ALI have reported higher incidence rates for this syndrome than previously described. The mortality and morbidity rates associated with ALI are considerable, with significant impact on public health.

Findings on the portable chest radiograph correlate with fluid balance in critically ill patients

STUDY OBJECTIVES

Fluid balance concerns occur daily in critically ill patients, complicated by difficulties assessing intravascular volume. Chest radiographs (CXRs) quantify pulmonary edema in acute lung injury (ALI) and total blood volume in normal subjects. We hypothesized that CXRs would reflect temporal changes in fluid balance in critically ill patients.

DESIGN

Standardized scoring of 133 supine, portable, anteroposterior CXRs. Outcomes included subjective and objective measures of intravascular volume and pulmonary edema.

SETTING

Academic university medical center and affiliated Veterans Affairs hospital.

PATIENTS

Thirty-seven patients with ALI receiving mechanical ventilation blindly randomized to treatment with diuretics and colloids or dual placebo for 5 days.

MEASUREMENTS AND RESULTS

Treated patients experienced a 3.3-L diuresis and 10-kg weight loss during the 5-day period. A significant correlation was observed in all patients between changes in vascular pedicle width (VPW) and net intake/output (r = 0.50, p = 0.01) or weight (r = 0.51, p = 0.01). The correlation between VPW and fluid balance was greatest for weight changes in the treatment group alone (r = 0.71, p = 0.005). Pulmonary artery occlusion pressure correlated highly with changes in VPW (r = 0.70, p < 0.001). After day 1, CXRs revealed significant between-group differences in VPW without changes in cardiothoracic ratio or subjective measures of edema. The proportion of patients with VPW < 70 mm did not differ at baseline but was significantly more in the treatment group on all subsequent days (p < 0.05).

CONCLUSIONS

We conclude that temporal fluid balance changes are reflected on commonly utilized portable CXRs. Objective radiographic measures of intravascular volume may be more appropriate indicators of fluid balance than subjective measures, with VPW appearing most sensitive. If systematically quantitated, serial CXRs provide a substantial supplement to other clinically available data for the purpose of fluid management in critically ill patients.

The pulmonary physician in critical care. 5: Acute lung injury and the acute respiratory distress syndrome: definitions and epidemiology

An understanding of the epidemiology of ALI/ARDS and the effects of treatment have been hampered by the lack of a uniform definition of the syndrome. Various definitions have been proposed, and these are reviewed with particular attention to how changes in definition have affected our understanding of the natural history and treatment options for the condition.

Pulmonary dead-space fraction as a risk factor for death in the acute respiratory distress syndrome

BACKGROUND

No single pulmonary-specific variable, including the severity of hypoxemia, has been found to predict the risk of death independently when measured early in the course of the acute respiratory distress syndrome. Because an increase in the pulmonary dead-space fraction has been described in observational studies of the syndrome, we systematically measured the dead-space fraction early in the course of the illness and evaluated its potential association with the risk of death.

METHODS

The dead-space fraction was prospectively measured in 179 intubated patients, a mean (+/-SD) of 10.9+/-7.4 hours after the acute respiratory distress syndrome had developed. Additional clinical and physiological variables were analyzed with the use of multiple logistic regression. The study outcome was mortality before hospital discharge.

RESULTS

The mean dead-space fraction was markedly elevated (0.58+/-0.09) early in the course of the acute respiratory distress syndrome and was higher among patients who died than among those who survived (0.63+/-0.10 vs. 0.54+/-0.09, P<0.001). The dead-space fraction was an independent risk factor for death: for every 0.05 increase, the odds of death increased by 45 percent (odds ratio, 1.45; 95 percent confidence interval, 1.15 to 1.83; P=0.002). The only other independent predictors of an increased risk of death were the Simplified Acute Physiology Score II, an indicator of the severity of illness (odds ratio, 1.06; 95 percent confidence interval, 1.03 to 1.08; P<0.001) and quasistatic respiratory compliance (odds ratio, 1.06; 95 percent confidence interval, 1.01 to 1.10; P=0.01).

CONCLUSIONS

Increased dead-space fraction is a feature of the early phase of the acute respiratory distress syndrome. Elevated values are associated with an increased risk of death.

Using the chest radiograph to determine intravascular volume status: the role of vascular pedicle width

Due to concerns about the efficacy and safety of using pulmonary artery catheterization to evaluate hemodynamic status, noninvasive diagnostic testing has gained increased importance. This article focuses on both the supportive evidence and the limitations of applying the vascular pedicle width (VPW), which is the mediastinal silhouette of the great vessels, as an aid in the assessment of patients' intravascular volume status. The objective measurement of the VPW obtained from either upright or supine chest radiographs (CXRs which are often already available though not fully utilized) can increase the accuracy of the clinical and radiographic assessment of intravascular volume status by 15 to 30%, and this value may be even higher when VPW is used serially within the same patient. Regardless of the presence or absence of pulmonary edema, the best VPW cutoff for differentiating a high vs normal to low intravascular volume status is 70 mm. Patients with a VPW of > 70 mm coupled with a cardiothoracic ratio of > 0.55 are more than three times more likely to have a pulmonary artery occlusion pressure > 18 mm Hg than are patients without these radiographic findings. We suggest a management algorithm for utilizing the VPW, and whether or not such an approach will offer superior patient outcomes requires prospective investigation. Reappraisal of the VPW and other roentgenographic signs should be incorporated into newly implemented studies of the Swan-Ganz catheter, ICU echocardiography, portable CT scans, and other costlier technologies. While such investigations may refine the optimum application of the portable CXR, conventional and digital supine radiographs should retain an important role in the diagnosis and management of critically ill patients. Lastly, the measurement of the VPW should be incorporated into the training of chest clinicians and radiologists.

Incidence and mortality of acute lung injury and the acute respiratory distress syndrome in three Australian States

To determine the incidence and 28-d mortality rate for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) using the 1994 American-European Consensus Conference definitions, we prospectively screened every admission to all 21 adult intensive care units in the States of South Australia, Western Australia, and Tasmania (total population older than 15 yr of age estimated as 2,941,137), between October 1 and November 30, 1999. A total of 1,977 admissions were screened of which 168 developed ALI and 148 developed ARDS, which represents a first incidence of 34 and 28 cases per 100,000 per annum, respectively. The respective 28-d mortality rates were 32% and 34%. The most common predisposing factors for ALI were nonpulmonary sepsis (31%) and pneumonia (28%). Although the incidences of ALI and ARDS are higher and the mortality rates are lower than those reported from studies in other countries, multicenter international studies are required to exclude methodological differences as the cause for this finding.

Radiologic determination of intravascular volume status using portable, digital chest radiography: a prospective investigation in 100 patients

OBJECTIVE

To answer the following questions: Can the digital chest roentgenogram (CXR) be used to differentiate patients' volume status? Do clinical data alter radiologists' accuracy in interpreting the digital CXR?

DESIGN

Prospective cohort study.

SETTING

Nine adult intensive care units of a tertiary care medical center.

PATIENTS

One hundred thirty-five consecutive patients with pulmonary artery catheters, of whom 35 were excluded because of unacceptable pulmonary artery occlusion pressure (PAOP) tracings.

METHODS

Each patient had a portable, anteroposterior, supine digital CXR. Clinicians evaluated volume status and then measured hemodynamic data within 1 hr of the CXR. Digital CXRs were independently interpreted on two separate occasions (with and without clinical information) by three experienced chest radiologists, and these interpretations were compared with hemodynamic data.

RESULTS

Of the 100 patients, 39 had PAOP >18 mm Hg, whereas 61 had PAOP <18 mm Hg. Radiologists' accuracy in differentiating volume status increased with incorporation of clinical data (56% without vs. 65% with clinical data, p =.009). Using objective receiver operating characteristic-derived cutoffs of 70 mm for vascular pedicle width and 0.55 for cardiothoracic ratio, radiologists' accuracy in differentiating PAOP >18 mm Hg from PAOP <18 mm Hg was 70%. The intrareader and the inter-reader correlation coefficients were very high. The likelihood ratio of the CXR in determining volume status using the objective vascular pedicle width and cardiothoracic ratio measures was 3.1 (95% confidence interval, 1.9-6.0), significantly higher than subjective CXR interpretations with and without clinical data (p <.001).

CONCLUSIONS

Differentiating intravascular volume status with portable, supine, digital CXRs may be improved by using objective cutoffs of vascular pedicle width >70 mm and cardiothoracic ratio >0.55 or by incorporating clinical data.

Agreement between alternative classifications of acute respiratory distress syndrome

To examine the agreement between two classifications of acute respiratory distress syndrome (ARDS) that are used interchangeably in clinical practice and clinical research, we classified 118 patients taking part in a randomized trial with respect to the presence of ARDS using the North American-European Consensus Committee (NAECC) and the Lung Injury Severity Score (LISS) criteria. The incidence of ARDS using NAECC criteria was 55.1% (95% confidence interval, 46.1% to 64.1%), and using the LISS criteria 61.9% (95% confidence interval, 53.1% to 70.6%). The p value on the difference between these proportions was 0.07. Raw agreement, chance-corrected agreement (kappa), and chance-independent agreement (phi) on the study occurrence of ARDS using the two classifications were, respectively, 0.73 (95% CI, 0.65 to 0.81), 0.46 (95% CI, 0.32 to 0.61), and 0.63 (95% CI, 0.41 to 0.79). No single component of either index contributed to disagreement to an appreciably greater extent than other components. Baseline characteristics and outcomes were similar among patients who developed ARDS according to either classification. We conclude that NAECC and LISS classifications resulted in similar estimates of the incidence of ARDS in this clinical trial, though patients were frequently classified as having ARDS with only one model. These discordant classifications had no prognostic importance.

Estimation of operating characteristics for dependent diagnostic tests based on latent Markov models

We describe a method for making inferences about the joint operating characteristics of multiple diagnostic tests applied longitudinally and in the absence of a definitive reference test. Log-linear models are adopted for the classification distributions conditional on the latent state, where inclusion of appropriate interaction terms accommodates conditional dependencies among the tests. A marginal likelihood is constructed by marginalizing over a latent two-state Markov process. Specific latent processes we consider include a first-order Markov model, a second-order Markov model, and a time-nonhomogeneous Markov model, although the method is described in full generality. Adaptations to handle missing data are described. Model diagnostics are considered based on the bootstrap distribution of conditional residuals. The methods are illustrated by application to a study of diffuse bilateral infiltrates among patients in intensive care wards in which the objective was to assess aspects of validity and clinical agreement.

Use of a screen log to audit patient recruitment into multiple randomized trials in the intensive care unit. Canadian Critical Care Trials Group

OBJECTIVE

To develop and evaluate a screen log for monitoring enrollment in multiple randomized clinical trials conducted in a single center.

SETTING

University-affiliated 20-bed tertiary care medical-surgical intensive care unit (ICU).

PATIENTS

Consecutive ICU patients admitted between April 1995 and March 1997.

METHODS

We developed a screen log for multicentered studies conducted in our ICU. Using a multiple-project, unicenter perspective, we evaluated the screen log as a tool for monitoring eligibility and enrollment of patients in four multicentered randomized trials focused on stress ulcer prophylaxis, blood transfusion thresholds, immunotherapy for sepsis and mechanical ventilation strategies.

RESULTS

The screen log was used as an instrument to monitor trial execution. We recorded all aspects of study enrollment and created a taxonomy of reasons for nonenrollment into each trial. We calculated enrollment efficiency rates and used these data to develop strategies to maximize accrual. The screen log became a communication tool that fostered research-oriented continuous quality improvement initiatives for the management of concurrently conducted randomized trials in our ICU.

CONCLUSIONS

Intensivists participating in several clinical trials may be interested in monitoring and maximizing enrollment when conducting multiple studies and understanding the influence of each trial on enrollment into the others. The unicenter, multiple-project screen log is one tool that may help to achieve these goals.