Outcomes research in respiratory care.

Outcomes research seeks to understand the end results of particular health care interventions. End results include effects that people experience and care about, such as change in ability to function. The modern outcomes movement in the United States had its beginnings in the early 1980s, with an official start when Congress created the Agency for Health Care Policy and Research in 1989. Today known as the Agency for Healthcare Research and Quality, this agency supports outcomes research that is designed to answer 4 questions: (1) What works? (2) What doesn't? (3) When in the course of illness does it work or not? and (4) At what cost? Outcomes research provides the data for evidence-based medicine. Both activities work together in a continuous quality improvement cycle under the general heading of disease management. Outcomes research includes such things as epidemiology studies, clinical trials (designed as effectiveness studies), quality of life surveys, and cost analyses. Outcomes research is distinguished from traditional clinical research more by its focus than its methods. For example, outcomes research is population-centered rather than disease-centered, deals more with processes of care than drugs and devices, and relies less on the "hard sciences" such as physics and biochemistry and more on the social sciences such as economics, behavioral sciences, and epidemiology. Appropriate outcomes measures may be classified as (A) clinical, such as physiologic measures and mortality; (B) economic, such as direct and indirect costs of care; or (C) humanistic, such as quality of life and patient satisfaction with care. Respiratory therapists need to be familiar with outcomes research issues in order to be educated consumers of (and to participate in) future studies.

Decision analysis for large capital purchases: how to buy a ventilator.

We describe a formal decision-making procedure for purchasing intensive care ventilators. We adapted a general decision-making tool known as an additive, compensatory, multiattribute utility model. The model incorporates input from the various stakeholders in the decision. It identifies the factors that are important in the decision and the alternative decision options, weights the factors, ranks the alternative decisions on how well they serve the factors, and finally provides an overall score that identifies the best option. This model provides a more objective and analytical approach than is often used in purchasing decisions. The benefits include simplifying discussion among stakeholders and assisting administrators in justifying major purchase proposals.

A new system for understanding modes of mechanical ventilation.

Numerous ventilation modes and ventilation options have become available as new mechanical ventilators have reached the market. Ventilator manufacturers have no standardized terminology for ventilator modes and ventilation options, and ventilator operator's manuals do not help the clinician compare the modes of ventilators from different manufacturers. This article proposes a standardized system for classifying ventilation modes, based on general engineering principles and a small set of explicit definitions. Though there may be resistance by ventilator manufacturers to a standardized system of ventilation terminology, clinicians and health care equipment purchasers should adopt such a system in the interest of clear communication--the lack of which prevents clinicians from fully understanding the therapies they administer and could compromise the quality of patient care.

Electrical stimulation for swallowing disorders caused by stroke.

BACKGROUND: An estimated 15 million adults in the United States are affected by dysphagia (difficulty swallowing). Severe dysphagia predisposes to medical complications such as aspiration pneumonia, bronchospasm, dehydration, malnutrition, and asphyxia. These can cause death or increased health care costs from increased severity of illness and prolonged length of stay. Existing modalities for treating dysphagia are generally ineffective, and at best it may take weeks to months to show improvement. One common conventional therapy, application of cold stimulus to the base of the anterior faucial arch, has been reported to be somewhat effective. We describe an alternative treatment consisting of transcutaneous electrical stimulation (ES) applied through electrodes placed on the neck. OBJECTIVE: Compare the effectiveness of ES treatment to thermal-tactile stimulation (TS) treatment in patients with dysphagia caused by stroke and assess the safety of the technique. METHODS: In this controlled study, stroke patients with swallowing disorder were alternately assigned to one of the two treatment groups (TS or ES). Entry criteria included a primary diagnosis of stroke and confirmation of swallowing disorder by modified barium swallow (MBS). TS consisted of touching the base of the anterior faucial arch with a metal probe chilled by immersion in ice. ES was administered with a modified hand-held battery-powered electrical stimulator connected to a pair of electrodes positioned on the neck. Daily treatments of TS or ES lasted 1 hour. Swallow function before and after the treatment regimen was scored from 0 (aspirates own saliva) to 6 (normal swallow) based on substances the patients could swallow during a modified barium swallow. Demographic data were compared with the test and Fisher exact test. Swallow scores were compared with the Mann-Whitney U test and Wilcoxon signed-rank test. RESULTS: The treatment groups were of similar age and gender (p > 0.27), co-morbid conditions (p = 0.0044), and initial swallow score (p = 0.74). Both treatment groups showed improvement in swallow score, but the final swallow scores were higher in the ES group (p > 0.0001). In addition, 98% of ES patients showed some improvement, whereas 27% of TS patients remained at initial swallow score and 11% got worse. These results are based on similar numbers of treatments (average of 5.5 for ES and 6.0 for TS, p = 0.36). CONCLUSIONS: ES appears to be a safe and effective treatment for dysphagia due to stroke and results in better swallow function than conventional TS treatment.

Pediatric asthma disease management.

The prevalence of asthma in children in the United States is estimated at more than 5% of the population, and it has risen more than 40% in the previous decade. Several guidelines for the management of acute and chronic asthma exist, and they all emphasize several basic components including state-of-the-art pharmacologic treatment, trigger avoidance, and patient self-management skills. This Article highlights the necessary components for pediatric asthma disease management to insure a smooth continuum of care across all disciplines and settings.

A cost-saving algorithm for children hospitalized for status asthmaticus.

OBJECTIVE: To test the ability of an assessment-driven algorithm for treatment of pediatric status asthmaticus to reduce length and cost of hospitalization. DESIGN: Nonrandomized, prospective, controlled trial. SETTING: Tertiary care children's hospital. PATIENTS: Children aged 1 to 18 years hospitalized for status asthmaticus; 104 were treated using the asthma care algorithm (intervention) and 97 using unstructured standard treatment (control). INTERVENTION: Patients were treated using either an assessment-based algorithm or standard care practices. The algorithm group was treated with standard medications (aerosolized albuterol, systemic corticosteroids, epinephrine, ipratropium) administered at a frequency driven by the patient's clinical condition. Specific criteria were outlined for decreasing or augmenting therapy, transferring to intensive care, and discharging to home. A unique patient record containing assessments, algorithm cues, and a treatment record was used. Intervention group patients were interviewed by telephone 1 week after discharge. MAIN OUTCOME MEASURES: Hospital length of stay, cost per hospitalization, relapse rate, protocol adherence. RESULTS: Average hospital stay for intervention patients was significantly shorter than for control patients (2.0 vs 2.9 days, P<.001). Although intervention patients received fewer aerosolized albuterol doses than controls, there was no difference in short-term relapse rate between groups. The intervention saved more than $700 per patient in hospital charges. Adherence to the protocol was excellent, with only 8 variances per patient stay out of more than 150 opportunities. CONCLUSION: An intensive, assessment-driven algorithm for pediatric status asthmaticus significantly reduces hospital length of stay and costs without increasing morbidity.

Estimation of total body water in very-low-birth-weight infants by using anthropometry with and without bioelectrical impedance and H2[(18)O].

The usefulness of bioelectrical impedance (BI) with anthropometry to measure total body water (TBW) was evaluated in very-low-birth-weight (VLBW) infants. A specific regression equation to measure TBW in a VLBW population was developed by simultaneously using the H2[(18)O] dilution method and BI in 12 infants with a gestational age of 24-30 wk and weighing <1200 g at birth. After an oral dose of H2[(18)O], the tracer dilution was measured in expired carbon dioxide. BI measurements were made with a model BIA-101 apparatus (RJL Systems, Detroit). Electrodes were placed in the standard position as well as proximally on the leg and the forearm. The best correlation was observed between body weight and TBW (r = 0.989). For BI, the best correlation was obtained when gestational age was used as a covariable along with body weight and crown-heel length (r = 0.985). The correlation was comparable with proximal electrode placement (r = 0.985). The new correlation was evaluated in 6 infants weighing < 1008 g. A significant correlation between BI and H2[(18)O]-measured TBW was observed (r = 0.988). Published regression equations for infants consistently gave higher estimates of TBW in another group of 14 infants weighing <1200 g than did the new correlations. TBW represented 84-95% of body weight in these VLBW infants. TBW could be computed simply from body weight alone. Use of BI and length as covariables did not add significantly to the estimate of TBW in VLBW infants.

Effect of exogenous and endogenous nitric oxide on the airway and tissue components of lung resistance in the newborn piglet.

Despite widespread reports of the vasodilatory actions of nitric oxide (NO), little is known of the relaxant effect of NO on newborn airways or lung parenchymal structures. We studied the effects of inhaled NO at 20, 40, and 80 ppm on lung (Rl), tissue (Rti), and airway (R(aw)) resistance in 13 2-5-d-old anesthetized, ventilated, open-chested piglets. Rl was measured from transpulmonary pressure and air flow. Rti was measured by alveolar capsules, and R(aw) was calculated as the difference between Rl and Rti. Any given concentration of inhaled NO (20, 40, or 80 ppm) significantly decreased Rl (p < 0.001), Rti (p < 0.001), and R(aw) (p < 0.05). In addition, blockade of endogenous NO with 30 mg/kg N omega-nitro-L-arginine methyl ester (L-NAME) given i.v. in 12 piglets significantly increased Rti and Rl with variable changes in R(aw), and caused a decrease in dynamic compliance. Readministration of NO to eight piglets induced a significant decreased in Rl and Rti at 20 and 80 ppm, whereas R(aw) significantly decreased only at 80 ppm. Pulmonary arterial pressure decreased after exposure to inhaled NO and increased after L-NAME administration. Systemic arterial pressure was unaffected by inhaled NO but increased after L-NAME administration. Our results indicate that Rl, R(aw), and Rti are reduced by exogenous NO, suggesting NO-mediated airway smooth muscle relaxation throughout the newborn lung. In contrast, blockade of endogenous NO significantly increases only Rti, suggesting a physiologic role for endogenous NO in regulation of peripheral contractile elements. We speculate that NO-mediated modulation of resistance in pulmonary parenchyma may serve to regulate the balance of ventilation and perfusion and resultant gas exchange in the lungs during early postnatal development.

Evaluation of instrument error and method agreement.

Safely operating life support equipment and evaluating new technology both require some basic understanding of measurement theory. Measurement errors fall into two main categories: systematic errors (predictable problems usually due to calibration) and random errors (unpredictable). These two types of errors can be quantified by experiments involving repeated measurements of standards or "true" values. Systematic error (called bias) is usually expressed as the mean difference between measured and true values. Random error, called imprecision, can be expressed as the standard deviation of measured values. Total error can be expressed as an error interval, being the sum of bias and some multiple of imprecision. An error interval is a prediction about the error of some proportion of future measurements (e.g., 95%) at some level of confidence (e.g., 99%) based on the variability of the sample data and the sample size. Specifically, a tolerance interval gives an estimate of the true value of some variable given repeated measurements with an assumed valid measurement system. An inaccuracy interval predicts the validity of a measurement system with an estimate of the difference between measured true values (given that a standard or true value is available for measurement). An agreement interval evaluates whether or not one measurement system (e.g., a known valid system) can be used in place of another (e.g., a new unknown system). Statistical analyses such as correlation and linear regression are commonly seen in the literature, but not usually appropriate for evaluation of new equipment. Instrument performance evaluation studies should start out with a decision about the level of allowable error. Next, experiments are designed to obtain repeated measurements of known quantities (inaccuracy studies) or of unknown quantities by two different measurement systems (i.e., agreement studies). The first step in data analysis is to generate scatter plots of the raw data for review of validity (e.g., outliers). The next step is to make sure the data adhere to the assumption of normality. The third step is to calculate basic descriptive statistics, such as the mean and standard deviation. Finally, the data should be presented in graphic form with the differences plotted against the reference values and including numerical values for the calculated error intervals. The key idea to remember is that device evaluation and method agreement studies are based on the desire to know how much trust we should place in single measurements that may be used to make life support decisions.

Inspiratory pressure/maximal inspiratory pressure: does it predict successful extubation in critically ill infants and children?

OBJECTIVE: To evaluate the accuracy of the initial negative inspiratory pressure (PI) to maximal negative inspiratory pressure (PImax) ratio in predicting extubation outcome for intubated infants and children. DESIGN: A prospective study. SETTING: Pediatric intensive care unit. PATIENTS: A sample of 50 stable intubated pediatric patients who were judged clinically ready for extubation. METHODS: Using a one-way valve, PI and PImax were measured in all patients, after which the < or = ratio PI/PImax was calculated and its accuracy in predicting extubation outcome evaluated. MEASUREMENTS AND RESULTS: A total of 39 patients (78%) were successfully extubated and 11 patients (22%) were not. The mean PI/PImax ratio was not significantly different between extubation successes (0.36 +/- 0.14) and failures (0.45 +/- 0.1) (P > 0.05). The cut-off value of 0.3 for PI/PImax identified in adult patients did not discriminate between extubation success and failure in children. Furthermore, a discriminatory cut-off value other than 0.3 could not be identified for infants and children. CONCLUSION: The PI/PImax ratio cannot be used to predict extubation outcome in pediatric patients. Indices that predict extubation outcome in adults should not be extrapolated to infants and children before testing and validation.

Mechanical ventilators optimized for pediatric use decrease work of breathing and oxygen consumption during pressure-support ventilation.

OBJECTIVES: a) To investigate whether the patient work of breathing needed to trigger inspiration is affected by the type of ventilator delivering pressure-support ventilation for mechanically ventilated pediatric patients. b) To determine whether changes in oxygen consumption (VO2) trend with changes in work of breathing and would thus be helpful in tracking work of breathing. DESIGN: Prospective study. SETTING: Pediatric intensive care unit at a university hospital. PATIENTS: Nine mechanically ventilated patients (2 to 75 months of age). INTERVENTIONS: While maintaining a constant pressure-support ventilation level, patients were alternately supported with the Siemens Servo 900C, the Bird VIP, and the Newport Wave E200 ventilators in random order. MEASUREMENTS AND MAIN RESULTS: Work of breathing, defined as the integral of the pressure-volume curve corresponding to negative pressure, was calculated with a pulmonary monitoring system. VO2 was measured with a metabolic cart. Patient distress levels were assessed using the COMFORT scale, a behavioral scoring system. Mean values (20 breaths/patient) for measured variables with each ventilator were compared using analysis of variance and Scheffé tests, with p < .05 indicating statistical significance. The lowest VO2 (103 +/- 35 mL/min/m2) and work of breathing (24 +/- 15 g.cm/m2) were achieved with the Bird VIP ventilator and were significantly (p < .05) lower than those values obtained with either the Siemens Servo 900C (VO2 147 +/- 33 mL/min/m2; work of breathing 49 +/- 18 g.cm/m2) or the Newport Wave E200 (VO2 122 +/- 33 mL/min/m2; work of breathing 35 +/- 15 g.cm/m2). Also, the values of work of breathing and VO2 obtained using the Newport Wave E200 were significantly (p < .05) lower than those values obtained using the Servo 900C. No change in behavioral distress occurred when the ventilators were changed. In all patients, there was a clear similarity in the trends of VO2 and work of breathing. CONCLUSIONS: We conclude that VO2 and work of breathing may be reduced significantly using the latest generation of mechanical ventilators optimized for infant and pediatric use. Because work of breathing is less with the Bird VIP than the other two ventilators tested, leading to a corresponding decrease in VO2, we suggest that the Bird VIP better adapts the patient to the ventilator and may facilitate weaning from ventilatory support. We also suggest that changes in VO2 might be helpful in tracking changes in work of breathing.

Technical description and classification of modes of ventilator operation.

These changes are proposed as a starting point for the more logical application of ventilator terminology and are for your consideration and debate. It is our contention that this system can be easily adopted once the basics of the classification system are understood.

Early randomized intervention with high-frequency jet ventilation in respiratory distress syndrome.

To determine whether early use of high-frequency jet ventilation reduces neonatal mortality or pulmonary morbidity rates, we randomly selected 42 infants with clinical and radiographic evidence of severe respiratory distress syndrome to receive either high-frequency jet ventilation or conventional ventilation. Separate sequential analyses (two-sided, alpha = 0.05, power = 0.95 to detect 85:15 advantage) were performed for mortality rates, air leaks, bronchopulmonary dysplasia, intraventricular hemorrhage, and assignment crossover, and a combined analysis was performed, with death overriding other outcome variables. Enrollment was completed when the combined analysis reached the sequential design boundary indicating no treatment difference. Mortality rates (19% among infants receiving high-frequency jet ventilation vs 24% among infants receiving conventional ventilation), the incidence of air leaks (48% vs 52%), bronchopulmonary dysplasia (39% vs 41%), and intraventricular hemorrhage (33% vs 43%), and assignment crossovers (14% vs 24%) did not differs significantly between the treatment groups. We conclude that early use of high-frequency jet ventilation does not prevent or substantially reduce mortality or morbidity rates associated with assisted ventilation.

Patterns of practice in neonatal and pediatric respiratory care.

UNLABELLED: Because little information has been available regarding common respiratory care practices in neonatology and pediatrics, it has been difficult to develop departmental standards of care. We therefore conducted a national survey of current practices, hoping to establish whether any de facto standards exist in the U.S. METHODS: A 47-item multiple-choice survey instrument was mailed in 1988 to 689 U.S. hospitals that included all neonatal and perinatal high-risk centers. RESULTS: Response was received from 323 hospitals, for a 47% response rate. Some de facto standards do seem to exist, notably (1) q 2 h ventilator checks, (2) continuous measurement of oxygen concentration in oxygen hoods and ventilator circuits, (3) staffing ratio of four ventilator patients to one respiratory care practitioner, and (4) changing of ventilator circuits q 48 h. CONCLUSION: While we do not claim that such de facto standards have a scientific basis, we suggest that respiratory care services whose practices vary from the de facto standards should investigate why their own practices differ and whether they can be justified.

Low frequency oscillatory ventilation through the suction channel of a pediatric bronchoscope.

To determine whether low frequency oscillatory ventilation (LFOV) may be safely applied through the suction channel of a pediatric fiberoptic bronchoscope, we devised a system using a combination of jet ventilation and constant air suction, both delivered with a single interface valve. The system was tested on an in vitro lung model and on rabbits. With tidal volumes of 12 mL, inadvertent increase in functional residual capacity (FRC) measured in the lung model was minimal. All rabbits experienced marked hypoventilation (PaCO2 62 +/- 2 torr) on introduction of the bronchoscope, which promptly improved with administration of LFOV (PaCO2 41 +/- 4 torr). That baseline FRC remained stable indicated that air trapping did not occur. We conclude that LFOV improves ventilation in rabbits during bronchoscopy without causing air trapping. A similar system might be applied during bronchoscopy in full-term and premature infants, thus facilitating safer and more complete visualization of their airways and preserving the possibility of obtaining samples by suction.