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.

Efficacy of computer-assisted management of respiratory failure in neonates.

We modified an algorithm for mechanical ventilation of infants with respiratory distress syndrome to create an interactive user-friendly computer program. To determine the effectiveness of this computer program, we evaluated the correction of deranged arterial blood gases in three groups of neonates: group I, treated before the introduction of the computer into the nursery; group II, managed by pediatric residents with the guidance of the computer program; group III, treated after the introduction of the computer into the nursery but managed without consideration of the computer output. Arterial blood gas values improved more frequently in the neonates managed with computer consultation (group II, 65/75, 87%) than in both control groups (group I, 37/57, 65%, P less than .005; and group III, 46/63, 73%, P less than .05). Furthermore, increases in ventilatory support in the presence of normal arterial blood gas values occurred only in patients managed without computer guidance. In a teaching institution, more effective care of neonates with respiratory failure may be facilitated by computer-assisted management of mechanical ventilators.

Bronchoscopic findings in infants treated with high-frequency jet ventilation versus conventional ventilation.

To identify tracheobronchial abnormalities associated with assisted ventilation, 40 infants with respiratory distress syndrome randomized to receive either short-term (48 hours) conventional or high-frequency jet ventilation were studied. Flexible fiberoptic bronchoscopy (n = 13) was performed and/or clinical and radiographic assessments were used to evaluate for laryngeal, tracheal, and bronchial lesions. There was no bronchoscopic evidence of necrotizing tracheobronchitis after either high-frequency jet ventilation (n = 8) or conventional ventilation (n = 5). Laryngotracheomalacia and nodular vocal cords were the most common abnormalities noted, and they occurred with equal frequency in both groups. Study infants who were not bronchoscoped had no clinical or radiographic evidence of tracheal or mainstem bronchial obstruction. One patient did have microscopic evidence of necrotizing tracheobronchitis at autopsy, however. It is concluded that short-term treatment of respiratory distress syndrome with high-frequency jet ventilation may be performed without undue risk of tracheobronchial injury.

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.

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.

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.

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.

A heat and humidification system for high frequency jet ventilation.

The clinical application of high frequency jet ventilation (HFJV), especially in pediatrics, has been hindered by the lack of adequate heating and humidification of the delivered gas. A technique of injecting particulate water into the gas from the jet ventilator has been described in the literature. However, it has been used primarily on adults and may cause fluid overload or hypothermia when used on infants. We describe a device for use during HFJV that provides gas (free of particulate water) to the patient at or near body temperature, with a relative humidity of 91%. This system has been used on 34 persons (14 premature infants, 17 small children, and 3 adults) without complications associated with improper conditioning of inspired gas.

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.

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.

Modification of a ventilator pressure monitoring circuit to permit display of mean airway pressure.

We modified the pressure gauge of a Bourns BP200 infant ventilator to allow it to display either mean airway pressure (Paw) or conventional airway pressure fluctuations. The modification consists of a pneumatic toggle switch and a needle valve connected in-line to the pressure gauge. When the switch is activated, the resistance of the needle valve and the compliance of the pressure gauge combine to form a pneumatic low-pass filter, whose output is read as Paw on the pressure gauge.

A new patient-circuit adapter for use with high frequency jet ventilators.

Current techniques of connecting a patient's endotracheal tube to the delivery circuit of a high frequency jet ventilator have several disadvantages. We describe a rigid, interchangeable adapter with a built-in jet injector that connects to any type or size of endotracheal tube. The device is reusable and avoids some of the disadvantages, such as catheter kinking, difficulty in accommodating injectors of different diameters, and tracheal tube obstruction, inherent in other commonly used techniques. It has been used successfully on 44 patients ranging in size from premature infants to adults.

An in-hospital evaluation of the sonic mist ultrasonic room humidifier.

It is generally recognized that nebulizers can be a source of nosocomial infection. 'Cold mist' room humidifiers are a particular problem because they are difficult to sterilize. We evaluated a new device, the Sonic Mist ultrasonic room humidifier, to determine how quickly it became contaminated during continuous use by a population of cystic fibrosis patients. In addition, the study was designed to test the effectiveness of placing a bacterial filter on the air inlet of the humidifier. We found that the entire humidifier could withstand repeated gas sterilization. Data obtained from 18 humidifiers involving cystic fibrosis patients indicate that the earliest humidifier contamination occurred after 5 days of continuous use. Although all patients had large numbers of gram-negative bacilli as predominant sputum flora, only 7 episodes of contamination were found during 34 humidifier-use periods. Three units equipped with filters became contaminated (5-7 days) and four unfiltered units became contaminated (6-11 days), indicating that the use of an inlet filter made no apparent difference. The organisms recovered from contaminated units were not found as sputum flora and would not generally be considered of clinical significance in cystic fibrosis sputum cultures. Probable sources of the organisms were room dust and hand contamination. A further test of the inlet filter was performed by exposing filtered and unfiltered units to mist from an intentionally contaminated humidifier. Again, the contamination rate was low and the filter apparently made no difference. These results indicate that the Sonic Mist humidifier may be appropriate for hospital use if adequate sterilization and contamination-monitoring practices are followed.

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.

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.

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.

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.