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Biomedical subjects

R L Chatburn

Publications and source records attributed to R L Chatburn.

At least 19 recordsLinked to original sources
PubMed1998

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.

Adolescent↗
PubMed1998

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.

Anthropometry↗
PubMed1997

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.

Airway Resistance↗
PubMed1996

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.

Adolescent↗
PubMed1996

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.

Bias↗
PubMed1994

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.

Analysis of Variance↗
PubMed1990

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.

Age Factors↗
PubMed1990

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.

Child↗
PubMed1989

High-frequency jet ventilation in neonatal pulmonary hypertension.

To determine if high-frequency jet ventilation is beneficial in neonates with persistent pulmonary hypertension, we compared the ventilator settings, blood gas concentrations, and outcome of infants who met established criteria for a high predictive mortality. During a six-year period, 14 neonates who had severe respiratory failure and hypoxemia while receiving conventional ventilation were treated with high-frequency jet ventilation. Twenty-three comparable infants meeting the same criteria were treated exclusively with conventional ventilation. After initiation of high-frequency jet ventilation there was a significant reduction in mean airway pressure and partial pressure of arterial carbon dioxide (PaCO2). In contrast, neonates treated exclusively with conventional ventilation continued to have higher airway pressures and PaCO2. However, there was no difference in the alveolar-to-arterial oxygen gradient, air leakage, incidence of bronchopulmonary dysplasia, or duration of assisted ventilation or oxygen supplementation. Furthermore, mortality was comparable in both groups of infants. These preliminary observations suggest that high-frequency jet ventilation can reduce airway pressure and PaCO2 in neonates with persistent pulmonary hypertension but does not appear to improve outcome.

Carbon Dioxide↗
PubMed1989

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.

Animals↗
PubMed1988

Optimal positive end-expiratory pressure therapy in infants and children with acute respiratory failure.

Positive end-expiratory pressure (PEEP) has become a mainstay in the treatment of hypoxemic acute respiratory failure (ARF). Whereas PEEP improves arterial oxygen tension by decreasing intrapulmonary shunting, it may also impair cardiac output and hence decrease systemic oxygen transport. Inasmuch as optimizing oxygen transport is a goal of therapy in ARF, we sought to determine if the level of PEEP that results in maximal oxygen transport could be estimated from measurements of compliance of the respiratory system (Crs) or PaO2. We studied the effects of PEEP application on cardiorespiratory parameters in 15 children who required mechanical ventilation for ARF. Static Crs, PaO2, central venous and arterial blood pressures, indicator dilution cardiac index (CI), and oxygen transport were determined at 0, 3, 6, 9, 12, and 15 cm H2O PEEP. PaO2 increased significantly at PEEP levels greater than or equal to 9 cm H2O (p less than 0.001), while CI fell by 15% between 0 and 15 cm end-expiratory pressure (p less than 0.02). Crs and oxygen transport did not change significantly with increasing levels of PEEP. The level of PEEP resulting in maximal oxygen transport ranged from 0 to 15 cm H2O, and in all patients it corresponded to PEEP of best CI. At levels of PEEP above that associated with maximal oxygen transport, CI and oxygen transport fell significantly, while PaO2 continued to rise. No relationship between Crs and oxygen transport was observed. In our normovolemic patients with ARF, neither PaO2 nor Crs predicted PEEP of maximal oxygen transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

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.

Bronchi↗
PubMed1987

Randomized trial of high-frequency jet ventilation versus conventional ventilation in respiratory distress syndrome.

To compare high-frequency jet ventilation (HFJV) with pressure-limited time-cycled conventional ventilation (CV), we randomized 41 infants with clinical and radiographic evidence of respiratory distress syndrome during the first day of life to receive either HFJV or CV. Standardized ventilatory protocols were used for 48 hours, after which CV was administered to both groups. Despite comparable oxygenation (arterial/alveolar oxygen tension ratio), mean airway pressure was lower in the HFJV group (9 +/- 2 vs 13 +/- 2 cm H2O, P less than 0.001), and thus the arterial/alveolar oxygen tension ratio corrected for mean airway pressure was improved in the HFJV group (P less than 0.05). PaCO2 was lower during HFJV (37 +/- 3 vs 42 +/- 3 mm Hg, P less than 0.05) despite a comparable peak inspiratory pressure. The incidence of air leaks, progression of intraventricular hemorrhage, and mortality during the 48-hour period did not differ between the two groups. Bronchoscopies in eight infants given HFJV and five given CV revealed no microscopic evidence of necrotizing tracheobronchitis, but one infant given HFJV had evidence of necrotizing tracheitis at autopsy. We conclude that for 48 hours during the acute stage of respiratory distress syndrome, HFJV can maintain adequate gas exchange at lower mean airway pressure than during CV, without an increase in the incidence of side effects.

Clinical Trials as Topic↗