New advances and validation of knowledge management tools for critical care using classifier techniques.

An earlier version (2.0) of the case-based reasoning (CBR) tool, called IDEAS for ICU's, allowed users to compare the ten closest matching cases to the newest patient admission, using a large database of intensive care patient records, and physician-selected matching-weights [1,2]. The new version incorporates matching-weights, which have been determined quantitatively. A faster CBR matching engine has also been incorporated into the new CBR. In a second approach, a back-propagation, feed-forward artificial neural network estimated two classes of the outcome "duration of artificial ventilation" for a subset of the database used for the CBR work. Weight-elimination was successfully applied to reduce the number of input variables and speed-up the estimation of outcomes. New experiments examined the impact of using a different number of input variables on the performance of the ANN, measured by correct classification rates (CCR) and the Average Squared Error (ASE).

Randomized trial of long-term diuretic therapy for infants with oxygen-dependent bronchopulmonary dysplasia.

STUDY OBJECTIVE: To determine whether long-term oral diuretic therapy would improve the pulmonary function of preterm infants with bronchopulmonary dysplasia. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Level III intensive care nursery. INTERVENTION: We randomly selected 43 stable patients with oxygen-dependent bronchopulmonary dysplasia to receive either orally administered spironolactone and chlorothiazide or placebo. These drugs were continued until the patients no longer required supplemental oxygen. Both groups received furosemide as needed. MEASUREMENTS AND RESULTS: Each infant had pulmonary function tests at study entry, 4 weeks after study entry, 1 week and 8 weeks after being weaned to room air and off study drugs, and at 1 year of corrected age. Pulmonary function tests include dynamic pulmonary compliance, airway resistance, thoracic gas volume, and maximal expiratory flow at functional residual capacity; most of the infants had functional residual capacity measured. Between the first and second pulmonary function tests (while the infants were receiving diuretic or placebo), the infants in the diuretic group had a significant improvement in dynamic pulmonary compliance (46%; p < 0.001) and airway resistance (31%; p < 0.05); there were no changes in compliance or resistance in the placebo group. Although patients in both the diuretic and the placebo groups required progressively less supplemental oxygen, by 4 weeks after study entry the patients in the diuretic group needed less supplemental oxygen than did those in the placebo group (p < 0.01). There were no significant differences in results of serial pulmonary function tests in either group after discontinuation of diuretic therapy. Despite the significant differences in pulmonary function between the two groups, there was no significant difference between them in the total number of days that supplemental oxygen was required. Significantly more infantsin the placebo group received more than 10 doses of furosemide on an as-needed basis. CONCLUSIONS: Long-term diuretic therapy in stable infants with oxygen-dependent bronchopulmonary dysplasia, after extubation, improves their pulmonary function and decreases their fractional inspired oxygen requirement, but does not decrease the number of days that they require supplemental oxygen. The improvement in pulmonary function associated with diuretic therapy is not maintained after treatment is discontinued.

A radiographic method for estimating lung volumes in sick infants.

Estimation of lung volumes by conventional methods in sick infants is technically difficult and is the subject of controversy. In this study, we compared both thoracic gas volume (TGV), measured with an infant whole body plethysmograph, and functional residual capacity (FRC), determined by the nitrogen washout technique, to planimetric measurements of anteroposterior chest radiographs in 26 infants with bronchopulmonary dysplasia (BPD). The tidal volume (TV) of each patient was added to TGV and FRC because these were measured at the end of expiration whereas chest radiographs were taken at the end of spontaneous inspiration. The regression equations expressing the relationships between TGV and right+left lung field areas [A+B], and between FRC and lung areas are expressed as follows: [TGV+TV](mL) = 3.3 mL/cm2 x [A+B] cm2 + 24 mL and [FRC+TV](mL) = 3.5 mL/cm2 x [A+B] cm2 - 13.5 mL. Correlation coefficients of 0.9 and 0.7 for TGV and FRC, respectively, suggest a stronger correlation between TGV and lung areas than between FRC and lung areas. Lung areas measured by planimetry correlate closely with physiological measurement of lung volumes. We conclude that the planimetric method is an inexpensive and reliable technique for estimating lung volumes in young infants with BPD when chest radiographs are available.

A double-blind, randomized study of sodium cromoglycate versus placebo in patients with cystic fibrosis and bronchial hyperreactivity.

To evaluate the effects of sodium cromoglycate (SCG) on patients with cystic fibrosis (CF) and with bronchial hyperreactivity, a long-term, double-blind, placebo-controlled, crossover study was performed. Fourteen patients with CF and without asthma (aged 7 to 29 years) and with bronchial hyperreactivity entered the study. Each patient received 8 weeks of 1% SCG nebulizer solution three to four times daily and 8 weeks of placebo. Seven patients received the treatment in the order SCG/placebo and seven patients in the reverse order. Evaluation of SCG effect was performed every 4 to 8 weeks by (1) clinical assessment of symptoms, (2) clinician and patient/parent opinion, (3) pulmonary function tests, and (4) methacholine provocation tests. After two patients were withdrawn for lack of cooperation, the results were evaluated for treatment effect (SCG versus placebo), period effect (whether SCG was administered first or last), or combination of both. No significant difference was found for these parameters for the clinical assessment of symptoms, the patient/parent and clinician opinion, their subjective preferences, the metacholine challenges, or the pulmonary function tests. The study did not demonstrate any benefit from the use of SCG in patients with CF and with bronchial hyperreactivity and does not support the routine use of SCG in patients with CF.

Experience with a metered-dose inhaler with a spacer in the pediatric emergency department.

Studies of adults suggest that metered-dose inhalers with spacers are as effective as hand-held nebulizers for bronchodilator delivery. We studied 13 children with acute asthma. They received two puffs every 2 minutes from metered-dose inhalers with spacers (range, 4 to 14 puffs) titrated until improvement stopped. Peak expiratory flow increased 34% for metered-dose inhalers with spacers after the first 2 puffs and increased 87% for metered-dose inhalers with spacers after dose titration. After titration, respiratory rate decreased by 12%, heart rate increased by 2%, and breath sounds improved in 92% of the patients. We concluded that the metered-dose inhalers with spacers are an effective device for the treatment of asthma in the pediatric emergency department and that the use of metered-dose inhalers with spacers with titration can achieve significant bronchodilation in the treatment of patients with acute asthma.

Short-term variability of pulmonary function tests in infants with bronchopulmonary dysplasia.

We determined the short-term variability of pulmonary function in infants recovering from bronchopulmonary dysplasia. Sixteen infants with birth weight of 1,231 +/- 929 grams (mean +/- SD) and gestational age of 29 +/- 4 weeks were studied twice at 17 +/- 8 weeks postnatally at intervals of 4 to 8 days during a period of clinical stability. The infants were still on supplemental oxygen but were off diuretics and bronchodilators. We used a modification of the rapid thoracic compression method to measure forced expiratory flow (Vmax FRC) and the time constant (tau) of expiratory flow at functional residual capacity. Thoracic gas volume (TGV), mean and total airway resistance (RawM and RawT), and mean and total specific airway conductance (SGawM and SGawT) were measured in a whole body pressure plethysmograph. An esophageal balloon was used to measure dynamic pulmonary compliance (Cdyn). Variabilities were defined as the standard deviation of percent changes between the first and second tests. They were 30% for VmaxFRC, 23% for tau, 12% for TGV, 20% for RawM, 35% for RawT, 25% for SGawM, 72% for SGawT, and 23% for Cdyn. All these tests are useful in assessing pulmonary function of infants with BPD; however, their variability must be taken into account when interpreting short-term changes.

Effects of inhaled metaproterenol and atropine on the pulmonary mechanics of infants with bronchopulmonary dysplasia.

We evaluated the individual and combined effects of an inhaled beta-adrenergic agent (metaproterenol) and an inhaled anticholinergic agent (atropine) on the pulmonary function of infants with bronchopulmonary dysplasia. In this randomized, double-blind study we studied 15 infants at a mean postnatal age of 15.8 weeks (range 4-28 weeks). On 4 successive days, pulmonary function tests were measured before and after a single treatment with one of the following four aerosols: placebo, metaproterenol, atropine, and combined metaproterenol and atropine. Following treatment with metaproterenol, atropine, and combined metaproterenol and atropine, airway resistance and maximal expiratory flow at functional residual capacity improved significantly when compared with baseline. Pulmonary function values returned toward baseline by 3 hours after the treatments. We found no significant differences between the effects of metaproterenol and atropine and were unable to show any synergy of the two agents.

Improving pulmonary function does not decrease oxygen consumption in infants with bronchopulmonary dysplasia.

To determine whether the high oxygen consumption VO2 in infants with bronchopulmonary dysplasia (BPD) is caused by increased mechanical power of breathing, and if improvement of pulmonary mechanics would reduce mechanical power of breathing and VO2 we gave 16 infants with oxygen-dependent BPD at 19.5 +/- 10.7 (mean +/- SD) weeks of age placebo, theophylline, and orally administered diuretics or theophylline plus diuretics. Pulmonary mechanics, mechanical power of breathing, and VO2 were measured at the beginning and end of each study period. In the placebo group, all infants had elevated VO2 (7.4 +/- 1.4 mL/kg/min) and carbon dioxide production (6.6 +/- 1.2 mL/kg/min), increased airway resistance (59 +/- 30 cm H2O/L/sec), decreased dynamic compliance (0.073 +/- 0.024 mL/cm H2O/cm), increase respiratory rate (52 +/- 11), and increased mechanical power of breathing (2.22 +/- 1.05 kg.cm/kg/min). Treatment with theophylline, diuretics, and theophylline plus diuretics resulted in a significant improvement in pulmonary mechanics and mechanical power of breathing, but not in VO2. These results suggest that the increased VO2 in infants with BPD is not secondary to increased mechanical power of breathing.

Bias and precision of pulse oximeters and arterial oximeters.

We evaluated measurements of oxygen saturation from four noninvasive pulse oximeters, and two conventional arterial oximeters. Simultaneous measurements were obtained on each instrument on three different occasions in five healthy subjects breathing gas with an FIO2 of 1.00, 0.50, 0.21, 0.17, 0.15, 0.13 and 0.11. Mean bias relative to the sum of oxy-, carboxy-, and methemoglobins ranged from -0.4 to -2.6 percent for the pulse oximeters and +1.8 to -4.2 percent for the conventional oximeters. Two pulse oximeters performed well at all saturations down to 65 percent, while the others showed either increasing or decreasing bias below 80 percent saturation. Precision was approximately 2 percent for all instruments except one conventional oximeter with a precision of 0.7 percent. In the clinically relevant range, the performance of the noninvasive pulse oximeters was similar to conventional oximeters using arterial samples.

Oral theophylline and diuretics improve pulmonary mechanics in infants with bronchopulmonary dysplasia.

We studied the effects of orally administered theophylline and diuretics (chlorothiazide and spironolactone) on pulmonary mechanics in 16 infants with bronchopulmonary dysplasia. Their gestational age (mean +/- SD) was 28.5 +/- 3.4 weeks, and postnatal age at the time of study 19.5 +/- 10.7 weeks. The infants were randomized to two groups. Group 1 received successively placebo, theophylline, and theophylline plus diuretics; Group 2 received theophylline, placebo, and placebo plus diuretics on successive 4-day periods. Pulmonary function was measured before beginning the study (baseline) and at the end of each 4-day period. No significant changes in pulmonary function were noted after treatment with placebo. After treatment with theophylline, dynamic compliance (Cdyn) increased from baseline (mean +/- SD) 0.075 +/- 0.017 to 0.091 +/- 0.028 mL/cm H2O/cm (P less than 0.01), airway resistance (Raw) decreased from 67.19 +/- 36.71 to 41.44 +/- 22.50 cm H2O/L/sec (P less than 0.001), maximal expiratory flow at functional residual capacity (VmaxFRC) increased from 0.261 +/- 0.240 to 0.357 +/- 0.299 thoracic gas volume (TGV)/sec (P less than 0.01), and time constant decreased from 0.312 +/- 0.224 to 0.275 +/- 0.247 sec (P less than 0.02). After treatment with combined placebo and diuretics, Cdyn increased to 0.103 +/- 0.023 mL/cm H2O/cm (P less than 0.05), Raw decreased to 31.76 +/- 24.90 cm H2O/L/sec (P less than 0.001), VmaxFRC increased to 0.638 +/- 0.595 TGV/sec (P less than 0.02), and time constant decreased to 0.180 +/- 0.141 sec (P less than 0.05). After treatment with combined theophylline and diuretics, Cdyn increased to 0.118 +/- 0.017 mL/cm H2O/cm (P less than 0.001), Raw decreased to 35.98 +/- 25.85 cm H2O/L/sec (P less than 0.02), VmaxFRC increased to 0.479 +/- 0.377 TGV/sec (P less than 0.02), and time constant decreased to 0.180 +/- 0.137 sec (P less than 0.01). We conclude that theophylline and diuretics have additive effects on the improvement of pulmonary function in infants with bronchopulmonary dysplasia.

Absent hypoxic and hypercapneic arousal responses in children with myelomeningocele and apnea.

Hypoxic and hypercapneic arousal responses from quiet sleep were tested in seven infants with myelomeningocele and Arnold-Chiari malformation who were symptomatic with apnea and/or hypoventilation. All infants with myelomeningocele required tracheostomy and posterior fossa decompression. Responses were compared with those of nine healthy control infants. To assess hypoxic arousal, inspired PO2 was decreased until the end-tidal (alveolar) PO2 reached 45 mm Hg for a maximum of three minutes. Eleven studies were performed in seven infants with myelomeningocele, and arousal occurred in only two studies (18.2%). Eight of nine control infants aroused to hypoxia (89%). To test hypercapneic arousal, inspired PCO2 was increased until end-tidal PCO2 reached 60 mm Hg for a maximum of three minutes. Eight studies were performed on six infants with myelomeningocele, and arousal occurred in three studies (37.5%). All seven control infants studied aroused to hypercapnea (100%). Three infants with myelomeningocele subsequently died. Infants with myelomeningocele, Arnold-Chiari malformation, and apnea or hypoventilation have arousal deficits to respiratory stimuli.

In vivo response times for a heated skin surface CO2 electrode during rest and exercise.

The continuous, noninvasive estimation of arterial carbon dioxide tension (PaCO2) by heated skin surface electrodes has recently become available for pediatric patients. Skin surface (PsCO2) electrodes can enhance the safety of procedures such as intubation, bronchoscopy, ventilator changes, sleep studies, or measurement of the ventilatory response to CO2 or hypoxia. However, clinical situations that include rapid changes in PaCO2 demand knowledge of the in vivo response time. We compared the response of a heated PsCO2 electrode to end tidal CO2 (PetCO2) during abrupt changes in inspired CO2 from room air to 7% CO2 and back to room air. We obtained 54 curves on nine healthy subjects. There was an initial lag time with less than a 10% change in PsCO2. Then PsCO2 approached PetCO2 exponentially. For subjects at rest changing from breathing room air to 7% CO2, the initial lag time was 40 +/- 2 seconds and the 50% response time of the exponential portion was 46 +/- 3 seconds. Thus, it took 86 seconds for the electrode to record a 60% response to an abrupt increase in inspired CO2. The initial lag and 50% response time were considerably shorter during exercise (30 +/- 2 and 33 +/- 2 seconds) and even shorter when switched from breathing 7% CO2 to room air (23 +/- 2 and 21 +/- 2 seconds). Exercise did not further reduce the response time when CO2 was initially elevated, suggesting the faster response time was due to vasodilation of the skin due to elevated CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchopulmonary dysplasia. Chronic pulmonary disease following neonatal respiratory failure.

Infants with respiratory failure in the first weeks of life may develop a chronic pulmonary condition called bronchopulmonary dysplasia. Their lungs have areas of atelectasis and areas of air trapping from variable obstruction of the airways. These infants may be dependent on supplemental oxygen or a ventilator and may require hospitalization for months, and have symptoms of airway obstruction which last for years. They require meticulous medical management to avoid a number of common complications such as patent ductus arteriosus, cor pulmonale, tracheal stenosis, recurrent aspiration, and death. The condition of most infants improves over the first two years. Preliminary studies suggest that their exercise and pulmonary function is usually close to normal by school-age. The long-term implications for the increasing number of children with this disease who will soon reach adulthood are still unknown.

Lipid-laden macrophages in tracheal aspirates of newborn infants receiving intravenous lipid infusions: a cytologic study.

Seventy-four neonates with respiratory distress syndrome had cytologic study of tracheal aspirates. Thirteen, all of whom were receiving intravenous lipid and nothing orally had abundant macrophages with foamy cytoplasm, positive for intracytoplasmic lipid by Sudan black stain, in the tracheal aspiration specimens. Cytologic surveillance of tracheal aspiration specimens may be a useful method of monitoring infants receiving intravenous lipid infusions.

Developmental pattern of maximal transdiaphragmatic pressure in infants during crying.

Diaphragm strength was measured as maximal transdiaphragmatic pressure (Pdi) during airway occlusion in 38 infants aged 11.6 +/- 0.5 (S.E.) months postconception (mpc), range 8-21 mpc. All infants were asymptomatic at the time of study and required no mechanical ventilatory assistance. Ten infants had previous surgical correction of abdominal wall defects (gastroschisis/omphalocele); 10 infants had previous surgical correction of congenital diaphragmatic hernia; and 18 infants had no thoracic or abdominal surgery. The mean maximal Pdi for all infants was 72 +/- 3 cmH2O. There were no significant differences between the three groups. All infants with a maximal Pdi of less than 60 cmH2O were aged less than 10 mpc. After 13 mpc there was no significant increase in maximal Pdi. Between the ages 8-13 mpc there was a significant positive correlation between maximal Pdi and age postconception (r = 0.87, P less than 0.0005), reflecting a developmental pattern of increasing maximal transdiaphragmatic pressure in infants during crying.

Calibration of a heated transcutaneous carbon dioxide electrode to reflect arterial carbon dioxide.

The CO2 measured by a heated skin surface electrode is greater than arterial CO2. In this study we (1) determined the magnitude of this difference retrospectively, (2) adjusted the calibration of the heated transcutaneous CO2 electrode to reflect this difference, and (3) tested the validity of the calibration procedure prospectively. The retrospective study consisted of 252 simultaneous arterial and transcutaneous measurements on 38 infants and children (age range, 1 day to 6 yr). A linear regression analysis showed PtcCO2 = 1.61 X PaCO2 - 0.01 mmHg, r = 0.90 (p less than 0.0001). Because the intercept was virtually zero, we subsequently changed the calibration procedure by dividing the transcutaneous electrode reading by 1.61. The prospective study consisted of 269 more simultaneous arterial and transcutaneous measurements from 57 consecutive infants and children (age range, 1 day to 18 yr) using this calibration procedure. Regression analysis showed PtcCO2 = 1.02 X PaCO2 - 2.3 mmHg, r = 0.96 (p less than 0.0001). Thus, we found that the transcutaneous CO2 electrode, using this technique, reliably predicted the arterial CO2.

Distance running improves fitness in asthmatic children without pulmonary complications or changes in exercise-induced bronchospasm.

The effect of a distance running program was studied in 15 children with severe chronic asthma. Following a 6-week control period, the subjects ran four days a week for 6 weeks. The distance was increased gradually to 3.2 km. Clinical status and need for treatment did not change. Episodes of exercise-induced bronchospasm were readily reversed. Fitness improved as measured by the distance run in 12 minutes (P less than .005). Resting pulmonary function did not change. Exercise-induced bronchospasm following a bicycle ergometer stress test under comparable conditions did not change. Ventilatory muscle strength, measured as the maximal inspiratory pressure, and endurance, measured as the sustainable inspiratory pressure, were at a high level initially and did not change. It is concluded that distance running is safe and can increase the fitness of asthmatic children who are receiving adequate therapy.