Chronic radiographic lung changes in children with vertically transmitted HIV-1 infection.

OBJECTIVE: We prospectively studied children with and without maternally transmitted HIV-1 infection born to mothers infected with HIV-1 to determine the incidence of chronic radiographic lung changes (CRC) and to correlate these changes with clinical assessments. SUBJECTS AND METHODS: Between 1990 and 1997, we scored 3050 chest radiographs using a standardized form. Group I children (n = 201) were HIV-1-infected at enrollment. Group II children (n = 512) were enrolled prenatally or before 28 days postpartum and subsequently subdivided into group IIa (n = 86), children identified as HIV-1-infected; and group IIb (n = 426), those who were HIV-1-uninfected. CRC were defined as parenchymal consolidations or nodular disease lasting 3 months or more or increased bronchovascular markings or reticular densities lasting 6 months or more. Morbidity was assessed by CD4 counts, viral load, the presence of low oxygen saturation, wheezing, tachypnea, crackles, and clubbing. RESULTS: The cumulative incidence of chronic radiographic lung changes in HIV-1-infected children was 32.8% by 4 years old, with increased bronchovascular markings or reticular densities being most common. Chronic changes were associated with lower CD4 cell counts and higher viral loads. Resolution of these chronic changes was associated with decreasing CD4 cell counts but not with lower rates of clinical findings, viral load, or difference in survival. CONCLUSION: With increased survival, CRC are becoming more common. The resolution of these changes may indicate immunologic deterioration rather than clinical improvement.

Respiratory diseases in the first year of life in children born to HIV-1-infected women.

Our objective was to describe the respiratory complications, clinical findings, and chest radiographic changes in the first year of life in infected and uninfected children born to HIV-1-infected women. We prospectively followed a cohort of 600 infants born to HIV-1-infected women from birth to 12 months in a multicenter study. Of these, 93 infants (15.5%) were HIV-1-infected, 463 were uninfected, and 44 were of unknown status prior to death or loss to follow-up. The cumulative incidence ( +/- SE) of an initial pneumonia episode at 12 months was 24.1 +/- 4.7% in HIV-1-infected children compared to 1.4 +/- 0.6% in HIV-1-uninfected children (P < 0.001). The rate of Pneumocystis carinii pneumonia (PCP) was 9.5 per 100 child-years. The HIV-1 RNA load was not higher in the group that developed pneumonia in the first year vs. those who did not. Children who developed lower respiratory tract infections or PCP had increased rates of decline of CD4 cell counts during the first 6 months of life. Lower maternal CD4 cell counts were associated with higher rates of pneumonia, and upper and lower respiratory tract infections. The rates of upper respiratory tract infection and bronchiolitis/reactive airway disease in infected children were not significantly different than in uninfected children. At 12 months, significantly more HIV-1-infected than uninfected children had tachypnea and chest radiographs with nodular and reticular densities. There was no relationship between cytomegalovirus infection in the first year of life and radiographic changes or occurrences of pneumonia. In conclusion, despite a low incidence of PCP, rates of pneumonia remain high in HIV-infected children in the first year of life. The incidence of pneumonia in uninfected infants born to HIV-1-infected mothers is low. Chest X-ray abnormalities and tachypnea suggest that subacute disease is present in infected infants. Further follow-up is warranted to determine its nature.

Forced expiratory flow in uninfected infants and children born to HIV-infected mothers.

The Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV (P(2)C(2) HIV) Study is a multicenter study examining pulmonary and cardiac outcomes in offspring of HIV-infected mothers. This portion of the P(2)C(2) study tests the hypothesis that infants exposed to, but uninfected by, maternal HIV have normal maximal expiratory flow at functional residual capacity (V'max,(FRC)). We obtained 500 measurements of V'max,(FRC) by rapid thoracic compression in 285 children ages 6-30 mo in five U.S. centers. The data were compared with those from a healthy cohort of children described elsewhere. V'max,(FRC) rose with height in a linear relationship. The slope of the regression line in the exposed infants did not differ statistically from the slope in the comparison group, but the intercept was about 20% lower (p < 0.001). Height and weight were comparable in the two cohorts, and the differences between intercepts persisted after adjusting for birth weight and gestational age. However, maternal HIV infection cannot be assumed to be the cause as the cohorts may have differed in other variables, such as socioeconomic status and frequency of maternal smoking and drug use. Also, measurements varied substantially within and between our five centers, probably in part because of different racial and ethnic distributions. In summary, maternal HIV infection probably has only a modest effect, if any, on maximal expiratory flow at functional residual capacity in uninfected infants.

Thoracoabdominal compression and respiratory system compliance in HIV-infected infants.

The thoracoabdominal compression technique (TAC) is used to measure expiratory flow in infants. We investigated whether TAC caused a change in total thoracic compliance (Crs), resistance (Rrs), and respiratory system time constant (Trs). We studied 41 infants (mean age, 12.4 mo; SD, 7.5) from five centers studying longitudinal lung and cardiovascular function of infants from HIV-infected mothers. We measured Crs, Rrs, and Trs before and after TAC. Changes in Crs, Rrs, and Trs after TAC were not dependent on the length of time since TAC. Crs and Trs were reduced after TAC, p = 0.013 and p = 0.003, respectively, whereas Rrs did not change. When compared with uninfected infants, HIV-infected infants had a larger post-pre TAC percent decline in Crs (p = 0.003) and a post-pre TAC rise in mean Rrs (p = 0.03). These differences remained significant after adjusting for sex and age. When performing infant pulmonary function testing, TAC itself produces a temporary decrease in Crs and Trs that is more significant in infants at risk for abnormal lung volume or compliance. Therefore, the sequence of performing the infant lung function parameters should be the same each time the testing is repeated with TAC as the last parameter tested at each testing session.

Neurodevelopmental outcome at 3.5 years of age in children treated with extracorporeal life support: relationship to primary diagnosis.

OBJECTIVE: Recent studies suggest that for neonates treated with extracorporeal membrane oxygenation (ECMO), children with congenital diaphragmatic hernia (CDH) have poorer neurodevelopmental outcome than children with other diagnoses. We therefore analyzed the neurodevelopmental outcome at 3(1/2) years of age in 130 neonatal ECMO survivors with 6 different primary diagnoses. STUDY DESIGN: Children were assessed with the McCarthy Scales of Children's Abilities, Peabody Picture Vocabulary Test, Vineland Adaptive Behavior Scales, and a neurologic/physical examination; 12 factors related to infant characteristics and ECMO/hospital course including primary diagnosis were identified as independent variables. Dependent variables included test scores and 2 outcome categories: functional status (normal, risk, abnormal) and major neurologic sequelae (presence or absence). Statistical tools included chi-squared analysis, t test, analysis of variance, and discriminant and regression analysis. RESULTS: No significant differences were found between diagnostic groups in functional status or neurologic sequelae. Hospital days was the only variable consistently expressed in all analyses as having significant influence on the outcome measures. This was not a factor of the longer hospital days experienced by children with CDH. CONCLUSION: Neurodevelopmental outcome in neonatal ECMO is multifactorial. Although hospital days has the greatest association with outcome at age 3(1/2) years, these days likely reflect degree of illness and various complications that are independent of diagnostic group. Further study is required to determine which factors influencing the length of hospital stay may be the best predictor of long-term outcome.

Incidence of premature birth and neonatal respiratory disease in infants of HIV-positive mothers. The Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted Human Immunodeficiency Virus Infection Study Group.

OBJECTIVE: We sought to determine the prematurity rate in infants of HIV-positive mothers and to characterize the incidence and severity of neonatal respiratory disease in this population. STUDY DESIGN: From 1990 to 1994, 600 live-born infants of HIV-infected mothers were enrolled prenatally (73%) or postnatally (27%) from five U.S. centers. Logistic regression was used to determine the association of HIV status in the infant with prematurity (< or = 37 weeks), low birth weight (< or = 2.5 kg), and very low birth weight (< or = 1.5 kg) rates. The incidence of respiratory distress syndrome (RDS), bronchopulmonary dysplasia, meconium aspiration syndrome, and neonatal pneumonia was compared with anticipated rates for gestational age and birth weight. RESULTS: Very high rates of prematurity (19%), low birth weight (18.3%), and very low birth weight (3.3%) were found in the infants of HIV-positive mothers; and HIV infection in the infant was associated with younger gestational age. The overall incidence of RDS was 3% (17/600), which coincided with the anticipated rate, after adjusting for prematurity and birth weight. Only five infants (all < or = 1.5 kg) had bronchopulmonary dysplasia, and none required assisted ventilation beyond 14 days. Three term infants had mild meconium aspiration syndrome, and there were no cases of documented neonatal pneumonia. CONCLUSION: Infants born to HIV-positive mothers exhibited high prematurity and low birth weight rates, and the odds of prematurity were higher in infants who were infected with HIV. Despite the high incidence of prematurity and perinatal risk of this population, incidence and severity of neonatal respiratory disease were not higher than would be expected from available neonatal data in populations not exposed to HIV.

Measurement of lung volumes and pulmonary mechanics during weaning of newborn infants with intractable respiratory failure from extracorporeal membrane oxygenation.

Newborn infants with intractable respiratory failure who require extracorporeal membrane oxygenation (ECMO) experience diffuse pulmonary atelectasis shortly after initiation of ECMO. Atelectasis is likely due to the primary lung injury and the reduction of applied inspiratory ventilator pressure when the respirator settings are changed to the "rest settings." These pathophysiologic changes result in a decrease in lung compliance and lung volumes. We hypothesized that improving lung functions observed during ECMO and indicated by an increase in lung volumes will predict successful weaning from ECMO. Sixteen infants (mean +/- SEM: gestational age, 40.3 +/- 0.3 weeks; birth weight, 3.5 +/- 0.1 kg) with meconium aspiration syndrome (n = 13), sepsis (n = 2), and persistent pulmonary hypertension (n = 1) were studied. We measured passive respiratory system mechanics and lung volumes initially during full ECMO support (115 +/- 18 h on ECMO, Study I), and then within 24 h prior to weaning from ECMO (Study II). Respiratory system compliance (Crs), respiratory system resistance (Rrs), functional residual capacity (FRC), and tidal volume (VT) were measured. Prior to Study I lung volumes were too small to be detected. Crs increased between Study I and Study II (0.41 +/- 0.05 to 0.63 +/- 0.05 mL/cmH2O/kg, P < 0.05), and VT increased between Study I and Study II (5.6 +/- 0.6 to 10.4 +/- 0.8 mL/kg, P = 0.0005). FRC increased from 3.6 +/- 1.0 to 7.9 +/- 0.9 mL/kg (P = 0.0001). There was no change in Rrs (88 +/- 8 to 89 +/- 6 cm H2O/L/s, P = 0.9). The combination of Crs > 0.5 mL/cmH2O/kg and FRC > 5 mL/kg was a better predictor (P = 0.0002) of readiness to wean from ECMO than either Crs (> 0.5 mL/cmH2O/kg, P = 0.057) or FRC (> 5 mL/kg, P = 0.007) alone. The combination of FRC and Crs had a sensitivity of 73.3% and specificity of 100% for successful decannulation. We conclude that repeated measurements of FRC and Crs can assess lung recovery and may assist in establishing criteria for successful weaning from ECMO.

Pulmonary sequelae at six months following extracorporeal membrane oxygenation.

Mechanical assisted ventilation for neonatal respiratory failure is associated with residual lung disease. Because ECMO rests the lungs, it has been suggested that ECMO will prevent chronic lung disease in survivors. To determine whether or not ECMO survivors have evidence of pulmonary sequelae, we studied 19 infants who were treated with ECMO for neonatal respiratory failure. Ten infants still required supplemental oxygen or pulmonary medications or both to treat clinical lung disease during the first six months of life. Thoracic gas volume was normal. Pulmonary mechanics in ECMO survivors were compared with those of 13 preterm infants with BPD at similar age. We conclude that a significant proportion of ECMO survivors have residual abnormalities in pulmonary mechanics at 6 months of age. We speculate that neonatal lung injury due to meconium aspiration and other causes is a more important determinant of abnormal pulmonary sequelae than the method of treatment.

Extracorporeal membrane oxygenation in lambs through umbilical vessel perfusion: cardiac and hepatic complications.

Twin lambs were delivered by ceasarean section near term, aralyzed, sedated and randomly assigned to either mechanical ventilation or umbilical arteriovenous ECMO for 48 hours. Umbilical arteriovenous ECMO provided adequate gas exchange with minimal or no ventilation of the native lungs. However, at autopsy, animals treated with umbilical ECMO showed right heart dilation and liver necrosis or hemorrhage compared to their twins treated with mechanical ventilation.

Serial measurement of pulmonary mechanics assists in weaning from extracorporeal membrane oxygenation in neonates with respiratory failure.

Extracorporeal membrane oxygenation (ECMO) is a highly invasive therapy for intractable neonatal respiratory failure, and serious complications may occur with increasing duration of bypass. Weaning from bypass is empirical at present. Thus, there is a need to accurately predict when infants can be successfully decannulated. We hypothesized that pulmonary mechanics would reflect lung recovery and, therefore, predict successful weaning from ECMO. We measured pulmonary mechanics daily in 22 neonates, at gestational age of 37.8 +/- 0.6 weeks (SE) requiring ECMO for severe respiratory failure (oxygen index 66 +/- 6). Pulmonary resistance (Rpul), dynamic compliance (Cdyn), and tidal volume (VT) were measured. Rpul did not predict lung recovery. Cdyn within 24 hours of starting ECMO was 0.3 +/- 0.04 ml/cm H2O. Cdyn within 24 hours of weaning from ECMO was 1.2 +/- 0.09 ml/cm H2O (p less than 0.001). All 22 infants had Cdyn greater than 0.6 ml/cm H2O at the time of decannulation, but four infants (20 percent) with Cdyn less than 0.6 ml/cm H2O could not be weaned from ECMO within 20 hours (p less than 0.01). Thus, a minimum Cdyn of 0.6 ml/cm H2O is associated with successful weaning from ECMO. Cdyn of 0.8 ml/cm H2O provided better overall discrimination between those who could be successfully weaned from ECMO. We conclude that serial measurement of dynamic pulmonary compliance predicts successful weaning from ECMO.

Digital clubbing and pulmonary function abnormalities in children with lung disease.

Digital clubbing and pulmonary function tests were measured in children, adolescents, and adults with chronic lung diseases to determine pulmonary function correlates with a quantitative measure of clubbing. The group had a mean age of 13.8 +/- 6.0 (SD) years, mean PaO2 of 81 +/- 21 mm Hg, and mean FEV1 of 60% +/- 26% predicted. Digital clubbing was diagnosed in 43 cases when the distal phalangeal depth to interphalangeal depth (DPD/IPD) ratio, measured on a finger cast, was greater than or equal to 1 (greater than 3 SD above mean from 85 controls; no history of pulmonary disease; mean age, 14.8 +/- 7.6). The PaO2 of patients with digital clubbing was 69.4 +/- 2.1 (SEM) mm Hg compared with 88.3 +/- 1.3 mm Hg in those without digital clubbing (P less than 0.0001). Digital clubbing was present in 39 of the 84 (46%) hypoxic patients (PaO2 less than or equal to 88) but only four of the 78 (5%) normoxic patients (P less than 0.0001). The DPD/IPD ratio was negatively correlated with PaO2 in subjects with cystic fibrosis and interstitial fibrosis. Weak negative correlations were seen for all other subjects except asthmatics. Overall, the DPD/IPD ratio was significantly correlated with PaO2 (r = -0.53; P less than 0.0001). The DPD/IPD ratio was correlated with other lung function abnormalities (increased RV, decreased FEV1, and FEF25%-75%) only for the subjects with cystic fibrosis. We conclude that digital clubbing is associated with hypoxemia and airway obstruction. The relation is seen most clearly in subjects with cystic fibrosis, possibly reflecting the prolonged duration of hypoxemia. Digital clubbing is rarely seen in normoxic subjects.

Capillary plasma ammonia concentration in neonates receiving total parenteral nutrition. Comparison with arterial and venous concentrations.

Plasma ammonia concentration in neonates has routinely been determined using arterial or venous blood. Expected plasma ammonia values in capillary blood obtained by heelstick have not been determined. We compared ammonia levels in 20 sets of plasma from simultaneously drawn arterial, venous, and capillary blood in a group of neonates receiving total parenteral nutrition. Mean ammonia concentrations in venous (107 +/- 44) and capillary blood (112 +/- 33) were 45% and 51% higher, respectively, than corresponding arterial (74 +/- 22) values (P less than .001). Ammonia levels in blood obtained by venipuncture (Ven), however, did not correlate consistently with arterial (Art) values (r = .43; Art = 51 + 0.21 Ven; P greater than .05). In contrast, ammonia levels in capillary blood (Cap) correlated well with arterial values (r = .86; Art = 10.3 + 0.6Cap; P less than .001). Ammonia levels in neonates may be reliably interpreted using the latter regression equation when blood for analysis is obtained by a properly performed heelstick, allowing the preservation of arteries and veins, and sparing the infant from repetitive needle punctures. Ammonia levels in blood obtained by venipuncture do not adequately correlate with arterial values and therefore may be therapeutically misleading.

Long-term pulmonary sequelae of meconium aspiration syndrome.

To determine the incidence of long-term sequelae after meconium aspiration syndrome (MAS), we studied 11 children who had MAS at age 8.2 +/- 0.2 years (mean +/- SD) and nine healthy control subjects with pulmonary function and exercise stress tests. The MAS children had evidence of mild airway obstruction, hyperinflation, and increased closing volumes in comparison with control values. During graded exercise stress tests on a treadmill, MAS children achieved normal maximal oxygen consumption and anaerobic threshold without a significant fall in arterial oxygen saturation or increase in CO2 tension. Exercise-induced bronchospasm occurred in four (36%) MAS subjects but in none of the control subjects. We conclude that children surviving MAS have long-term pulmonary sequelae, including airway obstruction, hyperinflation, elevated closing volumes, and airway hyperreactivity; yet they achieve normal aerobic capacity. These findings are similar, although less severe, than those after prematurity and bronchopulmonary dysplasia.

Childhood sequelae of infant lung disease: exercise and pulmonary function abnormalities after bronchopulmonary dysplasia.

To determine the long-term pulmonary sequelae and effect on exercise tolerance of bronchopulmonary dysplasia (BPD), we studied 10 children at a mean age of 10.4 years, who had been born prematurely, survived respiratory distress syndrome, and subsequently developed BPD, and compared them with eight age-matched normal children born at term. Pulmonary function tests and graded exercise stress tests were performed. Residual volume, the ratio between residual volume and total lung capacity, vital capacity, forced expiratory volume in 1 second, forced expiratory flow between 25% and 75% of vital capacity, and maximal expiratory flows at 80%, 70%, and 60% of total lung capacity were all abnormal (P less than 0.02) in the children with BPD, compared with control values. Pre-exercise transcutaneous CO2 tension was higher (P less than 0.05) in the BPD group than in the control group. At maximal workload, tcPCO2 remained high in patients with BPD compared with control values (P less than 0.05). Arterial oxygen saturation at maximal workload fell below pre-exercise levels in the BPD group (P less than 0.05) but not in control children. There were no differences in maximal oxygen consumption between the BPD group and control children. Exercise-induced bronchospasm occurred in 50% of the BPD group, but not in the control group. We conclude that long-term survivors of BPD have evidence of airway obstruction, hyperinflation, and airway hyperreactivity, compared with a control group. Aerobic fitness was not significantly different in the BPD and control groups, but was achieved in the BPD group at the expense of a fall in SaO2 and a rise in tcPCO2.

Unexpected hearing loss in high-risk infants.

Eleven high-risk infants who had normal auditory brainstem responses at the time of discharge from the neonatal intensive care unit were found on follow-up between 13 and 48 months later to have significant sensorineural hearing loss. All 11 infants were the products of high-risk pregnancies and deliveries. Birth weights ranged from 890 to 3,700 g, but seven had birth weights of more than 1,500 g. Gestational ages ranged from 28 to 42 weeks. The length of hospitalization ranged from 45 to 167 days. All of the infants had respiratory distress, requiring prolonged mechanical ventilation with resultant chronic lung disease. All of the infants had received pancuronium, morphine, ampicillin, and gentamicin, and ten had also received furosemide and chlorothiazide. Other frequent clinical complications included abnormal CNS findings during the neonatal intensive care unit stay (ten infants), acidosis (pH less than 7.25) on the initial blood gas test (eight infants), and persistent fetal circulation in all seven infants with birth weights greater than 1,500 g. Developmentally, eight of nine children tested between 12 and 36 months of age were normal in all respects other than the hearing loss and the related language impairment. We conclude that infants who have been very ill in the newborn period, including term infants, may remain at risk for development of significant sensorineural hearing loss even though they have passed an initial auditory brainstem responses screening test in the newborn period.

Hypoxic and hypercapneic arousal responses and prediction of subsequent apnea in apnea of infancy.

Hypoxic and hypercapneic arousal responses from quiet sleep were tested in 56 infants with apnea of infancy (one or more episodes of cyanosis, limpness, and apnea requiring vigorous stimulation or resuscitation with no treatable cause; age 6.8 +/- 1.1 [SEM] months). Responses were compared with those of nine control infants ranging from 1 to 25 months of age. To assess hypercapneic arousal, the inspired PCO2 was rapidly increased during quiet sleep to 60 mm Hg or until arousal (restlessness, agitation, eye opening) occurred. All control infants and those with apnea of infancy aroused to hypercapnea, but control infants aroused at a lower inspired PCO2 (inspired PCO2 40.1 +/- 2.6 mm Hg) than those with apnea of infancy (inspired PCO2 46.9 +/- 1.5 mm Hg, P less than .05). To assess hypoxic arousal, the inspired PO2 was rapidly decreased during quiet sleep to 80 mm Hg or until arousal occurred. All control infants aroused to hypoxia (inspired PO2 78.3 +/- 2.1 mm Hg). However, only 38% of those with apnea of infancy aroused (inspired PO2 78.1 +/- 0.8 mm Hg), indicating an abnormality in recognition of hypoxia, or central brainstem response to hypoxia. During the 10.4 +/- 1.2 months of follow-up, there was a high incidence of subsequent apneas (greater than 20 seconds) during sleep at home in 50 apneic infants. Infants with abnormal hypoxic arousal responses had more severe subsequent apneas than those with normal hypoxic arousal responses (P less than .05).

Effect of oral diuretics on pulmonary mechanics in infants with chronic bronchopulmonary dysplasia: results of a double-blind crossover sequential trial.

In a randomized double-blind crossover trial with sequential analysis, the effects of oral diuretics were compared with the effects of placebo on pulmonary mechanics in ten infants with bronchopulmonary dysplasia (BPD). Pulmonary mechanics were measured before and at the end of a week of treatment with oral diuretics (chlorothiazide, 20 mg/kg/dose and spironolactone, 1.5 mg/kg/dose) given twice daily, or placebo. Mean airway resistance decreased 35.3 cm H2O/L/s, mean specific airway conductance increased 0.095 1/L/s/cm H2O, and mean dynamic pulmonary compliance increased 1.74 mL/cm H2O during treatment with diuretics (all P less than .001), but not during treatment with placebo. The infants' rate of weight gain decreased on the first three days of diuretic treatment, but was thereafter comparable with weight gain during treatment with placebo. Fluid intake was similar in infants receiving diuretics and placebo. But, infants receiving diuretics not only had significantly increased urine output, osmolal clearance, and potassium and phosphorus excretion, but these infants also retained less fluid, and, in addition, excreted less calcium than infants receiving placebo. It is concluded that oral diuretics improve lung function in infants with chronic bronchopulmonary dysplasia; however, potassium and phosphorus depletion are potential complications of treatment.

Effect of isoproterenol inhalation on airway resistance in chronic bronchopulmonary dysplasia.

The effects of isoproterenol inhalation on pulmonary mechanics in ten infants with bronchopulmonary dysplasia (BPD), aged 41 +/- 1 (SE) weeks postconception, with gestational age at birth 30 +/- 1 weeks, and birth weight 1,590 +/- 200 g were studied. The infants had: (1) hyaline membrane disease requiring mechanical ventilation in the first five days of life, (2) mechanical ventilation and/or FIo2 greater than 30% for at least 30 days, and (3) stage III or IV radiographic changes. Thoracic gas volume, airway resistance, and specific airway conductance were measured in an infant body pressure plethysmograph during quiet breathing. Dynamic pulmonary compliance was measured using an esophageal balloon. These infants with BPD had greater airway resistance, lower specific airway conductance, and lower dynamic pulmonary compliance than 16 normal control infants (age 40 +/- 1 weeks postconception). In the infants with BPD, measurements were obtained before and 1/2, 1, 2, and 6 hours after the administration of isoproterenol aerosol 0.1% inhalation or saline aerosol placebo, five breaths by slow inflation of the lungs with an anesthesia bag. Within 30 minutes after isoproterenol inhalation, airway resistance decreased 28% +/- 5% and specific airway conductance increased 53% +/- 15%. Thoracic gas volume and dynamic pulmonary compliance did not change. There were no changes following administration of the placebo. Isoproterenol inhalation is associated with rapid short-term improvement in airway resistance and specific airway conductance in infants with BPD.