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After viral bronchiolitis at an early age, a chronic asthma-like syndrome develops in BN, but not F344, rats. We hypothesized that the BN strain is less effective at clearing virus from the involved tissues. Weanling BN and F344 rats were inoculated with Sendai virus, and lung and peribronchial lymph nodes were harvested from each strain at 5 to 84 days after infection; control tissues were obtained from noninfected rats. Lung viral titers were similar for the 2 strains, with no infectious virus detectable by day 10. However, viral RNA was detected consistently by means of RT-PCR analyses in lungs and lymph nodes of both strains from days 10 to 27 and was still present at day 84 in some of the tissues from each strain. In contrast, there were strain-related differences in immune responses because IL-13 levels remained increased in the lung secretions of BN rats at 4 weeks after inoculation. Thus although Sendai virus could persist for at least 3 months after an acute infection in rats, this did not differ with strain. The persistent increase in IL-13 suggests instead that the strain-related variability in virus-associated airway pathology might be determined by the host response to infection rather than by the intensity or duration of infection.

Respiratory syncitial virus (RSV) is a common cause of upper and lower respiratory tract infection in infants. An association between RSV bronchiolitis and cardiac arrhythmias has been described but is rare. A further case of an infant with supraventricular tachycardia in association with culture-positive respiratory syncitial virus bronchiolitis is reported. This case prompted a review of the two other cases of arrhythmia associated with RSV infection seen at this institution and a review of all other published cases.

Twenty-one children with normal hearts were studied during acute bronchiolitis. Doppler echocardiography showed tricuspid valve regurgitation in 11 patients, many of whom had evidence of raised pulmonary artery systolic pressure. Serial studies in those with severe infection showed that tricuspid regurgitation disappears with clinical improvement.

About 1% of infants are admitted to hospital with acute bronchiolitis; 85% of cases are caused by infection with Respiratory Syncytial Virus (RSV). The pathophysiological changes during the acute illness are inflammatory obstruction in the small airways with submucosal cellular infiltration, epithelial necrosis and mucous plugging; FRC increases and dynamic compliance falls. Failure to respond to bronchodilator drugs suggests that muscle spasm contributes relatively little to the airway narrowing. Affected infants become increasingly dyspnoeic and hypoxic for 3-4 days then spontaneously improve. After an attack of acute bronchiolitis up to 75% of children have recurrent lower respiratory tract symptoms, many continue to have hyperinflated lungs and bronchial hyperresponsiveness. In the majority, symptoms of cough and wheezing have subsided by the time they start school, but abnormalities of small airway function are detectable at least 13 years later. Children with a genetic predisposition to atopy do not appear to have an increased risk of developing bronchiolitis. Evidence of genetic predisposition to bronchial hyperresponsiveness in those with persistent wheezing is controversial. There is little to suggest that neonatal lung damage or an adverse home environment are important factors in determining susceptibility to post-bronchiolitis wheezing. IgE antibodies to RSV, and leukotriene C4, are found more frequently in the respiratory secretions of infants who wheeze during and after bronchiolitis than in those who do not. The possibility of viral-induced alteration of the immune response at the time of infection needs further investigation.

An unusually large number of infants (82) were admitted to Stanford University Hospital from November 1, 1983, through May 31, 1985, with a diagnosis of bronchiolitis requiring oxygen therapy. A larger percentage of these infants (17/82 = 21%) than generally expected required mechanical ventilation for respiratory failure. Fourteen infants had respiratory syncytial virus (RSV) infections, and three had parainfluenza virus infections. Ten patients had respiratory difficulties as neonates. The mechanical ventilation of the children requiring respiratory assistance was characterized by high minute ventilation with high tidal volumes (15 to 20 ml/kg) and slow respiratory rates (16 to 22 breaths/min). Peak inspiratory pressure averaged (mean +/- SD) 35 +/- 6 cm H2O in the RSV group and 34 +/- 6 cm H2O in the parainfluenza group. The mean number of days on the ventilator was 9.7 +/- 3.1 for the RSV group and 8.3 +/- 2.9 for the parainfluenza group. All were extubated within 17 days of presentation and discharged within 28 days. The complications encountered included pneumothorax and acute pulmonary hypertension.

We reviewed the clinical progress of 81 children as part of a prospective study three and a half years after admission to hospital with acute viral bronchiolitis in infancy. Fifty six (69%) reported episodes of lower respiratory symptoms continuing over the preceding year, 25 (31%) had symptoms lasting for longer than two weeks on two or more occasions, 14 (17%) had symptoms for more than 100 days, and six (7%) required readmission to hospital with acute respiratory illness. Two years previously, these percentages had been 82%, 36%, 33%, and 13% respectively. Forty six (57%) children were said to be improving or to have become asymptomatic, but eight (10%) were deteriorating. There was no difference in the personal or family history of atopy, nor in the rate of skin test positivity between those with and without continuing symptoms, suggesting that atopy does not play an important role in the persistence of symptoms. Less than half the symptomatic children had received bronchodilator treatment during the preceding 12 months.

A 9-year-old with immunodeficiency developed a severe, diffuse respiratory illness that necessitated mechanical ventilation. Open lung biopsy revealed Respiratory Syncytial Virus (RSV) as the sole pathogen. RSV detection should be included in the differential diagnosis of diffuse lung disease in an immunocompromised child.

A prospective follow-up of 48 infants hospitalized with respiratory syncytial virus bronchiolitis in the first year of life revealed that 44 of these infants had symptoms suggestive of asthma in the 5 years following their initial illness (cumulative prevalence 92%). Symptoms became less frequent and less troublesome during the follow-up period. Thirty-five of these children visited the laboratory for clinical examination, pulmonary function testing, and histamine challenge. Twenty-five children were believed to have clinical evidence of asthma at the time of the laboratory visit (point prevalence 71%). Five children were unable to perform pulmonary function tests; 25 of the remaining 30 (67%) had a positive histamine challenge test. No relationship could be demonstrated between a clinical diagnosis of asthma, a family history of atopy, and the results of histamine challenge testing. These results question the relationship between the results of bronchial provocation tests and clinical asthma in this age group.

Four infants in whom excessive secretion of antidiuretic hormone was associated with pulmonary infections are reported. Severe hyponatraemia was noted in 3 of them; in the fourth, fluid restriction may have prevented this complication.

Severe respiratory disease associated with bovine respiratory syncytial virus (BRSV) infection has been identified in dairy cattle in New York State. The cases identified occurred in dairy calves and heifers. The disease was characterized in 4 animals by pathologic changes including interstitial pneumonia, necrotizing bronchiolitis with multinucleated syncytial epithelial cells and interstitial emphysema. BRSV antigen was demonstrated in lung samples or was isolated in tissue culture in all 4 cases. A retrospective survey of 6279 bovine diagnostic accessions between 1977 and 1982 revealed 66 cases of interstitial pneumonia, often with concurrent bronchiolitis. In this 5 year period, only 1 case in 1981 had interstitial pneumonia and bronchiolitis with pathologic features consistent with BRSV infection. It is concluded that pathogenic BRSV has entered New York State and that it is contributing to clinical respiratory disease in dairy cattle.

To determine whether the magnitude of the respiratory syncytial virus (RSV)-specific IgE response at the time of an episode of RSV bronchiolitis in infancy accurately predicts the development of subsequent wheezing episodes, we observed 38 infants prospectively from the time of an episode of infantile bronchiolitis through 48 months of age. Peak RSV-IgE titers were measured at the time of the bronchiolitis episode using an ELISA procedure. Notation was made of both the number of subsequent wheezing episodes reported by parents and the number documented by a physician. Subsequent wheezing was documented by a physician in 20% of infants who did not develop an RSV-IgE response at the time of the bronchiolitis episode and in 70% of those with the highest responses (P less than 0.025). These results suggest that the magnitude of the RSV-IgE response at the time of RSV bronchiolitis is a useful prognostic indicator for recurrent wheezing.

Spontaneous pneumothorax is an uncommon complication of bronchiolitis due to respiratory syncytial virus. Bilateral spontaneous pneumothorax in an infant with respiratory syncytial virus bronchiolitis has not been previously reported. We report the case of a four-month-old infant who presented in respiratory distress owing to respiratory syncytial virus bronchiolitis with bilateral pneumothoraces. The infant improved with evacuation of air from the chest.

Airway reactivity and the effects of bronchodilators in infants are controversial. We studied the response to bronchodilator treatment in 14 mechanically ventilated infants (mean age, 2.74 months; range, 0.6-5.9) in respiratory failure caused by respiratory syncytial virus (RSV)-associated bronchiolitis. Sixteen infants without lung disease, undergoing elective surgery, provided normal values. Maximum expiratory deflation flow-volume (DFV) curves were produced by manual inflation of the lungs with an anesthesia bag to a predetermined static airway pressure followed by rapid deflation with a negative airway pressure before and after administration of bronchodilator. At baseline, the bronchiolitis group had a forced vital capacity (FVC) of 34.5 +/- 3.6 ml/kg compared with 41.8 +/- 1.5 ml/kg in the normal group; maximum expiratory flow rate at 25% of FVC (MEF25) was 10.2 +/- 2.0 ml/kg/s compared with 27.3 +/- 2.0 ml/kg/s in the normal group. The clinical and radiologic impression was severe lower airway obstruction and air trapping. After administration of bronchodilator, FVC did not increase significantly, but MEF25isov increased by over 30% in 13 of 14 infants. Mean MEF25 increased by 148 +/- 43.2% to 21.7 +/- 3.9 ml/kg/s (P less than 0.02). These findings indicate that during the acute phase of severe RSV-positive bronchiolitis most infants have airway reactivity that responds positively to bronchodilator treatment.