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Objective: To examine the effects of bronchiolitis on feeding efficiency and respiratory integration., Study Design: We studied 21 infants with bronchiolitis and 21 bottle-fed healthy infants who formed a comparison group. Repeat evaluations of half the bronchiolitis group were performed during recovery. During each feeding study we measured the duration and frequency of sucking, the frequency of single and multiple swallows, the respiratory rate, the postswallow respiratory direction, and the suck and swallow volumes., Results: The infants with bronchiolitis devoted significantly less time to sucking than their healthy peers (P <.05), and the mean suck volume was reduced. Although the frequency of swallowing was slightly higher, the volume of milk consumed per swallow was almost half the amount consumed by the comparison group (P <.01). Coordination of breathing with swallowing was also less effective (P <.01)., Conclusion: Although most aspects of feeding are less efficient during periods of respiratory illness, others are preserved or recover rapidly. Coordination of breathing during feeding is also significantly impaired.

Airway hyper-responsiveness, or hyper-reactivity, can be identified on clinical evaluation in a number of ways, including a history of wheezing, physician-diagnosed asthma, or the bronchial response to challenge with nonspecific stimuli such as methacholine or histamine. However, wheezing and the responses to these stimuli are not uniform within or across individuals, and in the general population there is a wide range of bronchial responsiveness that follows a normal distribution. Airway hyper-reactivity occurs in a number of settings, including acute viral bronchiolitis. Some, but not all, studies of children years after hospitalization during infancy for respiratory syncytial virus bronchiolitis or another lower respiratory tract infection demonstrate the presence of airway hyper-responsiveness. In contrast, infants studied who are <12 months of age do not have airway hyper-responsiveness after episodes of bronchiolitis. Discrepancies in the study results may reflect the bronchial challenge procedure used and the pulmonary function studies performed. Viral lower respiratory tract infections might alter immune responses to favor immunoglobulin E production, but the results of studies relating respiratory syncytial virus bronchiolitis with subsequent immunoglobulin E production again have been discrepant. Host and environmental factors such as exposure to tobacco smoke or a family history of atopy may be more important than viral lower respiratory tract infections as determinants of bronchial reactivity.

Objective: To determine whether abnormalities of cellular immunity are present and linked to early wheezing after bronchiolitis., Methods: We prospectively studied 26 infants hospitalized for a first episode of bronchiolitis and without any prior immune, cardiac, or respiratory disease. Blood was obtained at the time of enrollment and 5 months later for the assessment of the total cellular and differential counts, CD4+ (helper) and CD8+ (suppressor/cytotoxic) lymphocytes, and the activation markers CD23 (low-affinity immunoglobulin E receptor) and CD25 (interleukin-2 (IL-2) receptor). The cytokines interferon gamma (T-helper (TH) type-1 cytokine) and IL-4 (TH-2) were measured in plasma and in vitro after stimulation with IL-2 or with the house-dust mite (Dermatophagoides farinae) antigen. A daily log of episodes of wheezing was kept by parents after discharge., Results: We found an increase in blood eosinophils, an increased percentage of CD4+, CD25+, and CD23+ lymphocytes in subjects at 5 months compared with the time of bronchiolitis and with healthy subjects of the same age (p < 0.05). Plasma IL-4 levels, although not different from those of healthy subjects, also increased significantly. Peripheral blood lymphocytes from infants who wheezed produced more IL-4 in vitro, 5 months after bronchiolitis, in response to D. farinae antigen. In babies who wheezed, a positive correlation was found between the total number of days that wheezing occurred and the blood eosinophil count. Babies who wheezed more often (> 20 days) had more peripheral blood basophils and eosinophils, and peripheral blood lymphocytes obtained from these subjects at the time of bronchiolitis produced less interferon gamma on stimulation with IL-2., Conclusions: Bronchiolitis is followed by activation of cellular immunity, and early wheezing in infants is associated with a TH-2 response.

Measurements of thoracic gas volume, airways resistance, and total respiratory resistance were measured in a group of babies with acute severe bronchiolitis. Assessments were made at convalescence, three to four months later, and after 12 months. Clinical histories were also taken 12 months after the acute episode. Results at this time showed that 35% of the infants had coughing attacks, 50% episodes of wheezing, 50% had dry skin or eczema, and that over 75% had lung function abnormality.

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.