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Background: Maintenance of spontaneous breathing is advocated in mechanical ventilation. This study evaluates the effect of spontaneous breathing on regional lung characteristics during high-frequency oscillatory (HFO) ventilation in an animal model of mild lung injury. Methods: Lung injury was induced by lavage with normal saline in eight pigs (weight range 47-64 kg). HFO ventilation was applied, in runs of 30 min on paralyzed animals or on spontaneous breathing animals with a continuous fresh gas flow (CF) or a custom-made demand flow (DF) system. Electrical impedance tomography (EIT) was used to assess lung aeration and ventilation and the occurrence of hyperinflation. Results: End expiratory lung volume (EELV) decreased in all different HFO modalities. HFO, with spontaneous breathing maintained, showed preservation in lung volume in the dependent lung regions compared with paralyzed conditions. Comparing DF with paralyzed conditions, the center of ventilation was located at 50% and 51% (median, left and right lung) from anterior to posterior and at 45% and 46% respectively, P<0.05. Polynomial coefficients using a continuous flow were −0.02 (range −0.35 to 0.32) and −0.01 (−0.17 to 0.23) for CF and DF, respectively, P=0.01. Conclusions: This animal study demonstrates that spontaneous breathing during HFO ventilation preserves lung volume, and when combined with DF, improves ventilation of the dependent lung areas. No significant hyperinflation occurred on account of spontaneous breathing. These results underline the importance of maintaining spontaneous breathing during HFO ventilation and support efforts to optimize HFO ventilators to facilitate patients' spontaneous breathing. [ABSTRACT FROM AUTHOR]

Unlabelled: One of the major questions regarding long-term side effects of bronchiolitis by respiratory syncytial virus (RSV) is whether or not it induces asthma in later life. In this quantitative review, the data of 10 controlled studies are analysed.Methods: Follow-up studies of RSV bronchiolitis published between January 1978 and December 1998 were identified through a MEDLINE search. Studies were selected if (i) postnatal age at the time of the initial illness was below 12 mo, (ii) all children were hospitalized for RSV bronchiolitis, (iii) the diagnosis RSV was virologically confirmed in all cases, and (iv) a control group was used.Results: Six studies met all selection criteria. Up to 5 y of follow-up after RSV bronchiolitis in infancy, 40% of children reported wheezing as compared to only 11% in the control group (p <0.001). Between 5 and 10 y of follow-up 22% of the bronchiolitis group reported wheezing against 10% of the control group (p = 0.19). The incidence of recurrent wheezing as defined by three or more wheezing episodes also decreased with increasing years of follow-up: at 5 or more years of follow-up the difference between the RSV group and the control group was no longer significant. Furthermore, the presence of either a personal and/or a family history of either atopy and/or asthma did not differ between the two groups.Conclusions: Wheezing is common after RSV bronchiolitis in infancy. It may persist for > or = 5 y of follow-up. However, no significant difference between the RSV bronchiolitis and the control group was observed regarding recurrent wheezing by 5 y of follow-up. No significant difference between the RSV bronchiolitis and the control group were found regarding a personal history of atopy, a family history of atopy and/or asthma. Therefore it seems unlikely that RSV bronchiolitis is a cause of atopic asthma in later life. [ABSTRACT FROM AUTHOR]