Oscillometric measurements of respiratory system resistance (Rrs) in infants are usually made via the nasal pathways, which not only significantly contribute to overall Rrs, but also introduce marked flow (V')-dependent changes. We employed intrabreath oscillometry in casts of the upper airways constructed from head CT images of 46 infants. We examined oscillometric nasal resistance (Rn) in upper airway casts with no respiratory flow (R0), and the effect of varying V' on Rn by simulating tidal breathing. A characteristic nonlinear relationship was found between Rn and V', exhibiting segmental linearity and a prominent breakpoint (V'bp) after log-log transformation. V'bp was linearly related to the preceeding value of end-expiratory volume acceleration (V"eE; on average r2=0.96, p<0.001). Rn depended on V', and R at end-expiration (ReE) and showed a strong dependence on V"eE in every cast (r2=0.994, p<001) with considerable inter-individual variability. The intercept of the linear regression of ReE vs. V"eE was found to be a close estimate of R0. These findings were utilised in re-analysed Rrs data acquired in vivo in a small group of infants (n=15). Using a graphical method to estimate R0 from ReE, we found a relative contribution of V'-dependent nonlinearity to total resistance of up to 33%. In conclusion, we propose a method for correcting the acceleration-dependent non-linearity error in ReE. This correction can be adapted to estimate R0 from a single intrabreath oscillometric measurement, which would reduce the masking effects of the upper airways on the changes in the intrathoracic resistance.

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Furunculosis as a presentation of PVL MRSA infection Repetitive abcedations and furuncles in young patients are unusual. When occurring in an immunocompetent subject, PVL-SA infection should be considered. In this case report, the history of a female patient with severe PVL-SA infection is reported. An overview of the diagnosis and treatment recommendations is given.

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