Respiratory Infections and Vascular Rings

Recurrent respiratory infections after the first years of life are not easily related to vascular rings as the cause of these infections. Therefore six cases of older children are presented in whom a vascular ring was the cause of their respiratory problems. None of them ever had stridor or swallowing problems in early infancy, and recurrent respiratory infections occurred later in life as a symptom of a vascular ring. Unfamil iarity with this association caused a delay in diagnosis and treatment in two patients and persistent lung damage in one child. Five of the 6 children recovered well after operation. The diagnosis can be made at an early stage if close inspection of the outline of the trachea on the chest radiograph shows an impression from the right side

The effect of tissue elastic properties and surfactant on alveolar stability

This paper presents a novel mathematical model of alveoli, which simulates the effects of tissue elasticity and surfactant on the stability of human alveoli. The model incorporates a spherical approximation to the alveolar geometry, the hysteretic behavior of pulmonary surfactant and tissue elasticity. The model shows that the alveolus without surfactant and the elastic properties of the lung tissue are always at an unstable equilibrium, with the capability both to collapse irreversibly and to open with infinite volume when the alveolus has small opening radii. During normal tidal breathing, the alveolus can becomes stable, if surfactant is added. Including the passive effect of tissue elasticity stabilizes the alveolus, further allowing the alveoli to be stable, even for lung volumes below residual volume. The model is the first to describe the combined effects of tissue elasticity and surfactant on alveolar stability. The model may be used as an integrated part of a more comprehensive model of the respiratory system, since it can predict opening pressures of alveoli

Lung Imaging in Animal Models

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