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Early life is a key period that determines long-term health. Lung development in childhood predicts lung function attained in adulthood and morbidity and mortality across the life course. We aimed to assess the effect of early-life lower respiratory tract infection (LRTI) and associated risk factors on lung development from birth to school age in a South African birth cohort.

In the healthy animal lung, high-frequency oscillatory ventilation (HFOV) achieves effective ventilation at tidal volumes (VT) less than or equal to dead space while generating very small pressure fluctuations in the alveolar spaces (PA). We hypothesized that the respiratory mechanical parameters influence the magnitude of the intrapulmonary pressure fluctuations during HFOV. A computer model of the neonatal respiratory system was used to examine the independent effects of altering the compliance, nonlinear and linear resistance, and inertance of the respiratory system on VT, and cyclic intrapulmonary pressures under homogeneous and heterogeneous conditions. The impact of low compliance on the transmission of pressure from the airway opening to the trachea (Ptr/Pao) and alveolar compartment (PA/Pao) during HFOV was determined in a preterm lamb lung model. In the computer model, an increase in flow-dependent resistance to simulate changing the internal diameter of the tracheal tube from 4.0 mm to 2.5 mm halved the transmission of the pressure waveform to both the carina and the alveolar compartment. Increased peripheral resistance was associated with an increased Ptr/Paobut a reduction in PA/Pao. The PA/Paoalso decreased with increasing alveolar compartment compliance, a finding that was verified in the preterm lamb lung. There was an exponential decrease in the magnitude of PA1compared with PA2as the ratio of the time constants of the two parallel compartments (1/2) increased in the heterogeneous computer lung model. The transmission of driving pressure amplitude to both the proximal airways and lung tissue during HFOV is dependent on lung mechanics and may be greater in the poorly compliant lung than that observed previously in experiments on healthy animals.

In the healthy animal lung, high-frequency oscillatory ventilation (HFOV) achieves effective ventilation at tidal volumes (VT) less than or equal to dead space while generating very small pressure fluctuations in the alveolar spaces (?PA). We hypothesized that the respiratory mechanical parameters influence the magnitude of the intrapulmonary pressure fluctuations during HFOV. A computer model of the neonatal respiratory system was used to examine the independent effects of altering the compliance, nonlinear and linear resistance, and inertance of the respiratory system on VT, and cyclic intrapulmonary pressures under homogeneous and heterogeneous conditions. The impact of low compliance on the transmission of pressure from the airway opening to the trachea (?Ptr/?Pao) and alveolar compartment (?PA/?Pao) during HFOV was determined in a preterm lamb lung model. In the computer model, an increase in flow-dependent resistance to simulate changing the internal diameter of the tracheal tube from 4.0 mm to 2.5 mm halved the transmission of the pressure waveform to both the carina and the alveolar compartment. Increased peripheral resistance was associated with an increased ?Ptr/?Paobut a reduction in ?PA/?Pao. The ?PA/?Paoalso decreased with increasing alveolar compartment compliance, a finding that was verified in the preterm lamb lung. There was an exponential decrease in the magnitude of ?PA1compared with ?PA2as the ratio of the time constants of the two parallel compartments (t1/t2) increased in the heterogeneous computer lung model. The transmission of driving pressure amplitude to both the proximal airways and lung tissue during HFOV is dependent on lung mechanics and may be greater in the poorly compliant lung than that observed previously in experiments on healthy animals.