European journal of respiratory diseases. Supplement
-
Eur J Respir Dis Suppl · Jan 1987
Clinical TrialSurfactant replacement in the management of the neonatal respiratory distress syndrome.
Several recent reports have documented the efficacy of surfactants replacement therapy in the neonatal respiratory distress syndrome (RDS). The surfactants tested in these trials were obtained from animal lungs or human amniotic fluid. In general, such natural preparations seem to be superior to entirely synthetic surfactants, although promising results have recently been obtained in animal experiments with artificial surfactant based on isolated apoproteins and synthetic phospholipids. ⋯ This discrepancy may be due to maldistribution of the exogenous material, or to the rapid development of epithelial lesions in the immature lung, with leakage of surfactant-inhibiting proteins into the airspaces. A transient beneficial response to surfactant replacement may also be due to circulatory problems, especially reversal of the shunt through a patent ductus arteriosus, with overloading of the lung circulation leading to pulmonary oedema and recurrent respiratory failure. Additional, properly randomized clinical trials are required to evaluate the benefits and potential hazards of surfactant replacement therapy in neonatal RDS.
-
We examined the relationship between mucus rheology, depth of mucus layer, and clearance by simulated cough. A model trachea constructed of rigid plexiglass was lined with mucus simulants--borate-crosslinked locust bean gum gels. Their viscoelastic properties were determined by magnetic rheometry and expressed as mechanical impedance (dynamic stress/strain ratio or vectorial sum of elasticity and viscosity) and loss tangent (viscosity/elasticity ratio). ⋯ Mucus clearance was associated with transient wave formation in the lining layer. Thus the dependence on viscoelasticity is consistent with the observations that airflow-mucus interaction and wave formation are impeded by elasticity. The clearance vs. loss tangent relationship for cough is opposite to that found for ciliary clearance, suggesting a natural balance in viscosity and elasticity for mucus to be cleared by both mechanisms.
-
Excessive bronchial secretions within the airways can be transported by two-phase gas-liquid flow with airflow rates encountered during normal tidal breathing. The transport speed of secretions with this mechanism is as effective as the mucus clearance rate in normal subjects. The thickness of bronchial secretions required to effect two-phase gas-liquid flow is about 10% of the airways diameter which is not an unusual situation for patients who have bronchial hypersecretion. ⋯ This pattern can be achieved by imposing a controlled pattern of mechanical ventilation and is also probably the basis for the "huffing manoeuvre" taught by chest physiotherapists to clear airway secretions. Increased elasticity and decreased viscosity of secretions promote higher transport rates by two-phase gas-liquid flow. Conditions for two-phase gas-liquid flow during tidal breathing can be met at the 8th to 9th generation of the airways.
-
Eur J Respir Dis Suppl · Jan 1986
Comparative Study Clinical Trial Controlled Clinical TrialLong-term oxygen therapy vs. IPPB therapy in patients with COLD and respiratory insufficiency: survival and pulmonary hemodynamics.