Various doses (0-4.8 mg) of porcine surfactant were administered into the airways of immature newborn rabbits delivered at a gestational age of 26 days and 17-23 h. When the estimated concentration of exogenous surfactant in the lung liquid was less than or equal to 0.75 mg/ml (dose 0.6 mg), an average tidal volume of no more than a 3.0 ml/kg was obtained by mechanical ventilation with a peak insufflation pressure of 25 cm H2O, but when the estimated concentration was increased to 1.5 mg/ml (dose 1.2 mg), an average tidal volume of 17.7 ml/kg was attained, and the survival rate during a 30-min period of artificial ventilation improved significantly, from 14% to 53%. Even larger average tidal volumes, about 25 ml/kg, were recorded in animals with estimated surfactant concentrations of 3 and 6 mg/ml (doses 2.4 and 4.8 mg, respectively). In vitro observations revealed that the surface adsorption time of the surfactant suspension decreased non-linearly from 20 to 1 sec when the concentration was increased from 1 to 3 mg/ml. The minimum surface tension during cyclic film compression also decreased non-linearly from greater than 15 to less than 3 mN/m with the same increments in concentration. This led us to conclude that, under the present experimental conditions, the critical concentration of surfactant in fetal lung liquid at birth (about 3 mg/ml) is close to the concentration required in vitro for rapid adsorption and optimal dynamic surface properties.

Administration, Oral↗

PubMedDate not supplied

Optic disc findings in normal tension glaucoma.

One hundred thirty stereo photographs of optic discs in patients with normal tension glaucoma (NTG) were reviewed in order to identify characteristics of the three following types of NTG: focal ischemic, senile sclerotic, and generalized cup enlargement. Twenty patients in each group were selected. Focal ischemic patients were more frequently women, had a higher incidence of migraine, a relatively smaller disc size, and localized superior scotoma that often threatened fixation. Senile sclerotic patients were generally elderly, had a higher incidence of surgery under general anesthesia, had more ischemic heart disease or systemic hypertension, had a small rim area, and also had extensive peripapillary atrophy as well as combined diffuse and localized visual field defects. Generalized cup enlargement patients were younger, had a relatively larger disc size and a greater incidence of purely diffuse visual field loss. Results of our study suggest that the different characteristics of the groups are related to pathogenic mechanisms specific to each group.

Aged↗