The critical concentration of surfactant in fetal lung liquid at birth.
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.
Kobayashi
T
T
Department of Anesthesiology, School of Medicine, Kanazawa University, Japan.
Shido
A
A
Nitta
K
K
Inui
S
S
Ganzuka
M
M
Robertson
B
B
D000284:Administration, Oral; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D008168:Lung / Q000737:chemistry*; D011663:Pulmonary Surfactants / Q000008:administration & dosage / Q000032:analysis* / Q000502:physiology; D011817:Rabbits; D012119:Respiration / Q000187:drug effects / Q000502:physiology
D011663:Pulmonary Surfactants