Factors Affecting Surfactant Responsiveness: Influence of mode of administration and ventilation, disease stage and type of surfactant

Historically, Kurt von Neergaard was the first to suggest that surface tension plays an important role in lung elasticity. He showed, in 1929, that the pressure necessary for fIlling the lung with liquid was less than half the pressure necessary for filling the lung WiOl air, and concluded that two-thirds to three-fourths of the elasticity of the lung was derived from interfacial forces. The problem with his discovery was that this paper was published in Gemlan and that, for 25 years, no scientists in the evolving fIeld really took note of this pnblication. In 1954, Macklin described the presence of a thin aqueous mucoid microfIlm, formed from secretion of the granular pneumocytes, on the pnlmonary alveolar walls and which is in constant slow movement toward the phagocytic pneumocytes and bronchioles. One year later, Pattie noticed the remarkable stability of foam and bubbles from lung edema and healthy lung cut. He assumed that the walls of these bubbles consists of surface-active material which must lower the surface tension to nearly zero. In 1957, Clements [was the fIrst to prove the direct evidence of surface active material in the lungs. He measured surface tension of a surface fIlm derived from the lung by using a Wilhelmy balance and demonstrated that the surface tension was not a constant value; when the surface was stretched the tension was relatively high (40 dynes/cm), but when the surface area was decreased the tension fell to 10 dynes/cm. He pointed out that such a reduction in surface tension during deflation in the lung would tend to stabilize the air spaces by permitting them to remain open at low lung volumes. Two years later, Avery and Mead demonstrated that lung extracts of very small premature infants and infants dying with hyaline membrane disease had much higher surface tension than normal lung extracts, due to a defIciency in surface active material. This was the first step towards extensive research on the surfactant system, and Fujiwara and colleagues, in 1980, were the fIrst to treat premature babies suffering from respiratory insufficiency with exogenous surfactant.

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