Abstract

Measurements of the resistance, time constant, and compliance of the respiratory system were made in 25 mechanically ventilated, preterm babies on 32 occasions, using the single breath technique. Patients were classified according to the level of respiratory resistance by reference to a population of 36 babies studied over the first two days of life before airway secretions had become apparent. There was a highly significant fall in both the resistance and time constant measurements after tracheobronchial suction or lavage for infants whose pretreatment values of resistance were greater than the reference mean. When tracheobronchial toilet was effective in removing secretions the changes in resistance and time constant values were again significant. No changes in compliance values were noted. Severe but clinically inapparent mucous obstruction of the airways was revealed in two infants by a progressively rising respiratory system resistance during continuous monitoring. The need for and efficacy of tracheobronchial suction and lavage could be determined by such techniques for monitoring the resistance of the respiratory system during mechanical ventilation.