Surfactant

Surfactant, a complex substance containing specific proteins and phospholipids, is essential for gas exchange in the lungs. Research shows that surfactant not only lowers surface tension, but also plays a role in host defense. Surfactant replacement therapy is a cornerstone in the treatment of respiratory distress syndrome in premature infants. New information on endogenous surfactant composition including surfactant apoproteins has led to advances in the surfactant replacement products currently available. Because of the success of surfactant deficiency treatment in neonates, surfactant replacement therapy has been studied in both the pediatric and adult population for the treatment of other respiratory disorders. This article describes the composition, metabolism, and function of endogenous surfactant and other uses of surfactant replacement therapies in neonates.     

Optimal intensity for respiratory muscle endurance training in patients with spinal cord injury.

OBJECTIVE: Respiratory muscle endurance of able-bodied persons, assessed by normocapnic hyperpnoea at 70% of their maximal voluntary ventilation, usually ranges from 10 to 20 minutes. The aim of this study was to determine the level of ventilation that patients with paraplegia and tetraplegia can sustain for 10-20 minutes to later be used as the guideline for respiratory muscle endurance training. DESIGN: Pilot study; cross-over setting. SUBJECTS: Two groups, 8 patients with paraplegia and 6 with tetraplegia. METHODS: Respiratory muscle endurance tests were performed at 3 different intensities of normocapnic hyperpnoea, i.e. 20%, 40% and 60% maximal voluntary ventilation. Subjects performed partial re-breathing from a bag to assure normocapnia. Respiratory endurance was separately analysed for patients with paraplegia and tetraplegia. RESULTS: Mean respiratory endurance times were 46.0, 18.9 and 4.2 minutes at 20%, 40% and 60% maximal voluntary ventilation in patients with tetraplegia and 51.8, 38.8 and 12.2 minutes in patients with paraplegia. The duration differed significantly at 60% maximal voluntary ventilation between the groups. CONCLUSION: Minute ventilation to perform respiratory muscle endurance training can be set at around 40% of maximal voluntary ventilation for patients with tetraplegia and around 60% of maximal voluntary ventilation for patients with paraplegia, as these levels can be sustained for 10-20 minutes.