Summary
Highlights
This module introduces surfactant agents, differentiating them from mucokinetic agents. Surfactants are a replacement therapy, targeting the alveoli to prevent collapse and improve gas exchange, unlike mucokinetic agents which target airway mucus.
A case of a premature baby born at 28 weeks with respiratory distress due to immature lungs and lack of surfactant is presented. This highlights why surfactant therapy is crucial for such cases.
The alveoli, crucial for gas exchange, contain Type 1 pneumocytes for gas exchange and Type 2 pneumocytes for surfactant production and regeneration of Type 1 cells. Surfactant creates a layer between air and water in the alveoli, reducing surface tension.
Surface tension in the alveoli pulls them inward, leading to collapse (atelectasis) and Respiratory Distress Syndrome (RDS) without adequate surfactant. LaPlace's Law explains the relationship between pressure, surface tension, and alveolar radius, demonstrating how surfactant reduces the pressure needed to keep alveoli open.
Exogenous surfactants are used for prophylactic treatment (prevention) in high-risk premature infants and rescue treatment (therapy) for infants already suffering from RDS. They improve lung compliance and ease of breathing.
Pulmonary surfactant is mainly composed of lipids (especially DPPC, responsible for lowering surface tension) and proteins (SP-A, B, C, D) that aid in spreading and recycling. Surfactant is synthesized in Type 2 alveolar cells, stored in lamellar bodies, released upon lung inflation, and largely recycled by the body.
There are three classifications: natural or modified natural (animal-derived, containing phospholipids and proteins, most common), synthetic (man-made, lacking proteins, safer but less effective), and genetically engineered (future combination of synthetic and natural).
Detailed comparison of 'Cervanta' (Beractant), 'Infasurf' (Calfactant), and 'Curosurf' (Poractant) covering their source, protein content, timing of use (prophylaxis vs. rescue), dosing, and administration techniques including the use of aliquots for even distribution.
Surfactant therapy is not without risks. Complications include airway occlusion, desaturation, bradycardia (procedure-related), hyperoxia, hypocapnia/overventilation, and pulmonary hemorrhage (effect-related). These require careful monitoring and immediate management.
Future applications extend beyond neonatal RDS to conditions like ARDS, MAS, and pneumonia. Developments include aerosolized delivery systems for non-invasive administration and genetically engineered surfactants for improved effectiveness and safety.
Respiratory therapists must assess patients before, during, and after surfactant administration. This includes monitoring for RDS signs, risk factors, cardiac rhythm, oxygenation, carbon dioxide levels, lung mechanics, and overall patient condition to ensure safety and adjust therapy if needed.