1. WHO Collaborative Centre for Training and Research in Newborn Care Ashok Deorari MD, FNNF,FAMS Department of Pediatrics All India Institute of Medical Sciences Science & Physiology behind C P A P

2. Definition Maintenance of an increased (positive) trans- pulmonary pressure during the inspiratory & expiratory phase of respiration, with the patient breathing spontaneously. Maintenance of an increased (positive) trans- pulmonary pressure during the inspiratory & expiratory phase of respiration, with the patient breathing spontaneously.

3. Physiology of CPAP Pulmonary Increases FRC Decreases V/Q mismatch Splints upper airway –  airway resistance  Tidal volume  Work of breathing Conserves surfactant  lung compliance

4. Effect of Ventilator on Preterm Lamb Lung No ventilation 24 h ventilation Limitations of premature lung 1.Underdeveloped architect to hold the lung open 2.Thicker and few septa so less SA for gas exchange Pinkerton KE, et al J Appl Physiol, 1994

5. nCPAP C V Preterm Lambs at 72 Hours Preterm Lambs at 72 Hours - Distal Airspace Wall Thickness -

8. Ventilator induced lung injury Biotrauma with tubeBiotrauma with tube AtelectotraumaAtelectotrauma

9. Ventilator induced lung injury BarotraumaBarotrauma VolutraumaVolutrauma

10. CPAP magic Opens the lung at FRC Opens the lung at FRC Keeps it open by minimal constant pressure –least baro and volutrauma Keeps it open by minimal constant pressure –least baro and volutrauma No ET tubes- no biotrauma No ET tubes- no biotrauma Pulmonary arterial pressure are least with improved blood flow, hence less V/Q mismatchPulmonary arterial pressure are least with improved blood flow, hence less V/Q mismatch

11. PVR Increases at Lung Volumes Below and Above FRC PVR Lung Volume

12. r = 3 T = 6 P = (2 x 6) / 3 P = 4 Law of LaPlace : P = 2T/r P : pressure T : surface tension r : radius

13. Larger alveolus r = 1.5 T = 3 P = (2 x 3) / 1.5 P = 4 Smaller alveolus r = 1 T = 3 P = (2 x 3) / 1 P = 6 CPAP Law of LaPlace : P = 2T/r P : pressure T : surface tension r : radius

14. Surface tension Imagine a human chain !! CPAP Surfactant

15. What did we learn ? 1. 1.CPAP causes less lung injury 2. 2.Give adequate CPAP to open lung at FRC 3. 3.Surfactant and CPAP have additive effect 4. 4.Maximum dividends if - Good delivery room care ; ANS for preterm labor -Acceptance by TEAM

16. The Best Ventilator… Least damage The Best Ventilator… Least damage