Mechanical ventilation 4

Mechanical ventilation 4

1. Mechanical Ventilation – 4 Fakhir Raza Haidri SIUT

2. Monitoring Respiratory Mechanics Acute Respiratory Distress Syndrome

3. Monitoring Respiratory Mechanics Two-Component Model the resistive component the elastic component

4. Elastance and Compliance P air = P R + P E P R = Q x R P E = V / C P air = {Q x R} + {V / C}

5. Peak Pressure It is the maximum pressure that is achieved in the respiratory cycle It is affected by the airway resistance, flow, volume and lung parenchyma elastance (stuffiness) The more the airway resistance, flow, volume or elastance, the more the Peak Pressure To know the pressure caused by elastance we must stop the inspiration, it will nullify the effect of resistance and flow

6. Plateau Pressure It is the measure of lung parenchymal properties at a given volume Measure of maximum alveolar pressure during respiratory cycle Measured by inspiratory pause maneuver Higher with increased tidal volume and decreased respiratory system compliance

7. Decreased peak pressure Decreased peak pressure during VCV In the setting of patient inspiratory efforts An endotracheal tube cuff leak Reasons of cuff leak Cuff underinflation Cephalad migration of the endotracheal tube, Inadvertent intratracheal placement of a gastric tube A Defective endotracheal tube cuff

8. Compliance The compliance of a system is defined as the change in volume that occurs per unit change in the pressure of the system Lung Compliance (C) = Change in Lung Volume (V) / Change in Transpulmonary Pressure {Alveolar Pressure ( Palv ) – Pleural Pressure (Ppl)}

9. Static Compliance It is the measure of compliance when the flow is hold (zero flow) It nullify the effect of resistance of airways and gives us the true picture of state of lung parenchyma C stat = Tidal Volume / { Pleatue – PEEP} Normal Static Compliance = 60 – 100ml /cm of H 2 O Decreased by Pneumonia, edema, atelectasis, pneumothorax, restrictive lung disease

10. Dynamic Compliance C dyn = Tidal Volume / {Peak Pressure – PEEP} Normal Static Compliance is 50-80ml / cm of H 2 O It is decreased in bronchospasm, mucus plugging, kinked tube or decreased static compliance