Mechanical Ventilation presentation

1. Mechanical Ventilation Dr. Shalini Garg

13. The mechanism of spontaneous ventilation and the resulting pressure waves. During inspiration P PL decreases to – 10 cm of H2O. During exhalation, P PL increases from -10 to -5 cm of H2O.

70. Contraindications for Heat Moisture Exchangers 1. In patients with thick, copious, or bloody secretions may accumulate on the HME and increase resistance to flow, both inspiratory and expiratory 2. When exhaled V T is less than 70% of inhaled V T 3. In patients with body temperatures of <32° C (hypothermia) 4.When spontaneous V E is >10 L/min 5. When an aerosolized medication must be given. 6. Very small V T delivery, in which case the HME may significantly increase V Dmech and compromise CO2 clearance Large V T delivery may compromise the ability of the HME to humidify inspired gases .

81. Equation of Motion Muscle pressure + Ventilator pressure = Elastic recoil pressure + Flow resistance pressure where Elastic recoil pressure = Elastance x Volume = Volume/Compliance(V/C) and Flow resistance pressure = Resistance x Flow = (R aw x Flow) The equation can be rewritten as follows: P mus + P TR = V/C + (R aw x Flow) P mus is the pressure generated by the muscles of venti­lation (muscle pressure). If these muscles are inactive, P mus = 0 cm H20. P TR is the transrespiratory pressure (P awo - P bs ); this is the pressure read on the ventilator gauge (manometer) during inspiration with positive pressure ventilation (i.e., the ventilator pressure).

82. V is the volume delivered, C is respiratory system compliance, V/C is the elastic recoil pressure, Raw is respiratory system resistance, and Flow is the gas flow during inspiration (Raw x Flow = Flow resistance). Because PTA = Raw x Flow and PA = V/C, substituting in the above equation results in P mus + P TR = P A + P TA where P A is the alveolar pressure and P TA is the transairway pressure.