Changing the way you learn

The Background For Mechanical Ventilation

Transpulmonary pressure= Alveolar pressure- intrapleural pressure
1. It must be a positive value, so that the alveoli remain open
  1. Usually a value of +4mmHg
For ventilation (FLOW) to occur,: the alveolar volume increases (due to work of dia phragm/ext intercostals), alveolar pressure decreases (Boyle's law) to below atmospheric pressure
1. There is AIR FLOW. This air flow will continue to occur, UNTIL there is no longer a pressure difference between the atmospheric pressure and alveolar pressure
  1. Flow= Delta P/ Resistance
    1. However, if there is a change in pressure (ie between alveoli and atmosphere BUT there is high airway resistance, then flow (aka ventilation) will still be compromised
      1. So what can be done????
        Well, if we are assisting the patient, only one of two things::
        Increase the pressure outside the body (ie going to the alveoli)
        What's this??
        Positive pressure ventilation!! (invasive or noninvasive)
        Decrease the pressure in the alveoli relative to atmospheric pressure (this was attempted with the IRON LUNG, used for POLIO victims
      2. The patient will initially try to WORK HARDER, diaphragm contracts more, accessory muscles chime in to create a more negative intrapleural pressure, thus increasing the gradient between alveolar pressure and atmospheric pressure., BUT EVENTUALLY WILL BECOME TIRED

The Background For Mechanical Ventilation

	Created by Wen Eze over 9 years ago