Terms Used in the Physiology of the Ventilated Patient

  • Airway resistance:
    • Refers to the resistive forces encountered during the:
      • Mechanical respiratory cycle
    • The normal airway resistance is:
      • ≤ 5 cmH2O
  • Lung compliance:
    • Refers to the:
      • Elasticity of the lungs, or
        • The ease with which they stretch and expand:
          • To accommodate a change:
            • In volume or pressure
    • Lungs with a low compliance, or high elastic recoil:
      • Tend to have difficulty with the inhalation process, and are colloquially referred to as:
        • Stiff” lungs:
          • An example of poor compliance would be:
            • A patient with a restrictive lung disease, such as:
              • Pulmonary fibrosis
    • In contrast:
      • Highly compliant lungs, or lungs with a low elastic recoil:
        • Tend to have more difficulty during the exhalation process:
          • As seen in obstructive lung diseases
  • Atelectasis:
    • Is a complete or partial collapse:
      • Of the entire lung or area (lobe) of the lung:
        • It occurs when the tiny air sacs (alveoli) within the lung:
          • Become deflated or possibly filled with alveolar fluid
  • Derecruitment:
    • Is the loss of gas exchange surface area:
      • Due to atelectasis
    • Derecruitment is one of the most common causes of:
      • Gradual hypoxemia in intubated patients and can be minimized by:
      • Increasing PEEP
  • Recruitment:
    • Is the restoration of gas exchange surface area:
      • By applying pressure:
        • To reopen collapsed or atelectatic areas of the lung
  • Predicted Body Weight:
    • Is the weight that should be used in determining ventilator settings:
      • Never use actual body weight
    • Lung volumes are determined largely by:
      • Gender and height, and therefore, these two factors are used to determine predicted body weight:
        • The formula for men is:
          • PBW (kg) = 50 + 2.3 (height (in) – 60) and
        • The formula for women is:
          • PBW (kg) = 45.5 + 2.3 (height (in) – 60)

#Arrangoiz #Surgeon #Teacher

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