Respiratory 2

    Cards (77)

    • Lung compliance
      How easily lung stretch (distensibility)
    • Compliance
      ∆V / ∆P - The change in lung volume from a change in distending pressure
    • High compliance

      • Large ∆V for a given ∆P
    • Low compliance

      • Small ∆V for a given ∆P
    • Gravity causes weight of lung (80% water) to pull down on alveoli
    • Gravity pulling down on lungs (think slinky) causes alveoli in apex to be more expanded
    • Compliance of the base > apex; More tidal volume goes to base
    • Pulmonary fibrosis
      • Collagen deposition due to lung injury - High elastic recoil
    • Emphysema
      • Disappearing lung tissue - Low elastic recoil
    • Surfactant
      1. Lowers surface tension - Increases compliance of lung making it easier to inflate<br>2. Keeps alveoli dry - Lowers surface tension, less inward pressure pulling fluid from capillaries
    • Boyle's Law: the pressure & volume of a gas are inversely related (P1V1 = P2V2)
    • Henry's Law: The amount of a gas that dissolves into a fluid is related to the solubility of the gas, the temperature, and the partial pressure of the gas
    • Dalton's Law: The total pressure of a gas mixture is equal to the sum of the pressures that each gas exerts independently
    • Inspiration begins
      Ambient air brought into airways warmed & humidified<br>Water vapor = a gas (PH2O = 47 mm Hg)<br>Partial pressure of other gases diluted
    • PO2 in a humidified mixture
      PO2 trachea = (PB-PH2O) x FO2
    • Total ventilation
      VE = VT x f
    • Both VT and f increase during max exercise, but depth of breathing increased more because of anatomical dead space
    • Anatomical dead space
      Part of inspired air that remains in conducting airways and is useless for gas exchange
    • Alveolar ventilation (VA)
      VA = (VT -VD) x f
    • Inverse relationship between VA and PaCO2
    • Systemic circulation: Left ventricle -> aorta -> rest of body
    • Pulmonary circulation: Right ventricle -> main pulmonary artery -> lungs
    • The lungs receive the entire right ventricular cardiac output
    • Bronchial circulation arises from the aorta and nourishes conducting airways (& parenchyma) up to terminal bronchioles
    • Blood from bronchial circulation (deoxygenated) mixes with O2-enriched blood in the pulmonary vein; contributes to the small A-a O2 difference
    • Pulmonary blood flow is high (5 L/min) but at low pressure
    • Pulmonary circulation
      • Low resistance - Pulmonary arteries shorter, in dilated state; pulmonary arterioles thin walled with less smooth muscle and lower resting tone, more distensible;; Enormous number of capillaries in a unique arrangement to create sheets of blood flowing past alveoli
    • 3 Factors That Alter Pulmonary Vascular Resistance
      • Changes in blood flow (perfusion) - Increased flow leads to recruitment and distention, decreasing resistance<br>2. Changes in lung volume - Resistance lowest at FRC<br>3. Changes in local O2 concentration - Hypoxia causes vasoconstriction
    • Pulmonary vasculature is NOT significantly regulated by the autonomic nervous system
    • Increase in cardiac output (e.g. exercise)

      Pulmonary blood flow increases, pulmonary vascular resistance decreases due to recruitment and distention of capillaries
    • Decrease in cardiac output (e.g. heart failure)

      Pulmonary blood flow decreases, pulmonary vascular resistance increases
    • Pulmonary vascular resistance is lowest at FRC and increases at lower and higher lung volumes
    • Hypoxia (low O2 in alveoli) and/or hypoxemia (low O2 in blood) trigger vasoconstriction in the pulmonary vasculature
    • In an upright person, blood flow is highest near the base and lowest near the apex of the lungs
    • Bulk flow
      How gas moves in airways from trachea to alveoli - Due to mass movement, occurs when there are differences in total pressure
    • Diffusion
      How gas moves from air to liquid, and liquid to air - Gases moving due to their individual partial pressure gradients
    • O2 in blood in 2 forms: physically dissolved and bound to hemoglobin
    • Dissolved O2 is directly proportional to PO2, but bound O2 does not contribute to PO2
    • Total O2 content in arterial blood is ~20 ml O2/100 ml blood
    • Partial pressure gradients (∆P)
      Major determinant of rate of diffusion
    See similar decks