• bulk airflow (refers to ventilation) progressively slows down as it moves through the conductiong airway
• by the terminal bronchiole there is no longer bulk flow, but gases move toward alveolar space by difusion

• some air may never get to alveoli and stay behind in the interior of the purely conducting airways and not participating in gas exchange
  • this fills the anatomic dead space

Define dead space ventilation

How do you determine anatomic dead space

• equivalent to individuals lean body weight in pounds
• usually about 150 mL

Define alveolar ventilation

part of tidal volume that reaches alveolar reservoir and can participate in gas exchange

• Va = Vt + Vd

• increase tidal volume
• increase respiratory frequency

• stored gas within alveoli that is only gradually replenished or emptied
  • prevents fluctuation in alveolar gas tensions with each tidal breath
• Va determines alveolar gas composition
• represents FRC

• anatomic dead space plus any terminal air space not being perfused by blood, thus not participating in gas exchange (indicitave of pathology)

want to determine amount of anatomic dead space

1. start inspiration from pure oxygen reservoir
2. start expiration into system and measure amount of nitrogen concentration (first bit of breath is probably gonna be oxygen)

Vd = Vt x {(PaCO2-PeCO2)/PaCO2}

• all CO2 expired come from gas exchange in alveoli
• practically no CO2 in inspired atmospheric air
• physiologic dead space does not contribute to expired CO2
• alveolar CO2 = arterial CO2

Vd/Vt = [(PaCO2-PeCO2)/PaCO2]

"a" represents artery

• Pt = P1 + P2 + P3

In a mix of gas, each gas contributes to total pressure in direct proportion to its concentration

• oxygen = 20.93%
• nitrogen = 79.03%
• carbon dioxide = 0.04%

P of water vapor at body temperature

P = 0.21 (760-47) = 150 mm Hg

PaO2 = FiO2 (Pb-Pwater) - PaCO2/RQ

"a" represents alveoli

• PaO2 = Fi (Pb-Pwater)-(Pblood/ventilation rate) 
• PaO2 = 0.21(760-47) - (40/0.8)
• PaO2 = 150 - 50
• PaO2 = 100

• alveolar ventilation determine alveolar pressure of carbon dioxide (inversely proportional relationship)
• if alveolar ventilation decreases, partial pressure of carbon dioxide in alveoli increases

• alveolar pressure of oxygen = 100 torr
• arterial pressure of oxygen = 90 torr

Equation for alveolar ventilation

Va = (VCO2 x K)/PaCO2

"a" is alveoli

hyperventilation leads to increase in partial pressure of oxygen in alveoli (less dilution of mixture coming into the trachea)

Fate of oxygen as it goes through the pathway

Function of upper airway in ventilation (nose and sinuses)

• filtration and impaction remove particles
• sneeze, cough, bronchospasm expel particles
• epithelial barriers and mucus limit particle penetration
• mucociliary escalator transports particles cephalad

• intersitital and alveolar macrophages
• phagocytosis of particulates, organisms, and debris
• microbicidal and tumoricidal activities
• degradation of organic particles

Function of larynx