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Advanced Study | Respiratory & Airway Part Three

Respiratory & Airway Part Three

Exchange and Transport of O2 and CO2
Red blood cells (RBCs) – transport O2 and CO2 with a protein called hemoglobin

FiO2 – concentration of O2 in inspired are. Pressure stays high in O2 (104) and low in CO2 (50) to make the O2 move across the alveolar/capillary membrane in to the blood stream until gas pressures are equal on both sides. CO2 levels vary inversely with ventilations.

O2 is transported in arterial blood in 2 ways:

  1. PO2 – physically dissolved in plasma (3%)
  2. SaO2 – chemically attached to hemoglobin

O2 diffuses from an area of greater concentration (the bloodstream) to an area of lower concentration (the tissues). Cells constantly use O2 in the Krebs cycle so a low PO2 (pressure) constantly exists.

Carbon Dioxide or PCO2 has a partial pressure of 50 mmHg. Co2 is carried to the lungs in three ways:

  1. PCO2 – dissolved in plasma (10%)
  2. Coupled with hemoglobin (20%)
  3. Combined with water as carbonic acid and its components (70%)

Nitrogen: Atmospheric air is 78% nitrogen. It serves no metabolic function, but is necessary to maintain inflation of body cavities that are gas filled.

Stimulus to Breathe: stimuli from brain needed for the pattern of inspiration/expiration.

Medulla Oblongata and the Pons are the resp. centers of the brain, control rate and depth

  • Medulla Oblongata: central chemo-receptors sense Hydrogen when CO2 combines with water (H2CO3) and then breaks down into H and HCO3. The Medulla is connected to the respiratory muscles by the vagus nerve
  • Pons contains pneumotaxic and apneustic areas that help regulate breathing movements
  • Aortic Arch and carotid body also have chemoreceptors that sense increased CO2, increased blood acid levels (H) and decreased blood O2 levels

Assessment: Airway is always the first step
Initial impression, level of consciousness/responsiveness

  • airway -patency
  • breathing/respiratory function
  • circulation

Pulse Oximetry: take on all patients as a vital sign. Take it BEFORE administering O2 and repeat it through assessment, treatment and transport. Test it on yourself first to see if it’s working. You can get false readings from:

  • CO/cyanide poisoning
  • Excessive ambient light on sensor probe
  • Patient movement
  • Hypotension (low perfusion)
  • Hypothermia
  • Vasoconstrictive drugs on board
  • Nail polish
  • Jaundice
  • COPD patients may be normally low
    • SaO2 reading of 95-99% is ideal
  • 91-94% mild hypoxemia 4-6 L O2 with nasal cannula
  • 85-90% moderate hypoxemia 15 L/m O2 with a non-rebreather
  • under 85% severe hypoxemia intubate or BVM with 15L/m O2

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