Quick A&P Review of Respiratory System:

1. Upper Respiratory Tract

Nose

• Divided into two passages (nares) by the septum.
• Internal passages are shaped into rolling projections called turbinates - function is to increase the surface area for warming and moistening air.
• With this humidification the body loses ~ 250 cc/day - insensible loss.

Pharynx:

• Nasopharynx
• adenoids - small mass of lymphatic tissue
• Oropharynx
• tonsils - also small mass of lymphatic tissue
• Laryngopharynx
• epiglottis - small flap of tissue that covers the larynx during swallowing

Larynx:

• vocal cords

Trachea:

• 5" cylindric tube bifurcates into the rt. and lt. Bronchi at the carina

2. Lower Respiratory Tract

Bronchi

• Main Stem Bronchi is made up of rt. and left main stem. The right main stem is shorter, wider and straighter than the lt.
• Potential problem for aspiration - with which lung?
• Rt. and Lt. main stem bronchi are the only lower airway structures not contained in the lungs
• Carina is located at the level of the angle of Louis
• Bronchioles - are encircled by smooth muscles that constrict and dilate in response to various stimuli.

Bronchoconstriction - Bronchodilation- Are terms used to refer to a decrease or increase in the diameter of the airways caused by contractions of these smooth muscles.

Everything above is consider only a conducting pathway for breathing and NO gas exchange occur - this pathway is termed the anatomic dead space. VT with normal adult is 500cc and ~ 150cc of this is VD Alveolar ducts

Alveoli:

- FUNCTIONAL UNIT OF THE LUNG ~ 300m alveoli in the lung Total volume of ~ 2500 ml Surface area for gas exchange that is about the size of a tennis court SURFACTANT

Oxygen-Hemoglobin Dissociation Curve: (describes the affinity of hemoglobin for oxygen).

O2 delivery to the tissue depends on:

• The amount of O2 delivered to the tissue
• The ease with which hemoglobin gives up O2 once it reaches the tissue

A. Upper flat portion of the curve fairly large changes in the PaO2 cause a small change in hemoglobin saturation.

Oxygen Toxicity - refers to alveolar injury caused by high oxygen concentrations > than 40 to 60%

B. Lower steep portion of the curve - as the hemoglobin becomes further desaturated, larger amt. of O2 are released for tissue use.

[Shift to left - blood picks up O2 more readily in the lungs but delivers O2 less readily to the tissues (seen in alkalosis, hypothermia, and with a decrease in PaCO2). Caused by: increased pH, decreased temperature, decreased PCO2]

{An example is seen in CABG's surgery... with hypothermia following surgery the pt may be given higher concentration of O2 immediately post op until the body temperature normalizes. Then as the curve shift back to the right the body picks up oxygen less rapidly in the lungs but delivers O2 more readily to the tissues.}

[Shift to right - blood picks up O2 less rapidly in the lungs but delivers O2 more readily to the tissues (seen in acidosis, hyperthermia, and when the PaCo2 is increased. Caused by: decreased pH, increased temperature, increased PCO2]

ABG's - determine oxygenation status and acid-base balance. ABG analysis includes measurement of the PaO2, PaCO2, acidity (pH), and bicarbonate (HCO3)

Normal ABG:

• pH 7.35-7.45
• PaO2 80-100 mm Hg
• PaCO2 35-45 mm Hg
• HCO3 22-26 mm Hg
• SaO2 > 95%