OUTLINE 16

I. PRINCIPLE SUBDIVISIONS OF
THE RESPIRATORY SYSTEM

A. Upper division

1.

2.

3.

B. Lower division

1.

2.

3.

4.

5.

6.

7.

8.

9.


II. BASIC FUNCTIONS OF THE UPPER DIVISION

A. Conduction

B. Cleansing

C. Humidification

D. Olfactory Support

E. Voice

 
III. BASIC FUNCTIONS OF THE LOWER DIVISION
A. Gas exchange
with the Blood

B. Metabolic

1. Acid-base
balance



2. Angiotensin II
Activation



3. Immunity:
alveolar macrophages


OVERVIEW: PROCESSES INVOLVED IN THE RESPIRATORY SYSTEM

1.


2.


3.

4.


5. 
IV. MECHANICS OF PULMONARY VENTILATION
(Inspiration and Expiration)

A. Gas Laws

1. Boyle's law: VP = K (T constant)
Where V: Volume of a container
P: Pressure of gas in the container
K: Constant


a. V x P = K




b. Also states: V 1 ; This underlies breathing
P

1.Increase vol of the container (lungs), Pressure in lungs decreases, Air moves in down a pressure gradient
2.Decrease vol of the container(lungs), gas pressure in lungs increases, Air moves out down a pressure gradient

2. Dalton's Law; Pt = P1 + P2 + P3, etc.

a. Total pressure of a gas = sum of all the partial pressures of the gases in the mixture

b. Patm = PN + PO + Pother

= 78% + 21% + 1%

B. Structural Relationships: Lungs, Pleura, Thoracic Wall














Pressures (Refer to previous figure)

A. Atmospheric (PATM)
1. At sea level: 760 mm Hg (torr)
2. Used as a baseline
a. Pressures above atmospheric: ie, +5 cm
b. Pressures below atmospheric: ie, -5 cm


B. Intrapulmonic, intra-alveolar or alveolar (PA)
1. Pressure inside the lungs (alveoli)

2. Starts at PATM
a. Lungs expand: increase vol so decrease in pressure below atmospheric
b. Air flows into the lungs
c. Flow stops when PA returns to PATM

3. During expiration, lungs recoil so vol decreases and pressure increases
a. Air flows out until return to PATM

4. Graph: Intrapulmonic (PA) pressure vs. time











C. Pleural pressure, Intrapleural or interpleural (PPL)
1. Pressure in the pleural space between lung and chest wall
2. Always less than PATM
3. During inspiration; -5 to -8
4. Graph: Changes in Intrapleural Pressure






D. Transpulmonary pressure (PTM)
1. Pressure gradient across the lungs
a. Holds the lungs open
PTM = PA -PPL or PTM = 0 - -5 = 5


b. Pushes lungs open during inflation as it increases
PTM = O - -8 = 8


2. With a pneumothorax, air is introduced into the pleural space
a. PPL goes to 0 so PTM = 0 - 0 = 0
1) The pressure holding the lung open is 0
2) The lung collapses




















C. Muscles of Respiration
1. Inspiratory:
a. Diaphragm
b. External intercostals
c. scalenes

2. Expiratory: passive
a. Forced expiration
1. Internal intercostals
2. Abdominal muscles

D. The Respiratory Cycle

1. Inspiration
a. Diaphragm flattens; sternum and ribs- up and out
b. Thoracic cavity expands
1. Ppl decreases (-5 to -8), Ptm increases to 8
c. Lungs are pushed open by increased Ptm
1. As lung vol increases, gas pressure decreases
2. PA decreases below Patm
d. Air flows in along the gradient until PA returns to Patm

2. Expiration: Passive
a. Diaphragm, scalenes and external intercostals relax
1. Folds back into the thoracic cavity
2. Rib cage drops: PPL returns to -5; Ptm drops to 5

b. Lungs recoil
1.As lung vol decreases, gas pressure increases
2. PA exceeds Patm

c. Air flows out along the gradiet until pressure returns to Patm
 
*** GRAPHS ***



1. PPL











2. Ptm











3. PA











4. Volume of air
In the lungs






V. Compliance
A. Definition: V/ P
1. Change in vol in response to
change in pressure
a. CL = 8/2 = 4

b. Takes more pressure (2 to 4)
to reach the same volume:
Compliance has decreased
CL = 8/4 = 2

2. General ideas
a. With maximal inspiration, CL decreases

b. With aging, lung CL decreases causing a decrease in IRV

B. Factors Influencing Compliance

1. Pulmonary and Thoracic Elasticity

a. Increase in elasticity, Decrease in compliance

b. Decrease, increases compliance: occurs with the second stage of emphysema


2. Surface Tension-Alveolar Fluid-Surfactanct

a. Alveoli tiny, collapse due to surface tension

b. Surfactant decreases surface tension so alveoli remain open even during exhalation

c. Without surfactant, increase in surface tension,
alveoli collapse (Infant respiratory distress syndrome)
1.Takes more pressure to reach same vol:(decrease in CL)




3. Airway resistance
a. Increases with obstructive disorders and causes a decrease in dynamic compliance while static compliance stays the same

 
STATIC VS. DYNAMIC COMPLIANCE
Definitions:
1. Static CL
a. Stepwise analysis of change in vol vs. change in pressure

2. Dynamic CL
a. Analysis of change in vol vs. change in pressure while air is moving


NORMAL COPD









Obstruction to airflow decreases dynamic compliance in COPD


4. Pneumothorax
a. Definition
1. Pneumothorax: atm air enters the pleural fluid, lungs collapse
a. PPL (-5 to 0); PTM = 0; lungs collapse

b. Requires increased pressure to move air into the lungs (if possible) so CL greatly decreases







IV. Obstructive versus restrictive disorders