Lecture 32: Respiratory System Ii

Front 1

Barometric Pressure (PB)

Back 1

PB=760mmHg

Front 2

What contributes to PB

Back 2

Partial pressures of each gas contributes to PB

Front 3

Dalton's Law

Back 3

PB=PN2+PO2+PH2O+PCO2 (each gas contributes to the overall PB)

Front 4

Partial Pressure of O2

Back 4

PO2=PB x FO2=760mmHg x 0.2094=~160mmHg; FO2 is the fraction of oxygen in the atmosphere

Front 5

What must we account for in the trachea?

Back 5

Must account for water vapor pressure (47mmHg) in the trachea

Front 6

The PO2 in the alveolar=?

Back 6

The PO2 in the alveolar=PCO2 in the arterial blood

Front 7

What is PA(alveolar pressure) immediately prior to inhalation?

Back 7

PA=760mmHg immediately prior to inhalation

Front 8

In order for air to flow into the lungs, what must happen?

Back 8

In order for air to flow into the lungs= PA < atmospheric pressure

Front 9

What does diaphragmic contraction during inspiration lead to?

Back 9

Diaphragmic contraction increases the vertical dimensions of the thoracic cavity.

Front 10

What happens to the pleural cavity during inspiration?

Back 10

The Pleural cavity decreases which increases the volume of the lungs.

Front 11

During inspiration, air flows according to?

Back 11

Air flows according to Boyle's Law.

Front 12

Boyle's Law

Back 12

Pressure of the gas varies inversely with the volume. EX: if we cut volume in 1/2, the pressure doubles. P=1/V

Front 13

What moves air into and out of the lungs?

Back 13

Changes in alveolar pressure move air in and out of lungs.

Front 14

Describe the steps leading to when the alveolar pressure=atmospheric pressure.

Back 14

1. Inspiratory muscles contract
2. Thoracic cavity expands
3. Pleural pressure becomes more negative
4. Transpulmonary pressure increases
5. Lungs inflate
6. Alveolar pressure becomes subatmospheric
7. Air flows into lungs until alveolar pressure equals atmospheric pressure

Front 15

Minute Ventilation (V)

Back 15

Volume of air inhaled and exhaled per minute

Front 16

Expired Minute Ventilation (VE)

Back 16

Amount of air expired per minute; VE=VT x f;
500mL x 14 = 7L/min.

Front 17

Not all of tidal volume (VT) you being in participates in gas exchange, what happens to VT?

Back 17

Dead space ventilation in the coducting zone. VT is distributed between conducting and respiratory zones.

Front 18

If there is a tidal volume of 500mL. How much participates in gas exchange and how much remains in the conducting airways?

Back 18

350mL participates in gas exchange, and 150mL remain in the conducting airways (VD)

Front 19

What is the equation for Tidal Volume (VT)?

Back 19

VT= VD + VA (dead space volume and alveolar volume)

Front 20

What is VD a function of?

Back 20

VD is a function of body size. Crude estimation: 1mL/lb body weight

Front 21

Is all air new during inspiration?

Back 21

No, not all air is new, it is air that was in the conducting zone being pushed to the respiratory zone.

Front 22

Alveolar Dead space (VD)

Back 22

1. Air in alveoli without blood flow
2. Ventilation in excess blood flow

Front 23

Physiological dead space (VD)

Back 23

1. Physiological VD=anatomic VD (conducting airways) + alveolar VD
2. Each type of VD is the volume of inspired air that does not participate in gas exchange

Front 24

Alveolar Ventilation (VA)

Back 24

Amount of fresh air reaching the alveoli/min;
VA=(VT-VD) x f

Front 25

What is the most effective way to increase VA?

Back 25

Increasing the depth of breathing is the most effective way of increasing VA

Front 26

What is VA inversely related to?

Back 26

VA is inversely related to PaCO2 (if VA is halved, PACO2 will double

Front 27

What is an appropriate alveolar ventilation?

Back 27

Appropriate alveolar ventilation must accomplish two things: maintain partial pressure of oxygen so arterial oxygen (~100 mm Hg) and maintain partial pressure of CO2 (~40 mm Hg)—this is what we are trying to do with eucapnic (normal breathing).

Front 28

Hypoventilation

Back 28

decrease in alveolar ventilation

Front 29

Hyperventilation

Back 29

increased alveolar ventilation, leads to a fall in PACO2

Front 30

An increase in PaCO2 results in?

Back 30

hypoventilation

Front 31

A decrease in PaCO2 results in?

Back 31

hyperventilation

Front 32

Compliance of lungs:

Back 32

1. How much effort is required to stretch the lungs and chest wall
2. Delta V/Delta P

Front 33

High compliance of lungs

Back 33

easy expansion (takes little pressure)

Front 34

Low Compliance

Back 34

Expansion is resisted (takes a lot of pressure)

Front 35

What are the 2 factors which impact compliance?

Back 35

Elasticity and Surface Tension

Front 36

Elasticity

Back 36

Normal lungs are highly compliant and expand easily b/c the elastic fibers in lung tissue are easily stretched.

Front 37

Surface Tension

Back 37

1. A contractile force acting parallel to the surface
2. Force between molecules in a liquid pull the surface molecules toward the interior

Front 38

What decreases surface tension?

Back 38

surfactant in alveolar fluid decreases surface tension

Front 39

Name 4 pulmonary conditions in which causes decreased compliance of the lungs.

Back 39

1. Scar tissue (e.g., TB)--more difficult to get air in
2. Cause lung tissue to fill with fluid (pulmonary edema)--more difficult to get air in and diffusion problem with O2
3. Produce a deficiency in surfactant
4. Impede lung expansion in any way (e.g.,paralysis of intercostal muscles)

Front 40

When does increased lung compliance occur?

Back 40

Increased lung compliance occurs in emphysema due to destruction of elastic fibers in alveolar walls.

Front 41

What is the significance of low compliance in the lungs.

Back 41

It requires more work to inflate lungs. (takes more work to bring the air in)

Front 42

What is the significance of high compliance in the lungs? What happens to RV?

Back 42

More effort to force air out. RV increases over time, they can't get air out no matter how hard they try, which results in increased poressure of air to try and get in.

Front 43

What 2 things contribute to airway resistance?

Back 43

Turbulent flow and laminar flow contribute to airway resistance

Front 44

What ratio describes airway resistance?

Back 44

Ratio of driving pressure (DP) to airflow (V)

Front 45

What is the equation for total airway resistance (RAW)?

Back 45

For total airway resistance (RAW), the driving pressure is the pressure difference between atomosphere (pressure at mouth) and PA;
RAW(Pmouth-PA)/V

Front 46

Where is the major site of airway resistance?

Back 46

Large and medium airways down to ~7th generation of airway branches (very little resistance in the small airways)

Front 47

What increases resistance?

Back 47

Any condition that narrows or obstructs the airways increases resistance. Therefore more pressure is required to maintain the same airflow

Front 48

What 2 conditions increase airway resistance?

Back 48

COPD (emphysema and chronic bronchitis) and asthma (airways are obstructed or collapsed and RAW increases)

Front 49

What decreases airway resistance?

Back 49

During inspiration bronchi and small airways enlarge as their walls are pulled outward in all directions, thus decreasing RAW.

Front 50

What does bronchial smooth muscle tone affect?

Back 50

Bronchial smooth muscle tone affects airway caliber (gets smaller), and thus RAW

Front 51

What controls smmooth muscle from trachea to terminal bronchioles (conducting zone)?

Back 51

Smooth muscle from trachea to terminal bronchioles (conducting zone) are under autonomic control.

Front 52

What occurs during the parasympathetic stimulation of smooth muscle tone?

Back 52

Bronchial constriction and increased mucus secretion

Front 53

What occurs during the sympathetic stimulation of smooth muscle tone?

Back 53

Dilation and inhibition of secretion

Front 54

TRUE/FALSE. No energy is expended furing inspiration?

Back 54

FALSE. Energy is expended during inspiration.

Front 55

What is the percentage of energy that is expended during inspiration?

Back 55

1-5% of basal metabolism

Front 56

Name the 3 things that requires work during breathing?

Back 56

1. Expand thoracic cavity
2. Inflate the lungs
3. Overcome RAW

Front 57

What is the equation of work?

Back 57

Work= f x d
f= change in transpulmonary pressure
d=change in lung volume
W= P x delta(V)

Front 58

What happens to energy when a greater transpulmonary pressure is required to inflate the lungs?

Back 58

More energy is expended.