12- Lung Volumes, Lung Ventilation, and Distribution of Inspired

Question 1

tidal volume

Answer 1

amount of air in a normal breath

Question 2

inspiration vs expiration

Answer 2

1. lungs are not completely filled during inspiration or completely emptied during expiration
2. inspiratory reserve is much larger than expiratory reserve

Question 3

functional residual capacity

Answer 3

volume of air in lungs at the end of passive expiration

Question 4

VE

Answer 4

total amount of air exiting the lungs in one minute (VT x f)

Question 5

VT

Answer 5

volume of a single breath

Question 6

f

Answer 6

breathing frequency

Question 7

VD

Answer 7

volume of airways (dead space)

KNOW THIS EQUATION
VD = VT x FACO2-FECO2/FACO2)

-FECO2 is the fractional concentration of CO2 in mixed expired air (all the air exhaled over a period of time)

Question 8

VA

Answer 8

volume of fresh atmospheric air reaching the lungs in one minute (VE = VD x f)

Question 9

FACO2 and FAO2

Answer 9

fractional concentrations of CO2 & O2 in the alveoli

• pressures of CO2 and O2 in the alveoli
• the pressure of O2 and CO2 measured at the mouth will not be constant throughout an exhalation

Question 10

when you inspire, what happens to the air

Answer 10

if you have 500 ml tidal volume, 150 ml remains in conducting airways and does not participate in gas exchange , only 350 ml enters alveoli

-the amount of fresh atmospheric air that reaches the alveoli with each inspiration will not equal the tidal volume

Question 11

PACO2 and PAO2 differ from

Answer 11

atmospheric PO2 and PCO2

Question 12

Dyspnea

Answer 12

breathing becomes painful (warning signal of something worse)

• air hunger, effort of breathing or chest tightness
• increased airway resistance
• Mismatch b/w efferent motor command to the respiratory muscles and afferent feedback from pulmonary and chest wall receptors, which signal the effectiveness of the motor command
• Insula receives afferents from projections from respiratory chemoreceptors and lung and chest wall mechanoreceptors.
• Dyspnea increases neural activity in the insula, cerebellum, thalamus and amygdala.
• normally you should be able to breathe out 90% of vital capacity in 1 second
  
  • if you have increased airway resistance then it will be something less than 90% (some sort of airway resistance problem)

Question 13

increased airway resistance diseases

Answer 13

1. bronchitis- due to inflammation of airway (medicine can help)
2. asthma- hyperactive smooth muscle of airway (medicine can help)
3. emphazema- loss of elasticity so airways become unstable and they are constricted (not much you can do to help)
   
   • chronic hypercapnea which is a much more long term problem

Question 14

alveolar hypoventilation

Answer 14

reduced ventilation without a corresponding decrease in metabolic rate resulting in inadequate atmospheric to alveolar gar exchange

-when breathing is decreased more than metabolic rate

Question 15

alveolar hyperventilation

Answer 15

increased ventilation without a corresponding increase in metabolic rate resulting in decreased PaCO2

-decrease in arterial pressure is sensed by chemoreceptors which causes hyperventilation, compensatory response

Question 16

distribution of inspired air is not uniform in upright posture. What are the two major factors that account for this?

Answer 16

1. Vertical gradient in PPL and PTP
   - pleural pressure is more negative at the top of the chest than at the bottom
2. Nonlinear lung compliance
   - the distribution of an inspiration depends on the lung volume the breath was initiated

-in the upright posture, at all lung volumes except total lung volume, the top of the lung is filled more than the bottom of the lung