Pulmonary Ventilation

Question 1

What are the muscles of inspiration? How do we breathe in?

Answer 1

external intercostals and diaphragm
- life the alveoli in ribs and decrease pressure by increasing volume
- air moves from high to low pressure

Question 2

What are the accessory inspiratory muscles? What are they used for?

Answer 2

used when taking the deepest breath possible

scalene muscles - neck
pectoralis minor - scapula
serrates anterior
sternocleidomastoid muscle

Question 3

What are the muscles of passive expiration? Active expiration?

Answer 3

no muscles for passive expiration - only relaxation of inspiration muscles

active - when blowing a balloon
- internal intercostals: pulls rubs down
- abdominal muscles - rectus abdominus, internal/external oblique, transverse: compresses abdomen and forces diaphragm higher

Question 4

Describe what happens during inspiration

Answer 4

1. external intercostal muscles contract - raise diaphragm
2. Thoracic V increases, intrathoracic P decreaes
3. Surface tension btw parietal and visceral pleura expand lungs to air in increased intrapulmonary V
4. air flows into lungs until intrapulmonary P and atm P are equal

Question 5

What happens when the external intercostal and the diaphragm contract? What about the internal intercostals? What nerves control these muscles?

Answer 5

external intercostals - v pattern that lifts ribs when it contracts
- increases diameter of ribs
- innervated by intercostal nerve

diaphragm - when contract, it increases the diameter of fibs from top to bottom
- innervated by phrenic nerve

forced exhalation - internal intercostals
- inverted V pattern that pulls ribs down
- innervated by intercostal nerve

Question 6

What is Boyle’s law?

Answer 6

PV = NRT
- P and V have inverse relationship at constant T

Question 7

At different elevations, what changes: gas percentiles or amount of gas particles?

Answer 7

gas percentiles remain the same at different elevations

relative amount of particles decreases as elevation increases

Question 8

Describe the relationship between alveolar, atmospheric and pleural pressure

Answer 8

atmospheric - air around the body, dependent on elevation, around 760 mmHg

alveolar - fluctuates with changes in thoracic P
- 759-761 mmHg

pleural - closed space in a healthy individual, can rise and fall but always less than alveolar
- creates a negative space that helps keep the lungs inflated/expanded
- 754-756 mmHg

Question 9

Describe the relationships between alveolar, atmospheric and pleural pressure during inspiration, exhalation ad holding breath.

Answer 9

Inspiration: Atm P > Alveolar P > Pleural P
Exhalation: Alveolar P > ATM P > Pleural P
Holding breath: Alveolar P = ATM P = no air movement

Pleural P will never be more than P atm or P alveolar as longs as its in tact

Question 10

What is transmural pressure?

Answer 10

the difference between intrapulmonary (alveolar) and intrapleural pressures

Question 11

What are the forces that act to collapse the lung?

Answer 11

Decreased pulmonary volume - increases alveolar pressure
inherent elasticity - allows lungs to recoil
surface tension of areolar fluid - alveoli tend to collapse

Question 12

What are the forces that act to expand the lungs?

Answer 12

increased pulmonary volume - decreases alveolar pressure
surface tension of pleural fluid - lung surfaces tend to adhere to parietal pleura

Question 13

What happens during a pneumothorax? Which side is more severe than the other?

Answer 13

puncture in pleural cavity forces air into pleural cavity
- with each breath in and out, air from the ATM and alveoli move into the pleura to equalize pressure
- with more air in the pleural space, it becomes increasingly hard for the lung to expand

tension pneumothorax - can push R lung towards L side of body
- compresses L lung, shifts trachea and heart towards L

Question 14

What is atelectasis?

Answer 14

collapse of the lung
can be caused by a pneumothorax

Question 15

What are the factors the influence pulmonary ventilation?

Answer 15

airway resistance, lung compliance, elasticity and surface tension

Question 16

What are the factors that influence airway resistance in pulmonary ventilation?

Answer 16

inverse relationship with diameter of bronchioles
- primary control over resistance to airflow

length of airway
- difficult for normal person to change length of airway

viscosity of air
- humidity and pollutants increase viscosity

Question 17

What are the ways the the parasympathetic and sympathetic nervous systems affects bronchiole diameter?

Answer 17

Parasympathetic innervation - vagus nerve - constrict
- ACh binds to muscarinic 2 receptors that constrict airway
- can be triggered by airborne irritants, cold air, PS stimulation, histamine

Sympatethic - dilates bronchioles
- epinephrine binds to B2 receptors to increase airflow

Question 18

Describe lung compliance. How is it measured?

Answer 18

ease of expansion measured by change in lung volume that occurs with specific change in alveolar pressure
- more lungs expand, greater the compliance

high compliance - less elastic recoil
low compliance - high elastic recoil

Question 19

What are the factors that lung compliance are dependent on? What reduces compliance?

Answer 19

dependent on - elasticity of lung tissue and thoracic wall

reduced by:
- reduction of natural lung resilience - disease, age
- blockage of bronchi/bronchioles - asthma, tumors
- impairment of thoracic cage flexibility
- increase surface tension of alveoli

Question 20

Describe what happens to lung compliance with emphysema and fibrosis?

Answer 20

emphysema - high compliance due to alveolar walls being destroyed
- decreased elasticity, difficult to breath out, increased lung volume

pulmonary fibrosis - increased CT in alveolar walls
- difficult to expand, decreased compliance
- increased distance from O2 from capillaries an alveoli
- decrease in gas exchange

Question 21

Describe what airway elasticity is and how it is related to surface tension

Answer 21

ability of lung to recoil during expiration
- alveoli walls have elastic fibers

surface tension helps collapse lungs
- H2O molecules on sides of alveoli helps with collapse
- helps alveoli resist stretching and recoils

Surfactant: lipoprotein nonpolar secretion that coats alveoli to help reduce H bonding and surface tension
- produced by alveolar Type II cells - highest # in alveoli

Question 22

What is infant respiratory distress syndrome and what causes it?

Answer 22

increased surface tension in the alveoli
- requires more pressure to open

smaller alveoli require more pressure to open
- surfactant is thicker in small alveoli

insufficient production of surfactant in newborns leads to IRDS

Question 23

Describe what happens to small alveoli during inhalation and exhalation

Answer 23

inhalation - as alveoli gets larger, surface tension increases due to dilution of surfactant

exhalation - alveoli decreases in size, surface tension decreases as the ratio of surfactant to alveolar surface is high

Question 24

How doe surfactant affect lung compliance?

Answer 24

increases lung compliance as surfaces forces are reduces

surfactant promotes alveolar stability
- prevents smaller alveoli from collapsing at low volumes

promotes dry alveoli
- collapsed alveoli tend to draw fluid into them from pulmonary capillaries

Question 25

Describe the following respiratory volumes: tidal V, inspiratory reserve V, expiratory reserve V, residual V
What is vital capacity?

Answer 25

tidal: amount of air moving in/out of lungs with each breath
- 500 mL

inspiratory reserve: difference btw max total inspiratory V minus max normal
- inspired forcibly beyond tidal volume
- 2100-3200 mL

expiratory reserve: difference between max total expiratory minus max normal
- use of accessory muscles to forcibly expire air after tidal expiration
- 1000-1200 mL

residual: amount of air still in lungs after breathing out as much as possible
- 1200 mL

vital capacity: TV + IRV + ERV = ~ 4800 mL
- total volume you can breath in and out

Question 26

Describe the forced expiratory volume test and what it measures.

Answer 26

take deepest breath possible and blood out as fast as you can
- measures vital capacity - FVC - forced vital capacity
- FEV1 - how much total vital capacity you can expire in 1 second

normal ~ 80% of to total VC
obstructive airway disease: <80% of total VC

Question 27

Describe what the minute ventilation tests

Answer 27

AKA pulmonary ventilation
total amount of gas that flows in/out of the respiratory tract in 1 minute
- increases with exercise

pulmonary ventilation = RR x tidal volume
average = 12 x 500 = 6000 mL/min

Question 28

What is the difference between obstructive pulmonary disorders and restrictive pulmonary disorders?

Answer 28

obstructive - decreased FEV1
- blockage of air flow - narrowed airway or dilated alveoli
- increased air resistance due to: increased residual volume, functional residual capacity or total lung capacity
- emphysema, chronic bronchitis

restrictive - decreased FVC
- loss of alveolar space/volume - part of alveoli blocked
- decreased lung volume: decreased residual volume, functional residual capacity, or total lung capacity
- pneumonia, pulmonary fibrosis or edema

Question 29

What is the alveolar ventilation rate? What is anatomical dead space?
What is total dead space?

Answer 29

respiration rate X (tidal volume - anatomical dead space)
anatomical dead space - air conducting conduits that do not contribute to gas exchange
- 150 mL

total dead space - anatomical dead space + any nonfunctional (due to pathology) exchange in volume