Pulmonary Ventilation Flashcards
What are the muscles of inspiration? How do we breathe in?
external intercostals and diaphragm
- life the alveoli in ribs and decrease pressure by increasing volume
- air moves from high to low pressure
What are the accessory inspiratory muscles? What are they used for?
used when taking the deepest breath possible
scalene muscles - neck
pectoralis minor - scapula
serrates anterior
sternocleidomastoid muscle
What are the muscles of passive expiration? Active expiration?
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
Describe what happens during inspiration
- external intercostal muscles contract - raise diaphragm
- Thoracic V increases, intrathoracic P decreaes
- Surface tension btw parietal and visceral pleura expand lungs to air in increased intrapulmonary V
- air flows into lungs until intrapulmonary P and atm P are equal
What happens when the external intercostal and the diaphragm contract? What about the internal intercostals? What nerves control these muscles?
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
What is Boyle’s law?
PV = NRT
- P and V have inverse relationship at constant T
At different elevations, what changes: gas percentiles or amount of gas particles?
gas percentiles remain the same at different elevations
relative amount of particles decreases as elevation increases
Describe the relationship between alveolar, atmospheric and pleural pressure
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
Describe the relationships between alveolar, atmospheric and pleural pressure during inspiration, exhalation ad holding breath.
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
What is transmural pressure?
the difference between intrapulmonary (alveolar) and intrapleural pressures
What are the forces that act to collapse the lung?
Decreased pulmonary volume - increases alveolar pressure
inherent elasticity - allows lungs to recoil
surface tension of areolar fluid - alveoli tend to collapse
What are the forces that act to expand the lungs?
increased pulmonary volume - decreases alveolar pressure
surface tension of pleural fluid - lung surfaces tend to adhere to parietal pleura
What happens during a pneumothorax? Which side is more severe than the other?
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
What is atelectasis?
collapse of the lung
can be caused by a pneumothorax
What are the factors the influence pulmonary ventilation?
airway resistance, lung compliance, elasticity and surface tension
What are the factors that influence airway resistance in pulmonary ventilation?
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
What are the ways the the parasympathetic and sympathetic nervous systems affects bronchiole diameter?
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
Describe lung compliance. How is it measured?
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
What are the factors that lung compliance are dependent on? What reduces compliance?
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
Describe what happens to lung compliance with emphysema and fibrosis?
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
Describe what airway elasticity is and how it is related to surface tension
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
What is infant respiratory distress syndrome and what causes it?
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
Describe what happens to small alveoli during inhalation and exhalation
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
How doe surfactant affect lung compliance?
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
Describe the following respiratory volumes: tidal V, inspiratory reserve V, expiratory reserve V, residual V
What is vital capacity?
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
Describe the forced expiratory volume test and what it measures.
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
Describe what the minute ventilation tests
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
What is the difference between obstructive pulmonary disorders and restrictive pulmonary disorders?
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
What is the alveolar ventilation rate? What is anatomical dead space?
What is total dead space?
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
