Physical Aspects of Breathing Flashcards
purpose of conducting airways
- warm, humidify, and cleanse inhaled air
respiratory defense mechanisms
- anatomic
- mechanical
- immune
- general
anatomic respiratory defense mechanisms
- upper airway (nose)
- epiglottis/larynx
mechanical respiratory defense mechanisms
- mucociliary and cough clearance
immune respiratory defense mechanisms
- innate
- adaptive
innate immune respiratory defense mechanisms
- lysozyme
- lactoferrin
- defensins
- complement
adaptive immune respiratory defense mechanisms
- secretory IgA
- humoral antibody
- cellular immunity
general respiratory defense mechanisms
- alveolar macrophages
- inflammatory response
- anti-oxidants
- anti-proteases
why does the amount of O2 consumed differ from the CO2 produced?
- depends on the source of carbon in the diet
what do we use the alveolar gas equation for
- compare alveolar gas to blood gas
- determine how well the lungs are working
Dalton’s law
- total pressure of a mixture of gases is the sum of the pressures exerted by each gas
Henry’s law
- the amount of gas dissolved in the liquid is directly proportional to the partial pressure of the gas above the liquid
what happens with pulmonary capillary blood and alveolar gas in a healthy lung
- pulmonary capillary blood equilibrate with alveolar gas
PAO2 in the body
what does the A stand for
- 104 mmHg
- alveolar
PACO2 in the body
- 40 mmHg
branching pattern of the airways in the lung
- dichotomous branching patterns
how many generations of branching
- 23
which are the cartilaginous airways?
- bronchi
which are the non cartilaginous airways?
- bronchioles
- terminal bronchioles
what constitutes the conducting zone
- bronchi
- bronchiole
- terminal bronchiole
important component of respiratory bronchioles
- alveoli
what constitutes the respiratory zone
- respiratory bronchiole
- alveolar duct
- alveolar sac
capillaries in the conducting zone
- not close enough to inspired air for gas exchange to occur
capillaries in the respiratory zone
- close enough to inspired air for gas exchange to occur
what is anatomic dead space
- air in the conducting zone that cannot contribute to gas exchange
where do we find most vascularization in the lung?
- within the alveoli
importance of branching of airways in regard to cross sectional area
- aggregate cross-sectional area of the airways increases with each generation
expansion of the lung during inspiration is achieved by ______ in thoracic volume
- an increase in thoracic volume
muscles involved in quiet breathing during inspiration
- contraction and downward movement of diaphragm
- contraction of external intercostals
muscles involved in quiet breathing during expiration
- no active muscular contraction
- driven by elastic recoil of viscera, rib cage, and lung
muscle involved in forced expiration
- contraction of abdominal muscles and internal intercostals
- nonmuscular: lung elastic recoil
how do we express alveolar pressure
- cmH2O
alveolar pressure at end expiration
0 cm H2O
alveolar pressure during inspiration
importance of this
- 1 cm H2O
- pressure becomes more subatmospheric and creates a driving force for the inward flow of air
where is the intrapleural space location
- between the outer surface of the lung and the inner surface of the thoracic cavity
intrapleural pressure at end expiration
-5 cm H2O
intra pleural pressure during inspiration
-8 cm H2O
what pleura lines the lung
- visceral pleura
what pleura lines the chest cavity
- parietal pleura
pleural fluid originates as
- ultra filtrate from the chest wall systemic microcirculation
pleural fluid exits via
- via parietal pleural lymphatic stomata
why is there negative pressure in the pleural space?
- balance between lung wanting to collapse and chest wall wanting to spring out develops a suction (negative pressure) between them
sub atmospheric pressure in the pleural space at end-expiration is caused by
- tendency of the lung to collapse and ribs to spring outward
why does intrapleural pressure become more negative during inspiration?
- due to Boyle’s Law
- thoracic cavity volume is increased
- pressure drops when volume increases
what is transpulmonary pressure
how do we calculate it
usual value
- pressure difference across the surface of the lung, relative to alveolar pressure
- alveolar pressure - intrapleural pressure
- usually positive
importance of positive value of transpulmonary pressure
- holds lungs open at end-expiration (because intrapleural pressure is negative)
- when transpulmonary pressure increases during inspiration to overcome elastance of lung, lung inflates
compliance of the lung formula
- change in volume / change in pressure
elastance definition
- inverse of compliance
process of lung inflation during inspiration
- inspiratory muscles contract
- thoracic cavity expands
- intrapleural pressure becomes more negative
- transmural pressure gradient increases, creates subatmospheric alveolar pressure
- air flows inward and lung inflates
mechanical energy transferred where during end expiration
- from chest wall to lungs to keep lungs expanded
mechanical energy transferred where during end inspiration
- from lung to chest wall due to elastic recoil of lungs
why does expiration during a quiet tidal breath take longer than inspiration
- typically passive and not driven by active muscular contraction
- driven by elastic recoil of the lung
volume of a single inspiration or expiration
- tidal volume
maximal volume that can be inhaled following a normal inspiration
- inspiratory reserve volume
volume which can be forcibly expired from a normal expiration
- expiratory reserve volume
volume remaining after a maximal expiration
- residual volume
volume remaining in the lungs after a tidal expiration
- volume when the system is relaxed
how to calculate
- functional residual capacity
- ERV + RV
maximum volume of gas that can be inspired following a tidal expiration
- the most air you can inspire
how to calculate
- inspiratory capacity
- TV + IRV
maximal volume of gas which can be expired following a maximal inspiration
- the most air you can exhale
how to calculate
- vital capacity
- TV + IRV + ERV
sum of all four non overlapping lung volumes
how to calculate
- total lung capacity
- RV + ERV + TV + IRV
what do we use a body plethysmograph for
- measurement of the residual volume and functional residual capacity
what does functional residual capacity define
- mechanical equilibrium between the lung wanting to recoil inwards and ribs wanting to spring out at the end of a tidal breath when no active force is applied to the system
pressures in lung compared to pressures in vascular system
- low
- easier to move air than liquid
what will alveolar pressure be during expiration
- more positive
what will intrapleural pressure be during expiration
- less negative
