Resp Flashcards
What is the hilum?
root of the lungs
What is the total adult lung volume?
3.5-8.5L
What is the difference between visceral pleura and parietal pleura?
visceral adheres to the lungs, pleural lines thoracic cavity
What is the main muscle of inspiration?
diaphragm. 80% of inspiration, controlled by the medulla via the phrenic nerve.
Where does the phrenic nerve exit?
C3, 4, 5
Describe the mechanical process of inspiration.
diaphragm contracts and flattens, pulls down the parietal pleura which decreases pressure and draws air into lungs. 80% of the work. the remaining 20% is done by accessory muscles such as external intercostals, actively moving rib cage up and out
Describe the process of expiration.
Not a passive process diaphragm relaxes, elastic recoil of the lungs, chest wall, and abdominal structures compress the lungs, exhalation longer than inspiration intercostals assist with inward movement of the ribs
What are the accessory muscles?
Scalene from neck to first two ribs, Sternoclediomastoid raises the sternum, and pectoral is major and minor
What are the conducting airways?
nasal cavity, nasopharynx, oropharynx (soft palate to hyoid), laryngopharynx
Characteristics of the trachea
smooth muscles, 11cm long, c shaped cartilagenous rings
Characteristics of the carina
Tracheal bifurcation site, right main stem bronchus, important anatomical landmark 2-3 cm above carina for ett placement
Characteristics of alveoli
primary site of gas exchange
Type 1 alveolar epithelial cells
90% functioning alveoli, gas exchange
type 2 alveolar epithelial cells
greater number vs type 1 cells, a supporting cell, produce , store and secrete surfactant
functions of surfactant
decrease surface tension, stabilizes alveoli, prevents collapse, increases lung compliance, eases WOB
What are the two vascular systems of the pulmonary alveoli.
pulmonary (pulmonary arteries, divides into right and left branches, receives venous blood from the right side of the heart) and bronchial( no gas exchange)
Bronchial circulation
functions to distribute blood to the airways, does not participate in gas exchange
Alveolar capillary membrane
5 layers thick no air in the blood no blood in the alveoli diffusion of oxygen and carbon dioxide Co2 is 20x faster than o2
What is the maximum peak pressure
35mmHg
The rate of diffusion is influenced by
thickness of the alveolar capillary membrane
surface area of the alveolar capillary membrane
diffusion coefficient of the gas
Why is CO2 faster than O2 to perfuse?
because it is more soluble
What can impair diffusion through AC membrane?
pulmonary edema, ARDS, pulmonary fibrosis Thickens alveolar membrane
Function of pulmonary lymphatic circulation
removal of foreign matter, cell debris, remove fluid to help keep alveoli clear, produce antibody and cell mediated immune response
eventually drains into the primary lymph nodes located at the hila
two forms of oxygen
bound to hemoglobin 97% oxyhemoglobin, 4 oxygen molecules, SaO2
plasma oxygen PaO2diffuses to the cellular level, which the stimulates haemoglobin to offload its oxygen.
What determines o2 delivery?
cardiac output 4-8l/min hemoglobin concentration oxygen binding capacity of the hemoglobin am ount of oxygen int he blood SaO2
how much oxygen is extracted every minute?
25% arterial oxygen every minute
what changes hemoglobin binding capacity
hypoxemia, altered rbc morphology
describe the relationship between extraction an consumption
once maximum extraction is reached, further increase in demand or decrease in supply leads to hypoxia
then anerobic metabolism and lactic acidosis
what are the three forms of CO2 in the blood
plasma 10%
hemoglobin 30%
bicarbonate 60% can accept or reject components to maintain acid base balance
What is the v in the vq balance
ventilation
movement of air into and out of alveolus
normal alveolar ventilation 4L/min
what is the q in the vq balance
perfusion
flow of blood thru a pulmonary capillary bed
normal alveolar perfusion 5L/minute
what is a normal vq
4:5 or 0.8
what problems can cause vq mismatch
ventilation, perfusion, or a combo
shunt
normal blood flow with decreased ventilation
anything that Impedes or blocks airflow
less than 0.8
dead space
ventilation without perfusion greater that 0.8
what are the normal and pathological percentages of wob
normal 3%
critical illness, 30% or more
how does the body compensate for vq mismatch?
hypoxic vasoconstriction around the alveoli with decreased oxygenation or bronchoconstriction in the presence of alveolar deadspace
Which two factors must be overcome for lung expansion?
elastic recoil, compliance, and resistance (impedance to airflow by conducting airways)
what causes increased wob
change in compliance
decreased chest wall compliance
increased airway resistance
decreased lung recoil
what are the key factors in lung compliance
lung volume- greatest at moderate volumes
tissue elastic recoil - aging decreases elastic tissue, increased compliance
pulmonary surfactant- decrease surface tension of alveoli, increased copmliance
elastic recoil
expiration
resistance key factors
under normal conditions, frictional interference to flow of air thru airways
adult icu increased resistance- leads to increased wob to move air in and out of the lungs
what might increase resistance
increased airway secretions
bronchospams
the smaller diameter, the increased resistance to airflow
changes in compliance
lungs are stiffer, difficult to inflate, increased effort or vent pressure to achieve volume
emphysema lungs are floppy, easy compliance
changes in resistance
increased effort to get air into lungs
What are the triad controllers of ventilation
controller - cns autonomic control
effector - muscles of ventilation
sensors - chemoreceptors( central and peripheral)
mechanoreceptor (chest and wall of lung)
components of the control of ventilation controllers
brainstem-medulla and pons, apneustic length of resp, pneumotaxic rate and depth
cerebral
cortex - voluntary ventilation to override autonomic control
the central and peripheral chemoreceptor control of ventilation
sensitive to changes in paCO2 and hydrogen ions
medulla and pons
not affected by paO2
CO2 is your drive to breathe
peripheral chemoreceptors respond to
paO2 primarily, but does respond to paCO2 and hydrogen.
any paO2 less than 60 increases ventilation
found in the bifurcation of common carotid, and above and below aortic arch
Dissociation curve
a relationship between paO2 and SaO2
dissolved oxygen and hemoglobin-bound oxygen
hemoglobin has a steady and predictable affinity for oxygen, occasionally events occur that change the affinity relationship
the curve shifts