Module 2 Pulmonary Flashcards
rate and depth
ventilation
define ventilation
mechanical process where air is brought into and out of lungs
define respiration
gas exchange in lungs at alveolar/capilaries
ventilation rate
12 breaths per min
minute ventilation
volume of air inspired/expired per min in L
6L per min at rest
minute ventilation = (alveolar ventilation + dead space ventilation
)*RR
alveolar ventilation
volume of air that reaches the alveoli per min
dead space ventilation
volume of air that does not reach alveoli per min
how many seconds for inspiration? expiration?
2 / 3
respiratory center in brainstem
controls contraction and relaxation of respiratory muscles DRG and VRG in medulla and pneumotaxic and apneustic centers in pons
dorsal respiratory group
in medulla-
primary inspiratory- tells diaphragm to contract
sets automatic rhythm of breathing
gets infput from respiratory receptors (peripheral and central chemoreceptors, lung receptors etc) - this is a mechanism for blood co2 and o2 levels to influence rate of ventilation
example of respiratory receptors that influence DRG
peripheral and central chemoreceptors and lung receptors
co2 and o2 can influence the rate of ventilation
ventral respiratory group (VRG)
inspiratory and expiratory actions when ventilation is required- otherwise the lazy brother during rest
pheumotaxic and apneustic centers
in pons
modify DGR and VGR depth and rate inspired
what can override automatic ventilation control?
other parts of cns! ex. motor cortex (voluntary movement), hypothalamus and limbic system (stress/emotion)
3 types of lung receptors
irritant, stretch, j-receptors
what do lung receptors do?
send impulse to DRG to influence rate of ventilation
irritant receptors
rapidly adapting
in epithelium of conducting airway (usually larger airway)
stimulated by noxious gas, particles etc
cause cough reflex, gasping, initiate bronchoconstriction of air way and increased ventilation rate/depth (hyperpnea = increase breathing)
stretch receptors
slowly adapting receptors
in smooth muscle of conducting airways
“hering-breuer reflex inflation reflex” - prevents over inflation of lung
stimulated by stretch (adults extreme tidal volume in exercise, or copd) or (new borns to maintain ventilation)
sends a signal via CN 10 to b brain stem to inhibit inspiration by prolonging expiration time and decreasing volume of ventilation
Juxtapulmonary capillary receptors (J-receptor)
near alveolar septum of capillaries
stimulated by elevated pulmonary capillary pressure (edema, pul embolism etc)
acts on DRG to stimulate inspiration (rapid shallow breathing), also will decrease HR, and decrease BP
(extreme situation can cause opposite effect: apnea-slow breathing)
name the chemoreceptors and locations
central chemoreceptors in brainstem near respiratory centers
peripheral chemoreceptors in carotid and aortic bodies (carotid a. and aortic arch)
central chemoreceptors
indirectly monitor co2 of arteres by monitorying the pH of CSF (h+)
receptors detect changes in pH levels - co2 can cross bbb but h+ can not, so co2 bibnds with h20 to get h2co3 which breaks into h+ and hco3…. so if co2 rises in CSF, then H+levels increase (causing pH to decrease) which increases ventilation! (to blow off co2)
peripheral chemoreceptors
monitor o2- if o2 is less then 60mmHg = hypoxmia= causes an increase in ventilation via DRG
sensitive to changes in o2 mainly
must be less then 60 otherwise central chemoreceptor will kick in first
peripheral vs central chemoreceptor - their important roles
peripheral - acclimatization in altitude (chronic hypoemia)
central - acid base balance
describe the relationship between central and peripheral chemoreceptors
co2 and ph levels are primary influence on ventilation in health condition. ex) decrease o2 by hypoventilation increases co2 which decreases ph =increase in ventilation
(central is more sensitive then peripheral)
peripheral would kick in if o2 fell below 60 mmHg
if unhealthy: chronic hypoventilation makes central chemoreceptors less sensitive so the peripheral takes over and regulates ventilation
muscles related to inspiration
during rest: diaphragm and external intercostal
during exercise/disease: accessory muscles
(SCM/scalenes)
muscles related to expiration
during rest: none-elastic recoil!
during exercise / disease: accessory muscles (abdominal and internal intercostal muscles
What does surfactant do?
Surfactant lowers the surface tension to allow alveoli to expand
It has detergent like properties that separate the molecules allowing the alveoli to expand
Makes alveoli more compliant
Increased surface tension makes it difficult to expand the alveoli
What is the relationship to surfactant and alveoli diameter?
If the radius of alveoli decrease, then the surfactant makes it easier to distend the alveoli
as the radius of the alveoli increase it becomes more difficult to distend the alveoli
at low lung volumes it is easier to inflate the lungs tan it is at high volumes (after inspiration)
What happens if there is inadequate surfactant in the lungs?
Surface tension will increase and alveoli will collapse Decreased lung expansion Increased work of breathing Poor gas exchange ex: infant respiratory distress syndrome
What is the work of breathing (WOB) for a healthy individual?
Very low!
Pathology: work of breathing can increase significantly–chronic adaptation with hypertrophied accessory muscles (SCM/scalenes)
What is the atmospheric pressure (barometric pressure) at sea level?
760mmHg
decreases with elevation
What is partial pressure? What is the mathematical definition of partial pressure?
The pressure of individual gases within total air pressure
partial pressure = %concentration x total pressure of gas (air)
pao2=20.9%
partial pressure nitrogen=78.1%
paCo2=0.03%
What drives gas exchange (respiration)?
pressure gradients
higher O2 partial pressures in alveoli vs pulmonary capillaries (promote O2 to diffuse into blood)
higher blood stream co2 partial pressures in pulmonary capillaries vs alveoli (promote CO2 to diffuse into alveoli)
How does the air pressure within respiratory system compare to atmospheric pressure?
air pressure in respiratory system is less than atmospheric pressure
the respiratory tract warms and humidifies air which decreases total air pressure
What is the water vapor of respiratory tract?
47mmHg
To calculate total pressure in respiratory tract subtract the water vapor from atmospheric air (760mmHg-47mmHg) = 713mmHg
What is the percentage of O2 and CO2 in the trachea?
trachea=inspired air
713mmHgx20.9% = PO2 = 149mmHg
713mmHgx.03% = PCO2 = 0.21mmHg
What is the percentage of O2 and CO2 in the alveoli?
713mmHgx14.5% = PO2 = 103mmHg 713mmHgx5.5% = PCO2 = 39mmHg
Define tidal volume
500ml
volume of air inspired or expired with each normal breath
Define inspiratory reserve volume (IRV)
3000-3300ml
Volume of air that can be inspired over and above the tidal volume (used with exercise)
Define expiratory reserve volume (ERV)
1000-1200ml
volume of air that can be expired after the expiration of tidal volume
Define reserve volume or residual lung volume (RV)
1200ml
volume of air that remains in the lungs after maximal expiration
cannot be measured by spirometry
What is the forced vital capacity (FVC)
4500-5000ml
volume of air that can be forcible expired after maximal inspiration
TV + IRV + ERV = VC
What is the total lung capacity (TLC)?
5700-6200 ml
sum of all four lung volumes
VC+RV=TLC
cannot be measured by spirometry because it contains RV
What is forced expiratory volume (FEV1)
volume of air that’s measured during the first second of expiration
what is the FEV1 to FVC ratio?
the percent of FVC that can be expired in one second
normal FEV1/FCV = 70-90%
average = 85% (85% of fvc can be pused out of lungs in 1 second)
abnormal = 90%
fev1/fvc in obstructive disease: decreases (90% or no change)
What is minute ventilation? (ve)
volume of air expired in one minute
RR x TV
rr = respiration rate = 12 breaths/min
at rest minute vent = approximately 6 L/min (12x500ml)
can be increased by increasing rr or increasing tv
What is maximum minute ventilation (max ve)?
maximum volume of air moved in/out of lungs during maximal exercise
measured during maximum exercise stress test
healthy adult max minute ventilation will only be 60-70% of MVV (max voluntary vent)
this is a realistic measure of ventilation at maximal exercise, therefore ventilation is not a limiting factor in exercise
Disease: patient can reach max minute vent. before max HR so really is MVV
can go as high as 100-200L/min
What is maximum voluntary ventilation (mvv)
mvv = max volume of air that can be moved in and out of lungs in 60 seconds
tested by measured for 15 seconds and multiplying by 4
males: 140-180L/min, females 80-120L/min
can be as high as 230-240L/min in elite athlete
obstructive disease - 40% of expected normal
MVV is 35% higher than exercise ventilation (so vent. is not limiting factor in exercise)
this is not a functional measure..more theoretical
What is the forced expiratory flow rate (FEEF25-75%)?
aka MMEFR (maximum midexpiratory flow rate) essentially the middle portion of FVC
What is the relationship between exercise and lung volumes/capacities?
measures of lung volumes/capacities are poor predictors of athletic performance/fitness and much more useful in predicting disease/dysfunction
in disease-exercise may have beneficial effect on static and dynamic lung volumes
in healthy person-exercise training will have minimal-small effect on static dynamic lung volumes
