Normal Physiology 4 - Ventilation Flashcards
to what can we compare the diaphragm
To a piston : Descends and flattens when it contracts leading to an increase in lung volume
What kind of movement of the ribs do we see with the lifting of the lower chest wall created by the contraction of the diaphragm?
the bucket handle motion of the ribs
3 accessory muscles for respiration
scalenes, sternocleidomastoids and trapezius
What does the sternocleidomastoid
elevates sternum and clavicle
What does the trapezius
stabilizes and moves the scapula
What does the scalene muscles
elevate upper ribs
What is the role of the accessory muscles?
its a backup system for the primary respiratory muscles
During exercise, what helps the inspiration
abdominal muscles: rectus abdominis, transverse abdominis, internal/external oblique muscles
thoracic muscles: internal/innermost intercostal muscles
how many generations of airways in the respiratory system
23 generations
- first 16 act as conduits only
- after 16 generation start to have alveoli
what is the tidal volume, and what is the volume
the volume of gas inspired and expired during each normal breath, typically around 500ml at rest
what is the minute ventilation
the total volume of fresh gas drawn into the lungs each minute
formula for minute ventilation
f= normal respiratory rate environ 12-20 /minute
Vt = normal tidal volume, 350-500ml
what is the anatomic dead space
The amount of gas that never makes it past the conducting zone (about 150ml)
What happens if Vt is lower than Vd (dead space)
no exchange of air. Vt must be greater than Vd
What is the anatomic dead space ventilation
the volume of fresh gas reaching the anatomic dead space each minute
What is the alveolar ventilation
The volume of fresh gas reaching the respiratory zone each minute
The minute ventilation is the sum of?
the sum of alveolar ventilation plus dead space ventilation
Why is there a physiological dead space (versus anatomic dead space)
sometines increases in minute ventilation are not matched by increases in alveolar ventilation, so dead space appear to be increased.
The total dead space, also referred to as physiological dead space, is the volume of inspired gas that does not exchange CO2
2 components of physiological dead space
VD Physiological = VD Anatomic + VD Alveolar
what is partial pressure
the relative amounts of each gas in a mixture is reflected in its partial pressure.
Partial pressure are exerted in proportion to the number of molecules present in the mixture
what is the water vapor pressure for body temperature (37 C)
47 torr or 47 mm Hg
How can we calculate the volume of Co2 eliminated from the lungs each minute?
The alveolar CO2 equation, where FACO2 is the fraction of CO2:
What is the partial pressure in the alveoli (PA) of N2? O2? Co2? H2O?
N2: 573
O2: 100
Co2: 40
H2O: 47
Total atmospheric pressure at sea level
760 mmHg
how are related fraction concentration of CO2 and alveolar CO2 partial pressure ?
They are proportionally related.
What is a fractional concentration ?
the volume of CO2 eliminated from the lung each minute - VCO2
Important formula for PACO2
explain
The CO2 fraction pressure is proportianately related to the amount of CO2 excreted by the alveoli, and inversely related to the minute ventilation.
If you stop breathin (minute ventilation decreased drastically) the PACO2 will increased.
If you exercise and produce more CO2 (VCO2), the partial pressure will also increase (but will be readjusted by increasing the minute ventilation to make sure that the PACO2 stays within limit)
What is the check and balance system to keep PACO2 within normal limit
minute ventilation is adjusted to keep PCO2 within tight limits by ensuring adequate alveolar ventilation
So what happens if Alveolar ventilation is too low
- Increased PACO2
- Respiratory acidosis - Increased [H+] and low pH in the blood
Why is PACO2 so related to the blood concentration of CO2
Because CO2 is a highly soluble gas, so basically if PACO2 increases in the alveolar, it will also increase in the blood. in fact, PACO2 = PaCO2 (arterial partial pressure)
What happens in alveolar ventilation is too high
- Decreased PACO2
- REspiratory alkalosis : decreased [H+] and high blood pH
What is the metabolic regulation of acid-base balance?
the other way the body can regulate alkalosis or acidosis (appart from the lungs)
What is the major metabolic buffering system
HCO3-
What regulates the level og HCO3- ?
The kidneys
Which system can act the fastest to deal with acidosis or alkalosis?
The lungs - Changes in blood CO2 with ventilation is faster than the kidney
What results in an increased of [HCO3-] ?
Metabolic alkalosis - increased in blood pH
What results in a decrease of [HCO3-] ?
Metabolic acidosis, decreased blood pH
difference between osis and emia
osis is a process and emia is blood value
important formula for acid-base balance
[H+][HCO3-] = 24 x PaCO2
what determines the pH
The ratio of HCO3- / PaCO2
So how do the kidneys react with an increase of PCo2 ?
respiratory acidosis, kidney compensates by increasing HCO3- (to increase pH)
And how do the lungs react to a metabolic acidosis?
So metabolic acidosis = a decreased of HCO3- = acidosis, so lungs want to increase pH, so decreases the partial pressure of Co2, by ventilating more
what happens to the respiratory muscles if the tissue is non compliant?
they will be more solicitated
what region of the lungs experience a bigger change in volume with the inspiration?
the lower region of the lung - more compliant
2 types of respiratory failures
type 1: Decreased PaO2
Type 2: Increased PaCO2
what is respiratory failure?
When the respiratory system is unable to keep up and cannot accomplish its job of exchanging O2 and CO2
major categories of respiratory failures (5)
- abnormal lungs with impared gas exchange
- stiff lungs or stiff chest wall (low compliance)
- obstructed airways (high resistance)
- impaired muscle function
- suppression of respiratory drive
how is the hyperinflation of lungs leads to inspiratory muscle dysfunction?
if lung volume is greatly increased, the diaphragm is flattened/shortened all the time. Muscles that are shortened do not contract efficiently
