Flashcards in Pulmonary facts Deck (49)
Partial Pressure of water vapor is dependent on what?
Core body temp
what happens when you half the alveolar ventilation?
the CO2 is going to be DOUBLED!
If you double the bicarb concentration then what is the acid-base situation
remember that pH is determined by the ratio of HCO3: dissolved CO2
so you double both values overall same ratio
Calculate of Alveolar ventilation if you have TV or Vt same thing=750mL, dead space= 150mL, RR=10bpm. What happens if you decrease TV=500ml but increase rate to 20bpm
Va=(Vt - Vd) F
Va = (750ml - 150ml)(10) = 6,000ml/min or 6L/min
Va= (500ml-150ml)(20) = 7,000ml/min or 7L/min
increase in alveolar ventilation by 1L/min
what are causes of hypoxemia?
Ventilation/Perfusion Inequality (think of this first)
R-->L shunting (not corrected on 100% O2)
what does not cause hypoxemia (low oxygen tension in the blood, PaO2)?
Hypoventilation (increased PaCO2 and Increased PaO2 and decreased alveolar ventilation)
Drop in O2 pressure from 150-140mmHg --> causes big ventilation drive. Removal of what extinguishes this response?
Removal of carotid arch
peripheral chemoreceptors ( increases the carotid/aortic bodies) located at carotid sinus-> senses O2 (hypoxia) then H+ and CO2 levels
Alveolar Ventilation, what are the different formulas?
Va= Ve (minute ventilation) - Vd (wasted ventilation)
Va= (Vt-Vd) RR or F
what happens to the V/Q when there is a pulmonary embolus?
perfusion stops but ventilation is unaffected so the V/Q ratio will be infinity
then the gas in the affected alveolus will eventually equilibrate with atmospheric gases (since no gas is entering the blood stream) and alveolar gas tensions will be 150mmHg PO2 and 0mmHg PCO2 (alveolar dead space)
Increases A-a gradient (due to increase in alveolar gas tension (PAO2))
why is there an A-a gradient??
A-a gradient= PAO2- Pa02 --> equilibration between atmospheric 150mmHg and Alveolar 100mmHg --> 100mgHg Arterial PaO2 but this decreases as O2 is used up metabolically as you move through the system circulation so by the time it returns the P02 is 40mmHg
Other equation is PAO2=PIO2-(PACO2/R)
If you are breathing a partial pressure of 50% then this means you have inhaled 50% O2 instead of the normal 21% so what happens?
760mm Hg - 47= 713 x .50 = 356.5
760 mm Hg - 47= 713 x .21 = 149.73
these would be your inspired PIO2 values
.50 or .21 would be your FIO2 values, fractional concentration of O2
plug these into the PAO2= PIO2 - (PACO2/R (0.8)) equation
what is the reason that PH2O is always constant?
temperature dependent variable not pressure dependent so since core body temp is pretty constant we assume 47mmHg
In pulmonary fibrosis (restrictive disease), what happens to the FEV, FVC and lung volume
Lung volume declines
what do central and peripheral chemoreceptors respond to?
Peripheral --> Hypoxia sensors (low PaO2), low arterial pH (high H) and increased PaCO2
Central --> PCO2 levels detect via pH of CSF (detects respiratory acidosis)(located in the medulla)
Emphysema will the EPP go proximal or distal?
EPP will go distal (more resistance because the lungs are much more compliant)
called dynamic compression
In a pressure-volume compliance curve what will emphysema look like compared to fibrosis
Emphysema--> increase compliance of lung--> shift of the pressure-volume curve to the left, increasing the gradient
Fibrosis--> decreased compliance of lung--> shift of the pressure volume curve down to the right (below FRC)
what are the causes of pulmonary edema?
Increased hydrostatic pressure (accumulation of fluid in the interstitum)
Decreased oncotic pressure = lack of absorption and favoring of filtration
Decreased lympathetic drainage
Increased Alveolar Tension
what is the equation for physiological dead space?
Alveolar Ventilation = (Vt-Vd) x F
Vd= Vt x (PaCO2-PeCO2)/PaCO2
(arterial PCO2 is always equal to alveolar PCO2)
Vd= anatomic dead space + alveolar dead space (normal person this value is 0)
How do you increase alveolar minute ventilation?
increase breaths per minute or tidal volume
Why is lung easier to collapse with saline than with water??
Saline washes out the surfactant and therefore there is no surface tension
Increase in lung volume is an increase in radial traction. The amount of air you take in does have an effect on airflow. If you decrease the volume coming in what happens?
increase in resistance?? not sure though
why is the systemic arterial blood partial pressure of oxygen 90mmHg vs 100mmHg in alveoli?
because of physiological shunting, right to left shunt mixes venous and arterial blood, lowering the partial pressure of oxygen
How do you increase minute or alveolar ventilation the best?
80% NO and 20% O2, causes vasodilation and increased the O2 of blood the best
When blood stays in a blood bank for a long time it has decreased 2,3-BPG, so what happens when you transfuse it into someone?
So when transfused into someone they will have a left shift (lower P50) or a decrease in the ability to unload their O2
If you increase the deoxyhemoglobin state (bind H+ or 2,3bpg) what happens?
increase offloading of O2 at lower P02 decreased (lower P50).
Where in the 3 levels of the lung is blood flow and ventilation the highest?
the bottom zone 3
high perfusion, ventilation
If a patient presents to your office and has a tumor and part of his lung is dysfunctional then what physiologically is going on with the patient?
decreased blow flow to that part of the lung, the tumor is essentially closing up the alveoli. So if you run blood past that area you will get deoxygenation of that blood.
A patient has decreased Pa02 and you give the patient 100% oxygen however the partial pressure of O2 in not increased, what is a possible reason for this finding?
Anatomical Shunt (no bloodflow past alveoli so no gas exchange is possible)
aka R --> L shunt
If a patient presents to the ER with a head injury and his respiration rate is resulting in hyperventilation, taking deep breaths. then what will happen to the PCO2 and pH?
Hyperventilation = decreased PaCO2 and increased pH