Final Exam Flashcards
Value of atmospheric O2?
160 mmHg
Value of inspired O2?
150 mmHg
Value of alveolar O2?
100 mmHg
Value of arterial O2 (PaO2)?
100 mmHg
What is the arterial CO2 (PaCO2)?
40 mmHg
Formula for compliance
C = delta V / delta P C= change in lung volume / change in pressure
Majority of total surface area of the lung is found in the
alveoli
all of the following can be measured via spirometry except:
- tidal volume
- vital capacity
- functional residual capacity
- inspiratory capacity
- expiratory reserve volume
functional residual capacity
how does the radii of the various tubes change as we move from the trachea to the alveoli?
Radii of the tubules decreases due to shedding of epithelial cells. Conducting zones (g0-16) columnar/cuboidal epithelia, smooth muscles, thick cartilage Respiratory zones (g17-23) type 1 and type 2 epithelia, No columnar/cuboidal epithelia, cartilage and smooth muscle = smaller radius
Pleural pressure = -7 cm H2O
Alveolar pressure = -3 cm H2O
Transpulmonary pressure = ?
+4 cm H20
A lung compliance test indicates that a 3cm H2O change in transpulmonary pressure generates a 0.9 L change in lung volume? What is the patient’s lung compliance?
0.3 L air/cm H2O
Airway resistance across a set of airways is lowest under which condition?
airway radius is large and the length of the tube is small
As the lungs fill with air and we move from a low lung volume to higher lung volumes, airway resistance will
decrease exponentially
What is the typical Tidal volume?
normal breathing = 0.5L
What is the typical expiratory reserve volume?
air expelled after normal tidal volume expiration = 2L
What is the residual volume?
air that remains after maximal expiration = 1.2 L
What is the forced vital capacity?
air which can be forcible exhaled from the lungs after taking the deepest breath possible = 5L
What is the vital capacity?
air that is exhaled after maximal inspiration = 5L
what is total lung capacity?
max volume the lungs can be expanded = 6L
What is the functional residual capacity?
Air left in lungs below tidal = 2.5L
What is the inspiratory reserve volume?
air that can be inhaled after tidal - 2.5L
What is the inspiratory capacity?
air that can be drawn into lungs after normal expiration (tidal + above tidal) = 3L
What is an obstructive lung disease?
shortness of breath due to difficult exhaling all air from lungs
ex. asthma, cystic fibrosis
What is a restrictive lung disease?
inability to fully fill their lungs with air, restricted from fully expanding
ex: interstitial lung disease
A patient performs an expiratory forced vital capacity maneuver. His FVC is 2L and his FEV1 is 1 liter. Based on your knowledge of these numbers you would predict this person suffers from?
an obstructive lung disease
What is the formula for PaO2?
PaO2 = PIO2 - PaCO2/R
R=0.8
What is formula for PIO2?
PIO2 = oxygen concentration * (Pbar - 47 mmHg) oxygen c (normal) = 0.21 Pbar (normal) = 760 mmHg
A patient begins to hyperventilate while sitting in a clinic on Miami Beach and breathing room air. Over the ensuing 1 minute, his PaCO2 drops to 20 mmHg. What is his PaO2 at that moment in time?
125 mmHg
With respect to the path of O2 diffusion, the proper order for the movement of oxygen across the pulmonary capillary membrane is:
alveolar epithelium, interstitial space, capillary basement membrane, blood
When a gas in the blood, such as oxygen, fails to reach diffusion equilibrium with the alveolar air as it leaves the pulmonary capillary bed is said to be
diffusion limited
What does it mean to be perfusion limited?
oxygen levels reach equilibrium before the blood leaves the alveoli area, no more oxygen can be transported
What does it mean to be diffusion limited?
Interstitial space between the alveoli and capillary is too large, preventing complete oxygen transfer
Under normal physiologic conditions, the maximum capacity of O2 that Hb can carry is approximately
1.34 ml O2
OR
200 mls per liter
How many grams of hemoglobin are present in the blood?
15 g Hb / 100 mL blood
How much O2 is delivered to the body per minute? How much of that is consumed?
1000 mLs of O2 / min, only 250 mLs of O2 are consumed
What is the equation for how much oxygen hemoglobin can carry per liter of blood?
Carrying capacity * hemoglobin concentration * %saturation
units
Which of the following will increase the content of arterial oxygen?
- increased hemoglobin conc.
- decreased hemoglobin saturation
- decreased PaO2
- decreased O2 solubility
increased hemoglobin concentration
What is Henry’s Law? Solubility of O2?
Concentration of a dissolved gas = solubility of gas * deltaP of gas
Solubility of O2 = 0.0031 mLs O2/mmHg / 100 mLs blood
What is the formula for % Hb saturation?
% saturation = actual content / capacity
capacity at 100% saturation is 20.1
What happens to our oxyhemoglobin when we exercise and our metabolism and temperature increase?
Less O2 binding to Hb because of the O2 pressure increase
What is also released when exercise is occurring to help with oxygen release from Hb?
2,3-diphosphoglycerate, produced in anaerobic environments
Does a decrease in pH/increase in PaCO2 cause an increase or decrease in oxygen release from Hb?
increase, they both have effect but are more significant when combined
What is the total oxygen content composed of?
sum of dissolved and hemoglobin bound oxygen
What is polycythemia?
increase in hemoglobin/RBCs, oxygen therapy will not help with this disease
What is anemia?
decrease in hemoglobin/RBCs, oxygen therapy will not help with this disease
How does oxygen content change in CO poisoning?
Decrease in saturation due to present CO2 on hemoglobin, dissolved remains the same
How do we treat CO poisoning?
Increase dissolved O2 content via atmospheric pressure, allows for overall O2 content increase
How do we increase oxygen delivery (qualitatively)?
Increased heart rate, stroke volume, Hb concentration
How can we increase Hb concentration?
Train at high altitudes, blood transfusion after alteration
What is the formula for oxygen content?
HbO2 + dissolved
Hb capacity * Hb conc. * % saturation) + (solubility of O2 * PaO2
A blood gas analysis is performed on a patient and the following values are observed: Partial pressure of oxygen in the arterial blood = 60 mm Hg
Oxygen content = 18 mls O2/ dl of blood
Assuming that all else is normal, what is the percent hemoglobin saturation of this patient?
90%
An arterial blood gas is ordered and the following values are obtained
Hb=17 g/dL
Hemoglobin saturation = 100%
PaO2 = 200 mm Hg
What is the content of total oxygen in the arterial blood sample?
23.38 mLs O2/dL blood
What is the normal rate of respiration?
12 breaths per minute
What is a possible cause for no end tidal CO2?
Lack of blood circulation which prevents CO2 from reaching the lungs
Why might the pulse oximeter show 100% SaO2 while the arterial blood gas value shows 65% SaO2?
carbon monoxide poisoning binding to remaining 45% of Hb
Define ventilation
Removal of CO2
Are PaO2 levels higher or lower with hypoxemia?
lower, high levels of CO2
What is the Hb saturation when PaO2 levels drop down to 60 mmHg
90%
60/90 rule
A patient’s arterial blood gas indicates that her PaCO2 in 55 mm Hg. What can you conclude about her ventilation state?
she is hypoventilating
What is the difference between SaO2 and SpO2?
SaO2 is Hb saturation from arterial blood
SpO2 is Hb saturation from pulse ox
What is the average HCO3-level
24 mEq/L
A post-op patient is still unconscious, but is receiving supplemental oxygen via a mask device. An ABG indicates that
pH = 7.31 PaO2 = 155 mm Hg
PaCO2 = 82 mm Hg HCO3- = 26 mEq/L
Which of the following is false?
-Patient is acidotic
-HCO3- is normal
-PaCO2 is elevated
-ventilation is sufficient given that PaO2 = 155 mmHg
Ventilation is sufficient given that PaO2 = 155 mmHg
What is lung compliance?
ability to stretch and expand
With respect to the pulmonary circulatory system, overall the compliance of the system is…
high
What is pulmonary edema?
fluid entering the interstitial space that cannot be removed, commonly caused by increased hydrostatic
What is the formula for volume of gas diffusion?
V = D * deltaP D = diffusion capacity
What happens to hydrostatic pressure and osmotic pressure as the blood moves through the capillaries?
Hydrostatic pressure decreases, osmotic remains the same. Initial loss of water (10mmHg) then reabsorption (7mmHg)
What happens to the fluid that is not recaptured by the capillary?
Lymphatic vessels collect the residual fluid
What happens if the lymphatic vessels stop working properly?
There will be an accumulation of fluid in the interstitial space
What are the two stages of pulmonary edema?
Early/Interstitial edema - increase diffusion distance
Late edema - alveoli fill with fluid, no gas exchange in these unventilated alveoli
What happens typically with left heart failure?
pulmonary edema, pooling of blood in pulmonary vasculature and increases hydrostatic pressure
Define shunting
No ventilation, but perfusion is occurring (blood circulation)
What does surfactant do?
decreases surface tension, decreases lung recoil, increases lung compliance
How do pulmonary edemas affect compliance?
decreases lung compliance (less able to expand lungs fully)
What is a normal FEV1? (forced expiratory volume in the first second)
4L
What is the average FEV1 / FVC ratio?
80% higher = high recoil
lower = low compliance
What can preload reducers do?
ex. nitroglycerin
dilate the veins, decreases hydrostatic pressure in capillaries
What happens when there is a lack of proteins in the blood? (malnutrition)
Osmotic pressure cannot draw the fluid back into the capillaries and can cause pulmonary edema
What can diuretics (furosemide) do?
dump fluid from plasma/blood, decreases hydrostatic pressure in capillaries
What is an embolism?
blood clot in artery
What are the O2 and CO2 levels in a shunt patient?
O2 = 40 CO2 = 45
What are the O2 and CO2 levels in normal patients?
O2 = 100 CO2 = 40
What are the O2 and CO2 values in pulmonary embolism patients?
O2 = 150
CO2 = 0
because no circulation can bring CO2 to the lungs, no CO2 is present
In late stage pulmonary edema, the ventilation to perfusion (V/Q) ratio will…
decrease
What is the normal pH level?
7.4
What is the normal [H+] level?
40 nmol/L
What is the Henderson-Hasselbalch equation?
pH = pKa + log10 ([HCO3-] / [pCO2*0.03]) pKa = 6.1 constant
What are the three fates of HCO3-?
- Alkalosis - kidney dump HCO3-
- Acidosis - kidney can reabsorb 100% of filtered HCO3- (no bicarbonate in urine)
- Extreme acidosis - reabsorb 100% and kidneys can synthesize more HCO3-
What is metabolic alkalosis with respiratory compensation?
loss of body acids (ex. vomiting), increased pH.
lungs respond by decreasing ventilation so that acid can build up
What is metabolic acidosis with respiratory compensation?
Since kidneys cannot eliminate strong acids (lactic acids, ketoacids), causes acidosis.
lungs respond by increasing ventilation to eliminate some excess acid build - up
What is respiratory acidosis with renal compensation?
insufficient ventilation, rise in PaCO2, pH decrease
kidneys respond by increasing HCO3- reabsorption
What is respiratory alkalosis with renal compensation?
excessive ventilation, loss of acid, rise in pH
kidneys respond by dumping off HCO3-
Arterial blood gas values are as follows: pH: 7.30 PaO2: 60 mm Hg PaCO2: 80 mm Hg HCO3-: 41 mM Glucose: 140 mg/dL This is most likely:
Respiratory acidosis with renal compensation
True or false: in the Henderson-Hasselbalch equation, HCO3- is the denominator
False
Arterial blood gas values are as follows: pH: 7.55 PaO2: 91 mmHg PaCO2: 56 mmHg HCO3-: 36mM Glucose: 99 mg/dL This is most likely...
Metabolic alkalosis with respiratory compensation
According to the Henderson-Hasselbalch equation, is PaCO2 decreases to 20 mmHg, then the arterial pH will
increase, 7.70
A 74 year old moderately dehydrated man was admitted with a two day history of acute severe diarrhea. ABGs are as follows pH: 7.31 PaCO2: 33 mmHg PaO2: 98 mmHg HCO3- = 16mM The most likely diagnosis is...
Metabolic acidosis with respiratory compensation
The respiratory center that controls inspiration is the
dorsal respiratory group (DRG), innervates the diaphragm
Within peripheral chemoreceptors, the response to a drop in PaO2 is greater when…
Arterial PaCO2 is above normal
What do the phrenic motor nerves control?
Innervate the diaphragm, fires in bursts
What does the ventral respiratory group (VRG) control?
Only used during forced expiration
What are the two chemicals that are recepted to regulate breathing?
CO2 and H+
What do central chemoreceptors respond directly to? Indirectly?
H+, CO2 can cross the BBB and be readily converted to H+ (indirect response)
Are the peripheral necessary to detect CO2?
No, central chemoreceptors has same degree of effect alone as when working simultaneously with peripheral chemoreceptor
How do narcotics affect breathing?
Narcotics suppress the medulla, preventing the detection of CO2 levels
When CO2 levels are normal, what detects the low levels of O2?
Peripheral chemoreceptors
If the CO2 and O2 levels are both low, is ventilation going to occur?
No, the low CO2 levels blunt the ability for the low O2 to increase ventilation
How would you test the sensitivity of the chemoreceptors?
Administer low levels (4-5%) of CO2 through mask to observe increase in ventilation, should decrease again when CO2 levels are dropped
What increases the sensitivity of CO2 receptors?
metabolic acidosis (exercise)
How do chronic obstructive pulmonary diseases affect chemoreceptors?
In COPD, PaCO2 levels are chronically elevated and therefore cause the chemoreceptors to become desensitized to the high PaCO2. They must rely on the peripheral chemoreceptors to signal for their bodies to breath (via low PaO2 levels)
True or false; generally the central and peripheral chemoreceptors to work to antagonize one another
false
True or false; the central chemoreceptor becomes desensitized to CO2 under anesthesia
true
When we arrive at high altitude, we begin to hyper-ventilate. This is due
decreased PaO2
A 70 year-old is complaining of severe nausea. He has had problems with peptic ulcer disease and has been having similar pain for the past two weeks. Rather than seeing a physician , he opted to self medicate. Over the past week, he has been consuming large quantities of TUMS (calcium carbonate), and over the counter antacids. While breathing room air, an arterial blood sample is drawn and reveals the following: pH: 7.48 PaCO2: 49 mmHg PaO2: 68 mmHg HCO3-: 35 mEq/L Na+: 139 mEq/L K+: 4 mEq/L Cl-: 96 mEq/L Glucose: 387 mg/dL The most likely explanation for the observed hypoxemia is
hypoventilation that is secondary to a metabolic alkalosis
A patient begins to hyperventilate while sitting on a clinic on Miami beach and breathing room air. Over the ensuing 1 minute, his PaCO2 drops to 20 mm Hg. What is his PaO2 at that moment in time?
125 mmHg
A 74 year old moderately dehydrated man was admitted with a two day history of acute severe diarrhea. ABGs are as follows: pH: 7.31 PaCO2: 33 mmHg PaO2: 98 mmHg HCO3-: 16 mM The most likely diagnosis is...
metabolic acidosis with respiratory compensation
Which of the following is a muscle that is used for expiration?
external obliques
When at sea level and breathing room air, the partial pressure of O2 in inspired air is
150 mm Hg
In the case of severe embolism, over time the gas composition of the alveoli will become
150 mmHg O2
0 mmHg CO2
Regarding pulmonary edema (PE), which one of the following statements is false:
- PE is characterized by increased fluid in the interstitial space
- we move from diffusion limitations to perfusion limitations as PE worsens
- Oxygen therapy can be effective during early stage PE
- PE is characterized by a decreased DL
- There is a decreased gas diffusion with PE
we move from diffusion limitation to perfusion limitations as PE worsens
In late stage pulmonary edema, the ventilation to perfusion V/Q ratio will
decrease
