Exam 4 Flashcards
(74 cards)
What happens to the oxygen saturation and content if Hb concentration falls?
The oxygen saturation stays the same (bc all the Hb are fully saturated) but the concentration of oxygen decreases bc there is less Hb available to carry O2
What are the major determinants of oxygen delivery to the tissues?
Cardiac output and Hb concentration
Describe hypoxic pulmonary vasoconstriction (HPV)
When there is a decreased in PAO2, blood flow to that alveolus will be constricted. This is the body’s way to prevent a build up of CAO2 within that non-ventilated alveolus. It helps to ensure adequate matching of ventilation and perfusion, which is helpful for preserving blood oxygenation.
What effect does prolonged low PaO2 have on Hb?
Decreased PaO2 –> increase in erythropoietin concentration
Describe carboxyhemoglobinemia
carbon monoxide poisoning
Occurs when large amounts of gas are inhaled –> increased CO levels in the blood which impairs O2 delivery
PaO2 = normal
SpO2 = normal
CvO2 & SvO2 = Low
Describe methemoglobinemia
Ferrous iron 2+ oxidizes to ferric iron 3+ –> conformation change in Hb which prevents O2 from binding to Hb and impairs O2 delivery
Important note: Pulse ox usually reads 87-88% and pt does not respond to supplemental O2
Can be caused by dapsone (pneumocystis prophylaxis), benzocaine or cetacaine.
PaO2 = normal
SpO2 = low
CvO2 & SvO2 = Low
Describe cyanide poisoning
Normal O2 delivery but the mitochondria are unable to utilize the O2 bc cyanide inhibits cytochrome oxidase –> more O2 in mixed venous blood.
Hallmark of cyanide poisoning: high mixed venous blood O2 content and it’s very pink looking
PaO2 = Low or normal
SpO2 = low or normal
CvO2 & SvO2 = High
Describe the Haldane Effect
The oxygenation of Hb decreases the ability of Hb to carry CO2 as carbamino groups (but does not affect the bicarbonate rxn).
As O2 binds to Hb at the lungs, it releases CO2 to diffuse into the alveoli
Describe the Bohr Effect
As Co2 is loaded on to the RBC, the H+ binds to the Hb –> T state configuration –> release of O2 to the tissues
Name two basic factors that can cause hypercarbia and hypocarbia
Hypercarbia is > 45 mmHg and occurs as a result of low alveolar ventilation or increased metabolic production of CO2
Hypocarbia is < 35 mmHg and occurs as a result of high alveolar ventilation or decreased metabolic production of CO2
Name the main muscle used for inspiration along with other muscles that can be used if needed.
Diaphragm
External intercostal
SCM
Scalene
Why don’t the alveolar collapse when we breathe?
Bc of surfactant (a detergent to decrease surface tension) produced by type II pneumocytes.
If there is no surfactant –> atelectasis
Name a process that decreases FRC and name a process that increases FRC
Fibrosis decreases FRC causing the lungs to want to recoil more –> greater pressure inward than outward.
Loss of alveolar elasticity as with emphysema increases FRC causing the chest wall to want to recoil less –> greater pressure outward than inward.
What is radial traction and where is it greatest?
Radial traction pulls the airways open to a higher caliber and decreases resistance to airflow. As you move from a lower to higher lung volume, the alveoli exert greater radial traction on the airways.
When does turbulent and laminar flow occur?
Turbulent flow occurs in larger caliber airways with higher gas velocity. A tumor or other lesion that can narrow the airway can –> a increase in gas velocity due to smaller radius thereby causing turbulent flow.
Laminar flow occurs in smaller caliber airways with lower gas velocity
What does low PIO2 mean and give an example. How does it affect (A-a)changeO2?
Low PIO2 means you are breathing less O2
An example would be higher altitude.
(A-a)changeO2 is normal
What does hypoventilation mean and give an example? What is its hallmark? How does it affect (A-a)changeO2?
Hypoventilation the level of alveolar ventilation is insufficient for O2 influx and CO2 elimination.
Ex: Opiate overdose
Hallmark = increased PaCO2
(A-a)changeO2 is normal
What is diffusion impairment and give an example? Does it cause hypoxemia? How does it affect (A-a)changeO2?
Diffusion abnormalities that –> slower rate of O2 transfer across alveolar capillary bed.
Ex: Exercise at high altitudes
It rarely causes hypoxemia bc there is sufficient time for the Hb to become fully oxygenated. However, if the pt engages in activity, an increased cardiac output can shorten the capillary transit time –> decreased PaCO2
(A-a)changeO2 is increased
What is a shunt and example of a shunt. ? What is its hallmark? How does it affect (A-a)changeO2?
A shunt causes blood to pass from the venous system to the arterial system without going through gas exchange.
Ex: Pneumonia
Hallmark = Administration of O2 does not fully correct the PaO2
(A-a)changeO2 is increased
What is a VA/Q mismatch and give an example? How does change in VA/Q impact PaO2 and PACO2? How does it affect (A-a)changeO2?
With VA/Q mismatch, main problem is with gas exchange.
Example: COPD exacerbation or asthma
When ventilation > blood flow –> HIGH VA/Q –> high PaO2 and low PACO2
When blood flow > ventilation –> LOW VA/Q –> low PaO2 and high PACO2
(A-a)changeO2 is increased
Describe the 4 Steps in determining causes of hypoxemia.
Step 1: Is the pt at high altitude or breathing a low FIO2? If yes, then PIO2 is at least one cause of hypoxemia.
Step 2: Is the PaCO2 > 45 mmHg? If yes, then hypoventilation is at least one cause of hypoxemia.
Step 3: Is the (A-a)changeO2 normal or increased? If no, then there is no other process besides hypoventilation and/or PIO2. If yes, then pt has a mismatch or shunt.
Step 4: Does the pt respond to O2? If yes, then mismatch. If no, then shunt.
What does spirometry provide information about?
Airflow
What is a normal FEV1/FVC ratio? If the ratio is lower than normal what does that mean? What does the FEV1 alone tell you?
Normal FEV1/FVC ratio > 0.70
< 0.7 mean there is obstruction
FEV1 alone tells you the degree of severity
The lung volume test provides what information? What are the abnormal values for the information and what is signify?
Lung volume test prodivdes TLC and RV
TLC > 120% means hyperinflation
TLC <80% means restriction
RV > 120% means air trapping