Exam 4 Flashcards
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
What information does diffusion capacity provide? What is the abnormal value for DC and what does it mean? What does a normal DC value mean? What does DC not tell you?
Diffusion capacity provides information regarding the amount of surface area available for diffusion.
DC < 80% means decreased area for gas exchange so think EMPHYSEMA Normal DC (>80%) means think ASTHMA or UPPER AIRWAY OBSTRUCTION
DC does NOT tell you how well diffusion works!
Name the values for a positive bronchodilator (BD) response test. What does BD test evaluate?
Pos BD response is either FEV1 or FVC increased by 12% and 200ml.
BD evaluates the reversibility of airflow obstruction. A pos BD test means the airflow obstruction is reversible.
Describe how the flow-volume loop would look with an obstruction. Describe how it would look with a restriction.
Obstruction: the top exhalation portion would be concave
Restriction: The width of the loop would be reduced.
Describe how the flow-volume loop would look with an intrathoracic obstruction. And extrathroacic obstruction.
Intrathoracic obstruction: the top exhalation portion would be flatter
Extrathroacic obstruction: the bottom inhalation portion would be flatter
A restricted pt will present with what kind of TLC (high or low?) And if their DLCO is low? DLCO normal?
Restriction = low TLC
If DLCO is low = intra-pulmonary source of restriction
If DLCO is normal = extra-pulmonary source of restriction
Autonomic control of breathing is controlled by what?
Voluntary control of breathing is controlled by what?
Autonomic control = Brainstem (pons and medulla)
Voluntary control = cerebral cortex
The peripheral and central chemoreceptors are each sensitive to changes it what?
And where are they located?
Peripheral chemorecpetors are sensitive to changes in O2. They are located in the aortic arch and carotid bodies.
The central chemoreceptors are sensitive to changes in CO2. They are located in medulla.
When there is an increase in O2, what is the response of the chemoreceptors?
Increase in O2 –> peripheral chemorec to decrease ventilation
When there is an increase in CO2, what is the response of the chemoreceptors?
Increase in CO2 –> central chemorec to increase ventilation
As PaO2 decreases, how does that affect ventilatory sensitivity to PACO2?
Decrease in PaO2 –> increased sensitivity to PACO2
A primary disorder of ventilatory control is caused by what?
Caused by a CNS disorder –> hyper or hypoventilation
Name the four secondary disorders of ventilatory control we learned about.
Obesity Hypoventilation Syndrome (OHS)
Obstruction Sleep Apnea (OSA)
Central Sleep Apnea
Sleep-Related Hypoventilation (SRHV)
What is the pathogenesis for obstructive hypoventilation syndrome?
Pathogenesis for OHS:
Impaired chest wall mechanics: compliance is decreased
Impaired muscle function
Displaced diaphragm → impairs efficiency of diaphragm contraction
Altered ventilatory response to CO2 and hypoxemia → lack of drive
Upper airway obstruction
How is obesity hypoventilation syndrome characterized?
BMI > 30 and PaCO2 > 45 mmHg
Name some clinical manifestations of OHS
The low PaO2 causes increased erythropoietin secretion from the kidney, which can lead to increased hemoglobin concentration (polycythemia) Dyspnea with exertion Systemic HTN CHF Angina
What will the PFT and ABG read for a pt with obesity hypoventilation syndrome?
Decreased expiratory reserve volume
Low FRC
TLC and VC are decreased
DLCO is normal or low
FEV1/FVC is normal
ABG: respiratory acidosis
What is the tx for OHS?
Lose weight and treat nocturnal airway obstruction
Describe Obstruction Sleep Apnea.
Repeated reduction (hypopnea) or complete cessation (apnea) of inspiratory flow due to partial or complete obstruction. INSPIRATORY EFFORT IS STILL MAINTAINED!!!
Name some factors that promote airway collapse
Pharyngeal dilator muscle activity which maintains upper airway tone and counteracts extra luminal forces.
They are activated by negative airway pressure and increased PCO2.
Extra soft tissue (fat) around the neck
Low lung volume → decreased compliance and contributes to collapse
Airway size: narrow airway and/or large anatomic features→ more prone to collapse
Fluid shifts: from legs toward neck in supine position
Unstable ventilatory control
Name some chronic pathophysiology that can occur with Obstructive Sleep Apnea
Sympathetic system activation Vascular endothelial dysfunction Oxidative stress & inflammation Hypercoagulability Metabolic dysfunction Adverse cardiovascular outcomes: HTN, MI, stroke, HF, Excessive sleepiness Diminished cognitive outcomes.
Describe the clinical features of Obstructive Sleep Apnea
Partners report loud snoring w/pauses!
Daytime sleepiness
Neck circumference >16” for women and >17” for men
Narrow posterior oropharynx, enlarged tonsils, enlarged tongue and uvula.
There are few more in the syllabus.
How do you diagnose Obstructive Sleep Apnea?
Polysomnography to monitor cardiorespiratory physiology (to include abdominal and chest excursion, nasal/oral airflow and oximetry).
Apnea-hypopnea index of > or = 5 is dx for OSA.
What is the tx for Obstructive Sleep Apnea?
Lose weight No alcohol or sedative before bed avoid supine position CPAP Mandibular advancement device or surgery if all else fails.
What are the key findings with Obstructive Sleep Apnea?
Episodic cessation and reduction of airflow w/ongoing throacic and abdominal movements
Describe Central Sleep Apnea and what it is commonly caused by.
Episodes of apnea and/or hypopnea resulting from low or no respiratory effort occurring in a cyclic fashion.
Commonly caused by cardiac or CNS dysfunction
Pts with both CHF and Central Sleep Apnea can experience what special kind of breathing? How is the breathing characterized?
Cheyne Stokes Breathing characterized by alternating hypopnea and hyperpnea with a crescendo-decrescendo tidal volume.
ABSENCE OF CHEST WALL MOVEMENT!!!
What is the pathogenesis for Cheyne Stokes Breathing?
Mainly caused by prolonged circulation time (due to HF) and over-responsive chemoreceptors.
They hyperventilate –> low CO2 –> chemoreceptors to initiate stop breathing –> high CO2 –> central drive kicks in –> hyperventilation, then the whole process starts all over again.
What is the treatment for Central Sleep Apnea?
Treat HF, CPAP, and O2
What is Sleep-Related Hypoventilation?
Abnormally high PaCO2 during sleep. Usually seen with pt that use chronic opioids or benzodiazepines, that are obese, have severe COPD or neuromuscular disease
What is the diagnosis and treatment for Sleep-Related Hypoventilation
Dx: Polysomnography
Tx: CPAP
What are the two factors that affect airflow? (hint: what is the equation for airflow?)
- decreased driving pressure
- increased airway resistance
airflow = pressure change / airway resistance
What will the PFTs look like for obstructive diseases? How will the flow-volume loop look?
FEV1/FVC = decreased!!!!! FEV = decreased FVC = preserved TLC = can be hyperinflated RV = can be airtrapping
Flow volume loop is concave in the top portion
Asthma is an __________ process that has ______ and _______ symptoms of _______, airflow ______, and airway _____-responsiveness.
Asthma is an inflammatory process that has variable and recurring symptoms of dyspnea, airflow obstruction, and airway hyper-responsiveness.
Name three mechanisms to airflow obstruction in asthma
- Secretions in airway lumen
- Smooth muscle hypertrophy and contraction
- Mucosal edema
Will the bronchodilator response for a pt with asthma be positive or negative and why?
The BD test will be POSITIVE bc asthma is a REVERSIBLE airflow obstruction
What are the three factors that must be controlled for adequate management of asthma?
- medications
- Eliminate control triggers (dust mites, mold, pollution
- Identify stressors (smoking in homes, stressful school environment)
COPD is a chronic condition (a syndrome) characterized by _________ symptoms, ______ obstruction, and ________ reversibility.
COPD is a chronic condition characterized by respiratory symptoms, airflow obstruction, and incomplete reversibility.
Name the two disease processes that lead to COPD and describe them. What are they both characteristic of (hint it’s a ratio)?
- Emphysema: Defined anatomically- irreversible destruction of alveolar walls
- Chronic bronchitis: Defined by hx- productive cough > 3 months/year for > or = 2years
Both are characteristic of a low FEV1/FVC ratio
In the developed world, what is COPD most commonly caused by? In the developing world, what is COPD most commonly caused by?
Developed world: smoking!
Developing word: indoor air pollution, work exposure, outdoor pollution
Name three mechanisms to airflow obstruction in COPD
- Secretions in airway lumen
- Smooth muscle hypertrophy and contraction
- Loss of radial traction
If there is a decrease in ventilation only, how does that affect the level of oxygen in the blood?
What if their ventilation and perfusion are BOTH decreased?
Decreased ventilation only –> hypoxemia
Decreased ventilation and perfusion –> less hypoxemia and preserved VA/Q ratio
How would an overall spirogram look for COPD pt?
The overall spirogram will be elevated in comparison to a normal person
Why do COPD pts have higher FRCs?
W/COPD the recoil forces of the chest wall are > then lungs → chest walls pulling the lungs to a higher volume
What are the effects of hyperinflation on contractility?
Flattened diaphragms cannot contract effectively –> decreased airflow
What is required for the dx of COPD?
Must have a REDUCED FEV1/FVC ratio to dx COPD!!!!
Can you dx COPD based on chest x-ray?
NO!!!! You still need spirometry!!
Name a short-acting beta agonist and long acting beta agonist.
Short acting: Albuterol
Long acting: Salmeterol and Formoterol
Name an short and long acting antimuscarinic
Short: Ipratropium
Long: Tiotropium
What is the management for COPD exacerbations?
- Oral prednisone
- Albuterol
- Azithromycin
If the initial regimen for COPD is not working, what can you add to augment the regimen?
If initial regiment was long-acting Beta-agonist, then add inhaled corticosteroid (Fluticasone)
If initial regiment was long-acting antimuscarinic, then add steroid-beta agonist combination
