Homeostasis Mini-cases Final Exam
74 yo, Neurodegenerative, severe weakness over 3 months, difficulty breathing. Short of breath and breathing rate increased when lying down. Correct Answer: Weakness of hand and arm, suggests impairment of C5 and T1. C5 is innervation of diaphragm so suggests d...
difficulty breathing short of breath and breathing rate increased when lying down
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Homeostasis Mini-cases Final Exam
74 yo, Neurodegenerative, severe weakness over 3 months, difficulty breathing. Short of breath and
breathing rate increased when lying down. Correct Answer: Weakness of hand and arm, suggests
impairment of C5 and T1. C5 is innervation of diaphragm so suggests diaphragm is weak. Lying down you
lose the effects of gravity helping her moving diaphragm downwards and chest up and out. Internal
intercostal and abdominal muscles innervated by thoracic = T1.
Describe innervation and muscles used for inspiration and expiration Correct Answer: During quiet
inspiration using diaphragm (innervated by C3, C4, C5, moves down) and external intercostals
(innervated by thoracic). During max inspiration use pectoralis major, scalene, and sternocleidomastoid.
During quiet expiration the diaphragm and the intercostal relax which leads to recoil. During max
expiration utilize abdominal muscles (innervated by thoracic and lumbar) and internal intercostals
(innervated by thoracic).
74 yo, Neurodegenerative, severe weakness over 3 months, difficulty breathing. Short of breath and
breathing rate increased when lying down. Why would she breath faster when lying down? Correct
Answer: Ventilation, carbon dioxide elimination. If she wants to maintain the same minute ventilation,
harder for her to take a full breath, so she will make many small breaths instead.
Aspirating food into airway where is food most likely to go? Correct Answer: Right main bronchus is
almost a straight shot down. Will go to most posterior part: If standing upright then food will go into
right lower. If someone is lying down then food will go into right upper lobe and superior segment right
lower lobe. Middle lobe is anterior so probably won't go in there.
A patient has fluid in the pleural space in the right chest. You want to place a needle into the pleural
space along the 8th rib. Given you knowledge of anatomy, how would you decide whether it is safest to
insert the needle along top margin of the rib or along the lower margin of the rib? Correct Answer:
Neurovascular bundle runs right under the rib. So always want to go just above the top of the rib. If go
below risk hitting neurovascular bundle and causing significant bleeding.
You are trying to determine if the left atrium is enlarged in your patient. You have an x-ray, which shows
clearly the right and left mainstem bronchi; how would you determine if the left atrium is enlarged
based on the position of the bronchi Correct Answer: If left atrium gets larger it lifts up the left
mainstem bronchi which increases angle will be widened left mainstem bronchus will be more
horizontal, sign you have left atrial enlargement
Tripod Correct Answer: Fix arms, then pectoralis major rather than lifting arms can lift chest up and out
2 mo infant, not growing appropriately, whooshing between heart beat on auscultation, diagnoses
defect, or an opening between ventricles, where is blood going and how do you know? Correct Answer:
Whooshing is turbulent flow. In this case, suggests left to right blood flow since able to here on anterior
side of patient: ventricular septal defect with left to right shunt. Hole is causing blood to go from left
ventricle to right ventricle. Since right ventricle is more anterior and hear whooshing on anterior
suggests going left to right shunt. In addition if patient is normally saturated (not blue / cyanotic) then
,may further suggest left to right. Right to left shunt would lead to deoxygenated going through aorta
which would lead to lower oxygenation. Failure to thrive because inability augment cardiac output.
What heart structures anterior vs. posterior? Correct Answer: Anterior view: see right atrium and right
ventricle primarily. Posterior view: see left atrium primarily and left ventricle.
Angle of interventricular septum with respect to anterior chest wall? Correct Answer: Interventricular
septum lies between the two ventricles. From anterior view, interventricular septum points down in the
same plane as right ventricle. Near PMI.
Normal structures RBC travels through, normal pressure, average oxygenation Correct Answer: Inferior
& superior vena cava -> right atrium -> tricuspid -> right ventricle -> pulmonic valve pulmonary artery ->
lungs -> pulmonary veins -> left atrium -> mitral valve -> left ventricle -> aortic valve -> aorta. Pressure is
higher on the left than on the right. Higher oxygenation on left than on right.
Hole between ventricles, how would that affect path blood travels, pressure, and oxygenation? 2 month
old fetus Correct Answer: In utero, right ventricle is quite thick compared to left therefore a fetus with
hole between ventricles may have blood going from RV to LV and then to aorta, would see lower
oxygenation. But as grow the left ventricle is thicker so blood goes from LV to RV and then to pulmonary
artery. On echo will see higher oxygenation than normal in the right ventricle.
Tricuspid valve regurgitation will be heard when? Correct Answer: Not closing properly leads to
turbulent flow, heard during systole. Diastole is when blood filling in ventricles since heart relaxed,
therefore valve is open. Systole is when the heart contracts therefore valve closes.
Mitral valve regurgitation, when and where will you hear? Correct Answer: Heard during systole. Hear it
at the apex (think about anatomy)
Create a hypothesis, based on physiological principles, to explain the low blood pressure when Serena
arrived in the emergency department. How might the body have compensated to prevent the fall in
blood pressure?: Serena is a 75 year old woman with a history of hypertension and recurrent
pneumonia. She has also smoked cigarettes for nearly 50 years and tends to get discomfort in her lower
legs when she walks more than a few blocks. She has been feeling poorly for the past 24 hours with
increased cough. Today she developed chills and fever to 102 degrees; in the past hour she noted
dizziness and called her daughter to take her to the hospital. When she arrived in the hospital her blood
pressure was 70/40 mm Hg. The doctors found her to be confused when they asked her questions. Her
skin was diffusely warm and flushed and a bruit was noted in the periumbilical region. After giving her
fluids, antibiotics, and a medication to constrict her blood vessels, the blood pressure was 100/70 mm
Hg. Serena's confusion had resolved but over the course of 10 hours, she made minimal urine. Over the
course of the next 12 hours, blood pressure rose to 130/90 mm Hg and the urine output increased.
Correct Answer: Bacterial infection -> systemic infection -> cytokines release -> vasodilation and
increased permability. Vasodilation -> increased radius -> decreased blood pressure. Increase
permeability -> decreased intravascular volume-> decreased blood pressure. Decrease intravascular
volume -> decreased urination.
Create a hypothesis, based on physiological principles, to explain the bruit heard on the abdominal
exam. Include in your answer an explanation for why Serena's confusion improved with blood pressure
100/70 mm Hg but the urine output remained low until the blood pressure rose to 130/90 mm Hg:
,Serena is a 75 year old woman with a history of hypertension and recurrent pneumonia. She has also
smoked cigarettes for nearly 50 years and tends to get discomfort in her lower legs when she walks
more than a few blocks. She has been feeling poorly for the past 24 hours with increased cough. Today
she developed chills and fever to 102 degrees; in the past hour she noted dizziness and called her
daughter to take her to the hospital. When she arrived in the hospital her blood pressure was 70/40 mm
Hg. The doctors found her to be confused when they asked her questions. Her skin was diffusely warm
and flushed and a bruit was noted in the periumbilical region. After giving her fluids, antibiotics, and a
medication to constrict her blood vessels, the blood pressure was 100/70 mm Hg. Serena's confusion
had resolved but over the course of 10 hours, she made minimal urine. Over the course of the next 12
hours, blood pressure rose to 130/90 mm Hg and the urine output increased. Correct Answer: Stenosis
in aorta is causing turbulent flow = bruits. Which is why her legs hurt when she walks (claudication).
Prioritize the blood flow to the brain to preserve brain function since most important. Also, kidneys are
not getting enough perfusion because downstream of a blockage therefore need a higher pressure.
Takes more work to overcome higher resistance where blockage is.
Create a hypothesis to explain the wheezing when Juan listened to Mike's chest. In your answer explain
why the wheeze varied with the phase of breathing. Create a hypothesis to explain the sensation that
Mike had that he had to work harder to breathe. Explain your reasoning based on changes in physiology:
Swallowing peanuts (one goes wrong way), then working harder to breathe, wheezing and diminished
breath sounds on right chest posteriorly, wheeze prominent on exhalation than inhalation Correct
Answer: Obstruction right lower lobe -> decrease radius -> increase resistance -> increase velocity to
maintain flow -> increase reynold's number -> increase turbulence -> vibrations in airways -> focal
wheezing. Exhalation (less volume, more resistance) is when lung volume is smallest which leads to
smaller airways radius which leads to wheezing heard on exhalation. Work harder to breathe: increasing
resistance, flow stays same, increase change in pressure which increases work required to take a breath
based on Ohm's Law. (V = IR -> change in pressure = flow x resistance)
85 yo with memory loss, visual loss, chronic hypertension; prescribed beta 1 blocker, took 3 by accident
-> dizziness, stumbling. Create physiological hypotheses to explain: a) why did she feel dizzy when
standing? b) Why did she feel better when lying down? Correct Answer: Beta 1 receptor normally is
activated by epinephrine leads to higher contractility (does not affect veins since controlled by beta 2
receptor). Giving beta 1 blocker would decreases contractility which would decrease systemic blood
pressure. Less blood going to brain makes dizzy. Cellular level: epinephrine -> beta receptor -> Gs ->
adenylate cyclase -> cAMP -> PKA -> phosphorylate ryanodine receptors and phospholambin -> calcium
in cytosol -> tropomyosin doesn't block actin binding. Blocking beta receptor leads to lower calcium less
actin myosin interaction leads to less contractility. When standing up heart needs to work harder to
pump blood to the brain because larger pressure differential due to gravity. Lying down increase venous
return increase preload. Normally when blood pressure drops activate sympathetic nervous system to
increase heart rate, contractility, and systemic vascular resistance. Beta blocker prevents increase heart
rate and contractility.
Why did the norepinephrine have relatively little impact on the Mr. Robinson's blood pressure? Draw a
normal Starling curve and show where Mr. Robinson would be on that curve before he was given fluids
or medicines. How would this curve change with the administration of norepinephrine?: 30 year-old,
taking indomethacin four times a day, at work today, he felt nauseated and a bit light-headed, vomited
liter of bright red blood -> started intravenous fluids, blood pressure was measured at 60/40 mm Hg ->
norepinephrine and the patient's heart rate rose from 130 to 150 beats/min but only small increase in
blood pressure -> increased fluids and transfusing blood while reducing the norepinephrine dose. Mr.
, Robinson's blood pressure rose over the next hour to 100/70 mm Hg and his heart rate fell to 100
beats/min. Correct Answer: Indomethacin (NSAID) -> erode stomach mucosa -> stomach ulcers ->
ulcerate down to artery -> GI bleeding -> High blood loss -> decreased volume -> decreased preload
(move to left on Starling curve since decreased EDV)-> decrease blood pressure. Giving norepinephrine
increases contractility, heart rate, increase SVR. Leads to upward shift on Frank Starling curve. Even
though increase stroke volume, such low volume doesn't matter how much beating heart won't lead to
increased blood pressure. Also body was already increasing heart rate (130). When give blood and fluids
then able to move along Frank Starling curve. Blood is colloid, and stays in blood stream much better
than IV fluids increases volume more.
Why did the administration of fluids and blood achieve a better result than the norepinephrine? Where
would the patient be on his Starling curve after the administration of fluid and blood?: 30 year-old,
taking indomethacin four times a day, at work today, he felt nauseated and a bit light-headed, vomited
liter of bright red blood -> started intravenous fluids, blood pressure was measured at 60/40 mm Hg ->
norepinephrine and the patient's heart rate rose from 130 to 150 beats/min but only small increase in
blood pressure -> increased fluids and transfusing blood while reducing the norepinephrine dose. Mr.
Robinson's blood pressure rose over the next hour to 100/70 mm Hg and his heart rate fell to 100
beats/min. Correct Answer: Blood is colloid, and stays in blood stream much better than IV fluids. After
administration of blood and fluids able to move along to the right on frank starling curve since now
increasing EDV. Since the line is curved, the increase in EDV leads to a higher increase in stroke volume
than increasing contractility does.
Explain why Mr. Robinson's skin became more pale and cold with norepinephrine. Why was his urine
output very low? Was the norepinephrine helping him or hurting him? Explain your answer: 30 year-old,
taking indomethacin four times a day, at work today, he felt nauseated and a bit light-headed, vomited
liter of bright red blood -> started intravenous fluids, blood pressure was measured at 60/40 mm Hg ->
norepinephrine and the patient's heart rate rose from 130 to 150 beats/min but only small increase in
blood pressure -> increased fluids and transfusing blood while reducing the norepinephrine dose. Mr.
Robinson's blood pressure rose over the next hour to 100/70 mm Hg and his heart rate fell to 100
beats/min. Correct Answer: He was pale and cold due to the sympathetic response of his body which
lead to increased systemic vascular resistance to shunt blood to the core. Kidney not getting enough
perfusion because decreased blood pressure why urine output low. Because volume was so low wasn't
really helping since increasing HR and contractility doesn't really help when volume so low.
38 year-old woman, major automobile accident, injuries of the phrenic nerves bilaterally. Her maximal
inspiratory pressure is only -30 cm H2O (normal is -80 to -120 cm H2O): Predict the impact of this injury
on total lung capacity, functional residual capacity, and residual volume. Explain your reasoning Correct
Answer: Phrenic Nerves innervate the diaphragm. Reduced ability to contract diaphragm. Reduce ability
to contract diaphragm -> reduced lung volume -> reduced total lung capacity. During total lung capacity:
lung force goes inward, chest wall force goes inward, muscles go outward. For this patient the outward
force of the muscles will be reduced therefore total lung capacity is reduced. Functional residual
capacity: volume in lungs after relaxed breathing = residual volume + expiratory reserve volume. During
FRC: the chest wall wants to go outward and the lungs want to come inward and they cancel each other
out therefore, muscles not involved, therefore FRC is not changed in this patient. Residual volume is the
remaining volume of air in the lung in after forced expiration, still some air even after forced expiration.
For residual volume: the chest wall wants to really want to go outward, the lungs want to go inward, the
chest wall force outward is high therefore the expiratory muscles have a force inward. The expiratory
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