Lecture 6 (hypoxia)-Exam 2

Question 1

Hypoxemia:
* What is it? (2)
* What does not necessarily indicate?

Answer 1

• Abnormally low level of oxygen in the blood
• O2 supply is inadequate to the body as a whole (general hypoxia) or to a specific region (tissue hypoxia)
• Hypoxemia does not necessarily indicate tissue hypoxia

Question 2

skipped slide

V/Q mismatch:
* Lung regions with low ventilation?
* Lung regions with high ventilation?

Answer 2

• Lung regions with low ventilation compared to perfusion will have a low alveolar oxygen content and high CO2 content
• Lung regions with high ventilation compared to perfusion will have a low CO2 content and high oxygen content

Question 3

skipped slide

What is Alveolar-arterial gradient (A-a)

Answer 3

is the measure of the difference between the partial pressure of O2 in the alveoli and in the arterial blood – provides the efficiency of gas exchange in the lungs and can help narrow down possible causes of hypoxemia

Question 4

Hypoxemia due to V/Q mismatch can or cannot be corrected? Explain

Answer 4

Hypoxemia due to V/Q mismatch can be corrected with low to moderate flow supplemental oxygen and is characterized by an increased A-a gradient.

Question 5

Measurements of Oxygen:
* Arterial O2 sat?
* A-a oxygen gradient?

Answer 5

• Arterial oxygen saturation – SpO2 via pulse oximeter or SaO2 via ABG
• A-a oxygen gradient – Alveolar and arterial oxygenation - the difference between amount of oxygen in the alveoli (PAO2) and amount of oxygen dissolved in the plasma (PaO2)

Question 6

⭐️

Obesity Hypoventilation Syndrome:
* What is another name?
* What is it?
* Prevalence increases?

Answer 6

“Pickwickian Syndrome”

Awake alveolar hypoventilation (elevated PaCO2 levels) in obese patient with alternative causes of hypercapnia and hypoventilation have been excluded-> Not fully getting rid of CO2, restrictive pattern

Prevalence increases with BMI
* BMI of 30-35 is 8-12%
* BMI >=40 is 18 – 31%
* BMI >=50 = 50%

Question 7

Obesity Hypoventilation Syndrome:
* Correlation with OSA: Study of patients presenting with OSA? (3)

Answer 7

• ~ 16% of patients with obstructive sleep apnea
• ~ 22% of obese patients with OSA have OHS
• ~20-30% in obese patients with severe OSA

Question 8

⭐️

Obesity Hypoventilation Syndrome
* What is a major risk factor?

Answer 8

Obesity primary risk factor, severe obesity BMI > 50 is the major risk factor.
* Not all patients with obesity develop OHS

Question 9

Obesity Hypoventilation Syndrome: Clincal findings
* BMI?
* May have what?
* All patients with OHS have some form of what?
* What many present late in disease?

Answer 9

Question 10

When to suspect OHS:
* Strong What?
* BMI?
* Unexplained what? (2)
* Sxs of what?
* What happens with face?
* Increased what?

Answer 10

Question 11

Diagnostics OHS:
* What do the labs show? (3)
* What happens to the blood?
* What does the PFTs?
* What does the CXR?

Answer 11

Restrictive pattern – decrease TLC, decreased FVC, decreased FVC1, normal FVC/FVC1 or increased ration

Question 12

⭐️

Diagnostics OHS:
* What happens to your cardiac exam?
* What does the EKG show?

Answer 12

Cardiac – right ventricle enlargement from pulmonary hypertension on EKG and ECHO
* Right axis deviation of +110 or more
* Dominant R wave in V1 (R/S ration > 1 or >7mm tall) – tall R-eaves in right-sided chest leads
* Dominant S wave in V5 or V6 (R/S ratio <1,or > 7mm tall) – deep S-waves in left-sided leads

Question 13

What is the diagnostic gold standard for OHS? ⭐️

Answer 13

Gold standard – sleep studies with continuous
carbon dioxide monitoring (polysomnography)

Question 14

Treatment for OHS:
* What is the first line?
* All patients with OHS have some form of what?

Answer 14

• First-line: Noninvasive positive airway pressure (PAP) together with weight loss are the initial first-line therapies
• All patients with OHS have some form of sleep disordered breathing; PAP should NOT be delayed with the patient tries to lose weight.

Question 15

Supportive Therapies: OSH
* Avoidance of what?
* Treatment of what?

Answer 15

Avoidance of alcohol and sedatives
* Relaxing the muscles of the airway

Treatment of comorbid conditions
* COPD
* Hypothyroidism

Question 16

OSA:
* Most common what?
* What is it?

Answer 16

• Most common sleep-related breathing disorder and has significant adverse health consequences
• Recurrent obstructive apneas, hypopneas, and/or respiratory effort-related arousals caused by repetitive collapse of the upper airway during sleep

Question 17

Epidemiology of OSA:
* Mc in who?
* Based on what?
* Prevalence increasing and may be related to?

Answer 17

• Most common in older males
• 15-30 % adult males, 10-15% adult females in US
  * Based on apnea-hypopnea index (AHI) 5 or more events per hour of sleep
• Prevalence increasing and may be related to increasing rates of obesity or increased detection rates

Question 18

Risk factors of OSA:
* What are they (5) ⭐️ ⭐️
* What are the less well established risk factors?
* Certain conditions carry higher prevalence?
* Increased what? ⭐️ ⭐️

Answer 18

Question 19

⭐️

Clinical Features: OSA
* What happens in the daytime?
* Patient or partner complaints/concerns about?
* Morning what?
* What is common associated surgery?
* What will be on exame?

Answer 19

Question 20

OSA

Snout and spin?

Answer 20

• Snout – pt has the disease will test positive; if negative then pt most likely does not have the disease
• Spin – pt does not have the disease; if tests positive then pt most likely does have the disease

Question 21

How do you dx OSA? ⭐️

Answer 21

In-laboratory polysomnography (PSG) is the gold standard diagnostic test
* Full-night; split-night (diagnostic then therapeutic with PAP)

There are home sleep study devices, but gold standard is laboratory based.

Question 22

What is this? What does the pink mean?
* What do you look for? what are the ranges?

Answer 22

Polysomnography
* Pink – not ok->Desaturation of O2 during apnea arrests

Look for apnea/hypopnea index. Look for total amount of apnea and hypopnea periods over # of hours of sleep (like 8hrs).
* Mild – 5-14.
* Moderate – 15-30
* Severe – 30+

Question 23

What is the STOP-band questionnaire?

Answer 23

Question 24

What are non-osa related conditions associated with sleep-disordered breathing?

Answer 24

Complicated OSA

Question 25

Treatment of OSA: * Txt begins with what? * What type of therapy?

Answer 25

* Treatment begins with patient education and behavior modification. * Positive airway pressure therapy – should be recommended to all patients with diagnosed OSA.

Question 26

Conservative adjunctive treatments for OSA?

Answer 26

Question 27

Complications of OSA: * MVA? * Neuropsych? * CV and cerebrovascalar? * What happens to heart and lungs? * What other diseases? (2) * What happens to the liver?

Answer 27

Question 28

Answer 28

Risk factor – tongue enlargement; body mass !!

Question 29

What is normal pH, CO2, O2, HCO3?

Answer 29

* pH – 7.35-7.45 * CO2 – 35-45 * O2 – 80-100 * HCO3 – 22-24

Question 30

Acid-Base Disorders * Are group of conditions characterized by what? * Categorized as what? * Dx is made by what? ⭐️ What is the txt? ⭐️

Answer 30

* Acid-base disorders are a group of conditions characterized by changes in the concentration of hydrogen ions (H+) or bicarbonate (HCO3-), which lead to changes in the arterial blood pH * Categorized as acidosis or alkaloses and respiratory or metabolic, depending on the cause of the imbalance * Diagnosis is made **by arterial blood gas (ABG) interpretation** * **Treatment is based on identifying the underlying cause** ## Footnote CO2 +H2O = H2Co3 = HCO3 + H * The more CO2 -> the more H will be made and make the environment acidic (low pH) * Lower CO2 will create alkalosis (high pH)

Question 31

pH and Acid * Why is pH important? * What is H+? * H+ represents what? What does it cause? * As the number of protons in the body goes up, the pH will go what? * Blood has only one pH; regulating pH will alter all what?

Answer 31

Question 32

ACID BASE * What is the CO2/bicarbonate system equation? * The body can regulate what? * Bicarb plus H+ produce what? The body can use what? What is breathed out? * Clinically we can measure what?

Answer 32

Question 33

Factors that cause a right shift of the oxygen-hemoglobin dissociation curve * When is o2 released? * In these situations, hemoglobin has what? * When does hemoglobin give up more oxygen more readily (3)

Answer 33

Question 34

Factors that cause a left shift of the oxygen-hemoglobin dissociation curve * This type of shift prevents what? * What does hemoglobin do? * What are the causes (3)

Answer 34

Question 35

# Skipped slide partial pressure of oxygen rises, there are more what?

Answer 35

partial pressure of oxygen rises, there are more and more oxygen molecule available to bind with hemoglobin.

Question 36

Oxygen-Hemoglobin Dissociation Curve * As PaO2 falls, hemoglobin saturation also falls as what happens? * At around a saturation of 90%, the dissociation curve does what? Why? * Since normal PaO2 is between 90-100 mmHg, an O2 saturation of 90% is not normal. An oxygen saturation of 90% corresponds to what?

Answer 36

* As PaO2 falls, hemoglobin saturation also falls as hemoglobin releases oxygen to the tissues in the areas of the lower oxygen supply. * At around a saturation of 90%, the dissociation curve drops off quickly. This is because hemoglobin binding sites become less attracted to the oxygen as it is bound to fewer oxygen molecules. * Since normal PaO2 is between 90-100 mmHg, an O2 saturation of 90% is not normal. An oxygen saturation of 90% corresponds to a PaO2 of 60 mmHg, this is the minimum oxygen concentration providing enough oxygen to prevent ischemia in tissues.

Question 37

Bicarbonate: * **base or acid?** * Why organ regulated bicarb (how?) ? What is the normal limits? * Can be used where? * **Anything that happens with bicarbonate in the body is what type of process? **

Answer 37

* BASE * Kidneys regulate, 24-26 is normal * Kidneys: Reabsorption of filtered bicarb by the proximal tubule & Renal excretion of hydrogen ions * METABOLIC PROCESS

Question 38

In a metabolic problem both, what can occur at the same time? Give examples?

Answer 38

In a metabolic problem both an acidosis and an alkalosis can occur at the same time as in incidence of vomiting (alkalosis) and diarrhea (acidosis) & aspirin

Question 39

# ⭐️ About CO2 * Comes from what? * Acid or base? * Produced where? * How can it leave the body? * Can only have what? Why? * Changes can occur how fact?

Answer 39

Question 40

# ⭐️ Bicarbonate and PCO2 * What is there in the body? * Bicarb is produced generated and regenerated where? Where can it be lost? * Co2 is made where? Regulated through what?

Answer 40

There is a balance in the body. * Bicarb is produced generated and regenerated in the kidney and can be lost anywhere in the body * CO2 made everywhere in the body and regulated through the lungs

Question 41

Acid Base * How does the healthy body regulate pH? (paCO2?

Answer 41

PaCO2 : by changing ventilation rates * CO2 elimination via the lungs is the main way the body eliminates acid and maintains acid-base homeostasis

Question 42

HCO3 regulated? * What happens in the kidney?

Answer 42

* by reabsorption of virtually all the filtered HCO3- by the proximal tubule * this process simply keeps HCO3- from being lost in the urine and therefore prevents metabolic acidosis from developing. * Kidney controls the plasma HCO3- is by eliminating enough hydrogen ion to equal the fixed acid produced each day

Question 43

# ⭐️ What is metabolic acidosis/alkalosis? What is respiratory acid/alkalosis?

Answer 43

Metabolic acidosis: * Caused by excess H+ production or HCO3- loss (such as in proximal renal tubular acidosis) Metabolic alkalosis: * Caused by excess HCO3- production or H+ loss (such as the renal system overwhelmed and can not reabsorb all bicarb thus it spills over into the urine) Respiratory acidosis: * Caused by CO2 retention (↓alveolar ventilation rate) Respiratory alkalosis: * Caused by excess CO2 removal (↑alveolar ventilation rate)

Question 44

How do you do the davenport diagram

Answer 44

Question 45

Metabolic acidosis: * What are causes of increase H production? * What are causes of HCO3 loss?

Answer 45

Question 46

What are the causes of respiratory acidosis?

Answer 46

Question 47

Metabolic alkalosis: * What are the causes of H loss? * What is the cause for HCO3 intake?

Answer 47

Question 48

What are the causes of Respiratory Alkalosis?

Answer 48

Question 49

Answer 49

Question 50

Mechanical Ventilation * What is mechanical ventilation? * What does a ventilator do? * What does it maintain/improve? * What does it remove? * What does it decrease?

Answer 50

## Footnote Under slide: Mechanical ventilation is a procedure often performed in patients in respiratory failure, which is defined broadly as the inability to meet the body’s needs for oxygen delivery or carbon dioxide removal. A ventilator delivers air, usually with an elevated oxygen content, to a patient’s lungs via an endotracheal tube to facilitate the exchange of oxygen and carbon dioxide.

Question 51

What are the indications for mechanical ventilation?

Answer 51

* Cardiac or respiratory arrest * Tachypnea or bradypnea with respiratory fatigue or impending arrest * Acute respiratory acidosis * Refractory hypoxemia (when the PaO2 could not be maintained above 60 mm Hg with inspired O 2 fraction (FI O2 )>1.0) * Inability to protect the airway associated with depressed levels of consciousness ## Footnote Signs/symptoms: hypoxia, tachypnea, agonal breaths, hypoxemia, hypercapnia

Question 52

What are some otehr indications for mechanical ventilation?

Answer 52

* Shock associated with excessive respiratory work * Build up of lactic acid * Inability to clear secretions with impaired gas exchange or excessive respiratory work * Newly diagnosed neuromuscular disease with a vital capacity <10-15 mL/kg * Short term adjunct in management of acutely increased intracranial pressure (ICP)

Question 53

What are the two types of MV? (would know invasive)

Answer 53

Question 54

Invasive vs. Non- invasive Ventilation * When would you consider non invasive ventilation? * When is resp failure likely be resersible?

Answer 54