Lecture 6 (hypoxia)-Exam 2 Flashcards
Hypoxemia:
* What is it? (2)
* What does not necessarily indicate?
- 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
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V/Q mismatch:
* Lung regions with low ventilation?
* Lung regions with high ventilation?
- 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
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What is Alveolar-arterial gradient (A-a)
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
Hypoxemia due to V/Q mismatch can or cannot be corrected? Explain
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.
Measurements of Oxygen:
* Arterial O2 sat?
* A-a oxygen gradient?
- 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)
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Obesity Hypoventilation Syndrome:
* What is another name?
* What is it?
* Prevalence increases?
“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%
Obesity Hypoventilation Syndrome:
* Correlation with OSA: Study of patients presenting with OSA? (3)
- ~ 16% of patients with obstructive sleep apnea
- ~ 22% of obese patients with OSA have OHS
- ~20-30% in obese patients with severe OSA
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Obesity Hypoventilation Syndrome
* What is a major risk factor?
Obesity primary risk factor, severe obesity BMI > 50 is the major risk factor.
* Not all patients with obesity develop OHS
Obesity Hypoventilation Syndrome: Clincal findings
* BMI?
* May have what?
* All patients with OHS have some form of what?
* What many present late in disease?
When to suspect OHS:
* Strong What?
* BMI?
* Unexplained what? (2)
* Sxs of what?
* What happens with face?
* Increased what?
Diagnostics OHS:
* What do the labs show? (3)
* What happens to the blood?
* What does the PFTs?
* What does the CXR?
Restrictive pattern – decrease TLC, decreased FVC, decreased FVC1, normal FVC/FVC1 or increased ration
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Diagnostics OHS:
* What happens to your cardiac exam?
* What does the EKG show?
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
What is the diagnostic gold standard for OHS? ⭐️
Gold standard – sleep studies with continuous
carbon dioxide monitoring (polysomnography)
Treatment for OHS:
* What is the first line?
* All patients with OHS have some form of what?
- 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.
Supportive Therapies: OSH
* Avoidance of what?
* Treatment of what?
Avoidance of alcohol and sedatives
* Relaxing the muscles of the airway
Treatment of comorbid conditions
* COPD
* Hypothyroidism
OSA:
* Most common what?
* What is it?
- 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
Epidemiology of OSA:
* Mc in who?
* Based on what?
* Prevalence increasing and may be related to?
- 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
Risk factors of OSA:
* What are they (5) ⭐️ ⭐️
* What are the less well established risk factors?
* Certain conditions carry higher prevalence?
* Increased what? ⭐️ ⭐️
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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?
OSA
Snout and spin?
- 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
How do you dx OSA? ⭐️
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.
What is this? What does the pink mean?
* What do you look for? what are the ranges?
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+
What is the STOP-band questionnaire?
What are non-osa related conditions associated with sleep-disordered breathing?
Complicated OSA
Treatment of OSA:
* Txt begins with what?
* What type of therapy?
- Treatment begins with patient education and behavior modification.
- Positive airway pressure therapy – should be recommended to all patients with diagnosed OSA.
Conservative adjunctive treatments for OSA?
Complications of OSA:
* MVA?
* Neuropsych?
* CV and cerebrovascalar?
* What happens to heart and lungs?
* What other diseases? (2)
* What happens to the liver?
Risk factor – tongue enlargement; body mass !!
What is normal pH, CO2, O2, HCO3?
- pH – 7.35-7.45
- CO2 – 35-45
- O2 – 80-100
- HCO3 – 22-24
Acid-Base Disorders
* Are group of conditions characterized by what?
* Categorized as what?
* Dx is made by what? ⭐️
What is the txt? ⭐️
- 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
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)
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?
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?
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)
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)
Skipped slide
partial pressure of oxygen rises, there are more what?
partial pressure of oxygen rises, there are more and more oxygen molecule available to bind with hemoglobin.
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?
- 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.
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? **
- BASE
- Kidneys regulate, 24-26 is normal
- Kidneys: Reabsorption of filtered bicarb by the proximal tubule & Renal excretion of hydrogen ions
- METABOLIC PROCESS
In a metabolic problem both, what can occur at the same time? Give examples?
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
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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?
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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?
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
Acid Base
* How does the healthy body regulate pH? (paCO2?
PaCO2 : by changing ventilation rates
* CO2 elimination via the lungs is the main way the body eliminates acid and maintains acid-base homeostasis
HCO3 regulated?
* What happens in the kidney?
- 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
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What is metabolic acidosis/alkalosis? What is respiratory acid/alkalosis?
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)
How do you do the davenport diagram
Metabolic acidosis:
* What are causes of increase H production?
* What are causes of HCO3 loss?
What are the causes of respiratory acidosis?
Metabolic alkalosis:
* What are the causes of H loss?
* What is the cause for HCO3 intake?
What are the causes of Respiratory Alkalosis?
Mechanical Ventilation
* What is mechanical ventilation?
* What does a ventilator do?
* What does it maintain/improve?
* What does it remove?
* What does it decrease?
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.
What are the indications for mechanical ventilation?
- 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
Signs/symptoms: hypoxia, tachypnea, agonal breaths, hypoxemia, hypercapnia
What are some otehr indications for mechanical ventilation?
- 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)
What are the two types of MV? (would know invasive)
Invasive vs. Non- invasive Ventilation
* When would you consider non invasive ventilation?
* When is resp failure likely be resersible?
