Respiratory Concepts Flashcards
What is PaO2 and the normal range?
PaO2 is the amount of oxygen dissolved in plasma.
Normal Range: 80-100 mmHg
What is SaO2 and the normal range?
SaO2 is the amount of oxygen BOUND to hemoglobin
Normal: 95-99%
What is mixed venous oxygen saturation SvO2 and the normal range?
a measurement of the percentage of oxygen bound to hemoglobin in the blood returning to the heart from the entire body; measures the end-result of O2 consumption and delivery
Marker of how well O2 is being delivered to tissues
60-75%
DIRECT MEASUREMENT FROM PULM ARTERY
The brainstem (medulla), central/primary control of ventilation, senses changes in pH via PaCO2.
What happens when pH is decreased (PaCO2 increases)
A decrease in pH (Increase in PaCO2) causes increase in ventilation.
Arterial chemoreceptors in the aortic arch/carotid bodies are sensitive to PaO2 and are peripheral/secondary control–they sense PaO2 of blood. If PaO2 decreases, what happens with ventilation?
Ventilation Increases
What happens if you correct the PaO2 to normal (80-100) for chronic PaCO2 retainers?
Decrease the drive to breath.
What is the clinical indicator of ventilation? What value are you looking at?
PaCO2 (35-45)
What is the normal L/min for ventilation (minute ventilation)
~4 L/min
*Note, any INCREASE in minute ventilation = increase in WORK OF BREATHING
What is dead space ventilation?
Volume of air that does not participate in gas exchange
What are the 3 types of dead space?
Anatomic dead space (normal for everyone to have, ~2 mL/kg of Vt (tidal volume)
Alevolar dead space, which is pathologic, non-perfused alveoli (usually a blockage preventing gas exchange; think PE, which blocks blood flow and increases alveolar dead space)
Physiological dead space, which is anatomic + alveolar. Good way to assess how lungs are working
Type II pneumocytes make what?
surfactant. reduces surface tension in alveoli (prevents collapse)
Ventilation + Perfusion =
Gas exchange
What is a normal ventilation/perfusion ratio? (V/Q)
4 L ventilation/min (V) / 5 L perfusion/min (Q) = 0.8 V/Q ratio
essentially tells you how well oxygen is being exchanged in the lungs
If there is a problem with either ventilation OR perfusion there is a V/Q ____?
V/Q Mismatch
What is the treatment for a V/Q mismatch?
Give O2
Identify and treat underlying problem
What is a V/Q shunt?
movement of blood from right side of heart to left side of heart withouth getting oxygenated; venous blood moves to artieral side
Even 100% o2 will not correct hypoxemia
There are 3 types of shunts. What are they?
Normal Physiological Shunt: thesbian veins
Anatomic Shunt: think ventricular septal defect and atrial septal defect
Pathologic Shunt: ARDS!
Treatment of a V/Q Shunt?
Oxygen AND increased PEEP
A “left-shift” on the oxyhemoglobin-dissociation curve means what?
Hemoglobin “holds on” to oxygen molecules; bad for tissues; SaO2 (amount of oxygen bound to hemoglobin) is high, but is stuck and isn’t easily released
A “right shift” on the oxyhemoglobin-dissociation curve means what?
Oxygen is more easily released from hemoglobin into tissue.
Good for tissues; SaO2 is low, but O2 is more easily released into tissue
What conditions cause a shift to the left?
Alkalosis
Low PaCO2
Hypothermia
Low 2,3-DPG
What conditions cause a shift to the right?
Acidosis
High PaCO2
Fever
High 2,3-DPG
What is 2,3-Diphosphoglycerate?
Organic phosphate found in RBCs that can alter the affinity of Hgb for oxygen
What causes a decrease in 2,3-DPG, resulting in less O2 available to tissues?
Multiple blood transfusions
Hypophophatemia
Hypothyroidism
What causes an increase in 2,3-DPG, resulting in more O2 available to tissues?
Chronic hypoxemia
Anemia
Hyperthyroidsm
In respiratory acidosis, what is the primary change?
There is an increase in PaCO2, with an increase in HCO3 to compensate
In metabolic acidosis, what is the primary change?
Decrease in HCO3, with a decrease in PaCO2 to compensate
In respiratory alkalosis, what is the primary change?
Decrease in PaCO2, with a decrease in HCO3 to compensate
In metabolic alkalosis, what is the primary change?
Increase in HCO3, with a increase in PaCO2 to compensate
Acute Respiratory Failure is a rapidly occuring inability of the lungs to maintain adequate oxygenation of blood. What are the 3 types?
Hypoxemic (Type I)
Hypercapnic (Type II)
Type III: ARDS (late), COPD (late), Status asthmaticus
List some examples of Type I respiratory failure
ARDS (early)
Asthma
Atelectasis
Pneumonia
Pulmonary Edema (heart failure)
PE
Smoke inhalation
List some examples of Type II respiratory failure (hypercapnic)
CNS depression
COPD (acute exacerbation)
Sleep Apnea
Status Asmaticus (early)
Head trauma
What are clinical signs/symptoms of Acute Hypoxemic Respiratory Failure?
Tachypnea, adcentitious breath sounds, accessory muscle use
Tachyarrhythmias (early), bradyarrhythmias (late), cyanosis
Anxiety, agitation
What are some clinical signs/symptoms of Acute Hypercapnic Respiratory Failure?
Shallow breathing, bradypnea, progressive decreased LOC (lethargic, obtunded, unresponsive, stupor)
COPD includes which diseases?
Emphysema, Asthma, Bronchitis
