Oxygen Therapy

Question 1

Oxygen Delivery Equation

Answer 1

DO2 = Cardiac Output x Arterial O2 Content

Question 2

Causes of oxygen delivery failure

Answer 2

hypotension, acidosis, coagulopathy

Question 3

Oxygen Use Equation

Answer 3

VO2 = Cardiac Output x (O2a - O2v)

Question 4

Normal Oxygen Extraction Ratio

Answer 4

about 25%

Question 5

Surgical patients are at ____ risk for hypoxemia/hypoxia

Answer 5

increased

Question 6

Hypoxemia definition

Answer 6

deficiency of O2 in blood

Question 7

Hypoxia definition

Answer 7

O2 delivery to tissues not sufficient to meet metabolic demand

Question 8

What is our goal in terms of oxygen therapy?

Answer 8

prevention and correction of hypoxemia and tissue hypoxia

Question 9

Hypoxic hypoxia

Answer 9

overdose, COPD, emphysema, asthma - shunting, pulmonary diffusion defects

Question 10

Circulatory hypoxia

Answer 10

decrease CO d/t congenital heart defects

Question 11

Hemic hypoxia

Answer 11

decreased Hgb, anemia, carboxyhemoglobin, methemoglobin

Question 12

Demand hypoxia

Answer 12

fever, seizure, MH

Question 13

Histotoxic hypoxia

Answer 13

inability of cells to utilize O2, cyanide toxicity

Question 14

Hypoxia signs and symptoms

Answer 14

vasodilation, tachycardia, tachypnea, cyanosis, confusion, lactic acidosis

Question 15

Possible methods to improve oxygenation

Answer 15

increase VE, increase CO, increase O2 carrying capacity, optimize V/Q relationship, decrease O2 consumption, increase FiO2

Question 16

Nasal Cannula

Answer 16

flow rates 1-6 L/min

FiO2 increases about 4% per L/min

Question 17

Simple face mask

Answer 17

FiO2 40-60%
minimum 6 L flow required to prevent rebreathing
(or patient’s minute ventilation - want to be higher than that)

Question 18

Face masks with reservoirs

Answer 18

FiO2 60-100%

Question 19

Venturi mask

Answer 19

more precise FiO2 24-50%

Question 20

What law is associated with venturi masks?

Answer 20

Bernoulli

Question 21

oxygen toxicity

Answer 21

high FiO2 over long periods

• decreased ciliary movement
• alveolar epithelial damage
• interstitial fibrosis
  safe: 100% for up to 10-20 hours
  toxic: 50-60% for more than 24-72 hours

Question 22

Absorption atelectasis

Answer 22

nitrogen is replaced by oxygen
under ventilated alveoli have decreased volume d/t greater uptake of oxygen
increases pulmonary shunting

Question 23

induced hypoventilation

Answer 23

chronic CO2 retainers rely on hypoxic drive
peripheral chemoreceptors are triggered by hypoxemia
increased O2 can lead to hypoventilation

Question 24

Fire hazard of O2

Answer 24

o2 supports combustion

use caution with head and neck cases

Question 25

retinopathy

Answer 25

O2 therapy in neonates that can lead to vascular proliferation, fibrosis, retinal detachment, blindness
at risk: <36 week gestation, weight < 1500gm, up to 44 weeks
Safe: PaO2 60-80mmHg

Question 26

Hypercapnia

Answer 26

increased CO2 >45 mmHg

causes: increased CO2 concentration, increased CO2 production

Question 27

Causes of hypercapnia

Answer 27

increased alveolar dead space, decreased alveolar ventilation

Question 28

clinical manifestations of hypercapnia

Answer 28

vasodilation of peripheral vessels, indirectly increases HR after catecholamine release, headache, N/V, sweating, flushing, shivering, restlessness

Question 29

considerations for hypercapnia

Answer 29

regulation of ventilatory drive, cerebral blood flow, depression of smooth/cardiac muscle, increased catecholamine release, vasodilation (initially) then vasoconstriction (catecholamine release), increased RR, increased PVR (pulmonary)

Question 30

one treatment for hypercapnia

Answer 30

increase minute ventilation

Question 31

hypocapnia

Answer 31

CO2 <35 mmHg
iatrogenic cause
manifestations: decrease CBF, decrease CO, coronary constriction, hypoxemia
treat: decrease minute ventilation