EXAM #2: OXYGEN THERAPY Flashcards
Generally, what is happening at the flat upper portion of the oxyhemoglobin curve?
Loading of oxygen on Hb
Generally, what is happening at the steep lower portion of the oxyhemoglobin curve?
Unloading of oxygen from Hb
What causes a right shift of the oxyhemoglobin curve?
1) Increased temp.
2) Increased 2-3 BPG
3) Increased H+
*Decreased affinity
What causes a left shift of the oxyhemoglobin shift?
1) Decreased temp.
2) Decreased 2- BPG
3) Decreased H+
4) CO
*Increased affinity
What is hypoxia?
Oxygen delivery is inadequate to meet metabolic need
What is hypoxemia?
Failure of respiratory system to oxygenate arterial blood
How is hypoxemia defined in adults? What about neonates?
- PaCO2 less than 60 mmHg, or SpO2 less than 90%
* Less than 50 mmHg in neonates
What is dysoxia?
Impaired ability for tissue to utilize oxygen
E.g. Cyanide poisoning
What does V/Q greater than 1.0 mean?
Ventilation (V) exceeds perfusion (blood flow)
What does V/Q less than 1.0 mean?
Inadequate ventilation compared to perfusion*
*This is what accounts for most hypoxemia
How does gravity affect V/Q in the apcies and bases of the lungs?
- 3 in apices
- Less than 1 in bases
What is the V/Q in the alveolar deadspace?
0
What is an anatomic shunt?
Blood flow that does NOT participate in gas exchange
E.g. Right to left shunt in a congenital heart defect
Does an anatomic shunt respond to oxygen therapy?
NO
What is alveolar shunt?
Areas of poor ventilation in relation to perfusion
What are the ominous signs of severe hypoxia?
1) Cyanosis
2) Bradycardia/ arrhythmia
3) Hypotension
4) Somnolence
In regards to FiO2, how do oxygen percentage and partial pressure change with increased elevation?
- Percentage is ALWAYS 21%
- Partial pressure is proportional to atmospheric pressure
*Thus, increased elevation = decreased partial pressure of oxygen
With exposure to 100% O2 for 0-12 hours, what are the physiologic responses?
- Tracheobronchitis
- Substernal chest pain
With exposure to 100% O2 for 12-24 hours, what are the physiologic responses?
Decreased vital capacity
With exposure to 100% O2 for 24-30 hours, what are the physiologic responses?
- Decreased lung compliance
- Increased A-a gradient
With exposure to 100% O2 for 30-72 hours, what are the physiologic responses?
Decreased diffusion capacity
What two organs are primarily affected by oxygen toxicity?
Lungs and CNS
What causes the damage seen in oxygen toxicity?
Oxygen free radicals that induce an inflammatory reaction
Describe the physiologic mechanism of oxygen-induced hypoventilation in a COPD patient.
- COPD= blunted CO2 response
- Respiratory drive is based on HYPOXIA
- High blood O2 suppresses ventilatory drive
What is retinopathy of prematurity?
Blindness and retinal detachment associated with prematurity and oxygen toxicity
What causes retinopathy or prematurity?
1) Excessive oxygen causes retinal vasoconstriction
2) New blood vessels form and increase in number
3) Hemorrhaging of new vessels causes scarring
What is absorption atelectasis?
- Oxygen therapy replaces a large volume of nitrogen in the lung with oxygen
- Oxygen is then absorbed into the blood, reducing the volume of the alveoli
- Alveolar collapse results i.e. absorption atelectasis.
What are the indications for hyperbaric oxygen therapy?
1) Air embolism
2) CO poisoning
3) Wound therapy
If you use a simple oxygen mask, what flow rate is required as a minimum?
5 L/min
What is the minimum flow rate for a rebreather mask?
8 L/min
*Note that this mask has 2x ports that block inhalation of room air vs. a partial that only has 1x
When do you need to ensure that supplemental oxygen is humidified?
Anytime you’re bypassing the nose and mouth
