oxygen therapy Flashcards
oxygen
oxygen doesn’t make breathing easier. but it does increase oxygen levels
normal in blood can range from 92 to a 100 percent O2.
-PaO2- what drives the oxygen into the blood so the bigger Pao2 the more you have into your blood which then bind to hb.
what is oxygen good for ?
Mitochondial metabolism (ATP) (cellular respiration)
Angiogensis - Hypoxia promotes angiogensis but this effect is enhanced by episodic oxygen therapy and hyperbarics,
Vasoactive – causes both vasodilation and vasoconstriction depending on site and concentration.
(In the lung however vessels dilate in response to oxygen rich alveoli. )
Immune function - suppresses anaerobic bacteria, supports proper function of WBC
hypoxemia
too little O2 in the blood
you can have hypoxia without hypoxemia but if you have hypoxemia it will always lead to hypoxia
hypoxia
inadequate oxygen for proper cellular metabolism
not enough to support very vigorous exercise- muscles get tired
-When hypoxia exists, cells activate anaerobic metabolism
This produces dangerous waste products such as lactate
causes of hypoxemia
- decrease in oxygen alveolar tension.
- increase altitude (less ATM)
- inadequate ventilation (apnea or hypopnea)
- shunt
- dead space
hypoxemia via shunt
blood but no air- this is due to no alveolar oxygen tension at all, but capillaries are still passing blood. pick up almost zero oxygen
(perfusion without ventilation)
hypoxemia via deadspace
Air but no blood
Your lungs work fine but the capillaries around the alveoli are either constricted or occluded. (ventilation but no perfusion)
body response to hypoxemia
chemoreceptor detect low levels of oxygen in the blood., They activate this responses,
increase minute ventilation (RR or Vt)
-increase cardiac output (pump more blood)
-increase red blood cell production, this is a slow process and only happens on chronic hypoxemia (COPD) (ASBESTUSIS)
signs of hypoxemia
cyanosis- blue arrhythmias confusion or disorientation polycythemia (in chronic hypoxemia)-increase in RBcs lethargy
four diff types of hypoxia
hypoxic- from hypoxemia
anemic - not enough RBCs to carry O2 to tx or there is something wrong with the Hb (dyshemoglobins)
circulatory- heart isn’t working well. (does not respond to oxygen therapy)
histotoxic- cyanide poison(does not respond to O2 therapy)
way to asses need for O2 therapy
laboratory measure- invasive or noninvasive (pulse oximetry or ABG)
clinical problem or condition
symptoms of hypoxemia(finger clubbing)
contraindications for O2 therapy
use of drugs which increases sensitivity to oxygen and oxygen radicals, bleomycin
demonstrated O2 sensitivity in end stage COPD
oxygen toxicity
Results from breathing in oxygen at elevated partial pressures
This causes release of oxygen free radicals and oxidative damage to vital organs and cells
Mucosal inflammation and cilia inactivation
Also causes red blood cell destruction (hemolysis)
Although not truly oxygen toxicity, breathing in elevated amounts of oxygen can also lead to nitrogen washout atelectasis
-Pulmonary oxygen toxicity occurs at a partial pressure of 375 mmHg which is roughly equivalent to an FiO2 of 0.50, after exposure at this level for roughly 14 hours
pathophysiology
High PO2 damages capillary endothelium
Followed by interstitial edema & AC membrane thickening
Type I cells are destroyed (cells that create new lung tissue, gas exchange cells)
Type II cells proliferate (trigger inflamax response)
how much is too much O2?
> 50% for very extended times
PO2 the less time it takes
Use the lowest FiO2 possible to maintain adequate tissue oxygenation
