49: Therapeutic Gases - Duric Flashcards
O2 delivery to the tissues is inadequate to meet metabolic need
hypoxia
failure of the respiratory system to oxygenate arterial blood or a decreased carrying apacity of the blood
hypoxemia
3 causes of hypoxia
- hypoxemia
- impaired blood flow
- dysoxia
inability of the cardiac system to adequately deliver blood to the tissues
impaired blood flow
impaired ability for tissue to utilize oxygen
dysoxia
impaired ability of oxygen to diffuse across the alveolar-capillary membrane
v/q mismatch
anatomic shunt example
blood bypasses lungs like in bronchial circulation
cyanide posioning is an example of …
dysoxia
cellular use of oxygen is abnormally decreased
primary response to hypoxia
increased cardiovascular workload
___ of air at sea level is oxygen
21%
_____ of room air is _______ but partial pressure is proportional to atmospheric pressure
FiO2
constant
most common therapy to treat hypoxia/hypoxemia
oxygen therapy
indications for adult and children hypoxemia oxygen treatment
PaO2 less than 60 torr
SaO2 less than 90%
indications for neonate hypoxemia treatment
PaO2 less thann 50 torr
SaO2 less than 88%
pathological responses to oxygen
- damage to the capillary endothelium
- thickening of the alveolar-capillary membrane
- alveolar exudate and consolidation causing physiological shunting
- at end stage pulmonary fibrosis and hypertension
why does oxygen-induced hypoventilation sometimes happen?
central response to CO2 is blunted –> primary stimulus to breathe is oxygen deprivation (hypoxemia) –> high blood O2 levels suppress peripheral chemoreveptors and depress ventialtroy drive
condition of the eye affecting premature/low-birth weight infants
retinopathy of prematurity
excessive blood-oxygen levels produce retinal vasoconstriction causing necrosis of the blood vessels –> new vessels form and increase in number –> hemorrhage of these new vessels causes scarring behind the eye’s retina leading to retinal detachment and blindness
describe absorption atelectasis
nitrogen, the primary gas in teh alveoli, is “washed out” by oxygen
results in increased physiologic shunt because alveoli are perfused but not ventilated
for every liter increase, increase FiO2 __ %
4%
ex 1L = 24% or FiO2 0.24
2L = 28 etc…
indications for hyperbaric oxygen therapy
air embolism
carobon monoxide poisoning
wound therapy
makes more oxygen available in the blood and not just on hemoglobin
less than ___ helium is not therapeutic
60%
delivered in parts per million up to 80ppm - standard dose is 20 ppm
how does helium-oxygen therapy work?
low-density gas which lowers the work of breathing - promotes laminar flow in large airways
FDA approved indication for nitric oxide therapy
persistent pulmonary hypertension of the newborn
treats by dilating the pulmonary blood vessels
