Pulmonary lecture Diagnostics Flashcards
ABG
pH, PaCO2, PaO2
Allen test
to see if the ulnar and radial artery are not occluded by a thrombus
normal pH
7.4
normal PaCO2
35-40
-represents ventilatory problems
normal PaO2
around 100
-represents oxygenated problems
acidemia pH
blood pH <7.35
acidosis
primary physiologic process that, occurring alone, tend to cause acidemia.
- example: metabolic acidosis from decreased perfusion (lactic acidosis)
- respiratory acidosis from hypoventilation
Alkalemia pH
blood pH >7.45
alkalosis
primary physiologic process that occurring alone tends to cause alkalemia.
- examples: metabolic alkalosis from excessive diuretic therapy
- respiratory alkalosis acute hyperventilation
primary acid base disorder
one of the four acid base disturbances that is manifested by initial change HCO3 or PaCO2.
compensation
change in HCO3 or PaCO2 that results from the primary event
respiratory alkalosis
- first change is a lowering of PaCO2-> elevated pH
- compensation is secondary by kidneys of lowering bicarbonate-> reduction in bicarbonate results in metabolic acidosis
respiratory acidosis
- first change is elevation of PaCO2-> decrease pH
- compensation: retention of bicarbonate from kidneys-> metabolic alkalosis
metabolic acidosis
- first change is lowering HCO3-> decreased pH
- Compensation: hyperventilation (lower PaCO2)
metabolic alkalosis
- first change is elevation of HCO3-> increased pH
- compensation: hypoventilation (increase PaCO2), want to bring pH back down
anion gap
Na-(CL+CO2)
metabolic acidosis: increased anion gap is from
lactic acidosis, ketoacidosis, drug poisoning,
“MULEPAKS”
metabolic acidosis: normal anion gap is from
diarrhea, some kidney problems
“HARDUP”
metabolic alkalosis anion gap
chloride responsiveness: contraction alkalosis, diuretics, corticosteroids, gastric suctioning, vomiting
chloride resistance
respiratory acidosis
(increased PaCO2, decreased pH)
- CNS depression
- chest bellows dysfunction (MA, GB)
- disease of lungs (obstructive), severe asthma, severe pulmonary edema
respiratory alkalosis
(decreased PaCO2, increased pH) hypoxemia anxiety sepsis acute pulmonary insult (PE, pneumonia, pulmonary edema)
patient with pH>7.4, with PaCO2 >40
either Met. Alka with respiratory compensation or
met. Alka and a respiratory acidosis
FiO2
fraction of inspired oxygen
SpO2
pulse Ox or bound oxygen (dissolved)
A-a gradient
alveolar oxygen-Arterial oxygen
abnormal A-a gradient
elevated when gas diffusion is impaired (lung problem)
expected normal A-a gradient
(patient age/4) +4
PiO2
pressure inspired oxygen in trachea
SaO2
bound oxygen %
for most pulmonary disease, the A-a gradient number will get
bigger
-sensitive for PE
oxygenation failure
to quantify the degree of diffusion impairment or hypoxemia (low oxygen []) it is important to know two addition relationships:
- oxygen saturation to the dissolved oxygen []
- dissolved oxygen concentration to the inspired oxygen c[]
PaO2 of 60 mmHg
saturation of 90%
-want to be at 90% or above
causes Hb to hold onto O2
-leftward shift alkalosis hypothermia low PCO2 Low 2,3-DPG
causes Hb to release of O2
-rightward shift High PCO2 fever acidosis high 2,3-DPG
normal PaO2:FiO2 on room air
100: 21%= 475 (ratio)
severity of diffusion impairment increases, what happens to PaO2:FiO2
ratio decreases
shortcut for calculating PaCO2:FiO2 ration
PaO2 is about 5X FiO2
decreased V/Q
areas of lung that are better perfused than ventilated
-shunt
increased V/Q
areas are better ventilated than perfused
-dead space
highest pressure zone of lung
lowest part of lung
- zone 3: Pa>Pv>PA (alveolar pressure, doesn’t interrupt flow)
- shunt happens hear
zone 2 of lung
Pa>PA>Pv
zone 1 of lung
PA>Pa>Pv
- not able to pump the blood all the way up to the lung
- alveolar pressure collapses capillaries, not able to be perfused
what can cause an increased V/Q (increased dead space)
- PE
- emphysema
decreased V/Q (shunt)
- emphysema (non-function alveoli)
- fibrosis (poor diffusion of air)
- secretions (blocks diffusion of air)
shunts occur when
-venous blood mixes with arterial blood bypassing oxygenation
extra pulmonary, you see
right to left cardiac shunts
-example: T or F
intra pulmonary, you see
blood is transported thru lungs without taking part in gas exchange
-example: atelectasis, pneumonia, hepatopulmonary syndrome, Anomolous venous return
