1. Example: if you have metabolic alkalosis (increase in bicarb: which is in the numerator), then have to increase denominator (pCO2) to keep it normal, therefore, compensation is due to respiratory (pCO2) acidosis. A nice way of memorizing it is what is the opposite of
metabolic? Respiratory and what is the opposite of acidosis? Alkalosis, and vice versa. 2. Example: if you have metabolic acidosis (decrease bicarb) what do we have to do with the pCO2? We have to get rid of it. If we decrease the nominator, we have to decrease the dominator in order for the equation to stay the same. Therefore, we have to blow off the CO2 (hyperventilation).
3. Ventilation is a CO2 term!
Hyperventilation = Increase in respiratory rate allows for the blowing off of CO2, therefore results in respiratory alkalosis. For the treatment of respiratory alkalosis is to give the pt a paper bag and ask to breath in it, b/c then they are re-breathing their own CO2.
Hypoventilation = Decrease in respiratory rate allows for the retention of CO2, therefore results in respiratory acidosis.
Full compensation does not exist; you never bring back the pH to the normal range. There is one exception: chronic respiratory alkalosis in high altitude; ie mountain sickness (ie peru). C. Respiratory conditions: acidosis and alkalosis
1. Things that deal with CO2:
a) Respiratory center is in medulla oblongata, which controls the breathing rate b) Upper airways – if obstructed, there will be a problem getting rid of CO2. c) Chest bellows – most imp muscle of respiration is diaphragm. On inspiration: the diaphragm goes down, the negative intrathroacic pressure increases, and air is sucked into the lungs and blood is sucked into the right side of the heart (this is why neck veins collapse on inspiration). Negative vacuum sucks blood and air into your chest. On expiration, there is a “+” intrathrocic pressure, pushing things out. It helps the left heart to push blood out and it also helps the lungs by pushing out air.
2. Examples:
(a) Barbiturates or any drug that depresses the respiratory center will leads to respiratory acidosis
(b) CNS injury to medulla oblongata – resp acidosis
(c) Anxiety = MCC resp alkalosis. When you take a test, sometimes you feel strange, and get numb and tingly, especially around mouth and on the tips of fingers, and become twitchy (b/c you are in tetany) its all caused by being alkalotic and ionizing calcium level gets lower and you really are getting tetany. Therefore you become
twitchy and paresthesias (ie carpal pedal sign or trousseau’s sign are both signs of tetany). All due to tetany b/c of breathing too fast from anxiety.
(d) Pregnant woman have resp alkalosis b/c estrogen and progesterone over stimulate the respiratory center. Located in the lungs are spider angiomas due to AV fistulas related to high estrogen, therefore clear more CO2 per breath than a normal woman. A lot of shunting occurring within lungs. These spider angiomas go away after delivery of the baby.
(e) Endotoxins over stimulate the system. All pts in endotoxic shock have resp alkalosis. They are also in anaerobic metabolism, producing lactic acid, therefore are also in
metabolic acidosis. Therefore, endotoxic resp alkalosis due to overstimulation, and metabolic acidosis due with normal pH.
(f) Salicylate overdose – overstimulate resp center, leading to resp alkalosis. Salicylic acid is an acid, hence metabolic acidosis, and pH will be normal b/c they balance e/o out. (Tinnitus in salicylate OD – also a MIXED disorder!)
(g) 6 y/o child with inspiratory strider – do a lateral x-ray, and see thumbprint sign, with a swollen epiglottis. The diagnosis is acute epiglottitis, due to H. influenza; vaccination has decreased incidence, hence you don’t see any ids with H. meningitis b/c of the vaccination. The MC of meningitis in 1 month – 18 yrs = N. meningitis.
(h) 3 month old – croup, a larygiotracheobronchitis dz due to parainfluenza virus. Want to do a lateral x-ray and see a steeple sign. Where is the obstruction in croup? Trachea (i) Pt shoving food in their mouth (café coronary) – Heimlich maneuver; if they can talk, leave alone and let them cough it out.
(j) Diaphragm innervated by the phrenic nerve – ie erb Duchene palsy, with brachial plexus injury, and child has resp difficulty, and diaphragm on right side is elevated. Paralysis of the diaphragm will lead to increased CO2.
(k)Lou Gehrig’s dz – amyotrophic lateral sclerosis dz, a LMN’s and UMN’s gone therefore cannot breath b/c no innervation to the diaphragm (ie diaphragm and intercostals are paralyzed)
(l)Guillain-Barre – ascending paralysis in a patient who a week ago had a respiratory infection. The spinal fluid shows increased protein, slight increase in lymphocytes, and a gram stain negative. Dz: Guillain-Barre, demyelinating dz
(o) Polio – destroys LMN’s and eventually UMN’s. Therefore, anything that paralyzes muscle of resp will lead to resp acidosis.
(p) LUNGS: obstructive and restrictive lung dz’s
Obstructive lung dz – problem getting air out, compliance increased and elasticity is decreased, therefore, have a resp acidosis.
In restrictive lung dz, ie Sarcoidosis and pneumonocionioses, there is a problem in getting air in therefore has a resp alkalosis (?)
Day 2
Caisson’s Disease –Underwater: for every 30 ft, increase 1 atm, (ie 760 at level, but 30 ft lower it will be 2 atm); the reverse is true when you go to high altitudes – ie at top of mt everst, the atmospheric pressure is 200 atm; still breathing 21% O2; breathing the same, but atmospheric pressure is different, depending on where you are.
Formula for calculating: alveolar O2 = (0.21 x atmospheric pressure) – PCO2 / .8
High Altitude: (.21 x 200) – 40mmHb/.8 = 2mmHg of air in alveoli, therefore will have to hyperventilate at high altitudes, b/c lower pCO2= increased PO2 (you HAVE to hypverventilate otherwise you die).
However, when you go under, the atm pressure increases, and the nitrogen gases are dissolved in your tissues, leading to an increase in pressure. Ie 60 ft below, want to get up fast; like shaking a soda bottle; as you ascend, the gas comes out of fat in bubbles; the bubbles get into tissues and BV’s; this is called the bends; leads to pain, and quadriplegia, loss of bladder control. Rx = hyperbaric O2 chamber.
CHAPTER 4: NUTRITION