Pulmonary Flashcards
Central control: brain stem
Senses pH, decreased pH > ventilation is stimulated > increased RR
Peripheral control: PaO2 sensors in aortic arch
Senses PaO2 > decrease in PaO2 (hypoxemia) > ventilation is stimulated > increased RR
How to know if ventilating normally?
PaCO2! NOT PaO2
Minute ventilation
Tidal volume x RR
Normal is approx. 4L/minute
Increased minute vent = increased WORK OF BREATHING
Primary muscle of ventilation
Diaphragm!
Anatomic dead space
Doesn’t participate in gas exchange
Dead space is approx. 2ml/kg of Vt
Alveolar dead space
Pathologic, non-perfused alveoli (PE)
Physiologic dead space
Anatomic + alveolar dead space
Perfusion def
Movement of blood past alveoli
Normal ventilation/perfusion ratio
4L ventilation/min
5L perfusion/min
Ideal lung unit = 0.8 VQ ratio
Can be decreased by PE or low CO
How to position R lung PNA
GOOD LUNG DOWN
Treatment of VQ mismatch
Give O2, treat cause
Lung shunt such as ARDS
An extreme VQ mismatch, even on 100% O2 will not correct hypoxemia
Treatment: give 100% O2, PEEP
Shunt def
Movement of blood from R side of heart to L without oxygenation
Normal physiologic shunt
Thebesian veins of the heart empty into L atrium
Anatomic shunt
VSD or ASD
Pathologic shunt
ARDS! Blood goes through without being oxygenated resulting in refractory hypoxemia
PEEP
Prevents expiratory pressure from returning to zero, by keeping exp. pressure positive it
- decreases surface tension of alveoli
- increases alveolar recruitment
- increases driving pressure, extends time of gas transfer and allows decrease in FiO2
Left shift of oxyhemo dissociation curve
Alkalosis
Low PaCO2
Hypothermia
Low 2,3-DPG
SaO2 high but O2 stuck to hgb > BAD
Right shift of oxyhemo dissociation curve
Acidosis (high H+)
High PaCO2
Fever
High 2,3-DPG
Good for tissues, SaO2 low but O2 easily released
What is 2,3-DPG?
Organic phosphate in RBCs that alters affinity of hgb for oxygen
Decreased 2,3-DPG
Multiple blood transfusions
Hypophosphatemia
Hypothyroidism
Less O2 available to tissues
Increased 2,3-DPG
Chronic hypoxemia
Anemia
Hyperthyroidism
More O2 available to tissues