Pulmonary Flashcards
What is the primary control of ventilation?
Central control from the brainstem. Senses blood pH & decrease in pH stimulates ventilation (increase in rate &/or depth of breathing).
What is the secondary control of ventilation?
Peripheral control from PaO2 sensors in the aortic arch. Decrease in PaO2 (hypoxemia) results in increase rate &/or depth of breathing.
*This is why chronic CO2 retainers rely on mild hypoxemia.
What is the clinical indicator of ventilation?
PaCO2 (Not PaO2)
- Tidal volume (Vt) x respiratory rate.
- Normal is 4L/min
- Increase = increase work of breathing
Minute ventilation
What is the primary muscle of ventilation?
The diaphragm
What is the optimal position for ventilation?
Upright sitting position. The worst is flat on their back.
Volume of air that does not participate in gas exchange.
Dead space ventilation
~ 2ml/kg of Vt
Everyone has this, it is normal. No gas exchange at level of nose down to alveoli.
Anatomic dead space
Pathologic, non-perfused alveoli, PE.
Alveolar dead space
Anatomic dead space + alveolar dead space
Physiological dead space
Results in increase alveolar dead space! A clot in the pulmonary circulation.
Pulmonary embolism
Movement of blood past alveoli
Pulmonary perfusion
What is normal ventilation/perfusion ratio?
4L ventilation/min (V) / 5L ventilation/min (Q)
Ideal lung unit?
0.8 ratio
What lung do you want down?
The GOOD one
What is the treatment for VQ mismatch?
Give oxygen & treat underlying problem
An extreme V/Q mismatch that even 100% FiO2 will not correct.
-Example: ARDS.
Shunt
Treatment: Give 100 FiO2 & increase PEEP
Thebesian veins of the heart empty into the left atrium. This is why the normal oxygen saturation on room air is 95% to 99% & cannot be over 100% on RA.
Normal physiological shunt
What type of shunt is ventricular or atrial septal defects?
Anatomic shunt
Blood goes through lungs but does not get oxygenated resulting in ____?
Refractory hypoxemia.
*This is what happens in ARDS & is a pathologic shunt
Extends time of gas transfer, increases driving pressure, decreases surface tension of alveoli (preventing atelectasis)
PEEP
Delivery of O2 at meet tissue demands at the cellular level.
Adequate oxygenation
Normal arterial oxygen (PaO2)?
80-100 mmHg on RA
Normal mixed venous (SvO2)?
60-75%
What is the most sensitive indicator of oxygenation at the cellular level?
Mixed venous oxygen saturation
Normal oxygen content (CaO2)?
15-20 ml/100 ml blood
*Important when addressing anemia
Normal oxygen delivery (DO2)?
900-1100 ml/min
*Seen with pump problems
Normal oxygen consumption utilization (VO2)?
250-350 ml/min
*Low with septic shock
Normal alveolar-arterial (A-a) gradient?
<10 mmHg
*Indicates if gas transfer is normal and if not, how bad the V/Q mismatch or shunt is.
When do cells begin to have difficulty maintaining aerobic metabolism?
When PaO2 is less than 60
When SpO2 is at 90%, what is PaO2?
60%
What way does the oxyhemoglobin dissociative curve shift when hemoglobin holds onto oxygen?
Shifts to the left
What way does the oxyhemoglobin dissociative curve shift when hemoglobin releases oxygen?
Shifts to the right
What causes the oxyhemoglobin dissociative curve to shift left?
Alkalosis (low H+), low PaCO2, hypothermia, low 2,3-DPG. Bad for patients even though SaO2 high because it’s stuck to hemoglobin.
What causes the oxyhemoglobin dissociative curve to shift right?
Acidosis (high H+), high PaCO2, fever, high 2,3-DPG. Good for tissues even though SaO2 low.