Pulmonary gas exchange and transport Flashcards
What is hypoxia and hypercapnia?
What are the three variables of arterial blood that the body responds to in order to avoid hypoxia and hypercapnia?
-Oxygen-ATP production
-Carbon dioxide: CNS depressant/acid prescursor
-pH: denaturing of protein
What are the systemic normal blood values in pulmonary medicine?
What are the influences of alveolar gas exchange?
Gas diffuses down partial pressure gradients
-#1 revolves around concentration gradient
What are the two causes of low alveolar PO2 assuming perfusion remains constant?
- Insipired air has low O2 content:
-Atmospheric pressure: PO2 at sea level is about 160mmHg, in Denver (about 1600m above) PO2 is about 132mmHg - Alveolar ventilation:
-If atmospheric PO2 normal and alveolar PO2 still low then it must be a ventilation issue (hypoventilation)
-Increased airway resistance, decreased lung compliance, or CNS issue (resp. control center) decreased rate and/or depth of breathing
What is usually the cause of hypoxia if perfusion remains constant and hypoventilation or alteration in atmospheric PO2 are not the problem?
-Lies within the gas exchange between the alveoli and blood
-Blockages such as increased surfactant, blood clots, etc. are factors that can negatively impact gas exchange
What is diffusion and what is going to affect the random movement of gas molecules between alveoli and capillaries?
What is the main determinant of diffusion in a healthy individual? What are pathologies that cause hypoxia?
How does gas solubility affect diffusion?
Oxygen doesn’t dissolve well in liquid
How can you calculate gas transport in the blood?
-More than 98% of oxygen in blood is bound to hemoglobin in red blood cells, less than 2% in dissolved plasma
-Four oxygen binding sites in Hb, one for each heme group
How does oxygen binding obey the las of mass action?
How does PO2 determine Oxygen-Hb binding?
Describe oxygen transport
Alveoli -> plasma -> RBC
-O2 moves down pressure gradient
-Hb in RBC binds oxygen, decreasing PO2 and creating a cycle of incoming O2 until Hb is completely saturated
-As PO2 decreases in RBC due to O2 moving to plasma then to the cells, Hb reversibly binds and releases more oxygen
What is the percent saturation of Hb in alveoli vs resting cells?
What is the effect of pH on Hb affinity for O2?
What is the effect of PCO2 on Hb affinity for O2
What is the effect of temperature on Hb affinity for O2?
What is the effect of 2,3-BPG on Hb affinity for oxygen?
What is the difference between maternal and fetal hemoglobin?
Fetal: two alpha, two gamma globin subunits (vs two alpha, two beta in maternal)
-Curve is shifted left and higher because of increased binding affinity of oxygen in hemoglobin
Briefly describe the importance of CO2 transport
-Elevated PCO2 causes acidosis, low pH leads to interruptions in H bonds and denaturing of proteins
-Abnormally high PCO2 depresses the CNS causing confusion, coma or even death
What are the 3 ways CO2 is transported?
Explain in detail CO2 transport from the cell to alveoli
what is the purpose of converting CO2 to HCO3- (bicarbonate)
what are the mechanisms that prevent equilibrium of CO2 converting to HCO3 and H+ and their purpose
How does Hb bind CO2?
Describe CO2 removal at the lungs
Describe regulation of ventilation
What is the current model for control of respiraton?
What is the function of nucleus tractus solitaris (NTS)
What is the function of the pontine respiratory group? (PRG)
What is the function of the ventral respiratory group? (VRG)
Explain neural activity during quiet breathing
What are peripheral chemoreceptors and what influences them?
Describe the function of glomus cells
Explain the functions of central chemoreceptors
Explain how the body reacts to decreased arterial O2
Explain how the body reacts to increased arterial H+ independant of CO2
Explain how the body reacts to increased arterial CO2
How do protective reflexes guard the lungs?
Why does ventilation rate jump as soon as exercise begins, despite the fact that neither arterial PCO2 nor PO2 has changed?
-Suggests there is a feedforward component to the ventilatory response
-Proprioceptors in muscles and joints
