Gas exchange and gas transport Flashcards
is oxygen very soluble in plasma
no
what is oxygen bound to in the blood
It is bound to haemoglobin (Hb) to form oxyhaemoglobin
when does the oxygen dissociation curve flatten
at higher levels of saturation
How does Hypoventilation/hyperventilation affect arterial O2 content
little change
what is P50
P50 is the partial pressure of oxygen at which 50% of Hb is saturated
what does the affinity of Hb for Oxygen depend on
pH, CO2 partial pressure and temp
what does an increase in the concentration of 2,3-DPG result in
- a shift to the right
- 2,3-DPG promotes hemoglobin transition from a high-oxygen-affinity state to a low-oxygen-affinity state
what happens if the the oxygen dissociation curve moves to the right
if the curve moves to the right means that the affinity is decreased so that there is a larger tendency to release oxygen rather than keep it to itself
what is the oxygen cascade
the oxygen cascade is the falling pressure of oxygen from air to mitochondria
what happens to air in upper conducting airways
it is humidified and does not participate on gas exchange
what does water vapour do to the ppO2
decreases
how does oxygen get transferred from the air to the mitochondria
From air → conducting airways → alveoli → interstitial space containing fluid → across the interstitium → red blood cell → bind to Hb → tissue fluid → across cell membrane → mitochondria
describe what happens to HB when oxygen binds to form oxyhaemoglobin
it is saturated
what is it called when deoxygenated Hb contains no o2
desaturated
what does oxygen delivery (DO2) depend on
Oxygen delivery (DO2) depends on cardiac output (CO) and arterial oxygen content (CaO2)
what is the calculation for oxygen delivery (DO2)
- DO2 = CO x CaO2
- CO = heart rate x stroke volume
what is the equation for oxygen consumption (VO2)
- Oxygen consumption (VO2) = amount of O2 consumed/minute
- VO2 max = CO x (CaO2 – CvO2)
what does the ratio of oxygen delivery and oxygen consumption in a healthy person
At rest in healthy person, DO2 > VO2
how is CO2 carried in the blood
- 30% of CO2 carried as carbaminohaemoglobin
- 10% of CO2 is carried dissolved in plasma
- 60% of CO2 is transported as bicarbonate ions
- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 –
Enzyme: carbonic anhydrase
- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 –
what are some characteristics of H+ in the blood
- there is a high concentration of H+ in RBC
- the membrane is impermeable to H+
what is the Haldane effect
- when Hb becomes deoxygenated in tissues it can take up more CO2
- in alveoli, oxygenation of Hb results in the release of CO2
what is respiratory acidosis
bicarbonate and deoxygenated Hb bind and release CO2 according to the pH
what is the respiratory quotient
this is the ratio of CO2 production to O2 consumption
what is PAO2, PACO2, PaO2
- PAO2 = alveolar partial pressure of oxygen
- PACO2 = alveolar partial pressure of carbon dioxide
- PaO2 = arterial partial pressure of oxygen
what is acinus
a unit of respiratory function distal to the terminal bronchioles comprising of the respiratory bronchioles, alveolar ducts and alveoli
what is it called when many acinar are together
pulmonary lobule
what are pulmonary lobules seperated by
septae
what is the importance of structural interdependence in acinar
prevent collapse of an individual unit
what does the number and size of alveoli depend on
No of alveoli depends on height of individual, size depends on volume of air in lungs
what are alveoli lined by
thin layer of unciliated squamous epithelial cells
where are type 1 pneumocytes
rest on the Basement Membrane and interface closely with capillary membrane = alveolar-capillary unit
what is in the interstitial space
Interstitial space contains pulmonary capillaries, elastin and collagen fibres
where are type 2 pneumocytes
- found at the junction between alveoli and produce surfactant which reduced surface tension
what are club cells/ bronchiolar exocrine cells
Club cells (Bronchiolar exocrine cells) in alveolar fluid produce glycosaminoglycans
what is the insterstitium
The Interstitium is a microscopic space between the alveoli and the pulmonary capillary wall
what are factors that affect diffusion
- thickness of membrane
- surface area of membrane
- solubility of gas in the membrane
- molecular weight of gas
how can movement of O2 be estimated
The amount of CO transferred across/minute is estimated using a single-breath method-This is called TLCO/DLCO
what is TLCO reduced by
- TLCO will be reduced in conditions that affect:
- The surface area available for gas exchange = emphysema
- Thickening of the membrane = pulmonary fibrosis
what is carboxyhaemoglobin (COHb)
is formed when Carbon Monoxide (CO) binds to Hb
does haemoglobin have a higher affinity for O2 compared to CO
no
what are the clinical symptoms for Co poisoning
headaches, N+ V, dizziness, lethargy; weakness, confusion, coma and death within hours
what is methaemoglobin (MetHb)
Methaemoglobin (MetHb) arises when the Iron component in haemoglobin is oxidised so that it is in the ferric state (Fe3+)
what is the binding like for MetHb
MetHb is unable to bind O2 and therefore cannot participate in O2 transport
what are the causes of MetHb
Congenital/idiopathic methaemoglobinaemia
Infants become cyanosed
Acquired MetHB: post exposure to chemicals (anaesthetics, nitrobenzene, specific antibiotics )
what is Congenital/idiopathic methaemoglobinaemia
this genetic defect leads to a deficiency of a certain enzyme, or protein. This protein is responsible for converting methemoglobin to hemoglobin
what is cyanosis
happens when there’s not enough oxygen in your blood, or you have poor blood circulation
