gas exchange Flashcards
what are anabolic reaction
actively transporting ions and maintaining gradients
what are catabolic reactions
energy from the brake down of large macromolecules releasing energy
what makes ATP
ADP+Pi+energy
what to catabolic reactions create
- ATP
- NADH
what is involved in oxidative phophorylation
- electron transfer from NADH along a chain of molecules
- O2 is final electron acceptor
how are H+ ions moved
- redox reaction generate energy, H+ pumped from mitochondrial matric through ATPase
- accumulation of H+ in inter membrane space
- generates H+ gradient
how is energy stored in the body
- stored as macromolecules
- ATP can’t be stored so neither can O2
how does partial pressure change affinity for oxygen
increase in PP decreases affinity of oxygen to haemoglobin
what is tissue hypoxia
when the tissue O2 demand is greater the supply
what are the 4 main mechanisms of tissue hypoxia
- lack of blood flow
- reduced number of Hb
- reduced unloading of O2 from Hb
- low Hb saturation due to low PaO2
oxygen unloading affinity
higher tissue pO2, reduces unloading and lower pO2 enhances unloading
how does oxygen unloading link to CO2
- CO2 has a high affinity for Hb with slow binding
- CO2 binding to Hb at same site causing O2 displacement
what is henry’s law
the amount of gas dissolved in a liquid depends on solubility of that gas in the liquid and pressure of the gas
how does oxygen treatment treat carbon monoxide poisoning
100% O2 makes half life of carbon monoxide decrease from 4 hours to 40 minutes
what are the limitations of pulse ox in carbon monoxide poisoning
- HB-O2 and HbCO absorb red light similarly
- pulse ox overestimate spO2 giving false positives
- pt is hypoxaemic
what can cause falsely normal or elevated SpO2
- CO poisoning
- sickle cell anaemia vaso-occlusive crisis
what can cause falsely low SpO2
- venous pulsations
- excessive movement
- IV pigmented dyes
- finger nail polish
- rare inherited Hb variants
what can cause falsely low or high SpO2
- methemoglobinemia
- sulfhemoglobinemia
- poor probe positioning
- sepsis and septic shock
what are the observations of cynosis
bluish colour of lips, tongue, gum, ears, nose, nails, fingers/ feet
what does a low arterial PaO2 show
- low amount of dissolved O2
- lower Hb-O2 saturation
what are the main mechanisms of low arterial PaO2
- reduced alveolar PaO2
- diffusion limitation
- VQ scatter
- Shunts
how does hypoventilation reduce PaO2
- reduced respiratory rate
- reduced tidal volume
- increased dead space
- asphyxiation
what is the diffusion limitation
rate of O2 diffusion at respiratory membrane is reduced when partial pressure gradient is reduced
what factors affect the diffusion rate of O2
- decreased surface area of diffusion
- increased thickness
what happens to diffusion during exersice
- transit time in pulmonary capillaries is decreased
- increased cardiac output
- muscle need more O2
what happens to diffusion when diffusion rate is reduced
longer duration will be required for equilibrium to be reached at rest
what is deadspace in relation to VQ scatter
areas are better ventilated than perfusied
what is shunt in relation to VQ mismatch
area are better perfused than they are ventilated
how does increased VQ scatter reduce PaO2
increase in areas with low VQ decreases O2 content of blood from disassociation curve
what is a shunt in gas exchange
- blood not moving to where it is needed to be oxygenated
what is the bodies response to supplemental O2 in hypoxemia
- PaO2 needs to be managed and then underlying cause altered
- high FiO2 needed to raise PaO2 in shunt
where is CO2 produced in the cell cycles
- TCA cycle in mitochondria
- diffuses from cell to blood
- CO2 binds to Hb releases H+ proton
what is the Haldane effect
loss of affinity of Hb for CO2 and H+ when PaO2 increases
how id CO2 transported from respiring tissue to the lungs
- gas dissolved in plasma
- bound to proteins
- as bicarbonate after H2O reaction
why are CO2 variations seen slowly
- buffering systems slow it down
- O2 has a rapid changed in arterial partial pressure
what factors affect alveolar CO2
- CO2 output
- ventilation rate
- inspired CO2 concentration
- decreased diffusion capacity
what is capnography used for
- alveolar and arterial PCO2
- look at expired CO2 changes according to phase of respiratory cycle
what are the difference capnography phases
- inspiration and early exhalation
- transitional phase
- alveolar plateau
- inspiratory downslope
what regulates ventialtion
medullar: dorsal respiratory group and ventral respiratory group
what inputs modify ventilation
- voluntary actions
- involuntary actions
- chemoreceptor activity
- muscle and joint receptors
- lung stretch receptors and lung irritant receptors
- emotion
where is the medullary dorsal respiratory group location
bilaterally in and around the nucleus tractus solitarius
what activates the medullary dorsal respiratory group
neurones activated during inspiration
how does the medullary dorsal group work
- projecting to motor neurons in the spinal cord
- projects to medullary ventral group
- carry sensory efferent information from peripheral chemoreceptors
what is the function of the medullary dorsal respiratory group
integration of sensory input to reflex alter the breathing pattern
where is the medullary ventral respiratory group located
- bilaterally in discreet regions
what is the overall mechanism of the medullary ventral respiratory group
- receives sensory info from DRG
- has inspiratory and expiratory neurones
- has interneurons, premotor neurons and motor neurons
what is the caudal VRG
- retro-ambigualis - expiratory upper motor neurone decussation
- para-ambigualis - inspiratory neurones
what is the rostral VRG
- airway dilator
- location of central pattern generator
- expiratory neurones
what is the chemical feedback regulation of ventilaton
- tigger, decrease O2 increase CO2
- sensor activation of peripheral chemoreceptors
- chemo sensitive neurones in medulla
- medullary respiratory group activated
- increased firing on somatic nerves
- contraction of primary and secondary respiratory muscle
what do carotid chemoreceptors detect
- arterial hypoxaemia
- low ph
- increased pCO2
what do medullary central chemoreceptors detect
drop in ph in cerebrospinal fluid
how to palpate accessory skeletal muscle use in respiration
- posterior triangle of neck feel the contraction
- sternomastoid, thumb and first finger draw back to feel contraction
