control on ventilation

Question 1

what is hyperinflation , what is it associated with and what can it cause

Answer 1

• abnormal increase in the volume of air in the lungs due to air trapping
• commonly associated with COPD and asthma
• air trapping occurs due to the increased resistance in the airways of the lungs which prevents air being fully exhaled
• hyperinflation can also cause respiratory muscle shortening as a inflated lung pushes the diaphragm down and flattens it

Question 2

why does obesity contribute to impaired ventilation

Answer 2

• with obesity you have smaller lung volumes
• increased airway resistance and therefore increased work of breathing
• obesity therefore can be an extrinsic cause of restrictive lung disease and it can also cause type 2 respiratory failure

Question 3

where are central chemoreceptors found and what are their role

Answer 3

• found in the medulla of the brain
• roles is to detect changes in carbon dioxide levels, PH in the CSF
• this can result in signals being sent to the lungs from respiratory centre of the brain to either decrease or increase breathing rate

Question 4

what are the list of sensors which are involved in respiratory control

Answer 4

• peripheral chemoreceptors
• central chemoreceptors
• cerebral cortex
• pontine respiratory centre
• pulmonary inputs (stretch receptors, j receptors, irritant receptors)

Question 5

what is the chemical control of ventilation

Answer 5

• plasma carbon dioxide increase
• carbon dioxide crosses brain blood vessel barrier into CSF
• stimulus is [H+] in css stimulates central chemoreceptors
• increases minute ventilation
• few buffers in CSF so small changes in carbon dioxide concentration results in large changes in [H+] and CSF PH
• response (20second) increase ventilation
• result return to normal CO2

Question 6

what is the relationship between partial pressure of carbon dioxide and ventilation

Answer 6

• increasing partial pressure of carbon dioxide increases ventilation however at very low partial pressures of carbon dioxide increasing the concentration has no effect on ventilation

Question 7

what is the stimuli for peripheral chemoreceptors

Answer 7

• partial pressure of oxygen and to a lesser extent partial pressure of carbon dioxide/[H+]
• response is second- increase in ventilation
• result return to normal PaO2
• peripheral chemoreceptors found in carotid and aortic bodies
• account less to increasing ventilation

Question 8

what is the relationship between partial pressure of oxygen and ventilation

Answer 8

• at very low partial pressures of oxygen decreasing oxygen massively increases ventilation
• however at normal/high oxygen levels changes to the partial pressure of oxygen has no effect on ventilation

Question 9

what shifts the carbon dioxide response curve to the left

Answer 9

• low ph (metabolic acidosis), hypoxia
• shift to the left suggests increase sensitivity

Question 10

what shifts carbon dioxide ventilation curve to the right

Answer 10

• right shift suggests decreased sensitivity so extreme values required for body to respond
• causes COPD (elevated carbon dioxide levels, chemoreceptors resist to tolerate high carbon dioxide levels)

Question 11

what are some mechanical influence of ventilation and the receptors involved

Answer 11

• irritant receptors (sense-dust, chemicals)
• stretch receptors (sense- lung inflation)
• J receptors (sense- pulmonary oedema from heart failure, stretch, chemicals)
• muscle joint receptors (sense-chest wall position, muscle tension)

Question 12

what are some other sensors for ventilation

Answer 12

• temperature- skin heating can cause hyperventilation
• pain- hyperventilation
• diving reflex- decreased hr

Question 13

what is the body response to exercise in terms of ventilation

Answer 13

• ventilation increases immediately and matches the increased oxygen uptake and carbon dioxide output
• venous carbon dioxide goes up during exercise but not arterial
• driven by muscle/temp receptors

Question 14

what is the loop gain

Answer 14

• how well the respiratory system responds to changes in blood gases such as oxygen and carbon dioxide levels
• has a controller gain which measures changes in ventilation with regards to changes in carbon dioxide levels (sensitivity of brain stems respiratory centre to changes in arterial carbon dioxide)
• plan paint- measures how effectively changes in ventilation affect gas exchange in the lungs and blood