Arterial Blood Gases, Control of Respiration and Respiratory Adaptation at Altitude Flashcards
what conducts involuntary breathing
inspiratory and expiratory neurones
where are inspiratory and expiratory neurones found
PONS
Medulla oblongata
What nerves innervate the cerebral cortex and the hypothalamus
CN IX and X
What inputs from the cerebral cortex and hypothalamus can change the respiratory rate
Poutine respiratory centre -> medulla
What does the medulla stimulate or suppress
Voluntary control
Pain
Emotion
Temperature
What do dorsal respiratory group control
Inspiration
What do ventral respiratory group neurones control
Inspiration and expiration in active breathing
What is the pacemaker in the medulla
Central pattern generator which is in the ventral respiratory group
What does the central pattern generator do
Initiates breathing
What are the 2 respiratory control Centres in the brain stem
PON respiratory centres and medullary respiratory centres
What is the pons respiratory centres divided into
Pneomotaxic center
Apneustic center
What is the medullary respiratory center divided into
Dorsal and ventral respiratory group
What does the pontine respiratory center do
Inhibits and excited inspiration
What does the pneumotaxic centre do
Inhibits inspiration to allow expiration
What does the apneustic centre do
Excites inspiration to enhance breathing (gasps)
What do central chemoreceptors detect
PCO2 and pH
What does peripheral chemoreceptors detect
PCO2 pH and PO2
Where are central chemoreceptors found
Lie near the venterolateral surface of the medulla near the exit of CN IX and X
What is the blood brain barrier
Tight endothelial layer which separates the cerebrospinal fluid from blood
What is the blood brain barrier impermeable to
Charged molecules (H+ and HCO3-)
What is the blood brain barrier permeable to
CO2 so it can easily cross from blood to cerebral spinal fluid
What is the pH of the cerebral spinal fluid determined by
Arterial PCO2
is the pH of the cerebral spinal fluid affected by changes in blood pH
no
why does the cerebral spinal fluid have low buffering capacity
little protein
what are neurones in the central chemoreceptors sensitive to
CO2
what are the neurones in the central chemoreceptors less sensitive to
H+
what does an increase in CO2 in the cerebral spinal fluid cause
an increase in minute ventilation (VE)
how does metabolic acidosis shift the CO2-ventilation curve
to the left
how does metabolic alkilosis shift the CO2-ventilation curve
to the right
where is the carotid body found
bifurcation of the common carotid artery just above the carotid sinus
what is the carotid body innervated by
Carotid Sinus Nerve → Glossopharyngeal Nerve (CN IX)
where is the aortic bodies found
around the aoritc arch
what are the aoritc bodies innervated by
Vagus nerve (CNX)
what do all the peripheral chemoreceptors respond to when there is a small change
PCO2, pH, pO2
what happens to minute ventilation when there’s an increase in PCO2
increase
what happens to minute ventilation when there is an increase in pH
decrease
what happens to minute ventilation when there is an increase in PO2
decrease
what happens to the respiratory centre when there hyercapnoea
less sensitive to chronic PaCO2 elevations, and respiratory response becomes blunted
what is the respiratory response to hypocapnoea
- Chronic respiratory acidosis with metabolic compensation
- Hypoxaemia due to hypoventilation
what happens to chemoreceptors in response to chronic lung disease
hypoventilation → prolonged hypercapnoea (high CO2)
what happens to the cerebral spinal fluid pH in response to prolonged hypercapnoea
returns to normal due to adaptive and compensatory processes
what do stretch receptors in smooth muscle of the bronchial walls do
Receive and send signals through Vagi → shallower inspiration, delaying next cycle of inspiration
what do irritant receptors in smooth muscle do
Receive parasympathetic bronchoconstrictor nerve supply via Vagi which act via Acetylcholine and Muscarinic Type 3 receptors → deep sighs, prevent lungs from collapsing
what do juxtapulmonary receptors do
Afferents are small, unmylelinated C-fibres or Vagi. Stimulation → apnoea, rapid shallow breathing, ↓ HR and BP
where are juxtapulmonary receptors found
on alveolar and bronchial walls close to capillaries.
what are juxtapulmonary receptors stimulated by
Stimulated by pulmonary congestion, pulmonary oedema, microemboli and inflammatory mediator.
where are irritant receptors found
smooth muscle and trachea
where are proprioceptors found
Golgi tendon organs, muscle spindles and joints of respiratory muscles (not diaphragm) → Spinal Cord
what are proprioceptors stimulated by
Stimulated by shortening of the respiratory muscles → Respiratory Centre →↓ RR
what are opioids
naturally occurring peptides used as analgesics (pain control)
what do opioids do
Opioids → decrease in sensitivity of peripheral and central chemoreceptors → Respiratory Depression
what is the treatment for opioid overdose
naloxone
where are ABG’s taken from
peripheral artery: Radial, Brachial, Femoral
what does low PaO2 show
respiratory faliure
what does low pH show
acidosis
what does high pH show
alkilosis
what does abnormal PaCO2 show
type 2 respiratory faliure
what does a normal PaCO2 show
type 1 respiratory faliure
what does this ABG show
PaO2: 12.7 kPa (11 – 13 kPa)
pH: 7.50 (7.35 – 7.45)
PaCO2: 5.5 kPa (4.7 – 6.0 kPa)
HCO3-: 29 (22 – 26 mEq/L)
BE: +3 (-2 to +2)
metabolic alkalosis
what does this ABG show
PaO2: 9.1 kPa (11 – 13 kPa)
pH: 7.30 (7.35 – 7.45)
PaCO2: 8.4 kPa (4.7 – 6.0 kPa)
HCO3-: 29 (22 – 26 mEq/L)
BE: +4 (-2 to +2)
respiratory acidosis with metabolic compensation
what does this ABG show
PaO2: 7.9 kPa (11 – 13 kPa)
pH: 7.31 (7.35 – 7.45)
PaCO2: 7.1 (4.7 – 6.0 kPa)
HCO3-: 22 (22 – 26 mEq/L)
BE: +1 (-2 to +2)
type 2 respiratory falire
respiratory acidosis
what does this ABG show
PaO2: 6 kPa (11 – 13 kPa)
pH: 7.51 (7.35 – 7.45)
PaCO2: 3.1 kPa (4.7 – 6.0 kPa)
HCO3-: 21 (22 – 26 mEq/L)
BE: 0 (-2 to +2)
Respiratory alkalosis and type 1 respiratory failure.
what are causes of Type 1 RF
- Low inspired O2 (FIO2): high altitude, asphyxia
- Hypoventilation: COPD
- Diffusion impairment: pulmonary fibrosis
- VQ mismatch: pulmonary emboli, pneumonia
- R-L Shunt: includes congenital causes
what are the causes of type 2 RF
- Failure of ventilation → alveolar hypoventilation
- Chronic Lung Disease:
- Musculoskeletal abnormalities:
- Neuromuscular disease:
- Central Nervous System:
what is the anion gap
difference between primary measured Cations and Anions
what are symotoms of acute mountain sickness
headache and disturbed sleep
malaise, drowsiness
loss of appetite and nausea
what can acute ountain sickness cause
peripheral oadema
what happens during high altitude pulmonary oedema
increase of capillary hydrostatic pressure
what are symptoms of high altitute cerebral oedema
change in level of consciousness
nausea
vomiting
hallucinations, seizures and paralysis