Respiratory Flashcards
Normal ABG pH
7.35-7.45
Normal ABG PCO2 and PO2
PCO2 4.6-5.6 kPa
PO2 12-14.6 kpa
Normal ABG HCO3 and base excess
HCO3 22-26mmol/L
BE - 0
Causes of hypoxia
Hypoxic environment
Anaemia
Stagnant
Hystotoxins
Decr circ blood volume
Lung pathology
Circ failure
Axis on oxygen dissociation curve
Y o2 sat of Hb %
X o2 partial pressure mmHG
Does increased affinity for o2 cause left or right shift in ox Hb dissociation curve
Left
Causes of left shift in ox Hb dissociation curve
Decr pCO2
Decr H+ (alkali pH)
Decr 2,3 DPG
Decr temp
HbF
Causes of right shift in ox Hb dissociation curve
Incr pCO2
Incr H+ (acidosis)
Incr 2,3 DPG
incr temp
What is vital capacity made up of
Insp reserve vol + tidal vol + exp reserve vol
What is functional residual capacity made of
Exp reserve vol + residual vol
How does ventilation and perfusion vary across west zones
Upper zone - incr vent decr perf
Middle zone - vent = perf
Lower zone - decr vent incr perf
What is a shunt
Capillary that can not take part in gas exchange ( shunts blood past alceoli)
Why does perfusion vary across west zones
Less perfusion at top of lung due to gravity (when pt upright)
West zones
Zone 1, where alveolar pressure is higher than arterial or venous pressure;
Zone 2, where the alveolar pressure is lower than the arterial but higher than the venous pressure
Zone 3, where both arterial and venous pressure is higher than alveolar
Zone 4, where the interstitial pressure is higher than alveolar and pulmonary venous pressure (but not pulmonary arterial pressure)
Which west zone only exists in haemorrhage or positive pressure ventilation
Zone 1
Lung compliance
Change in lung volume per unit pressure
‘Stretchiness’
What happens when PEEP is too low
Alveoli collapse (atelectasis) decreasing o2 diffusion area
More pressure needed to re expand alveoli causing atelectotrauma
Factors affecting lung compliance
Lung volume
Age
Posture
Pulmonary blood volume
Bronchial smooth muscle tone
Disease states
Factors effecting thoracic compliance
Age
Posture
Skin lesions (burns)
Obesity
Abdo distension
Kyphoscoliosis
3 aspects of breathing controls
Central
Chemical receptors
Stretch receptor
Medullary control of breathing
Inspiratory pool - source of rhythm, incr output of muscles of resp, inhibits exp pool
Expiratory pool - gradually starts activity during inspiration, inhibits insp pool
Pontine control of resp
Pneumotactic centre - fine tunes vent rate and vol, inhibits insp pool during inspiration
Apneustic centre - prolonged inspiration, acts on insp pool
Where are peripheral and central chemoreceptors found
Peripheral carotid bodies
Central medulla
What are peripheral and central chemoreceptors sensitive to
Peripheral - o2 conc
Central - H+ ion conc
Do peripheral or central chemoreceptors have a greater response to CO2
Central
Where are irritant receptors found and what effects do they cause
Upper airway and trachea mucosa
Cause Bronchoconstriction and apnoea
Pressure receptors involved in breathing regulation and their locations
Pulmonary stretch receptors - airway smooth muscle
J receptors - alveolar walls
Golgi tendon organs - intercostal muscles
Muscle spindles - insp muscles and diapragm
Pressure receptor effects to regulate breathing
Pulmonary stretch receptors - inhibit inspiration on distension
J receptors - vause rapid shallow breathing
Golgi tendon organs - inhibit inspiration when chest wall distended
Muscle spindles - activate when intense resp effort required
