Respiratory Flashcards
Distinguish between an anatomical and physiological shunt and dead space
Anatomical shunt - when blood moves from the right side of the heart without passing through the lungs - eg: congenital heart defect
Physiological shunt - when perfusion exceeds ventilation - eg: asthma/pnemonia
Anatomical dead space - the air in the conducting airspace that does not participate with gas exchange (usually about 150ml)
Physiological dead space - anatomical dead space plus alviolar dead space in which ventilation exceeds perfusion (usually equivilent to anatomical dead space, however in diseases taht cause poor perfusion, physiological dead space is larger )
Discuss the role of ventilation and perfusion (V/Q) matching and shunting in oxygen delivery and consumption
Effective gas exchange needs an even distribution of gas (ventilation) and blood (perfusion).
V/Q ratio’s reflect the relationship between the pulmonary circulation and the ventilation of the alvioli.
Anything that alters ventilation or perfusion will impair gas exchange.
A pulmonary shunt occurs when deoxygenated blood passes from the right to the left side of the heart without participating in gas exchange at the pulmonary capilaries.
Discuss the transport of oxygen in the blood under the following headlines:
- Dissolved oxygen
- Haemoglobin bound oxygen
Heamoglobin bound oxygen (oxyhaemoglobin) is transported from the pulmonary circulation to cells by the red blood cell.
Dissolved oxygen (about 2%) is carried in plasma and intracellular fluid.
Explain the oxygen-haemoglobin-dissociation curve
It describes the relationship between affinity of haemoglobin for oxygen with an increasing PaO2 (partial pressure of oxygen).
Haemoglobin has 4 different subunits each with an O2 binding spot. When one O2 binds, it causes an increased affinity for the next subunit.
It is affected by:
- PCO2
- Hydrogen ion concentration (pH)
- Temperature
- 2,3-DPG (a phosphate in RBC that plays a role in liberating O2 from Hb)
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Discuss the factors that result in a Right shift to the OHDC
- depicts a decrease in Hb affinity for O2*
- Promotes dissociation at the cellular level
Caused by:
- Increased PCO2
- Increased H+/decreased pH
- Increased temperature
- Increased DPG
Clinical applications:
- Ventilatory failure
- Metabolic acidosis
- Fever
- Septic shock
Discuss the factors that result in a Left shift to the OHDC
- Depicts the Hb’s increased affinity for O2*
- Promotes association in the lungs
- Improves SpO2 at lower PO2 levels
Caused by:
- Decreased pCO2
- Decreased H+ ions/increased pH
- Dereased temperature
- Decreaed 2,3 DPG
Clinical applications:
- Metabolic alkalosis
- Hypothermia
- Respiratory alkalosis
Discuss the relationship between oxygen content, oxygen delivery, oxygen consumption and oxyen extraction ratio in the assessment of hypoxaemia and shunting
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Describe how carbon dioxide is transported in the blood
CO2 diffuses into the blood, small amount of CO2 is carried in the blood plasma, or carried by haemoglobin forming carbaminohaemoglobin.
Most CO2 is carried in the bicarbonate ion of carbonic acid (made up of H+ and HCO3-).
- Increased CO2 = increased pH as carbonic acid splits to bicarb and H+ ions. Therefore respiratory acidosis.
- Decreased CO2 = less H+ ion release from carbonic acid.
Effects of hypoxia on the lungs and consequences of hypoxia
Hypoxia causes blood vessels in the pulmonary circulation to vasoconstrict.
Consequences:
- Altered cell function and structure
- Aerobic metabolism
- Biochemical disruption
- Intracellular dysfunction
- Cell death
Define hypercapnia and describe clinical manifestations
An accumulation of CO2 in the blood (PaCO2 > 45mmHg).
Clinical Manifestations:
- Depression of CNS
- Headache
- Papilloedema
- Flapping tremmor of hands
- Narcosis
- Coma
Define:
Type 1 respiratory failure
Type 2 respiratory failure
Type 1:
Lung damage preventing adequate oxygenation of the blood. CO2 remains unchanged as it requires less functioning lung tissue to excrete.
Type 2:
‘Ventilatory failure’. Alviolar ventilation is insufficent to oxygenate AND excrete CO2. Therefore hypoxia and hypercapnia.
How to interpret a CXR using DRSABCD
DETAILS
- pt information, type of film (PA/AP, L and R marker)
RIPE (image quality)
- rotation (clavicles even)
- inspiration (5-6 anterior/8-10posterior ribs above diaphragm)
- picture (straight, entire lung fields)
- exposure (IV disk spaces, L hemidiaphragm visible through cardiac)
SOFT TISSUE AND BONES
- #, soft tissue swelling, subcut emphysema
AIRWAY AND MEDIASTINUM
- trachea, carina, aortic knob,
BREATHING
- lung fields (lesions, pneumothorax)
- pleura (reflections, thickening)
CIRCULATION
- heart position (2/3 L, 1/3 R)
- heart size
DIAPHRAGM
- shape/contour
- costrphrenic angles
- gastric bubble
EXTRA’S
- ETT, CVP, pacemaker etc
