Week 2 Hypoventilation / Shunt / Diffusion limitation Flashcards
Invasive and non invasive ways of measuring arterial oxygenation
Invasive: Sample of arterial blood PaO2 SaO2
Non invasive: Oximetry SpO2
Hypoventilation
Define
Amount of fresh gas going to the alveoli (VA)(alveolar ventilation) per unit of time is reduced.
VA= (VT- VD) x f (tidal volume-deadspace)
(VE)(Expired total ventilation) is inadequate for metabolic demand or
(VT)(Tidal volume) is too shallow to clear anatomical dead spaceeffectively
List 4 Concequences of hypoventilation
Increased PaCo2
Decreased PaO2 (may be increased w o2 therapy)
Increased work of breathing
( to eliminate co2 if normal control of breathing is preserved)
Increased dead space- ( physiological dead space)
List 9 Causes of hypoventilation
related to their location in the body.
- Depression of the respiratory centre
- Trauma haemorrage medulla
- Spinal injury (C 3,4,5 PHRENIC NERVE)
- Disease of anterior horn cells (POLIO)
- Disease of nerves supplying muscles ( eg MS)
- Diseases at myoneural junction (eg myesthenia gravis)
- Muscles themselves (Guillan barre,MD)
- Thoracic cage problems (scoliolis)
- Upper airway problem
Sleep disordered breathing
Describe the 2 kinds
- Central sleep apnoea (in brain stem)
decreased respiratory drive during REM sleep
-Obstructive sleep apnoea(OSA) ( upper airways)
muscle tone around tongue and oropharynx decrease
shape of airway circular to oval
airways close down on expiration
*also close down on inspiration
upper airway-pos pressure
lower airway-neg pressure
Mask ventilation for OSA will blow pos pressure into upper airways to keep them open.
Shunt Definition
Blood enters arterial system WITHOUT going through ventilated areas of the lung.
Deoxygenated blood mixes with oxygenated reducing PaO2.
Shunts
- Normal
- Bronchial circulation
- Coronary circulation
- Pathological shunt
- vascular
- intrapulmonary
Describe the 2 causes for
Pathological shunt
Vascular- kids w congenital heart defects vessels are abnormal.(Atrioseptal defect) Blood exits heart w out coming into contact with lungs.
Intrapulmonary- unventilated alveoli due to atalectasis or sputum clogged alveoli. blood passes through.
Normal shunts
Bronchial circulation-Blood in bronchial arteries perfuses bronchi, some O2 is extracted and blood moves to pulmonary veins.
Coronoary circulation- Thespian veins return deoxygenated coronary artery blood to left side of the heart
Compensatory mechanism for intrapulmonary shunt
such as in chronic hypoxemic lung conditions
eg pneumonia
when does this work?
when doesn’t it?
Hypoxic pulmonary vasoconstriciton
corrects the V/Q missmatch V/Q is now zero in that area.
Perfusion redirected to alveoli that are ventilated. Good if only part of the lungs affected
If condition affects all of the lungs eg COPD, cystic fibrosis (Global disease).
All capillaries in both lungs constrict. Increased vascular resistance in capilllaries in lung.
Increased afterload for right side of lung. R sided hypertrophy. R sided heart failure.
Impairments to diffusion with result in
Decreased Pao2
Normal ish PaCO2
*CO2 diffuses more easily.
Rate of diffusion
* edit this
Proportional to tissue area
Difference in gas partial pressure
Diffusion affected by
1Surface area 2Time 3O2 vs Co2 4Pressure difference 5Thickness of alveolar membrane / interstitial space 6V/Q ratio Nature of gas Contact time b/n blood and gas
A-a difference
What is is
How is is calculated
What is it’s value normally?
Difference in oxygen partial pressure b/n arteries and alveoli. (PAO2-PaO2)
*ratio is calculated by PaO2/PAO2
Normally PAO2-PaO2 = 5-20 mmHg
due to normal anatomical shunt
V/Q miss matchhing
Difference increases with disease
Effect of O2 Therapy
supplemental ventilation
Increased PaO2:
Difussion limitation
hypoventilation
V/Q missmatch
No change in PaO2 in:
shunt
List some lung diseases that may alter diffusion
Abnormal quality/quantity of gas exchange membrane.
- Intersitial lung disease
- rhumatoid lung,scleroderma(connective tissue)
Thickening blood gas barrier
-pulmonary oedema
Cough
Dry-Upper respiratory tract infection
- Early stages acute pneumonia
Moist- chronic bronchitis, bronchiectasis,cystic fibrosis,smokers
Loose or tight-
Weak or strong-
Suppressed short painful cough- pleurisy
Nervous
Define Haemoptysis
List some common causes **
Presence blood in sputum due to breakdown of blood vessels adjacent to airway/lung.
Common causes
Define Epistaxis
Nosebleed
Haematemesis
Vomiting blood
What is the difference between wheeze and stridor?
**
Which common respiratory conditions classically present with a wheeze?
WHEEZE - sound produced when air is forced past a point in which airway walls are almost touching. Resulting in vibration of the airway walls. High pitched continous adventitious lung sound.
Heard on expiration. During inspiration the airways are more open and wheeze tends to be less intense
Caused by asthma or airway obstruction. This obstruction may be caused by smooth muscle spasm airway edema, increased secretions, lesions, scarring, tumor foreign bodies.
STRIDOR
Occurs in extrathoracic airways-best heard @mouth or trachea
Heard on inspiration as extrathoracic airways exposed to opposite pressure gradients so diameter decrease on inspiration and increase on expiration
Tracheal or laryngeal obstruction. Croup, laryngeal oedema and tracheal stenosis
Define
Tachypnoea
Hyperventilation
Hypernoea
Tachypnoea- increased rate of breathing
Hyperventilation-breathing in excess of metabolic needs
Hypernoea-Increased breathing
Define
Dyspneoa
Difficulty breathing, shortness of breath.
Feelings of:chest tightness,feeling puffed,suffocating feeling
Define Orthopnoea
Dyspnoea(SOB) that occurs when lying flat
Paroxysmal Nocturnal Dyspnoea (PND)
Can cause orthopnoea
Occurs in patients with cardiac disease
Hydrostatic shifts in blood volume.Left atrial filling pressure is increased leading to increased pulmonary venous congestion and decreased lung compliance
Gravity causes the spread of basal pulmonary oedema to odema free areas of the lung
Describe features of a barrel shaped chest
Normal chest is symmetrical.
Ribs descend 45 degrees from the spine.
AP diameter is less than the transverse diameter
BARREL SHAPED CHEST
ribs more horizontal
Intercostal muscles decreased mechanical advantage
No bucket handle action
Describe and expain
Pectus excavum
Pectus carinatum
Pectus excavum-funnel chest
Most common
Congenital defect several ribs and the sternum grow abnormally inwards, producing a concave, or caved-in, appearance in the anterior chest wall.
Pectus Carinatum-Pigeon chest
Protrusion of the sternum that occurs as a result of an abnormal and unequal growth of the costal cartilage connecting the ribs to the sternum. costal cartilages grow outward pushing the sternum forward.
Although the shape of the chest wall is distorted, it does not usually affect the internal organs. 4x more likely in males
Upper chest breathing pattern
occurs in COPD
Pursed lip breathing Fixed elevated shoulder girdles Use of accessory muscles Intercostal recession Abdominal paradox
Explain the concept of intercostal recession
Drawing in of inspaces ( intercostal spaces)
Seen first in floating ribs
Sucked inwards on inspiration because acessory muscles working so hard due to resistance to airflow that they generate EXCESSIVE negative.
Occurs in patients with COPD
It’s a form of paradoxical movement
Pursed lip breathing
Raises interbronchial pressure by expiratory apposition thereby increasing resistance to expiration.
Generates intrinsic PEEP(positive end expiratory pressure) to keep airways open during expiration for longer.
Prolongs expiration and alters the I:E ratio (normally 1:2 now it’s 1:3) Trying to eliminate CO2 and reduce hyperinflation. Prevents passive airway collapse
Allows patient to take more air in on next inspiration
*Grunting in infants is similar expiration starts with a closed glottis resulting in explosive release of airway pressure. Prevents airway collapse
Signs of respiratory distress
in neonates with severe respiratory issues
Dilation of nostrils- to decrease airway resistance
Grunting- Similar to pursed lip breathing
Sternal recession- Ribcage is very compliant and is associated with increased negative intraplural pressure during inspiration.
See-saw effect- In severe respiratory distress the ribcage will move inward as the abdoment distends outwards during inspiration
Define paradoxical movements
Intercostal recession
Abdominal paradoxical movements
-Abdomen is sucked in on inspiration as an innefective diaphragm is pulled up by negative pressure generated within the chest.
due to paralysed diaphragm , increased inspiratory load or weak muscles
Relavence of examining hands of patient with respiratory distress
Temp:
cold = poor perfusion
hot& sweaty= high CO2 causes vasodialation
Colour:
Blue=cyanosis due to hypoxemia or inadequate perfusion
Nicotine=smoker
Finger clubbing= chronic hypoxemia(low blood oxygen)
Flapping tremor= (asterixis) due to high CO2
Relavence of examining hands of patient with respiratory distress
** return to cyanosis
Temp:
cold = poor perfusion
hot& sweaty= high CO2 causes vasodialation
Colour:
Blue=cyanosis due to hypoxemia or inadequate perfusion
Nicotine=smoker
Finger clubbing= chronic hypoxemia(low blood oxygen)
Flapping tremor= (asterixis) due to high CO2
Cyanosis
Draw the oxyhaemoglobin dissociation curve and label the axes.
ii) Briefly describe the four factors that shift the curve to the right and left.
Bluish discoloration of skin and mucous membranes
Pathological causes of cyanosis: Low PaO2(hypoxemia) Cardiac disease Abnormal haemaglobin pigments Decreased regional blood flow . low CO
What are the normal adult blood gas values
PaO2= 85-100 mmHg
PaCO2= 35-45 mmHg
SaO2 =96-100%
Central v peripheral cyanosis
CENTRAL
Bluish tinge of areas not usually prone to local circulatory changes such as the tongue.
Due to desaturation of arterial blood.Central cyanosis is caused by diseases of the heart or lungs, or abnormal haemoglobin. Will have peripheral cyanosis as well.
PERIPHERAL
Bluish tinge of
Peripheral cyanosis is caused by decreased local circulation and increased extraction of oxygen in the peripheral tissues
Clubbing
i) Explain, using diagrams, what is meant by clubbing.
ii) List conditions whereby clubbing is a recognised feature.
Swelling of the soft tissue of tip of finger with loss of the normal angle between the nail and the nail bed leading to an abnormal rounded appearance.
Downward curving nail.
Softening nail beds which makes nails seem to float instead of being attached.
Primary digital clubbing
pachydermoperiostosis (young males)
Idiopathic pulmonary fibrosis,
Cystic fibrosis (thick mucus in throat and digestive tract),
Lung cancer
Tuberculosis
COPD,
bronchiectasis (destruction of the large airways)
Crohn disease
ulcerative colitis
Congenital heart diseases
Define hypercapnia
List symptoms
Hypercapnia: a condition of abnormally elevated CO2 levels in the blood
PaCO2 of 45mmHg +
Symptoms Headaches especially on walking Confusion, drowsiness, decreased concentration Warm moist skin Full bounding pulse(very strong) Flapping hand tremor (asterixis)
What is a normal breathing rate?
12-16 breaths per min
Sputum
Normal amount 100ml/24 h
Mucoid- clear or white mucous
Purulent- pus cells infection (yellow, green brown)
Rusty- sign of inflammation old red blood cells
Blood stained- haemoptysis
Plugs or casts- impaced mucous shape of airway
Yellow- asthma due to presence of eosinophils
Green- from bacterial infection
Brown- altered blood eg fungal infection
Frothy pink- severe pulmonary oedema
Brown/ black- carbon particles
foul smelling- presence of anaerobic organisms (lung abcess,bronchiectasis)
Define bronchorrhoea
Production of large volumes of clear watery sputum. Sometimes occurs in patients with alveolar cell carcinoma.
