L6 - Pulmonary function testing Flashcards
FEV1
Forced expiratory volume in 1 second
FVC
Forced vital capacity.
Total vol forcefully expired from max inspiration efforts
What might a low FEV1/FVC ratio indicate?
Obstructive pattern: Asthma, emphysema
What might a normal value of FEV1/FVC indicate?
Restrictive or a normal pattern
If the FEV1/FVC is normal but the FVC is low what might this show?
Restrictive pattern
Signs of lung disease
Cough Dyspnea Cyanosis Wheezing Hyperinflation of lungs Hypoxemia Hyperapnia
Dyspnea
Shortness of breath
Hypoxemia
Abnormally low level of oxygen in blood
Hypercapnia
Abnormally elevated level of carbon dioxide.
Spirometry
Measurement of air movement in and out of lungs during various respiratory maneuver’s
How might anaemia affect the lungs?
- Number of haemoglobin molecules reduced.
- Decreased ability of lung to transfer carbon monoxide to blood (experiment)
- Lower diffusion capacity
Examples of conditions which decrease the surface area of the alveolar capillary membrane
Emphysema - breathing tubes narrowed and air sacs damaged.
Pulmonary embolism.
Conditions altering membrane permeability / thickness?
Pulmonary fibrosis
Why is carbon monoxide used to test diffusion capacity?
More soluble in blood than in lung tissue.
What are extraparenchymal causes of restriction? (4)
Impairs patients ability to fully inflate lungs:
- Obesity
- Neuromuscular disease
- Chest wall deformities
- Large pleural effusion
Describe quiet respiration pathophys
- Diaphragm contracts.
- Moves downwards.
- Parietal pleura attached to diaphragm descends.
- Movement pulls down visceral pleura.
- Airway and alveoli expand.
- Air sucked into lungs.
What occurs during expiration?
- Diaphragm relaxes
- Recoil of elastic tissue in lungs expels air from alveoli and airways.
Describe the use of accessory muscles during forced respiration?
- Neck muscles pull ribcage upwards.
- Sternocleidomastoid elevates sternum.
- Scalenus major and minor elevate first two ribs and sternum.
Which muscles pull the ribcage downwards?
- Oblique.
- Transverse.
- Rectus abdominus.
Which muscles fix shoulder girdle in place and pull ribcage outwards?
Pectoralis major.
Latissimus Dorsi.
Describe innervation of diaphragm?
motor and sensory supply
C3,4,5 keeps diaphragm alive
- Motor supply: via Left and right phrenic nerves.
- Sensory supply:
- Central : Phrenic
- Peripheral: Intercostal
Apnoea
Absence of breathing.
A spinal cord injury where might cause apnoea
Break above C3,C4
Intercostal muscles innervated by which distribution of motor neurones?
T1-T12
Intrapulmonary pressure
Pressure within alveoli.
e.g. Expansion of chest and accompanying inflation of lungs will cause pressure within alveoli to fall.
Intrapleural pressure
Pressure between viscera and parietal pleural layers.
Pressure in pleural space.
How might intrapleural pressure be measured?
By inserting tip of needle connected to a manometer into pleural cavity.
What can maximal respiratory pressure be used to measure?
Strength of inspiratory and expiratory muscles.
Tidal volume
- Amount of air inspired and expired at each breath
- at any level of activity.
Residual volume
Volume of air that remains in the lungs that cannot be completely emptied.
Functional residual capacity
Volume of air left in lungs at the very end of normal expiration
What may increase airway resistance?
- Structures outside conducting airways (tumours) or mediastinal masses
- Laryngeal spasm
- Gastric content / blood blocking airway
- Relaxation of genioglossus muscle during anaesthesia causing tongue to fall backward
- Aspirated object
Describe genioglossus muscle?
- Fan shaped muscle.
- Forms most of tongue mass.
- Inserts on hyoid bone as well as inferior portion of tongue.
Bronchomotor tone is under what type of nervous innervation
Parasympathetic
Describe mediation of bronchoconstriction
- Mediated by efferents from vagus to ganglia in the wall of small bronchi.
- From which short post ganglionic fibres lead to nerve endings that release ACH to act at muscarinic receptors in bronchi smooth muscle.
Describe stimulants of bronchoconstriction? (4)
- Cigarette smoke
- Histamine release from mast cells (affects parasymp), direct action on airway smooth muscle.
- Non-adrenergic noncholinergic fibres releasing Vasoactive intestinal polypetide.
- nSAIDS: notabily aspirin, and B-adrenoreceptor blocking drugs
nSAIDS causing bronchconstriction
- Aspirin
- Beta-adrenoreceptor blocking drugs
Compliance
How easily lungs can be distended.
Types of lung disease causing decreased DLCO
- Emphysema , CF
- Fibrosing alveoli, asbestosis
- Pulmonary embolism
- pulmonary vascular disease with occlusion.
How might we measure total lung capacity?
Dilution of an inert gas such as helium in an enclosed box.
Total body: plethysmograph
Tests for gas exchange
- Pulse oximetry
- measured by the absorbance of light by haemoglobin, used to assess hypoxaemia - Blood gas analysis
What occurs in respiratory acidosis
PaCO2 RISES.
pH FALLS.
Compensation: kidneys retain bicarb
In what situations may respiratory acidosis occur?
- Lung disease
- COPD, pneumonia, asthma, pulmonary odema - MSK disorders
- Kyphoscoliosis, chest trauma, Guillain Barre, Myasthenia Gravis
Kyphoscoliosis
Abnormal curvature of the vertebral column.
Arterial blood gas measures… (4)
Measures:
- acidity
- pH
- levels of oxygen
- levels carbon dioxide.
Sign of bronchiectasis
Bronchiectasis - airway of lungs become abnormally widened.
Leeds to build up of excess mucus that can make the lungs more vulnerable to infection.
A patient with chronic heart failure may have?
- Positional and exertional breathlessness.
- Elevated JVP
- peripheral oedema.
- Tachycardia
- crackles.
A reduced lung volume may indicate
Restrictive problems.
- Interstitial lung disease, thoracic cage abnormalities, neuromuscular problems.
An increase lung volume may indicate
Air trapping and lung overinflation, typical of COPD.
Pattern of raised RV (residual volume) and raised FRC (Functional residual capacity) with other volumes normal.
Lung diffusion measurement
Measures ability of lungs to transfer gases across the alveolar capillary membrane - from lung to blood stream.
DLCO - measures what heart has to deal with, composite measure of lung vol and basement membrane abnormality
KCO - measured value. adjusted for lung volume hence demonstrates alveolar membrane pathology.
Examples of interstitial parenchymal lung disases?
- Fibrosis
- Granulomastosis TB
- inflammation of tissues including BV, primarily in resp tract - Pneumoconiosis
- Pneumonitis (Lupus)
Pneumoconiosus
Disease of lungs due to inhalation of dust.
Pneumonitis
Autoimmune.
Inflammation
Sniff test
aka Diaphragm Fluoroscopy
Done to evaluate function of diaphragm.
Continuous beam of X-rays to see the diaphragm move up and down on insp and exp.
Patient asked to sniff forcefully while images are acquired.
