Resp: FEV, Respiratory failure, Asthma Flashcards
What is FEV 1
Forced expiratory volume in 1 second
Where a person takes maximal inspiration and then exhales maximally as fast as possible
Procedure to measure FEV 1
Breathe in to total lung capacity
Exhale as fast as possible in one second
Volume produced is FVC for one second
What is FEV 6
Forced expiratory volume 6 seconds
When is flow of air in res cycle greatest
Expiration, and declines in rate as volume decreases
What does FEF25 mean
Flow at point when 25% of total volume is exhaled has been exhaled
Define FVC
Forced Vital capacity
Name 4 obstructive lung diseases
- COPD
- Asthma
- Bronchiectasis
- Bronchitis
When is the value of FEV1 normal
When it is 80% of the normal predicted value for that patient
What indicates airways restriction
- Ratio of FEV1/FVC greater than 0.7 AND FVC is lower than 80% of predicted value
- Just a low FVC (less than 80% of predicted value
What indicates airways obstruction
- FEV1/FVC less than 0.7 (in other words they can breathe fast in the first second but obstruction stops them from fully expelling their total capacity volume)
Define type I respiratory failure
- Hypoxia but not hypercapnia
What causes type I respiratory failure
- High altitude
- VQ mismatch
- Shunting
- Diffusion problem (oxygen can’t enter capillaries due to parenchymal disease)
What defines type II respiratory failure
- Hypoxia
- Hypercapnia
- pH DECREASED
What causes type II respiratory failure
- Increased respiratory resistance (COPD, asthma)
- Reduced breathing effort (brain stem lesions! Obeisty)
- Guillain-Barré Syndrome
- MND
- Ankylosing Spondylitis
- Decrease in area of the lung available for gas exchange
ANYTHINg that causes inadequate alveolar ventilation
CO2 CAN’T BE ELIMINATED
Where in the lungs is V/Q ration higher
Apex
Lower in base of lungs
Why iS V/Q lower at the base of the lung
Because Perfusion increases as we go down the lungs faster than ventilation due to gravity
What is a V/Q of 0
Area with perfusion and no ventilation = shunt
What is dead space
Area with ventilation and no perfusion (V/Q of infinity)
Effect of pulmonary embolism on V/Q
High V/Q
Because there is a decrease in Q, making value bigger
What most commonly causes type I res failure
Pulmonary embolism
What most commonly causes type II resp failure
Hypoventilation
What neurological conditions can result in reduced ventilation
- MG
- Guillain-Barre syndrome
- Encephalitis
- MND
- Space-occupying lesions (increased ICP which can compress brainstem)
What conditions can decrease Q in V/Q
- Pulmonary embolism
- Cardiac failure
- Shunt (VSD)
- Pulmonary hypertension
What conditions can decrease V in V/Q
- COPD
- Neurological weakness
- Obesity
- Reduced drive from narcotics
Signs of hypercapnia
- tachycardia
- Flapping tremour
- Confusion
- Drowsiness
- Reduced consciousness
Difference between ASTHMA and COPD
Asthma : airflow varies in obstruction
COPD: Fixed airflow obstruction
What is the transfer co-efficient
Measure of ability of oxygen to diffuse across alveolar membrane
How do you calculate transfer co-efficient
Inspiring a small amount of CO and hold breath for 10 seconds at total lung capacity, fast transferred measured
In what conditions is transfer co-efficient low in
- Severe emphysema
- Fibrosing alveolitis
- Anaemia
- Pulmonary hypertension
- COPD
When is transfer co-efficient high
Pulmonary haemorrhage (can absorb O2 efficiently as bleeding means more blood cells available)
Risk factors for COPD
- Tobacco smoking
- Female
- Secondhand smoke
- Air pollution
- Cold mining, silica dust
- Alpha 1-antitrypsin deficiency
- Poverty
What can exacerbate COPD
- Cold temperature
2. Pulmonary embolus
Signs of pulmonary emboli in COPD
- Heart failure
- Pleuritic chest pains
NO SIGN OF INFECTION
Pathophysiology of COPD
- Increased numbers of mucus-secreting goblet cells within bronchial mucosa
- CHRONIC BRONCHITIS occur
- Airway narrowing and airflow limitation due to HYPERTROPHY AND HYPERPLASIA of mucus secreting glands of the bronchial tress, bronchial wall inflammation and mucosal oedema
- Infiltration of walls of bronchi and bronchioles with acute and chronic inflammatory cells
- Epithelial cells ulcerate and squamous epithelium replaces columnar cells when ulcer heals
- Causes scarring and thickening of walls which narrows airways
When can chronic bronchitis be reversed
Early in disease when there is no significant change in breathlessness
Continued inflammation even when smoking is stopped
What kind of patients present with COPD
- Alpha-1 antitrypsin gene deficiency
2. Young patients
What dies alpha-1 antitrypsin deficiency do in th body
Causes cirrhosis
When is airflow worst
Breathing out
What is the replacement of columnar epithelial cells with squamous epithelial tissue now called
- Bullae
Large air pockets (Bulllous emphysema)
Why is airflow worst when breathing out
Because the chest is compressing airways at this time
So more air remains in the lungs than should be there = hyperinflation
Define emphysema
- Dilatation and destruction of lung tissue distal to terminal bronchioles
Results in loss of elastic recoil which normally keep airways open during expiration
This makes it harder to breathe out in COPD
What emphysema is found in smokers
Centriacinar emphysema
What emphysema is seen in alpha 1 - antitrypsin deficiency
Panacinar emphysema
What is panacinar emphysema
- INVOLVES destruction of ENTIRE respiratory acinus from respiratory bronchiole to alveoli is expanded
What is centriacinar emphysema
- Only effects respiratory bronchiole (alveoli are unchanged)
What causes V/Q mismatch in COPD
- Damage and mucus plugging of small airways during expiration and rapid closure in smaller airways lead stop fall in PaO1 and increased work of inspiration
Why is CO2 level unaffected in COPD
- Increase in CO2 increases rate of preparation but patients become insensitive to CO@ and depend on hyperaemia to drive ventilation = eventual increase in CO2