Flashcards in Mechanics Of Breathing-2 Deck (23)
What technique is used for testing lung volume ?
- measures tidal volume, inspiratory reserve volume, excitatory reserve volume
What parameters are used to calculate vital capacity ?
Inspiratory reserve volume
Expiratory reserve volume
For a 70kg man what are the values of the different lung volumes and capacities ?
Tidal volume= 500 ml
Inspiratory reserve volume= 3000ml
Exploratory reserve volume= 1000ml
Residual volume = 1200ml
Inspirit pry capacity = Tv + irv = 3500ml
Vital capacity= tv+irv+ erv= 4500ml
What is functional residual capacity ?
Volume of air in the lungs at the end of tidal expiration
Erv + residual volume= 2200ml
How do you calculate total lung capacity ?
Tidal volume + expiratory reserve volume + inspiratory reserve volume + residual volume= 5700ml
Define tidal volume
Volume of air that moves into and out of the lungs during a single unforced breath
What is inspiratory reserve volume ?
Max volume of air that can be inspired at the end of a normal inspiration
What is expiratory reserve volume ?
Max volume of air that can be expired at the end of a normal expiration
What is residual volume. ?
Volume of air remaining in the lungs at the end of max expiration
What is the helium dilution test ?
Helium is almost insoluble in blood
Used to measure residual volume
Subject breathes in a gas mixture containing known conc of helium
In inspiration this mixes with air in the lungs and dilutes the helium
Subject exhales and the concentration of helium is compared to original
What is minute ventilation ?
Total amount of air flowing into or out of respiratory system per minute
Tidal volume * respiration rate
What is the typical amount of air which reaches alveoli ?
350ml - 70%
What is alveolar ventilation ?
It is a measure of the volume of fresh air reaching the alveoli each minute - includes the correction for the dead space volume
What is FVC ?
Forced vital capacity - volume of air expired after a max inspiration
What is FEV1 ?
Forced expiratory volume in 1 second- volume of air expired in 1 second after max inspiration
What is the normal FEV1:FVC ratio ?
Lower than this indicates airway resistance
What is another method for assessing airway resistance ?
Peak expiratory flow
What is restrictive pulmonary disease ?
Causes decrease lung volume, increased work of breathing and inadequate ventilation
Common cause is decreased compliance - others include weak muscles of damaged nerves
Causes shortness of breath and often a cough
What are examples of restrictive pulmonary disease ?
What is asbestosis ?
Inhalation of microscopic fibres of asbestosis
Reach bronchioles and alveoli they trigger lung immune response and cause inflammatory response
Macrophages phagocytise fibres and stimulate fibroblasts to deposit connective tissues
Macrophages die off relaxing cytokines which attracts more macrophages
Fibrosis occurs causing thickening of alveolar Wales and reduced lung elasticity and reduces gas diffusion
What is obstructive pulmonary disease ?
Obstruction of airways often caused by inflamed and/or easily collapsible airways
Symptoms : cough, shortness of breath, wheezing, fatigue
What is asthma, ?
Common inflammatory disease of airways
Genetic and environental factors
Triggered by allergens, irritants, drugs, infections and exercise