CP

- to understand what is happening int he lungs

- spirometry

- total amount of gas contained in the lung at full inspiration

• - volume of gas ramining in the lung at the end of a normal expiration
• - the frc is the point (lung volume) at which all these forces are in equilibrium

- volume of gas ramining in the lung at the end of a maximal expiration

- voume of gas inspired or expired during a normal breath

- maximal amount that can be expired aftera  full inspiration

• - height
• - lung, chest wall and abdominal pathology (basically elasticity)
• - gravity
• - position

• - prevents closure of the small airways and alveoli during expiration
• - reduces WOB- efficient
• - allows for continuous gas exchange during inspiration and expiration

- is volume at which small airways start to close

then the small airway collapse is likely to occur during breathing - alveolar collapse- blood directed to non ventilated alvolie (V/Q mismatch) - hypoxaemia

• - age
• - obestity
• - post surgery
• - anaesthesia
• - restricitve lung disease
• - increased abdominal pressure

• -measurement of volume of gas in the lung at fixed points during the breathing cycle
• - lab based
• - most commonly measured
• - TLC
• - RV
• - FRC

• - total body plethysmography- pt inside a closed pressure box and inspired and expires against a closed shutter- thoracic volumes can be worked out by pressure changes
• - helium dilution- a marker gas is used to measure RV or FRC, gas is rebreathed through a closed circuit and the final concentraion is used to calculate the accessible volume of the lung

- hyperinflation

- gas trapping

- restrictive pattern

- max expired air after full inspiration

• - involves the measurement of forced expiration from TLC
• - provides a great deal of infomration
• -pts readings are compared to age and height match to normal values
• - identifying pathology
• - assessing extent of respiratory compromise
• - monitoring lung disease

• - FVC- forced vital capacity
• - VC- slow (unforced) vital capacity
• - FEV1- forced vital capacity in one second
• - MMEFR (FER 25-75%)

• - the volume of gas that can be forcefully expired in the first second
• - FEV1 is a measurement of the flow rate at which air can beblwon out of the lungs

• - narrowing of the airways
• - loss of expiratory power
• - inadequate expiratory effort
• - inadequate inspiratory volume

• - as an actual volume (eg 1.0L)
• - as a % redicted (eg 40% pred)
• - as a % of FVC (ratio)

-FVC- the total colume of gas that be forcefully expired from TLC. Measure of the accessible lung volume (apart from RV)

• - VC (slow vital capacity)
• - used if the pts airways have a tendency to collapse during forceful expiration eg emphysema (COPD)
• - in this situation VC is more acurate than FVC

• - factors that reduce inspiratory volume- ie not enough volume to start
• - factors that limit airflow- airway obstruction, loss of lung elasticity

- an adult with normal respiratory system functioning can blow out at least 75% of FVC in the first second of forced expiration

• -restrictive pattern
• - obstructive patterns

• - low FEV1
• - FVC- normal, increase or decreased
• - FEV1/FVC ration <75%

• - all lung volumes are reduced
• - FEV1 and FVC are down
• - FEV1/FVC may be preserved or sometimes elevated

• - maximum mid expiratory flow rate
• - forced expiratory flow- 25-75%
• - detects obstructive changes in small airways- often the first sign of obstructive lung disease

• - due to being a forced technique- can generate high intrathoracic and abdominal pressure
• - unstable heart- IHD, angina, arythmias
• - AAA
• - hernias
• - paroxysmal coughing
• - very unstable airways

• - dizzy/ faint
• - angina
• - increase SOB
• - coughing
• - pain in thorax

PEFR- effort dependent measurement which gives info about the calibre of airways

• - DLCO
• - the measurement of diffusing capacity for carbon monoxide is made when ever a diffusion problem is suspected
• - a reduced DLCO indicates a limitation to diffuse eg pulmonary interstitial fibrosis