Lecture 10 - Spirometry Flashcards
Spirometry
Measures the volume of air breathed in and out and generates a tracing
Tracing
Used to calculate:
- Tidal volume
- Vital capacity
- Flow rate of air movement
Pulmonary function test
Not diagnostic Patient assessment: - changes - response to therapy - compensation - pre-surgical assessment
Research:
- epidemiology
- study of growth and development
- investigation of disease processes
FVC seated
Higher amount of air exhaled when standing but high intrathoracic pressure can reduce CO and cerebral blood flow so may faint
Always do spirometry when sitting down and use nose piece to stop air escaping from nasal cavity
Spirometry results
Volume - time tracing
Volume - time graph
Flow - volume loop
Collins waterseal spirometer
Inhale - Gas decreases and floating jar sinks and pen rises
Exhale- Gas passes into water jar rises and pen sinks
Inspiration and expiration on a tracer
Inhalation - upwards deflection
Expiration - downwards deflection
IRV
Difference between max inhaled air and normal inhaled air
RV
Air that stays in lungs
VC
IRV + TV + ERV
or
IC + ERV
Max inspiration and expiration
FRC
ERV and RV
How much air left in lungs after a normal exhale
Maximum filling factors
Determined by:
- Max inspiratory effort - muscle weakness due to deformity or injury
- Recoil force of lungs - if stiff
= restrictive deficit
FVC
Forced expiratory max volume
- reduced in restrictive disorders
FEV1
Volume of air exhaled in 1 second during forced expiration
- decreases with narrowing of airways and airway closure - obstructive deficits
e. g. asthma and COPD
PEF
Maximal speed of airflow when exhaling
Shown by slope of graph
Or measured by peak flow spirometer
Speed decreases in asthma
Obstructive deficit spirometry
FVC - normal
FEV1 - reduced
FEV1/FVC - below 70%
Restrictive deficit spirometry
FVC - reduced
FEV1 - reduced proportionately
FEV1/ FVC- greater than 70%
E.g Lung fibrosis
Nomograms
FVC compared to value of people with same:
- age
- height
- gender
How to get PEFR from volume time graph
Tangent at 0 with line
How to tell the difference between COPD and asthma
Both show obstructive pattern
Give bronchodilator - asthma spirometry should improve but COPD does not
Obstructive volume time graph
FVC not markedly reduced
FEV1 reduced
Restrictive volume time graph
FVC reduced
FEV1 reduced proportionally
Flow volume loop
peak - PEFR
TLC - flow at 0 L/sec
Obstructive:
- Scalloping
- Asthma - decreases PEFR
Restrictive:
- Narrowed vital capacity therefore tall and narrow
