11: Respiratory instramentation Flashcards
1
Q
Lung volumes
A
- Inspiratory reserve- how much extra you can consume
- Tidal volume- intake with normal breath
- Expiratory reserve- how much extra you can expel
- Residual volume- amount that can’t leave lungs following maximal expiration
- Vital capacity = IRV + TV + ERV
- Total lung volume = IRV + TV + ERV + RV
2
Q
Respiratory instrumentation measurement aims
A
- Presence of respiration
- Pressure measurement
- Flow rates- flow meter or pneumotachometer
- Lung volumes- spirometry or body plethysmograph
3
Q
Presence of respiration
A
- Transthoracic impedance (pneumograph)
- Chest movement
- Nasal thermistor
4
Q
Pneumotachometer
A
- Breathe through a tube containing a resistive element
- Venturi effect- fluid pressure drops as fluid flows across resistive element
- Pressure differential linearly related to air-flow velocity
5
Q
Lung volume measurement
A
- Spirometry- measure gas volume passing through airway opening (measures changes only)
- Gas dilution and body plethysmography- measure absolute volume and changes in volume of gas space within body
6
Q
Spirometry for forced expiration
A
• Obstructive conditions = o Normal forced vital capacity (FVC) o Reduced FEV1 o FEV1/FVC ratio reduced o Flow volume loop concave • Restrictive conditions = o FVC reduced o FEV1 reduced o FEV1/FVC ratio normal or increased o Flow volume loop normal shaped, but steeper
7
Q
Gas dilution technique
A
- Known concentration of gas inhaled (helium or carbon monoxide)
- Change in concentration measured after inhaling for while
- Indicative of functional residual capacity (air in lungs after passive expiration)
- Subsequently measure RV and TLV
8
Q
Total-body plethysmograph
A
- Patient sits inside airtight chamber breathing into tube
- End of normal expiration, shutter closes off breathing tube
- Subsequent volume change in chamber = volume change in chest
- Use Boyle’s law to find final volume in chamber/chest
