Week 11 - Physio techniques for gas & secretion impairments Flashcards
Gas movement impairments are commonly due to:
Low lung volumes such as:
- Low Vt
- Low FRC
- Reduced volume in a particular part of the lung
Gas movement physio techniques
(1) Deep breathing exercises (DBE)
(2) Positioning
(3) Mobilisation
DBE affects: (6)
- Increase Vt
- Alveolar stretch
- Stimulates surfactant prod.
- Decreases surface tension
- Increases lung compliance
- Increases VA / VE
Encourage deep inspiration to:
Total lung capacity
+ slow inspiration
What does slow inspiration during DBE do?
- Better distribution of ventilation.
- Slow inspiration gives you the ability to take in airflow to the dependent regions b/c it depends more on lung compliance
- Greater compliance = greater flow
What does fast inspiration do during DBE?
- Airflow depends more on airways resistance
- Less resistance = greater flow
- Resistance is less in the non-dependent regions, so airflow is better distributed here.
How does deep breathing exercises affect the direction of breathing?
- It encourages lateral basal expansion (LBE) which increases distribution of VE to the dependent regions
- Tries to decrease excess AP/upper chest breathing
When would you not want to prescribe DBE?
- Emphysema patients: they are already hyper-inflated
- But post-op you WANT to give DBE
Inspiratory hold:
- Recruits collapsed alveoli + alveolar interdependence
- Appropriate in pts w/ atelectasis/low lung volumes
- NOT hyper-inflated breathless patients
General positioning:
Aims to increase lung volumes
(most imp. increase FRC) [upright pos. are best or side-lying rather than slumped ]
Specific positioning aim:
Aims to re-expand areas of localised atelectasis
Closing capacity (CC)
The lung volume @ which the dependent airways begin to close/cease to ventilate
- Normally FRC>CC so alveoli are open during tidal breathing
- Increases w/ age/smoking
if FRC < CC
Small airway closure during tidal breathing
- Results in reduced gas exchange + decreased PaO2/SaO2
What does an increase in FRC do?
- Increases lung compliance
- Decreases respiratory load
- Increases VQ matching + gas exchange
Specific positioning
- When is it used?
- What position is it aiming to target?
- What does the position do that improves the issue?
- Use w/ a localised gas movement problem; lung/lobar/seg. atelectasis
- Position: Problem area is uppermost/non-dependent
- Gravity will stretch the area open, stimulating surfactant release + increases local compliance
- After - used generalised pos. + DBE to maintain FRC
Modified specific positioning
- What is the aim
- Common positions
Aim is to place the affected lung uppermost (non-dependent) relative to the rest of the lung w/o HDT
- Common positions: L + R sidelying
Benefits of mobilisation: (4)
- Increases FRC + distribution of vent. to dependent regions
- Increases V/Q matching
- Increases CO/lung perfusion
- Increases O2 demand + RR/Vt
Benefits of secretion clearance: (3)
- Reduce infection
- Improve ventilation/gas movement
- Avoid deterioration of breathing mechanics (decrease work of breathing)
Techniques to facilitate the movement + removal of secretions
huff/cough, postural drainage, percussion, vibrations
What does cough do?
- Clears secretions from Upper central airways
What are the components of an effective cough (4)
- Deep inspiration to TLC
- Closure to the glottis
- Contraction of ab muscles
- Opening of glottis + an explosive breath out
What does a huff do?
Can vary the size of the breath in for a huff + this will affect where the secretions are moved from w/in the lungs (i.e. central/peripheral)
Components of an effective huff: (4)
- Breath in to specified volume
- Keep glottis open
- Contract ab muscles
- Controlled force expiration of specified volume
The 3 main concepts of cough + huff:
- 2 Phase gas-liquid flow
- Dynamic compression
- Equal pressure point
2 phase gas-liquid flow:
2
- Explains the interaction of liquid (airway secretions) + gas (air) w/ a conduit (airway)
- Responsible for how secretions move towards the mouth
Annular flow:
The surface of the liquid layer moves in waves
Mist flow:
The liquid is carried as small droplets in the gas
For gas-liquid flow to occur towards the mout the expiratory flow rate must be at least:
10% greater than inspiratory flow rate.
- cough has a higher expiratory flow + uses mist flow
- Huff has lower flow rates + uses annular flow
Dynamic compression:
- During a forced expiration some parts of airways narrow
- Leads to high airflow (velocity) + turbulence which causes shearing of the mucus layer + gas-liquid interaction
Dynamic compression occurs:
towards the mouth @ the equal pressure point (EPP)
Equal pressure point (EPP)
The point where intrapleural pressure is = to alveolar pressure
What happens when Ppl>Pal
Dynamic compression > faster flow rate > movement of secretions
Low volume cough does:
- Moves peripheral secretions
- Small breath in > Less alveolar recoil > Less alveolar pressure to start with
High volume huff/cough can:
- Can clear secretions that are more central to upper airways
- Big breath in > more alveolar recoil > greater alveolar pressure to start with
Postural drainage:
Positioning the bronchus to a particular lung segment uppermost + perpendicular to horizontal to allow secretions to drain by gravity. (peripheral > central)
- Secretions removed by cough
Common postural draining positions:
- L&R horizontal side-lying
- Supine 30 degree head up
- Prone horizontal
- Upright sitting
Percussion
- 1-10 min.
- Imparts mechanical energy to airways to : loosen secretions, increase expiratory flow rate, + change mucus rheology
- Useful in patients w/ excessive secretions
Vibrations/shaking
- Patient takes max inspiration to TLC then applies vib/ in the direction of normal movement of ribs during EXPIRATION
Phys. of vibrations/shaking
- Increases peak expiratory flow rate (PEFR)
- Aids 2 phase gas-liquid flow via annular flow
- Decreases mucus viscosity
- Elicits spontaneous cough
