1. Session 7: Assessing weak cough and testing respiratory muscle strength

2. Why respiratory muscle testing?
Are the respiratory muscles weak?
How severe is the weakness?
Is the extent of the muscle weakness clinically important?
Are all the respiratory muscles affected equally?
Is the weakness deteriorating or improving over time?
(ARTP 2005)
Are the respiratory muscles weak? – how do they compare to reference values, are they within normal limits?
How severe is the weakness? – What it the pecent below LLN
Is the extent of the respiratory muscle weakness clinically important?
Are all respiratory muscles affected equally? – are there tests for specific respiratory muscles – yes we’ll descuss these further on in the presentation.
Is the weakness deteriorating over time? – Its important to trend patients results, we often find that there are hight correlations between a patient VC and SNIP pressure measurements and bith may have a equall decline as the patient begins to deteriorate.

3. Vital capacity (VC) (Hough 2001)
Volumes
Vital capacity (VC) (Hough 2001)
Lung function should be within a predicted range based on:
Age - Height - Gender - ethnicity
Normal VC = 3 – 6 L. Or 80% of TLC
For adequate cough: >1L.

4. Why vital capacity (VC)?
Measures ventilatory reserve in a
Indicates ability to breathe deeply and cough.
Reflects inspiratory and expiratory muscles strength.
VC is sometimes reduced in obstructive disorders.
VC is always reduced in restrictive disorders.
Malnourished and obese. patients.

5. Assessing cough effectiveness
Inspiratory phase:
vital capacity
Sniff nasal inspiratory pressure
Maximum inspiratory pressure
Glottic closure:
Staccato expiration from Maximum inspiratory capacity?
Expiratory phase:
Peak cough flow
Maximum expiratory pressure
Audible cough

6. Respiratory muscle function tests
Volitional
(Used Frequently)
Vital Capacity
Mouth pressure (Pe max and Pi max)
Sniff pressures
Cough PEF
Invasive – Volitional Methods
(Infrequent use)
Sniff oesophageal pressure
Cough gastric pressures
Non – Volitional
Electrical stimulation
Magnetic stimulation
So here is a list of the tests that can be conducted to test respiratory muscle strength.
Most laboratories will test muscle strength using non-invasive volitional tests. Mainly because these are less invasive and simple and providing you have a trained/competent practitioner results will be sound.

7. Vital capacity Simple Widely available Non-invasive
Advantages
Simple
Widely available
Non-invasive
Serial measurements easy
Disadvantages
Volitional
Non-specific
Insensitive in mild/moderate disease
Vital Capacity. A test to assess how much air the patient can breath in and out the lungs in one long breathe from a position of full inspiration.
Advantages/Disadvantages
VC measures can be done in a sitting a supine position to detect abnormalities within the diaphragm. In normal subjects the decline is less that 10% whilst in patients with diaphragmatic paralysis the difference may be more that 25%.
(ARTP 2005)

8. Sniff pressures non–invasive widely available and inexpensive
Advantages
non–invasive
widely available and inexpensive
serial measurements easy
high pressures exclude significant respiratory muscle weakness
reference values available
Disadvantages
Volitional
Difficult with bulbar disease
Impaired transmission of pressure in COPD
Normal values
SNIP >60(F) - >70(M)
Sniff pressure offers a simples non invasive alternative to mouth pressures. Advantage being that this is a familiar manoeuvre.
Inserting a plug containing a pressure catheter into one nostril so that its distal end is within the nose opening. Patient then required to perform maximal sniff (From FRC) through the contralateral nostril whilst keeping the mouth closed. This generate a negative pressure in the nasopharynx that is similar to oesophageal pressure as an indication of global inspiratory muscle strength.
In patients with COPD the transmission of the negative intrathoracic pressure to the nose is dampened so that the sniff is less negative, underestimating muscle strength.
Hand-held device for measuring sniff nasal inspiratory pressure (SNIP).
(ARTP 2005)

9. Don’t forget the PCEF (more this afternoon)

10. Patient example
SNIF
05/07/ cmH2O
15/08/ cmH2O
21/11/ cmH2O
09/01/ cmH2O
20/02/ cmH2O
This data demonstrates the fall in vital capacity and corresponding fall in VC of a patient with MND over 4 years

11. Signs of respiratory compromise for those without access to spirometry, PEF or SNIPS
increased respiratory rate
shallow breathing
recurrent chest infections
weak cough
quiet voice
weak sniff
abdominal paradox
use of accessory muscles of respiration
reduced chest expansion on maximal inspiration
drop on usual sPO2 <94%.

12. Lung volumes

13. Living with and managing a weak cough
To support a weak cough you need to:
support the mucocillary escalator
support the inspiratory muscles
support the vocal cords
support the expiratory muscles
or all of these.

14. Supporting the Mucociliary escalator
mobilise the phlegm
hydration
mucolytics
breathing techniques.
mucociliary escalator video

15. https://www. bing. com/videos/search
Mucociliary escalator breathin

16. Supporting the inspiratory muscles
Breath stacking
It allows patients to achieve an inspiratory lung volume close to total lung capacity. FRC = functional residual capacity; TLC = total lung capacity.
Modified by permission from McKim D. Canadian Respiratory Journal 2008:15.

17. Supporting the inspiratory muscles
Breath stacking.
Lung Volume Recruitment (LVR) bag.

18. Supporting the inspiratory muscles
Breath Stacking
Lung Volume Recruitment bag
Glossopharyngeal breathing video

19.
Glossopharyngeal breathing

20. Supporting the expiratory muscles
Manual Assisted Cough
Own and patient size? Eight of bed? Strength, pain relief? Suction?

21. Doing all three: Mechanical insufflator/exsufflator
Emerson Cough assistor
Nippy Clearway
E 70 Cough assistor
‘The MI/E uses positive pressure to promote maximal lung inflation followed by an abrupt switch to negative pressure to the upper airway – the rapid change stimulates the flow changes that occurs during a cough’ (Chatwin et al 2003)

22. Increasing muscle weakness Expiratory techniques
Schematic representation of the management of cough augmentation (Chatwin & Simonds 2007)
Increasing muscle weakness
Combination of all techniques
Cough assist
Combination of inspiratory and expiratory techniques
Inspiratory techniques:
Pressure breathing (IPPB)
Breath stacking
Non invasive ventilation (NIV)
Intermittent positive pressure breathing (IPPB)
Expiratory techniques
Cough assist techniques
Worsening peak cough flow