medical management and assessment of respiratory system in ... · respiratory physiology summary...

Medical management and Medical management and assessment of respiratory system assessment of respiratory system

in neuromuscular diseasein neuromuscular disease

A Respiratory physiology perspective

Andrew MorleyAndrew Morley (BSc Hons, RPSGT),(BSc Hons, RPSGT),

Manager of the Respiratory Physiological services,Manager of the Respiratory Physiological services,

Royal Hospital for Children, Glasgow.Royal Hospital for Children, Glasgow.

Respiratory PhysiologyRespiratory Physiology

PlanPlan•• Why do Lung Function? Why do Lung Function?

•• When to ask for a sleep study ?When to ask for a sleep study ?

•• Which sleep study to ask for ?Which sleep study to ask for ?

•• Positive pressure therapiesPositive pressure therapies


• Inspiratory vital capcity <60% - Predicts sleep disordered breathing

• Inspiratory Vital capacity <40% - predicts Nocturnal hypoventilation


Pulmonary function tests

• MIP & MEP

– (PIPS & PEPS)

• Spirometry

• Lung Volumes


Pulmonary function tests

• MIP & MEP

– (PIPS & PEPS)

• Spirometry

• Lung Volumes

maximum inspiratory pressure (MIP) maximum

expiratory pressure (MEP) measures the strength

of the muscles that are used during normal & forced

breathing in & out

Measuring how much air you can breathe out in one

forced breath.

Measures the volume of air in the lungs, including

the air that remains at the end of a normal breath.

May also include diffusing capacity test this

measures how easily oxygen enters the

bloodstream.

https://www.whatwhychildreninhospital.org.uk/breathing-test


VC / FVC

(Forced) vital

capacity

TV – Tidal Volume

IC

Inspiratory

Capacity

ERV

Expiratory Reserve Volume

RV

Residual volume

TLC

Total Lung capacity

FRC

Functional Residual Capacity


TLC – normal RV - normal

Flow - normal

Normal


TLC – reduced = restriction RV - normal

Flow - > normal

Restriction


• Inspiratory vital capcity

<60% - Predicts sleep

disordered breathing


What is Sleep Disordered Breathing?

“Sleep-disordered breathing is an umbrella term for several chronic conditions in which partial or complete cessation of breathing occurs

many times throughout the night”

• This could be as a result of Obstructive or Central events


How do you assess for Sleep Disordered Breathing?


Sleep Basics


Sleep Basics

•• Sleep stages (REM & NREM)Sleep stages (REM & NREM)

•• Stage N1Stage N1

•• Stage N2: Light sleepStage N2: Light sleep

•• Stage N3: Deep sleepStage N3: Deep sleep

•• REM Rapid eye movementREM Rapid eye movement


Ventilation

REM:


•Muscle atonia

•Breathing more variable, erratic patterns, similar to wakefulness

• Intercostal muscles show virtually no respiratory activity

• Increased abdominal (diaphragm) contribution to ventilation

• � � ventilation

NREM:

• Regular breathing pattern (automatic control)• � ventilation

“I need a sleep study?”


• Overnight Oximetry

• Overnight Oximetry & Transcutaneous CO2

• Cardio respiratory study (CRSS or Polygraphy)

• Polysomnogrpahy (PSG)



• Overnight Oximetry

• Overnight Oximetry & Transcutaneous CO2

• Cardio respiratory study (CRSS or Polygraphy)

• Polysomnogrpahy (PSG)


What is pulse oximetry ?


What does Oximetry tell you?

• Oxygen Saturatione.g. Normoxic, Hypoxic,

Supplementary oxygen requirement

3 channels !!!

• Heart rate

• Plethsmography signal


What does Oximetry tell you?

• Oxygen Saturatione.g. Normoxic, Hypoxic,

Supplementary oxygen requirement

3 channels !!!

• Heart rate

• Plethsmography signal


Advantages

• Oximetry provides a Non-invasive marker

• Cheap

• Inpatient or Outpatient - limited supervision

• Easy to administer

• Provides continuous monitoring &

recording of blood oxygenation

• Provides desaturation index ( DI/hr)

• Pre and Post Tx studies – e.g O2, NPA

• Good sensitivity for severe OSA


LTOT : assessment


Clinical question : Can the patient come off Oxygen ?

Air 0.25 L O2 / Min


NPA Out

NPA in situ

Heart rate

NPA OutNPA in situ

Clinical question : Is the NPA working?

- Heart baseline increases, increased WOB?

•• AASM: AASM: Oximetry lacks the specificity and sensitivityOximetry lacks the specificity and sensitivity to be used as anto be used as analternative to PSG or an attended respiratory (type 3) study foralternative to PSG or an attended respiratory (type 3) study for diagnosingdiagnosingsleep related breathing disorders sleep related breathing disorders ((www.aasmnet.org/PracticeParameterswww.aasmnet.org/PracticeParameters))

Limitations


Transcutaneous CO2 monitoringTranscutaneous CO2 monitoring


Why measure Transcutaneous CO2?

• Assess ventilation- Hypercapnic

- Hypocapnic

• Assess stage of condition- Daytime CO2

• Assess effectiveness of ventilator

settings (vent check)


Cardiorespiratory Sleep study

(CRSS / Polygraphy)

http://www.ankitparakh.com/

What is a CRSS?

• Multi channel sleep investigation

• Records breathing patterns and any associated oxygen desaturations

• Provides measurements such as- AHI – Obstruction or central

- DI – Desaturation index

- CO2 trends


Limited PSG:

Cardiorespiratory

Sleep study (CRSS)

Setup– Airflow – (Hypopneas)

– Thermistor – (Apnoeas)

– Respiratory Effort (Tho & Abd)– ECG

– Leg EMG– Snore

– Pulse oximetry

– Video– CO2 (ETCO2 or TransCO2)

Somnomedics

Optional




Obstructive apnoea

• ≥90% reduction in airflow for 2 missed breaths during

baseline breathing

• continued or � respiratory effort

Central Apnoea


• ≥90% reduction in airflow for 2 missed

breaths during baseline breathing

• No respiratory effort/movement

•• DMD patientDMD patient

Duchenne Muscular Dystrophy patient.


• CPAP

• NIV / Bilevel

Picture taken from Resmed website


Continuous Positive Airways Pressure (CPAP)

CPAP can be used to :-

• Splint airways the upper airway opene.g. OSA, Anatomy, Post extubation stridor

• Splint small airways e.g. Bronchiolitis, Asthma- where airways

collapse on expiration

• Improve Lung compliance

• Recruit small airways & alveoli

Sullivan CE. Lancet 1981; 1(8225):862-5


• DMD patient� VT � VT x rate = �MV


Bilevel or BiPAP

Two pressures – Inspiratory (IPAP) & Expiratory (EPAP)

• Bilevel therapy is used when the problem is not just obstructive in origin.

• Bilevel therapy is needed when there are

- Central Apnoeas

- Hypoventilation

- Carbon dioxide retention

- Overlap syndrome : Downs syndrome (Obstructive & Central Apnoeas)


• DMD corrected overnight oxygen saturation tracings

� VT � VT x rate = �MV

�VT �VT x rate = � MV


Initiating NIV can be difficult


Initiating NIV can be difficult

• Patients do not always find this an easy therapy to use.

“It was like an endurance test every night”

• Medical/Health care professionals often underestimate patient concerns.

• Patient / Parent can be very anxious

(NIV is often associated with milestones in a condition)


Sensation:

“CPAP is like trying to breath while having

your head stuck out the car window”


• Uncomfortable

• Claustrophobic

• Communication - Talking difficult

Physical:-

• Growth defects


Physical:-

• Pressure Sores



• DMD Mortality

Eagle et al Neuromuscular Disorders 2002;12:926-929

• Never be too pleased with yourself


Case Study

•15 year old Prader-Willi Syndrome

• SBD? , Snores, Tiredness

• CRSS

CRSS

• AHI = 20.7/hr

(Central Apnoeas =18.1/hr)

• Desat. Index = 21.3/hr

NIV establishment(Inpatient admission – 3 nights)


SUMMARY

Respiratory physiology have an important role to play in the

assessment and management of Neuromuscular patients.

NIV therapy is a very successful treatment, however the

level of skill, time & effort required to make this an effective

treatment should not be underestimated.

Thanks for listening.

[email protected]

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