STEFANO NAVASTEFANO NAVA Clinical importance of respiratory

mechanicsISTANBUL 8 May 2010

Fondazione Maugeri-IRCCS-PaviaFondazione Maugeri-IRCCS-Pavia

Pneumologia Riabilitativa e Terapia Intensiva RespiratoriaPneumologia Riabilitativa e Terapia Intensiva Respiratoria

Problems• Diagnosis

• Need for mechanical ventilation

• Settings of mechanical ventilation

• Patient/ventilator interaction

• Weaning from mechanical ventilation

How do we breathe ?

Flow

Pdi

Pga

Pes

Pdi= Pga – (-Pes) = Pdi= Pga + Pes

+

_

inspiration

espiration

Diagnosis

Case report• 47 yrs old lady with a 2-yr history of CHF

(actually NYHA class II) EF=41%

• Fatigue and orthopnea in the last 12 months

• 3 recent ER admission for shortness of breath and increased secretions

• PFT= FEV1=64% pred VC=32% pred

• Mean SaO2 during visit= 92-94%

-Despite NO echographic signs of CHF worsening, she was treated 2 times as CHF decompensation

- Third time she see a pulmonologist, that diagnosed COPD exacerbation (since she was a former smoker)

- Admitted to our Unit where she underwent respiratory mechanics

Sitting

Flow

Volume

Paw

Pes

Pga

Pdi

inspiration

- 5 cmH20

1 cmH20

6 cmH20

320 ml

Supine

Flow

Volume

Paw

Pes

Pga

Pdi

inspiration

- 15 cmH20

- 14 cmH20

1 cmH20

150 ml

Which associated pathology ?• Scleroderma

• Idiophatic Pulmonary Fibrosis

• Severe “intermittent” asthma

• Sjogren syndrome

• Amiotrophyc Lateral Sclerosis

ALS=

Diaphragm paralysis (i.e. inward abdominal movement during inspiration in supine position) may be one of the

first symptom

Need for MV

Another case• 71 yrs old man with a long-lasting

COPD story• On LTOT since 2 yrs• Last ABG before admission= pH=7,38

PaCO2=41 PaO2=65 in oxygen• In the last couple of days worsening

of secretions and dyspea• ABG at admission: pH= 7,34 PaCO2=

46 PaO2=59 in oxygen

• Friday afternoon 16,30

• On call the previous weekend

• Looking forward to watching the defining game of the season on TV

• Choice of starting medical therapy and being home, showered and in front of the TV by 1900

• or trying NIV, maybe failing and getting home, just in time to see the credits

Respiratory mechanics was performed

Flow

Pdi

Pga

Pes

18 cmH20 9cmH20

MIP Tidal Breathing

Pdi per breath is 50% of the maximal inspiratory pressure

Can this guy breathe alone for long ?

*

*

**

**

** *

*

**

*

*

**

*

*

*

*

*

* *

*

*

*

*

*

0

10

20

30

0 50 100

Force (% of Force max.)

Tim

e lim

i t (m

i n.)

From Sherer and Monod, 1956

0 50% 100%Pdi/Pdimax

50%

100%T

i/Tot

0.15

= normal

= stable COPD

= ARF

Fatigue treshold

Not likely to go very far….

FORCE

LOAD

Hyperinflation

Resistance

PEEPi

Elastance

Weakness

FORCE LOAD

Ventilator Bronchodilators

Setting of MV

We seat in front of a ventilator

Apparently there is nothing wrongApparently there is nothing wrongon what you see on the ventilatoron what you see on the ventilator

But if you could see the neuralBut if you could see the neuralactivity of the patient…..activity of the patient…..

Or be more more careful…..Or be more more careful…..

You could find out that there is sometimes a problem

Only 3 of 19 patients (16%), with I/E were weaned. This is in contrast to a weaning success rate of 57%, of those patients without I/E

I/E appeared to result from:

1) high auto-PEEP 2) high Pressure Support3) severe pump failure.

ConclusionsConclusions

If you measured PEEPi withthe balloon-catheter techniqueset the appropriate amount ofexternal PEEP

US= the usual ventilator settingsPHYS= the ventilator settings according the recording of respiratory mechanics

Patient/ventilator interaction

Weaning from mechanical ventilation

“Passive” mechanics

Elevated static complianceSTRONG indicator of weaning failure

“Active” mechanics

Weaning success vs weaning failure

0 50% 100%Pdi/Pdimax

50%

100%T

i/Tot

0.15Fatigue treshold

TTdi

The case of post-surgical patients

Some researchers studying respiratory mechanics at the table

Karakurt Z et al (submited)

Patients ventilated for >15 daysafter a major surgical procedure

Non-weaned vs “late” weaned

Patients with at least 1 weaning failure were compared, usingrespiratory mechanics index, at the time of failure and eventuallylater on at the time of weaning success

ConclusionsThe recordings of respiratory mechanics may be

useful in the clinical practice to:

- Establish a correct diagnosis for difficult cases

- Drive the clinician about “how far” could a patient

sustain her/his spontaneous breathing

- Setting the right ventilator parameters to avoid gross patient/ventilator mismatching

- Predict the weaning success or failure

STABLE PATIENTSNORMALS

19/155=13%19/155=13%