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STEFANO NAVA. Clinical importance of respiratory mechanics ISTANBUL 8 May 2010. Fondazione Maugeri-IRCCS-Pavia Pneumologia Riabilitativa e Terapia Intensiva Respiratoria. Problems. Diagnosis Need for mechanical ventilation Settings of mechanical ventilation
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STEFANO NAVA Clinical importance of respiratory mechanics ISTANBUL 8 May 2010 Fondazione Maugeri-IRCCS-Pavia Pneumologia Riabilitativa e Terapia Intensiva Respiratoria
Problems • Diagnosis • Need for mechanical ventilation • Settings of mechanical ventilation • Patient/ventilator interaction • Weaning from mechanical ventilation
espiration Flow Pdi Pga Pes inspiration Pdi= Pga – (-Pes) = Pdi= Pga + Pes + _
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 inspiration Flow Volume Paw Pes Pga Pdi 320 ml - 5 cmH20 1 cmH20 6 cmH20
Supine inspiration Flow Volume Paw Pes Pga Pdi 150 ml - 15 cmH20 - 14 cmH20 1 cmH20
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
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
Pdi per breath is 50% of the maximal inspiratory pressure Flow Pdi Pga Pes 18 cmH20 9cmH20 MIP Tidal Breathing
From Sherer and Monod, 1956 30 * * * * 20 * * * Time limit (min.) * * * * * 10 * * * * * * * * * * * * * * * * 0 100 0 50 Force (% of Force max.)
= normal 100% = stable COPD = ARF 50% Ti/Tot 0.15 Fatigue treshold 50% 0 100% Pdi/Pdimax
Weakness Hyperinflation FORCE Elastance PEEPi Resistance LOAD
Ventilator Bronchodilators FORCE LOAD
Apparently there is nothing wrong on what you see on the ventilator
But if you could see the neural activity of the patient…..
Conclusions 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: high auto-PEEP high Pressure Support severe pump failure.
If you measured PEEPi with the balloon-catheter technique set the appropriate amount of external PEEP
US= the usual ventilator settings PHYS= the ventilator settings according the recording of respiratory mechanics
Elevated static compliance STRONG indicator of weaning failure
100% 50% Ti/Tot TTdi 0.15 Fatigue treshold 50% 0 100% Pdi/Pdimax