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Which parameters are practical in evaluating the efficacy of mechanical ventilation?. Turkish Thoracic Society 11 th Annual Congress Antalya, Turkey April 2008. Gökhan M. Mutlu, M.D. Pulmonary and Critical Care Medicine Northwestern University Feinberg School of Medicine.
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Which parameters are practical in evaluating the efficacy of mechanical ventilation? Turkish Thoracic Society 11th Annual Congress Antalya, Turkey April 2008 Gökhan M. Mutlu, M.D. Pulmonary and Critical Care Medicine Northwestern University Feinberg School of Medicine Financial Disclosure: Nothing to disclose
Goals of mechanical ventilation Treatment of respiratory failure Life support Supporting respiratory muscles Correction of hypoxemia and hypercapnia Prevention of complications associated with mechanical ventilation Barotrauma (i.e., pneumothorax, pneumomediastinum) VILIMOSF
Goals of mechanical ventilation 1. Monitor vital signs, ABG and airway pressures 2. Small VT 6 ml/kg in ALI/ARDS 6-8 ml/kg in obstructive airway disease 3. Keep Pplat < 30 cm H2O 4. Administer enough PEEP to improve oxygenation 5. Keep FiO2 < 0.6
Common parameters in monitoring MV Clinical Vital signs SpO2 Gas exchange Invasive Arterial blood gas (SaO2, PaO2, pH, PaCO2) Non-invasive SpO2 VO2 ETCO2
Common parameters in monitoring MV Lung and chest wall mechanics Paw (Ppeak and Pplat) Compliance and elastance Airway resistance Auto-PEEP P-V relationship
Resistance (Raw) Plateau Pressure Compliance (Csrs) Measurement of lung mechanics Peak Pressure 30 Airway Pressure (cm H2O) 20 10 PEEP Time
Airway pressures Ppeak =Presistive+ Pelastance + Pinertia Ppeak = (Flow x Resistance) + (VT x Elastance) Ppeak = (Flow x Resistance) + (VT x 1/Compliance)
PIPvsPplat PIP High Raw Normal PIP PPlat PPlat Paw (cm H2O) PIP PPlat Low Compliance Time (sec)
Compliance and airway resistance Compliance (static)RS= ΔV/ΔP CRS= VT/Pplat-PEEP Normal values- 60-80 ml/cm H2O Severely decreased compliance <25 ml/cm H2O Resistance Constant flow 60 L/min (1L/sec) PIP - Pplat cmH2O L/sec Normal < 15 cmH2O/L/sec
Airway pressures Parenchymal diseases (Pneumonia, ALI, ARDS, pulmonary edema) ↑ Ppeak ↑ Pplat ↓ Compliance Airway diseaseas (COPD, asthma) ↑ Ppeak N Pplat ↑ Airway resistance Auto-PEEP
Normal Patient Normal vs. Obstruction Inspiration Time (sec) Flow (L/min) } Expiration
Auto-PEEP Determination Auto PEEP Expiration Inspiration Paw (cm H2O) Total PEEP Set PEEP Time (sec) Expiratory hold
Case 1 34 yo woman with no PMH CC: productive cough, fever and pleuritic chest pain Exam: RR-34/min, SpO2 81% on RA, crackles at both bases Labs: WBC 21,000/mm3, 98% PMNs BUN 31, Crea 1.2
Case 2 41 yo man with history of asthma CC: SOB, wheezing, not responding to q2 hour SABA Exam: RR-37/min, SpO2 92% on RA, decreased BS BL, prolonged exp, and wheezing Labs: WBC 14,000/mm3, 84% PMNs, 11% eos ABG 7.24/60/62
Effects of a 50%shunt on oxygenation 150 CxO2 = 1.39*HG*% sat + PO2*0.003 21% oxygen 100 15 20 CvO2=15 PvO2 = 45 SvO2 = 75% CcO2=20 PcO2 = 100 ScO2 = 98% 17.5 CaO2=17.5 PaO2 = 57 SaO2 = 87%
Effects of 100% oxygen in 50% shunt 713 CxO2 = 1.39*Hgb*% sat + PO2*0.003 100% oxygen 650 15 22 CvO2=15 PvO2 = 45 SvO2 = 75% CcO2=22 PcO2 = 650 SaO2 = 100% 18.5 CaO2=18.5 PaO2 = 65 SaO2 = 92%