LCI 2014 and Beyond
LCI: Lessons learnt in the lung function lab Dr Patrick Stafler Pulmonary Institute Schneider Children’s Medical Center of Israel ChIPaP February 2015 Today Physiology Recap Lung Clearance Index Slope III Analysis Key Publications in 2014 Lessons learnt Conclusions and Future Prospects Physiology Recap Lung Clearance Index Number of volume turnovers required to “washout” tracer to 1/40th of initial concentration Peripheral airway function (generation 8+) Ventilation homogeneity/ in-homogeneity • Functional Residual Capacity FRC = Vol tracer C init – C end • Lung Clearance Index LCI = CEV FRC Slope III Analysis Diffusion- Convection Front Convection Diffusion Alveolar Bronchial Deadspace Rise of SnIII over time (CF) Tidal N2 multiple breath washout (MBW) from a 15-year girl with cystic fibrosis (CF). Volym (L) 1.000 0.500 0.000 N2 % 80 N2 % 70 #1 60 # 23 50 N2 (%) Vol 40 Vol 30 20 10 0 0 30 60 90 120 Tid (s) 150 180 210 Verbank 1997 Convection dependent inhomogeneity Diffusion-convection interaction dependent inhomogeneity SF6 = MM 146 He= MM 4 N2= MM 28 Key Publications 2014 Lung Clearance Index 2014 n=45 Asthma Aim: Compare LCI in asthma and controls Assess effect of salbutamol in children with asthma on LCI Methods: Outpatients with asthma compared to healthy controls MBW using SF6 Results: 32 asthma (4.7-17.4 years) and 42 controls (5.3-20.8) LCI differed: mean LCI 6.48 (0.48) vs 6.21 (0.38) (P = 0.008) Salbutamol had no significant effect on LCI for asthmatics (SF6!) Conclusion: Asthmatics have LCI in the normal range LCI in asthma is significantly higher Esophageal Atresia Purpose: Methods: 28 patients operated for EA: Questionnaire, spiro & MBW Results: Investigate peripheral AW dysfunction vs spirometry 22/28 (79%) patients respiratory symptoms 17 (61%) abnormal peripheral AW function 6 (21%) central obstruction Conclusion: Peripheral airway disease is common in EA Long-term follow-up of (peripheral) AW warranted CF Aim: Compare repeatability, sensitivity and test duration of LCI 1/30, 1/20 and 1/10 to standard 1/40 Methods: 30 clinically stable CF vs 30 healthy controls Results: CF: Repeatibility (CV%) in all concentrations not significantly different to controls Sensitivity of LCI 1/40, LCI1/30 and LCI1/20 to presence of CF equal (67%) Sensitivity of LCI 1/ 10 and FEV1% pred. lower (53% and 47%) Test duration of LCI 1/30, 1/20 and 1/10 significantly shorter than 1/40 Conclusions: LCI1/20 shorter, repeatable and sensitive measure with equal diagnostic performance to LCI1/40 Lessons learnt So far... Number of MBW tests (n=34) 1 ILD Post BMT 4 Asthma 4 7 PCD 18 CF 0 2 4 6 8 10 12 14 16 18 ... but the quality? Good 14 Acceptable 6 Unacceptabl e14 Get the basics right Sit upright Use silicon mouth piece Breath on "true" FRC- find it during pre-phase No swallow in first 5 breaths Remain air tight Switch off auto-start Check entire circuit No coughing Inspiratory peak flow must not exceed bias flow Get the basics right Check for re-equalibration Between trials check O2 and N2 levels Despite "locked system" for 1.5 times washout Intake form- fill in during test for QC CetN2 falsely low with small breaths/ falsely high with deep breaths Check the tidal volumes of the 3 breaths below target to ensure endpoint accurate N2 leak Patient side Sample line Maintain breathing pattern Changes in TV unacceptable Hyperventilation- change in Cet CO2 Shifting EEL- 23 yo PCD; FEV1 80% Reset target alveolar concentration WO time 5.51 mins LCI 12.4 More physiological Shortens washout Shifting EEL- 23 yo PCD; FEV1 80% Check BTPS WO time 5,51 mins LCI 12.4 Direct effect on CO2 WO time 4,31 mins LCI 10.1 7 yo Post BMT Good short test in young child 17 yo Asthma FVC 113% 112% FEV1 76% 91% (19%) MEF 49% 71% (44%) FeNO 38.6 (<20) 12 yo CF ABPA; Pre- Ivacaftor FEV 76% 97% LCI 14.9 Conclusions and Future Prospects Preliminary conclusions It‘s not all about the number Don‘t start research studies without experience Tests takes a long time Chose patients carefully The future Longitudinal measurements Evaluate multitude of disease processes Shorter tests (single breath, LCI 5) Insights about location of various disease processes Different techiniques E.g. SBW from FRC more sensitive than RV? Assessment of trapped gas VC maneuvres at end of wash out
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