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RespiratoryMuscleFunction Assessmentof StrengthandEndurance Load Work of breathing Ventilation Elastic Resistance (Chest wall and Lung) Airway Resistance Capacity of the respiratory pump Substrate / O2 Force Endurance CNSoutput Respiratorydrive Pump Capacity Respiratory musclepump Loadon thepump Ventilatory Failure LOAD RESPIRATORYMUSCLES ● HYPERINFLATION ● OBSTRUCTION ● EDEMA- FIBROSIS ● CHESTWALL ● VENTILATION ● TI/TTOT CAPACITY RESPIRATORYMUSCLES • • • • • • • • • • • HYPERINFLATION CHRONICHEARTFAILURE HYPERCAPNIA- HYPOXAEMIA INACTIVITY NEUROLOGICALCONDITIONS NEUROMUSCULARCONDITION CATABOLISM DRUGS(CORTICOSTEROIDS) INFLAMMATION MALNUTRITION ELECTROLYTEDISTURBANCES STRENGTH • MOUTHPRESSURE (PImax,PEmax) • SNIFFPRESSURE (PSNIFF) • TRANSDIAPHRAGMATICPRESSURE (PDImax) • PHRENICNERVESTIMULATION • CERVICALMAGNETICSTIMULATION Techniquestomeasurerespiratory musclefunction Pdi Psniff O Pmouth Poes Maximalvoluntarycontractions EFFORTDEPENDENT!!!! Pabd Measurementofrespiratorymusclestrength Pressure Force Geometry ofthethorax Mechanical properties (stiffness) PImax isnotameasure ofmusclecontractile properties butrather ameasure ofpressure ALL RESPIRATORYMUSCLESAREINCLUDED VitalCapacity(%pred) 100 80 60 40 20 0 0 20 40 60 80 100 Inspiratorymusclestrength(%pred) DeTroyeretal.Thorax1980,35:603- 610. Maximalstaticpressuresatthemouth • Measurementofpressuregeneratedbyallin- orexpiratory respiratorymusclesANDpassiveelasticrecoiloflungsandchest wall • Advantages: – simpleandquick – welltolerated – non-invasive • Disadvantages – effortdependent – globalmeasurement – resultdependentontechnique,andequipmentused STANDARDISATION OF THE MEASUREMENT: STANDARDISED LUNG VOLUME IS ESSENTIAL Muscle Length Elastic properties lung and chest wall (FRC: ideal elastic properties included) RV: PImax TLC: PEmax FORCE MUSCLELENGTH-TENSIONRELATIONSHIP LENGTH Pressure-VolumeCurve 100 Pcw %ofVitalCapacity 80 PRS 60 40 EELV/FRC 20 PL 0 -60 -40 -20 0 20 40 60 MouthPressure(cmH2O) Rahn H,etal.AmJPhysiol 1946 Respiratorypressureandlungvolume Lungvolume(%TLC) 100 TLC 80 60 FRC 40 Pmus RV 20 -100 PRS Pmus -50 0 Pressure(cmH2O) 50 100 J.T.Sharpetal.ClinChestMed1983,4:421- 432. Theequipment Tube Black&Hyatt(ARRD,1969) cylinder length15.2cm internal diameter 3cm closeddistalend leak, length15mm,i.d. 2mm Smaller leaksresult inlargerpressures (10-20%) Mayos Chest1991;100:364-366 Leakpreventsglottisclosure,andgenerationofpressurebythe facialmuscles Themouthpiece The mouthpiece 16 14 Pressure (kPa) 12 10 ** Flanged Tube ** 8 6 4 2 0 PI max PE max MEP-measurements • Checkcontra-indications(e.g.stressincontinence) • Patientseatedstraight • Explainthemaneuver:emphasisonFORCE,not VOLUME • • • • • Fullinspiration Applymeasuringdevicetothemouth Forcefulexpirationwithstiffcheeks Checkquality,andperformance Repeatuntilreproducible(<5%betweenbest3) MIP-measurements • Patientseatedstraight • Explainthemaneuver:emphasisonFORCE,not VOLUME,explainthesensationofnotgettingairin • Fullexpiration • Applymeasuringdevicetothemouth • Forcefullinspirationwithstiffcheeks (creatingavacuum) • Checkquality,andperformance • Repeatuntilreproducible(<5%betweenbest3) ATS/ERSStatement Respiratory muscle testingAJRCCM2002;161:518-624 VOLUNTARYACTIVATION: FULLCOOPERATIONOFTHE PATIENTIS REQUIRED*! *Assessment inICUpatientswillbe discussed separately Number of repetitions PImax (cmH2O) 80 70 60 50 40 1 2 3 4 5 6 7 8 9 10 11 12 20 Fiz etal.Thorax1989;44:419-421 Inspection of pressure/time curve Start not at RV Not quick enough P Time Normativedata 9 - 18 Age Man Women 19 - 49 50 - 69 -96 ±35 -127 ±28 -112 ±20 -76 ±27 PEmax (cmH2O) 170 ±32 216 ±45 196 ±45 133 ±42 90 ±25 -91 ±25 -77 ±18 -66 ±18 PEmax (cmH2O) 136 ±34 138 ±39 124 ±32 108 ±28 PImax (cmH2O) PImax (cmH2O) > 70 Rochester&Arora1983 ATS/ERSStatement Respiratory muscle testingAJRCCM2002;161:518-624 Istheobtainedresult‘(ab)normal’ ? PImax (cmH 2 O) 180 PImax (kPa) 20 15 10 160 140 120 100 80 60 40 20 5 0 0 0 10 20 30 40 50 0 60 70 80 Age (Yrs) Wijkstra 1995 McConnell 1998 Uldry 1995 Rochester 1983 Hautmann 2000 Heijdra 1993 Enright 1994 Vincken 1987 15 90 100 30 45 60 75 85 Age (yrs) Leech 1983 McElvaney 1989 Ringqvist 1966 Wilson 1984 In:Troosters Eur Respir Mon2005 SNIFFPRESSURE SNIFFPRESSURE Pes Pnp Pmo ATS/ERSStatement Respiratory muscle testing.AJRCCM2002;161:518-624 ENDURANCE • SUSTAINEDNORMOCAPNICHYPERPNEA • INCREMENTALTHRESHOLDLOADING • REPEATED(SUB)MAXIMALINSPIRATORYMANEUVERS SustainedNormocapnicHyperpnea RESPIRATORYMUSCLEENDURANCE Normocapnic Hyperpnoea https://youtu.be/lkmGHMRZpKM Ventilation, L Sustainedventilation ~60-70%MVV Tlim,sec ATS/ERSStatement Respiratory muscle testingAJRCCM2002;161:518-624 Incrementalthresholdloading Gosselink etal.Thorax1996;51:601-605 ATS/ERSStatement Respiratory muscle testingAJRCCM2002;161:518-624 Respiratorymuscleendurance:constant workload Pressureload (%PImax) 100% 75% 50% 25% 5 10 15 20 Endurancetime(Tlim) (min) 25 Variable Resistive IMT Endurancemeasurement • Patientseatedstraight • Explainthemaneuver:emphasisonENDURANCE • Inspiratoryloadapprox.50%PImax • • • • Exhalecompletely Fastandforcefulinspiration Warm-uptrial3-5minat40%Pimax Repeatwhentrialisshorterthan3minorlonger than7minutes Endurance Conclusions • Assessment of respiratory muscle performance is clinically relevant for diagnosis, treatment and evaluation • Assessment of respiratory muscle strength and endurance is feasible and reliable in clinical practice • Practical training is necessary to develop skills in the assessment of respiratory muscle strength and endurance