significato clinico e tecniche di misura

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1 Il ruolo delle piccole vie aeree nella patogenesi Resistenze, e clinica conduttanze della BPCO e FOT: significato clinico e tecniche di misura Dott. Roberto Torchio Responsabile S.S.D. Laboratorio Fisiopatologia Respiratoria e Centro Disturbi Respiratori nel Sonno Dipartimento Fisiopatologia Cardio-Respiratoria AOU S.Luigi Orbassano Torino

2 P totale = P per gonfiare + P per vincere resistenze P totale = (Volume/Compliance) + (Flusso/Raw) Alveolo Via aerea

3 La pressione necessaria per espandere polmoni ha 2 componenti: 1- componente elastica (per gonfiare il polmone) 2- componente resistiva (per far passare l aria nelle vie aeree)

4 V R V R I

5 Resistenza del segmento (cmh 2 O*s/l) Vie aeree superiori 0.5 Apertura delle vie aeree (bocca o naso) Laringe Vie aeree inferiori 0.8 Trachea Vie aeree di conduzione Raw R L Rrs Tessuti Polmonari 0.2 Tessuti Parete toracica 0.5 Alveoli Tessuti polmonari Parete toraco-addominale Totale = 2.0

6 I. Properties of the dynamic lung V V = P R = P P R A B P R = V

7 Studio delle proprieta meccaniche del sistema respiratorio: misure con sistemi palloncino-catetere-trasduttore Flusso all apertura delle vie aeree Polmoni Stima della pressione pleurica tramite misura della pressione esofagea Parete toraco-addominale Pressione esercitata dai muscoli respiratori

8 RL= PLres / Flusso 0.5 [ PLelast = PL = Vt0.5 x EL,dyn, ]

9 Interruptor method

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11 C. Experimental determination of airway resistance To do this, we utilize the relationship established for determining airflow. V V = P R R = P V 1) subject is placed in a plethysmograph which has meters to measure mouth pressure (P M ), box pressure (P BOX ) and pneumotachometer which measures air flow. All air is drawn from inside the box from a tube containing a valve.

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13 BOYLE s law PV = K P 1 V 1 = P 2 V 2

14 ΔP A (a) TGV ΔV BOX (b) t a α b/a = cosα/senα = ctg α = ΔV BOX / ΔP A TGV = ctg α = cos α a/b = tg α = ΔP A / ΔV BOX sin α t b Raw V (a) ΔV BOX (b) t t a β b Raw = tg α tg β

15 Limitazione al flusso espiratorio P = RV

16 Effect of interdependence on airway caliber Lung Volume Lung Volume Airway caliber Raw

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18 tgα 1 tg β Raw = Gaw = = tg β Raw tgα G aw tg β / tgα tg β. tgα sg aw = = = TGV (=1/tgα) (1/tgα) tgα Se errori nel TGV (angolo α) Li elimino

19 1956: DuBois, A. B., A. W. Brody, D. H. Lewis, and B. F. Burgess. Oscillation mechanics of lungs and chest in man. J.Appl.Physiol. 8: Forced Oscillation Technique Tecnica utilizzabile per misurare le proprieta meccaniche del sistema respiratorio durante respiro spontaneo in modo non invasivo e in soggetti scarsamente collaborativi

20 In matematica una funzione è il dato di tre oggetti: un dominio X, un codominio Y e una legge x ƒ(x) che associa ad ogni elemento x di X uno e un solo elemento di Y che viene indicato ƒ(x). Y X U.Frey 2004 mod.

21 Time Domain Signals Pressure and flow are time domain signals they are measured and plotted against time U.Frey 2004 mod.

22 There are many complex time domain signals are made up of a number of different sine waves with different: Frequency sample amplitudes phases

23 One frequency

24 Two frequencies

25 Rectangular pulse: all frequencies

26 Sum of two frequencies

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28 Frequency Domain Signals Breaking a signal into its component parts transforms a signal from the time domain to the frequency domain. The technique used to do this is called Fourier transformation

29 U.Frey 2004 mod.

30 Sum of two frequencies

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32 Forced Oscillation Technique (FOT) Oscillatory Pressure Pressure oscillations Airway opening flow Chest wall Pressure developed by respiratory muscles

33 Impedance Resistance Reactance 1 Power spectral density of airway opening pressure Pressure (cmh 2 O) Spontaneous breathing ) 2 O) Forced oscillations Flow (l/s) ins Power ( (cmh Frequency (Hz) 5 s

34 V R V R I

35 U.Frey 2004 mod.

36 U.Frey 2004 mod.

37 Impedance changes with frequency due to changes in both in-phase (resistive) and out-of-phase (reactive) elements Accurate characterisation of the frequency dependance of lung mechanics requires representation of both and phase. Respiratory system impedance (Z rs ) is often written in the form: Z rs = R rs + X rs j where R rs is resistance, X rs is reactance and j describes the phase component of the reactance. U.Frey 2004 mod.

38 Describing Phase Using Imaginary Numbers U.Frey 2004 mod.

39 Derivation of the Value of j

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41 Eur Respir J 2004; 23: /03/12

42 pressure waves generate pressure in the lungs waves are reflected in the lungs reflected waves carry information about the pressure at different places in the lungs flow measured via PT reflected waves are analysed in respect of pressure and frequency

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47 Impedance Resistance Reactance 1 Power spectral density of airway opening pressure Pressure (cmh 2 O) Spontaneous breathing ) 2 O) Forced oscillations Flow (l/s) ins Power ( (cmh Frequency (Hz) 5 s

48 Respiratory impedance Z rs Includes airways resistance and inertive behaviour of lungs and chest wall at one oscillation frequency

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52 Reattanza (X rs ) : Componente fuori fase della relazione Pressione Flusso La reattanza è attribuibile a 2 componenti fuori fase : uno legato alle proprietà elastiche e capacitative uno alle proprietà inertive. Quando la frequenza di oscillazione aumenta il valore della dissipazione di pressione elastica diminuisce, mentre quello della dissipazione di pressione legata alla inertanza aumenta. Per questo a bassa frequenza di oscillazioni (5Hz) le proprietà capacitative delle piccole vie aeree dominano la reattanza della FOT.

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54 Impulse Penetration Slow Impulses 5Hz Fast Impulses 20 Hz

55 Xrs5

56 Frequency Dependence of Impedance (Z) U.Frey 2004 mod.

57 Signal Frequency o < 4 Hz for tissue (apnoea) o 5-30 Hz airways o > 100 Hz serial distribution airway diameters/airway wall properties

58 Baseline Histamine

59 Delta R5-R19

60 Disadvantages of FOT Tends to focus on resistance What is the right frequency which index to report Impact of tissues on R rs at any given frequency will vary o Different diseases o Maturation Does not adequately quantify tissue mechanics

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62 The IOS system is different from the classical FOT because an impulse (a rectangular wave form) rather than a pseudorandom noise signal (a mixture of several sinusoidal wave forms) is applied and because of differences in data processing. The IOS signal contains a limited number of frequencies while the latter does not have this limitation. The signal-to-noise ratio for the FOT, keeping the magnitude of the overall signal within acceptable limits and reducing the number of frequencies, increases the power at each frequency.

63 pseudo random noise is a signal similar to noise which satisfies one or more of the standard tests for statistical randomness. Although it seems to lack any definite pattern, Pseudo-random noise consists of a deterministic sequence of pulses that will repeat itself after its period.

64 The fact that the Rrs values obtained with IOS and FOT are related to each other should not lead to the conclusion that they are interchangeable.

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70 P.V = k P. V = k Se gas toracico sotto pressione misurando alla bocca il flusso ( volume al secondo ) Il valore sarà più basso

71 Cambio volume alla bocca (compressione) Cambio volume in cabina (no compressione)

72 Ingram R.H, Schilder D.P JAP 1966; 21:

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75 POST beta 2

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77 SANO XM_insp ott-08 nov-08 dic-08 gen-09 feb XM_exp ott-08 nov-08 dic-08 gen-09 feb DeltaXrs ott-08 nov-08 dic-08 gen-09 feb-09 14/03/12

78 ASMATICO 0.0 XM_insp ott-08 nov-08 dic-08 gen-09 feb XM_exp ott-08 nov-08 dic-08 gen-09 feb DeltaXrs ott-08 nov-08 dic-08 gen-09 feb-09 14/03/12

79 Gobbi et al 2012 Asthma inter-day variability

80 Home monitoring clinical study Prediction of future extreme values of Rrs Prediction window τ: 4 days Time scale φ: 2, 4, 8 days Time scale φ: 8 days Prediction window τ: 4, 7, 15, 30 days A φ = 8 days generates a predictor close to the ideal shape, i.e. a step function Gobbi et al 2012 The predictors with τ up to 15 days maintain a good ability to discriminate extreme events

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