The cardiopulmonary response at the onset of exercise has been studied extensively, from the early work of Krogh and Lindhard (1913) until recently. The aim of this work was to provide a graphical user interface (GUI) for the study of the cardiopulmonary response at the onset of exercise, in particular the interactions between the volume of blood shifting between the trunk and the extremities (Vbs) and alveolar gas exchange (Vgas). Vbs was calculated as the difference between chest wall volume (Vcw) and lung volume variations (Vbox) measured simultaneously by opto-electronic plethysmography (OEP) and whole-body plethysmography (WBP), respectively; a technique referred to as double-body plethysmography (DBP). A volume displacement WBP in which Vbox was measured by a spirometer was initially implemented. Evaluation of this system showed that the compliance of the WBP did not allow accurate measurement of volume displacement. A flow WBP was thus implemented. To reduce the noise superimposed on Vbox due to changes in temperature and humidity during exercise, an algorithm based on the measurement of psychometric correction to detrend Vbox accordingly. To correct the drift due to mathematical integration of the flow signal to obtain Vbox, a wavelet based algorithm controlled by physiological parameters was implemented. To compute Vgas, the drift in mouth volume (Vm) was corrected using Vcw as a reference; then gas fractions at the mouth (Fgas) were corrected for instrumental delay and aligned with Vm to account for dead space delay. The product of Vm and Fgas was used to compute Vgas breath-by-breath. To assess the functionality of the Matlab GUI, three subject performed quiet breathing, exercise and vital capacity maneuvers within the setup. Vbs swings obtained by our algorithm were comparable in amplitude with the results obtained previously and appeared to reflect better the intra-breath variations. Oxygen uptake computed by our algorithm was comparable in shape and amplitude to the gold standard. Despite technical limitations, he results obtained are encouraging. Collection on a much larger sample size will allow for more conclusive statements on the results.
La risposta cardiopolmonare all’inizio dell’esercizio è argomento di molti studi a partire da quello di Krogh and Lindhard (1913). Obiettivo di questo lavoro è fornire un’ interfaccia grafica (GUI) per lo studio della risposta cardiopolmonare all’inizio dell’esercizio, in particolare l’interazione fra il volume di sangue che si sposta fra il tronco e le estremità dell’organismo (Vbs) e il gas scambiato a livello alveolare (Vgas). Vbs risulta dalla differenza tra il volume della gabbia toracica (Vcw) e le variazioni di volume polmonare (Vbox) misurate tramite la pletismografia opto-elettronica (OEP) e a box (WBP); l’insieme delle due tecniche è chiamato double-body plethysmography (DBP). Inizialmente la variazione di volume generata nel box è stata misurata tramite uno spirometro, ma la verifica di questo sistema ha mostrato che la compliance della cabina non permetteva una accurata misurazion. Per cui si è passati alla misurazione del flusso. Per ridurre la deriva di Vbox dovuta ai cambiamenti termodinamici della cabina durante l’esercizio, è stato sviluppato un apposito algoritmo basato sui segnali di temperatura e umidità. Per correggere la deriva generata dall’operazione di integrazione del flusso per il calcolo di Vbox, è stato sviluppato un automatico filtraggio basato sulla trasformata wavelet rispettoso delle componenti fisiologiche dei segnali. Per il calcolo di Vgas, la deriva del volume alla bocca (Vm) è stata corretta utilizzando Vcw come riferimento mentre è stata corretto il ritardo della concentrazione di gas (Fgas) dovuto alla risposta dello strumento e allo spazio morto. Il prodotto di Vm e Fgas è usato per calcolare Vgas respiro per respiro. Per valutare il funzionamento della GUI sviluppata in Matlab, sono stati acquisiti tre soggetti: le variazioni di Vbs ottenuto sono confrontabili con i risultati di precedenti lavori e apparentemente più stabili nelle variazioni intra-respiro. L’ossigeno scambiato calcolato dall’algoritmo proposto risulta confrontabile in forma e dimensioni con il gold standard. Nonostante le limitazioni tecniche i risultati sono incoraggianti e l’aumento del numero di acquisizioni potrebbe portare a conclusioni definitive.
New methods and techniques for determining V'O2 and blood shift from the thorax to the extremities during exercise on a breath-by-breath basis
CAZZANIGA, GIACOMO
2016/2017
Abstract
The cardiopulmonary response at the onset of exercise has been studied extensively, from the early work of Krogh and Lindhard (1913) until recently. The aim of this work was to provide a graphical user interface (GUI) for the study of the cardiopulmonary response at the onset of exercise, in particular the interactions between the volume of blood shifting between the trunk and the extremities (Vbs) and alveolar gas exchange (Vgas). Vbs was calculated as the difference between chest wall volume (Vcw) and lung volume variations (Vbox) measured simultaneously by opto-electronic plethysmography (OEP) and whole-body plethysmography (WBP), respectively; a technique referred to as double-body plethysmography (DBP). A volume displacement WBP in which Vbox was measured by a spirometer was initially implemented. Evaluation of this system showed that the compliance of the WBP did not allow accurate measurement of volume displacement. A flow WBP was thus implemented. To reduce the noise superimposed on Vbox due to changes in temperature and humidity during exercise, an algorithm based on the measurement of psychometric correction to detrend Vbox accordingly. To correct the drift due to mathematical integration of the flow signal to obtain Vbox, a wavelet based algorithm controlled by physiological parameters was implemented. To compute Vgas, the drift in mouth volume (Vm) was corrected using Vcw as a reference; then gas fractions at the mouth (Fgas) were corrected for instrumental delay and aligned with Vm to account for dead space delay. The product of Vm and Fgas was used to compute Vgas breath-by-breath. To assess the functionality of the Matlab GUI, three subject performed quiet breathing, exercise and vital capacity maneuvers within the setup. Vbs swings obtained by our algorithm were comparable in amplitude with the results obtained previously and appeared to reflect better the intra-breath variations. Oxygen uptake computed by our algorithm was comparable in shape and amplitude to the gold standard. Despite technical limitations, he results obtained are encouraging. Collection on a much larger sample size will allow for more conclusive statements on the results.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/135426