In domestic animals, it’s of primary importance the evaluation of the pressure state in order to avoid the numerous diseases that may result from hypertension. The persistent increase of blood pressure can cause serious alterations in some structures defined target-organs that, for anatomical and functional characteristics, are particularly affected by the high blood pressures, represented by the cardiovascular system, central nervous system, from kidney and eye. The invasive methods for measuring and monitoring blood pressure, although providing highly accurate measurements, have high risks (especially in cats) resulting from catheterization as the possibility of verify infections, hematoma, tissue necrosis, thrombosis and embolism. Furthermore, the use of invasive techniques is in contrast with the increasingly strict regulations regarding the protection of animals used for purposes of scientific experimentation (Directive 86/609/CEE). Nowadays there is a preference, even in the veterinary field, the use of non-invasive devices. In some animals, such as rabbits, the small size of limbs, the presence of coat and the low intensity of transduced signal, do not allow a good measurement and in fact there are no devices that do the continuous non-invasive monitoring of blood pressure using one cuff only. The present study proposes a possible solution in order to solve the problems described above, thanks to the planning, realization and validation of a device for measuring and continuous non-invasive monitoring waveform blood pressure in laboratory animals and/or small domestic animals. The system initially, through the implementation of the oscillometric method, research the calibration values namely systolic, diastolic and mean pressure. Then the device performs the continuous monitoring of blood pressure by inflating the cuff until it reaches the diastolic pressure value. This phase ends when the operator decides to stop or repeat the measure going to update the pressure values. Once achieved the device, the experiments were carried out for the subsequent validation. In particular this procedure, carried out on an almost homogeneous sample of 10 rabbits (sedated and anesthetized before the measurement), is based on a comparison of blood pressure recorded non-invasively by our system, with the pressures obtained by catheterization of the artery located in the animal’s ear. Moreover during the validation, it was possible to perform also a calibration of the device, in order to estimate the parameters (specific for each rabbit) to be used in the algorithm for calculating the systolic and diastolic pressure. The analysis conducted on 10 rabbits shows the sensitivity and accuracy of the measurements performed by the device. As regards the sensitivity of the system, is observed, qualitatively, a good correspondence between the signals acquired in invasive and non-invasive mode. Furthermore from the comparison of these signals, is confirmed quantitatively the accuracy of the system by calculating the systolic and diastolic percentage relative error between the invasive and non-invasive measures. In particular, during calibration of system, the calculated error is approximately zero on the median value while, whereas the values distributed between the first and third quartiles, is around ± 1%. Moreover, from elaboration of the values recorded in calibration phase, optimal parameters were identified to minimize systolic and diastolic error rate obtained values 0.65 and 0.76 respectively. Finally analyzing the measurements acquired during the waveform monitoring of arterial pressure occurs an error close to zero on the median value (about ± 2% on data between the first and third quartiles).
Negli animali da affezione, è di fondamentale importanza la valutazione dello stato pressorio al fine di evitare le numerose patologie che possono derivare dall’ipertensione. L’aumento persistente della pressione sistemica può causare, infatti, gravi alterazioni a carico di alcune strutture definite organi-bersaglio che, per caratteristiche anatomiche e funzionali, risentono particolarmente delle elevate pressioni sanguigne, e sono rappresentati dal sistema cardiovascolare, dal sistema nervoso centrale, dal rene e dall’occhio. Le metodiche invasive per la misurazione ed il monitoraggio della pressione arteriosa, pur fornendo misure molto accurate, presentano rischi elevati (ad esempio nel gatto) derivanti dal cateterismo come la possibilità di riscontrare infezioni, ematomi, necrosi tissutale, trombosi ed embolie. Inoltre, l’uso di tecniche invasive è in contrasto con la sempre più severa regolamentazione in materia di protezione degli animali utilizzati a scopo di sperimentazione scientifica (direttiva 86/609/CEE). Ad oggi quindi si predilige, anche in ambito veterinario, l’utilizzo di dispositivi non invasivi. In alcuni animali, come ad esempio i conigli, le ridotte dimensioni degli arti, la presenza del pelo e la bassa intensità del segnale trasdotto, non consentono una buona misurazione ed infatti non ci sono dispositivi che consentono il monitoraggio continuo non invasivo della forma d’onda della pressione arteriosa, usando un solo manicotto. Detto questo, nel presente lavoro di tesi si è progettato, realizzato e validato un dispositivo per la misurazione e il monitoraggio continuo non invasivo della forma d’onda della pressione arteriosa in animali da laboratorio e/o in piccoli animali da affezione: il sistema inizialmente, attraverso l’implementazione del metodo oscillometrico, ricerca i valori di calibrazione ovvero la pressione sistolica, media e diastolica. In seguito il dispositivo compie il monitoraggio continuo gonfiando il manicotto fino a raggiungere il valore di pressione diastolica. Questa fase termina nel momento in cui l’operatore decide di fermare o ripetere la misura andando ad aggiornare i valori pressori. Una volta realizzato il dispositivo, sono stati svolti degli esperimenti per la successiva validazione. In particolare questa procedura, effettuata su un campione pressoché omogeneo di 10 conigli (sedati e anestetizzati prima della misurazione), si basa sul confronto dei valori pressori registrati in modo non invasivo dal nostro sistema, con le pressioni ottenute mediante la cateterizzazione dell’arteria situata nell’orecchio dell’animale. Durante la validazione inoltre, si è potuta effettuare anche una taratura del dispositivo, allo scopo di stimare i parametri (specifici per ogni coniglio) da utilizzare nell’algoritmo per il calcolo delle pressioni sistolica e diastolica. L’analisi delle prove svolte sui 10 conigli mostra la sensibilità e l’accuratezza delle misure effettuate dal dispositivo. Per quanto concerne la sensibilità del sistema, si nota, qualitativamente, una buona corrispondenza tra i segnali acquisiti in modo invasivo e non invasivo. Dal confronto di questi segnali inoltre, viene confermata quantitativamente l’accuratezza del sistema calcolando l’errore relativo percentuale sistolico e diastolico tra le misure invasive e non invasive. In particolare, in fase di calibrazione del sistema, l’errore calcolato è circa nullo sulla mediana mentre, considerando i valori distribuiti tra il primo e il terzo quartile, è attorno al ±1%. Inoltre, sempre dall’elaborazione dei valori registrati in calibrazione, sono stati individuati i parametri ottimi per minimizzare l’errore relativo percentuale sistolico e diastolico ottenendo rispettivamente i valori 0.65 e 0.76. Infine analizzando le misure acquisite durante il monitoraggio della forma d’onda della pressione arteriosa si evidenzia un errore pressoché nullo sulla mediana (circa ±2% sui dati compresi tra il primo e il terzo quartile).
Dispositivo per la misura ed il monitoraggio continuo non invasivo della pressione arteriosa in animali da laboratorio e/o in piccoli animali da affezione
MARCHI, ANDREA
2010/2011
Abstract
In domestic animals, it’s of primary importance the evaluation of the pressure state in order to avoid the numerous diseases that may result from hypertension. The persistent increase of blood pressure can cause serious alterations in some structures defined target-organs that, for anatomical and functional characteristics, are particularly affected by the high blood pressures, represented by the cardiovascular system, central nervous system, from kidney and eye. The invasive methods for measuring and monitoring blood pressure, although providing highly accurate measurements, have high risks (especially in cats) resulting from catheterization as the possibility of verify infections, hematoma, tissue necrosis, thrombosis and embolism. Furthermore, the use of invasive techniques is in contrast with the increasingly strict regulations regarding the protection of animals used for purposes of scientific experimentation (Directive 86/609/CEE). Nowadays there is a preference, even in the veterinary field, the use of non-invasive devices. In some animals, such as rabbits, the small size of limbs, the presence of coat and the low intensity of transduced signal, do not allow a good measurement and in fact there are no devices that do the continuous non-invasive monitoring of blood pressure using one cuff only. The present study proposes a possible solution in order to solve the problems described above, thanks to the planning, realization and validation of a device for measuring and continuous non-invasive monitoring waveform blood pressure in laboratory animals and/or small domestic animals. The system initially, through the implementation of the oscillometric method, research the calibration values namely systolic, diastolic and mean pressure. Then the device performs the continuous monitoring of blood pressure by inflating the cuff until it reaches the diastolic pressure value. This phase ends when the operator decides to stop or repeat the measure going to update the pressure values. Once achieved the device, the experiments were carried out for the subsequent validation. In particular this procedure, carried out on an almost homogeneous sample of 10 rabbits (sedated and anesthetized before the measurement), is based on a comparison of blood pressure recorded non-invasively by our system, with the pressures obtained by catheterization of the artery located in the animal’s ear. Moreover during the validation, it was possible to perform also a calibration of the device, in order to estimate the parameters (specific for each rabbit) to be used in the algorithm for calculating the systolic and diastolic pressure. The analysis conducted on 10 rabbits shows the sensitivity and accuracy of the measurements performed by the device. As regards the sensitivity of the system, is observed, qualitatively, a good correspondence between the signals acquired in invasive and non-invasive mode. Furthermore from the comparison of these signals, is confirmed quantitatively the accuracy of the system by calculating the systolic and diastolic percentage relative error between the invasive and non-invasive measures. In particular, during calibration of system, the calculated error is approximately zero on the median value while, whereas the values distributed between the first and third quartiles, is around ± 1%. Moreover, from elaboration of the values recorded in calibration phase, optimal parameters were identified to minimize systolic and diastolic error rate obtained values 0.65 and 0.76 respectively. Finally analyzing the measurements acquired during the waveform monitoring of arterial pressure occurs an error close to zero on the median value (about ± 2% on data between the first and third quartiles).| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/45822