Experimental investigation of the viability of using nano-bubbles for intravascular oxygenation

Smit, Mynhardt (2020-03)

Thesis (MEng)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: In the human body sufficient oxygen supply is of utmost importance. In certain critical conditions the lungs cannot sufficiently supply the human body subsequently other forms of oxygenation are required to potentially save the patients life. Equipment currently available for the purpose of oxygenation is often unaffordable and unavailable. The use of nano-bubbles for intra-vascular oxygenation is envisioned to possibly solve this problem. To determine if this is a viable option to be further investigated, the validation process is broken into multiple phases starting with a basic system that simulates some properties of the pulmonary system, such as flow rate, pipe diameter and systolic pressure while using water as working fluid. This thesis focussed on the first phase and serves as baseline research into the important factors associated with generating nano-bubbles using membranes. The focus of this project is to determine the effects of membrane nominal pore size, oxygen inlet pressure and acoustic interference on oxygenation of a fluid using membranes. To test the effect of these factors an experimental setup was designed, using water as working fluid, that is used to introduce oxygen bubbles into water through a membrane. Flat sheet and tubular membranes were used to introduce oxygen into the system. Two different inlet manifolds were designed to mount these membranes. Box-Behnken design was used to determine the different combinations of pore size, pressure and frequency that is to be tested and a dissolved oxygen probe was used to measure the levels of dissolved oxygen in the water associated with each combination of variables. The results obtained during experimentation was analysed, and functions were fitted to the data. The fit of the function was analysed using analysis of variance. The effect of each variable was investigated and discussed. The obtained function was then optimised using a genetic algorithm to determine the expected optimum dissolved oxygen levels. The results showed evidence that pore size, pressure and frequency influence the level of dissolved oxygen in the mixture. Using the flat sheet membrane, it was determined that the near optimum point is expected to be at 10 nm, a pressure of 2.8 bar and a frequency of 200 Hz. The effect of bubble size and zeta potential on the level of dissolved oxygen in water was investigated. It was expected that a decrease in bubble diameter would lead to an increase in dissolved oxygen levels. At a zeta potential between −9 mV and −22 mV it was observed that a decrease in bubble diameter does indeed lead to an increase in dissolved oxygen. Two sets of tests were done using the tubular ceramic membranes. Data from the sets of experiments, using tubular ceramic membranes, were combined, disregarding data obtained using the 100 nm membrane due to leakages affecting the data. It was determined that increasing the pressure, pore size and frequency lead to an increase in DO2. As the overarching aim of the project is to be able to sufficiently oxygenate a human intravenously. Considering the evidence obtained, it cannot be concluded that using membranes with nano-scale pores are a viable method for blood oxygenation, as the measured DO2 obtained in water is relatively low. The main concern, however, is the formation of large oxygen bubbles. One of the properties of nano-bubbles is that they are neutrally buoyant and that due to their negative surface charge they can stay in a mixture for long periods of time. It is hypothesised that during experimentation, nano-bubbles were generated, but remain stable in the water. As these bubbles possibly did not dissolve the dissolved oxygen levels possibly does not reflect the available oxygen. Further investigation is suggested.

AFRIKAANSE OPSOMMING: In die menslike liggaam is voldoende suurstofvoorraad uiters belangrik. In sekere kritieke toestande kan die longe nie die menslike liggaam voldoende van suurstof voorsien nie, en dan is ander vorme van oksigenasie nodig om die pasiient se lewe te red. Toerusting wat tans beskikbaar is met die oog op bloed oksigenasie, is dikwels onbekostigbaar en nie algemeen beskikbaar nie. Die gebruik van nano-borrels vir intravaskul^ere oksigenasie word voorgestel om hierdie probleem moontlik op te los.Om te bepaal of dit 'n lewensvatbare opsie is om verder te ondersoek, word die valideringsproses in verskillende fases verdeel, beginnend met 'n basiese stelsel wat 'n paar eienskappe van die pulmonale stelsel simuleer, soos vloeitempo, pypdiameter en sistoliese druk terwyl water gebruik word as werksvloeier. Hierdie tesis fokus op die eerste fase en dien as basislyn-ondersoek na die belangrike faktore wat verband hou met die opwekking van nano-borrels met behulp van membrane. Die fokus van hierdie projek is om die effekte van membraan nominale poriegrootte, suurstofinlaatdruk en akoestiese interferensie op oksigenering van vloeistof met behulp van membrane te bepaal. Om die effek van hierdie faktore te toets, was 'n eksperimentele stelses ontwerp, waar water as werkvloeistof gebruik was, om suurstofborrels deur die membraan in die water in te bring. Platvel- en buisvormige membrane was gebruik om suurstof in die stelsel in te voer. Twee verskillende inlaatspruitstukke was ontwerp om hierdie membrane te monteer. Box-Behnken-ontwerp was gebruik om die verskillende kombinasies van poriegrootte, druk en frekwensie wat getoets moet word te bepaal, en 'n opgeloste suurstof meter word gebruik om die vlakke van opgeloste suurstof in die water, wat met elke kombinasie van veranderlikes geassosieer word, te meet. Die resultate wat tydens eksperimentering verkry was, was ontleed, en 'n funksie was op die data gepas. Die pas van die funksie was geanaliseer met behulp van variansie-analise. Die effek van elke veranderlike was ondersoek en bespreek. Die verkrygde funksie was toe geoptimaliseer met behulp van 'n genetiese algoritme om die verwagte optimale opgeloste suurstofvlakke te bepaal. Die resultate het bewys dat poriegrootte, druk en frekwensie die vlak van opgeloste suurstof in die mengsel benvloed. Deur die gebruik van die platvelmembrane is daar bepaal dat die naaste optimale punt na verwagting by n poriegrootte van 10 nm sal wees, 'n druk van 2; 8 bar en 'n frekwensie van 200 Hz. Die e ek van borrelgrootte en zeta-potensiaal op die vlak van opgeloste suurstof in water is ondersoek. Daar word verwag dat 'n afname in borreldiameter sou lei tot 'n toename in opgeloste suurstofvlakke. By 'n zeta-potensiaal tussen -9 mV en -22 mV is daar waargeneem dat 'n afname in borreldiameter lei wel tot 'n toename in opgeloste suurstof. Twee stelle toetse was met behulp van die buisvormige keramiek membrane gedoen. Data van die stelle eksperimente, met behulp van buisvormige keramiek membrane, was gekombineer, met uitsluiting van data wat verkry was met behulp van die 100 nm membraan weens lekkasies wat die data benvloed. Daar was bepaal dat die verhoging van die druk, poriegrootte en frekwensie lei tot 'n toename in DO2. Vir hierdie gekombineerde stel data was vasgestel dat die suurstofdruk en die frekwensie van die klankgolf wat die stelsel vibreer die mees beduidende invloed het op die vlak van DO2. Die oorkoepelende doel van die projek is om 'n vir mens genoegsame suurstof binneaars te kan toedien. Met inagneming van die bewyse wat verkry was, kan daar nie afgelei word dat die gebruik van membrane met nanoskaalsporiee 'n lewensvatbare metode is om suurstof in bloed te bewerkstellig nie, aangesien die vlak van DO2 wat in water verkry is, relatief laag is. Die grootste bekommernis is egter die vorming van groot suurstofborrels op sekere plekke op die membraan. Een van die eienskappe van nano-borrels is dat hulle neutraal dryf en dat hulle as gevolg van hul negatiewe oppervlaktelading gedurende 'n lang periode in 'n mengsel kan bly, soos gellustreer deur die eksperiment wat deur Meegoda et al. (2018) gedoen is. Daar word veronderstel dat nano-borrels tydens eksperimentering gegenereer word en stabiel in die water bly. Aangesien dit moontlik is dat hierdie borrels nie oplos nie, weerspiel die opgeloste suurstofvlakke moontlik nie die totale beskikbare suurstof nie. Verdere navorsing word voorgestel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107999
This item appears in the following collections: