Reduction of CPR artifacts in the ventricular fibrillation ECG by coherent line removal

<p>Abstract</p> <p>Background</p> <p>Interruption of cardiopulmonary resuscitation (CPR) impairs the perfusion of the fibrillating heart, worsening the chance for successful defibrillation. Therefore ECG-analysis <it>during ongoing chest compression </it>could provide a considerable progress in comparison with standard analysis techniques working only during "hands-off" intervals.</p> <p>Methods</p> <p>For the reduction of CPR-related artifacts in ventricular fibrillation ECG we use a localized version of the <it>coherent line removal </it>algorithm developed by Sintes and Schutz. This method can be used for removal of periodic signals with sufficiently coupled harmonics, and can be adapted to specific situations by optimal choice of its parameters (e.g., the number of harmonics considered for analysis and reconstruction). Our testing was done with 14 different human ventricular fibrillation (VF) ECGs, whose fibrillation band lies in a frequency range of [1 Hz, 5 Hz]. The VF-ECGs were mixed with 12 different ECG-CPR-artifacts recorded in an animal experiment during asystole. The length of each of the ECG-data was chosen to be 20 sec, and testing was done for all 168 = 14 × 12 pairs of data. VF-to-CPR ratio was chosen as -20 dB, -15 dB, -10 dB, -5 dB, 0 dB, 5 dB and 10 dB. Here -20 dB corresponds to the highest level of CPR-artifacts.</p> <p>Results</p> <p>For non-optimized <it>coherent line removal </it>based on signals with a VF-to-CPR ratio of -20 dB, -15 dB, -10 dB, -5 dB and 0 dB, the signal-to-noise gains (SNR-gains) were 9.3 ± 2.4 dB, 9.4 ± 2.4 dB, 9.5 ± 2.5 dB, 9.3 ± 2.5 dB and 8.0 ± 2.7 (mean ± std, <it>n </it>= 168), respectively. Characteristically, an original VF-to-CPR ratio of -10 dB, corresponds to a variance ratio <it>var</it>(VF):<it>var</it>(CPR) = 1:10. An improvement by 9.5 dB results in a restored VF-to-CPR ratio of -0.5 dB, corresponding to a variance ratio <it>var</it>(VF):<it>var</it>(CPR) = 1:1.1, the variance of the CPR in the signal being reduced by a factor of 8.9.</p> <p>Discussion</p> <p>The <it>localized coherent line removal </it>algorithm uses the information of a single ECG channel. In contrast to multi-channel algorithms, no additional information such as thorax impedance, blood pressure, or pressure exerted on the sternum during CPR is required. Predictors of defibrillation success such as mean and median frequency of VF-ECGs containing CPR-artifacts are prone to being governed by the harmonics of the artifacts. Reduction of CPR-artifacts is therefore necessary for determining reliable values for estimators of defibrillation success.</p> <p>Conclusions</p> <p>The <it>localized coherent line removal </it>algorithm reduces CPR-artifacts in VF-ECG, but does not eliminate them. Our SNR-improvements are in the same range as offered by multichannel methods of Rheinberger et al., Husoy et al. and Aase et al. The latter two authors dealt with different ventricular rhythms (VF and VT), whereas here we dealt with VF, only. Additional developments are necessary before the algorithm can be tested in real CPR situations.</p

Substitution of maize with high fibre by-products in concentrates supplemented to dairy cows grazing kikuyu/ryegrass pasture during spring

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011.ENGLISH ABSTRACT: Kikuyu over-sown with ryegrass forms the basis of pasture based systems in the Southern Cape. During early spring, energy is the first limiting nutrient in kikuyu/ryegrass pasture, supplementation is thus essential. Supplementation consists mainly of high starch concentrates (high maize inclusion), which is expensive and could negatively affect rumen parameters. The objective of this study was to determine if milk production could be improved or maintained, and if the rumen environment would be improved, by replacing high starch concentrates with low starch (high by-product) concentrates for dairy cows on kikuyu/ryegrass pasture. Forty-five multiparous, high producing, lactating Jersey cows [body weight, 340 ± 34.7 kg; milk yield (MY), 19.6 ± 2.23kg/d; days in milk (DIM), 153 ± 33.5; lactation number, 3.6 ± 1.85; (mean ± SD)] were used in the production study. A randomised block design was used. The forty-five cows were allocated to fifteen groups of three each (blocking) on the basis of MY, DIM, and lactation number. Cows from each group were randomly allocated to one of three treatment groups (high starch, medium starch and low starch concentrate supplementation). Cows were fed 6kg (3kg during each milking) concentrate per day and were allocated fresh pasture ad lib after each milking. There were no significant differences (P > 0.05) found in milk yield and fat corrected milk yield between treatment groups. Milk fat percentage was significantly higher (P < 0.05) in the low starch treatment than in the high starch treatment. Milk fat yield was significantly higher (P < 0.05) in both the low starch and the medium starch treatment when compared to the high starch treatment. Milk protein and lactose percentages, as well as milk urea nitrogen and somatic cell count, did not differ significantly (P > 0.05) between treatments. Live weight change, as well as body condition score change, was unaffected (P > 0.05) by treatments indicating body reserves were not used to maintain milk production in the low starch treatment. A rumen metabolism study was also done with ten lactating, cannulated Jersey cows [body weight, 332 ± 56.3 kg; MY, 17.3 ± 1.73kg/d (mean ± SD)] were used. The cows were divided into two groups of five each, on the basis of lactation number, DIM, and MY. The five cows from each group were randomly allocated to one of two treatment groups (high starch and low starch concentrate supplementation) and used in a cross-over design. Cows were fed 6kg concentrate per day and were allocated fresh pasture ad lib after each milking. The volatile fatty acid (VFA) concentration was significantly higher (P < 0.05) in the high starch treatment when compared to the low starch treatment. The individual VFA’s, acetic-, propionic- and butyric acid concentrations were also significantly higher (P < 0.05) in the high starch treatments when compared to the low starch treatment. The acetic to propionic acid ratio was unaffected (P > 0.05) by treatment. Rumen ammonia-nitrogen concentration was significantly higher (P < 0.05) in the high starch treatment. Rumen pH was unaffected (P > 0.05) by supplementation type. The in sacco dry matter and neutral detergent fibre digestibilities of the kikuyu/ryegrass pasture were unaffected (P > 0.05) by treatment type. Results indicated that milk production could be maintained with low starch concentrates which also improved milk composition. Results further suggested that the rumen environment was relatively unaffected by low starch concentrate supplementation.AFRIKAANSE OPSOMMING: Kikoejoe, oorgesaai met raaigras, vorm die basis van weidingstelsels in the Suid-Kaap. Tydens die lentemaande is energie die eerste beperkende voedingstof op kikoejoe/raaigras weidings, wat kragvoeraanvulling noodsaaklik maak. Aanvulling bestaan grootliks uit hoëstysel-kragvoer (hoë mielieinhoud) wat nie net duur is nie, maar dit kan ook die rumenomgewing benadeel. Die doel van die studie was om vas te stel of melkproduksievlakke onderhou kan word en of rumenomgewing verbeter kan word deur die vervanging van hoëstysel-kragvoer met laestysel-kragvoer (hoë neweprodukinhoud) vir melkkoeie op kikoejoe/raaigras weidingstelsels. Vyf-en-veertig meervoudige pariteit-, hoë produserende, lakterende Jerseykoeie [liggaamsmassa, 340 ± 34.7 kg; melkproduksie, 19.6 ± 2.23kg/d; dae in melk, 153 ± 33.5; laktasienommer, 3.6 ± 1.85; (gem ± standaardafwyking)] is gebruik vir die produksiestudie van die proef. Daar is gebruik gemaak van ‘n ewekansige blokontwerp. Die vyf-en-veertig koeie is opgedeel in vyftien groepe van drie elk, gebaseer op melkproduksie, dae in melk en laktasienommer. Koeie in elke groep is ewekansig aan een van drie behandelings (hoëstysel-, mediumstysel- of laestysel-kragvoeraanvulling) geallokeer. Koeie is daagliks 6kg (3kg tydens twee milkings) kragvoer gevoer en vars weiding was ad lib beskikbaar na elke melking. Daar was geen beduidende verskil (P > 0.05) in melkopbrengs of vet-gekorrigeerde melkopbrengs tussen die drie behandelings nie. Bottervetpersentasie was beduidend hoër (P < 0.05) in die laestyselbehandeling in vergelyking met die hoëstyselbehandeling. Bottervetopbrengs was beduidend hoër (P < 0.05) in beide die laestysel- en mediumstyselbehandelings in vergelyking met die hoëstyselbehandeling. Melkproteïen- en melklaktosepersentasies, asook melkureumstikstof en somatise seltelling, was onveranderd (P > 0.05) tussen behandelinge. Liggaamsmassa en liggaamskondisietelling het geen verskille (P > 0.05) getoon tussen behandelings nie, wat daarop dui dat liggaamsreserwes nie gebruik is om melkproduksie in die laestyselbehandeling te onderhou nie. ‘n Rumenmetabolismestudie is ook uitgevoer met tien lakterende, gekannuleerde Jerseykoeie [liggaamsmassa, 332 ± 56.3 kg; melkproduksie, 17.3 ± 1.73kg/d (gem ± standard afwyking)]. Die koeie is in twee groepe van vyf elk verdeel, gebasseer op laktasienommer, dae in melk en melkproduksie. Die vyf koeie van elke groep is in ‘n omslagontwerp gebruik en is ewekansig aan een van twee behandelings (hoëstysel- of laestysel-kragvoeraanvulling) geallokeer. Koeie het daagliks 6kg kragvoer ontvang en vars weiding was ad lib beskikbaar na elke melking. Die vlugtige vetsuurkonsentrasie was beduidend hoër (P < 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Die individuele vlugtige vetsure naamlik asynsuur, propionsuur en bottersuur, was ook beduidend hoër (P < 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Die asynsuur- tot propionsuurverhoudings het geen verskille (P > 0.05) tussen behandelings getoon nie. Rumen-ammoniakstikstof was beduidend hoër (P < 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Rumen-pH het geen verskille (P > 0.05) getoon tussen behandelings nie. Die in sacco droëmateriaal- en neutraalbestande veselverteerbaarhede van kikoejoe/raaigras weiding het geen verskille (P > 0.05) tussen behandelings getoon nie. Die resultate het aangedui dat melkproduksie onderhou kan word en dat melksamestelling verbeter kan word met laestysel-kragvoeraanvulling. Resultate het ook daarop gedui dat die rumenomgewing nie noodwendig verbeter word deur die aanvulling van laestysel-kragvoer vir koeie op kikoejoe/raaigras weidings nie