Investigation of Heart-Lung Function in Smokers Using Integrated Heart-Lung Signal Acquisition System

Integrated heart lung signal acquisition system is a device which helps to acquire ECG and respiratory signals simultaneously and unambiguously. This study deals with the investigation of the functioning of heart and lungs in smokers. The Vernier EKG sensor and Vernier –NTC thermistor were assembled to record the ECG and respiratory signals from 30 subjects. After recording the data were further divided into 2 groups, smokers and non-smokers. R-R interval and the HRV analysis of the ECG signal was done. For the respiratory signal analysis, first respiratory information were extracted from the data and the inspiratory and expiratory volumes were then determined. From the results, it was found that the mean heart rate of the smokers was less than the non-smokers whereas the mean R-R interval was more in case of smokers. From the frequency domain analysis it was observed that there is significant increase in the low frequency (LF) indices in case of smokers and slight increase in the high frequency (HF) indices for non-smokers. Furthermore the LF/HF ratio was higher in case of smokers. The Shannon entropy analysed from the nonlinear indices of HRV was found to be more or less similar for both smokers and non-smokers whereas the Poincare standard descriptors seem to be less for smokers in comparison with the non-smokers. The analysis of the respiratory signals showed that both the inspiratory and expiratory areas under the respective curves were higher for the smokers in comparison to the non-smokers. From all these we can deduce that the sympathetic activity in case of smokers is high as compared to the non-smokers. Thus, the overall study concluded that the integrated data acquisition system is a good methodology to investigate both ECG and respiratory signals. In future, this methodology can be used to find the relation between R-R intervals and breathing intervals to investigate the co-relative function between heart and lungs in various pathological cases

The Effects of Neuromuscular Fatigue on the Complexity of Isometric Torque Output in Humans

The temporal structure, or complexity, of torque output is thought to reflect the adaptability of motor control and has important implications for system function, with high values endowing greater adaptability in response to alterations in task demand. The aim of this thesis was to investigate the effect of neuromuscular fatigue on the complexity of isometric muscle torque output. It was hypothesised that neuromuscular fatigue would lead to a reduction in the complexity of muscle torque output, as measured by approximate entropy (ApEn), sample entropy (SampEn) and the detrended fluctuation analysis (DFA) ? scaling exponent. The first experimental study (Chapter 4) demonstrated that muscle torque complexity was significantly reduced during both maximal and submaximal intermittent fatiguing contractions, with the values at task failure indicative of increasingly Brownian noise (DFA ? > 1.50). It was subsequently shown in the second study (Chapter 5) that this reduction in complexity occurred exclusively during contractions performed above the critical torque. It was next demonstrated, in the third study (Chapter 6), that pre-existing fatigue significantly reduced torque complexity and time to task failure, but still resulted in consistent values of complexity at task failure regardless of the time taken to reach that point. In the fourth study (Chapter 7) caffeine ingestion was found to slow the rate of reduction in torque complexity with fatigue, seemingly through both central and peripheral mechanisms. Finally, in the fifth study (Chapter 8) eccentric exercise decreased the complexity of torque output, with values only recovering to baseline levels after 24 hours recovery, in comparison to only 10 minutes recovery following isometric exercise. These results demonstrate that torque complexity is significantly perturbed by neuromuscular fatigue. This thesis has thus provided substantial evidence that the complexity of motor control during force production becomes less complex, and that muscles become less adaptable, with neuromuscular fatigue