Apneic Oxygenation in Diagnosis and Treatment of Lung Tumours in an Experimental Porcine Model

Objectives: Respiratory movements may complicate diagnostic and therapeutic procedures such as biopsies and stereotactic irradiation therapy in lung cancer patients. An attempt to avoid respiratory movements, up to 30 minutes, long enough for procedures was performed in an animal study.Methods: Ten anaesthetized minipigs ~30 kg were intubated in the trachea and small NiTi-stents were placed in various parts of the lungs. Using a muscle relaxing drug, the pigs were deprived of the ability to breathe for 30 minutes, a longer time than normally used for positioning and irradiation or for biopsies. No attempt to hyperventilate the animals was made prior to the apneic period. After a lung recruitment manoeuvre, a constant oxygen pressure of 20 cm water was applied to the airways. Using X-ray fluoroscopy, the position of the stents and thereby the movements of the lung, were monitored. Arterial gas analyses were performed every 5 minutes during the apneic period.Results: All animals survived 30 minutes of apneic oxygenation. The median arterial oxygen partial pressure actually rose from 11.8 to 54.3 kPa and there were no changes in oxygen saturation. The median arterial carbon dioxide partial pressure rose from 6.9 to 18.7 kPa and the median pH fell from 7.41 to 7.04 during 30 minutes of apneic oxygenation. Our setup, or our strategy of anaesthesia, did not immobilise the internal parts of the lungs satisfactorily, and must be improved before it can be used in a clinical situation. Conclusion: Physiologically, it is possible to stop respiration using apneic oxygenation for periods long enough to perform biopsies or stereotactic radiation therapy

Stop criteria for retransmission termination in soft-combining algorithms

Soft-combining algorithms use retransmissions of the same codeword to improve the reliability of communication over very noisy channels. In this paper, soft-outputs from a maximum a posteriori (MAP) decoder are used as a priori information for decoding of retransmitted codewords. As all received words may not need the same number of retransmissions to achieve satisfactory reliability, a stop criterion to terminate retransmissions needs to be identified. As a first and very simple stop criterion, we propose an algorithm which uses the sign of the soft-output at the MAP decoder. The performance obtained with this stop criterion is compared with the one assuming a genius observer, which identifies otherwise undetectable errors. Since this technique needs always a particular number of initial retransmissions, we exploit cross-entropy between subsequent retransmissions as a more advanced but still simple stop criterion. Simulation results show that significant performance improvement can be gained with soft-combining techniques compared to simple hard or soft decision decoding. It also shows that the examined stop criteria perform very close to the optimistic case of a genius observer

Proactive attack : A strategy for legitimate eavesdropping

In this paper, we study a novel approach to eavesdrop the messages of suspicious users for a surveillance purpose. In particular, we consider a scenario in which the legitimate monitor can act as a jamming source and a decode-And-forward relay station that can force the suspicious users to reveal their exchanged messages. Accordingly, the power allocation policies for the jamming signal of the legitimate monitor subject to deterministic and non-deterministic interference channels are considered. On this basis, we derive a closed-form expression for the successful eavesdropping probability to evaluate the system performance. More importantly, our results reveal that the successful eavesdropping probability of the non-deterministic interference channel from the legitimate monitor to the suspicious receiver outperforms the one of the deterministic interference channel. SafeCOP - Safe Cooperating Cyber-Physical Systems using Wireless Communicatio