METHODS: An iterative airway pressure reconstruction (IPR) method is used to reconstruct asynchronous airway pressure waveforms to better match passive breathing airway waveforms using a single compartment model. The reconstructed pressure enables estimation of respiratory mechanics of airway pressure waveform essentially free from asynchrony. Reconstruction enables real-time breath-to-breath monitoring and quantification of the magnitude of the asynchrony (MAsyn).
RESULTS AND DISCUSSION: Over 100,000 breathing cycles from MV patients with known asynchronous breathing were analyzed. The IPR was able to reconstruct different types of asynchronous breathing. The resulting respiratory mechanics estimated using pressure reconstruction were more consistent with smaller interquartile range (IQR) compared to respiratory mechanics estimated using asynchronous pressure. Comparing reconstructed pressure with asynchronous pressure waveforms quantifies the magnitude of asynchronous breathing, which has a median value MAsyn for the entire dataset of 3.8%.
CONCLUSION: The iterative pressure reconstruction method is capable of identifying asynchronous breaths and improving respiratory mechanics estimation consistency compared to conventional model-based methods. It provides an opportunity to automate real-time quantification of asynchronous breathing frequency and magnitude that was previously limited to invasively method only.
METHODS: Consecutive patients with a new histological diagnosis of LAPC were recruited over 20 months. Baseline CT and 18FDG PET-CT were performed and repeated after 12 weeks to assess response to treatment. Following 2 cycles of conventional chemotherapy, patients underwent EUS-guided 32P OncoSil implantation followed by a further six cycles of chemotherapy.
RESULTS: Twelve patients with LAPC (8M:4F; median age 69 years, IQR 61.5-73.3) completed the treatment. Technical success was 100% and no procedural complications were reported. At 12 weeks, there was a median reduction of 8.2cm3 (95% CI 4.95-10.85; p=0.003) in tumour volume, with minimal or no 18FDG uptake in 9 (75%) patients. Tumour downstaging was achieved in 6 (50%) patients, leading to successful resection in 5 (42%) patients, of which 4 patients (80%) had clear (R0) resection margins.
CONCLUSIONS: EUS guided 32P OncoSil implantation is feasible and well tolerated and was associated with a 42% rate of surgical resection in our cohort. However, further evaluation in a larger randomized multicenter trial is warranted. (32P funded by OncoSil Medical Ltd, equipment and staff funded by the Royal Adelaide Hospital, ClinicalTrials.gov number, NCT03003078).
METHODS: Gaussian effort model (GEM) is a derivative of the single-compartment model with basis function. GEM model uses a linear combination of basis functions to model the nonlinear pressure waveform of spontaneous breathing patients. The GEM model estimates respiratory mechanics such as Elastance and Resistance along with the magnitudes of basis functions, which accounts for patient inspiratory effort.
RESULTS AND DISCUSSION: The GEM model was tested using both simulated data and a retrospective observational clinical trial patient data. GEM model fitting to the original airway pressure waveform is better than any existing models when reverse triggering asynchrony is present. The fitting error of GEM model was less than 10% for both simulated data and clinical trial patient data.
CONCLUSION: GEM can capture the respiratory mechanics in the presence of patient effect in volume control ventilation mode and also can be used to assess patient-ventilator interaction. This model determines basis functions magnitudes, which can be used to simulate any waveform of patient effort pressure for future studies. The estimation of parameter identification GEM model can further be improved by constraining the parameters within a physiologically plausible range during least-square nonlinear regression.