Automatic detection of AutoPEEP during controlled mechanical ventilation

ABSTRACT: BACKGROUND: Dynamic hyperinflation, hereafter called AutoPEEP (auto-positive end expiratory pressure)with some slight language abuse, is a frequent deleterious phenomenon in patients undergoingmechanical ventilation. Although not readily quantifiable, AutoPEEP can be recognized onthe expiratory portion of the flow waveform. If expiratory flow does not return to zero beforethe next inspiration, AutoPEEP is present. This simple detection however requires the eye ofan expert clinician at the patient's bedside. An automatic detection of AutoPEEP should behelpful to optimize care. METHODS: In this paper, a platform for automatic detection of AutoPEEP based on the flow signalavailable on most of recent mechanical ventilators is introduced. The detection algorithms aredeveloped on the basis of robust non-parametric hypothesis testings that require no priorinformation on the signal distribution. In particular, two detectors are proposed: one is basedon SNT (Signal Norm Testing) and the other is an extension of SNT in the sequentialframework. The performance assessment was carried out on a respiratory system analog andex-vivo on various retrospectively acquired patient curves. RESULTS: The experiment results have shown that the proposed algorithm provides relevant AutoPEEPdetection on both simulated and real data. The analysis of clinical data has shown that theproposed detectors can be used to automatically detect AutoPEEP with an accuracy of 93%and a recall (sensitivity) of 90%. CONCLUSIONS: The proposed platform provides an automatic early detection of AutoPEEP. Such functionalitycan be integrated in the currently used mechanical ventilator for continuous monitoring of thepatient-ventilator interface and, therefore, alleviate the clinician task.     

Glycine Betaine as a Direct Substrate for Methanogens (Methanococcoides spp.)

Nine marine methanogenic Methanococcoides strains, including the type strains of Methanococcoides methylutens, M. burtonii, and M. alaskense, were tested for the utilization of N-methylated glycines. Three strains (NM1, PM2, and MKM1) used glycine betaine (N,N,N-trimethylglycine) as a substrate for methanogenesis, partially demethylating it to N,N-dimethylglycine, whereas none of the strains used N,N-dimethylglycine or sarcosine (N-methylglycine). Growth rates and growth yields per mole of substrate with glycine betaine (3.96 g [dry weight] per mol) were similar to those with trimethylamine (4.11 g [dry weight] per mol). However, as glycine betaine is only partially demethylated, the yield per methyl group was significantly higher than with trimethylamine. If glycine betaine and trimethylamine are provided together, trimethylamine is demethylated to dimethyl- and methylamine with limited glycine betaine utilization. After trimethylamine is depleted, dimethylamine and glycine betaine are consumed rapidly, before methylamine. Glycine betaine extends the range of substrates that can be directly utilized by some methanogens, allowing them to gain energy from the substrate without the need for syntrophic partners.     

Involvement of Autonomic Nervous Activity Changes in Gastroesophageal Reflux in Neonates during Sleep and Wakefulness

Background

It has been suggested that disturbed activity of the autonomic nervous system is one of the factors involved in gastroesophageal reflux (GER) in adults. We sought to establish whether transient ANS dysfunction (as assessed by heart rate variability) is associated with the occurrence of GER events in neonates during sleep and wakefulness.

Methods

Nineteen neonates with suspected GER underwent simultaneous, synchronized 12-hour polysomnography and esophageal multichannel impedance-pH monitoring. We compared changes in HRV parameters during three types of periods (control and prior to and during reflux) with respect to the vigilance state.

Results

The vigilance state influenced the distribution of GER events (P<0.001), with 53.4% observed during wakefulness, 37.6% observed during active sleep and only 9% observed during quiet sleep. A significant increase in the sympathovagal ratio (+32%, P=0.013) was observed in the period immediately prior to reflux (due to a 15% reduction in parasympathetic activity (P=0.017)), relative to the control period. This phenomenon was observed during both wakefulness and active sleep.

Conclusion

Our results showed that GER events were preceded by a vigilance-state-independent decrease in parasympathetic tone. This suggests that a pre-reflux change in ANS activity is one of the factors contributing to the mechanism of reflux in neonates.     

Actin polymerisation at the cytoplasmic face of eukaryotic nuclei

Background  

There exists abundant molecular and ultra-structural evidence to suggest that cytoplasmic actin can physically interact with the nuclear envelope (NE) membrane system. However, this interaction has yet to be characterised in living interphase cells.     

ERK is involved in the reorganization of somatosensory cortical maps in adult rats submitted to hindlimb unloading

Sensorimotor restriction by a 14-day period of hindlimb unloading (HU) in the adult rat induces a reorganization of topographic maps and receptive fields. However, the underlying mechanisms are still unclear. Interest was turned towards a possible implication of intracellular MAPK signaling pathway since Extracellular-signal-Regulated Kinase 1/2 (ERK1/2) is known to play a significant role in the control of synaptic plasticity. In order to better understand the mechanisms underlying cortical plasticity in adult rats submitted to a sensorimotor restriction, we analyzed the time-course of ERK1/2 activation by immunoblot and of cortical reorganization by electrophysiological recordings, on rats submitted to hindlimb unloading over four weeks. Immunohistochemistry analysis provided evidence that ERK1/2 phosphorylation was increased in layer III neurons of the somatosensory cortex. This increase was transient, and parallel to the changes in hindpaw cortical map area (layer IV). By contrast, receptive fields were progressively enlarged from 7 to 28 days of hindlimb unloading. To determine whether ERK1/2 was involved in cortical remapping, we administered a specific ERK1/2 inhibitor (PD-98059) through osmotic mini-pump in rats hindlimb unloaded for 14 days. Results demonstrate that focal inhibition of ERK1/2 pathway prevents cortical reorganization, but had no effect on receptive fields. These results suggest that ERK1/2 plays a role in the induction of cortical plasticity during hindlimb unloading.