Monitoring lung impedance changes during long-term ventilator-induced lung injury ventilation using electrical impedance tomography

OBJECTIVE

The target of this methodological evaluation was the feasibility of long-term monitoring of changes in lung conditions by time-difference electrical impedance tomography (tdEIT). In contrast to ventilation monitoring by tdEIT, the monitoring of end-expiratory (EELIC) or end-inspiratory (EILIC) lung impedance change always requires a reference measurement.

APPROACH

To determine the stability of the used Pulmovista 500^® EIT system, as a prerequisite it was initially secured on a resistive phantom for 50 h. By comparing the slopes of EELIC for the whole lung area up to 48 h from 36 pigs ventilated at six positive end-expiratory pressure (PEEP) levels from 0 to 18 cmH₂O we found a good agreement (range of r ² = 0.93-1.0) between absolute EIT (aEIT) and tdEIT values. This justified the usage of tdEIT with its superior local resolution compared to aEIT for long-term determination of EELIC.

MAIN RESULTS

The EELIC was between -0.07 Ωm day^-1 at PEEP 4 and -1.04 Ωm day^-1 at PEEP 18 cmH₂O. The complex local time pattern for EELIC was roughly quantified by the new parameter, centre of end-expiratory change (CoEEC), in equivalence to the established centre of ventilation (CoV). The ventrally located mean of the CoV was fairly constant in the range of 42%-46% of thorax diameter; however, on the contrary, the CoEEC shifted from about 40% to about 75% in the dorsal direction for PEEP levels of 14 and 18 cmH₂O.

SIGNIFICANCE

The observed shifts started earlier for higher PEEP levels. Changes of EELI could be precisely monitored over a period of 48 h by tdEIT on pigs.

Mesenchymal stromal cell-derived extracellular vesicles rescue radiation damage to murine marrow hematopoietic cells

Mesenchymal stromal cells (MSCs) have been shown to reverse radiation damage to marrow stem cells. We have evaluated the capacity of MSC-derived extracellular vesicles (MSC-EVs) to mitigate radiation injury to marrow stem cells at 4 h to 7 days after irradiation. Significant restoration of marrow stem cell engraftment at 4, 24 and 168 h post irradiation by exposure to MSC-EVs was observed at 3 weeks to 9 months after transplant and further confirmed by secondary engraftment. Intravenous injection of MSC-EVs to 500cGy exposed mice led to partial recovery of peripheral blood counts and restoration of the engraftment of marrow. The murine hematopoietic cell line, FDC-P1 exposed to 500cGy, showed reversal of growth inhibition, DNA damage and apoptosis on exposure to murine or human MSC-EVs. Both murine and human MSC-EVs reverse radiation damage to murine marrow cells and stimulate normal murine marrow stem cell/progenitors to proliferate. A preparation with both exosomes and microvesicles was found to be superior to either microvesicles or exosomes alone. Biologic activity was seen in freshly isolated vesicles and in vesicles stored for up to 6 months in 10% dimethyl sulfoxide at -80 °C. These studies indicate that MSC-EVs can reverse radiation damage to bone marrow stem cells.

[Mechanisms causing chronic renal injury in kidney disease and their possible reversibility]

Much study has been dedicated to the understanding of the mechanisms leading to the progression of renal injury and to the development of strategies to limit this progression or possibly induce tissue regeneration. Among several identified mechanisms, the role of angiotensin II is widely recognized. Moreover, the progression of glomerular damage is characterized by capillary loss, reduction of the proliferative response, and production of antiangiogenic factors. Several lines of evidence support the potential effect of therapeutic startegies aimed at interfering with angiotensin II or stimulating angiogenesis in order to reduce the progression of renal injury. Recent work has underlined the potential of strategies involving the use of stem cells. Different populations of stem cells have been identified in the adult kidney. During renal injury, stem cells derived from the bone marrow that migrate through the circulation to the kidney may contribute to tissue repair. The regenerative potential of stem cells could be exploited by administration of ex vivo expanded stem cell populations or by the development of techniques to expand and differentiate local stem cells.

[Ion pair HPLC determination of p-aminobenzoic acid as an impurity in procaine and procainamide hydrochlorides]

A simple, specific and sensitive high-performance liquid chromatographic method for the determination of p-amino benzoic acid (PABA) as impurity in procaine and procainamide hydrochlorides has been developed. The compounds were chromatographed on reversed phase C-18 using water-methanol-acetonitrile solvent system containing sodium lauryl sulphate ion-pair reagent.