American journal of respiratory and critical care medicine
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Gas and tar phases of commercially available filter cigarettes were tested for ferritin-iron-releasing effects and polyunsaturated-fatty-acid oxidant capacity in vitro. A vacuum pump-dependent apparatus with Cambridge filters was used to separate gas and tar; the former was directly smoked into reaction mixtures, while the latter was extracted from Cambridge filters in aqueous medium and freshly used at 40 to 80% final concentrations. Both phases induced ferritin iron release, which was not antagonized by superoxide dismutase (SOD). ⋯ In the absence of ferritin, gas-induced lipid peroxidation was very low, and tar extracts were apparently ineffective. Thus, the intrinsic lipoperoxidative capacity of cigarette smoke is low and is due to gas; however, when smoke interacts with ferritin, a marked iron-driven peroxidation becomes manifest essentially with gas, tar components acting as antioxidants. The present data suggest that cigarette-smoke-mediated iron mobilization from ferritin may represent a specific prooxidant mechanism related to cigarette smoking in vivo.
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Am. J. Respir. Crit. Care Med. · Jan 1995
Comparative StudyPatient-ventilator interaction during synchronized intermittent mandatory ventilation. Effects of flow triggering.
Synchronized intermittent mandatory ventilation (SIMV) intermixes assisted and spontaneous breaths. Its ability as a weaning technique has been questioned on the basis that patients show little adaptation to ventilator assistance. We studied inspiratory effort and patient-ventilator interaction at different levels (SIMV, 100, 50, and 0%) of flow-triggered SIMV versus pressure-triggered SIMV in patients during the weaning period. ⋯ During pressure-triggered SIMV PTP/b and PTP/min were identical for mandatory and spontaneous breaths, whereas during flow-triggered SIMV PTP/b and PTP/min were significantly lower for mandatory than for spontaneous breaths. This difference was greatest when flow triggering and constant pressure ventilation were associated. These data show that flow triggering reduces inspiratory effort during both mandatory and spontaneous SIMV breaths and obtains a better patient-ventilator interaction.