Influence of face mask design on bag-valve-mask ventilation performance: a randomized simulation study.

BACKGROUND: Different face mask designs can influence bag-valve-mask (BVM) ventilation performance during resuscitation. We compared a single-use, air-cushioned face mask (AM) with a reusable silicone face mask (SM) for quality of BVM ventilation on a manikin simulating cardiac arrest. METHODS: Thirty-two physicians were recruited, and a prospective, randomized, crossover observational study was conducted after an American Heart Association-accredited basic life support provider course and standardized practice time were completed. Participants performed 12 cycles of BVM ventilation with both the AM and SM on a SmartMan lung simulator. RESULTS: Mean tidal volume was significantly higher in ventilations performed using the AM vs. the SM (548 ± 159 ml vs. 439 ± 163 ml, P < 0.01). In addition, the proportion of low-volume ventilation was significantly lower with the AM than the SM [6/12 (2-11) vs. 9/12 (5-12), P = 0.03]. Bag-valve-AM ventilation volume was not affected by the physical characteristics of the rescuers, except for sex. In contrast, bag-valve-SM ventilation volume was affected by most of the characteristics tested, including sex, height, weight, hand width, hand length, and grip power. CONCLUSION: The AM seems to be a more efficient face mask than the SM at delivering sufficient ventilation volumes. The performance of the AM did not seem to be associated with the physical characteristics of the rescuers, whereas that of the SM was affected by these factors. The SM may not be an appropriate face mask for performing one-person BVM ventilation during resuscitation for rescuers who are smaller in stature, have a smaller hand size, or have weaker grip power.

Sepiapterin reductase producing L-threo-dihydrobiopterin from Chlorobium tepidum.

A novel type of NADPH-dependent sepiapterin reductase, which catalysed uniquely the reduction of sepiapterin to l-threo-dihydrobiopterin, was purified 533-fold from the cytosolic fraction of Chlorobium tepidum, with an overall yield of 3%. The native enzyme had a molecular mass of 55 kDa and SDS/PAGE revealed that the enzyme consists of two subunits with a molecular mass of 26 kDa. The enzyme was optimally active at pH8.8 and 50 degrees C. Apparent Km values for sepiapterin and NADPH were 21 and 6.2 microM, respectively, and the kcat value was 5.0 s-1. Diacetyl could also serve as a substrate, with a Km of 4.0 mM. The inhibitory effects of N-acetylserotonin, N-acetyldopamine and melatonin were very weak. The Ki value of N-acetyldopamine was measured as 400 microM. The N-terminal amino acid sequence was revealed as Met-Lys-His-Ile-Leu-Leu-Ile-Thr-Gly-Ala-Xaa-Lys - Lys - Ile - Xaa - Arg - Ala - Ile - Ala - Leu - Glu - Xaa - Ala - Arg - Xaa-Xaa-Xaa-His-His-His-, which shared relatively high sequence similarity with other sepiapterin reductases.

Tepidopterin, 1-O-(L-threo-biopterin-2'-yl)-beta-N-acetylglucosamine from Chlorobium tepidum.

A novel pterin compound, designated as tepidopterin, was detected from a thermophilic photosynthetic green sulphur bacterium, Chlorobium tepidum. The amount of tepidopterin inside the cell was estimated to be 2-5 micromol g(-1) dry weight of cell. This compound was purified through a high performance liquid chromatography using preparative DeltaPak C18 column. This compound was characterized by chromatographic behavior and by absorption and fluorescence properties. Its structure was determined to be 1-O-(L-threo-biopterin-2'-yl)-beta-N-acetylglucosamine by 1D- and 2D-NMR spectroscopy, mass spectrometry and CD. The relative amount of tetrahydrotepidopterin was estimated to be 96.7% inside the cell, that of dihydrotepidopterin 2.9%, and that of fully oxidized tepidopterin 0.4%. The amount of tepidopterin within the cell increased continuously until the beginning of the stationary phase of the cell growth.