Starting young? Children's experiences of trying smoking during pre-adolescence.

Although the risks smoking poses to health are now well known, many young people continue to take up the habit. While numerous cross-sectional studies of adolescents have identified correlates of smoking initiation, much less prospective, longitudinal research has been conducted with young children to gather their accounts of early experiences of smoking, and this study fills that significant gap. Quantitative and qualitative data, collected using questionnaires, interviews and focus groups, are presented from the pre-adolescent phase of the Liverpool Longitudinal Study of Smoking. By age 11, 27% of the cohort had tried smoking, 13% had smoked repeatedly and 3% were smoking regularly. Rates of experimentation increased over time. Qualitative data revealed that curiosity and the role of peers were central to children's accounts of early smoking. By pre-adolescence, children are at different stages in their smoking careers, therefore interventions must be targeted to their varied experiences. Current prevention strategies often focus on restricting access to cigarettes, but a broad range of intervention measures is required which take account of the multifactorial nature of smoking onset. To be effective, policies that aim to prevent smoking must be grounded in children's lived experiences.

Utility and limitations of near-infrared spectroscopy during cardiopulmonary bypass in a piglet model.

Near-infrared spectroscopy assessment of cytochrome oxygenation could be a valuable technique to monitor cerebral intraneuronal oxygen delivery during cardiopulmonary bypass. However, the validity of the cytochrome signal has been questioned as it could easily be overwhelmed by the Hb signal. Five- to six-week-old control piglets (n = 5) underwent cardiopulmonary bypass at 37 degrees C. Study animals (n = 10) received 100 mg/kg of sodium cyanide to uncouple cytochrome from HB: Hematocrit was then decreased in steps of 5% from 35 to 5% with crystalloid hemodilution. In study piglets, the initiation of cardiopulmonary bypass was associated with oxygenated Hb increasing from 0 to 62.9 +/- 25.6 microM times the differential path-length factor, and oxidized cytochrome a,a3 increasing to 1.9 +/- 1.8 microM times the differential path-length factor. Cyanide caused oxygenated Hb to increase further to 132.3 +/- 48.9 microM times the differential path-length factor, and oxidized cytochrome c decreased to -7.0 +/- 2.6 microM times the differential path-length factor as anticipated, confirming uncoupling of electron transport. However, hemodilution subsequently resulted in linear decreases in oxidized cytochrome a,a3 (F = 8.57, p < 0.001) suggesting important cross-talk between the Hb and cytochrome signals as cytochrome is only intracellular. In control piglets, tissue oxygenation index showed a positive correlation with pump flow (r = 0.986, p = 0.013). The cytochrome signal as presently measured by near-infrared spectroscopy is highly dependent on hematocrit.