Bilateral vagotomy differentially alters the magnitude of hypoglossal and phrenic long-term facilitation in anesthetized mechanically ventilated rats.

Acute intermittent hypoxia elicits long-term increases in respiratory motor output (long-term facilitation, LTF). Most investigators study LTF in mechanically ventilated, bilaterally vagotomized, and anesthetized animals. Vagotomy blocks inhibitory lung-volume feedback that could diminish the magnitude of LTF. However, the effects of vagotomy on LTF may not be so straight forward. In cats, vagotomy increases LTF of upper airway muscles but may decrease LTF of accessory pump muscles. The effects of vagotomy on LTF in rats are unknown. We hypothesized that the magnitude of hypoglossal and phrenic LTF would be differentially regulated by vagal afferent feedback in anesthetized and mechanically ventilated rats. Hypoglossal and phrenic motor outputs were recorded from vagotomized and vagally intact anesthetized mechanically ventilated adult Sprague-Dawley rats before, during, and up to 60-min after intermittent hypoxia. Ventilator frequency (f), pump volume, and peak tracheal pressure were not different between groups. The effects of vagotomy on the magnitude of LTF depended on the motoneuron population in question. The magnitude of hypoglossal LTF increased after vagotomy (vagi intact, -5+/-10%; vagotomy, 66+/-11% above baseline; p<0.05); whereas, the magnitude of phrenic LTF decreased after vagotomy (vagi intact, 135+/-24%; vagotomy, 40+/-13% above baseline; p<0.05). These data support previous work in anesthetized cats, and suggest that the expression of hypoglossal and phrenic respiratory motor plasticity is differentially regulated by vagal afferent feedback.

Cigarette smoking and the desire to quit among individuals living with HIV.

Among individuals living with human immunodeficiency virus (HIV), studies have found that smokers are at greater risk than nonsmokers to develop bacterial pneumonia, oral lesions and acquired immune deficiency syndrome (AIDS) dementia complex. Information is lacking regarding the prevalence of cigarette smoking among people living with HIV or about their intentions to quit smoking. A survey was conducted with a sample of patients attending an HIV outpatient clinic at San Francisco General Hospital to assess the prevalence of cigarette smoking and the level of interest in quitting. In total, 228 assessments were completed. Study results revealed a high percentage of smokers among our sample of individuals living with HIV compared to the percentage of smokers found in the general adult population. A total of 123 individuals (54%) reported that they smoked cigarettes. Men were more than twice as likely to have made previous attempts at smoking cessation than were woman. The majority of cigarette smokers (63%) reported that they were currently thinking about quitting. Respondents' preferences for types of smoking cessation methods are discussed, and recommendations are proposed for identifying and treating tobacco dependence in this population.