Smoking during pregnancy: postnatal effects on arousal and attentional brain systems.

Prenatal exposure to cigarette smoke is known to produce lasting arousal, attentional and cognitive deficits in humans. The pedunculopontine nucleus (PPN), as the cholinergic arm of the reticular activating system (RAS), is known to modulate arousal, waking and REM sleep. Rapid eye movement (REM) sleep decreases between 10 and 30 days postnatally in the rat, with the greatest decrease occurring at 12-21 days. Pregnant dams were exposed to 150 ml of cigarette smoke for 15 min, three times per day, from day E14 until parturition, and the pups allowed to mature. We analyzed (a) intrinsic membrane properties of PPN neurons in slices from pups aged 12-21 days, and (b) the sleep state-dependent P13 auditory evoked potential, which is generated by PPN outputs, in animals allowed to age to adolescence. We found significant changes in the intrinsic membrane properties of PPN cells in prenatally exposed animals compared to intact ones, rendering these cells more excitable. In addition, we found disturbances in the habituation to repetitive stimulation in adolescent, freely moving animals, suggestive of a deficit in the process of sensory gating. These findings could explain some of the differences seen in individuals whose parents smoked during pregnancy, especially in terms of their hypervigilance and increased propensity for attentional deficits and cognitive/behavioral disorders.

Prenatal exposure to cigarette smoke affects the physiology of pedunculopontine nucleus (PPN) neurons in development.

Prenatal exposure to cigarette smoke is known to produce lasting arousal, attentional and cognitive deficits in humans. The pedunculopontine nucleus (PPN), as the cholinergic arm of the reticular activating system (RAS), is known to modulate arousal, waking and rapid eye movement (REM) sleep. REM sleep decreases between 10 and 30 days postnatally in the rat, especially at 12-21 days. Pregnant dams were exposed to 350 ml of cigarette smoke for 15 min, 3 times per day, from day E14 until birth, and the pups allowed to mature. Intracellularly recorded PPN neurons in 12-21 day rat brainstem slices were tested for intrinsic membrane properties, including the hyperpolarization-activated cation current Ih, which is known to drive oscillatory activity. Type II (A-current) PPN cells from 12-16 day old offspring of treated animals had a 1/2max Ih amplitude of (mean +/- SE) 4.1 +/- 0.9 mV, while 17-21 day cells had a higher 1/2max Ih of 9.9 +/- 1.1 mV (p < 0.0001). Cells from 12-16 day old control brainstems had a 1/2max Ih of 1.3 +/- 0.1 mV, which was lower (p < 0.05) than in cells from prenatally treated offspring; while 17-21 day old cells from controls had a 1/2max Ih of 3.3 +/- 0.3 mV, which was also lower (p < 0.01) than in cells from prenatally treated offspring. In addition, changes in resting membrane potential [control -65. +/- 0.9 mV (n=32); exposed -55.0 +/- 1.4 mV (n = 27) (p < 0.0001)], and action potential (AP) threshold [control -56.5 +/- 0.7 mV (n = 32), exposed -47.0 +/- 1.4 mV (n = 27) (p < 0.0001)], suggest that prenatal exposure to cigarette smoke induced marked changes in cells in the cholinergic arm of the RAS, rendering them more excitable. Such data could partially explain the differences seen in individuals whose parents smoked during pregnancy, especially in terms of their hypervigilance and increased propensity for attentional deficits and cognitive/behavioral disorders.

Temporal changes in rates and reasons for medical induction of term labor, 1980-1996.

OBJECTIVE: This study was undertaken to assess temporal changes in rates and reasons for medical induction of term labor. STUDY DESIGN: A retrospective medical record review was conducted on a population-based cohort of 1293 women with term deliveries. RESULTS: The rate of medical labor induction increased from 12.9% in 1980 to 25.8% in 1995. Stated indications also changed, with a 2-fold increase in induction for postdate gestation, a 23-fold increase in induction for macrosomia, a 15-fold increase in elective induction, and a 22-fold decline in induction for premature rupture of membranes. The average gestational age at delivery of postdate pregnancies declined from 41.9 weeks in 1980 to 41.0 weeks in 1995. By 1995, the average maternal length of stay and the percentage of cesarean deliveries were higher among women with induced labor at term than among those with spontaneous labor at term. CONCLUSION: Induction of term labor has almost doubled in prevalence during the past 15 years. The most common indications are elective induction and postdate pregnancy, often applied to gestations of 40 to 41 weeks' duration.

Development of a giant bulla after lung volume reduction surgery.

Lung volume reduction surgery (LVRS) is being evaluated in the treatment of emphysema. The proposed mechanisms of improvement are increased elastic recoil of the lung and improved mechanical efficiency of the muscles of respiration. We report a unique patient with emphysema who developed a giant bulla 3 years subsequent to LVRS. The patient underwent extensive evaluation, including measurements of lung mechanics. Bullectomy was performed, but it was unsuccessful. Although the mechanisms behind the development of giant bullous disease remain speculative, heterogeneous improvement in elastic recoil following LVRS may be one of the responsible mechanisms.

Development of pulmonary hypertension after lung volume reduction surgery.

This prospective, longitudinal study was designed to assess the hemodynamic changes occurring in patients who undergo lung volume reduction surgery (LVRS). Patients with emphysema treated with LVRS underwent hemodynamic evaluation before and after surgery. The study group consisted of nine patients with an average age of 64.4 yr. FEV1 rose significantly from 0.64 preoperatively to 0.99 L postoperatively. After surgery, pulmonary artery (PA) systolic pressure rose to 47.9 +/- 12.4 mm Hg, meeting criteria for development of pulmonary hypertension. In six patients, the elevation in PA pressure was attributed to an increase in the pulmonary vascular resistance, but for all nine patients the change was not statistically significant. The pulmonary artery occulsion pressure (PAOP) did not change postoperatively. There was no correlation of PAOP with global left ventricular ejection fraction. While preoperatively there was a negative correlation between symptoms (Mahler dyspnea index) and PA pressure, after surgery the change in PA pressures did not correlate with the change in symptoms (Mahler transitional dyspnea index). We concluded that development of pulmonary hypertension may occur after LVRS in patients whose symptomatic status improves and in whom this condition was not present preoperatively.

Changes in pulmonary mechanics after lung volume reduction surgery.

Lung volume reduction surgery (LVRS) is a promising new treatment for emphysema and leads to increased flow rates. We investigated the mechanisms by which flow rates could increase and the correlates of lessened dyspnea in patients undergoing LVRS before and 3 months after LVRS in patients with severe emphysema. The following were done: routine pulmonary function testing, measurements of elastic recoil (Pel), tidal breathing patterns, inspiratory work of breathing (Winsp), construction of static recoil-maximum flow curves, and measurement of baseline and transitional dyspnea index (TDI). There were increases in forced vital capacity (FVC: 2.24 +/- 0.71 to 2.92 +/- 0.63 liters; p < 0.05), forced expired volume in 1 (FEV1: 0.64 +/- .16 to 1.03 +/- 0.28 liters; p < 0.01), and decreases in all divisions of lung volume, e.g. total lung capacity (TLC: 6.86 +/- 1.41 to 5.96 +/- 1.49 liters; p < 0.01). Maximum Pel increased (11.7 +/- 3.7 to 19.8 +/- 7.8 cmH2O; p < 0.02) as did the coefficient of retraction (CR = Pel/TLC: 1.8 +/- 0.7 to 3.6 +/- 3.6 +/- 2.2 cmH2O/liter). However, the individual responses in other parameters were markedly different among patients. There was no consistent trend in changes in the slope or position of the static recoil-maximum flow curve or Winsp. The only positive correlate of improved dyspnea (TDI = 3.22 +/- 2.22; p < 0.01) was improvement in CR, FEV1 being a weak negative correlate and change in lung volume not being a correlate at all. We conclude that there is a heterogeneous response of the airways to LVRS. Increased elastic recoil was the primary determinant of improved flow rates after LVRS and is the only positive correlate for improvement in dyspnea.