American journal of respiratory and critical care medicine
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We set out to determine tuberculosis incidence and risk factors in the homeless population in San Francisco. We also examined the transmission of tuberculosis by molecular methods. We followed a cohort of 2,774 of the homeless first seen between 1990 and 1994. ⋯ The high rate of tuberculosis in the homeless was due to recent transmission in those HIV-positive and nonwhite. African Americans and other nonwhites may be at high risk for infection or rapid progression. Control measures in the homeless should include directly observed therapy and incentive approaches, treatment of latent tuberculous infection in those HIV-seropositive, and screening in hotels and shelters.
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Am. J. Respir. Crit. Care Med. · Aug 2000
Right ventricular function in respiratory distress syndrome and subsequent partial liquid ventilation. Homeometric autoregulation in the right ventricle of the newborn animal.
Infant respiratory distress syndrome (IRDS) and subsequent partial liquid ventilation (PLV) cause increased pulmonary vascular resistance, thus raising afterload. In nine newborn lambs the effects of IRDS and subsequent PLV on right (RV) and left ventricular (LV) contractility and systolic pump function were assessed using indices derived from RV and LV pressure-volume relations, obtained by micromanometric and conductance catheters during transient inferior vena cava occlusion. Pulmonary function deteriorated during IRDS with a significant decrease in the ratio of arterial oxygen pressure to fraction of inspired oxygen (Pa(O(2))/FI(O(2))) whereas pulmonary artery pressure (Ppa) showed a significant increase and pulmonary vascular resistance showed a substantial though not significant increase. ⋯ LV pump function and contractility were unchanged. During PLV pulmonary function showed a recovery but Ppa and pulmonary vascular resistance remained high; indices for RV contractility showed a sustained significant increase compared with baseline conditions whereas indices for LV pump function and contractility remained unchanged. These results show that the right ventricle of the newborn heart, in the face of increased pulmonary vascular resistance, is able to maintain cardiac output through homeometric autoregulation.
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Am. J. Respir. Crit. Care Med. · Aug 2000
Sleep architecture and respiratory disturbances in children with obstructive sleep apnea.
Little is known regarding sleep architecture in children with the obstructive sleep apnea syndrome (OSAS). We hypothesized that sleep architecture was normal, and that apnea increased over the course of the night, in children with OSAS. We analyzed polysomnographic studies from 20 children with OSAS and 10 control subjects. ⋯ OSAS is predominantly a REM phenomenon in children. Obstructive apnea worsens over the course of the night, independent of the changing amounts of REM sleep. We speculate that this increase in apnea severity may be secondary to upper airway muscle fatigue, changes in upper airway neuromotor control, or changes in REM density.
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Am. J. Respir. Crit. Care Med. · Aug 2000
Evaluating the role of inducible nitric oxide synthase using a novel and selective inducible nitric oxide synthase inhibitor in septic lung injury produced by cecal ligation and puncture.
We studied the role of inducible nitric oxide synthase (iNOS) in septic lung injury using a novel and selective iNOS inhibitor (a fused piperidine derivative; ONO-1714) following a cecal ligation and puncture (CLP) procedure. All rats that received CLP died within 48 h after the intervention. The subcutaneous injection of ONO-1714 at 0.03 mg/kg every 12 h resulted in a significantly longer survival time than the saline control only when administration was started 12 h after the CLP procedure. ⋯ Since the iNOS mRNA expression in lung homogenates continued to elevate until 42 h, the decrease in iNOS activity and protein expression later than 24 h after the CLP was thus considered to be due to some posttranscriptional mechanism during the late phase of sepsis. In conclusion, intervention with a potent and selective iNOS inhibitor seemed to improve survival in CLP rats when used at the appropriate doses and time points. However, the self-limited mechanism of iNOS regulation in the lungs may also indicate that iNOS plays only a limited role in sepsis and septic shock.
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Am. J. Respir. Crit. Care Med. · Jul 2000
Comparative StudyBiologically variable or naturally noisy mechanical ventilation recruits atelectatic lung.
Biologically variable mechanical ventilation (Vbv)-using a computer-controller to mimic the normal variability in spontaneous breathing-improves gas exchange in a model of severe lung injury (Lefevre, G. R., S. E. ⋯ The respiratory rate variability programmed for Vbv demonstrated an inverse power law frequency distribution ( y approximately 1/f(a)) with a = 1.6 +/- 0.3. These findings provide strong support for the theoretical model of noisy end-inspiratory pressure better recruiting atelectatic lung. Our results suggest that using natural biologically variable noise has enhanced the performance of a mechanical ventilator in control mode.