An evaluation of home volume ventilators that support open-circuit mouthpiece ventilation

BACKGROUND: Open-circuit mouthpiece ventilation (MPV) is a form of noninvasive ventilation that can be used to provide portable daytime ventilatory support for neuromuscular patients with chronic respiratory failure. MPV has been reported to reduce the risk of respiratory infection due to tracheostomy, and to improve cough and voice function and patient quality of life. Despite these potential benefits, mouthpiece ventilation is not widely used. This may be due in part to the fact that little information is available as to which ventilators can support this application. OBJECTIVE: To determine which volume-cycled portable home ventilators currently available in the United States will support MPV, and what peak inspiratory flow rates create adequate circuit pressure to prevent low-pressure alarming. METHODS: We used a commercially available MPV breathing circuit with a set tidal volume range of 500\N1,000 mL with each of 8 ventilators currently available in the United States. RESULTS: Six of the 8 ventilators supported MPV: Respironics Lifecare PLV-100 and PLV Continuum, Mallinckrodt Achieva PSO2, Pulmonetics LTV800, Newport HT50, and Uni-Vent Eagle 754.     

Low-dose leptin reverses skeletal muscle, autonomic, and neuroendocrine adaptations to maintenance of reduced weight

Maintenance of a reduced body weight is accompanied by decreased energy expenditure that is due largely to increased skeletal muscle work efficiency. In addition, decreased sympathetic nervous system tone and circulating concentrations of leptin, thyroxine, and triiodothyronine act coordinately to favor weight regain. These "weight-reduced" phenotypes are similar to those of leptin-deficient humans and rodents. We examined metabolic, autonomic, and neuroendocrine phenotypes in 10 inpatient subjects (5 males, 5 females [3 never-obese, 7 obese]) under 3 sets of experimental conditions: (a) maintaining usual weight by ingesting a liquid formula diet; (b) maintaining a 10% reduced weight by ingesting a liquid formula diet; and (c) receiving twice-daily subcutaneous doses of leptin sufficient to restore 8 am circulating leptin concentrations to pre-weight-loss levels and remaining on the same liquid formula diet required to maintain a 10% reduced weight. During leptin administration, energy expenditure, skeletal muscle work efficiency, sympathetic nervous system tone, and circulating concentrations of thyroxine and triiodothyronine returned to pre-weight-loss levels. These responses suggest that the weight-reduced state may be regarded as a condition of relative leptin insufficiency. Prevention of weight regain might be achievable by strategies relevant to reversing this leptin-insufficient state.     

PREVENTION OF CELL-TO-CELL SPREAD OF HERPES SIMPLEX VIRUS BY LEUKOCYTES

Antibody to herpes simplex virus (HSV) plus complement destroyed HSV-infected cells but did not stop the spread of the infection. Studies on the relationship between the time of appearance of viral antigens on the cell surface, immunological destruction of the cells by antiviral antibody and complement, and transfer of the virus to adjacent cells showed that the virus spread from infected to uninfected cells before the infected cells were susceptible to immunological destruction. Incubation of infected monolayers with leukocytes, however, stopped the spread of the virus by nonspecifically damaging both infected and uninfected cells and by presumably breaking intercellular bridges. When leukocytes were removed from infected monolayers, viral plaques developed. If, however, antiviral antibody and complement were added to monolayers before the leukocytes were removed, the development of plaques was prevented. These findings suggest that both antibody and leukocytes are needed to cure HSV infections.     

A critical period in the development of tectal neurons in the chick, as revealed by early enucleation

To further study the existence of a critical trophic period in the development of the chick optic tectum¹⁷, during which the presence of retinal synapses is essential to the continued growth of tectal neurons, we have unilaterally enucleated embryos between stages 14–20 and allowed survival until stages 35–43. If the critical trophic period is between stages 40–44, as previously reported¹⁷, then we reasoned that early removal of the eye might not have any effect on tectal development until the critical period. We assessed tectal neuron survival by staining for degeneration in the efferent projections of tectal neurons. In early enucleates, degeneration was present from stages 37–43, and the severity of the degeneration was much reduced in comparison to animals enucleated during the critical period.These findings substantiate the proposition that there is a critical period late in chick tectal development. However, because the degeneration in tectal projections is less intense than in animals enucleated during the critical period, we suggest that the early enucleation has permitted axons from the remaining eye to be routed to the deafferented tectum, where they may help to sustain a portion of the tectal neurons through the critical period. Moreover, the somewhat earlier appearance of degeneration in tectal efferent pathways of early enucleates suggests that a subtle trophic relationship between retina and tectum may exist prior to stage 40, even though this relationship is not revealed when enucleations are performed later, as between stages 35–40 (ref. 17).     

Pseudoreduction of intussusception: Is ileal reflux the end point?

Two cases of unsuccessful hydrostatic reduction of intussusception are reported. Both were associated with barium filling multiple loops of distal ileum, despite lack of complete reduction of the intussusception. The presence of free ileal reflux does not guarantee successful reduction. Careful examination of the cecum for residual intussus-ceptum and of non-contrast-filled small-bowel loops for evidence of remaining small-bowel obstruction is essential to recognize unsuccessful reduction.     

Activation of hepatic guanylate cyclase by nitrosyl-heme complexes: Comparison of unpurified and partially purified enzyme

The objective of this study was to evaluate the effects of several agents on activation of both unpurified and partially purified hepatic soluble guanylate cyclase by performed NO (nitric oxide or nitrosyl)-heme complexes. Guanylate cyclase was activated by NO complexes of the heme compounds, hematin, hemoglobin, myoglobin, catalase and cytochrome c, and also by the reaction product of NO and ferredoxin, a non-heme, iron sulfur electron transfer protein. NO-lipoxygenase, which contains non-heme iron, did not activate guanylate cyclase. NO-heme complexes activated unpurified enzyme almost equally well in the presence of either Mg²⁺ or Mn²⁺. However, activation of purified (350- to 750-fold) guanylate cyclase was markedly greater with Mg²⁺ than with Mn²⁺. At concentrations that did not alter basal enzymatic activity, Ca²⁺ markedly inhibited guanylate cyclase activation in the presence of Mg²⁺ but not of Mn²⁺. Hemoproteins inhibited activation of unpurified and purified enzyme by NO-heme complexes, and increasing the concentrations of the latter overcame the inhibition. Gel filtration studies indicated that uncomplexed and NO-complexed hematin bind to common or adjacent sites on guanylate cyclase. Whereas dl-dithiothreitol enhanced activation, ferricyanide, cystine, o-iodosobenzoic acid and ethacrynic acid inhibited activation of guanylate cyclase by NO-heme complexes. The data indicate that the effects of these diverse agents on guanylate cyclase activation by preformed NO-heme are similar to their effects on enzyme activation by NO and nitroso compounds, both of which readily form NO-heme complexes. Therefore, the effects of these diverse agents may be on guanylate cyclase rather than on NO-heme formation.     

A computer-assisted image-processing system for the analysis of autoradiographs of cerebral metabolic activity

A computerized image-processing system has been developed for quantitative analyses of the autoradiographs obtained with the [¹⁴C]deoxyglucose method. By means of this system, these cerebral metabolic images can be digitized and the resultant data can be manipulated for image construction, enhancement, enlargement, and microdensitometric analysis. It is also possible to generate quantitative color-coded metabolic maps that display the distribution of the actual rates of local glucose utilization throughout the entire central nervous system with a resolution conservatively estimated to be equivalent to that of a full-width-half-maximum of approximately 100 μm.     

Systemic-pulmonary arteriovenous fistula of traumatic origin: A case report

Arteriovenous fistulas between the systemic circulation and the pulmonary artery are extremely rare. Continuous precordial murmur is the usual clinical sign while unilateral rib notching may be the only radiologic manifestation of this condition. Selective angiographic investigation is necessary to localize the site of such an arteriovenous (AV) fistula before surgery is performed. In a review of the literature of 15 published cases, the majority were of congenital origin, with four of these systemic-pulmonary AV fistulas of traumatic origin, of which one occurred after insertion of an intercostal catheter. We describe one case of traumatic origin 9 years after percutaneous thoracic drainage for spontaneous pneumothorax, in which transcatheter embolic occlusion of the feeding arteries of an AV fistula was attempted. The advantages and the disadvantages of the nonsurgical and surgical therapeutic approaches are discussed.