Congestion Factor Research Articles

Acoustic rhinometry findings in patients with mild sleep apnea.

Nasal obstruction may contribute to the development of obstructive sleep apnea (OSA). Acoustic rhinometry (AR) measures nasal patency and congestion, which are useful parameters in objectively evaluating nasal obstruction. The nasal obstruction produced by allergic rhinitis may contribute to the development of OSA and can be easily assessed with AR. This study was undertaken to assess the degree of nasal obstruction seen in allergic patients with and without OSA. This study was a retrospective data analysis from a tertiary referral center. The AR data from 10 patients with and 40 patients without mild OSA were compared. The mean congestion factors at the first cross-sectional area (CSA1) on the AR graph were found to be significantly higher in the OSA group than in the non-OSA group (P = 0.03). The classification of change in congestion factors demonstrated significant differences at CSA1, CSA2, and CSA3 and in volume (t distributions <0.001, 0.0312, <0.001, and <0.001, respectively). The non-OSA patients noted a significant subjective improvement in nasal congestion after topical nasal decongestion, whereas the OSA patients did not (P <or= 0.0001 and 0.064, respectively). Although the role of nasal obstruction in OSA is controversial, our study lends evidence to the thought that the nasal obstruction associated with allergic rhinitis is associated with the presence of mild OSA. Whether allergic rhinitis is a direct cause of OSA is debatable, but we have shown that greater nasal congestion is related to the presence of OSA in a population of patients with allergic rhinitis.

An interpretation method for objective assessment of nasal congestion with acoustic rhinometry.

Acoustic rhinometry is a relatively new modality for evaluating the status of the nose. It assesses the geometry of the nasal cavity by analyzing reflected sound waves. Despite its expanding use, there is no established interpretation method. Our aims in the present descriptive study were to develop and test a protocol as a possible method to read these graphs for clinical use. We formulated a reading protocol to grade the congestion state of the nasal cavity. The percentile difference of cross-sectional area and volume values between the baseline and decongested states were classified into five categories based on normative values. Fifty-six patients with allergic rhinitis were used. All the acoustic rhinometry readings were performed in blinded fashion according to the protocol; later, the clinical information was paired with the interpretation of the graph. The mean percentile differences of baseline and decongestion values in patients with allergic rhinitis were in the mild to moderate range difference according to our reading system. The range of nasal congestion in patients with allergic rhinitis patients was increased with additional pathological conditions such as sleep apnea. The percentile difference between the baseline values and values for maximally decongested state reflect mucosal congestion as a "congestion factor," which can be graded as mild, moderate, severe, or markedly severe, for objective evaluation of nasal congestion.

Evaluating a Roadside Assistance Program: Penn-Lincoln Parkway Service Patrol

The results of a preliminary evaluation of the Penn-Lincoln Parkway Service Patrol are summarized. The Pennsylvania Department of Transportation contracts with a local towing company to operate the Service Patrol on the Penn-Lincoln Parkway (PA Route 60, U. S. Route 22, and Interstates 279 and 376) in the Pittsburgh metropolitan area. The Service Patrol, consisting of specially equipped tow trucks driven by specially trained drivers, provides assistance to disabled vehicles along the parkway, thus reducing traffic delays and congestion. Service patrol hours of operation are during the morning and afternoon peak travel hours. The length of highway included in the evaluation is approximately 32 km (20 mi). The evaluation compared data from the period January–April 1997 with incident data collected by the Pennsylvania State Police during the corresponding period in 1996. The data were analyzed to determine the effect of the Service Patrol on incident response times, incident clearance times, and incident-related congestion factors (i.e., vehicle-hours of delay, fuel consumption, and vehicle emissions). This evaluation yielded the following results: ( a) the Service Patrol reduced incident response times by approximately 8.7 min; ( b) the Service Patrol cleared incidents approximately 8.3 min faster than before implementation; ( c) the Service Patrol reduced hours of delay by approximately 547,000 h per year; ( d) total monetary savings resulting from implementation of the Service Patrol are approximately $6.5 million per year; and ( e) the public response to the Service Patrol is overwhelmingly favorable.

Optimal road-pricing: Simultaneous treatment of time losses, increased fuel consumption, and emissions

In this paper, optimal road-charges are derived with respect to congestion, emissions, and the corresponding excessive fuel consumption and emissions due to the congestion. It is shown that a road-user should then pay a charge corresponding not only to its own emissions, but also to the increased emission and fuel consumption of other road-users. It is demonstrated in a numerical example that these ‘system effects’ may be significant. Furthermore, a new flexible speed-flow relationship is introduced which incorporates the linear speed-flow relationship as well as the linear speed-density relationship (for different parameter values). The optimal pure congestion charge is then expressed solely by the equivalent congestion factor, the average vale of time, the actual speed, and the speed at which the maximum flow occurs.

Disamenity Influences of Edge Cities on Exurban Land Values: A Theory with Empirical Evidence and Policy Implications

A theory is posed with some empirical support on how the American exurban land market behaves near edge cities. The exurban land market exists beyond the built-up urban area within commuting range of urban employment and service opportunities. It responds differently to proximity to downtown, edge cities and the boundary of urban development. Three relationships between the value of exurban land and these landscape features are theorised and empirically supported. First, as exurban households are dependent upon dispersed employment opportunities and rely on the urban area for many services, the value of residential land falls with respect to distance from the boundary of urban development. Secondly, since exurban households view edge cities as sources of congestion, pollution, noise and other factors associated with perceived ills of suburbia, the value of exurban land rises with respect to distance from edge cities. Thirdly, since downtowns are the dominant centre of reference for many metropolitan regions, exurban land values fall with respect to distance from downtowns. Taken together, exurban land values fall with respect to distance from the boundary of urban development but, because of the disamenity influences of edge cities, at a flatter slope than suggested by monocentric land value theory. The effect of edge cities may be to push the urban field farther out than would be expected without this influence.

Analysis of Channel Utilization in Traffic Concentrators

The behavior of line concentrators in a data communication system has been analyzed for different channel allocation strategies. The users (terminals) are divided into classes according to their transmission rate requirements. The different bit rate classes (BRC) can be separated by dividing the network into subnets or, alternatively, they can share one concentrator which forms outgoing channels from a common quantity of channels of a basic speed, or by splitting a high speed channel into two or more channels with lower transmission rate. The equations of state and analytical expressions for the time congestion factors have been developed for the different system models. The numerical results show that a joint concentrator arrangement requires less channel capacity than a separated concentrator system for a fixed value of the congestion probability. The results of this investigation may serve as background material for planning future data networks.