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Biomedical subjects

Ronald P Gruber

Publications and source records attributed to Ronald P Gruber.

9 recordsLinked to original sources
PubMed2005

Effects of caffeine on prospective duration judgements of various intervals depend on task difficulty.

The effects of caffeine on prospective duration judgements were investigated in two double-blind placebo-controlled experiments. After taking either 200 mg of caffeine or a placebo, participants performed a task that demanded considerable attention, driving a car in a simulator (Experiment 1) or a task that demanded relatively little attention, watching a videotaped scene from a driven car (Experiment 2). Each participant made duration judgements of three target intervals: 15 s, 60 s and 300 s. Actively driving participants in the caffeine condition judged it as shorter than did those in the placebo condition. Caffeine had no effect on duration judgements following passive viewing. When people must perform a relatively difficult task, caffeine causes participants to allocate relatively more of their attentional resources to the task and relatively less to duration timing. Although caffeine may increase the pacemaker rate of an internal clock (via dopamine D(1) agonism), when external events are attention-demanding, caffeine mainly influences the relative allocation of attention to external events or to time (via dopamine D(2) agonism) in cerebral areas subserving the executive control of attention.

Adult↗
PubMed2005

Changing the convexity and concavity of nasal cartilages and cartilage grafts with horizontal mattress sutures: part I. Experimental results.

Prior studies indicated that horizontal mattress sutures can control the curvature of a convex lateral crus. This study undertook to ascertain the ideal spacing for mattress sutures, determine what effect they have on the subsequent strength of the cartilage, and compare that to the resultant strength after scoring procedures used to control curvature. Curved fresh cadaver septa of various thicknesses (0.5, 1, and 1.5 mm) were used. The ideal spacing (gap between suture purchases) for the mattress suture was sought in 15 specimens. The consequent change in stiffness (modulus) of the cartilage was measured in nine other specimens before and after suture placement and after scoring. If the spacing was too large, instability resulted. If it was too small, curvature correction could not be obtained. An ideal mattress spacing (6 to 8 mm for 0.5-mm specimens and 8 to 10 mm for 1.5-mm specimens) removed most curvature and provided stability. The mattress suture increased the stiffness (modulus) above normal and far above that when the curvature was removed by scoring. The mean composite modulus before suturing was 4.6 MPa. After ideally spaced sutures, it was 6.2 MPa, a 35 percent increase in stiffness. After scoring to improve curvature, it was 2.4 MPa, a 48 percent reduction in stiffness (p = 0.02, Wilcoxon signed rank test). The horizontal mattress suture technique corrects cartilage curvature if the appropriate spacing is used. The corrected cartilage is stiffer/stronger than normal cartilage and much stiffer/stronger than if scored.

Cadaver↗
PubMed2005

Changing the convexity and concavity of nasal cartilages and cartilage grafts with horizontal mattress sutures: part II. Clinical results.

Horizontal mattress sutures have previously been shown to remove unwanted bulbosity and convexity of nasal tip cartilages. The purpose of this study was to extend that concept by investigating the universal applicability of the horizontal mattress suture to change and control the curvature (e.g., convexity or concavity) of a wide variety of nasal cartilages and warped cartilage grafts. The horizontal mattress suture was applied to a variety of clinical situations, including nasal tip bulbosity caused by convex lateral crura, collapsed external nasal valves, warped grafts and struts, crooked L-shaped septal struts, and collapsed internal nasal valves. Twenty-nine cases were studied over a period of 10 to 23 months. The horizontal mattress suture proved to be a simple, effective means of achieving satisfactory control of the curvature of various cartilages of the nose (including external valves, internal valves, and septum) and warped cartilage grafts. Curvature control was obtained in all cases where the cartilage was supple. Moreover, the resultant strength was increased above normal. Partial recurrence of the curvature was seen in only two cases. Clinical results indicated that the horizontal mattress suture is universally applicable to a variety of situations in which the curvature of nasal cartilage and cartilage grafts needs to be removed or modified. The mattress suture drastically reduces the need for scoring (with its inherent problems of weakness) and the need for cartilage grafting.

Cartilage↗
PubMed2003

Brow or forehead fixation with sutures only: a preliminary communication.

Fixation of the brow, although not technically difficult, can be a time-consuming process. Screws, whether permanent or absorbable, are occasionally associated with minor undesirable problems. We present a technique of brow suspension that is quick, simple, and free of the problems associated with fixation to the calvarium. It involves the use of sutures only. A heavy PDS suture is passed (with the aid of an awl) from the dermis of the brow or forehead that needs to be fixed to the dermis of a small incisional wound located 5-8 cm away. This suture suspension technique has proven to be quick and easy to execute. It has provided satisfactory fixation of the forehead/brow without problems of suture reaction. The cost of calvarial screws has been eliminated. When brow or forehead fixation is necessary, suspension with sutures to the dermis of a more superior location is an excellent method to accomplish the task quickly and easily. Long-term follow-up of a large series of patients will be necessary to validate the initial impression of this new technique.

Eyebrows↗
PubMed2003

Grafting the nasal dorsum with tandem ear cartilage.

A technique for autogenous grafting of the nasal dorsum with ear cartilage is suggested based on the results of 25 consecutive cases. The technique involves (1) harvesting the entire cymba conchae and cavum conchae of the ear; (2) separating them and suturing them to each other in tandem fashion; (3) filling the underside concavity of the cymba conchae part of the graft with scraps of cartilage; (4) avoiding any bruising or crushing of the graft; and (5) filling any minor residual irregularities of the dorsum with soft tissue or cartilage from the cephalic trim of the lateral crus. The results suggest a consistent augmentation of the nasal dorsum for deficiencies from 3 to 6 mm in size. Four of the 25 cases did require secondary correction for dorsal convexity, inadequate augmentation, and surface irregularities. The technique, however, has been helpful in that ear cartilage is invariably available, allowing septum to be used for more important grafts. The procedure is easily performed under local anesthesia with no significant distortion to the donor site.

Adult↗
PubMed2003

Effect of caffeine on prospective and retrospective duration judgements.

The effects of caffeine on prospective and retrospective duration judgements were evaluated in a double-blind placebo-controlled experiment. After taking either 200 mg caffeine or a placebo, participants touched a 17-sided polygon for 15 s. Then they verbally estimated the number of angles and the duration. Participants in the prospective group were told in advance they would be making a duration estimate, whereas those in the retrospective group were not told. Caffeine reduced duration estimates in the prospective condition but not in the retrospective condition. The effect of caffeine on very long duration comparisons (the past year compared with a year at one-half and one-quarter of one's age) was also evaluated, but none was found. The findings do not support the hypothesis that caffeine affects duration experience by increasing the internal clock rate as a result of its dopamine D(2) agonist properties. The hypothesis that caffeine produces its effect by enhancing memory was considered and rejected. The most parsimonious explanation is that caffeine increased arousal level, which led to a narrowing of the focus of attention to the most salient task.

Adolescent↗
PubMed2002

Surgical correction of the short nose.

The primary emphasis of the operation to achieve maximum nasal lengthening is based on: (l) a release of soft tissue including the mucoperichondrium; (2) release of the soft tissue between the upper lateral cartilage and the lower lateral cartilage; and (3) attachment of a batten graft to the septum to project the tip cartilages caudally. Case examples of the results of the open approach are given. In those cases in which the closed technique must be used, a modified technique is utilized. This involves a hemitransfixion incision and elevation of the mucoperichondrium bilaterally, followed by a batten graft.

Anesthesia, Local↗
PubMed2002

Suture algorithm for the broad or bulbous nasal tip.

The history and current status of suture techniques to correct a broad or bulbous nasal tip are reviewed. General principles for suture techniques to control tip shape are discussed; they include leaving an approximately 6-mm-wide lateral crus. The algorithm presented includes four sutures, all of which are not necessary in every case. These sutures include (1) the transdomal suture (to narrow the individual domes), (2) the interdomal suture (to provide symmetry and tip strength and sometimes to narrow the tip complex), (3) the lateral crural mattress suture (to reduce lateral crural convexity), and (4) the columella-septal suture (to prevent tip drop and adjust tip projection). The lateral crural mattress suture is the newest of these sutures. It specifically controls undesirable convexity of the lateral crus. The four-suture algorithm is principally designed for primary open rhinoplasties. However, it is also recommended for secondary rhinoplasties. A minor modification is suggested for use in closed rhinoplasties. The algorithm is intended to reduce the difficulty of determining which of the currently available rhinoplasty sutures are useful and in what order they should be used. Illustrative cases are provided. The advantages and disadvantages of this particular algorithm, compared with others that have been proposed, are also reviewed.

Algorithms↗