Surgical Treatment for Aseptic Mediastinitis in the Late Phase after Aortic Root and Arch Replacement / 日本心臓血管外科学会雑誌

Objective: A few cases of an aseptic abscess after thoracic aortic surgery have been reported. However, it sometimes requires surgical treatment because the rapid growth of perigraft fluid collection results in exposure towards the body surface. We discuss the results of our treatment of these cases. Methods: This study was a retrospective analysis. Four of 341 cases who underwent thoracic aortic surgery between April 2013 and March 2020 were included. These cases presented with a bulge of the body surface 10.3 (range, 3-27) months after surgery. Results: Although the fluids looked purulent in all cases, no bacteria were detected. We diagnosed them as aseptic abscess, for which omental implantation was performed. No signs of recurrence have been found in any cases even after 5.4 (range, 1-8.5) years. Conclusions: Omental implantation was effective for controlling aseptic abscess for long-term periods.

A Case of Postoperative Pyoderma Gangrenosum after Mitral Valve Replacement / 日本心臓血管外科学会雑誌

A 47-year-old man had severe mitral regurgitation after severe skin eruption, so mitral valve replacement was electively performed 8 months later. A median sternal wound opened spontaneously and had purulent exudate on the 5th postoperative day (5 POD). We had suspicion of bacterial mediastinitis, so we drained the anterior mediastinum and tried antibiotic treatment. However, the microbiological stains and culture were negative, and adipose tissue was extremely melted with pustules around the wound. Considering other diseases without infection, we consulted to a dermatologist and tried highdose steroid therapy as pyoderma gangrenosum (PG) appeared on the 8 POD. Meanwhile, the sternum was left open and apllied a negative pressure dressing applied with Negative Pressure Wound Therapy (NPWT). The wound responded remarkably to steroid therapy, so we closed the sternum on the 10 POD, and sutured the sternal wound on the 19 POD. We tapered off steroids after the suture. PG can be caused by the trauma of surgery, so we have to make a decision on whether to use high dose steroid therapy in the postoperative period. We report this case as one of the differential diseases that the surgeons must know.

A Case of Redo Aortic Valve Replacement by Right Minithoracotomy Approach with Port Access for Aortic Valve Stenosis after Coronary Artery Bypass Grafting / 日本心臓血管外科学会雑誌

We report a case of redo aortic valve replacement by right minithoracotomy approach for aortic stenosis after coronary artery bypass grafting (CABG). An 81-year-old man was followed-up once a year for 9 years after CABG. He complained of increasing respiratory distress, showed narrowing of the aortic valve area, elevation of the aortic valve pressure gradient, and tricuspid valve regurgitation by echocardiography. He was admitted for surgery. We considered minimally invasive operation would be better for him and performed aortic valve replacement (Carpentier-Edwards Perimaunt valve 19 mm) by a right minithoracotomy approach because graft injury could occur by median sternotomy after CABG, and he had the risks of advanced age, low activities of daily living, and mild dementia. His postoperative course was uneventful. On echocardiography performed at postoperative days 9, the ejection fraction recovered to 75% from 53% before surgery and the mean aortic valve pressure gradient was 8 mmHg. He was discharged on postoperative day 12. Right minithoracotomy approach with port access is a good option for redo operation for aortic valve stenosis after CABG.

THE BED REST FOR TWENTY DAYS ENHANCES THE EXCITABILITY OF SOLEUS SPINAL MOTOR NEURON POOL IN HUMAN / 体力科学

The purpose of this study was to examine the effect of physical inactivity, produced by prolonged bed rest, on the excitability of the spinal motor neuron pool in humans, using the activity of soleus H-reflex.<BR>Eight healthy male subjects underwent continuous bed rest with 6 degree head-down tilt for 20 days (BR group) . Ten different healthy male subjects maintained their usual daily life during the observation period for 20 days (control group) . Recruitment curves of H-reflex and M-wave were obtained from every subject. H slope/M slope (H slp/M sip) which shows the excitability of spinal motor neurons was calculated by using data in the recruitment curve.<BR>The H sip/M sip in the BR group significantly increased after BR, compared to the pre-BR values (p<0.05) . In the control group, however, there were no significant differences in the H slp/M sip between the pre and the post-observation values. At the baseline, the H slp/M sip showed no significant differences between the BR group and the control group. After the BR, the H slp/M sip in the BR group significantly increased compared to the control group after the observation period (p<0.05) .<BR>This study suggests that the excitability of the monosynaptic spinal motor neuron pool is facilitated by physical inactivity during BR.

Effects of Visually Perceived Size on Force Control While Manipulating Small Objects with a Precision Grip / 体力科学

The effects of visual information about object size on grip force programming were investigated. Fifteen subjects (26.1±7.6 yrs) repeated lifts of a cube-like grip apparatus (30×30×30 mm, 30g) using a thumb and index finger, while three boxes of different sizes but equal weight (small : 10×10×60 mm, medium : 30×30×60 mm, large : 60×60×60 mm, 25g) were pseudorandomly presented by attaching beneath the grip apparatus. Lifting tasks were performed in two visual conditions. In the full-vision condition, subjects could perceive the box size prior to the lift-off of the grip apparatus, similar to normal everyday conditions. In the obstructed-vision condition, subjects could not perceive the box size due to the placement of a screen during the initial lifting phase, and only the grip apparatus were visible over the screen. The grip apparatus measured grip and load forces during the trial and we found that the grip and load force applied to the grip apparatus in the full-vision condition significantly increased with box size regardless of equal weight. In contrast, when the size information was removed in the obstructed-vision condition, the force applied for a given box of any size was always that adequate for the largest box, suggesting that the scaling of fingertip force by utilizing size information may be achieved by reducing forces for the smaller boxes on the basis of the force output applied for the largest box, but not by increasing forces on the basis of the force output applied for the smallest box.

Effects of aging on force adaptation during manipulation of a small object using a precision grip / 体力科学

The effects of aging on adaptive force control of precision grip while manipulating a small object were compared between older (84.2±8.9 yrs, n=33) and young adults (19.1±0.24 yrs, n=18) from the following perspectives: (1) adaptation to an unfamiliar object with uncertain physical properties during 16 consecutive lifts ; (2) adaptation to an object with a non-slippery (sandpaper) surface during 12 consecutive lifts, followed by 12 consecutive lifts with a slippery (silk) surface ; and (3) adaptation to objects with different weights (0.49, 0.98, 1.96 and 2.94 N) during 24 lifts (6 consecutive lifts for each weight) .During each trial, grip and load forces were monitored. Safety margin force and slip force were evaluated from the data obtained.<BR>The majority of older adults employed a considerably greater safety margin for an unfamiliar object in the initial trials than did young adults, while the minority of the older adults were able to adapt their safety margin force with a few trials, like the young adults. The older adults who overestimated the safety margin force, however, successfully adjusted their grip force to more optimal levels with repeated lifts, suggesting that the adaptive capability of grip force remained even at 90 years of age. The adaptation of older adults, however, was found to be slower (i. e., required more trials) than that of young adults. Upon encountering surface friction change, the safety margin forces in older adults were more strongly affected by the previous surface condition than those in the young adults. In addition, adaptation to a non-slippery surface seemed more difficult than that to a slippery surface with aging. Upon encountering weight change, older adults showed more difficulties in scaling their safety margin forces according to object weights.<BR>Slower adaptation and difficulty in adaptation to the friction or weight change in older adults may reflect the agerelated decline of tactile sensitivity which impaired the signaling of frictional conditions and various discrete events in the hand. In addition, the lift repetition for force adaptation may possibly reflect the age-related deficit or slowing of central processing capacities related to grip force production.

Effects of Varied Surface Conditions on Regulation of Grip Force During Holding Tasks Using a Precision Grip / 体力科学

The effects of the surface friction of a grasped object on the regulation of grip force during holding tasks using a precision grip were investigated. Using a force transducer-equipped grip apparatus, the grip force and load force acting on the object were measured continuously while surface materials (silk, wood, suede and sandpaper) and load weights (0.98N, 1.96N, 2.94N, 4.90N and 9.81N) were varied. From the recorded data, the average static grip force, slip force, safety margin force and static friction coefficient were evaluated.<BR>It was found that both the slip force and safety margin force increased as the slipperiness of the object surface increased. Significant interactions between surface type and weight were observed in the slip force and static friction coefficient. The interaction effect resulted from the fact that the frictional relationships with the fingers changed according to both weight and surface conditions. This was considered due to the viscoelastic nature of finger skin. An increase in the safety margin force with surface slipperiness was considered due to psychological reaction, probably fear of dropping the object. Unexpected changes in surface conditions caused a greater safety margin force than trials without a surface change, which might also have been associated with psychological reaction to uncertainty of the new surface condition. A relatively large inter-subject variation was found in the slip force and safety margin force relative to slippery surfaces.

CHANGES LN POSTURAL SWAY RELATED TO FATIGUE / 体力科学

The purpose of the present study is to investigate the influence on postural sway of such condition as fatigue resulting from muscular work. Twelve of the male adults (26.7±6.2 yrs old) of a certain airport ground service company were served as the experimental subjects. The measurement of postural sway has been made by measuring the weight at two points of the supporting platform. The degree of postural sway was calculated by using an electronic computer (HITAC-10) . The measurement was carried out before and after the work on each day during the experimental days. The following results were obtained.<BR>On the 1st day with eyes open the ratio of the postural sway after the work to that of before the work (‘after’/‘before’) was 1.25, with eyes closed 113, respectively. On the 2nd day with eyes open it was 1.38, with eyes closed 1.53, respectively. On the last day with eyes open it was 147, with eyes closed 1.23, respectively. The amount of postural sway after the work was greater as compared with that of before the work. The statistical analysis showed that these difference in postural sway was significant (P<0.05-0.001) . The influence of several factors on the changes in postural sway was discussed, together with the experimental results obtained by other authors. In conclusion, these results suggest that balance impairment is mainly due to work-related fatigue.

CHANGES IN THE FREQUENCY OF DISCHARGE OF SINGLE MOTOR UNITS DURING THE PROLONGED VOLUNTARY CONTRACTION IN MAN / 体力科学

The purpose of the present study is threefold : first, to observe simultaneously the changes in both the frequency of motor unit (MU) discharges and the amplitude of surface electromyogram (EMG) during the prolonged and sustained voluntary efforts; and second, to demonstrate the effects of arterial occlusion on the frequency of MU discharges ; lastly, to discuss the mechanism of motor control in the light of the present results and others'. Two male adults participated in the experiment. They were with no nervous disorders, right-handed, aged 24 and 33 years. Each subject was seated with both eyes closed in a chair in an electrically shielded room. He held a weight of 1 kg on his wrist during periods of about 45 minutes. The angle of his elbow joint was maintained at 90 degrees during the course of the experiments. The impulses of MU and the surface EMG were led off from muscles biceps brachii of the left upper arm by using coaxial needle electrodes and surface ones respectively. Discharge intervals of MUs were recorded as ordinate by means of ‘Electro-tachograph’. The action voltages of single MU was monitored for differentiation from that of others with a cathode-ray oscillograph and with a loud speaker. The subject's complaints were noted during the course of the experiments. The following results were obtained.<BR>1. The patterns of changes in the frequency of discharges of MUs were divided into three types. The first pattern showed the steep decrease in the frequency of discharge for short period, and at last the discharge disappeared, the second the gradual prolongation of discharge intervals and the increase in both irregular fluctuation and slow undulation, the third constant frequency of discharge even immediately before the exhaustion of voluntary effort.<BR>2. The undulation and prolongation of discharge intervals appeared during the abolition of blood supply to the arm. It did not recover for about 1 minute even though the arterial occlusion was released.<BR>3. The gradual increase in the amplitude of direct EMG in muscles biceps brachii was observed during holding a weight of constant load.<BR>4. The rotational activity of MU was suggested to exist in the case of prolonged, sustained and voluntary muscular contraction.<BR>5. The gradual increase in prolongation and undulation of MU seems to come from the decrease in number of afferent impulses resulting from fatigue.

CHANGES IN POSTURAL SWAY RELATED TO AGE / 体力科学

The purpose of the present study is to investigate the changes in postural sway (PS) related to age quantitatively. The movement in the center of gravity of the body projected into the base of support was used as a criterion of PS. It was measured in 45 subjects, 23 males and 22 females, ranging in age from 22.1 to 68.1. The subjects maintained erect posture with feet together for about 2 minutes with eyes open, and thereafter with eyes closed respectively. The measurement of PS has been made by measuring the weight at two points of the supporting platform. The degree of PS was calculated by using an electronic computer (HITAC-10-II) . The following results were obtained.<BR>1. The displacements of body's center of gravity per 1 minute with eyes open as well as with eyes closed increased with age. The PS, however, showed a gradual increase with eyes open, and then it did a steep increase with eyes closed from the age of fifties.<BR>2. The PS was reduced to two components, i.e., lateral (X) and antero-posterior (Y) ones. The ratio of the Y component to the X one (Y/X) with eyes open as well as with eyes closed showed a gradual decrease with age.<BR>3. The ratio of X component with eyes closed to that with eyes open was calculated as well as the ratio of Y component. At all ages the ratio in X component was larger than that in Y component.<BR>4. Judging from both the steep increase in PS with eyes closed and the gradual increase with eyes open with age, there seems to exist the modification of static equilibration mechanism in the aged, especially the much degradation of some regulatory function other than visual one.

A CONSIDERATION OF THE PHYSICAL FITNESS OF MIDDLE AND OLDER AGED MEN AT THE SPORTS SAUNA TRAINING CENTER OF NATIONAL STADIUM / 体力科学

The aim of this study was to investigate quantitatively the power ability of middle and older aged men in the vertical jump.<BR>And, we would try to point out the changes with increasing ages and the influences of the environments factor to the power ability.<BR>Based on the environment point of view, we put an emphasis and consideration on those who did physical exercises and also those who drove a car in a daily life.<BR>Subjects were the health 201 men who visited the sports sauna training center of national stadium for physical exercises.<BR>The power was calcurated from the force and velocity concerning of jumper's C.G. during the take off motion. The force was measured by using a strain gage type tranceducer, and the velocity was calcurated by integrating the equation of motion about of C.G.<BR>Result:<BR>The power ability of middle and older aged men in the vertical jump decreased with increasing ages.<BR>The rate of decrease with every 5 years of age was 0.248 horse power, 2.960×10<SUP>-3</SUP> horse power in the maximum power and maximum power per body weight.<BR>In comparison with the power ability of 25 years old, the power ability, in terms of maximum power per body weight, of 35 years old, 45 years old, 55 years old were 90.8%, 81.1%, 59.0%, respectively.<BR>There were evidently differences between trained men and untrained men, and then car driver and no car driver in the power ability. The differences of maximum power per body weight were 12.190 × 10<SUP>-3</SUP> horse power, 9.231×10<SUP>-3</SUP> horse power, respectively.

PHYSIOLOGICAL EFFECT ON THE BODY IN THE SAUNA BATH / 体力科学

Recently, the popular usage of the sauna bath has been greatly increased but this is not necessaeily based upon scientific ground.<BR>This investigation has been made on the most ideal usage time with special emphasis on duration of time in the actual sauna room.<BR>The usage pattern, in view of the times of taking the sauna room and the cold water, has been established.<BR>And then the influences on the body function were measured.<BR>The usage pattern were as follows (Repetition were all 3 times)<BR>(1) 5 minutes stay in the sauna and 1 minute in the water<BR>(2) 7 minutes stay in the sauna and 1 minute in the water<BR>(3) 7 minutes stay in the sauna and 2 minutes in the water<BR>(4) 10 minutes stay in the sauna and 2, 5 minutes in the watar<BR>The result were as follows<BR>1. The usage pattern (1) gave the good result for the function of whole body reaction time, patellar-tendon reflex time, maximum power of vertical jump.<BR>Another usage pattern (2), (3), (4) gave the wrong result for those function.<BR>2. There were no remarkable differences blood pressure, heart rate and skin temperature among the usage pattern (1), (2), (3), (4) .<BR>3. Oxygen intake in the usage pattern (2) gave a large value than the usage pattern (1) .<BR>In the view of the energy expenditure, it was recognized that the usage pattern (2) was the best usage.