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To examine the baroreflex response in humans during acute high-altitude exposure, the carotid baroreflex cardiac responsiveness was studied using a neck chamber in seven unacclimatized male subjects. Measurements were made in a high-altitude chamber on separate days at sea level and during 1-h exposure at two different altitudes of 3,800 m [partial pressure of oxygen in inspired air (Pi O2 ) = 90 mmHg] and 4,300 m (Pi O2  = 82 mmHg). R-R intervals were plotted against neck chamber pressures, and the baroreceptor response was analyzed by applying a four-parameter sigmoidal logistic function. The baroreceptor response curve shifted downward in either altitude, reflecting a tachycardic response at high altitude, and the magnitude of the shift was greater at 4,300 m than at 3,800 m. There was no change in the sigmoidal parameters at 3,800 m compared with sea level except for a reduction ( P < 0.05) of the minimum R-R interval. At 4,300 m the maximal R-R range, slope coefficient, minimum R-R interval, and maximal gain of the curve decreased significantly ( P < 0.05) compared with sea level values, whereas the centering point of the curve remained unchanged. These results suggest that hypoxia (Pi O2  = 82 mmHg) reduces the sensitivity of carotid baroreflex cardiac response.

A prospective study was carried out on the clinical application and features of a carbon fibre reinforced plastic leg orthosis (carbon orthosis) for polio survivors. The subjects comprised 9 polio survivors, and 11 carbon knee-ankle-foot orthoses (KAFOs) were prescribed, fabricated, and checked out at the authors' post-polio clinic. Walking was classified based on the functional ambulatory category, and the features of walking with a carbon orthosis were self-evaluated by using a visual analogue scale. The period from modelling a cast to completion was 55 + 25 days; the weight of a carbon KAFO was 27.8% lighter than that of the ordinary KAFO; the standard carbon KAFO was 50% more expensive than the ordinary KAFO. The carbon KAFO remained undamaged for at least 2 years. It improved the scores in the functional ambulation categories, but there was no difference between walking with an ordinary and with a carbon KAFO. The self-evaluation of walking with a carbon KAFO revealed that the subjects using a carbon KAFO were satisfied with their carbon KAFO. The carbon KAFO is lightweight, durable, slim and smart, and is positively indicated for polio survivors.

These experiments were conducted to examine whether changes in central and peripheral hemodynamics were proportional to muscle sympathetic nerve activity (MSNA) during graded head-down tilt (HDT). Twelve healthy males (19-42 yr old) underwent HDT at 15 degrees and 30 degrees for 10 min each with a 10-min rest period between the trials. MSNA at 15 degrees HDT declined by 31 +/- 5% (P < 0.05) for burst rate and by 37 +/- 3% (P < 0.05) for total activity. At 30 degrees HDT, the reduction in MSNA was 51 +/- 5% for burst rate (P < 0.05 vs. 15 degrees HDT) and 46 +/- 5% for total activity (P < 0.05 vs. 15 degrees HDT). Stroke volume increased (P < 0.05) during both 15 degrees and 30 degrees HDT, but heart rate and blood pressure remained unchanged. A concurrent increase in central venous pressure (P < 0.05) and stroke volume with a reduction of thoracic impedance (P < 0.05) suggests that both pressure and volume in the atrium were elevated during HDT, and the magnitude of these changes was greater (P < 0.05) at 30 degrees HDT than at 15 degrees HDT. Forearm blood flow increased during HDT at both 15 degrees and 30 degrees, and the magnitude of the increase was greater (P < 0.05) at 30 degrees HDT. It is concluded that the magnitude of the loading of the cardiopulmonary mechanoreceptors during HDT was higher at 30 degrees in comparison to 15 degrees. This increased the afferent firing rate by the cardiopulmonary receptors and probably inhibited sympathetic outflow in the central nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

The gait efficiency of polio survivors with a carbon KAFO was objectively better than those without an orthosis or with an ordinary KAFO.

We examined the dynamics of capsule swallowing by healthy young men using the anterior-posterior view of videofluoroscopy as a first step in a study on capsule swallowing by dysphagic patients. The subjects were 14 healthy men who did not have any complaint of dysphagia. They were asked to swallow a #4 hard gelatin capsule filled with barium sulfate with 15 ml of water during the videofluoroscopic examination. This examination was repeated three times for each subject (total of 42 trials). In four of the 14 subjects, a swallowed capsule was retained at the upper esophageal sphincter, or the broncho-aortic constriction of the esophagus, or the lower esophageal sphincter. Except where retention occurred, the average capsule transit time from the mouth to the stomach was 6.0 +/- 2.4 s. Three of the four subjects who had capsule retention did not realize that the swallowed capsule was retained en route to the stomach. By considering the dynamics of swallowing a capsule with 15 ml of water in healthy men, we should be able to reveal the dynamics of capsule swallowing in dysphagic patients, and the capsule transit time from the mouth to the stomach.

: Coughing is an important protective mechanism for keeping the airway clear, and adequate voluntary coughing reduces the risk of aspiration in patients with deglutition disorders. The purpose of this study was to compare the peak cough f low (PCF) of stroke patients with and without dysphagia and to identify the physical and respiratory determinants of PCF. Using a spirometer, we measured and compared the PCFs of 10 stroke patients with dysphagia (SPD), 20 stroke patients without dysphagia (SP) and 10 gender and age matched healthy controls (HC) recruited by using a notice at a clinic and in newspapers. The PCF of the SPD (mean ± SD, 160.1 ± 68.7 l/min) was significantly lower than that of the SP and HC (297.2 ± 114.2 l/min and 462.0 ± 84.4 l/min, respectively; one-way ANOVA, Scheffe's test, P < 0.05). The vital capacity (VC) and inspiratory reserve volume (IRV) of the SPD were lower than those of the HC. Stepwise multivariate regression analysis revealed that IRV and ambulation function (Functional Ambulation Categories, FAC) contributed 50% and 17% to the variance of PCF (P < 0.05), respectively. It is suggested that respiratory function, especially IRV, is important for maintaining PCF in SPD.

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