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Biomedical subjects

C Hendricks

Publications and source records attributed to C Hendricks.

13 recordsLinked to original sources
PubMed1991

Prevention of spinal cord injury: an elementary education approach.

Spinal cord injury (SCI) results in permanent paralysis and most often happens to teenagers and young adults. High risk behaviors are most often the cause; therefore these injuries are often preventable. In response to a gap in existing prevention programs, an elementary age SCI prevention program was developed, designed for implementation by teachers. Evaluation was carried out via a quasi-experimental pre-post comparison group design. Experimental students demonstrated significantly improved knowledge of SCI and its prevention. Similar changes in self-reported safety belt use were not noted. Development of the curriculum, related grant activities, and plans for national dissemination are described.

Child↗
PubMed1990

[Early diagnostic criteria of ankylosing spondylitis in patients with acute anterior uveitis].

A group of 59 patients with acute anterior uveitis (AAU) were examined for ankylosing spondylitis (AS) according to the New York criteria und criteria for early diagnosis of AS: 17/59 (29%) presented AS according to the New York criteria: a further 13/59 (22%) were classified as having incipient AS according to the early diagnosis criteria. These findings indicate that in a group of AAU patients there are, in addition to patients with definite AS, patients with initial AS though X-rays of the sacroiliac joints are still negative or equivocal. Early diagnosis criteria seem to be useful for identification of these patients at an early stage and can be used as a major selection criterion for monitoring programs.

Acute Disease↗
PubMed1988

Visual field constriction caused by colored contact lenses.

Goldmann visual field testing was performed on ten patients while they were wearing the recently released DuraSoft 3 colored soft contact lenses. All patients but one had visual field constriction ranging from 5 degrees to 20 degrees. When the areas inside the three tested isopters were averaged, the amount of field loss ranged from 21% to 47%. Contact lens fitters as well as wearers should be warned of this potential complication.

Color↗
PubMed1988

Characteristics of the upper airway pressure-flow relationship during sleep.

In examining the mechanical properties of the respiratory system during sleep in healthy humans, we observed that the inspiratory pressure-flow relationship of the upper airway was often flow limited and too curvilinear to be predicted by the Rohrer equation. The purposes of this study were 1) to describe a mathematical model that would better define the inspiratory pressure-flow relationship of the upper airway during sleep and 2) to identify the segment of airway responsible for the sleep-related flow limitation. We measured nasal and total supralaryngeal pressure and flow during wakefulness and stage 2 sleep in five healthy male subjects lying supine. A right rectangular hyperbolic equation, V = (alpha P)/(beta + P), where V is flow, P is pressure, alpha is an asymptote for peak flow, and beta is pressure at a flow of alpha/2, was used in its linear form, P/V = (beta/alpha) + (P/alpha). The goodness of fit of the new equation was compared with that for the linearized Rohrer equation P/V = K1 + K2V. During wakefulness the fit of the hyperbolic equation to the actual pressure-flow data was equivalent to or significantly better than that for the Rohrer equation. During sleep the fit of the hyperbolic equation was superior to that for the Rohrer equation. For the whole supralaryngeal airway during sleep, the correlation coefficient for the hyperbolic equation was 0.90 +/- 0.50, and for the Rohrer equation it was 0.49 +/- 0.25. The flow-limiting segment was located within the pharyngeal airway, not in the nose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Alteration in obstructive apnea pattern induced by changes in oxygen- and carbon-dioxide-inspired concentrations.

In patients with obstructive apnea, it was hypothesized that stimulation of the ventilatory system by hypercapnia during sleep would increase pharyngeal inspiratory muscle activity and thereby increase upper airway caliber. We predicted that this increase in caliber would decrease the number of apneas and sleep time spent apneic. In contrast, suppression of the ventilatory system activity with hyperoxia was predicted to decrease both inspiratory muscle activity and pharyngeal caliber and thereby increase the number of apneas and apnea time. In all 7 patients with symptomatic obstructive sleep apnea studied, 3 with upper airway narrowing obvious during wakefulness, inhalation of 3 to 6% CO2 preferentially stimulated upper airway inspiratory muscle tonic electrical activity relative to the activity of chest wall inspiratory muscles and diminished periodic breathing. Apnea time decreased from 60 +/- 2% (mean +/- SEM) of sleep time during ambient air inhalation to 12 +/- 3% during CO2 inhalation; 50% O2 had the reverse effect on inspiratory muscle tonic electrical activity and increased apnea time to 75 +/- 5% of sleep time. We conclude that manipulation of inspiratory muscle tonic activity and alteration of the pattern of breathing by CO2 and O2 inhalation lead to significant changes in the pattern of upper airway inspiratory collapse during sleep. We speculate that physiologic variables related to the control of upper airway inspiratory muscle function are instrumental in the pathophysiology of obstructive sleep apnea.

Air↗
PubMed1988

Palate and hypopharynx--sites of inspiratory narrowing of the upper airway during sleep.

In order to determine the specific site of inspiratory narrowing within the upper airway during sleep, we measured supralaryngeal, oropharyngeal, and nasopharyngeal pressures and inspiratory flow in 11 healthy nonsnoring male subjects awake and in NREM sleep. Resistance was calculated at 0.01 L/s, a point along the linear portion of the pressure-flow relationship, and at peak inspiratory pressure, a point within the curvilinear section of the pressure-flow relationship. During sleep, nasal resistance increased minimally. At peak inspiratory pressure, both transpalatal and hypopharyngeal resistances increased more than 700% in NREM sleep. At 0.01 L/s inspiratory flow, transpalatal and hypopharyngeal resistances increased 200 and 400%, respectively. Six subjects had a greater increase in transpalatal than hypopharyngeal resistance, and five subjects had a greater increase in hypopharyngeal than transpalatal resistance. Three subjects in each of these two subgroups had an increase in resistance exclusively across the palate or the hypopharynx. The site of increased resistance during sleep was not predictable from awake resistance measurements. From these data, we conclude that the site of inspiratory narrowing within the upper airway during sleep occurs primarily at either the level of the palate or hypopharynx and is variable among subjects. The pattern of palatal or hypopharyngeal narrowing is the same as that observed in obstructive sleep apnea patients, but quantitatively different.

Adult↗
PubMed1987

Neuromuscular and mechanical responses to inspiratory resistive loading during sleep.

The purposes of this study were 1) to characterize the immediate inspiratory muscle and ventilation responses to inspiratory resistive loading during sleep in humans and 2) to determine whether upper airway caliber was compromised in the presence of a resistive load. Ventilation variables, chest wall, and upper airway inspiratory muscle electromyograms (EMG), and upper airway resistance were measured for two breaths immediately preceding and immediately following six applications of an inspiratory resistive load of 15 cmH2O.l-1 X s during wakefulness and stage 2 sleep. During wakefulness, chest wall inspiratory peak EMG activity increased 40 +/- 15% (SE), and inspiratory time increased 20 +/- 5%. Therefore, the rate of rise of chest wall EMG increased 14 +/- 10.9% (NS). Upper airway inspiratory muscle activity changed in an inconsistent fashion with application of the load. Tidal volume decreased 16 +/- 6%, and upper airway resistance increased 141 +/- 23% above pre-load levels. During sleep, there was no significant chest wall or upper airway inspiratory muscle or timing responses to loading. Tidal volume decreased 40 +/- 7% and upper airway resistance increased 188 +/- 52%, changes greater than those observed during wakefulness. We conclude that 1) the immediate inspiratory muscle and timing responses observed during inspiratory resistive loading in wakefulness were absent during sleep, 2) there was inadequate activation of upper airway inspiratory muscle activity to compensate for the increased upper airway inspiratory subatmospheric pressure present during loading, and 3) the alteration in upper airway mechanics during resistive loading was greater during sleep than wakefulness.

Adult↗
PubMed1987

Changes in inspiratory muscle electrical activity and upper airway resistance during periodic breathing induced by hypoxia during sleep.

We hypothesized that: the balance of electrical activities between the upper airway and chest wall inspiratory muscles affects upper airway inspiratory caliber, and at low levels of central respiratory neural efferent activity, an imbalance between the electrical activities of these 2 inspiratory muscle groups exists that results in a decreased upper airway caliber. These hypotheses were tested during periodic breathing induced by mild hypoxemia in NREM sleep in 9 healthy male subjects. In 6 subjects during periodic breathing as central respiratory neural activity decreased, the tonic and phasic EMG activity of the upper airway inspiratory muscles decreased at a rate greater than that of the chest wall EMG activity. When the ratio of upper airway to chest wall EMG activity decreased below a critical level, which was reproducible across subjects, upper airway inspiratory resistance increased hyperbolically. Resistance at peak inspiratory flow increased from 4.10 +/- 0.97 (mean +/- SEM) to 48.70 +/- 21.00 cmH2O/L/s as tidal volume decreased from 0.79 +/- 0.12 to 0.20 +/- 0.02 L during periodic breathing in these subjects. In the 3 remaining subjects, the ratio of the upper airway to chest wall EMG activity did not decrease below the critical level as the activity of both muscle groups decreased during periodic breathing, and upper airway resistance did not increase. We conclude that within the confines of this study the nonlinear activation of upper airway and chest wall inspiratory muscles contributed to fluctuations in upper airway resistance observed during periodic breathing in sleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Functional relations of the rodent claustral-entorhinal-hippocampal system.

Electrophysiological studies of the claustrum of rat demonstrate functional connections with the limbic system (dentate gyrus, hippocampus) via the entorhinal cortex. The pathways show reciprocal connectivity, a degree of topological organization and the capacity for a long-term response potentiation in the claustral projection to entorhinal cortex. The hypothesis that claustrum acts to functionally link neocortical regions with components of the limbic system is considered.

Animals↗
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Child, Preschool↗