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At least 217 records · Page 12Linked to original sources

Spirometry in normal subjects in sitting, prone, and supine positions.

OBJECTIVE: Determine whether pulmonary function testing is affected by patient positioning. METHODS: In a descriptive study with measurements made in a sequential but randomized order at a university-based pulmonary function laboratory, 20 healthy men, ages 18-50 years, were evaluated with spirometric assessment of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and maximum voluntary ventilation (MVV) in the sitting, supine, and prone positions. Subjects were excluded for body mass index (BMI) > 30 kg/m2 or abnormal baseline spirometry. RESULTS: Comparing sitting to supine and prone positions, there was a statistically significant decline in the spirometry values (reported as percent of predicted normal +/- standard error of the mean). FVC was 102% +/- 4% while sitting, 95% +/- 4% while supine, and 94% +/- 4% while prone. FEV1 was 104% +/- 3% while sitting, 96% +/- 3% while supine, and 94% +/- 3% while prone. MVV was 115% +/- 4% while sitting, 102% +/- 4% while supine, and 97% +/- 3% prone. CONCLUSION: In healthy men with BMI < 30 kg/m2, changing from the sitting to supine or prone position results in statistically significant change in respiratory pattern. However, all spirometry values in each position were normal by American Thoracic Society definitions.

Adolescent↗

Spontaneous arousability in prone and supine position in healthy infants.

STUDY OBJECTIVE: Compared with control infants, those who will be future victims of sudden infant death syndrome (SIDS) show a decreased arousability during sleep, with fewer cortical arousals and more-frequent subcortical activations. These findings suggest an incomplete arousal process in victims of SIDS. Prone sleep position, a major risk factor for SIDS, has been reported to reduce arousal responses during sleep. The present study was undertaken to evaluate whether the prone sleep position impairs the arousal process in healthy infants. METHODS: Twenty-four healthy infants were studied polygraphically during 1 night; 12 infants regularly slept supine and 12 infants regularly slept prone. Infants were matched for sex, gestational age, and age at recording. Arousals were differentiated into subcortical activations or cortical arousals, according to the presence of autonomic and/or electroencephalographic changes. Frequencies of subcortical activations and cortical arousals were compared in the prone- and the supine-sleeping infants. RESULTS: Compared with supine sleepers, prone sleepers had significantly fewer cortical arousals during rapid eye movement (REM) sleep (p = .043). There were no significant differences in cortical arousals between the 2 groups during non-REM sleep. No significant differences were seen in the frequencies of subcortical activations during both REM and non-REM sleep between supine and prone sleepers. The ratio of cortical arousal to subcortical activation showed no significant differences between the prone and the supine sleepers. CONCLUSIONS: Prone sleep position decreased the frequency of cortical arousals but did not change the frequency of subcortical activations, as has been previously found in SIDS victims. These results suggest specific pathways for impairment of the arousal process in SIDS victims.

Arousal↗

Characteristics of human body dynamic responses to landing impact in supine position.

OBJECTIVE: To study the characteristics of human body dynamic responses to landing impact. METHOD: Five healthy young men were exposed to 4-10 G for 50-80 ms half-sine acceleration pulse at 20 degrees supine angle and 10 G for 50 ms impact at 30 degrees to 60 degrees supine angles. The acceleration curves on the dropping platform of the impact tower, the seat, the human head, shoulder, chest and ilium, as well as ECG of the subjects were recorded. RESULT: The peaks of acceleration at the subject head, shoulder, chest, and ilium along chest-back direction rose with the increase of the impact level. The overshoots of acceleration at the subject head along head-ilium direction and chest-back direction were 93% and 102% respectively for 10 G at 20 degrees supine angle. With increase of supine angle, acceleration response at the subject along chest-back direction decreased. Acceleration response at the subject head along head-ilium direction was minimum at 40 degrees supine angle. CONCLUSION: Transfer function of the human body to landing impact demonstrated that human body had a series of resonance frequencies which were 25 Hz, 34 Hz, 39 Hz, 43 Hz, 50 Hz, 64 Hz, and 70 Hz respectively.

Acceleration↗