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Biomedical subjects

R E Watts

Publications and source records attributed to R E Watts.

5 recordsLinked to original sources
PubMed1994

Dead space loading and exercise limitation in patients with interstitial lung disease.

STUDY DESIGN: We tested the hypothesis that maximal exercise performance in subjects with interstitial lung disease (ILD) is limited by respiratory factors. Assuming this is so, ventilatory stimulation by added dead space (VD) should impair exercise capacity. METHODS: Six subjects with ILD each underwent three maximal incremental exercise studies on a bicycle ergometer; control 1, added VD, and control 2. During the VD study, external VD (500 ml) was added to the circuit, and results obtained were compared with the mean results from the control studies. RESULTS: Exercise duration (TLIM) was significantly less in the VD study when compared to the control study (369 +/- 50 vs 439 +/- 55, p < 0.05), as was work rate (102 +/- 13 vs 125 +/- 14 W, p < 0.05) and peak oxygen uptake per minute (VO2) (1.08 +/- 0.09 vs 1.43 +/- 0.14 L/min, p < 0.05). At end-exercise, the Borg scale was higher in the VD study when compared to the control study (6 +/- 1 vs 5 +/- 1, p < 0.05), while no significant difference in minute ventilation (VI) or oxygen desaturation was noted. When compared to the control study at matched times during exercise, the addition of VD resulted in a significant increase in VI while no significant change was noted in VO2, carbon dioxide output (VcO2), or heart rate (HR). CONCLUSION: The decrease observed in TLIM, work rate, and peak VO2 with added VD, associated with a lack of change in VI or oxygen desaturation at end-exercise, suggests that exercise limitation in ILD is primarily due to respiratory factors.

Adult↗
PubMed1993

Reproducibility of incremental maximal cycle ergometer testing in patients with restrictive lung disease.

BACKGROUND: Exercise testing has become an important tool in the diagnosis and treatment of restrictive lung disease. The reproducibility of variables measured during exercise testing was examined in subjects with stable restrictive lung disease. METHODS: Six subjects, who had never previously undergone exercise testing, each underwent three maximal incremental exercise studies on a bicycle ergometer conducted during a 28 day period. RESULTS: Data collected at rest, before exercise, were not significantly different during the three study days. Comparison of results at the end of the exercise tests from the three studies also revealed no evidence of a significant learning effect. Reproducibility of exercise performance by subjects was assessed by the coefficient of variation. The mean within subject coefficient of variation at the end of the exercise tests was 5.6% for work rate, 7.9% for exercise duration, and 9.5% for dyspnoea. The mean within subject coefficient of variation obtained at the end of the exercise tests was 5.3% for oxygen uptake (VO2), 2.5% for oxygen saturation (SaO2), 4.0% for heart rate (HR), 5.5% for minute ventilation (VE), 5.8% for respiratory frequency (f), and 4.6% for tidal volume (VT). The mean within subject coefficient of variation at 40% and 70% of maximal work rates for VO2 was 5.7% and 5.6% respectively, for SaO2 1.3% and 1.5%, for HR 4.8% and 4.0%, for VE 6.3% and 6.6%, for f 10.1% and 7.8%, and for VT 6.0% and 4.5%. CONCLUSIONS: Variables measured during clinical exercise testing in subjects with restrictive lung disease are highly reproducible. No significant learning effect was found on repeated testing in subjects who had never previously undergone exercise testing.

Adult↗
PubMed1985

Sensory transduction in dorsal cutaneous mechanoreceptors of the frog, Rana pipiens.

Sensory transduction was studied in dorsal skin mechanoreceptors of the frog, Rana pipiens. The skin was clamped and stretched before being stimulated with the tip of a glass rod mounted on a servo-controlled loudspeaker. Afferent activity was recorded extracellularly from a dorsal cutaneous nerve. Three groups of sensory units could be identified by the size of their recorded action potentials and their response to mechanical stimuli. Action potential amplitudes for the three groups were: less than 50 microV (group I), 50-250 microV (group II) and greater than 300 microV (group III). Group II were selected for further study because of their amplitude and their resistance to fatigue. Three types of mechanical stimuli were used to examine the dynamic properties of group II receptors, steps, sinusoids, and band-limited random displacement. In each case the responses could be well fitted by a power-law model with a fractional exponent of time or frequency. Random stimulation of a large number of group II receptors showed considerable variability in their sensitivity and in their dynamic behavior, as measured by the fractional exponent of frequency. However, the distributions of these two parameters were both unimodal and strongly clustered around the modes, suggesting that the recordings were from a single class of receptors. Varying the temperature of the receptors had little effect on their sensitivity or dynamic properties. This is in contrast to findings on other mechanoreceptors. Doubling the potassium concentration in the bathing solution affected the dynamic properties of the receptors within 5 min but several distinct patterns of change in dynamic behavior were seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗