Effect of age on the digit blood flow response to sedative concentrations of nitrous oxide

Twenty healthy male subjects [11 young, x̄ = 25.4 ± 0.8 (SEM) years old; 9 elderly, x̄ = 64.5 ± 0.7 years] volunteered for a study designed to investigate the effect of age on several cardiovascular parameters to inhaled N(2)O-O(2). The protocol was designed to mimic the administration of N(2)O-O(2) for sedation in the dental office, although no dental treatment was performed. Clinical criteria were used to judge the appropriate sedative level for each subject; no attempt was made to establish doseresponse relationships. Digit blood flow was measured by strain-gauge plethysmography, and heart rate, arterial blood pressure, respiratory rate, and skin temperature were monitored and recorded. N(2)O and CO(2) levels were monitored in end-tidal gas samples by gas chromatography; machine gauge readings were calibrated against known gas mixtures by the same technique.Under the conditions of this experiment both healthy young and healthy elderly subjects experienced a marked (200-300%) increase in digit blood flow during N(2)O inhalation, compared to that during air and 100% O(2) inhalation. There was no significant difference in the degree of flow increase between young and elderly subjects. Also, there were no significant differences in the response of these healthy young and healthy elderly subjects to sedative concentrations of N(2)O with regard to heart rate, arterial blood pressure, respiratory rate, skin temperature, or mean end-tidal CO(2) levels. The data indicate that N(2)O, in the concentrations routinely administered in the dental office for sedation, does not have a differential effect on the measured parameters in healthy elderly and healthy young males.