Dynamic ventilatory responses of females and males to acute isocapnic and poikilocapnic hypoxia.

The human ventilatory response during acute hypoxia appears to be biphasic (growth and decay), but the effect of sex on the size and timing of this response is not known. We studied the effects of 15min of poikilocapnic and isocapnic hypoxia (FiO2≈0.10) on ventilation (V˙i) in 14 healthy female and 13 healthy male subjects. Parameters (amplitudes, time delays, time constants) describing individual V˙i responses were estimated using a biexponential function. There were no significant effects of sex on any of these parameters. CO2 regulation significantly altered the amplitudes of growth and decay phases and the onset of the latter phase in females and males. These human data suggest that sex does not affect the biphasic response of ventilation during hypoxia. However, additional evidence in this study suggests that sex influences the breathing frequency response during hypoxia and that this effect depends on the control of CO2.

Effect of adhesive agent and fissure morphology on the in vitro microleakage and penetrability of pit and fissure sealants.

OBJECTIVE: To evaluate the effect of adhesive agents and fissure morphology on the microleakage and penetrability of pit and fissure sealants. METHOD AND MATERIALS: Sealants used in this study included Aegis (Bosworth), conseal f (Southern Dental Industries), and Admira Seal (Voco). Adhesive agents included Optibond Solo Plus (sds/Kerr) and Clearfil S3Bond (Kuraray). Ninety extracted permanent molars were randomly assigned to 9 groups combining sealant and adhesive agent materials. A sealant and control group (phosphoric acid etch only) was also included. Dye penetration (microleakage), penetrability, and fissure morphology assessment was performed for the treatment groups through microscopic evaluation. RESULTS: Significant (P = .003) differences in microleakage were exhibited, with the Aegis + control and Aegis + Optibond Solo Plus groups displaying less leakage, while significant (P = .03) differences were also noted between groups regarding penetrability. Fissure morphology was not a significant (P = .82) factor affecting microleakage; however, fissure type did significantly (P < .001) impact penetrability. No correlation was found between the extent of microleakage and penetrability. CONCLUSION: Application of sealants using phosphoric acid as a conditioning agent revealed superior results, while the use of adhesives was found to be unnecessary.

Oxygen cost of ventilation during incremental exercise to VO2 max.

OBJECTIVE: Evidence of significant oxygen requirements for ventilation during exercise (exercise hyperpnoea) prompted the investigation into whether the oxygen cost of ventilation affects the presence of a whole-body VO(2) plateau at maximal exercise. The purposes of this study were to: (i) use isocapnic hyperpnoea trials to determine the oxygen cost of ventilation (VO(2VENT)) across a range of ventilation (V(E)); (ii) determine the mean VO(2VENT) at maximal exercise expressed as a percentage of whole-body VO(2) max; and (iii) determine if a plateau in VO(2) is more evident when the VO(2VENT) is subtracted from whole-body VO(2) at maximal exercise. METHODS: A total of 21 subjects performed a VO(2) max test on the cycle ergometer to determine the range of V(E) for each subject. From the initial VO(2) max test, nine V(E) values across the range of V(E) were selected for each subject and the oxygen cost of each was measured. RESULTS: The mean maximal VO(2VENT) equalled 8.8 +/- 3.3% of VO(2) max and ranged from 5.0% to 17.6%. VO(2VENT) increased exponentially with increasing V(E), but there was considerable subject variability in the oxygen cost per litre of V(E) as V(E) increased. Subtracting the VO(2VENT) from whole-body VO(2) at maximal exercise increased the detection of a plateau in VO(2) at VO(2) max. CONCLUSIONS: The data of the present study indicate that the VO(2VENT) is a significant portion of VO(2) max and may be a limiting factor of maximal exercise performance in some subjects.