Assessment of the dynamic interactions between heart rate and arterial pressure by the cross time-frequency analysis.

In this study, a framework for the characterization of the dynamic interactions between RR variability (RRV) and systolic arterial pressure variability (SAPV) is proposed. The methodology accounts for the intrinsic non-stationarity of the cardiovascular system and includes the assessment of both the strength and the prevalent direction of local coupling. The smoothed pseudo-Wigner-Ville distribution (SPWVD) is used to estimate the time-frequency (TF) power, coherence, and phase-difference spectra with fine TF resolution. The interactions between the signals are quantified by time-varying indices, including the local coupling, phase differences, time delay, and baroreflex sensitivity (BRS). Every index is extracted from a specific TF region, localized by combining information from the different spectra. In 14 healthy subjects, a head-up tilt provoked an abrupt decrease in the cardiovascular coupling; a rapid change in the phase difference (from 0.37 ± 0.23 to -0.27 ± 0.22 rad) and time delay (from 0.26 ± 0.14 to -0.16 ± 0.16 s) in the high-frequency band; and a decrease in the BRS (from 23.72 ± 7.66 to 6.92 ± 2.51 ms mmHg(-1)). In the low-frequency range, during a head-up tilt, restoration of the baseline level of cardiovascular coupling took about 2 min and SAPV preceded RRV by about 0.85 s during the whole test. The analysis of the Eurobavar data set, which includes subjects with intact as well as impaired baroreflex, showed that the presented methodology represents an improved TF generalization of traditional time-invariant methodologies and can reveal dysfunctions in subjects with baroreflex impairment. Additionally, the results also suggest the use of non-stationary signal-processing techniques to analyze signals recorded under conditions that are usually supposed to be stationary.

Comparative parameters of fertility regulation as related to STD / HIV infections. An overview.

PIP: The sexually transmitted disease (STD), chancroid, is the greatest factor for HIV infections in Africa like syphilis is in the US. 3 physicians suggest that reducing the incidence of STDs may reduce the spread of HIV. Risk factors for HIV include current or history of STD in women and bisexual men, pelvic inflammatory disease, semen, copper releasing IUDs, contraceptive dermatitis, malnutrition/food allergy, environmental pollutants, genetic make up, and prostitutes. HIV infected persons should use condoms to not only protect partners but to prevent repeated contact with HIV which influences the clinical outcome. Condom use for contraception is not widely practiced in some areas, however, including Central Africa and Haiti. Condom use has increased in the US because IUDs have been removed from the market, fear of HIV infection, and discontinued use of oral contraceptives in older women. Urticarial reactions secondary to a copper IUD often occur in adolescent women, but clears when the IUD is removed. Traces of nickel in the copper wire used in IUDs often induce an allergic reaction. Allergic reactions are cofactors of HIV which can be made worse if coupled with excessive menstrual bleeding and HIV infected semen cells entering the uterus via the IUD tail. Many countries have integrated family planning services with other public health services, such as STD clinics that address AIDS. Integrated services should provide STD services and contraception and involve males and be accessible to them. Comprehensive school based clinical model should be implemented into schools and colleges. Counselors should advice HIV infected women not to have any more children. These women should get top priority to family planning services. HIV antibody testing for women should be done at any center where women may be including family planning centers and prisons.^ieng