Direct measurement of blood pressure using a fluid-filled catheter and an electromechanical transducer is widely accepted in clinical practice. However, errors associated with the measurement are often not appreciated and these catheter-manometer systems are frequently unable to accurately reproduce applied pressures. To assess the accuracy of catheter-manometer systems used for invasive arterial blood pressure measurements, in vitro and in vivo evaluations were performed. The frequency response (described in terms of damped natural frequency and damping factor) for a variety of cannulae, pressure tubing and stopcocks (and combinations thereof) and their dependence on various parameters (catheter length, lumen diameter, fluid temperature and catheter material) were measured using an hydraulic pressure generator. The design and construction details of the pressure generator are presented. It was found that the damped natural frequency of the catheter-manometer system is directly proportional to lumen diameter of the pressure tubing/catheter. Furthermore, damping factor is inversely related to the damped natural frequency and stiffer catheter material (for identical radius ratios) results in higher damped natural frequency. Catheter length is inversely related to damped natural frequency and the resonant frequency decreases for an increase in fluid operating temperature. It was established that all catheter-manometer systems tested were under-damped (0.15 < β < 0.37) and that the damped natural frequency ranged from 10.5 Hz for 1500 mm to 27.0 Hz for pressure tubing of 300 mm in length. Furthermore, catheter-manometer systems which had pressure tubing in excess of 300 mm in length did not comply with the bandwidth requirements for accurate dynamic blood pressure measurement. For the in vivo assessment of the catheter-manometer system, the blood pressure waveform was analysed in the time and frequency domains. It was established that in 60 percent of the cases, the systolic pressure peak was higher when measured by a narrow bandwidth catheter-manometer system compared to that measured by a wide bandwidth system. Furthermore, values of dp/dt maximum were lower for wide bandwidth catheter-manometer systems than those measured by narrow bandwidth systems for heart rates above 90 beats per minute. In the frequency domain analysis, artifact was sometimes found to occur at frequencies higher than the bandwidth of the catheter-manometer system. This high frequency artifact was found to distort the blood pressure waveform and resulted in false high dp/dt and peak systolic pressures.

INTRODUÇÃO: Não se sabe se o ajuste da terapia anti-hipertensiva baseado na Monitorização Residencial da Pressão Arterial (MRPA) pode melhorar o controle da pressão arterial em pacientes em hemodiálise. OBJETIVOS: Comparar a redução da pressão arterial (PA) e do índice de massa ventricular esquerda (IMVE) obtido com o uso da MRPA em relação às medidas da PA pré-diálise em pacientes em hemodiálise. MÉTODOS: Pacientes hipertensos em hemodiálise foram randomizados para ter a terapia anti-hipertensiva ajustada em dois grupos: controle, baseado na PA pré-diálise, e intervenção, baseada na MRPA. Antes e após 06 meses de acompanhamento, os pacientes realizaram Monitorização Ambulatorial da Pressão Arterial (MAPA) por 24 horas, MRPA durante uma semana e ecocardiograma transtorácico. RESULTADOS: 34 e 31 pacientes completaram o estudo no grupo intervenção e controle, respectivamente. As pressões arteriais sistólica (PAS) e diastólica (PAD) no período interdialítico pela MAPA foram significativamente menores no grupo intervenção em relação ao grupo controle no final do estudo (média 24 horas: 135 ± 13mmHg / 76 ± 7mmHg versus 147 ± 15mmHg / 79 ± 8mmHg, respectivamente - p<0,05). Na análise da MRPA, o grupo intervenção apresentou redução significativa somente para a PAS em comparação ao grupo controle (média semanal: 144 ± 21mmHg versus 154 ± 22 mmHg, respectivamente - p<0,05). Não houve diferenças entre os grupos intervenção e controle em relação ao IMVE ao final do estudo (108 ± 35 g/m2 versus 110 ±33 g/m2, respectivamente - p>0,05). CONCLUSÕES: O uso sistemático da MRPA no ajuste da terapia anti-hipertensiva em pacientes em hemodiálise propiciou maior controle da PA no período interdialítico em comparação às medidas da PA pré-diálise. A MRPA pode ser usada como um instrumento adjuvante útil no controle da pressão arterial em pacientes em hemodiálise / INTRODUCTION: It is not known whether the adjustment of the antihypertensive therapy based on Home Blood Pressure Monitoring (HBPM) can improve blood pressure (BP) control in hemodialysis patients. OBJECTIVES: To compare the reduction in BP and in the left ventricular mass index (LVMI) obtained with the use of HBPM in relation to that achieved with predialysis BP measurements in hemodialysis patients. METHODS: Hypertensive patients on hemodialysis were randomized to have the antihypertensive therapy adjusted according two groups: control, based on the predialysis BP measurements, and intervention, based on HBPM. Before and after 06 months of follow-up, patients were submitted to Ambulatory Blood Pressure Monitoring (ABPM) for 24 hours, HBPM during one week and transthoracic echocardiogram. RESULTS: 34 and 31 patients completed the study in the intervention and control groups, respectively. The systolic (SBP) and diastolic (DBP) blood pressure in the interdialytic period by ABPM were significantly lower in the intervention group compared with the control group at the end of the study (mean 24-hours BP: 135 ± 13 mm Hg / 76 ± 7 mmHg versus 147 ± 15 mm Hg / 79 ± 8 mmHg, respectively - p <0.05). When the interdialytic BP was analysed by HBPM, the intervention group showed significant reduction only for the PAS in comparison with control group (mean weekly BP: 144 ± 21 mm Hg versus 154 ± 22 mm Hg, respectively - p <0.05). There were no differences between intervention and control groups in relation to LVMI at the end of the study (108 ± 36 g/m2 versus 110 ± 33 g/m2, respectively - p> 0.05). CONCLUSIONS: The systematic use of HBPM in the adjustment of antihypertensive therapy in patients on hemodialysis has led to better control of BP during interdialytic period compared to that achieved with the predialysis BP measurements. The HBPM can be used as a useful adjunct instrument to control blood pressure in hemodialysis patients

INTRODUÇÃO: Não se sabe se o ajuste da terapia anti-hipertensiva baseado na Monitorização Residencial da Pressão Arterial (MRPA) pode melhorar o controle da pressão arterial em pacientes em hemodiálise. OBJETIVOS: Comparar a redução da pressão arterial (PA) e do índice de massa ventricular esquerda (IMVE) obtido com o uso da MRPA em relação às medidas da PA pré-diálise em pacientes em hemodiálise. MÉTODOS: Pacientes hipertensos em hemodiálise foram randomizados para ter a terapia anti-hipertensiva ajustada em dois grupos: controle, baseado na PA pré-diálise, e intervenção, baseada na MRPA. Antes e após 06 meses de acompanhamento, os pacientes realizaram Monitorização Ambulatorial da Pressão Arterial (MAPA) por 24 horas, MRPA durante uma semana e ecocardiograma transtorácico. RESULTADOS: 34 e 31 pacientes completaram o estudo no grupo intervenção e controle, respectivamente. As pressões arteriais sistólica (PAS) e diastólica (PAD) no período interdialítico pela MAPA foram significativamente menores no grupo intervenção em relação ao grupo controle no final do estudo (média 24 horas: 135 ± 13mmHg / 76 ± 7mmHg versus 147 ± 15mmHg / 79 ± 8mmHg, respectivamente - p<0,05). Na análise da MRPA, o grupo intervenção apresentou redução significativa somente para a PAS em comparação ao grupo controle (média semanal: 144 ± 21mmHg versus 154 ± 22 mmHg, respectivamente - p<0,05). Não houve diferenças entre os grupos intervenção e controle em relação ao IMVE ao final do estudo (108 ± 35 g/m2 versus 110 ±33 g/m2, respectivamente - p>0,05). CONCLUSÕES: O uso sistemático da MRPA no ajuste da terapia anti-hipertensiva em pacientes em hemodiálise propiciou maior controle da PA no período interdialítico em comparação às medidas da PA pré-diálise. A MRPA pode ser usada como um instrumento adjuvante útil no controle da pressão arterial em pacientes em hemodiálise / INTRODUCTION: It is not known whether the adjustment of the antihypertensive therapy based on Home Blood Pressure Monitoring (HBPM) can improve blood pressure (BP) control in hemodialysis patients. OBJECTIVES: To compare the reduction in BP and in the left ventricular mass index (LVMI) obtained with the use of HBPM in relation to that achieved with predialysis BP measurements in hemodialysis patients. METHODS: Hypertensive patients on hemodialysis were randomized to have the antihypertensive therapy adjusted according two groups: control, based on the predialysis BP measurements, and intervention, based on HBPM. Before and after 06 months of follow-up, patients were submitted to Ambulatory Blood Pressure Monitoring (ABPM) for 24 hours, HBPM during one week and transthoracic echocardiogram. RESULTS: 34 and 31 patients completed the study in the intervention and control groups, respectively. The systolic (SBP) and diastolic (DBP) blood pressure in the interdialytic period by ABPM were significantly lower in the intervention group compared with the control group at the end of the study (mean 24-hours BP: 135 ± 13 mm Hg / 76 ± 7 mmHg versus 147 ± 15 mm Hg / 79 ± 8 mmHg, respectively - p <0.05). When the interdialytic BP was analysed by HBPM, the intervention group showed significant reduction only for the PAS in comparison with control group (mean weekly BP: 144 ± 21 mm Hg versus 154 ± 22 mm Hg, respectively - p <0.05). There were no differences between intervention and control groups in relation to LVMI at the end of the study (108 ± 36 g/m2 versus 110 ± 33 g/m2, respectively - p> 0.05). CONCLUSIONS: The systematic use of HBPM in the adjustment of antihypertensive therapy in patients on hemodialysis has led to better control of BP during interdialytic period compared to that achieved with the predialysis BP measurements. The HBPM can be used as a useful adjunct instrument to control blood pressure in hemodialysis patients