Self monitoring versus ambulatory blood pressure monitoring]

Blood pressure is a variable parameter for which the isolated determination cannot be considered as a characteristic of the subject. Therefore, the clinical measurement of blood pressure constitutes the method of reference but presents limits and causes of errors which pose a problem for its validity in evaluating the average blood pressure level in certain patients. In order to overcome the limits of occasional measurement, different methods of blood pressure measurement have been proposed. Among these methods, self monitoring of blood pressure by the patient and 24 hour ambulatory blood pressure monitoring (ABPM) are the most used. Each of these methods presents advantages and disadvantages, indications and limits of use. The information obtained by each of them is of a different nature: these methods are not substitutes but are complementary. Self monitoring and ABPM seem to evaluate the pressure load better than clinical monitoring and are better correlated to the organic effects of hypertension and thus the cardiovascular morbidity and mortality, ABPM in particular. However, it remains to be clarified whether the use of these methods in the evaluation of cardiovascular risk and the therapeutic management of the hypertensive can improve the long term cardiovascular prognosis.     

Respiratory monitoring

The ability to accurately assess respiratory function is essential in the management of critically sick patients. Such measurements help in the diagnosis, management, and outcome of the patients. Proper understanding and interpretation of these parameters is of paramount importance. Clinicians should appreciate the benefits and the limitations of these techniques.     

Cardiac output monitoring

Minimally invasive and non-invasive methods of estimation of cardiac output (CO) were developed to overcome the limitations of invasive nature of pulmonary artery catheterization (PAC) and direct Fick method used for the measurement of stroke volume (SV). The important minimally invasive techniques available are: oesophageal Doppler monitoring (ODM), the derivative Fick method (using partial carbon dioxide (CO2 ) breathing), transpulmonary thermodilution, lithium indicator dilution, pulse contour and pulse power analysis. Impedance cardiography is probably the only non-invasive technique in true sense. It provides information about haemodynamic status without the risk, cost and skill associated with the other invasive or minimally invasive techniques. It is important to understand what is really being measured and what assumptions and calculations have been incorporated with respect to a monitoring device. Understanding the basic principles of the above techniques as well as their advantages and limitations may be useful. In addition, the clinical validation of new techniques is necessary to convince that these new tools provide reliable measurements. In this review the physics behind the working of ODM, partial CO2 breathing, transpulmonary thermodilution and lithium dilution techniques are dealt with. The physical and the physiological aspects underlying the pulse contour and pulse power analyses, various pulse contour techniques, their development, advantages and limitations are also covered. The principle of thoracic bioimpedance along with computation of CO from changes in thoracic impedance is explained. The purpose of the review is to help us minimize the dogmatic nature of practice favouring one technique or the other.     

Cardiac events monitoring

Cardiac events recorders have been developed in order to record the heart rhythm during symptoms such as palpitations or presyncope, to first make a diagnosis, and subsequently drive the treatment strategy. In other circumstances, they can be also used in asymptomatic patients (to record silent atrial fibrillation for instance). Because they are non-invasive, potentially cost-saving and relatively easy to use, the external rhythm recording devices have shown some great advances in the last years, spreading from photoplethysmographic technique to real ECG reconstruction. Technological advances in the field of microelectronics, as well as in the field of data transmission have contributed to their widespread use in cardiology. The trend for miniaturization was also expanded to the implantable recorders. This paper will review will review advantages and limitations of the different existing available well-established recording devices, as well as the last technological developments in terms of ECG recordings.     

Esophageal pH monitoring

In the 25 years since it was first described, prolonged esophageal pH monitoring has gained increasing acceptance and popularity as a diagnostic and research technique in GER disease. Some recent developments that have contributed to its attraction include compact portable recorders, computerized analysis, short monitoring periods, the good discriminant value of the simple measurement of percent monitoring time that pH is less than 4, and the symptom index, allowing correlation of symptoms with reflux events. Nevertheless, there remain areas of uncertainty with regard to reproducibility and the conditions of monitoring, in particular whether strict dietary control and controlled activity and posture are necessary. There is no universally accepted normal range of values, but it is now apparent that normal and abnormal GER are not appropriately differentiated by simply defining the upper limit of normal using a formula of the mean plus two standard deviations, so other statistical techniques have emerged. Indications for the technique include atypical symptoms, particularly noncardiac chest pain, respiratory symptoms, and, in young children, apneic attacks and recurrent vomiting associated with failure to thrive. The technique is having an impact on the assessment prior to, during, and after medical and surgical therapy for GER, as well as in helping to unravel the complexities of the pathogenesis of esophagitis.