**Author details**

74 Practical Applications in Biomedical Engineering

same patient (trend analysis).

patients more effectively.

**Abbreviations** 

ALI: acute lung injury ApEn: approximate entropy AUC: area under the curve

CV: coefficient of variation ECG: electrocardiogram EEG: electroencephalogram FD: fractal dimension

FW: failure weaning HRV: heart rate variability ICU: intensive care unit LAA : low attenuation area LLE: largest lyapunov exponents LVEF: left ventricular ejection fraction

MSE : multiscale entropy MV: minute ventilation

PEF: peak expiratory flow

FFT: fast Fourier transformation

COPD: chronic obstructive pulmonary disease CPAP: continuous positive airway pressure

MODS: multiple organ dysfunction syndrome

PEEP: positive end-expiratory pressure

PET: positron emission tomography

aiding in the development of better and more accurate diagnostic or prognostic indices in cardiovascular diseases [16]. Furthermore, many important questions remain unanswered such as the value of single or longitudinal variability measurements for clinically useful information or its prognostic capability for risk stratification between patients or within the

In conclusion, we believe that the most important aspect of research on breathing pattern dynamics remains the development of international databases of various respiratory signals, with free access from different investigators, such as the Web site Physionet (www.physionet.org), which has boosted research on heart rate dynamics in cardio-vascular medicine [91]. We also think that in addition, such efforts must also be undertaken by pulmonary physicians and those who treat patients with severe respiratory diseases. In conclusion, we suggest that implementation of fractal analysis and breathing pattern variability and complexity measurements in respiratory physiology will result in better understanding of different and dynamic changes during various pathologic states, whereas its impact upon prediction of severe complications will add value to such methods. Clinicians must begin to understand basic principles of complex systems theory and support an interdisciplinary approach for understanding pulmonary diseases, in order to treat their

> Vasilios Papaioannou\* and Ioannis Pneumatikos *Democritus University of Thrace, Alexandroupolis Hospital, Intensive Care Unit, Alexandroupolis, Greece*
