what point(s) on the capnographic waveform represents) a mixture of alveolar gas and dead space gas

However, it does not correlate with the pressures obtained from an arterial catheter in critically ill patients, and the use of vasoactive agents and patient movements affect the result of measurements. There are several techniques, such as applanation tonometry, for example, the T-Line system (Tensys Medical, San Diego, CA, USA), which has shown similar accuracy in blood pressure measurement compared to the arterial catheter. One of the areas of recent progress in monitoring is the increasing availability of non-invasive methods. Although abovementioned devices have made it possible to improve the treatment of critically ill patients and optimize goal-directed therapy, they are expensive, not commonly available, and have shown limitations in providing reliable data in different contexts. These systems can provide information on the hemodynamic status of critically ill patients and can also be used in the perioperative setting. Other examples, using dilution methods, are the PiCCO system (Pulsion Medical System, Munich, Germany) and LiDCO system (LiDCO Ltd, London, United Kingdom). Data are obtained from the transpulmonary thermodilution method. More advanced examples are the VolumeView system (Edwards Lifesciences, Irvine, CA, USA), which requires cannulation of the femoral artery and a central venous catheter to provide information on cardiac function and volumetric data. They are based on the estimation of cardiac output through the analysis of the pulse wave contour, such as the FloTrac system (Edwards Lifesciences, Irvine, CA, USA) that requires arterial cannulation, providing information on blood pressure, cardiac function and probability of response to volume.

Nowadays, there are minimally invasive hemodynamic monitoring methods available. It is an expensive and invasive method with usefulness in various clinical conditions being a matter of debate. Monitoring based on the pulmonary artery cathe-ter is considered the gold standard for cardiac output (CO) assessment. Instead, cardiac output is the most important variable that determines tissue oxygen supply. Tissue perfusion does not necessarily correlate with arterial blood pressure. The aim is to achieve an adequate coupling between oxygen (O 2) supply and metabolic demands in an organism under surgical stress, thus preserving aerobic metabolism. Hemodynamic optimization is vital in high risk surgical patients.

What point(s) on the capnographic waveform represents) a mixture of alveolar gas and dead space gas