mass index (size); core temp, Systolic, diastolic, central venous pressure CVP (measured from the atrium by the third lumen simultaneously) and pulmonary artery pressure are input, a comprehensive flow vs pressure map can be calculated. In crude terms, this measurement compares left and right cardiac activity and calculates preload and afterload flow and pressures which, theoretically, can be stabilized or adjusted with drugs to either constrict or dilate the vessels (to raise or lower, respectively, the pressure of blood flowing to the lungs), in order to maximize oxygen for delivery to the body tissues. The ability to record results is not a guarantee of patient survivability. Pharmacotherapy lumina Modern catheters have multiple lumina — five or six are common — and have openings along the length to allow administration of inotropes and other drugs directly into the atrium. Drugs to achieve these changes can be delivered into the atrium via the fourth lumen, usually dedicated to medication. Common drugs used are various inotropes, norepinephrine or even atropine. A further set of calculations can be made by measuring the arterial blood and central venous (from the third lumen) and inputting these figures into a spreadsheet or the cardiac output computer, if so equipped, and plotting an oxygen delivery profile. SvO2 measurement One further development in recent years has been the invention of a catheter with a fiber-optic based probe which is extended and lodged into the ventricle wall providing instant readings of SvO2 or oxygen saturation of the ventricle tissues. This technique has a finite life as the sensor becomes coated with protein and it can irritate the ventricle via the contact area. Alternatives Various other techniques have largely relegated the PA catheter to history, e.g. the lithium dilution technique; the external bio-resistance monitor or the very simple and reliable technique of esophogeal doppler measurements of the descending aorta. Complications The procedure is not without risk, and complications can be life-threatening. It can lead to arrhythmias, pseudoaneurysm formation or rupture of the pulmonary artery, thrombosis, infection, pneumothorax, bleeding, and other problems. Controversy The benefit of the use of this type of catheter has been controversial. Therefore, many clinicians minimize its use. Evidence of benefit Several studies in the 1980s seemed to show a benefit of the increase in physiological information. Many reports showing benefit of the PA catheter are from anaesthetic, and Intensive Care Unit (ICU) settings. In these settings cardiovascular