Arterial blood gas analysis is used to assess and monitor patient acid-base status. Disturbance of acid-base balance is classified to one of four main types depending on the pH, pCO₂(a) and bicarbonate results generated during blood gas analysis; the four types are respiratory acidosis, respiratory alkalosis,...

ROC curves are frequently used to show in a graphical way the connection/trade-off between clinical sensitivity and specificity for every possible cut-off for a test or a combination of tests. In addition the area under the ROC curve gives an idea about the benefit of using the test(s) in question.  ROC curves are...

The process of patient sample testing, whether performed in the clinical laboratory or at the point of care, is the sum of three distinct phases. The first is the preanalytical phase, which includes test selection as well as sample collection and handling.  The second is the analytical or measuring phase that...

Increasing obesity is associated with worsening arterial blood gases (pO₂(a) and pCO₂(a)). That is the headline finding of a recent cross-sectional study of morbidly obese individuals with apparently normal lung function and no respiratory disease.  The study population comprised 114 women and 35 men with a mean (SD) ...

Hypokalemia, one of the most common electrolyte disturbances, is diagnosed if plasma potassium concentration is less than 3.5 mmol/L. Mild hypokalemia (plasma potassium 3.0-3.5 mmol/L) is usually asymptomatic, but greater degree of hypokalemia can result in signs and symptoms that reflect the fundamental role of...

Pulse oximetry provides the means for continuous non-invasive monitoring of blood oxygenation by measuring % oxygen saturation (SpO₂). This safe, easy and convenient method of monitoring oxygenation status is ubiquitous in clinical medicine and is now a routine part of the overall assessment and monitoring of all...

Mechanical ventilation is necessary for survival of patients with acute respiratory distress syndrome (ARDS). It was once supposed that ventilation should be adjusted to maintain pCO₂(a) within the normal range but this degree of mechanical ventilation can result in further damage to the lungs. Less aggressive (low...

Clinical laboratory measurement of serum/plasma creatinine concentration has been used to assess patient kidney function for well over 50 years.  With the incorporation of creatinine analyses to blood gas and other point-of-care platforms the test is now available outside the laboratory, at the bedside and in the...

The appropriate number of significant figures is important in order to have a meaningful level of resolving power when reporting analytical concentrations. Various methods or criteria can be used when estimating how many significant figures are needed. In most cases three significant figures (two true plus one...

If the results of a recent New Zealand study are representative, there is room for improvement in the quality of blood gas test result interpretation among emergency-room medical staff. A total of 80 emergency-room doctors (37 consultants and 43 emergency-medicine trainees) voluntarily submitted themselves for a...