From the Guidelines
To measure the validity of pH, wireless pH monitoring should be undertaken for at least 48 hours, as this increases the number of patients found to have excess acid exposure and the number of symptoms available for symptom association analysis. This approach is supported by the British Society of Gastroenterology guidelines for oesophageal manometry and oesophageal reflux monitoring, which recommends a minimum of 48 hours of wireless pH monitoring 1.
When measuring pH, it is essential to consider the following key points:
- Calibration of the pH meter using standard buffer solutions
- Proper maintenance and cleaning of the electrode
- Accurate temperature compensation
- Correct measurement technique, including rinsing the electrode with distilled water between samples and allowing the reading to stabilize
- Regular verification of measurements using a known standard solution as a control
However, in the context of oesophageal pH monitoring, automatic analysis of oesophageal pH recordings and symptom association with acid reflux episodes is adequate for pH monitoring in patients, provided the recording is checked for artefacts and major technical issues, and that times of meals and symptoms have been accurately recorded 1. This approach can help ensure the validity of pH measurements and provide accurate results for clinical purposes.
It is crucial to note that the validity of pH measurements depends on various factors, including proper calibration, electrode condition, and measurement technique 1. By following these guidelines and recommendations, healthcare professionals can ensure accurate and reliable pH measurements, which is essential for diagnosing and managing various medical conditions.
From the Research
Measuring Validity of pH
To measure the validity of pH, several steps and calculations can be employed, including:
- Determination of the serum pH 2, 3
- Calculation of the serum anion gap to identify metabolic acidosis and distinguish between anion gap and non-anion gap acidosis 4, 5, 2, 3
- Estimation of the degree of compensation 2
- Calculation of the excess anion gap 2
- Evaluation of respiratory or metabolic compensation 3
- Measurement of urine anion gap and osmolal gap for further analysis 3
Calculation of Anion Gap
The anion gap is calculated as the difference between the sum of sodium and potassium ions and the sum of chloride and bicarbonate ions. An increased anion gap indicates the presence of unmeasured anions, which can be seen in various acid-base disorders 4, 5.
- The anion gap can be used to identify errors in the measurement of electrolytes and detect paraproteins 5
- The type of retained anion can affect the magnitude of the increase in anion gap relative to change in serum bicarbonate 5
Limitations and Effectiveness
The effectiveness of the anion gap in identifying acid-base disorders can be limited by various factors, including: