Related Experiment Video
Updated: Aug 4, 2026
06:47
Measurement and Analysis of Extracellular Acid Production to Determine Glycolytic Rate
Published on: December 12, 2015
Human PaCO2 and standard base excess compensation for acid-base imbalance
R Schlichtig1, A W Grogono, J W Severinghaus
1Department of Research and Development, Pittsburgh Veterans Affairs Medical Center, PA, USA.
Critical Care Medicine
|July 22, 1998
Summary
Standard base excess (SBE) simplifies acid-base balance analysis by decoupling respiratory and metabolic factors. This method offers a clearer understanding of how the body compensates for imbalances.
Area of Science:
- Physiology
- Biochemistry
- Medical Science
Background:
- Renal and respiratory systems dynamically regulate acid-base balance.
- Traditional analysis using pH, PaCO2, and HCO3- can be complex due to interdependencies.
- Standard base excess (SBE) offers a method to quantify metabolic balance independently of PaCO2.
Purpose of the Study:
- To simplify the characterization of acid-base compensation.
- To express compensatory mechanisms in terms of standard base excess (SBE) and PaCO2.
- To establish independent variables for metabolic and respiratory contributions to acid-base status.
Main Methods:
- Meta-analysis of 21 published reports on acid-base imbalance.
- Historical data synthesis via the Internet.
- Calculation of compensatory responses using SBE and PaCO2, expressed as deviations from normal values.
Main Results:
- Developed equations for compensatory changes: Chronic deltaSBE = 0.4 x deltaPaCO2.
- Established respiratory compensation equations: Acidosis deltaPaCO2 = 1.0 x deltaSBE, Alkalosis deltaPaCO2 = 0.6 x deltaSBE.
- Demonstrated that patient compensatory changes align with these SBE- and PaCO2-based equations.
Conclusions:
- Acid-base compensation can be effectively described using independent respiratory (PaCO2) and metabolic (SBE) variables.
- Findings are based on data from numerous investigators over 35 years.
- The SBE approach provides a simplified and independent method for assessing acid-base status.
Related Concept Videos
01:31pH Homeostasis
Acid-base homeostasis is essential for maintaining normal physiological activities in humans. The pH of various body fluids is strictly regulated because it is critical for the optimal activity of enzymes involved in metabolic reactions. Enzymes are basically proteins, so, any significant change in pH can affect their structure and activity. In humans, pH is regulated using three primary mechanisms— chemical buffer systems, respiratory regulation, and renal regulation.
Respiratory Regulation of...
Respiratory Regulation of...
01:25Acid-Base Balance
The human body maintains a narrow pH range regulated through acid-base balance. This balance is crucial as changes in the hydrogen ion concentration can disrupt cell membrane stability, alter protein structures, and change enzyme activities. The normal pH of arterial blood is 7.4, venous blood and interstitial fluid is 7.35, and intracellular fluid averages 7.0.
When the pH of arterial blood rises above 7.45, it results in a condition called alkalosis. Conversely, a drop below 7.35 leads to...
When the pH of arterial blood rises above 7.45, it results in a condition called alkalosis. Conversely, a drop below 7.35 leads to...
01:18Respiratory Regulation of Acid-Base Balance
Respiratory compensation is a vital physiological process that stabilizes blood plasma pH by regulating the partial pressure of carbon dioxide (PCO2), a key determinant of pH levels. Most carbon dioxide in the blood dissolves and converts into carbonic acid (H2CO3). It dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3⁻). There is also an inverse relationship between PCO2 and pH.
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are produced, leading to a...
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are produced, leading to a...
01:29Disorders of Acid-Base Balance
The human body maintains a precise pH range of arterial blood between 7.35 and 7.45. Deviations result in either acidosis (pH < 7.35) or alkalosis (pH > 7.45). These conditions are further classified as respiratory or metabolic disorders based on their underlying cause.
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
01:28Compensation Mechanisms
The human body employs intricate mechanisms to counteract changes in blood pH, preventing conditions like acidosis (pH < 7.35) and alkalosis (pH > 7.45). These compensatory responses aim to restore normal arterial blood pH by engaging respiratory or renal systems, depending on the source of the imbalance.
Respiratory Compensation
This mechanism addresses metabolic-induced pH imbalances by adjusting breathing rates. Respiratory compensation begins within minutes of detecting a pH...
Respiratory Compensation
This mechanism addresses metabolic-induced pH imbalances by adjusting breathing rates. Respiratory compensation begins within minutes of detecting a pH...
01:24Diagnosing Acidosis and Alkalosis
Diagnosing acid-base imbalances involves systematically analyzing arterial blood samples, focusing on three key measurements: pH, bicarbonate (HCO3−) concentration, and carbon dioxide partial pressure (PCO2). This analysis follows a four-step process that helps identify the imbalance's underlying cause and nature.
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2 and HCO3− values are examined to...
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2 and HCO3− values are examined to...