An important part of being healthy is for the blood to maintain a normal degree of acidity or alkalinity. The acidity or alkalinity of any solution, including blood, is indicated on the pH scale. The pH scale, ranges from 0 (strongly acidic) to 14 (strongly basic or alkaline). A pH of 7.0, in the middle of this scale, is neutral. Blood is normally slightly basic, with a normal pH range of about 7.35 to 7.45. Usually the body maintains the pH of blood close to 7.40.
A doctor evaluates a person's acid-base balance by measuring the pH and levels of carbon dioxide (an acid) and bicarbonate (a base) in the blood.
Blood acidity increases when the
Level of acidic compounds in the body rises (through increased intake or production, or decreased elimination)
Level of basic (alkaline) compounds in the body falls (through decreased intake or production, or increased elimination)
Blood alkalinity increases when the level of acid in the body decreases or when the level of base increases.
Control of Acid-Base Balance
The body's balance between acidity and alkalinity is referred to as acid-base balance.
The blood's acid-base balance is precisely controlled because even a minor deviation from the normal range can severely affect many organs. The body uses different mechanisms to control the blood's acid-base balance. These mechanisms involve the
Lungs
Kidneys
Buffer systems
Role of the lungs
One mechanism the body uses to control blood pH involves the release of carbon dioxide from the lungs. Carbon dioxide, which is mildly acidic, is a waste product of the processing (metabolism) of oxygen and nutrients (which all cells need) and, as such, is constantly produced by cells. It then passes from the cells into the blood. The blood carries carbon dioxide to the lungs, where it is exhaled. As carbon dioxide accumulates in the blood, the pH of the blood decreases (acidity increases).
The brain regulates the amount of carbon dioxide that is exhaled by controlling the speed and depth of breathing (ventilation). The amount of carbon dioxide exhaled, and consequently the pH of the blood, increases as breathing becomes faster and deeper. By adjusting the speed and depth of breathing, the brain and lungs are able to regulate the blood pH minute by minute.
Role of the kidneys
The kidneys are able to affect blood pH by excreting excess acids or bases. The kidneys have some ability to alter the amount of acid or base that is excreted, but because the kidneys make these adjustments more slowly than the lungs do, this compensation generally takes several days.
Buffer systems
Yet another mechanism for controlling blood pH involves the use of chemical buffer systems, which guard against sudden shifts in acidity and alkalinity. The pH buffer systems are combinations of the body's own naturally occurring weak acids and weak bases. These weak acids and bases exist in pairs that are in balance under normal pH conditions. The pH buffer systems work chemically to minimize changes in the pH of a solution by adjusting the proportion of acid and base.
The most important pH buffer system in the blood involves carbonic acid (a weak acid formed from the carbon dioxide dissolved in blood) and bicarbonate ions (the corresponding weak base).
Types of Acid-Base Disorders
There are two abnormalities of acid-base balance:
Acidosis: The blood has too much acid (or too little base), resulting in a decrease in blood pH.
Alkalosis: The blood has too much base (or too little acid), resulting in an increase in blood pH.
Acidosis and alkalosis are not diseases but rather are the result of a wide variety of disorders. The presence of acidosis or alkalosis provides an important clue to doctors that a serious problem exists.
Types of acidosis and alkalosis
Acidosis and alkalosis are categorized depending on their primary cause as
Metabolic acidosis and metabolic alkalosis are caused by an imbalance in the production of acids or bases and their excretion by the kidneys.
Respiratory acidosis and respiratory alkalosis are caused by changes in carbon dioxide exhalation due to lung or breathing disorders.
People can have more than one acid-base disorder.
Compensation for acid-base disorders
Each acid-base disturbance provokes automatic compensatory mechanisms that push the blood pH back toward normal. In general, the respiratory system compensates for metabolic disturbances while metabolic mechanisms compensate for respiratory disturbances.
At first, the compensatory mechanisms may restore the pH close to normal. Thus, if the blood pH has changed significantly, it means that the body's ability to compensate is failing. In such cases, doctors urgently search for and treat the underlying cause of the acid-base disturbance.
Acid-Base Disturbances and the Body's Response
FAQs
Usually the body maintains the pH of blood close to 7.40. A doctor evaluates a person's acid-base balance by measuring the pH and levels of carbon dioxide (an acid) and bicarbonate (a base) in the blood. Blood alkalinity increases when the level of acid in the body decreases or when the level of base increases.
What is the acid-base balance summary? ›
Acid–base balance refers to the balance between input (intake and production) and output (elimination) of hydrogen ion. The body is an open system in equilibrium with the alveolar air where the partial pressure of carbon dioxide pCO2 is identical to the carbon dioxide tension in the blood.
What are the 4 types of acid-base balance? ›
There are four simple acid base disorders: (1) Metabolic acidosis, (2) respiratory acidosis, (3) metabolic alkalosis, and (4) respiratory alkalosis. Metabolic acidosis is the most common disorder encountered in clinical practice.
What is the acid-base balance guideline? ›
To maintain homeostasis, the human body employs many physiological adaptations. One of these is maintaining an acid-base balance. In the absence of pathological states, the pH of the human body ranges between 7.35 to 7.45, with the average at 7.40.
What is the acid-base imbalance and balance? ›
There are two abnormalities of acid-base balance: Acidosis: The blood has too much acid (or too little base), resulting in a decrease in blood pH. Alkalosis: The blood has too much base (or too little acid), resulting in an increase in blood pH.
What is the acid-base theory summary? ›
Acids and bases can be defined via three different theories. The Arrhenius theory of acids and bases states that “an acid generates H+ ions in a solution whereas a base produces an OH– ion in its solution”. The Bronsted-Lowry theory defines “an acid as a proton donor and a base as a proton acceptor”.
How do you analyze acid-base balance? ›
When required to make a proper approach towards the evaluation of blood gas and acid–base disturbances in the body, the following scheme is suggested:
- Look at pH - < 7.40 - Acidosis; > 7.40 - Alkalosis.
- If pH indicates acidosis, then look at paCO2and HCO3-
- If paCO2is ↑, then it is primary respiratory acidosis.
Acid–base balance. The pH of the extracellular fluid, including the blood plasma, is normally tightly regulated between 7.32 and 7.42 by the chemical buffers, the respiratory system, and the renal system.
What are the two main ways to maintain acid-base balance? ›
The kidneys have two main ways to maintain acid-base balance: their cells reabsorb bicarbonate HCO3− from the urine back to the blood and they secrete hydrogen (H+) ions into the urine. By adjusting the amounts reabsorbed and secreted, they balance the bloodstream's pH.
What happens if your body is too alkaline? ›
If the body becomes too alkaline, it increases carbon dioxide in the lungs through hypoventilation, or decreased breathing. The body can also increase or decrease bicarbonate levels in the blood by increasing or decreasing breathing rate. The kidneys work to increase the elimination of bicarbonate through urine.
What are the signs of metabolic acidosis?
- Accelerated heartbeat (tachycardia).
- Confusion or dizziness.
- Feeling very tired (fatigue).
- Loss of appetite.
- Headache.
- Rapid breathing or long, deep breathing.
- Nausea and vomiting.
- Feeling weak.
The kidneys have the predominant role in regulating the systemic bicarbonate concentration and hence, the metabolic component of acid-base balance.
How do you monitor acid-base balance? ›
To determine a patient's acid–base balance, the physician needs to monitor the pH and the levels of carbon dioxide and bicarbonate in the blood.
What is the basic concept of acid-base balance? ›
Usually the body maintains the pH of blood close to 7.40. A doctor evaluates a person's acid-base balance by measuring the pH and levels of carbon dioxide (an acid) and bicarbonate (a base) in the blood. Blood alkalinity increases when the level of acid in the body decreases or when the level of base increases.
What are the diseases related to acid-base balance? ›
Examples include vomiting (metabolic alkalosis), diarrhea (metabolic acidosis), chronic obstructive pulmonary disease (respiratory acidosis), pneumonia (respiratory alkalosis), and so on.
What happens when acid-base balance is disturbed? ›
The body adapts, or compensates where there is an acid-base disturbance in an attempt to maintain homeostasis7. If the primary acid-base problem is metabolic, then the compensatory mechanism is respiratory.
What is the summary of acids and bases? ›
Key Points. An acid is a substance that donates protons (in the Brønsted-Lowry definition) or accepts a pair of valence electrons to form a bond (in the Lewis definition). A base is a substance that can accept protons or donate a pair of valence electrons to form a bond.
What is an acid-base indicator summary? ›
Acid-base indicators are chemicals used to determine whether an aqueous solution is acidic, neutral, or alkaline. Since acidity and alkalinity relate to pH, they may also be known as pH indicators.
What is the balance of acids and bases? ›
The pH scale, ranges from 0 (strongly acidic) to 14 (strongly basic or alkaline). A pH of 7.0, in the middle of this scale, is neutral. Blood is normally slightly basic, with a normal pH range of about 7.35 to 7.45. Usually the body maintains the pH of blood close to 7.40.
What are the conclusions of acid-base balance? ›
Conclusions: In man the acid-base balance is maintained and regulated by the renal and respiratory systems, which modify the extracellular fluid pH by changing the bicarbonate pair (HCO3- and PCO2); all other body buffer systems adjust to the alterations in this pair.
