Generality
Blood gas analysis, or arterial blood gas analysis, is a diagnostic test that allows the measurement of some important blood parameters, including circulating levels of oxygen and carbon dioxide, and blood pH.
Among the medical conditions for which the use of blood gas analysis is useful, include: pulmonary and respiratory diseases, kidney failure, heart failure, diabetes, nocturnal sleep illnesses, some types of infections, strokes to the head that affect respiratory capacity, drug overdose, etc.
Carried out in a medical-hospital center, blood gas analysis consists in taking a small sample of blood and in the subsequent laboratory analysis of the aforementioned sample.
Generally, the results of blood gas analysis are available to those who underwent it already after 10-15 minutes.
What is blood gas analysis?
Blood gas analysis is a diagnostic test that allows to measure three important parameters of an individual's blood: circulating oxygen levels, circulating carbon dioxide levels and pH (or acidity ). In other words, at the end of a blood gas analysis, the person who underwent it can know how much oxygen and carbon dioxide circulate in his blood and what the blood pH value is.
Blood gas analysis is also known as arterial blood gas analysis, since the measurement of the aforementioned parameters refers to the blood circulating in the arteries.
EMOGASANALYSIS MEASUREMENTS
Going into more detail, blood gas analysis makes it possible to measure:
- The partial pressure of oxygen . It is the pressure that oxygen would exert inside the lungs, if it were the only gas present. Its measurement provides indications on how effective the passage of oxygen contained in the inhaled air and into the innermost cavities of the lungs into the blood is.
- The partial pressure of carbon dioxide . It is the pressure that carbon dioxide exerts inside the lungs, if it were the only gas present. Its measurement provides indications on how effective the release of carbon dioxide from the human body.
- Blood pH . Measuring the pH of blood or another substance means calculating the amount of hydrogen ions (or H +) present inside. Under normal conditions, the pH of human blood is within a range of values that are 7.35 and 7.45.
A blood whose pH deviates from the normality values, resulting less than 7, is acid; vice versa, a blood whose pH is higher than the normality values is basic (or alkaline).
- Bicarbonate blood levels (HCO 3 ). Bicarbonate is a very important substance in keeping blood pH under control, preventing it from becoming too acidic or too basic.
- The blood oxygen content and oxygen saturation . By blood oxygen content, we mean how much oxygen is present in the blood.
Oxygen saturation, on the other hand, is a measure of how many oxygen molecules are linked to hemoglobin. Readers should be reminded that oxygen saturation values above 95% should be considered normal, while oxygen saturation values of 90% or less begin to become life-threatening.
uses
When the human being inhales, he introduces oxygen-rich air into the lungs. This air reaches particular pulmonary structures, called alveoli . Surrounded by a dense network of capillary vessels, in which circulates oxygen-poor blood but rich in carbon dioxide, the pulmonary alveoli have the task of taking oxygen from the air, exchanging it with the carbon dioxide of the blood.
In this way, the blood is oxygenated and is ready for the oxygenation of all the cells, tissues and organs of the human body.
The aforementioned exchange process, which involves the pulmonary alveoli and the blood, is called hematosis or gaseous exchange blood / alveoli .
Blood gas analysis is useful for doctors to understand the effectiveness of blood / alveoli gas exchange in an individual. In other words, blood gas analysis makes it possible to establish a person's ability to oxygenate the blood and free it from carbon dioxide.
INDICATIONS
In general, doctors subject subjects suspected of suffering from blood gases to blood gases
- Some pulmonary and / or respiratory disease, such as asthma, cystic fibrosis or chronic obstructive pulmonary disease;
- Kidney failure;
- Heart failure;
- Diabetes or some other metabolic disease;
- Some sleep sickness;
- Some serious infectious disease.
Furthermore, blood gas analysis is used in the diagnosis of injuries to the neck or head that affect the respiratory capacity of the victim, in the diagnosis of drug overdose, in the evaluation of a treatment for a given lung disease and in the estimation of how effective ventilation is mechanical (clearly in the subjects who are subjected to this remedy).
All the aforementioned medical conditions (pulmonary and / or respiratory diseases, kidney failure etc.), for which a blood gas analysis has a certain diagnostic value, have in common the fact of altering the blood levels of oxygen and carbon dioxide or the values pH blood vessels.
The symptoms in which doctors tend to resort to blood gas analysis:
- Dyspnoea
- Breathing difficulties
- Confusion
- Nausea
SOME NOTES ON EMOGASANALYSIS USE
Blood gas analysis is a procedure that alone cannot accurately diagnose the present medical condition. In fact, it does not allow to establish whether the anomalies detected are due to a heart problem, a lung problem, etc.
This limit makes the use of more in-depth and more specific diagnostic tests indispensable.
Preparation
Before carrying out blood gas analysis, doctors investigate whether patients who will undergo the diagnostic examination:
- They have some kind of coagulation disease or they take anticoagulants, including aspirin or warfarin;
- They take medicines of a different type than anticoagulants;
- They suffer from some drug allergy, especially anesthetic drugs.
Except for these three warnings, blood gas analysis is a fairly simple procedure that requires no special preparation.
Clearly, for any further information concerning the procedure, it is sufficient to consult the attending physician, who is at the complete disposal of patients who have doubts or questions.
Procedure
Carried out in a medical-hospital center, blood gas analysis consists in taking a blood sample, from the patient under examination, and in the subsequent laboratory analysis of the aforementioned sample.
The collection can take place in three different anatomical points, therefore from three different arteries. The arteries from which the blood sample can be taken for blood gas analysis are: the radial artery, the brachial artery and the femoral artery . The withdrawal from the radial artery takes place in the wrist; the removal from the brachial artery is located in the arms, to be exact in the anterior bend of the elbow; finally, the extraction from the femoral artery takes place at the level of the groin.
THE LEVY IN DETAILS
The withdrawal phase can be divided into at least 5 steps:
- First step → involves the sterilization, by means of alcohol, of the needle for collection and the anatomical site of collection. In the presence of patients who are particularly sensitive to pain, it also includes the injection of a local anesthetic, at the site where the needle is introduced, in order to make the entire withdrawal operation less annoying.
- Second step → consists of inserting the needle into the sampling site.
- Third step → it involves taking blood, using a syringe applied to the needle previously inserted in the sampling site. Generally, doctors advise patients to breathe normally during this important step of the procedure.
- Fourth step → consists in extracting the needle and applying a small piece of cotton, where the blood has been taken. The piece of cotton helps to stop any blood loss.
- Fifth step → foresees the bandaging of the picking site and the application of a digital pressure on the same site for 5-10 minutes. Digital pressure reduces the risk of bleeding and is particularly important for people who have some coagulation disease or who take drugs that make their blood more fluid (anticoagulants).
SENSATIONS DURING THE PROCEDURE
Blood drawing from an artery is more painful than drawing blood from a vein, as the arteries generally reside deeper than the venous vessels, and are surrounded by nerves.
Most patients who undergo blood gas analysis without resorting to local anesthesia experience an acute painful sensation when inserting the needle and, above all, at the time of collection. Thanks to local anesthesia, pain is drastically reduced: patients, in fact, experience a sensation comparable to the annoyance of a pinch or an insect bite.
The painful sensation felt during a blood gas analysis also depends on how sensitive a person is to pain. This means that a person with a high tolerance of pain suffers less when inserting the needle and at the time of collection.
LABORATORY ANALYSIS
Laboratory analyzes of the blood sample begin immediately after the end of the collection.
Generally, they are available to patients after only 10-15 minutes.
Post-procedural phase
Patients undergoing blood gas analysis can return home as soon as the procedure is completed. However, this occurs very rarely, since, in most cases, subjects who have carried out a blood gas analysis suffer from a medical condition of a certain clinical relevance, which requires immediate treatment.
Risks and complications
Blood gas analysis is considered a low-risk procedure, as it is minimally invasive and involves taking a small amount of blood.
POSSIBLE SIDE EFFECTS
Possible side effects of blood gas analysis include:
- Bleeding from the blood collection site. If the patient takes anticoagulant drugs or has some coagulation disease, the possibility of bleeding increases
- Occurrence of a hematoma at the blood collection site. To reduce the risk of hematoma, doctors advise applying a slight pressure with the finger, at the site where the needle is inserted, for at least 10 minutes;
- Feeling faint, vertigo and / or nausea, at the time of taking the blood sample;
- Development of an infection at the site of needle insertion, for blood collection;
- Damage to a neighboring nerve to the artery for harvesting or damage to the artery itself. These are two side effects that occur very rarely.
Results
The doctors compare what results from the blood gas analysis with a series of references, which correspond to normality. It should be noted that the reference values vary in relation to the geographical location, to be exact depend on the sea level. To simplify the above, the reference values for an individual who lives and has taken the exam in a geographical area above sea level are different from the reference values for an individual who lives and has taken the exam in an area of mountain (therefore not at sea level).
| Table of reference values for an adult individual who lives in a geographical area above sea level | |
| Partial pressure of oxygen | Above 80 mmHg |
| Partial pressure of carbon dioxide | 35-45 mmHg |
| pH | 7.35-7.45 |
| Bicarbonate concentration | 22-26 mEq / L (22-26 mmol / L) |
| Oxygen content | 15-22 mL per 100 mL of blood (6.6-9.7 mmol / L) |
| Oxygen saturation | 95% -100% |
* Note: the reference values for a child living in a geographical area above sea level are different, compared to those of an adult individual.
WHAT CAN RESULT IN RESULTS
Several conditions can alter the results of a blood gas analysis, including:
- The presence of fever or hypothermia;
- The presence of diseases that affect the transport of oxygen by red blood cells; the diseases in question include anemia and polycythemia;
- Having smoked or breathed in passive smoke, carbon monoxide or paints just before blood gas analysis.
