Intensive and Critical Care Nursing (2008) 24, 28—40 ORIGINAL ARTICLE Pathophysiology of acid base balance: The theory practice relationship Sharon L. Edwards ∗ Buckinghamshire Chilterns University College, Chalfont Campus, Newland Park, Gorelands Lane, Chalfont St. Giles, Buckinghamshire HP8 4AD, United Kingdom Accepted 13 May 2007 KEYWORDS Acid base balance; Arterial blood gases; Acidosis; Alkalosis Summary There are many disorders/diseases that lead to changes in acid base balance. These conditions are not rare or uncommon in clinical practice, but everyday occurrences on the ward or in critical care. Conditions such as asthma, chronic obstructive pulmonary disease (bronchitis or emphasaemia), diabetic ketoacidosis, …show more content…
High alveolar ventilation brings more O2 into the alveoli, increasing O2 , and rapidly eliminating CO2 from the lungs (for chemical abbreviations see Table 2). Partial pressure of gases Dalton’s law explains the partial pressure of a gas, which is the pressure exerted by a gas within a mixture of gases independent of each gas in the mixture (Marieb, 2004). The partial pressure of each gas is directly proportional to its percentage in the total mixture and in air is determined by atmospheric pressure. Atmospheric pressure is 101 kPa (760 mmHg), 21% of this air is oxygen, and the partial pressure of oxygen (PO2 ) in atmospheric air is: 21 × 101 = 21.2 kPa 100 Within the alveoli the PO2 is different to air because of enrichment in the air passages (dead space) with CO2 and water vapour. Alveolar air contains much more CO2 and water vapour and much less O2 and so makes a greater contribution to the near-atmospheric pressure in the lungs, then they do in air. This is due to: • gas exchanges occurring in the lungs, • humidification of air by the conducting passages, • mixing of gases in the dead space (contains air not involved in gaseous exchange) between the nose and alveoli. In alveoli, PO2 averages only 13.2 kPa (100 mmHg). Continuous consumption of O2 and production of CO2 in the cells means that there is a partial pressure gradient both in the lungs and at the tissue level
The features that lungs have that allow for efficient gas exchange are that the lungs are thin, moist and well supplied with blood.
Oxygen is drawn into the lungs by a process called inhalation, (breathing in), which occurs when the diaphragm and intercostal muscles are contracted which causes the lungs to expand, giving a larger volume and therefore causing a lower pressure differential between the lungs, alveolar pressure, and the outside atmosphere. This inverse relationship between volume and pressure is called Boyle’s law. (Tortora & Derrickson, 2011)
The presence of fluid in the alveolar space could potentially cause the lung capacity to be effected as well.
The respiratory system is a complex organ structure of the human body anatomy, and the primary purpose of this system is to supply the blood with oxygen in order for the blood vessels to carry the precious gaseous element to all parts of the body to accomplish cell respiration. The respiratory system completes this important function of breathing throughout inspiration. In the breathing process inhaling oxygen is essential for cells to metabolize nutrients and carry out some other tasks, but it must occur simultaneously with exhaling when the carbon dioxide is excreted, this exchange of gases is the respiratory system's means of getting oxygen to the blood (McGowan, Jefferies & Turley, 2004).
Small air sacks called alveoli are at the tips of the bronchioles. When air reaches them, the oxygen concentration is high, which causes diffusion into red blood cells travelling through pulmonary capillaries (7). The red blood cells then distribute the new oxygen to the rest of the body. When they reach the alveoli again, they exchange carbon dioxide (a form of cell waste) for new oxygen, and repeat the process. The carbon dioxide is moved through the bronchioles, bronchi, and trachea in the form of exhalation.
The respiratory system is responsible for supplying the body with oxygen and removing carbon dioxide. Respiration allows this gas exchange to occur in the lungs. While respiration can be observed as a physical process, the chemical process provides the body’s cells with adequate amounts of energy, which is produced by the breakdown of ATP (VanPutte, 2014). In order for the cells to obtain this energy, the respiratory system goes through a process called pulmonary ventilation, or breathing. The two concepts involved in pulmonary ventilation are an inspiration, air flowing into the lungs, and expiration, air forced out of the lungs.
The alveoli provide a large surface area in the lungs as they are very small, they are highly folded and there are a large amount of them in the lungs. In both the lungs of an adult there are around 300 million alveoli. If the alveoli were to be flattened out the surface area would be around 70 metres squared. The alveoli are well adapted as we require a lot of oxygen to respire at an efficient metabolic rate. This also means that we can transfer carbon dioxide out of our body at an efficient rate so a large amount doesn't stay in our blood as it is very harmful.
Due to the lack of insulin patients with type I diabetes are unable to use glucose as their primary energy source, as a result their body switches to fat metabolism as its source of energy. As a result acidic ketones are produced as metabolic byproduct, this can be directly detected as a decrease in pH on ABG analysis. Patients with moderate to severe DKA have a blood pH ranging from 6.9-7.2, lowered bicarbonate levels and a carbon dioxide partial pressure in the rage of 15-20mmHg. The the cause of our patient her partial pressure of carbon dioxide was 15mmHg, bicarbonate was low and a blood pH of 7.14, these values suggest that the patient has metabolic acidosis and that the diagnosis of DKA is likely correct. While ABG analysis can be used to diagnose DKA several studies suggest that the ABG test results rarely effect a physicians diagnosis, treatment and management of the condition (3). In addition the same studies have shown that the pH venous of venous blood was precise enough to serve as a substitute to arterial pH analysis and is less painful for the patient
The possible causes of this acid base imbalance are the vomiting and the overuse of antacids. As the name implies it is bicarbonate which has been added to the body. The vomiting reduces the extracellular fluid and this in turn leads to a release of angiotensin and aldersterone. This release then increases the bicarbonate absorption and increased hydrogen ion and potassium excreted. This patient may also have hypokalemia which is very common in metabolic alkalosis and would need to be replaced if it occurred ( Thomas, 2015). The respiratory rate would also slow to try and compensate for the alkalosis.
The respiratory system is the process responsible for the transportation and exchange of gases into and out of the human body. As we breath in, oxygen in the air containing oxygen is drawn into the lungs through a series of air pipes known as the airway and into the lungs. As air is drawn into the lungs and waste gas excreted, it passes through the airway, first through the mouth or nose and through the pharynx, larynx and windpipe – also known as the trachea. At this point it then enters the lungs through the bronchi before finally reaching the air sacs known as alveoli. Within the lungs, through a process known as diffusion, the oxygen is transferred to the blood stream through the alveoli (air ducts) where it is then transported inside
Emphysema is a disease which specifically targets the alveoli, or air sacs. According to the Cleveland Clinic, “there are about three hundreds million alveoli in normal lungs.”[3] The alveoli are very necessary for the body because they suck the oxygen from air and rid carbon dioxide out of the body, and they important for connections between the respiratory system and circulatory system, or blood vessels. In emphysema, the alveoli more gradually damaged and rupture. Additionally, the weakness the inner wall of alveoli, which made one larger air space rather of many tiny ones. As a result, the alveoli can not shrink and expand probably as usual. Moreover, this damage leads to reduced the surface of the lungs. Therefore, the amount of oxygen
Respiratory acidosis is when the lungs are unable to remove the normal amount of carbon dioxide as the body produces it. This leads to an increase in PaCO2 (hypercapnia) which lowers HCO3. The blood becomes too acidic because of the excess amount of CO2. The average range for PaCO2 is 35-45m Hg. Respiratory acidosis is caused by an issue with the lungs ability to remove CO2 properly, a form of lung disease. Most causes are asthma, neuromuscular disorders, obesity and COPD. The lungs and the kidneys regulate the body’s pH. Lungs remove CO2 and the kidneys remove acid through the urine. Treatment would include bronchodilator drugs to open airways, oxygen therapy and a breathing machine might be prescribed. A person that is much older is more likely to develop this type of disease since the strength of the kidneys and lungs has weekend with age. Also certain medications can affect the pH balance of the body.
Hyperventilation is a rapid breathing, an increased in alveolar ventilation and decrease in metabolism. It occur when greater amount of carbon dioxide are removed from the blood stream than the body can produce, meaning more carbon dioxide been breath out (Bell & Rhoades, 2012). As shown in the result (figure 1, 2 & table 1), hyperventilation compare to normal breathing increase mean PO2 and Hb-O2 saturation, decrease mean PCO2. This is because when alveoli ventilation double, metabolic CO2 decrease, PCO2 will be lower than normal. PO2 have the opposite effect. During hyperventilation, more fresh oxygen is delivered to the alveoli than the blood, as a result this will increase PO2 in the blood (Sherwood, 2013). PO2 had increase rapidly because
This also affects the pressure gradient from the lungs to
If an acid-base disturbance shifts the pH outside of the physiologic range, various control measures are activated to resist the change in pH. Compensatory mechanisms try to preserve the normal 20:1 ratio of bicarbonate to carbonic acid to keep the pH at normal range. The body works to maintain normal ratios through a compensation mechanism using renal and respiratory methods (Crowley, 2010).