Pathophysiology of Acid Base Balance Essay examples

6959 Words Jan 3rd, 2012 28 Pages
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,
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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
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