<P> The normal range for pH is 7.35--7.45 . As the pH decreases (<7.35), it implies acidosis, while if the pH increases (> 7.45) it implies alkalosis . In the context of arterial blood gases, the most common occurrence will be that of respiratory acidosis . Carbon dioxide is dissolved in the blood as carbonic acid, a weak acid; however, in large concentrations, it can affect the pH drastically . Whenever there is poor pulmonary ventilation, the carbon dioxide levels in the blood are expected to rise . This leads to a rise of carbonic acid, leading to a decrease in pH . The first buffer of pH will be the plasma proteins, since these can accept some H ions to try to maintain homeostasis . As carbon dioxide concentrations continue to increase (PaCO> 45 mmHg), a condition known as respiratory acidosis occurs . The body tries to maintain homeostasis by increasing the respiratory rate, a condition known as tachypnea . This allows much more carbon dioxide to escape the body through the lungs, thus increasing the pH by having less carbonic acid . If a patient is in a critical setting and intubated, one must increase the number of breaths mechanically . </P> <P> Respiratory alkalosis (Pa CO <35mmHg) occurs when there is too little carbon dioxide in the blood . This may be due to hyperventilation or else excessive breaths given via a mechanical ventilator in a critical care setting . The action to be taken is to calm the patient and try to reduce the number of breaths being taken to normalize the pH . The respiratory pathway tries to compensate for the change in pH in a matter of 2--4 hours . If this is not enough, the metabolic pathway takes place . </P> <P> Under normal conditions, the Henderson--Hasselbalch equation will give the blood pH </P> <Dl> <Dd> p H = 6.1 + log 10 ⁡ ((H C O 3 −) 0.03 × P a C O 2) (\ displaystyle pH = 6.1 + \ log _ (10) \ left ((\ frac ((HCO_ (3) ^ (-))) (0.03 \ times PaCO_ (2))) \ right)) </Dd> </Dl>

Partial pressure of carbon dioxide in arterial blood