There must be a pressure gradient for oxygen and carbon dioxide to be exchanged. When blood comes into the lung and the alveoli, the pressure of O₂ is higher in the alveoli than the blood. It will diffuse across the walls of the alveoli into the blood. Simultaneously, the concentration of CO₂ is higher in the blood than in the alveoli, causing the CO₂ to diffuse from the blood into the alveoli, where it will be exhaled.

Both respiratory and metabolic mechanisms affect the pH. When all organ systems work well, a finely tuned balance is in constant motion between the lungs and the kidneys- maintaining appropriate O₂, CO₂, and HCO₃ levels. With each gas exchange in the lungs, the oxygen level in the blood rises, and carbon dioxide levels decrease, resulting in a bicarbonate ion's eventual creation. However, when systems are not optimal, the balance is thrown off, and levels of CO₂ and HCO₃ can be too high or too low. The type of imbalance depends on which element (CO₂ or HCO₃) is altered.

The terms acidosis and alkalosis refer to the pH. The normal pH of blood is 7.35-7.45. If the pH is below 7.35, the patient is considered "acidotic." If the pH is above 7.45, the patient is considered "alkalotic."

Once you can determine the pH state (acidosis or alkalosis), further interpretation can give you insight into which systems are not performing optimally.

All types of acid-base imbalances are corrected by fixing the underlying cause. Examples of this may be by utilizing mechanical ventilation (both non-invasive and invasive), balancing electrolytes, managing chronic conditions, and infusions of medications depending on each situation.

One strategy used to assist with respiratory alterations in pH is BiPAP. BiPAP is employed to facilitate improved gas exchange. BiPAP may be administered two ways: non-invasively (using a mask) or invasively (through an endotracheal tube and ventilator). Some patients will even go home on BiPAP for regular use. If you have a patient who brings a BiPAP machine from home, they can use it in the hospital setting. However, the hospital will not supply circuits or interfaces for their home equipment. If they forget their equipment at home, respiratory therapy can provide hospital-owned equipment in certain circumstances.

When a patient is having metabolic alterations in pH, treatment is focused on correcting the underlying cause. Due to the underlying cause, the body is either creating too much bicarbonate or is unable to excrete hydrogen ions. For example, in extreme food poisoning, a patient may experience excessive volume loss through emesis and stool. Bicarbonate ions can be lost in the stool. As fluid loss occurs, less volume is filtered by the kidneys, leading to the increased hydrogen ion concentration in the blood (making it more acidic). With the administration of additional fluids, the blood's fluid volume increases, the kidneys can filter more effectively, and the pH can return to normal.