Respiration and Oxygenation

Respiration is the process of moving air in and out of the lungs, through inspiration and expiration. During inspiration, oxygen enters the lungs and crosses into the bloodstream, where it’s delivered to tissues, a process known as oxygenation. Then, during expiration, carbon dioxide is expelled from the lungs. When measuring your patient’s respiration and oxygenation, you’ll follow the steps of the Clinical Judgment Measurement Model to guide clinical decisions about patient care.

First, let’s review physiological regulation of respiration and oxygenation. Now, respiration is generally an involuntary process controlled by the respiratory center in the brainstem. Here, chemoreceptors in the medulla assess changes in the level of carbon dioxide and pH in cerebrospinal fluid. When CO2 increases and pH decreases, the chemoreceptors signal the respiratory center to increase the respiratory drive, which increases the rate and depth of breathing to eliminate excess CO2. Now, these central chemoreceptors work in concert with peripheral chemoreceptors located in the aortic arch and carotid arteries to regulate respiration.

Peripheral chemoreceptors are primarily sensitive to oxygen levels in the blood. When they detect low oxygen levels, they send a message to the respiratory center to increase the rate and depth of respirations, so more oxygen is inhaled. While respiration is predominantly passive, voluntary changes in respiration are controlled by the cerebral cortex like breaths during swimming or singing.

Alright, let’s review how respiration delivers oxygen to the tissues of the body. During inspiration, oxygen enters the lungs and travels into the alveoli, where it diffuses into the pulmonary capillaries and binds to hemoglobin in red blood cells. From there, the red blood cells deliver oxygen to the body’s tissues. Meanwhile, carbon dioxide diffuses across the capillaries into the alveoli where it is exhaled from the body.

Okay, so you’ll measure your patient’s respirations by counting the number of breaths per minute. If the respirations are faster than normal, it’s called tachypnea; while if the respirations are slower than normal, it’s called bradypnea. It’s also important to look at the depth of breathing, and whether the breaths are regular or irregular, and to measure your patient’s oxygen saturation, or the percentage of oxygen that’s bound to hemoglobin in the blood using a pulse oximeter, to ensure enough oxygen is delivered to the tissues.

Now, when assessing your patient’s respiration and oxygenation, you’ll use the Clinical Judgment Measurement Model to gather and recognize important cues. These can include objective cues like the respiratory rate, rhythm, depth, and oxygen saturation. Additionally, you'll assess for subjective cues such as dyspnea, or difficulty breathing, as well as dizziness or lightheadedness due to decreased oxygen supply to the brain.