About Oxygen: The Difference Between SpO2 and Respiration

SpO2 (oxygen saturation) refers to the percentage of oxygen-saturated hemoglobin in your blood. Respiration describes the process wherein your body takes in oxygen and breathes out carbon dioxide. 

During a stay at a clinic or hospital, medical staff frequently measure the patient's SpO2 and respiratory rate to monitor for signs of respiratory distress. What do these two terms mean, and can you measure them yourself? Why would you want to do so? Let’s explore oxygen saturation and respiration in depth.

Oxygen Saturation (SpO2)

The term oxygen saturation refers to the amount of oxygen in the hemoglobin in the blood. Expressed as a percentage, medical staff use a pulse oximeter to measure an individual’s SpO2. 

In recent years, interest in pulse oximetry, especially using fingertip pulse oximeters, has surged among the public. It emphasized the importance of measuring oxygen saturation, especially in certain situations (e.g., recovering from COVID-19 or respiratory illness, athletic activities, and climbing high altitudes)

In a normal, healthy adult, a normal reading for SpO2 ranges between 95% to 99%. During sleep, the percentage typically falls to about 90%. Interestingly, it also drops when a person works out. Exercise causes oxygen saturation to decrease. Obtaining a reading as low as 90% remains normal.

Individuals with medical conditions that affect respiratory operations, such as COPD, can consider a reading as low as 88% normal. Because of their disease, these patients typically measure a high reading of up to 94%.

Almost no one ever measures 100% oxygen saturation. To do that would mean that every molecule of hemoglobin in your body has an oxygen molecule attached to each of its four potential connections.

The Field of Pulse Oximetry

We refer to the area of medicine devoted to the study of oxygen saturation as pulse oximetry. The typically used pulse oximeter slips onto the finger, but many other styles also exist. Some clip onto a toe. A pulse oximeter for children fits onto a foot check out Cables and Sensors part number S303-490. Pulse oximetry even offers a pulse oximeter specifically designed for prenatal use. The sensor for it fits onto the unborn fetus’s head.

Learn more about pulse oximetry here.

What Happens If Oxygen Saturation Drops Too Low?

If oxygen saturation drops below a normal reading, a person may experience a few symptoms. These might include shortness of breath, fatigue, and a blue tinge to the skin. If the individual does something to increase the oxygen in their blood immediately, such as breathing in oxygen, as you likely see athletes do during televised sports events, without addressing the low oxygen saturation, hypoxemia develops.

Hypoxemia

The blue tinge increases when hypoxemia develops, turning the skin blue. This easily noted visible sign of hypoxemia signals cyanosis has developed.

Hypoxia

Without treatment that adds oxygen to the person’s hemoglobin, hypoxia can develop from hypoxemia. Hypoxia refers to a condition in which the low levels of oxygen move to the body’s tissues. This reduction in the oxygen available to the body’s tissues can cause brain damage, heart damage, or death.

Respiration

If you look it up in the dictionary, respiration means breathing. Medically though, there’s more to it than that. Respiration is the metabolic, biochemical process within a human’s cells.

During respiration, the breakdown of glucose creates energy known as adenosine triphosphate (ATP). The body’s cells use ATP to perform their survival functions. Although this article discusses human respiration, every living species respirates.

Respiratory Rate

In a clinical setting, a doctor or nurse measures the respiration rate of a patient. Respiration rate or respiratory rate refers to the number of breaths an individual takes in a minute (60 seconds).

The body undergoes two types of respiration: aerobic respiration and anaerobic respiration. Let’s look at each in depth.

Aerobic Respiration

The term aerobic respiration refers to the process of cellular respiration requiring the presence of oxygen and producing energy. This continuous cellular process requires oxygen and glucose. It results in carbon dioxide, water, and energy. Here’s the chemical equation for aerobic respiration:

Glucose (C6H12O6) + Oxygen (6O2) → Carbon dioxide (6CO2) + Water (6H2O)+  Energy (ATP).

Anaerobic Respiration

Conversely, anaerobic respiration can only occur without oxygen. It also produces energy from an interaction of glucose and alcohol 2. Here’s the chemical equation for anaerobic respiration:

Glucose (C6H12O6) → Alcohol 2 (C2H5OH) + Carbon dioxide 2 (CO2) + Energy (ATP).

Measuring the Respiratory Rate

In some hospitals and clinics, the medical staff uses medical equipment to measure the respiratory rate of a patient, but in most clinical settings, staff still relies on visible, manual measurement. That means the nurse or doctor times a 60-second period and counts the number of times the patient’s chest rises during that period.

If you were to lay down right now and watch your chest, you could observe the rise and fall of your chest as you breathe. Using a timer on your watch or smartphone, you could take your own respiratory rate the same way a clinician would.

Automated Respiratory Measurements Improve Patient Outcomes

There’s a push in the medical community to use respirometers to measure a patient’s respiratory rate to improve patient outcomes. Some respirometers offer the ability to automate the electronic measurement of respiration.

A recent study by Philips found that using automated electronic means to measure vital signs, including respiration, resulted in an 86% reduction in cardiopulmonary arrests. Because respiratory rate stands as one of the key early indicators of patient deterioration, automated monitoring can offer an early alert to clinicians.

The same Philips study also found that automated monitoring of vital signs, including respiration rate, SpO2, and heart rate, resulted in a 66% reduction in ICU mortality of patients transferred to the ICU. It also led to a 35% reduction in severe adverse events and a 20% reduction in hospital mortality.

Respiratory rate monitoring using automated methods not only reduces the load on medical staff, it also improves patient outcomes by alerting the staff as soon as a change in respiration occurs. Automated monitoring also provides alerts to changes. Many of these electronic devices also include early warning scoring calculations.

Normal Respiratory Rates

The definition of a normal respiratory rate depends on the individual’s age, decreasing as we age. The range of normal breaths per minute spans from 10 to 60. Here’s a quick chart you can reference to check what’s normal for you or your patient’s age group.

Infants can also experience periodic breathing, a breathing variation in which the infant pauses breathing for 10 seconds or less then resumes breathing but taking fast, shallow breaths in a cluster. This normal variation stems from their still-developing respiratory systems. Only a variation lasting longer than 10 seconds would signal respiratory insufficiency.

Tying It All Together

Respiration normally occurs in every living organism, including humans. In a clinical setting, staff monitors oxygen saturation and respiratory rate to identify early warning signs of respiratory distress. They typically accomplish this through automated SpO2 and respiratory rate monitoring using pulse oximeters and respirometers.

While oxygen saturation indicates the amount of oxygen present in hemoglobin, a protein in human blood, the respiratory rate describes the number of breaths an individual takes during a 60-second period.

Normal Standards

Standards of normal readings exist for both measurements. For oxygen saturation, a normal, healthy individual should not measure less than 90%. For respiration, the normal reading varies by age, but the slowest respiration rate of 10 marks the lowest rate for a human. Babies usually breathe fast with a slow respiratory rate coming in at 30.

A lack of oxygenated blood indicates a serious medical issue that requires immediate medical treatment. Similarly, both rapid breathing and slow breathing can indicate a medical issue.

Breathing heavily during exercise, which also depletes the hemoglobin of oxygen, is normal. Experiencing slow breathing during sleep also falls into the normal category. Measuring oxygen saturation during sleep also results in lower readings with 90% commonly occurring.

Monitoring at Home

You can easily monitor both oxygen saturation and respiratory rate at home. You’ll need a pulse oximeter or a smartwatch or fitness tracker that measures SpO2 to track it at home. Use a timer and manually count chest rises to determine the respiratory rate at home.

Keeping abreast of these two vital signs measurements can help a healthy person improve their workouts and a medically challenged individual notice important bodily changes so they can quickly obtain medical help.