Well-controlled, stable, treated asthma does not affect the lungs’ ability to extract needed oxygen from the air we breathe. Severe exacerbations of asthma, however, have the potential to significantly interfere with the lungs’ capacity to obtain oxygen from the air around us and send it into the body. When ongoing inflammation, bronchospasm, and mucus accumulation narrow the bronchial passages, oxygen levels may decrease.
The emergency treatment of an asthma exacerbation that brings a patient to the emergency room, for example, always begins with supplemental oxygen, given by an oxygen mask or by nasal prongs. In an asthma emergency, it is always better to err on the side of safety and automatically pre-scribe supplemental oxygen, rather than risk reduced oxygen. Once an asthma exacerbation resolves and control of asthma is regained, oxygen levels return to normal; thankfully no permanent or long-term change affects oxygenation!
A pulse oximeter is a small portable device that provides a noninvasive way of determining if the body’s oxygen levels are normal or reduced. A pulse oximeter measures oxygen percent saturation through a painless sensor that is usually placed on a fingertip covering the nail bed. Pulse oximetry can be performed any place healthcare is provided—in a clinic, doctor’s office, ambulance, emergency room, or hospital. It is also standard practice to monitor patients undergoing anesthesia with continuous pulse oximeter measurements.
I am often asked what a normal reading is, and as a rule, a value of 95% or more indicates adequate oxygen levels. A healthy person with well-controlled asthma can be expected to have oximetry readings of 95–100%. Variations can be due to nonpulmonary factors, such as age, altitude, and degree of fit-ness. Other ways doctors assess oxygenation is by physical examination (a blue discoloration of the lips or of the nail beds, called cyanosis, indicates inadequate oxygen) and by direct sampling of blood from an artery—an arterial blood gas, or ABG.