Emphysema is a progressive, chronic lung condition characterized by damage to the alveoli, the tiny air sacs responsible for gas exchange. This destruction reduces the surface area for oxygen to enter the bloodstream, leading to breathing difficulty and low oxygen levels in the body’s tissues. Emphysema is a major component of Chronic Obstructive Pulmonary Disease (COPD), which worsens over time. Determining when supplemental oxygen is necessary involves assessing both the structural severity of the lung damage and the body’s physiological response.
Understanding Emphysema Severity Stages
The severity of emphysema, as part of COPD, is classified using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) staging system. This system relies on spirometry, a test measuring how much air a person can exhale and how quickly. The stage is determined by the Forced Expiratory Volume in one second (FEV1), compared to the predicted value for a healthy person.
GOLD Stage 1 (Mild) means the FEV1 is \(80\%\) or more of the predicted value. GOLD Stage 2 (Moderate) occurs when the FEV1 falls between \(50\%\) and \(79\%\). Patients in these stages may have shortness of breath during exertion but usually do not require continuous oxygen support.
GOLD Stage 3 (Severe) is indicated by an FEV1 between \(30\%\) and \(49\%\). At this stage, breathing difficulty often impacts daily activities, and patients may be evaluated for supplemental oxygen if their blood oxygen levels are consistently low.
GOLD Stage 4 (Very Severe) is defined by an FEV1 less than \(30\%\). This represents the most advanced stage of airflow limitation, and patients frequently experience severe symptoms even at rest. While the GOLD stage indicates mechanical severity, the actual physiological oxygen level in the blood determines the need for oxygen therapy.
Clinical Criteria for Supplemental Oxygen Therapy
The decision to prescribe supplemental oxygen, known as Long-Term Oxygen Therapy (LTOT), relies on specific physiological measurements indicating chronic hypoxemia (low blood oxygen). These criteria are independent of the GOLD stage, though patients in later stages are more likely to qualify. Measurements are typically taken while the patient is awake, at rest, and breathing room air.
The most precise measurement is the arterial partial pressure of oxygen (PaO2), determined by an arterial blood gas test. LTOT is prescribed for patients with a PaO2 of \(55\) millimeters of mercury (mm Hg) or less. This corresponds to an oxygen saturation (SpO2) of \(88\%\) or lower, measured by a pulse oximeter.
Oxygen therapy is also indicated if the PaO2 falls between \(56\) and \(59\) mm Hg (or SpO2 is \(88\%\) to \(89\%\)) and the patient has accompanying complications. These complications include right-sided heart failure (cor pulmonale) or an elevated red blood cell count (hematocrit greater than \(55\%\)). These conditions signal that chronic lack of oxygen is straining the heart or causing the body to overproduce red blood cells.
While pulse oximetry monitors blood oxygen levels non-invasively, the PaO2 from an arterial blood gas test remains the definitive measurement for prescription. The goal of oxygen titration is to maintain the SpO2 within a target range of \(88\%\) to \(92\%\). Providing excessive oxygen can be counterproductive in some emphysema patients, potentially leading to carbon dioxide retention, known as hypercapnia.
Living with Long-Term Oxygen Therapy
Once LTOT is prescribed, the focus shifts to maximizing its effectiveness and integrating the equipment into daily life. The primary goal of LTOT is to improve survival and enhance quality of life by reducing chronic hypoxemia symptoms. Consistent use of oxygen has been shown to prolong life in patients with severe hypoxemia.
For maximum survival benefit, guidelines recommend using supplemental oxygen for a minimum of \(15\) to \(16\) hours per day. This duration ensures adequate oxygenation, reducing strain on the heart and other organs. Depending on the severity of hypoxemia, some patients may require continuous, \(24\)-hour use.
Oxygen delivery methods include compressed gas tanks, liquid oxygen systems, and oxygen concentrators, which filter nitrogen from the air. Portable units allow patients to remain mobile and participate in activities outside the home. A physician determines the flow rate and delivery method based on the patient’s individual resting, walking, and sleeping oxygen needs.
A safety consideration for all patients using supplemental oxygen is the necessity of avoiding open flames or smoking. While oxygen is not flammable, it significantly supports combustion, causing materials to ignite more easily and burn hotter. Patients and household members must be diligent about fire safety where the oxygen equipment is stored and used.
Consistent Medical Monitoring
The need for supplemental oxygen is determined by objective measurements of oxygen in the blood, specifically the arterial partial pressure of oxygen (PaO2) and oxygen saturation (SpO2) levels. Because emphysema is a progressive illness, consistent medical monitoring is necessary. This monitoring, including periodic blood gas analysis and pulse oximetry, determines if and when oxygen therapy should be initiated or adjusted.