Hypoxemia

Hypoxemia is when oxygen levels in your blood are lower than normal. If oxygen levels are too low, your body may not work properly.

When you breathe in, oxygen from the air travels through your lungs into small air sacs (alveoli). Small blood vessels travel close to the alveoli and pick up the oxygen. Finally, oxygen travels through your blood to your tissues and organs, giving them energy.

Hypoxemia can happen if you can’t breathe in enough oxygen or if the oxygen you breathe in can’t get to your blood. Air and blood flow are both important for having enough oxygen in your blood. This means both heart and lung issues can lead to hypoxemia.

Hypoxemia can happen suddenly and for a short period of time (acute). It can also be long-term — over months or years. In this case, you may hear it called chronic respiratory failure. If you have symptoms of hypoxemia — like shortness of breath or bluish or grayish skin, lips or nails — call 911 (or your local emergency service number) or go to the emergency room.

Symptoms of hypoxemia

Hypoxemia symptoms vary depending on the severity and underlying cause. Some hypoxemia symptoms include:

• Headache
• Difficulty breathing or shortness of breath
• Fast heart rate
• Tiredness
• Coughing
• Wheezing
• Confusion
• Bluish skin, fingernails or lips (cyanosis)

Hypoxemia causes

The most common cause of hypoxemia is an underlying illness that affects blood flow or breathing (like heart or lung conditions). Medical conditions that can lead to hypoxemia include:

• Anemia
• ARDS (acute respiratory distress syndrome)
• Asthma
• Blood clot in your lung (pulmonary embolism)
• Bronchitis
• Collapsed lung (pneumothorax)
• Congenital heart defects
• Congestive heart failure
• COPD (chronic obstructive pulmonary disease)
• Fluid in your lungs (pulmonary edema)
• Lung scarring (pulmonary fibrosis)
• Pneumonia
• Pulmonary hypertension
• Underinflated lungs (atelectasis)

Other causes include:

• Medications that slow your breathing, like sedatives
• Being at high altitudes
• Sleep apnea (nocturnal hypoxemia)

Types of causes

Five categories of conditions usually cause hypoxemia:

• Ventilation-perfusion (V/Q) mismatch
• Diffusion impairment
• Hypoventilation
• Low environmental oxygen
• Right-to-left shunting

Ventilation-perfusion (V/Q) mismatch

For oxygen to get to your blood, you need both airflow into your lungs (ventilation) and blood flow to your lungs (perfusion) to pick it up. If one of these isn’t working, you’ll end up with plenty of oxygen in your lungs but too little blood flow to pick it up, or vice versa. This is called ventilation-perfusion, or V/Q, mismatch. A heart or lung condition usually causes it.

Diffusion impairment

Even if you have good airflow and good blood flow, sometimes it’s difficult for the oxygen to pass — or diffuse — from your lungs to your blood vessels (diffusion impairment). Emphysema, lung scarring, or diseases that make it more difficult for the blood to flow between your heart and lungs can cause diffusion impairment.

Hypoventilation

Hypoventilation is when you don’t breathe deeply enough or breathe too slowly. This means not enough oxygen is getting into your lungs. Lung conditions, severe muscle weakness, certain medications and some diseases that affect your brain can cause hypoventilation.

Low environmental oxygen

If there’s not enough oxygen in the air around you to breathe in, your blood can’t get the oxygen it needs to keep your body working. Locations at high altitudes have less oxygen available in the air than those at lower altitudes. This is why traveling to higher altitudes or flying can cause minor breathlessness to severe altitude sickness.

Right-to-left shunting

Deoxygenated blood flows into your heart from the right side. It gets pumped out to your lungs to get oxygen. Then, it comes back in from the left side and gets pumped out to your tissues. Sometimes, deoxygenated blood can get pushed over to the left side of your heart and go out to your tissues without getting oxygen in your lungs first (right-to-left shunting). It’s usually caused by an abnormality in your heart.

Risk factors

Any condition that reduces the amount of oxygen in your blood or restricts blood flow can cause hypoxemia. People living with heart or lung diseases — like congestive heart failure, COPD or asthma — are at an increased risk. Some contagious illnesses, like the flu, pneumonia and COVID-19, can also increase your risk of hypoxemia.

Complications

If your blood has low levels of oxygen, it can’t deliver enough to your organs and tissues that need it to keep working (hypoxia). This can damage your heart or brain if it goes on for a long time (for instance, with nocturnal hypoxemia caused by sleep apnea). If it happens suddenly and severely, hypoxemia can be fatal.

How doctors diagnose hypoxemia

To diagnose hypoxemia, your healthcare provider will listen to your heart and lungs. They may also check to see if your skin, lips or fingernails look bluish or grayish.

Tests to check blood oxygen levels include:

• Pulse oximetry: A sensor that slips over your finger measures the amount of oxygen in your blood. Pulse oximetry is painless and noninvasive. Many doctors use it routinely each time you visit.
• Arterial blood gas test: A provider uses a needle to take a blood sample from your wrist, arm or groin to measure the levels of oxygen in your blood.
• Six-minute walk test (6MWT): This tests how far you can walk on a flat surface in six minutes. This test helps evaluate lung and heart function.

How is hypoxemia treated?

To help raise oxygen levels, your provider might use supplemental oxygen. You might need supplemental oxygen all the time or only with exertion or while sleeping. If you have severe hypoxemia, you might need a machine that breathes for you (ventilator).

Depending on the underlying cause of hypoxemia, medications or other treatments can help raise your blood oxygen levels. Your provider might recommend:

• Inhalers with bronchodilators or steroids to treat lung diseases like COPD
• Medications that help to get rid of excess fluid in your lungs (diuretics)
• Continuous positive airways pressure (CPAP) to treat sleep apnea
• Antibiotics to treat pneumonia

When should I see my healthcare provider?

COPD, sleep apnea and other medical conditions may cause chronic or intermittent hypoxemia with less severe or no symptoms. If you have a lung or heart condition, talk to your healthcare provider about your concerns and specific ways to lower your risk. Your provider might recommend monitoring your oxygen levels at home.

Even for those without heart or lung conditions, certain medications and situations — like traveling to a higher altitude — can increase your risk of hypoxemia. Ask your provider about any special precautions you need to take while traveling or taking medication. Allow time to safely adjust to higher altitudes when you travel.

When should I go to the ER?

Severe hypoxemia can be fatal within minutes if left untreated. Call 911 (or your local emergency service number) or go to the emergency room if:

• You have any symptoms of hypoxemia, or if others notice a sudden change in your behavior or awareness (restlessness, confusion, change in consciousness)
• You have an ongoing medical condition and your usual symptoms worsen suddenly, or you experience new symptoms that might be hypoxemia

What is the outlook for people with hypoxemia?

Depending on the cause, you might need a one-time treatment or ongoing treatments. Your healthcare provider will work with you to manage it.

How can I reduce my risk of hypoxemia?

Managing any underlying conditions is the best way to keep your blood oxygen at safe levels and lower your risk of hypoxemia:

• Don’t ignore new symptoms. Trust yourself if you feel something is off. Contact your healthcare provider or go to the ER.
• If your healthcare provider prescribes oxygen, use it as directed.
• Practice pulmonary hygiene. If you have COPD or asthma, know your triggers and make sure you always have a rescue inhaler with you, if prescribed. Use an incentive spirometer, perform breathing exercises and follow any other recommendations for lung health from your healthcare provider.
• Quit smoking. If you smoke, quitting can help increase lung function to bring more oxygen into your lungs. Quitting also helps prevent further damage to your lungs.
• Take any medication as prescribed by your healthcare provider.
• Make a plan for high altitude travel. Even those without heart or lung conditions can have trouble breathing at high altitudes. Understand how it might affect you, and make a plan to adjust to the change.

When you plan for high altitude travel, know what you’ll do ahead of time if you should need medical attention. Give yourself plenty of time to adjust, if necessary, and bring any extra equipment or medication you might need.