During the assessment it's likely that the amount of oxygen in your blood will be measured by taking a blood sample from your earlobe or wrist, or attaching a sensor to your finger (a pulse oximetry test). You may also be asked to breathe into a device called a spirometer during a spirometry test. Regular oxygen treatment may be recommended if the amount of oxygen in your blood is low. It's important that home oxygen treatment is only given if test results indicate that it's needed. This is because studies have shown that if oxygen is given just for breathlessness it can cause unnecessary harm.