Continued low oxygen levels may lead to respiratory or cardiac arrest. This may improve the outcomes of those with cystic fibrosis and other respiratory infections. Subcutaneous emphysema can result from puncture of parts of the respiratory or gastrointestinal systems. Death from ingesting large amounts of the plant results from cardiac arrhythmias and respiratory failure. There are other differences in respiratory and circulatory structures. Doxycycline has been used successfully to treat sexually transmitted, respiratory, and ophthalmic infections. These are irritating to mucous membranes and respiratory tract. DEFRA has published guidelines for people suffering from respiratory and heart diseases. The main impact is on the respiratory and the circulatory system. It causes irritation to skin, eyes, and respiratory tract. Pure oxygen has use in medical treatment of people who have respiratory difficulties. Death is due to suffocation resulting from paralysis of the respiratory muscles. Death is usually secondary to respiratory paralysis. It causes death by heart or respiratory failure. Several firefighters had to undergo treatment for respiratory irritation.