That oxygen mask they strap on patients rushed to the ER after a heart attack or a stroke? It could be doing more harm than good in many cases, Dutch researchers say in a new report.

In a review of earlier research, they found no support for routinely giving critically ill patients high-dose oxygen, a common practice among paramedics and emergency physicians.

"There is not a single study that points to beneficial effects," said Dr. Yvo Smulders, a professor at VU University Medical Center in Amsterdam. "All of the evidence that we found points to detrimental effects."

Most doctors believe extra oxygen is life-saving and many guidelines recommend it, he and his colleagues write in the Archives of Internal Medicine.

"What you would expect is that oxygen is healthy," Smulders told Reuters Health. "But it seems that God didn't introduce 20 percent oxygen in room air for nothing."

Studies on animals dating to the 1960s and 70s have found that higher-than-normal oxygen levels could be dangerous.

Smulders' team gathered all the human research they could find on supplemental oxygen after heart attacks, strokes, cardiac arrest and acute attacks of chronic obstructive pulmonary disease, or COPD.

The 18 studies they came up with all had the same grim message: supplemental oxygen doesn't work, and there is some weak evidence that it might be harmful.

For instance, one trial from 1976 found nine out of 80 heart attack patients who got oxygen died, compared to just 3 out of 77 who got compressed air. Although that difference could have been a statistical fluke, it was still bad news for oxygen.

Another trial, this one in stroke patients, had to be stopped early because too many patients who got extra oxygen died.

And for cardiac arrest, in which the heart stops beating, a study out last year found that people who had a lot of oxygen in their blood after they were revived died more often than people with normal levels.

"It has potentially far-reaching implications, because supplemental oxygen is just ubiquitous in the care of critically ill patients," Dr. Stephen Trzeciak, who led that work, told Reuters Health.

Too much oxygen in the blood can lead to the formation of molecules known as free radicals, he said, which can damage organs such as the heart and the brain.

But this is still theory, Trzeciak warned, and so far there is no iron-clad proof that supplemental oxygen is harmful. What is clear is that too little oxygen can be lethal.

"My concern is, if we just indiscriminately stop giving supplemental oxygen to post-arrest patients, they might end up having low oxygen, which is just as harmful or more harmful" than high oxygen, said Trzeciak, who studies resuscitation at Cooper University Hospital in Camden, New Jersey.

The American Heart Association currently recommends giving supplemental oxygen to people with cardiac arrest until the heart is restarted.

At that point, the group urges doctors and paramedics to use measurements to ensure that oxygen levels in the blood don't get too high. The same goes for heart attacks.

But what often happens is that providers just leave the oxygen on full blast, according to Dr. Michael Sayre of the American Heart Association.

"They don't realize they are giving too much oxygen," Sayre told Reuters Health. "It's just not something they are paying attention to."

The Dutch researchers call for more studies. But until then, Smulders said, health providers should only give oxygen when blood levels are very low and they should make sure they never become too high.

"I think it is about time that you step away from your intuitive approach and look at the evidence," he said.

What is pneumonia?

Pneumonia is an inflammation of the lung tissue affecting one or both sides of the chest that often occurs as a result of an infection. Infection can be caused by a lot of different micro-organisms – viruses (eg respiratory syncytial virus), bacteria, fungi (eg histoplasmosis) and parasites. In addition to infection, pneumonia can also be caused by corrosive chemicals breathed into the lungs or toxic smoke inhalation from a fire.

Rarely, pneumonia can result from you breathing in something that you are allergic to. This may be related to a hobby or to your employment. The medical term for pneumonia caused by an allergy is extrinsic allergic alveolitis. An example of this condition is farmer’s lung, caused by breathing in the dust from mouldy hay.

Pneumonia is still a common disease affecting around 1 per cent of the adult UK population each year. Many people die from it every year, most commonly women and especially people over the age of 70. The overall death rate due to pneumonia is currently 5 per cent, ie around 1 in 20 people contracting the condition die from it.

Half of all pneumonia cases are caused by bacteria. The bacteria, known as streptococcus pneumoniae is the main cause of the most typical pneumonia.

How is bacterial pneumonia contracted?

Infection usually occurs when you breathe in the micro-organisms.

More rarely, pneumonia is contracted when bacterial colonies from infections in other places in the body - such as an infected bone - travel via the blood circulation to the lungs and stay there.

Finally, you can breathe in the contents of your stomach, eg following vomiting, which causes chemical pneumonia and may bring micro-organisms into the lungs.

What are the signs of pneumonia?

• Classic bacterial pneumonia starts suddenly with shivering fits, fever, pains in the chest and coughing.
• The cough is dry at first, but in a day or two the person starts to cough up phlegm. The phlegm is usually yellow, bloodstained or rust-coloured.
• Breathing is typically fast and shallow. The infected person may gasp for air and may even go bluish around the lips and nails due to the lack of air (cyanosis).
• It hurts to breathe in deeply or cough. This may be a sign that the inflammation has spread to the membrane that covers the lungs (pleurisy).
• Acute confusional state (more common in the elderly).
• There may also be a serious outbreak of herpes (cold sores) around the mouth, which shows that your immune system is not now able to defend against the herpes virus.

If you catch a cold, that doesn't seem to go away, or recognise the symptoms mentioned above, it is important to seek medical advice.

Who is at greatest risk of pneumonia?

• Children, especially when chronically ill. Childhood pneumonia may be mistaken for appendicitis.
• The chronically ill, especially those with heart, liver or kidney conditions, asthmatics, people with smoker's lungs and diabetics.
• People with weak immune systems, such as HIV-infected individuals.
• The weak and elderly.
• People who have had their spleen removed.
• Alcoholics.

How can I avoid getting it?

Smoking damages your lungs and makes them more likely to become infected. If you smoke, the best thing you can do to prevent pneumonia is to stop smoking.

As of September 2006, all children will be offered a pneumococcal vaccine as part of their routine childhood vaccinations. This vaccine protects against the most common kind of pneumonia, caused by the Streptococcus pneumoniae bacteria, known as pneumococcus. The vaccine will given as three doses, at two, four and thirteen months of age. Some children who are chronically ill may also need a further pneumococcal booster after their second birthday. Your doctor will advise you.

If you are more than 65 years old, your immune system is relatively impaired, or if you suffer from a chronic disease such as smoker's lungs, asthma, a chronic heart, liver or kidney condition, or diabetes, you should also get vaccinated against pneumococcus. It is also important to take good care of yourself and get vaccinated against the flu, particularly if there is a bad flu epidemic around.

If your spleen has been removed, for instance after a road accident, it is important to get a vaccination against pneumococcus. Failure to get vaccinated means you run the risk of catching pneumonia. Around five years after the vaccination, your doctor needs to take a blood sample to see if it is still effective.

How does the doctor decide that you have pneumonia?

The doctor will ask you questions about your illness, and then perform an examination of your chest, by tapping or 'percussing' it with his or her fingers and by using a stethoscope. The doctor will then listen for sounds that are not normally heard, like creaking and bubbling sounds when breathing.

In the majority of cases further investigation is not required. If however the doctor is particularly concerned about a patient, they will often be directed to their local hospital where some X-ray pictures of the lungs will be taken to see how bad the condition is. Only if the condition was very severe, would they need to be admitted to hospital for treatment.

If it were necessary, the micro-organism could be grown from your phlegm or your blood to find out what it is and decide the best course of treatment to take.

Future prospects

The natural history of pneumonia varies, depending upon the person who catches it, the bacteria involved and the treatment provided.

In repeated cases of pneumonia and cases where the condition refuses to respond to a series of different treatments, there may be something else very seriously wrong like lung cancer.

Even following an episode of pneumonia that has been successfully treated, it is only natural to experience a period after the infection where you feel tired, get easily short of breath and have an annoying, persistent cough that can linger for several weeks.

How can pneumonia be treated?

It is possible to treat it with antibiotics such as penicillin. Apart from that, other support may be necessary, eg chest physiotherapy, oxygen treatment.

If you have been abroad within two to three months before contracting the disease, it is important that you tell your doctor right away. Foreign bacteria sometimes require a different treatment from those seen more commonly in the UK.

How can the medicine be given?

• Amoxicillin (eg Amoxil), by mouth.
• Benzylpenicillin (eg Crystapen), as an injection.
• Erythromycin (eg Erythroped), by mouth. Given if allergic to penicillin.

Other antibiotics may also be given, by mouth or injection, depending on the micro-organism that is found to be causing the pneumonia.

Based on a text by Dr Flemming Andersen - netdoctor