In the ICU blood tests are usually done at least once a day. They measure such things as the haemoglobin level, markers of infection, how well the blood is clotting, and how well the kidneys and liver are working. These are some of the indicators of how the body is working and can show the intensive care specialist how well a patient’s body is coping with their illness. Intra-arterial and intravenous lines (tubes placed in arteries and veins) are often used to monitor the body and, once established, allow rapid, reliable and pain-free access for repeated blood tests. Some conditions will require multiple repeated blood testing every few hours.

Patients with critical illness commonly develop problems with their hearts and circulation. Various factors are involved, some related to the primary disease while others are secondary effects. Problems include changes in the distribution and volume of body fluid, the condition of the blood vessels and the ability of the heart to pump blood around the body. Treatment for cardiovascular problems may include fluids therapy and a wide range of medicines to control the heart rate, cardiac function and blood pressure.

Respiratory failure occurs when the respiratory system is no longer able to provide enough oxygen requirements or remove enough carbon dioxide from the body. Hypoxia (not enough oxygen is reaching the tissues) may occur unless there are interventions. Large amounts of carbon dioxide may also build up in respiratory failure. Mechanical Ventilation is the use of a ventilator (sometimes called a life support machine) to do the breathing for a patient experiencing respiratory failure. The ventilator fills the lungs with oxygen and removes carbon dioxide via a breathing tube that sits in the patient’s airway. Patients are usually given sedating medications to help them tolerate the breathing tube and ventilator. Sometimes people may require a ventilator for a long time. If this is the case a tracheostomy (when an opening is made in the trachea) is performed and the breathing tube is inserted into the opening. A tracheostomy is more comfortable for the patient and allows them to be managed on a ventilator without the need for sedating medications.

A nasogastric tube is often inserted at the same time as the endotracheal tube. The nasogastric tube is inserted into the stomach via the nose. This tube ensures that patients receive the necessary nutrition while they are in the Intensive Care Unit.

Kidney (or renal) failure is when a patient’s kidneys are unable to remove wastes and excess fluid from the blood. The likelihood that the kidneys will get better depends on what caused the kidney failure. Sometimes a patient’s kidney failure progresses to the point where they require a machine to take over the function of the kidneys. This is called renal replacement therapy or dialysis.

Patients with coronary artery disease can have arteries that are blocked or narrowed, meaning blood flow to parts of the heart is poor or non-existent. Coronary artery bypass surgery (CABG) is a surgical procedure that uses veins or arteries from elsewhere in the body e.g. the leg to create a detour around the blocked coronary artery to improve or restore blood flow to the heart muscle. The procedure involves making a cut through the front of the chest and breast bone (sternotomy) so the surgeons can operate directly on the heart. During the procedure the patient's heart is stopped and replaced by an external heart-lung bypass machine. Once the surgery is complete the heart is restarted and the heart-lung machine removed, the breast bone is joined back together and the chest wound sewn up. The operation can take between 3-5 hours.

The heart has four major valves that act like gates to allow blood to flow in the correct direction. In some disease processes the valve can become narrow (stenosis) which means less blood can flow through it. The valve can also become ‘leaky’ which means the blood can flow both forwards and backwards. Both problems cause difficulties with blood flow and therefore the ability of the heart to function effectively. These valves can be repaired or replaced, using an artificial valve or a valve from a human donor or a pig. The procedure involves making a cut through the front of the chest and breast bone (sternotomy) so the surgeons can operate directly on the heart. During the procedure the patient's heart is stopped and replaced by an external heart-lung bypass machine. Part of the heart is then opened and the valve repaired or replaced. Once the surgery is complete the heart is restarted and the heart-lung machine removed, the breast bone is joined back together and the chest wound sewn up. The operation can take between 3-5 hours.

Congenital heart disease occurs from birth and can include structural defects and heart rhythm problems. the heart can have difficulty pumping efficiently because it is not completely developed. In some situations surgery can be performed on the young baby, infant or child but for others the surgery is left until adulthood. Congenital heart surgery can involve repairing the abnormality e.g. repairing defects in the internal walls of the heart with stitches or a patch made from either the patient's own tissue or from an artificial source or a procedure that will make the patient more comfortable but that will not necessarily correct the defect e.g. inserting a tube to connect the major vessels to increase blood flow to the lungs.

Heart or lung transplant surgery can be performed on patients with end stage heart or lung failure with poor life expectancy. Often other treatments have already been considered or attempted prior to recommendation. Some patients are not suitable for transplant surgery. In transplant surgery the patient’s heart or lungs are removed and replaced by a donor heart or lungs.

The ECMO machine is similar to the heart-lung bypass machine but it is used outside the operating theatres. The machine takes over the work of the heart and lung when the heart and lungs are so severely affected that they cannot support the needs of the body. The blood is pumped around an external circuit and through a membrane that removes carbon dioxide and adds oxygen, essentially acting like a lung. The aim of this therapy is to rest the body; it is not a treatment.

This involves the removal of a piece of diseased lung caused by a tumour, lung abscess or bleb. This will also often include lymph node removal. Remaining lung tissue over-expands to fill in the portion previously occupied by the resected lung. Chest drains are used post-operatively. Pain relief is given to ensure that the patient can cough and take deep breaths, which helps with their recovery.

This involves removal of an entire lung when there is a tumour that can’t be removed by partial resection of the lung. Once the lung is removed, the involved side of the thoracic cavity is an empty cavity and this fills with fluid over time. Again, chest drains are placed post-operatively. Pain relief is given to ensure that the patient can cough and take deep breaths, which helps with their recovery.

Removal or the stripping off of a thick fibrous membrane (scar tissue) that develops over the lining of the lung following infection. This constricts the lung and interferes with lung expansion.