Berkshire Sleep Apnoea
and Respiratory Clinic

Investigations available

• At the Berkshire Sleep Apnoea and Respiratory clinic there are a number of different investigations that can be carried out to help diagnose your sleep disorder or respiratory problem. 

  Sleep Study

  There are various ways of and assessing the severity of your snoring and establishing whether you have sleep apnoea. At Dunedin Hospital we use a multi-channel diagnostic sleep study system called Visi-lab 3 Digital. Visi-Lab is a minimal patient contact system for sleep screening, and is widely used throughout the UK. The Visi-3 system uses digital audio/video recordings and oxygen recording (oximetry) to generate measures of sleep disturbance allowing a comprehensive assessment of sleep disordered breathing and disturbed sleep.

  

  On the evening of your study you will need to arrive at the hospital at around 8pm. The staff will show you to your room and explain the study in more detail. You will be attached to a probe on your finger to record oxygen levels and pulse rate, some electrodes on your chest to record your heart tracing, and a strap around the chest which carries a box into which the various wires connect. In the room there is a camera, a microphone and a low level infra-red light source. After setting up the equipment you will be left to sleep, but if you have any problems during the night you can call the nurses via the intercom system and they will be able to help.

  In the morning you can stay for breakfast and then go to work or return home depending on your plans. You should be given an appointment for a follow-up appointment in the clinic before you leave the hospital. The study is then analysed and a report generated in preparation for your follow-up visit.

  More on sleep study

• Pulmonary function tests

  Lung function tests enable measurement of your breathing capacity and airway function. They can help establish the cause of your symptoms, are useful for monitoring some conditions, particularly a chronic illness, and can be reassuring if you are concerned about your health especially if the results are normal.

  Your tests will be described in detail by the technician at the hospital. You will need to blow into a machine usually by putting a mouthpiece in your mouth, like a snorkel. You will usually have to do this several times. You may be asked to wear a nose-clip.

  The tests should take between 30 minutes and one hour. If you are very breathless, they may take longer. You may also need a ‘reversibility test’. This involves giving you a dose of an inhaled drug often used in asthma (salbutamol); the tests may be repeated to assess whether they are different in response to the medication. This test can be useful to establish whether there is a significant asthmatic component to your symptoms.

  

  Different tests

  Peak flow: Measures the fastest speed you can blow out. To do the test you take the biggest breath in that you can and then blow out as fast as you can. The results are useful in diagnosing asthma and deciding on its treatment. This test can usually be performed in the clinic and does not need specialist equipment.

  
  Spirometry test: Measures your FEV1 (forced expiratory volume in 1 second). This is a useful way of assessing airway calibre. It is most often affected by smoking and asthma. It can also give an estimate of your vital capacity which is a marker of lung size.

  Lung volumes: Measure the size of the lungs in more detail. These tests use helium gas, which is not absorbed into the body. It allows the technician to work out parameters such as total lung capacity.

  Transfer factor: Measures how well your lungs can extract a substance from the air you breathe, and transfer it to the blood stream. To do this a very small dose of carbon monoxide is given to you with helium. There are usually no side effects from either of these gases.

  Oximetry: Measures the concentration of oxygen in the blood via a probe on the finger.

  Occasionally other tests of respiratory function may be necessary. These may have to be performed in the hospital, such as taking blood directly from your artery to measure carbon dioxide levels (an arterial blood gas), or an exercise test.

  More on pulmonary function testing

• Bronchoscopy

  Bronchoscopy is a procedure which allows a doctor to look into your large airways (the trachea and bronchi). These are the main tubes that carry air into the lungs. It is usually performed using a fibre-optic bronchoscope. This is a thin, flexible, telescope which is passed through the nose or mouth, down the back of the throat, into the windpipe (trachea), and down into the bronchi. The fibre-optics allows light to shine round bends in the bronchoscope so the doctor can see inside your airways.

  

  The procedure is usually done as an outpatient or day case. The doctor will numb the inside of your nose and the back of your throat by spraying on some local anaesthetic. This may taste a bit unpleasant. Also, you will normally be given a sedative to help you to relax. This is usually given by an injection into a vein in the back of your hand. The sedative can make you drowsy, but it is not a general anaesthetic and does not 'put you to sleep'. However, you are unlikely to remember anything about the bronchoscopy if you have a sedative.

  Throughout the procedure you will be connected to a monitor to check your heart rate, blood pressure and oxygen levels. Oxygen is also administered during the procedure via a nasal tube.

  The doctor may take one or more biopsies of parts of the inside lining of the airways - depending on why the test is done and what they see. The biopsy samples are sent to the laboratory for analysis.

  The bronchoscopy itself usually takes about 20-30 minutes, but you should allow at least two hours for the whole appointment to prepare, give time for the sedative to work, for the bronchoscopy itself, and to recover. The nursing staff will allow you to return home once you have made a satisfactory recovery. Occasionally it may be necessary for you to remain in hospital if the procedure was difficult or complications arise, or if you live alone.

  Please note that you should not drive yourself home if you have received sedation.
   

  More on bronoscopy