Wednesday, 18 July 2007

Type 2 Respiratory Failure and Therapy

In my years as a doctor I have seen many patients come to hospital with worsening respiratory failure due to all sorts of underlying diseases.

The classic example is with the patient with underlying heart failure who gradually gets breathless with worsening oedema who then is so breathless at rest eventually calls for an ambulance.

Of course, in some instances, the paramedics are unaware of the underlying problem and give high flow oxygen.

When the patient reaches the hospital, they can sometimes have a low conscious level which in some instances makes the doctor think of an intracerebral cause and the patient gets sent for a CT head scan which comes back as normal.

In this case, the patient has CO2 Narcosis and hypoxaemia causing the reduced conscious level.

A history from relatives or even the patient plus a detailed examination can provide a wealth of data that can quickly narrow down the cause and differential diagnosis to provide swift treatment.

When examining the patient-- START WITH THE HANDS. Assess for warmth and sweatiness that one can get with CO2 retention. In addition, red palms can also be due to this problem. However, the Gold Standard test is to look for a CO2 retention flap of the hands.

This can quickly tell you if there is a major problem and the likely cause. It is referred to as a Metabolic Flap as it can be caused by CO2 retention, Liver and Renal Failure in the main.

Pulse is an excellent measure. Not checking just the rate, but the QUALITY too. CO2 retention gives a Bounding Pulse that is easy to find. The blood pressure may also be high.

Check the JVP to see if it is raised. There are several causes of raised JVP such as heart failure, cor pulmonale of Type 2 respiratory failure, dysrhythmia, valvular dysfunction, tamponade, superior vena cava obstruction, pulmonary embolism, severe respiratory failure etc...

However, this is where a good history will be of help to try and make some discrimination as to the cause such as being a heavy smoker, previous evidence of myocardial infarction, thromboembolic events in the past, being on oral contraceptives.

Listening to the heart sounds may provide an answer such as obvious heart murmur or reduction in heart sounds as in tamponade. Feeling the apex to assess if has shifted laterally can reveal the chronicity of the problem as in chronic heart failure.

Listening to the chest may reveal the dullness and reduced air entry associated with a pleural effusion plus the classical sounds of bronchial breathing. Moreover, in heart failure, the appearance of widespread wet crackles aids the doctor to make the diagnosis at the bedside. Wheeze is not so easy, as it may signify asthma, COPD or even heart failure. That is why a history helps to refine the mental diagnosis along the way.

Feeling the abdomen for ascites and organomegally can provide further clues about heart failure and lastly, checking the legs, buttocks and abdominal wall for oedema and of course, around the face can also provide salient clues about the extent of heart failure.

Hence, a basic clinical diagnosis can be made at the bedside without a chest xray or blood results. However, these tests DO need to be done, but that should not stop you as doctors from providing emergency treatment whilst awaiting such results.

Basic life saving treatments include:

  • Appropriate oxygen therapy. For example, in the patient with hypoxaemia and a high respiratory rate, high flow high percentage oxygen is likely to be appropriate. However, in the patient with heart failure / COPD and a low respiratory rate, hypoxaemia and reduced conscious level, low percentage oxygen may be more appropriate. The percentage oxygen provided should be guided by arterial blood gas analysis, not just by saturation probe monitoring.

  • Percentage oxygen should be given throw a Venturi Mask and not nasal cannulae. I have seen in the past doctors trying to put 4 litres through nasal cannulae. The idea is flawed because the maximum effective amount of oxygen that can be put through nasal cannulae is only 2 litres. Moreover, if the patient is mouth breathing, there is no way that even 2 litres will give the desired effect. The only way to really ensure an adequate percentage of oxygen is via the Venturi system of facial mask.
  • Normally oxygen starts at 24% and increases upwards to maintain an oxygen saturation of about 92%. In patients with Type 2 respiratory failure, such patients rely on hypoxic drive for respiration. If the drive is abolished by high flow oxygen, the CO2 rises and the patients respiratory status worsens. Patients need to have careful oxygen replacement in order to maintain this hypoxic drive. Of course, when the patient is established on the right percentage of oxygen, a repeat blood gas needs to be obtained to ensure that the oxygen saturation is adequate and that the CO2 is beginning to fall. Additionally, acidosis, should it be present, should be seen to improve.

  • If the Venturi oxygen mask fail to ameliorate the problem of Type 2 Respiratory failure such as persistent hypoxaemia, rising CO2 and acidosis e.g. pH < style="font-weight: bold;">BIPAP. Such therapy is very effective to reduce CO2 and improve acidosis and at the same time raise the oxygen saturation. This can be used in COPD and heart failure, and in the latter condition, the positive pressure helps to push fluid out of the lung tissue and into the vasculature. In such events, reducing the fluid inside the lung alveoli improves compliance of the tissue and reduces the alveolar-capillary barrier thickness and thereby improves oxygenation.

  • Again, once established on BIPAP, blood gases need to be taken to ensure the patient is improving.

  • However, intubation and ventilation is sometimes the eventual progression of these disorders, but instituting such therapy should be the last option as in doing so you put the patient at risk of not being able to be weaned off the machine. Only after a few days of ventilation by a ventilator, the intercostal muscles start to waste and hence, this makes the patient ventilation capability worse if they were to come off the ventilator.

Other measures to improve respiratory outcome:

  • If heart failure is the main problem then using nitroglycerine and furosemide are standard therapies. Nitroglycerine reduces venous return and hence, preload of the heart is decreased. Furosemide has a similar effect and also cause diuresis and reduces afterload. These therapies are relatively safe as long as the patient has a sustainable blood pressure. If the clinical opinion is heart failure, giving such therapies is unlikely to do harm.

  • If wheeze is the predominant problem, giving steroids and beta-stimulant nebulisers may help. Even if the cause of the wheeze is not clear, such as a suspicion of heart failure, but a smoker and previous history of COPD, such therapies should not be withheld. Sometimes, it is not clear which condition predominates and so as a result, treatment for heart failure and COPD/Asthma are given until more information is available to refine the diagnosis. Withholding such life saving therapies to ascertain the true nature of the problem which could take several hours is not good practise because the patient suffers. It is better to sometimes treat several suspected problems at the same time on admission to the hospital as an inpatient and with further test / scans the treatments can be stopped or continued depending on the outcome. Hence, the patient has the life saving therapies from the start and comes to no harm from the disorder as treatment was not withheld. This way of practising medicine is common place in the UK and USA.
  1. Sit your patients up!!! Yes, it is a simple thing to do but very rarely done in Japanese hospitals. I have been to several hospitals in Japan, and in almost every one, patients with COPD and heart failure are nursed flat. This is not standard treatment. Patients who have cardiorespiratory diseases often find it easier to breath when sat up. For example, in COPD, such patients rely on diaphragmatic contraction for breathing as their hyperinflated 'barrel' chests poorly expand. If the patient is sat upright, the use of gravity is enhanced and patients can also sit forwards to fix their chest to enable deeper breathing. By lying COPD patients flat abolishes this advantage and worsening respiratory function can ensue. Heart failure patient rely on gravity so that the pressure in the upper lungs is less than the higher pressure in the lower lobes. This can help with respiratory function. Lying such patients flat equalises the pressure and breathless gets worse. This is why one sees the phenomena of orthopnoea in COPD and CHF and Paroxysmal Nocturnal Dyspnoea in CHF when lying flat. Just by sitting you patients up may improve their oxygen saturations !!!! However, please let your nursing staff know that the patient must be nursed in that position because failure of you as doctors to communicate such orders will find the patient put flat and situation repeats itself.
  • Dysrhythmias should be treated if pathological. For example, fast atrial fibrillation should be treated. It should not be left as a mere matter to observe. AF can lead to worsening heart failure and cardiorespiratory function can worsen as a result. Such patients need to have a echocardiogram to exclude thrombus formation, thyroid function tests and cardiac enzyme level measurement to ensure cardiac damage has not occurred.
  • Patients with renal failure and fluid overload can develop respiratory failure. Such patients may have a metabolic acidosis and poor urine output. Consideration for dialysis / haemoflitration to reduce circulatory volume should be considered on an urgent basis.

The above is by no means an exhaustive guide, but basic patient management with oxygen, positioning and standard basic drugs can make a world of difference to your patients care and hopefully prevent them from progressing to a worsening state.

Remember, the patient comes first. Please consider......