Respiratory failure: Causes, risk factors, symptoms, complications, treatment

Respiratory failure is a condition which happens when the lungs cannot maintain the normal oxygen and carbon dioxide levels in the body. Human life exists within a very narrow range of these gases. Thus, even minor disturbances can have deadly consequences. Fortunately, evolution has bestowed us with several mechanisms to keep the breathing stable and efficient. Several lung diseases can impair these functions. And, depending on the predominant gas affected it is called as Type I or Type II respiratory failure. Type I or hypoxic respiratory failure occurs when lungs fail to deliver sufficient oxygen to the tissues whereas Type II or “hyper-capneic” failure is characterised by an inability to remove excess carbon dioxide.Pneumonia & pulmonary embolism (clot within the lungs) are examples of Type I failure, whereas advanced COPD/Emphysema typically lead to Type II failure. Respiratory failure can be temporary or permanent, pneumonia is a good example of a temporary respiratory failure. Successful treatment of pneumonia usually returns the oxygen levels back to normal. Idiopathic pulmonary fibrosis (a type of lung fibrosis) is an example of permanent respiratory failure. Short of a lung transplant, it is a progressive and often fatal disease. The symptoms of respiratory failure often mirror the underlying disease that led to the failure. A patient with pneumonia may present with signs of infection such as fever, cough, breathing difficulty and low oxygen levels on pulse oximetry. Someone with COPD or asthma may have wheezing and breathlessness - and a blood gas analysis will likely show elevated carbon dioxide levels. Excess CO2 levels can also cause confusion, lethargy and drowsiness. A significant deviation in oxygen or CO2 levels can impair the functioning of vital organs, and potentially lead to cardiac arrest if not addressed promptly. The immediate treatment of respiratory failure involves supplemental oxygen to correct low oxygen, and augmenting removal of CO2 by means of a “ventilator”. A ventilator is a machine which can partially or completely take over the process of breathing, until the lungs recover. It does this by delivering a controlled mixture of oxygen and air into lungs. The advent of sophisticated ventilators have made it possible to support breathing for extended periods of time safely and they form one of the most essential and easily recognisable machines in a ICU. Traditionally, ventilatory support was only possible through a tube (Endo-tracheal tube ) placed in the patient’s windpipe. This often required the patient to be sedated with medication. The advent of “Non-invasive ventilators” where a tight mask applied over the nose and mouth delivers the air mixture was a breakthrough and was useful for milder forms of respiratory failure especially due to COPD or emphysema. This also enabled some of the patients to receive ventilator support outside of the intensive care unit, even at home.In some cases, the respiratory failure is so profound that even ventilators may not be sufficient to maintain adequate gas exchange. An extracorporeal membrane oxygenation (ECMO) device may be the only life -saving treatment in such cases. Similar to a dialysis machine, it removes blood from the body through a catheter, corrects the gases and returns it through a different catheter. Although an expensive and complex procedure with potential complications, it can correct the most severe forms of respiratory failure.Although ventilators can support breathing, they are not a definitive treatment. The definitive treatment depends on the underlying cause. For example, pneumonia would be treated with antibiotics while emphysema or COPD would be treated with nebulisation and steroids. The definitive treatment enables the reversal of the process that lead to respiratory failure. Certain diseases such as interstitial lung fibrosis may not be reversible with the currently available medical therapy and only a lung transplant could reverse the respiratory failure. In summary, respiratory failure is the consequence of multiple diseases when the lungs are unable to perform their functions. Treatment is supportive with oxygen and ventilators to provide a window of opportunity for effective treatment to take effect. Dr Hariprasad V S, Pulmonologist, MBBS, MD, DNB, MNAMS, DM, Apollo Hospitals, Bengaluru