This two-part unit discusses the use of non-invasive ventilation (NIV) in patients with respiratory failure, and in particular that associated with COPD.
- This article has been double-blind peer reviewed
- Figures and tables can be seen in the attached print-friendly PDF file of the complete article found under “related files”
VOL: 103, ISSUE: 39, PAGE NO: 26
Donna Barnes, BA, RGN, is staff nurse, Pilgrims Hospice, Canterbury
This two-part unit discusses the use of non-invasive ventilation (NIV) in patients with respiratory failure, and in particular that associated with COPD. Part 1 examines how an exacerbation of COPD can lead to hypercapnic respiratory failure and how this might be managed.
There are approximately 900,000 diagnosed cases of COPD in the UK and this is likely to be an underestimate (Booker, 2005). Data from ‘good-quality’ randomised controlled trials has shown the benefits of NIV for COPD-associated respiratory failure when used alongside traditional medical therapies (Booker, 2005; Ram et al, 2005; Stevens, 2005). NIV refers to ventilatory support provided by the delivery of pressurised gas via the upper airway, generally using a mask (Preston, 2001). It can therefore avoid the problems associated with intubation and conventional mechanical ventilation.
NIV is becoming more common (Chapman and Davies, 2003; Ram et al, 2005) and is increasingly undertaken outside specialist units by general nurses (British Thoracic Society, 2002; Gibbons and Milner, 2002). Nurses who have little experience of NIV have described it as ‘stressful’ and ‘frightening’ (Sawkins, 2001). There is therefore a need for literature that sheds light on care in NIV. This article focuses on nursing care of the NIV patient with COPD-related respiratory failure on an acute medical ward.
COPD AND RESPIRATORY FAILURE
NIV has been shown to be a particularly effective treatment for COPD-related respiratory failure (BTS, 2002; Del Castillo et al, 2003; Ram et al, 2005). In order to know how NIV helps, it is important to have an understanding of the associated physiology.
COPD includes those respiratory disorders that involve some airflow obstruction, for example chronic bronchitis, emphysema and bronchiectasis (Edmond, 2000, in Alexander et al, 2000). COPD is a progressive condition associated with an abnormal inflammatory response of the lungs to noxious substances, for example nicotine or coal dust (Booker, 2005). The airflow obstruction may be caused by all or some of the following: excessive secretions partially blocking the airways; oedematous thickening of the walls decreasing the diameter of the airways; and with emphysema the normally elastic alveolar walls becoming over-distended and collapsing inward, narrowing the airways (Edmond, 2000, in Alexander et al, 2000). Symptoms such as a cough, phlegm and shortness of breath may be present much of the time, having a significant impact on the person’s lifestyle (Marieb, 2000).
Impact on quality of life
As the condition progresses, airway resistance increases and these symptoms may become worse and present even at rest. The patient can become weaker due to constant respiratory effort and unable to undertake basic activities of daily living (Edmond, 2000, in Alexander et al, 2000). Their ability to participate in social activities and employment can be severely restricted and personal relationships can suffer, making social isolation a real risk (Booker, 2005). Additionally, COPD sufferers are vulnerable to more frequent and severe bouts of pulmonary infections. These exacerbate their usual symptoms and further impair airflow and gaseous exchange which, if severe, can necessitate a hospital admission (Marieb, 2000).
MANAGEMENT OF EXACERBATIONS
The management of infective exacerbation of COPD focuses on relieving symptoms, treating the underlying infection and preventing deterioration (Edmond, 2000, in Alexander et al, 2000). During the acute period, nursing care includes regular monitoring of vital signs. These might be taken hourly initially, graduating to four-hourly if improvement is seen. Special attention should be paid to respiratory effort. The rate, rhythm and depth of breathing should be observed and use of accessory muscles, wheezing and level of fatigue noted. If there are signs of deterioration, for example if the patient becomes drowsy, increasingly confused or appears cyanosed (Booker, 2005), the medical team should be informed.
Ensuring that the patient is in an upright position will aid ventilation by opening the airways (Edmond, 2000, in Alexander et al, 2000). Medication should be administered as prescribed, with peak flow measurements taken to monitor the efficacy of nebulised or inhaled bronchodilators (Esmond, 2001).
It is important to ensure the patient eats and drinks regularly. COPD patients are often malnourished because eating can exacerbate breathlessness. The approach of ‘little and often’ may be more manageable than full meals, so high-calorie snacks and supplementary drinks should be offered regularly (Esmond, 2001). Nurses should consider a referral to the dietitian for guidance, particularly if the patient has a low BMI (NICE, 2004).
Other agencies with whom nurses should consider liaising include the physiotherapy team for breathing techniques and sputum clearance (NICE, 2004). The critical care outreach team is often informed about the patient if deterioration occurs and supported ventilation is a possibility. After the acute period, occupational therapists may need to assess whether household aids might help patients manage better and the community respiratory team should be informed for post-discharge follow-up (Esmond, 2001).
Patient support and communication
Nurses should also ensure the patient and family are kept informed about the care plan. The psychosocial stress of this chronic condition cannot be understated. In the acute period, patients will need considerable support to combat the anxiety associated with severe breathlessness and their fears for the future (Esmond, 2001). As the patient improves, nurses can assess their knowledge of the condition and how they are coping. Leaflets can be an effective way to educate patients as they will have more time to digest the information. The British Lung Foundation produces several on COPD and may be a source of support for the family (further information can be found at www.lunguk.org).
Some exacerbations of COPD can be so severe that the effort of breathing exhausts the patient and respiratory failure becomes a possibility. This can be a terrifying time for patients as they fight for breath and experience symptoms of acute confusion, cyanosis and tachypnoea (Booker, 2005). They expend more oxygen with the increased effort, leaving even less for their organs and tissues (Woodrow, 2004). On admission to hospital, investigations will generally include a chest X-ray, ECG, full blood count, urea and electrolytes, blood cultures, sputum culture and arterial blood gases (Booker, 2005).
An arterial blood gas (ABG) sample typically shows that the patient has low oxygen levels (hypoxia) and high carbon dioxide levels (hypercapnia) (Woodrow, 2004). ABG analysis is a crucial part of managing the NIV patient. It provides an objective evaluation of oxygenation, ventilation and acid-base balance and so gives a picture of how well the respiratory system is working (Allen, 2005).
ARTERIAL BLOOD GASES
In the UK, oxygen and carbon dioxide concentrations are measured in kilopascals (kPa), and their normal ranges are 11.5-13.0kPa and 4.5-6.0kPa respectively (Allen, 2005).
Carbon dioxide removal depends on the size and frequency of breaths (Woodrow, 2003). The tense, shallow breaths of the COPD patient experiencing an exacerbation are insufficient to efficiently exhale carbon dioxide. When carbon dioxide mixes with water in the blood it forms carbonic acid. Too much of the gas therefore disturbs the acid-base balance of the blood. This is measured using the pH scale and the normal range for the body to work effectively is 7.35-7.45 (Allen, 2005).
Hypercapnia may cause blood pH to drop below 7.35, a life-threatening situation as enzyme activity, cardiac contraction and oxygen disassociation are all affected by only slight changes in pH (Woodrow, 2004). A patient with rising carbon dioxide levels may complain of headache, lethargy, drowsiness and sweating (Allen, 2005), so these are key symptoms to look out for in COPD.
Woodrow (2004) provides a more detailed discussion of ABGs that may be useful.
Types of respiratory failure
Bronchial oedema and respiratory secretions also worsen during an exacerbation of COPD. They increase the impermeability of the fluid barrier between alveolar air and pulmonary blood, further impairing gaseous exchange and aggravating the already chronically reduced oxygen levels (Woodrow, 2004).
ABG results showing oxygen levels of less than 8kPa and carbon dioxide levels of more than 6kPa are sometimes described as type two or hypercapnic respiratory failure. Type one or hypoxic respiratory failure is characterised by oxygen levels of less than 8kPa with normal or low carbon dioxide levels (Woodrow, 2004). This tends to be treated with continuous positive airway pressure rather than bi-level NIV and so will not be discussed further in this unit.
The management of type two respiratory failure caused by COPD exacerbation aims to correct the patient’s hypoxia and hypercapnia.
- Part 2 of this unit, which discusses how NIV can help the respiratory system to return to homeostasis, will be published next week. It also gives an overview of nursing care during NIV.
1. Know the main symptoms associated with COPD and understand the psychological effects of living with the disease.
2. Know the main nursing actions that are involved in caring for a patient with an exacerbation of COPD.