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An audit of provision of long-term oxygen therapy for COPD patients

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Denise Gibbons, RN, MA.

Advanced Practice Respiratory Nurse Specialist, South Tyneside Health Care Trust

Chronic obstructive pulmonary disease (COPD) is a major cause of ill health and death in adults. There is no explicit definition of COPD. It is, however, an umbrella term for a group of diseases, which include asthma, chronic bronchitis and emphysema (Bourke and Brewis, 1999). There are at least 600 000 people in the UK with COPD, a prevalence of about 1% (Calverly and Bellamy, 2000).

Chronic obstructive pulmonary disease (COPD) is a major cause of ill health and death in adults. There is no explicit definition of COPD. It is, however, an umbrella term for a group of diseases, which include asthma, chronic bronchitis and emphysema (Bourke and Brewis, 1999). There are at least 600 000 people in the UK with COPD, a prevalence of about 1% (Calverly and Bellamy, 2000).

As the disease progresses, many patients with COPD develop low arterial oxygen levels (hypoxaemia) even when they are clinically stable. This is a poor prognostic feature independent of the severity of the disease indicated by the patient’s FEV1 (Forced Expiratory Volume in the first second) (Calverly, 2000). Chronic hypoxaemia results in a number of detrimental physiological changes (Box 1). If left untreated the five-year survival rate of these patients is less than 50% (Halpin, 2001).

 

The role of long-term home oxygen therapy
Two large prospective multi-centre studies document the use of long-term home oxygen therapy (LTOT) as a treatment strategy for patients with COPD. The aim is to deliver oxygen therapy for a minimum of 15 hours a day. Benefits include the amelioration of symptoms associated with chronic hypoxaemia (Box 1). In addition to this, a reduction in mortality and hospitalisation rates, and improved quality of life for patients have also been observed (Medical Research Council, 1981; Nocturnal Oxygen Therapy Trial Group, 1980).

Criteria for the prescription of LTOT in the UK have been established based on the results of these studies (Box 2). LTOT should also be prescribed in patients who demonstrate a Pa02 (partial pressure of arterial oxygen) of between 7.3kPa (kilopascalles) and 8kPa with secondary polycythaemia, nocturnal hypoxia, peripheral oedema or evidence of pulmonary arterial hypertension (Halpin, 2001).

In England and Wales LTOT can be prescribed by a GP, but it is recommended that the patient is initially assessed by a respiratory physician. In Scotland LTOT is prescribed by a respiratory physician. The patient should be assessed when clinically stable (Box 3) and receiving optimal treatment dependent on the severity of their disease.

The guidelines recommend re-evaluation one to three months after the initial prescription for LTOT and thereafter re-assessment every six months. However, a study by Ringbaek et al (2001) indicated poor adherence to guidelines for initial prescription and subsequent re-assessment.

 

Audit aims
The aims of this audit were to:

- Assess the quality of the initial LTOT assessment

- Identify those patients who required a change in their oxygen therapy prescription

- Analyse the knowledge and understanding of equipment among those patients currently prescribed LTOT in South Tyneside.

 

Methods
All patients being prescribed LTOT in South Tyneside were identified from the oxygen therapy company database (Box 4). The respiratory nurse then reviewed the patients in the outpatient clinic. All patients were clinically stable at the time of assessment. The assessment consisted of the monitoring of arterial blood gases on room air and current prescribed rate of oxygen. In addition to this the respiratory nurse conducted a structured interview to collect data regarding the patient’s knowledge and understanding of their disease and the use and care of the equipment (Box 5).

Patients who failed to attend for their appointment were visited at home. Oxygen saturation was measured on air and the prescribed rate of oxygen from the concentrator using a portable pulse oximeter. A database was then set up to collect concurrent information from the assessments. Following re-assessment several patients required changes to their prescriptions (Box 6).

 

Discussion
The prescription of oxygen for use in the home has been developed over the past 50 years (Wedzicha, 1999). Home oxygen therapy is available in three forms:

- Stationary oxygen concentrators

- Compressed gas in metal cylinders in various sizes

- Liquid oxygen in lightweight portable containers

Concentrators use mains electricity and the cost (approximately two pence per hour) is reimbursed to the patient by the contracted supplier. An oxygen cylinder is always provided as a back up for use should the concentrator fail mechanically or if there is an electrical power cut.

Oxygen concentrators became available on FP10 prescription in December 1985. The GP is responsible for prescribing the concentrator and the service is centrally funded by the Department of Health. The concentrator works by passing air through a series of filters into a molecular sieve containing zeolite crystals. This removes nitrogen and other low-concentration gases, thereby enriching the oxygen (Harman, 1999). Concentrators deliver between 24% and 31.5% oxygen dependent on the flow rate.

Oxygen is delivered either by nasal cannula or a Venturi barrel oxygen mask. A standard flow meter regulates the flow rate and can be set at up to four litres on one machine. More than one machine can be used to deliver a higher percentage, up to 60% with four machines. Oxygen points may also be installed into the patient’s home to reduce the need for excess tubing.

Oxygen cylinders have been used to deliver both LTOT and intermittent oxygen therapy (ITOT). They are available in three sizes:

- Standard cylinders (size F) contain 1360 litres of oxygen and last 10 hours at two litres (set to deliver two litres of oxygen per minute over a period of 10 hours)

- Portable cylinders lasting one hour 50 minutes at two litres

- Lightweight cylinders (PA2) last three hours 15 minutes at two litres.

All cylinders are available on FP10 prescription. The liquid oxygen (LOX) portable system allows up to eight hours of oxygen, but is not available on FP10 prescription.

Despite recommendations from the British Thoracic Society (BTS, 1997) patients are still being inappropriately prescribed LTOT (Box 5). Patients who were reassessed during the study did not meet the criteria for ongoing prescription. With education and support the oxygen therapy was successfully discontinued and these patients were referred for physiotherapy, education on breathing control and pulmonary rehabilitation.

Quality control - Several studies have indicated variability in assessments and prescribing of oxygen concentrators as well as poor adherence to guidelines, lack of follow-up and monitoring of patients. Communication between primary and secondary care specialists is also poor. (Wedzicha, 1999). This is supported by a study by Kampelmacher et al (1999), which indicated poor quality control among GPs initiating LTOT. This may be due to the fact that even in a large practice there may be only a few patients who require this treatment and therefore knowledge and experience is limited (Ringbaek et al, 2001).

Current prescribing guidelines advocate a change to an oxygen concentrator when monthly usage exceeds 21 oxygen cylinders (Heaney et al, 1999). Any patient using in excess of 21 oxygen cylinders per month should be referred to a respiratory physician. It is essential that their diagnosis is reviewed, their medication maximised for the severity of disease and an oxygen assessment is performed to calculate oxygen requirements. Under these circumstances the oxygen concentrator is installed without the patient undergoing an assessment to see whether or not he or she requires it.

Conversely, many patients who might benefit from LTOT are not referred for assessment. GPs therefore require more education on indications for LTOT referral. It has been suggested that primary care groups should introduce pulse oximeters to measure oxygen saturation to assist with the assessment of COPD (Calverly and Bellamy, 2000). A study by Roberts et al (1998) on the use of pulse oximetry in primary care concluded that using pulse oximetry was helpful in deciding when to refer to a chest physician for consideration for LTOT.

Eighty-one per cent of patients who had been re-assessed were prescribed LTOT following a hospital assessment. However, we were unable to extrapolate how many of those were prescribed following a hospital admission for an acute exacerbation. Many patients who are hypoxaemic during an exacerbation will recover over a few weeks and will not require oxygen therapy (Bourke and Brewis, 1999). Education for hospital doctors on organisation of often transient oxygen therapy to expedite hospital discharge is therefore needed (Guyatt et al, 2000).

Few hospitals measure the carboxyhaemoglobin level in order to assess the smoking status of the patient (Ringbaek et al, 2001). Continued smoking in patients receiving LTOT is a fire hazard. Despite this, 13% of those who were re-assessed continue to smoke.

 

If the patient is still active, mobile and able to leave the house, he or she should be provided with a portable oxygen system. However, only 38% of patients had portable cylinders. Portable oxygen should also be considered for patients who are not chronically hypoxaemic or on LTOT, but show evidence of oxygen desaturation on exercise to below 85%. However, these patients should first demonstrate an increase in exercise tolerance when using oxygen therapy (Wedzicha, 1999). The patient should therefore be assessed using the Shuttle Walk Test or the six-minute walking test and a pulse oximeter both with and without supplemental oxygen (Calverly, 2000).

Side-effects of LTOT - Adverse effects are rare if the patient is assessed thoroughly. For patients who are in a stable condition, progressive carbon dioxide retention is unlikely (Wegg and Hass, 1998). Using the lowest flow rate of oxygen therapy that results in an acceptable arterial oxygen level can further reduce the risk of this potential complication (Celli et al, 2000).

Dryness of the nasal or oropharangeal mucosa from using either nasal cannulae or an oxygen mask can be resolved by adding humidification to the system. Patients should also be advised to increase their oral fluid intake. If humidification is added, it is important to reduce the risk of infection by changing the water daily. Some patients complain that headaches make it difficult to comply with the treatment, while for others, the noise of the machine is an issue.

Treatment compliance - Compliance with the medical prescription can be calculated by comparing the daily use of LTOT; which can be worked out by the oxygen therapy company technician, and the number of hours of therapy prescribed by the physician. However, if the patient leaves the concentrator switched on while not using it, this will be inaccurate. Ringbaek et al 2001 identified that self-reported data from patients on oxygen consumption is often over-estimated. Many patients fail to reach the minimum requirement of 15 hours per day (Rees and Dudley, 1998).

Home visits from respiratory nurses can help to reinforce instructions as well as to identify side-effects and intolerance to treatment, which may lead to a reduced level of compliance. Despite the fact that 69% of patients had received education at the time of their initial prescription, patients demonstrated poor knowledge and understanding of the use and care of the concentrator. This emphasises that an initial explanation is not enough.

Before this study was undertaken, patients in South Tyneside were not recalled for re-assessment. It appears that this is not uncommon. Morrison et al (1995) identified in one study that only 56% of patients using LTOT had arterial gases repeated within 12 months of prescription.

Recommendations
Results from the audit have highlighted many areas for improvement. It is apparent that patients require a considerable amount of adjustment to the prescription of LTOT. It is therefore important to educate them adequately so they can cope with the treatment at home (Box 7).

Since the completion of the audit the following quality initiatives have been put in place to improve the service for patients:

- Education checklist for all new patients

- Home visit from a respiratory nurse for all new patients

- Yearly re-assessment for all patients

- Assessment of carboxyhaemaglobin levels in outpatient clinics

- A prescription for portable oxygen cylinders for all active patients

- All patients requiring home oxygen on discharge from hospital to be referred to the respiratory team.

Conclusion
Long-term oxygen therapy can reduce morbidity and mortality in COPD patients with chronic hypoxaemia. However, there is a need to provide ongoing support for patients to enable continuing education, monitoring of the patients’ condition and prevention of unnecessary complications.

Reassessment of arterial blood gases after the initial prescription is essential. Many patients require a change in prescription as their condition changes (Box 6). The greatest problem concerning adherence to guidelines is the prescribing of LTOT by the GP without the patient being assessed, or during periods of acute exacerbation. It is therefore vital that the issue of staff education on indications for referral is addressed.

 

 

 

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Kampelmacher, M.J., Van Kesteren, R.G., Alsbach, P.J. et al.Prescription and usage of long term oxygen therapy in patients with chronic obstructive pulmonary disease in the Netherlands. Respiratory Medicine (1999) 93: 46-51.

 

 

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Ringbaek, T.J., Lange, P., Viskum, K. (2001)Are patients on long-term home oxygen therapy followed up properly? Data from the Danish Register Journal of Internal Medicine 250: 131-136.

 

 

Roberts, C.M., Franklin, J., O’Neill, A. (1998)Screening patients in general practice with COPD for long-term oxygen domiciliary oxygen requirement using pulse oximetry. Respiratory Medicine 92: 1265-1268.

 

 

Wedzicha, J.A. (1999)Domiciliary oxygen therapy services: clinical guidelines and advice for prescribers. Journal of the Royal College of Physicians 33: 5, 445-447.

 

 

Wegg, J.G., Hass, F.C. (1998)Long-term oxygen therapy for COPD. Postgraduate Medicine 103: 4.

 

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