Long-term Oxygen Therapy Service and Prognosis - Literature review Example

Introduction Long-term oxygen therapy (LTOT) is an established treatment for patients with chronic respiratory insufficiency and chronic, stable hypoxemia (Weitzenblum, E et al 1995). The main goal of oxygen therapy is to relieve tissue hypoxia thereby reducing the level of pulmonary vasoconstriction in cases of respiratory disorders (Missov ED, De Marco T 2000). The majority of studies done to determine the efficacy of LTOT have been carried out in patients with chronic obstructive pulmonary disorder (COPD) (Weitzenblum, E et al 1995). As COPD progresses hypoxia may develop and LTOT is one of the ways by which oxygen therapy can be given to patients with stable hypoxia (Ruse, C 2008). Cor pulmonale, defined as hypertrophy, dilation, or dysfunction of the right ventricle due to pulmonary hypertension resulting form disorders of the respiratory system, also commonly occurs in patients with COPD (Missov ED, De Marco T 2000). There are evidences to support LTOT could significantly reduce mortality in patients with COPD and Cor pulmonale (Weitzenblum, E et al 1995, Croxton, TL 2006, Missov ED, De Marco T 2000, Zielinski, J 1998 ). Two randomized, controlled clinical trials have demonstrated the beneficial effects of LTOT in case of COPD and sever resting hypoxemia. They include the Nocturnal Oxygen therapy trial and the trials carried out by the Medical Research Council (Weitzenblum, E et al 1995, Barnett, M 2007, Croxton, TL 2006, Ruse, C 2008, Missov ED, De Marco T 2000). Both the trials indicated that oxygen therapy administered for at least 15 hours daily for patients with severe hypoxic COPD increased survival and in addition reduced polycythaemia and the progression of pulmonary hypertension (Barnett, M 2007). The main focus of LTOT is to improve the quality of life of the patients and thereby to increase their survival (Barnett, M 2007, Marti, S et al, 2006, Croxton, TL 2006). Indications and Criteria for LTOT The criteria for the initiation of LTOT in the UK have been established based on the results of the 2 trials mentioned above (Barnett, M 2007, Zielinski, J 1998). The criteria as per the National clinical guidelines include patients with an arterial oxygen tension (PaO2) consistently at or below 7.3 kPa (55 mm Hg or less) when clinically stable. This threshold value of 55 mmHg indicates presence of severe hypoxemia which may have deleterious effects on pulmonary circulation, brain function etc (Atis, S et al 2001). Patients, who have a PaO2 consistently between 7.3 and 8.0 or 7.5 and 7.8 when clinically stable and if pulmonary hypertension (PAP > 25mm Hg), polycythaemia (hematocrit > 55% ), peripheral oedema resulting from right heart failure or nocturnal hypoxemia is present with an SaO2 of less than 88%, may be prescribed LTOT (Barnett, M 2007, Zielinski, J 1998, http://cks.library.nhs.uk/clinical_topics, Atis, S et al 2001 ). LTOT may be given to patients with an arterial carbon dioxide tension (PaCO2) of 6kPa (45 mm Hg or more) or more and an arterial oxygen saturation (SaO2) of 88% or less (Missov ED, De Marco T 2000, Atis, S et al 2001) and to those who exhibit palliation of dyspnoea in terminal disease (Zielinski, J 1998). The above readings should be taken on two separate measurements at 3 weeks apart. The guidelines also recommend patients to a specialist LTOT clinic for assessment to ensure correct diagnosis. It has also been stressed that the patients be under a medical regimen (Atis, S et al 2001). Patients suitable for the study The inclusion criteria for selecting patients suitable for LTOT may vary from one country to another. However, in the two trials mentioned above the patients included had advanced COPD with marked hypoxemia with an average PaO2 of 50 mm Hg and who had often experienced right heart failure (Weitzenblum, E et al 1995) 1. The diagnosis of COPD in the patients is established by clinical assessment and pulmonary function testing. The respiratory parameters include FEV1 (forced respiratory volume in one second) less than 80% and FEV1 / FVC (forced vital capacity ratio) that is less than 70% (Marti, S et al, 2006) 3. Hence the widely accepted eligibility criterion for LTOT is a stable arterial oxygen tension below 7.3kPa (55 mmHg). In some countries this could vary between 7.3 to 8.0 or 7.5 to 7.8 along with other specific clinical signs (Weitzenblum, E et al 1995, Barnett, M 2007, Marti, S et al, 2006, Ruse, C 2008, Missov ED, De Marco T 2000, http://cks.library.nhs.uk/clinical_topics, Weitzenblum et al 2002). Generally the beneficial effects of LTOT were observed only in patients with severe COPD than those who had moderate to lower degrees of impairment (Weitzenblum, E et al 1995, Croxton, TL 2006, Zielinski, J 1998, http://cks.library.nhs.uk/clinical_topics). It has also been shown that women demonstrate a lesser response to LTOT compared to men (Zielinski, J 1998) and that patients who continue to smoke after initiation of LTOT will not derive any benefit from the treatment (Barnett, M 2007). There is also a possibility of a fire hazard if the patient smokes while taking LTOT (Weitzenblum et al 2002). LTOT service and prognosis Though several studies have indicated a better survival rate in patients taking LTOT (Weitzenblum, E et al 1995, Croxton, TL 2006), others indicate a poor life expectancy (40 to 48%) in patients taking LTOT (Marti, S et al, 2006, Missov ED, De Marco T 2000, http://cks.library.nhs.uk/clinical_topics). There are several factors such as lack of knowledge regarding its mechanism of action, indications for prescriptions and effects on patient outcomes and cost that prevent the actual benefits of LTOT from reaching the patients (Croxton, TL 2006). Medical coverage policies till date hold that only those who meet the inclusion criteria for LOTT will benefit from LTOT. The LOTT and MRC trials were carried out several years ago with only around 500 patients enrolled in the trial and with fewer women patients. Hence considering the heterogeneity of the COPD population, the two trials cannot represent all patients. Better inclusion criteria taking into account other measures of disease severity must be adopted before prescribing patients to LTOT, rather than the arterial oxygen criteria alone (Croxton, TL 2006). In addition the prescribing physician should be aware about the minimal duration of efficient LTOT that should be administered to patients, which is probably 18h per day rather than 16h (Weitzenblum, E et al 1995, Croxton, TL 2006, Atis, S et al 2001). Patients taking LTOT must be under observance as their compliance to the treatment is indicated to be poor thus reducing the beneficial effects of the treatment (Atis, S et al 2001). Another drawback of LTOT is that the patient taking it is required to remain in a stationary place thus limiting their daily activities. Hence the use of light weight, portable oxygen delivery systems should be made available at a cheaper price in order to make it accessible to all patients (Croxton, TL 2006). I addition people may also be embarrassed to use these devices in public. Effective counseling is needed to break this stigma by enlightening the huge benefits that could be got compared to the inconveniences (Croxton, TL 2006). Medical policies should include an insurance cover which would enable more people to gain access to this life saving device. Another important factor that would contribute to the success of the treatment is educating patients and physicians about the benefits and also the risks associated with the use of LTOT. The major risk is the fire hazard in case the patient smokes while taking LTOT. They must be properly educated on it (Atis, S et al 2001). The choice of the source of oxygen can be made in consultation with the patient, according to their comfort. This would give them more confidence on the use of oxygen concentrators. The oxygen delivery system must be regularly checked and a periodic validation of the flow is necessary (Croxton, TL 2006,Atis, S et al 2001). In addition, administration of LTOT in patients with moderate hypoxemia and those who desaturate during physical activity or during sleep should be considered, as early initiation of the treatment would help to provide better prognosis for the patients (Croxton, TL 2006). Most importantly sufficient follow-up is needed in order to ensure compliance of patients to the treatment (Atis, S et al 2001). A study carried out in Turkey found that pre-treatment education of patients and follow-up by the physician may increase the compliance rate in patients (Atis, S et al 2001). Reference: 1. Weitzenblum, E et al 1995, ‘The Scientific Basis for Long-term Oxygen Therapy in Patients with Chronic Hypoxemia’, in O’Donohue, WJ (ed), Long-Term Oxygen Therapy: Scientific basis and Clinical applications, Informa Health care, viewed 24 July 24, 2008. 2. Barnett, M 2007, Drug delivery: Domiciliary oxygen therapy, JCN online, vol. 21, no. 8, viewed 23 July, 2008. http://www.jcn.co.uk/journal.asp?MonthNum=08&YearNum=2007&Type=backissue&ArticleID=1087 3. Marti, S et al, 2006, Body Weight and Comorbidity predict mortality in COPD patients treated with oxygen therapy, Eur Respir J, 27, 689-696, viewed 24 July 2008, http://www.erj.ersjournals.com/cgi/content/full/27/4/689 4. Croxton, TL 2006, Long-term Oxygen Treatment in Chronic Obstructive Pulmonary Disease: Recommendations for Future Research, American Journal of Respiratory and Critical Care Medicine, vol.174, 373-378, viewed 20 July 2008, http://ajrccm.atsjournals.org/cgi/content/full/174/4/373 5. Ruse, C 2008, Current approaches to the management of COPD, Prescriber, 17-20, viewed on 21 July 2008. 6. Missov ED, De Marco T 2000,Cor Pulmonale, Current Treatment Options in Cardiovascular Medicine, 2, 149-158, viewed 24 July 2008. 7. Rabe, KF 2007, Update in Chronic Obstructive Pulmonary Disease 2006, American Journal of Respiratory and Critical Care Medicine, vol 175, 1222-1232, http://ajrccm.atsjournals.org/cgi/content/full/175/12/1222 8. Zielinski, J 1998, Long-term oxygen therapy in patients with moderate hypoxemia: does it add years to life?, Eur Respir J, 12, 756-758. 9. CKS safe practical clinical answers, Chronic Obstructive Pulmonary Disease Management, http://cks.library.nhs.uk/clinical_topics 10. Weitzenblum et al 2002, Long-term oxygen therapy, in Similowski T et al (ed) Clinical management of chronic obstructive pulmonary disease, Informa Health Care, viewed 24 July 2008. 11. Atis, S et al 2001, Characteristics and compliance of patients receiving long-term oxygen therapy in Turkey, Monaldi Arch Chest Dis, 56(2), 105-9. http://www.ncbi.nlm.nih.gov/pubmed/11499295?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=2&log$=relatedarticles&logdbfrom=pubmed Read More