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).
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 >.