Outcome of COPD patients with mild daytime hypoxaemia with or without sleep-related oxygen desaturation

The aim of the present study was to compare the evolution of pulmonary haemodynamics and of arterial blood gases in chronic obstructive pulmonary disease (COPD) patients with mild-to-moderate hypoxaemia, with or without sleep-related oxygen desaturation. COPD patients with daytime arterial oxygen partial pressure in the range 56-69 mmHg were included prospectively. Sleep-related oxygen desaturation was defined as spending greater than or equal to 30% of the nocturnal recording time with arterial oxygen saturation < 90%. From the 64 patients included, 35 were desaturators (group 1) and 29 were nondesaturators (group 2). At baseline (to), patients with sleep-related desaturation had a significantly higher daytime (mean +/- SD) arterial carbon dioxide partial pressure (Pa,CO2) (44.9 +/- 4.9 mmHg versus 41.0 +/- 4.1 mmHg, p = 0.001) whereas mean pulmonary artery pressure (mPAP) was similar in the two groups. After 2 yrs (t2) of followup, 22 desaturators and 14 nondesaturators could be re-evaluated, including pulmonary haemodynamic measurements. None of the nondesaturator patients became desaturators at t2. The difference between the two groups in terms of daytime Pa,co, was still present at t2. The mean changes in mPAP from to to t2 were similar between the two groups, as were the rates of death or requirement for long-term oxygen therapy (American Thoracic Society criteria) during follow-up of up to 6 yrs. The presence of sleep-related oxygen desaturation is not a transitional state before the worsening of daytime arterial blood gases, but is a characteristic of some chronic obstructive pulmonary disease patients who have a higher daytime arterial carbon dioxide partial pressure. Such isolated nocturnal hypoxaemia or sleep-related worsening of moderate daytime hypoxaemia does not appear to favour the development of pulmonary hypertension, nor to lead to worsening of daytime blood gases

Sleep-related O2 desaturation and daytime pulmonary haemodynamics in COPD patients with mild hypoxaemia

It has been hypothesized but not firmly established that sleep-related hypoxaemia could favour the development of pulmonary hypertension in chronic obstructive pulmonary disease (COBB) patients without marked daytime hyperaemia, We have investigated the relationships between pulmonary function data, sleep-related desaturation and daytime pulmonary haemodynamics in a group of 94 COPD patients not qualifying for conventional O-2 therapy (daytime arterial oxygen tension (Pa,O-2) in the range 7.4-9.2 kPa (56-69 mmHg)), Nocturnal desaturation was defined by spending greater than or equal to 30% of the recording time with a transcutaneous O-2 Saturation <90%. An obstructive sleep apnoea syndrome was excluded by polysomnography, Sixty six patients were desaturators (Group 1) and 28 were nondesaturators (Group 2). There was no significant difference between Groups 1 and 2 with regard to pulmonary volumes and Pa,O-2 (8.4+/-0.6 vs 8.4+/-0.4 kPa (63+/-4; vs 63+/-3 mmHg)) but arterial carbon dioxide tension (Pa,CO2) was higher in Group 1 (6.0+/-0.7 vs 5.3+/-0.5 kPa (45+/-5 vs 40+/-4 mmHg); p) was very similar in the two groups (2.6+/-0.7 vs 2.5+/-0.6 kPa (19+/-5 vs 19+/-4 mmHg)). No individual variable or combination of variables could predict the presence of pulmonary hypertension. It is concluded that in these patients with chronic obstructive pulmonary disease with modest daytime hypoxaemia, functional and gasometric variables (with the noticeable exception of arterial carbon dioxide tension) cannot predict the presence of nocturnal desaturation; and that mean pulmonary artery pressure is not correlated with the degree and duration of nocturnal hypoxaemia. These results do not support the hypothesis that sleep-related hypoxaemia favours the development of pulmonary hypertension

A randomized trial of nocturnal oxygen therapy in chronic obstructive pulmonary disease patients

The beneficial effects of nocturnal oxygen therapy (NOT) in chronic obstructive pulmonary disease (COP) patients with mild-to-moderate daytime hypoxaemia (arterial oxygen tension (Pa,O-2) in the range 7.4-9.2 kPa (56-69 mmHg)) and exhibiting sleep-related oxygen desaturation remains controversial, The effectiveness of NOT in that category of COP patients was studied. The end points included pulmonary haemodynamic effects after 2 yrs of follow-up, survival and requirement for long-term oxygen therapy (LTOT). Seventy-six patients could be randomized, 41 were allocated to NOT and 35 to no NOT (control), The goal of NOT was to achieve an arterial oxygen saturation of >90% throughout the night. All these patients underwent polysomnography to exclude an associated obstructive sleep apnoea syndrome. The two groups exhibited an identical mean SD, daytime Pa,O-2 of 8.4+/-0.4 kPa (63+/-3 mmHg) at baseline. Twenty-two patients (12 in the NOT group and 10 in the control group, p=0.98) required LTOT during the whole follow-up (35+/-14 months). Sixteen patients died, nine in the NOT group and seven in the control group (p=0.84). Forty-six patients were able to undergo pulmonary haemodynamic re-evaluation after 2 yrs, 24 in the NOT and 22 in the control group. In the control group, mean resting pulmonary artery pressure increased from 19.8+/-5.6 to 20.5+/-6.5 mmHg, which,vas not different from the change in mean pulmonary artery pressure in the NOT group, from 18.3+/-4.7 to 19.5+/-5.3 mmHg (p=0.79). Nocturnal oxygen therapy did not modify the evolution of pulmonary haemodynamics and did not allow delay in the prescription of long-term oxygen therapy No effect of NOT on survival was observed, but the small number of deaths precluded any firm conclusion. These results suggest that the prescription of nocturnal oxygen therapy in isolation Is probably not justified in chronic obstructive pulmonary disease patients