The Effect of Intermittent. Negative Pressure Ventilation and Long-term Oxygen Therapy for Patients With COPD – Conclusion
Therefore, the identification of an accelerated phase of respiratory failure is prog-nostically important. In fact, in this phase, other therapeutic measures (such as some form of intermittent mechanical ventilatory assistance) other than LTOT have been suggested to control the evolution of the disease.
In our patients treated with LTOT, the rate of decline of Pa02 over time as well as the rate of increase of PaC02 were less pronounced than those reported by Cooper and Howard. The life expectancy of our patients was very poor because they had had an episode of ARF requiring mechanical ventilation and also because they subsequently experienced several relapses of ARF. Despite this, the worsening of the respiratory function was relatively slight. One possible explanation is that all of our patients but one stopped smoking at the beginning of the follow-up. It is well known that FEVX is highly correlated with survival and that it decreases faster in smokers than in nonsmokers or ex-smokers. Stopping smoking reduces the decline of FEVX to the level found in nonsmokers. A lower survival rate has been reported in patients with COPD receiving LTOT who continued smoking compared with those who stopped. However, if one compares the survival rate at 2 years of our patients receiving LTOT with that of the nonsmokers of the Swedish study, the difference in favor of our group is considerable (86 percent vs 55 percent). Thus, other factors could have influenced the slight worsening of the respiratory function found in our patients.
To speculate further on this subject, it should be noted that the only difference in terms of therapy between our patients receiving LTOT and those of other studies was the ventilatory treatment we applied. Thus, it can be thought that our patients benefited, to some extent, from the noninvasive ventilatory treatment used both for the initial acute episode and for the subsequent relapses of ARF. This hypothesis is in keeping with the results of our recent study showing that the application of the iron lung to this type of patient can improve survival both in the short and in the long term.
In conclusion, our study suggests that LTOT can improve the survival of patients with COPD after a bout of ARF treated with mechanical ventilation and that the association of LTOT with a noninvasive ventilatory system can modify positively the long-term prognosis of these patients. While the addition of LTOT to a therapeutic approach based on the use of INPV for treating acute episodes of respiratory failure seems to be beneficial, controlled clinical studies are still needed to compare long-term survival following intubation with mechanical ventilation versus noninvasive modes of ventilation.