Prognostic Value of Hypercapnia in Patients with Chronic Respiratory Failure during Long-term Oxygen Therapy

Abstract

Hypercapnia observed in patients with chronic respiratory failure may not be an ominous sign for prognosis when they are receiving long-term oxygen therapy (LTOT). In this study, we selected 4,552 patients with chronic obstructive pulmonary disease (COPD) and 3,028 with sequelae of pulmonary tuberculosis (TBsq) receiving LTOT from 1985 to 1993 throughout Japan and prospectively analyzed their prognoses. The hypercapnic patients (PaCO2 >= 45 mm Hg) had a better prognosis than the normocapnic patients (35 <= PaCO2 < 45 mm Hg) for TBsq, but no difference was found between the two groups with COPD. Furthermore, Cox's proportional hazards model revealed that in TBsq hypercapnia was an independent factor for favorable prognosis, and that the relative risk for mortality was 0.76 in patients with 45 <= PaCO2 < 55 mm Hg, 0.64 for those with 55 <= PaCO2 < 65 mm Hg, and 0. 49 for patients with PaCO2 >= 65 mm Hg against normocapnic patients. This favorable effect of hypercapnia in TBsq was particularly apparent in the patients without severe airway obstruction. Even a rise of 5 mm Hg or more in PaCO2 over the initial 6- to 18-mo follow-up period was not associated with poor prognosis in TBsq, although it was in COPD. From these findings, we conclude that hypercapnia should not be generally considered an ominous sign for prognosis in those patients who receive LTOT.

Long-term Oxygen Treatment in Chronic Obstructive Pulmonary Disease: Recommendations for Future Research

“…Median survival in those using O 2 for 18 hours/day was approximately twofold longer than in those receiving no O 2 . Survival curves for O 2 -treated subjects in subsequent uncontrolled studies have generally produced results that are consistent with the data from similarly treated groups of the NOTT and MRC studies (8)(9)(10)(11)(12)(13).…”

Physiological changes during low- and high-intensity noninvasive ventilation

“…Presently, it is unclear whether hypercapnia per se influences the survival of these patients [5,18,19]. Moreover, potential adverse consequences of Hi-NPPV include diaphragm atrophy due to complete rest [20], as suggested by the near abolition of the Pdi signal seen in most patients; the risk of this seems minimal, however, considering that the respiratory muscles of patients with severe COPD seem to be resistant to fatigue compared with normal subjects [21] and patients using Hi-NPPV are still breathing spontaneously most of the time, which should minimise atrophy [22].…”

Noninvasive ventilation in chronic ventilatory failure due to chronic obstructive pulmonary disease

“…Hypercapnia is a poor prognostic sign in COPD [28,29] and is a marker for a lack of benefit from oxygen therapy [26]. However, a study from Japan of 4,552 patients with obstructive lung disease did not show any difference in outcome between patients with hypercapnia and those who were normocapnic [30]. Indeed, hypercapnic patients who had had a thoracoplasty had a better prognosis than those who were normocapnic.…”