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Oxygen therapy could improve survival in patients with early desaturation in the 6‐minute walk test: A post hoc analysis

2024; Wiley; Volume: 29; Issue: 4 Linguagem: Inglês

10.1111/resp.14688

1440-1843

Ignacio García‐Talavera, Juan Marco Figueira Gonçálves, Cristóbal Esteban, Rafael Golpe, Silvia García‐Talavera, Carlos Antonio Amado Diago, Amaia Arámburu, Lina Pérez‐Méndez, Alicia Conde‐Martel,

High Altitude and Hypoxia

Long-term domiciliary oxygen therapy (LTDOT) in patients with chronic obstructive pulmonary disease (COPD) has been shown to increase survival when associated with severe hypoxaemia at rest,1, 2 but not when accompanied by moderate hypoxaemia at rest.3, 4 However, the benefits of LTDOT in patients with COPD and moderate hypoxaemia at rest and with desaturation during exercise are unknown, although its use is currently recommended when accompanied by improved dyspnoea or exercise capacity.5, 6 A recent study failed to show an increase in survival in these patients,7 although the importance of the pattern of desaturation during the 6-minute walk test (6MWT) was not assessed. Our group recently published a study in which we observed that patients with COPD and early desaturation—that is, a drop in SpO2 0.05, Table 1). Mean follow up time for the entire group was 4.48 ± 2.97 years. Mean follow up time for the no LTDOT group was 3.86 ± 2.70 and 6.42 ± 2.99 years for LTDOT group. Overall survival was 27.5% (n = 28), but with noticeable differences between groups (76% LTDOT vs. 11. 7% non-LTDOT), reflected in the cumulative survival and a hazard ratio of 6.2 (Figure 1). Survival time was 4.24 ± 0.39 years for the group without LTDOT and 11.83 ± 1.12 years for the LTDOT group. Our findings are novel. Cranston et al.3 did not find any benefits of domiciliary oxygen therapy in patients with mild to moderate hypoxaemia or those with nighttime only desaturation; however, the impact of desaturation during exercise was not analysed. Similarly, in a meta-analysis Laccasse et al.,4 found no difference in 3-year mortality in patients with COPD and moderate hypoxaemia managed with or without long-term oxygen therapy, but again the potential influence of exercise desaturation was not analysed. A more recent, large randomized controlled trial analysed outcomes of long-term oxygen therapy in COPD patients with moderate resting or exercise induced desaturation.7 Again, no significant difference in mortality or other clinical outcomes were found between groups. While the severity of desaturation including saturation nadir during exercise was considered in the analysis, the desaturation pattern (i.e., the timing of desaturation within the 6MWT) was not. In contrast, our current findings suggest that long-term domiciliary oxygen therapy in patients with COPD and early desaturation during the 6MWT may improve survival. While we do not have a clear explanation for the observed improvement in survival, one possibility is a reduction in frequent, intermittent desaturation these individuals may experience during everyday activities. By minimizing intermittent hypoxaemia with LTDOT, oxidative stress and dysregulation of hypoxia-inducible factors9 may be slowed, improving survival. In an earlier study by our group, we found that patients who desaturated within the first minute of the 6MWT had a 74% probability of also desaturating during activities of daily living.10 In contrast, those who desaturated 3.5 min or more after starting the walking test were unlikely to desaturate during everyday activities. There are a number of limitations that need to be considered when interpreting these preliminary findings. This was a subgroup analysis from a larger observational study of patients with COPD and moderate or severe hypoxaemia. Although no differences in clinical or functional baseline parameters between the two ED groups were seen, there many have been other confounders not accounted for due to the methodological approach used, influencing outcomes. The decision to prescribe LTDOT or not to these ED patients who did not meet typical guideline-based criteria for home oxygen therapy was at the discretion of the treating physician, and we do not have sufficient details to explore the factors influencing this decision. However, the reasons some patients were prescribed LTDOT and others were not may have contributed to the difference in survival times seen. Further, while patients were asked to use oxygen therapy >15 h/day, we have no objective evidence of adherence to this prescription. We believe these findings are novel and provide compelling support to undertake further investigation into the value of the temporal occurrence of oxygen desaturation during the 6MWT in patients with COPD who would not otherwise qualify for domiciliary oxygen therapy based on current international clinical guidelines.5, 6 In addition to confirming this apparent improvement in survival rates through the use of a more rigorous study design, it would be important to explore any other beneficial clinical or patient-centred outcomes such as exacerbation rates, development of comorbidities and quality of life with the use of LTDOT in patients with COPD and early desaturation during 6MWT. Ignacio García-Talavera: Conceptualization (equal); data curation (equal); supervision (lead); validation (equal); writing – original draft (equal); writing – review and editing (equal). Juan Marco Figueira-Gonçalves: Conceptualization (equal); data curation (equal); formal analysis (equal); validation (equal); writing – review and editing (equal). Cristobal Esteban: Formal analysis (equal); methodology (supporting); validation (equal); writing – review and editing (equal). Rafael Golpe: Formal analysis (equal); methodology (supporting); validation (equal); writing – review and editing (equal). Silvia García-Talavera: Formal analysis (equal); investigation (equal); validation (equal); visualization (equal); writing – original draft (equal); writing – review and editing (equal). Carlos Amado: Formal analysis (equal); methodology (lead); validation (equal); writing – review and editing (equal). Amaia Aramburu: Investigation (equal); methodology (supporting); validation (supporting); writing – review and editing (equal). Lina I. Pérez-Méndez: Methodology (lead); software (equal); writing – review and editing (equal). Alicia Conde-Martel: Formal analysis (equal); methodology (supporting); validation (lead); visualization (equal); writing – review and editing (lead). The authors declare that no funds, grants or other support was received during the preparation of this publication. None declared. This study was approved by the Ethics Committee of Research with medicines of the Canary Islands University Hospital Complex (Province of Santa Cruz de Tenerife). The confidentiality of personal data were guaranteed, and Informed Consent was waived. The capacity of the researchers and the available means were adequate to carry out the study and did not interfere with respect for ethical postulates. In addition, the Drug Research Ethics Committee of the Canary Islands University Hospital Complex (Province of Santa Cruz de Tenerife) issued a FAVOURABLE opinion for carrying out this study at the Nuestra Señora de Candelaria University Hospital. The data that support the findings of this study are available from the corresponding author upon reasonable request.