Study aim: To evaluate the feasibility of combined oximetry (pulse oximetric saturation [Spo2]) and cutaneous capnography (transcutaneous carbon dioxide tension [Ptcco2]) for oxygen titration in patients requiring long-term oxygen therapy.
Methods: Twenty patients with obstructive or restrictive lung disease underwent oxygen titration using a combined cutaneous oximetry-capnography sensor. The goal of titration was to achieve an oxygen saturation of > 90% without a significant rise in carbon dioxide. Spo2 and Ptcco2 measurements at the end of titration were compared with blood gas levels using Bland-Altman analysis and linear regression analysis.
Results: The mean (± SE of the estimate) Pao2 while breathing room air was 53.2 ± 8.1 mm Hg and increased to 75.9 ± 13.3 mm Hg with oxygen supplementation (p < 0.0001). The mean Paco2 was 45.9 ± 8.7 mm Hg at baseline and 47.8 ± 9.0 mm Hg after oxygen titration (p = 0.003). Bland-Altman analysis for comparison of Ptcco2 and Paco2 showed a bias of 0.86 mm Hg with a precision of 3.48 mm Hg. Bland-Altman analysis for the comparison of Spo2 and arterial oxygen saturation showed a bias of 0.14% with a precision of 1.13%.
Conclusion: Combined oximetry and cutaneous capnography is feasible during oxygen titration in patients needing long-term oxygen therapy. This noninvasive approach has the potential to reduce the number of arterial blood gas samplings performed.