Combined Oximetry-Cutaneous Capnography in Patients Assessed for Long-term Oxygen Therapy

Study aimTo 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.MethodsTwenty 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.ResultsThe 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%.ConclusionCombined 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.