Measurement of combined oximetry and cutaneous capnography during flexible bronchoscopy

Abstract

The aim of the present study was to assess the feasibility of measuring combined arterial oxygen saturation measured by pulse oximetry (S_p,O2) and cutaneous carbon dioxide tension (P_c,CO2) to monitor ventilation and quantify change in P_c,CO2 during bronchoscopy.

Combined S_p,O2 and P_c,CO2 were measured at the ear lobe in 114 patients. In four patients, the ear-clip slipped and they were excluded. In total, 11 patients had artefacts with S_p,O2 recordings, thus, S_p,O2 was analysed in 99 patients. Spirometry data were available in 77 patients. Multivariate analysis of covariance and logistic regression were used for statistical analyses.

Mean baseline P_c,CO2 was 4.78±1.06 kPa (36±8 mmHg) and mean rise in the P_c,CO2 during bronchoscopy was 1.26±0.70 kPa (9.5±5.3 mmHg), while mean P_c,CO2 at the end of bronchoscopy was 5.85±1.19 kPa (44±9 mmHg) . Baseline P_c,CO2 and the lowest S_p,O2 were significantly associated with peak P_c,CO2 and the change in P_c,CO2 during bronchoscopy. Risk of significant hypoxaemia (S_p,O2≤90%) was lower for a higher baseline S_p,O2. Peak P_c,CO2 was directly associated with significant hypoxaemia. There was no significant association in the baseline P_c,CO2, peak P_c,CO2, baseline S_p,O2 or the lowest S_p,O2 comparing patients with and without chronic obstructive pulmonary disease.

In conclusion, it is feasible to measure combined pulse oximetry and cutaneous carbon dioxide tension effectively to monitor ventilation during flexible bronchoscopy.