Internal medicine journal · 2015
Blood oxygen equilibration time after cessation of supplemental oxygen in chronic respiratory disease.
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Stone A M C, Wong K K H, Barnes D J
Аннотация
BACKGROUND: Measurement of the arterial partial pressure of oxygen (PaO2 ) while breathing air is an informative investigation in patients with hypoxaemia due to chronic respiratory disease, but there are a lack of published data on the time needed for blood oxygen levels to equilibrate after cessation of supplemental oxygen (O2 ) in such patients.
AIM: To determine the blood oxygen equilibration time after cessation of O2 and thereby provide guidance on best timing of baseline arterial blood gas analysis in this population.
METHODS: Medically stable subjects with chronic respiratory disease were administered O2 at a constant concentration. Continuous pulse oximetry was recorded from before cessation of O2 to beyond the point of oxygen saturation (SpO2 ) equilibration. Data were fitted to an exponential decay model. Blood oxygen equilibration time was defined as the t90, the time taken for SpO2 to fall 90% of the difference between initial (on O2 ) and final (on air) values.
RESULTS: Eighty-two (82) subjects with a mean age of 66 years were included. The largest diagnostic category was chronic obstructive pulmonary disease (37), followed by interstitial lung disease (15) and bronchiectasis (12). The median t90 was 6 min 18 s (interquartile range: 4 min 32 s-10 min 30 s). The 95th centile t90 value was 20 min.
CONCLUSION: In the majority of patients with chronic respiratory disease, a time delay of 20 min between cessation of supplemental O2 and PaO2 measurement allows confidence that the result is a true baseline value.
AIM: To determine the blood oxygen equilibration time after cessation of O2 and thereby provide guidance on best timing of baseline arterial blood gas analysis in this population.
METHODS: Medically stable subjects with chronic respiratory disease were administered O2 at a constant concentration. Continuous pulse oximetry was recorded from before cessation of O2 to beyond the point of oxygen saturation (SpO2 ) equilibration. Data were fitted to an exponential decay model. Blood oxygen equilibration time was defined as the t90, the time taken for SpO2 to fall 90% of the difference between initial (on O2 ) and final (on air) values.
RESULTS: Eighty-two (82) subjects with a mean age of 66 years were included. The largest diagnostic category was chronic obstructive pulmonary disease (37), followed by interstitial lung disease (15) and bronchiectasis (12). The median t90 was 6 min 18 s (interquartile range: 4 min 32 s-10 min 30 s). The 95th centile t90 value was 20 min.
CONCLUSION: In the majority of patients with chronic respiratory disease, a time delay of 20 min between cessation of supplemental O2 and PaO2 measurement allows confidence that the result is a true baseline value.