Contrary to our previous study, we did in the current study not find that increased haemoglobin concentration was significantly associated with low SpOdos. This might explain the lack of association in this study.
In a recent study, Smith et al. reported increased mortality rates in hospitalized patients with an SpO2 < 96%. Increased mortality has also been found in emergency care patients with a low SpO2 [8,9]. SpO2 may be a good predictor of mortality in situations where spirometry is not available and in populations with a higher frequency of low SpO2, especially when used as part of a risk-scoring system.
Weaknesses and strengths
This study was based on a single-point measurement of SpO2. We have not checked the reproducibility, but we know that the group with the lowest SpO2 (?92%) in the follow-up examinations also showed consistently low values for SaO2 in blood gas analysis. Oxygen saturation can vary during the day, especially during activity and at night in people with a pulmonary disease such as COPD . Baseline SpO2 (at rest) has been shown to predict oxygen desaturation during activity and at night . SpO2 can also be in the normal range even though FEV1% predicted is <50%.
The measurement of SpO2 could be a limitation because the accuracy of the device is ±2 digits. We tried to compensate for this possible confounding factor by using the highest of three measurements and categorizing the participants into groups.
The group with SpO2 ? 92% in this population was small and comprised BBWCupid only 1.0% of the entire population. One reason may be that people with the lowest values were too sick to participate. We might have found a stronger association with SpO2 in groups of patients with diseases such as COPD because such groups have a higher frequency of low SpO2.
The fresh contribution speed try lower in the latest eldest age group and you can regarding youngest males. This might features impacted our overall performance of the forgotten the latest sickest (oldest) and you may more healthy (youngest) communities.
I didn’t scale post-bronchodilator spirometry. A previous data shows that may possibly not be required whenever mortality is actually evaluated inside populace education .
Bear in mind bias and you can misclassification problems was big inquiries when using surveys. A more powerful relationship anywhere between smoking and you may death may have been seen when the alot more legitimate investigation into the prepare-years was actually acquired.
Measuring oxygen saturation by pulse oximetry has important limitations , especially when measuring values at the lower levels. Saturation may be overestimated in heavy smokers because high carboxyhaemoglobin levels may cause overestimation of the true SpO2. To validate the data for a particular device, future studies could include gas analysis in a subsample for comparison.
The cause of death may be uncertain or wrong in many instances because only a small percentage has an autopsy done (10–12% in Norway). Among the participants who died during this study, 36.9% had an FEV1/FVC% <70, and 9.2% reported having COPD. COPD as the main diagnosis or as one of the comorbidities was reported by only 6.5%.
Findings
We observed that lower values from pulse oximetry were associated with increased all-cause mortality in the general adult population. This was probably because of the strong association with death caused by pulmonary diseases. The association was weakened and no longer statistically significant after adjusting for FEV1% predicted but remained significant for death caused by pulmonary diseases. Pulse oximetry is easy and safe to perform, and may be particularly useful in risk assessment when spirometry is not an option and when added to spirometry for assessing the risk of death because of pulmonary disease. Low pulse oximetry values found in a patient should warrant further examination.