Normal Respiratory Rate and Peripheral Blood Oxygen Saturation in the Elderly Population

Abstract

To the Editor: Age-specific normal limits for a number of vital signs and physiological parameters have not been established in the elderly population. The limits for younger adults are not always applicable because of ageassociated physiological changes and the increase of interindividual differences with age. 1 Regarding the respiratory system, there are few data on normal respiratory rate at rest (RR) and peripheral pulse oximetry values (SpO 2 ), which are major parameters in clinical practice and easy to measure, and become altered quickly in respiratory and cardiac diseases. (Increased respiratory rate is often the only visible sign of a respiratory infection.) 2,3 This was a cross-sectional study of 791 noninstitutionalized individuals aged 65 and older living in Spain to establish the limits of normal RR and SpO 2 in the elderly population.The sample was collected using multistaged probabilistic sampling and stratified according to sex, size of place of residence (rural, urban, or big city), and geographic location with a nonproportional age stratum (523 subjects aged ≥80). A sample of 576 participants was considered necessary to estimate RR and SpO 2 with 5% error and a design effect of 1.5.Survey data were collected between 2007 and 2009. The survey was carefully designed to reduce nonsampling errors, the survey takers received specific training, and the field work was thoroughly supervised.RR and the SpO 2 were measured with the participant in a seated position after a rest of at least 10 minutes. SpO 2 was measured using a pulse oximeter (9500; Nonin Medical, Plymouth, MN), and RR was measured by directly observing thoracic movements for a 30-second period. As a distraction maneuver, the survey takers pretended to measure the radial pulse, so that participants would not be aware that their respiratory rate was being measured. 3 All information about participants' medical background was collected as control variables.Two consecutive analyses were conducted. First, all participants with pathologies that proved to affect RR or SpO 2 independently in multivariable models were excluded. A subsequent more-restricted analysis was performed by excluding all individuals who had any clinical factor showing significant influence in bivariate analyses. Participants with dyspnea during the examination were excluded from all calculations.Normal RR limits were represented according to percentiles that delimit 95% of the sample (2.5-97.5) and percentiles that delimit 99% of the sample (0.5-99.5). Limits of SpO 2 were represented according to the first and fifth percentiles. Calculations were weighted according to age, sex, and size of place of residence.History of chronic obstructive pulmonary disease (COPD) was the only variable that independently influenced RR and SpO 2 in the multivariate models. Once individuals with COPD were excluded, the RR distribution appeared bell-shaped, with 0.67 kurtosis and 0.43 asymmetry, and was significantly different from the theoretical normal distribution according to the Kolmogor...

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