Dark Skin Decreases the Accuracy of Pulse Oximeters at Low Oxygen Saturation: The Effects of Oximeter Probe Type and Gender

Pulse oximetry in family practice: indications and clinical observations in patients with COPD

PURPOSE

To establish situations in which family physicians (FPs) consider pulse oximetry a valuable addition to their clinical patient assessment; to explore pulse oximetry results (SpO(2)) when used by FPs in patients with chronic obstructive pulmonary disease (COPD); to explore associations between SpO(2) and other markers of COPD severity.

METHODS

We performed three separate studies: (i) interviews plus a Delphi consensus procedure with FPs experienced in using pulse oximetry to elucidate indications for pulse oximetry; (ii) analysis of SpO(2) and clinical data in COPD patients who presented to FPs with deteriorating symptoms and (iii) analysis of SpO(2), spirometry and clinical data in patients with stable COPD.

RESULTS

Interviewed FPs (n = 11) used their pulse oximeter for a range of acute (14) and non-acute (11) indications but valued it highest in acute (worsening of) dyspnoea, in suspected respiratory insufficiency/failure and in patients with COPD. In 88 patients with deteriorating COPD, 22% showed SpO(2) <or=92%. Correlation between baseline forced expiratory volume in 1 second % predicted and SpO(2) in patients presenting with acute COPD exacerbations was r = 0.55 (P = 0.001). In 207 patients with stable COPD, 6.3% showed SpO(2) values <or=92%. SpO(2) values were associated with Medical Research Council dyspnoea scores (P = 0.019).

CONCLUSIONS

FPs report a wide range of indications for pulse oximetry in acute as well as non-acute situations. In COPD, pulse oximetry appears to be especially useful in patients with severe disease and worsening of symptoms. Pulse oximetry may have a role in the monitoring of patients with COPD with exercise-related dyspnoea.

Carbon dioxide monitoring during long-term noninvasive respiratory support in children

INTRODUCTION

Routine monitoring of noninvasive respiratory support relies on nocturnal pulse oximetry and daytime arterial blood gases, without systematic nocturnal carbon dioxide recording. The aim of the study was to assess if overnight pulse oximetry and daytime blood gases are sufficiently accurate to detect nocturnal hypoventilation in children receiving long-term noninvasive respiratory support.

MATERIALS AND METHODS

Pulse oximetry and carbon dioxide pressure measured by capillary arterialized blood gases and a combined transcutaneous carbon dioxide and pulse oximetry (PtcCO(2)/SpO(2)) monitor were compared in 65 patients (asthma, n = 16, recurrent bronchitis, n = 8, lung infection, n = 8, cystic fibrosis, n = 15, interstitial lung disease, n = 6, neuromuscular disease, n = 12). Daytime capillary arterialized blood gases and nocturnal recording of pulse oximetry and carbon dioxide by means of a combined PtcCO(2)/SpO(2) monitor were performed in 50 other patients receiving nocturnal noninvasive respiratory support at home.

RESULTS

A correlation was observed between pulse oximetry (r = 0.832, P < 0.0001) and carbon dioxide pressure (r = 0.644, P < 0.0001) measured by capillary arterialized blood gases and the combined PtcCO(2)/SpO(2) monitor. Twenty-one of the 50 patients (42%) on long-term noninvasive respiratory support presented nocturnal hypercapnia, defined by a PtcCO(2) value >50 mmHg, without nocturnal hypoxemia. Daytime capillary arterialized carbon dioxide levels were normal in 18 of these 21 patients.

CONCLUSIONS

Nocturnal hypercapnia may occur in children receiving nocturnal noninvasive respiratory support at home. Nocturnal pulse oximetry and daytime arterial blood gases are not sufficiently accurate to diagnose nocturnal hypercapnia, underlying the importance of a systematic carbon dioxide monitoring in children receiving noninvasive respiratory support.