By Lucy Piper, Senior MedWire Reporter
Overnight pulse oximetry can be used to accurately diagnose sleep-disordered breathing (SDB) in patients with chronic heart failure, UK research suggests.
"Depending on the diagnostic cutoff chosen, pulse oximetry may be of greatest clinical value as a 'rule out' test," Neil Ward (Royal Brompton Hospital, London) and colleagues explain.
By contrast, however, they found that heart rate variability is not suitable for identifying patients with chronic heart failure who have SDB.
Among 171 (99%) of 180 patients with chronic heart failure in whom overnight pulse oximetry could be analyzed, 76 (44%) had SDB, defined as having an apnea-hypopnea index of at least 15 events/hour.
The 3% oxygen desaturation index had an area under the receiver-operating curve of 0.92 for detecting SDB, which the researchers say indicates high diagnostic accuracy.
At a pre-determined cutoff of more than 7.5 desaturations/hour, the 3% oxygen desaturation index predicted SDB with a sensitivity of 97% and a specificity of 32%. The negative and positive likelihood ratios were 0.08 and 1.42, respectively.
However, raising the cutoff to 12.5 desaturations/hour improved diagnostic accuracy by reducing the number of false-negatives, thereby increasing the specificity to 73%, while sensitivity remained high, at 93%.
The researchers report in Thorax that the 3% oxygen desaturation index had a superior diagnostic accuracy to the percent very low frequency increment (%VLFI) component of heart rate variability.
Notably, it was only measurable in 77 (45%) patients, among whom 36 (46%) had SDB. The area under the receiver-operating curve for detecting SDB was therefore just 0.50.
At the pre-determined cutoff of at least 2.23%, the %VLFI had a sensitivity for diagnosing SDB of 58% and a specificity of 48%, with negative and positive likelihood ratios of 0.88 and 1.11, respectively.
Given the poor diagnostic accuracy of HRV, Ward et al say "it cannot be recommended to screen for SDB in patients with CHF."
They conclude: "Overnight pulse oximetry would be of greatest clinical use to rule out SDB in patients with CHF [chronic heart failure], helping to reduce pressure on sleep laboratory facilities and prioritise patients who may require more detailed sleep studies."
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