Abstract
Introduction
The observation that oxygen desaturations do not necessarily return during CPAP withdrawal has been used to suggest that CPAP may not need to be an every night treatment. We explored the possibility that heart rate rises may return before oxygen desaturations; suggesting that sleep fragmentation may still be a problem.
Methods
We analysed pulse oximetry data from 92 patients with OSA undergoing CPAP withdrawal (3 nights on CPAP followed by 4 nights off CPAP). The nightly oxygen desaturation index =4% (ODI) and heart rate rises >6bpm index (HRR), were assessed during CPAP withdrawal using ANOVA and Fisher’s post hoc tests; in all patients, and in a subset of 27 patients with gradual ODI return.
Results
In the whole group the ODI and HRR increased equivalently and maximally on the first night off CPAP (Off CPAP 1; ODI=87% and HRR=104% of Off CPAP 4). In a subset with gradual ODI return, HRR returned rapidly (Off CPAP 1; ODI=43% and HRR=77% of Off CPAP 4; see table).
Mean±SD
(%Increase from On CPAP) |
On CPAP average |
Off CPAP 1 |
Off CPAP 2 |
Off CPAP 3 |
Off CPAP 4 |
| ODI |
5.7±3.5*
(0%) |
11.4±3.9*
(43%) |
17.6±11.1
(90%) |
17.0±10.5
(86%) |
18.9±13.1
(100%) |
| HRR |
19.0±13.1*
(0%) |
27.5±16.4
(77%) |
28.1±17.0
(82%) |
25.9±15.4**
(62%) |
30.1±16.7
(100%) |
Nightly pulse oximetry from 27 patients with gradual ODI return. Both ANOVA tests were significant (p<0.001). Post hoc tests; *=different to all other values, **=different from night 4 off CPAP (p<0.05).
Discussion
During CPAP withdrawal, in some patients, heart rate rises return before oxygen desaturations. This suggests that ODI alone may fail to adequately identify patients in whom potentially symptomatic OSA returns off CPAP.