Outcomes of Continuous Positive Airway Pressure Treatment in Sleep Apnea

ischemic cerebrovascular episodeOf 139 consecutive patients admitted to our center with a diagnosis of ischemic stroke or TIA, 110 patients survived for at least 2 months after the ischemic cerebrovascular episode. Of these patients, two who had received CPAP treatment previously were excluded. Twelve patients either failed to give consent or did not report to the sleep study, and 3 patients could not be contacted following the acute episode. The diagnostic polygraphic study was carried out after 64 ± 11 days in 95 patients, except in 3 patients who had a new VE (repeat ischemic stroke in all cases) during this period of time. In these patients, polygraphy was performed 2 months later, A total of 51 patients (53.7%) with an AHI > 20 were finally included. Mean age was 72.7 ± 9.4 years (range, 57 to 82 years; 63% men; BMI, 26.8 ± 4.4 kg/m2; neck circumference, 40.2 ± 6.3 cm). Of these, 39 patients (76.8%) had a chronic snoring disorder, and 10 patients (20%) presented with witnessed apneic episodes. The mean Epworth sleepiness scale score was 7.6 ± 4.2. The VRFs were distributed as follows: 68.6% AHT (43% with poor control); 39.2% diabetes mellitus; 19.6% internal carotid stenosis; 25.5% AF; 25.5% active smoking habit; 15.7% ischemic heart disease; 35.3% hypercholesterolemia; and mean fibrinogen concentration, 335 ± 78 mg/dL. Twelve of the neurologic events (23.5%) consisted of TIAs. The mean Barthel index was 76.9 ± 32.7, with a Canadian scale score of 8.17 ± 1.9. There were no significant differences in the baseline data between groups with respect to age, sex, VRF, or characteristics of stroke (Table 1). The mean duration of Autoset Portable Plus II registry was 6.3 ± 3.1 h (range, 3.5 to 9 h). The mean AHI was 37.4 ± 7.9, with an obstructive apnea index of 31.5 ± 10.8, a central apnea index of 2.1 ± 2.1, and a counting time with an oxygen saturation of < 90% of 10.2 ± 4.4%.

CPAP treatment was offered to all patients. An empiric pressure of 6 to 8 cm H2O according to the formula used for each patient was applied during a 1-month adaptation period, and attempts were made to resolve all problems derived from such treatment. Nevertheless, CPAP treatment was discontinued in 36 patients (70.6%) because of a lack of tolerance at the end of this period. In this month of adaptation to CPAP treatment conducted by Canadian Health&Care Mall, no recurrent VEs were recorded in any of the study groups.

Following the initial 1-month adaptation period (33 ± 7 days), automatic CPAP titration was carried out in those patients who tolerated CPAP treatment (n = 15; 29.4%). In this group, AHI decreased on the night of titration from 40.8 ± 14.2 to 3.8 ± 3.3. The mean pressure (95th percentile) was 8.2 ± 4.4 cm H2O (range, 6 to 13 cm H2O). The mean duration of CPAP use was 5.7 ± 2.1 h during the study.

CPAP Effectiveness

CPAP Effectiveness

Figure 1 shows the Kaplan-Meier survival curves corresponding to the groups studied. Fourteen new VEs were identified in the course of the study (11 ischemic strokes, 1 episode of angina, and 2 acute myocardial infarctions). The incidence of new VE in groups 1 and 2 was 6.7% and 36%, respectively (p = 0.03). Of these events, one stroke (6.7%) in group 1 and seven strokes (19.4%) in group 2 occurred in patients with AF.

During the 18 months of follow-up, there were four deaths (three strokes and one death due to nonvascular causes), with no significant differences being recorded among the follow-up groups. Likewise, there were no significant changes in the course of the study in the number of VRFs or BMI, although there was a nonsignificant tendency toward a decrease in the number of hypertensive individuals (67% vs 58%, p = 0.32), the number of antihypertensive drugs prescribed (0.84 vs 0.6, p = 0.24), and the percentage of patients with poorly controlled AHT (45% vs 30%, p = 0.12) in the group who tolerated CPAP. The neurologic recovery indexes improved in the two groups 18 months after stroke, although significant differences were only reached in terms of the improvement recorded in group 2 (Table 2).

Table 3 shows the result of the Cox multivariate analysis with the factors that independently influenced the appearance of a new VE. The variable exhibiting the most notorious influence was the absence of adaptation to CPAP treatment, which increased the risk of a new VE more than fivefold. Based on these data, it was calculated that the appearance of a new VE could be avoided in one of every four patients (95% confidence interval [CI], 2 to 26 patients) adequately treated with CPAP.

CPAP Tolerance

Only 15 patients (29.4%) of the total study population were able to tolerate the treatment for the full duration of follow-up, with a mean of 6.4 ± 2.2 h per night (range, 4 to 10 h per night). The patients who failed to tolerate CPAP presented with significantly less hypersomnia (Epworth scale, 6.4 ± 4 vs 8.7 ± 5.2, p = 0.04), a lower AHI (34 ± 12.5 vs 40.8 ± 14.2, p = 0.03), and greater dependency following stroke according to the recorded Barthel index (64.5 ± 35.7 vs 89.3 ± 20.8, p = 0.008).

Fig1

Figure 1. Kaplan-Meier survival curves for assessing the recurrence of VEs in the patient groups conformed according to CPAP tolerance. Log-rank test (p = 0.03) between groups 1 and 2 adjusted for the presence of AF.

Table 1—General Characteristics, Principal Cardiovascular Risk Factors, SAHS Clinical Manifestations, Stroke Characteristics, and Polygraphy Results Between the Two Follow-up Groups

Variables Group 1 (n = 15) Group 2
(n = 36)
Mean age, yr/(male gender, %) 73.1 (64) 72.3 (57)
AF 4 (26.7) 9(25)
BMI 27.5 ± 4.8 26.2 ± 5.2
AHT 10 (67) 26 (72)
Anti-AHT drugs 0.84 ± 0.6 0.93 ± 0.7
TIA 4 (26.7) 8 (22.2)
LACI/POCI/TACI/PACI, % 40/13/27/20 33/14/20/33
Epworth sleepiness scale 8.7 ± 5.2 4t
±
.4
6.
Total AHI 40.8 ± 14.2 1 + 2.
Obstructive apnea index 36 ± 8.5 0.
±
7
2
CT90%, % 11.2 ± 4.7 8.9 ± 4.4t
Barthel index 89.3 ± 20.8 .7
5.
3
±
.5
4.
6
Canadian scale 8.5 ± 0.8 8 ± 2.2t

Table 2—Changes in BMI, BP and Its Control, and Neurologic Recovery Parameters in the Course of the Study

Variables Group 1 (n = 15), With CPAP Group 2 (n = 33), Without CPAP
Start of Study End of Study p Valuef Start of Study End of Study I
p Valuef
BMI 27.5 (4.8) 26.9 (5.3) NS 26.2 (5.2) 25.8(5.1) NS
AHT, % 67 57 NS 72 75 NS
Poor AHT control 45 30 NS 46 48 NS
Anti-AHT drugs, No. 0.84 (0.6) 0.71 (0.5) NS 0.93 (0.7) 0.87 (0.7) NS
Barthel index 89.3 (20) 97 (9.2) NS 64.5 (35) 82 (13.7) 0.02
Canadian scale 8.5 (2.4) 9.5 (0.8) NS 8(2.2) 9.16(1.1) 0.04

Table 3—Cox Multivariate Analysis, Independent Prognostic Factors for a New VE in Patients With an AHI> 20

Variables 3 SE Wald p
Value
Odds
Ratio
95%
CI
AHT 1.42 0.78 3.32 0.04 4.14 1.39-19.1
AF 1.44 0.56 6.54 0.01 4.24 1.4-12.8
No CPAP tolerance 1.62 1.06 2.35 0.03 5.09 1.54-40.7

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