Methods
This retrospective chart review examined patients prescribed ASV therapy at the Hampton Veterans Affairs Medical Center (HVAMC) in Virginia who had therapy data between January 1, 2015, and April 30, 2020. The start date was chosen to approximate the phase-in of wireless PAP devices at HVAMC and to correspond with the release of preliminary results from the SERVE-HF trial.
Patients were initially identified through a query into commercial wireless PAP management databases and cross-referenced with HVAMC patients. Adherence and efficacy data were obtained from the most recent clinical PAP data, which allowed for the evaluation of patients who discontinued therapy for reasons other than intolerance. Clinical, demographic, and polysomnography (PSG) data were obtained from the electronic health record. One patient, identified through the database query but not found in the electronic health record, was excluded. In cases of missing PSG data, especially AHI or similar values, all attempts were made to calculate the data with other provided values. This study was determined to be exempt by the HVAMC Institutional Review Board (protocol #20-01).
Statistics
Statistical analyses were designed to compare clinical characteristics and adherence to therapy of those with primarily CSA on PSG and those with primarily OSA. Because it was not currently known how many patients would fit into each of these categories, we also planned secondary comparisons of the clinical and PSG characteristics of those patients who were adherent with therapy and those who were not. Adherence with ASV therapy was defined as device use for ≥ 4 hours for ≥ 70% of nights.
Comparisons between the means of 2 normally distributed groups were performed with an unpaired t test. Comparisons between 2 nonnormally distributed groups and groups of dates were done with the Mann-Whitney U test. The normality of a group distribution was determined using D’Agostino-Pearson omnibus normality test. Two groups of dichotomous variables were compared with the Fisher exact test. P value < .05 was considered statistically significant.
Results
Thirty-one patients were prescribed ASV therapy and had follow-up at HVAMC since 2015. All patients were male. The mean (SD) age was 67.2 (11.4) years, mean body mass index (BMI) was 34.0 (5.9), and the mean (SD) Epworth Sleepiness Scale (ESS) score was 10.9 (5.8). Patient comorbidities included 30 (97%) with hypertension, 17 (55%) with diabetes mellitus, 16 (52%) with coronary artery disease, and 11 (35%) with congestive heart failure. Three patients had no echocardiogram or other documentation of left ventricular ejection fraction (LVEF). One of these patients had voluntarily stopped using PAP therapy, another had been erroneously started on ASV (ordered for fixed BPAP), and the third had since been retitrated to CPAP. In the 28 patients with documented LVEF, the mean (SD) LVEF was 61.8% (6.9). Ten patients (32%) had opioids documented on their medication lists and 6 (19%) had benzodiazepines.
The median date of diagnostic sleep testing was January 9, 2015, and testing was completed after the release of the initial field safety notice regarding the SERVE-HF trial preliminary findings May 13, 2015, for 14 patients (45%).12 On diagnostic sleep testing, the mean (SD) AHI was 47.3 (25.6) events/h and the median (IQR) oxygen saturation (SpO2) nadir was 82% (78-84). Three patients (10%) were initially diagnosed with CSA, 19 (61%) with OSA, and 9 (29%) with both. Sixteen patients (52%) had ASV with fixed expiratory PAP (EPAP), and 15 (48%) had variable adjusting EPAP. Mean (SD) usage of ASV was 6.5 (2.6) hours and 66.0% (34.2) of nights for ≥ 4 hours. Mean (SD) titrated EPAP (set or 90th/95th percentile autotitrated) was 10.1 (3.4) cm H2O and inspiratory PAP (IPAP) (90th/95th percentile) was 17.1 (3.3) cm H2O. The median (IQR) residual AHI on ASV was 2.7 events/h (1.1-5.1), apnea index (AI) was 0.4 (0.1-1.0), and hypopnea index (HI) was 1.4 (1.0-3.2); the residual central and obstructive events were not available in most cases.