Prevention of Morbidity in Sickle Cell Disease (POMS 2): A Pilot Study of Nocturnal Respiratory Support Shows That Auto-Adjusting Positive Airways Pressure Is Safe and Is Preferred to Oxygen Therapy

Despite the high prevalence of obstructive sleep apnea (OSA) and overnight hypoxia in sickle cell disease (SCD) patients, there are few data on treatment safety and efficacy, with controversy about the optimal management of these complications. Auto-adjusting positive airways pressure (APAP) has been shown to improve attention span and reduce pain episodes in children with sickle cell anemia (SCA) in a pilot randomized trial and there is observational evidence that nocturnal oxygen therapy (NOT) used for a period of at least six months in patients with SCD and severe nocturnal hypoxia is safe and easy to use.

 The Prevention of Morbidity in Sickle Cell Disease (POMS 2a) study is a National Institute for Health Research (NIHR) funded pilot feasibility trial to compare APAP with NOT in adults and children with SCD to establish the most acceptable treatment strategy and to determine short term safety of both interventions. We also assessed the feasibility of using an iPad app to collect daily pain scores.

 Methods: This was a cross-over interventional trial.  Inclusion criteria were: age  over 8 years, diagnosis of HbSS and ability to give informed consent and use an iPad. Evidence of overnight hypoxia and/or OSA was not necessary for inclusion in the trial. Each intervention was administered for a week in randomized order with a week of baseline data collection and a week of washout between the interventions. Tablet technology was used to collect daily pain scores and a detailed qualitative interview was performed after both interventions.  These transcripts were analysed manually by two researchers using content analysis. Physiological and safety data included blood tests (routine hematology and biochemistry testing), urine protein measurements, oximetry,  quality of life (using PedsQL), spirometry and lung volume measurements, which were measured at baseline and after each intervention. Adherence data was downloaded from the APAP machine and was self-reported for NOT.

 Results: Ten adults (3 female, mean age 31.7 years, 4 on hydroxyurea) and eleven children (5 female, mean age 11.9 years, 7 on hydroxyurea) were enrolled. APAP adherence data was available on 8 adults who completed 3 to 7 nights of APAP for a mean of 6.13 hours (range 4.49-7.76). Data was not available on 2 patients. One patient completed 3 days of APAP and was admitted two days later with a painful crisis and subsequent acute chest syndrome, they were subsequently withdrawn from the trial. One adult developed a pain crisis on day 2 of NOT which was self managed at home. Data on APAP adherence was available on nine children who  completed APAP therapy for 3-7 nights for a mean of 5.9 hours(range 1.94-9.05), there was no data on 1 child and one did not tolerate APAP and stopped after one night. This child was admitted with a pain crisis  three days after stopping APAP. Detailed quantitative interviews were completed on 19 participants . The majority of participants showed a preference for APAP because the machine was smaller, easier to handle and less noisy and  noted that they slept better when using the APAP machine and were less fatigued, but some participants found the mask uncomfortable.  Patients reported that NOT had a calming effect on them but they also reported that it was very noisy and caused dry nose, throat and mouth. There was no significance difference in hemoglobin, reticulocyte count, creatinine, erythropoietin, albumin creatinine ratio, bilirubin or lactate dehydrogenase at baseline and after either intervention. One patient showed a decrease in absolute reticulocyte count from 128x10⁹l to 53x 10⁹/l after NOT therapy, with no change in hemoglobin. Mean overall pain days per week were 2.31 at baseline, 1.57 during APAP, 1.47 during NOT and 2.08 during washout. There was no difference in spirometry and lung volume measurements between baseline and post intervention. Pulse oximetry  and Quality of Life  was unchanged between baseline and after both interventions

 Conclusion: There were no safety concerns, in particular there was no evidence of erythroid suppression or rebound pain after 7-day application of APAP or nocturnal oxygen therapy. Tablet technology was acceptable to patients with satisfactory levels of completion. In view of patient preference for APAP the steering group has decided to proceed with a phase 2b randomized trial of six months therapy with APAP versus standard care to assess its effects on pain, quality of life and cognitive function.