Table 2.

General characteristics of included studies.

Study quality assessment∗
Author, year, country	Inclusion criteria	Exclusion criteria	Outcomes analyzed	1	2	3	4	5	6	7	8
Colrain et al., 2008 [12] USA	(i) 18 years & up (ii) People who snore or gasp or with apnea reported by their bed partners: selected from community following a telephone screen (iii) Clinic patients following PSG	BMI >35 Kg/m2, PAP users, URI symptoms, severe nasal allergies, sinusitis, nasal airflow restriction reported by patients, h/o nose surgery or trauma, insomnia or narcolepsy, or PLMD patients, serious medical problems including respiratory failure, heart failure, stroke, cancer, and MI. Females who are pregnant or planning to be pregnant	AHI, ODI, min SPO2, %TST SPO2 > 90, %TST snoring, questions related to comfort, ease of breathing via nose, comparison to PAP if patients previously used PAP, and sleep architectures including sleep stages on PSG	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
Rosenthal et al., 2009 [16] USA	Adults with snoring or witnessed apnea or those who are diagnosed with OSA	Prior PAP use, severe illness including cancer, CHF, COPD, and other coexistent sleep disorders, and sinusitis or severe nasal allergies or nasal blockage	AHI, ODI, PSQI, ESS, and sleep architectures including sleep stages on PSG	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
Berry et al., 2011 [18] USA	Newly diagnosed or untreated OSA patient with prestudy AHI ≥ 10 and age ≥ 18 years	H/o upper airway surgery, nasal obstruction or chronic nasal decongestant use, severe nocturnal oxygen desaturations, prior PAP or oral device use, sedative or neuromedications which affect alertness, serious or uncontrolled chronic illnesses, and other comorbid sleep disorders	AHI, ODI, SPO2 < 90%, ESS, and sleep architectures including sleep stages, effect of position on sleep stages, REM and non-REM AHI, and arousal index on PSG	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Kryger et al., 2011 [19] USA	Patients with ≥ 50% reduction in AHI or AHI of < 10 on 3-month n-EPAP on PSG or 1-week device off PSG n-EPAP use of ≥ 4 h/night and ≥ 5 nights/week on average 3-month trial of n-EPAP versus sham study	Same criteria as for original n-EPAP versus sham study. H/o upper airway surgery, nasal obstruction or chronic nasal decongestant use, severe nocturnal oxygen desaturations, prior PAP or oral device use, sedative or neuromedications which affect alertness, serious or uncontrolled chronic illnesses, and other comorbid sleep disorders	AHI, ODI, SPO2 < 90%, ESS, snoring, and sleep architectures including sleep stages, effect of position on sleep stages, REM and non-REM AHI, and arousal index on PSG	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
Patel et al., 2011 [13] USA	OSA patients with AHI with 4% desaturation > 5/hr	Patients with significant nasal obstruction, central apnea, CHF, neuromuscular disease, hypoventilation, elevated serum bicarbonate or arterial PCO2, and unexplained desaturations on baseline PSG	P crit, EtCO2 in supine and lateral positions in sleep and wakefulness during PSG, awake lung volumes in sitting, supine, and lateral positions including FEV1, FVC, FRC, ERV, TLC, and FEV1/FVC, and sleep architectures including sleep stages, effect of positions on sleep, REM and non-REM AHI, and arousal index	No	Yes	Yes	Yes	Yes	No	Yes	Yes
Walsh et al., 2011 [17] USA	18-year-olds with OSA symptoms who refused or are nonadherent to CPAP with less than 3 hours of nightly use & AHI on baseline of >15 or >10 with symptoms of daytime sleepiness, mood issues, or hypertension or cognitive impairment	Nasal blockage or allergies or sinusitis, chronic use of nasal decongestants or nasal lesions, comorbid sleep, other sleep disorders, cardiorespiratory diseases, psychiatric disorders, pregnancy, and large caffeine consumption	AHI, ODI, ESS, FOSQ, and sleep architecture variables including sleep stages, percent of oxygen saturations, and arousal indices	No	Yes	Yes	Yes	Yes	No	Yes	Yes
Rossi et al., 2013 [14] UK, Switzerland	Diagnosed and treated for OSA with CPAP for >12 months of ≥ 4 hours of nightly use prior to this trial in ages between 20 and 75 years, ODI of >10/h on baseline PSG or >10/h on nocturnal pulse oximetry test prior to enrolling for this trial. This test was performed on last night of 4-day CPAP off period	H/o CAD, PAD, uncontrolled or severe HTN, ventilator failure or Cheyne-Stokes breathing, sleep related accidents, comorbid sleep disorder, or commercial drivers	AHI, ODI, ESS, BP, and ODI from home oximetry	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Friedman et al., 2015 [15] USA	Age >18, diagnosis of OSA in previous 12 mo., failed CPAP	No stringent exclusion criteria	AHI, ODI, SPO2, snoring by VAS, ESS, and SAQLI	No	Yes	Yes	Yes	Yes	No	Yes	Yes

^∗Quality assessment of the included studies checklist from questions from National Institute for Health and Clinical Excellence (NICE): 1–8: (1) Case series collected in more than one center? (2) Is the hypothesis/aim/objective of the study clearly described? (3) Are the inclusion and exclusion criteria clearly reported? (4) Is there a clear definition of the outcomes reported? (5) Were data collected prospectively? (6) Is there an explicit statement that patients were recruited consecutively? (7) Are the main findings of the study clearly described? (8) Are outcomes stratified?

PLMD: periodic limb movement disorder; MI: myocardial infarction or angina; PAP: positive airway pressure; B/W: between; ODI: oxygen desaturation index; min SPO₂: minimum oxygen saturation; TST SPO₂: total sleep time with oxygen saturation; PSQI: Pittsburgh Sleep Quality Index; ESS: Epworth Sleepiness Scale; COPD: chronic obstructive pulmonary disease; CHF: congestive heart failure; REM: rapid eye movement sleep; non-REM: nonrapid eye movement sleep; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; FRC: functional residual capacity; ERV: expiratory reserve volume; TLC: total lung capacity; P _crit: critical closing pressure; EtCO₂: end tidal CO₂; n-EPAP: nasal EPAP (Provent); FOSQ: Functional Outcomes of Sleep Questionnaire; CAD: coronary artery disease; PAD: peripheral arterial disease; HTN: hypertension; BP: blood pressure; SAQLI: sleep apnea quality of life index; VAS: visual analog scale for snoring measurement.