Retrograde Air Escape via the Nasolacrimal System

Abstract

CRANS represents a previously undescribed clinical entity. CRANS may be responsible for some CPAP-related eye side effects and possibly for rarer secondary eye complications, including conjunctivitis and corneal ulceration. CRANS should be suspected in any patient on CPAP complaining of eye symptoms. CRANS may be diagnosed through careful observation during A-PSG and confirmed by performing a "saline bubble test." Management options include nonsurgical (mask alternatives, humidification, nasopharyngeal airway) and surgical techniques (nasal airway surgery, inferior turbinate out-fracture and adhesion, injection of bulking agent around Hasner's valve).

Face Mask-Associated Ocular Irritation and Dryness

“…Irritation and contact lens dryness were found in patients using chemical protection hoods that blow air across the inside of the face mask [4]. Continuous positive airway pressure (CPAP) masks may cause ocular surface irritation due to air leakage or regurgitation through the nasolacrimal system [5,6]. All of these studies suggest that increased air convection affects the eye; however, this process is not described in the context of face mask use.…”

Late-onset bleb-associated endophthalmitis and continuous positive airway pressure

“…Interestingly, even in the absence of detectable mask leaks, CPAP-associated retrograde air flow via the nasolacrimal system (CRANS) may be evident by a saline bubble test during CPAP use 34 , a mechanism previously suggested to have implications in dry eye and conjunctivitis. 31 , 35 …”

Continuous Positive Airway Pressure Thresholds for Nasolacrimal Air Regurgitation in a Cadaveric Model

“…In this study, all 6 unoperated nasolacrimal systems showed no AR at the highest testable level (30 cm H2O), consistent with the rare occurrence of AR in CPAP patients with unoperated nasolacrimal systems. 5, 6…”

“…While air regurgitation through an unoperated nasolacrimal system in patients using CPAP occurs only rarely, it may occur after DCR in about 70% of cases. 5–8 Regurgitation is associated with greater patency and higher success rate of DCR surgery. 4, 9, 10 Associated symptoms, including difficulty sleeping, dry eyes, eye pain, and blurry vision, significantly disrupt CPAP compliance in up to 43-50% of patients.…”

“…11 Nasolacrimal AR with CPAP has been reported only rarely in patients without a history of DCR. 5, 6 In these reports, pressures were given for 3 patients: two patients received CPAP at pressures of 17 and 15 cm H 2 O, respectively, and one patient used bi-level positive airway pressure (BiPAP) at pressures of 18/10 cm H 2 O. The present study aims to expand the current understanding of nasolacrimal AR with CPAP therapy by seeking to identify the threshold pressures for producing this phenomenon in a cadaver model before and after either nasolacrimal duct (NLD) probing or endoscopic DCR.…”