The Effect of Topical Oxygen Therapy in Horses Affected with Mycosis of the Guttural Pouch: An Experimental Pilot Study and a Case Series

Abstract

Background: The management of bleeding originating from the guttural pouch (GP) has a high success rate, but the resolution of the macroscopic inflammatory lesions in the case of mycosis (GPM) is highly variable; the resolution of neurological disorders is inconstant and challenging. Objectives: Our aim was to test the feasibility and safety of topical oxygen therapy (TOT) in horses after induction of GPM and in cases with naturally occurring disease. Study design: This study was an in vivo experimental and retrospective two-phase study. Methods: During phase 1, the pilot study, both GPs were inoculated with Aspergillus fumigatus. One GP was randomly assigned to receive one to four TOT 30 min sessions with 100% medical oxygen at 9 L/min. Follow-up endoscopic images were assessed for scoring macroscopic inflammatory lesions of the pharynx and both GPs. In phase 2, the clinical study, TOT was administered for 45 to 60 min at 15 L/min in six horses presenting with GPM. Results: In phase 1, TOT administration was easy to perform in the standing horse with no adverse effects. After more than two administrations, macroscopic inflammatory lesions decreased more quickly in size in the treated GP. In phase 2, horses were treated with TOT only (n = 1) or combined with a transarterial coil embolization (TACE) procedure (n = 5). After TOT and discharge from the hospital, nasal discharge resolved in three horses, and improvement was noted in the fourth one. Between days 2 and 10 after admission, upper respiratory tract endoscopy (URTE) indicated size reduction and alteration in the appearance of all the macroscopic inflammatory lesions. The partial or total recovery of neurological disorders (2/4 laryngeal hemiparesis, 3/5 dysphagia, 1/2 dorsal displacement of the soft palate (DDSP), and 1/1 Horner’s syndrome) was recorded. Main limitations: In phase 1, the small number of horses did not allow for statistically significant conclusions; in phase 2, clinical signs at admission varied between horses, which made comparison difficult. Conclusions: In adult horses, TOT alone or in combination with TACE is feasible and safe with a propensity to reverse the course and the progression of inflammatory lesions without additional local or systemic treatment.

Diagnosis of Aspergillosis in Horses

“…To the best of our knowledge, no comprehensive data on the prevalence of GPM has been published. During the last decade, GPM occurrences are mainly reported by the results of cluster case series [ 5 , 6 , 7 , 8 ]. The rare equine invasive pulmonary aspergillosis (IPA) has almost 100% mortality [ 9 , 10 ].…”

Treatment of guttural pouch mycosis with salpingopharyngostomy

“…An additional therapeutic that might have been helpful in this case prior to salpingopharyngeal fistulation is topical oxygen therapy (TOT) which has been recently published by Lepage et al (2021) for use as an adjunct treatment in epistaxis cases following transarterial coil embolization (TACE) or as a primary treatment in nonbleeding cases. Part of the rationale behind pursuing additional treatment options by this group is the percentage of horses that fail to completely resolve the neurological sequelae of the disease which has been reported at 50% (Lepage & Piccot-Crézollet, 2010).…”

“…Guttural pouch mycosis does not lend itself to aggressive surgical debridement given the closely associated vessels and nerves to the mycotic plaques, however, the somewhat enclosed environment of the guttural pouch may be an advantage for TOT. Lepage et al (2021) treated cases with TOT four times per day at 15 L/min for 1-2 weeks by placing an indwelling catheter into the affected guttural pouch and leaving it in place as much as possible for the duration of hospitalisation. During treatments, the horses were restrained with their heads at the height of the withers to decrease the opening of the guttural pouch orifice to maintain a closed high oxygen environment, though swallowing would still result in transient openings of the orifices.…”

Treatment of guttural pouch mycosis with salpingopharyngostomy

“…11 An additional therapeutic that might have been helpful in this case prior to salpingopharyngeal fistulation is topical oxygen therapy (TOT) which has been recently published by Lepage et al for use as an adjunct treatment in epistaxis cases following transarterial coil embolization (TACE) or as a primary treatment in non-bleeding cases. 12 Part of the rationale behind pursuing additional treatment options by this group is the percentage of horses that fail to completely resolve the neurologic sequelae of the disease which has been reported at 50%. 13 When examining the issue of recurrent epistaxis following TACE the survival rate is 84% which places this high level of persistent neurological abnormalities into sharp relief.…”

“…During treatments the horses were restrained with their heads at the height of the withers to decrease the opening of the guttural pouch orifice to maintain a closed high oxygen environment, though swallowing would still result in transient openings of the orifices. 12 Following a minimum of two treatments the fungal plaques were seen to begin regressing. Additionally the reported resolution or significant improvement of 10/12 neurologic disorders is encouraging compared to the 9/18 cases of resolution reported in a larger retrospective study on TACE.…”