University of Melbourne Equine Centre, Melbourne, Victoria, Australia.
University of Adelaide Equine Health and Performance Centre, Roseworthy, South Australia, Australia.
Equine Vet J. 2020 May;52(3):352-358. doi: 10.1111/evj.13177. Epub 2019 Oct 8.
There is limited knowledge of the breathing strategy and impact on the patency of the upper respiratory tract (URT) in swimming horses.
To describe the respiratory responses and endoscopic appearance of the URT during tethered swimming in horses.
Prospective descriptive study.
Ten race-fit horses, with no history of URT obstruction, were examined during tethered swimming. Endoscopic examination, heart rate, sound recordings and above and below water video recordings were obtained. Plasma lactate concentration was measured before and 5 min after swimming and tracheal endoscopy was performed 30 min after exercise to assess for presence of blood or mucus. Four horses also underwent endoscopy during exercise on the track.
Mean (±s.d.) breathing frequency was 28 ± 5 breaths/min during swimming, with a brief inspiration (mean ± s.d. T = 0.51 ± 0.08 s), followed by a period of apnoea (1.59 ± 0.53 s) and then a short, forced expiration (T = 0.42 ± 0.5 s). During apnoea all horses exhibited complete collapse of the URT including closure of the external nares, nasopharynx and rima glottidis (with bilateral adduction of the arytenoid cartilages and vocal folds) and, in two horses, epiglottic retroversion. No horses had URT collapse during overground exercise. Locomotor-respiratory coupling was not observed during swimming. Median (IQR) plasma lactate post swim was 4.71 mmol/L (2.08-8.09 mmol/L) vs 0.68 mmol/L (0.65-0.71 mmol/L) preswim. Post swim endoscopy revealed grade 1 exercise-induced pulmonary haemorrhage (EIPH) in 2 horses. Median mucus grade was 1 (range 0-3).
Overground endoscopy was not performed in all horses.
Horses experienced complete URT collapse associated with post inspiratory apnoea when swimming. The reason for this is unknown but may be to aid buoyancy or associated with the mammalian dive response - a survival reflex to preserve oxygen stores and prevent water entering the lungs.
对于游泳马匹的呼吸策略及其对上呼吸道通畅性的影响知之甚少。
描述 tethered 游泳时马匹的呼吸反应和上呼吸道内镜表现。
前瞻性描述性研究。
10 匹赛马，无 URT 阻塞史，在 tethered 游泳时进行检查。进行内镜检查、心率、声音记录以及水上和水下视频记录。游泳前和游泳后 5 分钟测量血浆乳酸浓度，运动后 30 分钟进行气管内镜检查以评估是否有血液或黏液。4 匹马还在赛道上运动时进行了内镜检查。
游泳时平均（±标准差）呼吸频率为 28±5 次/分钟，短暂吸气（平均 T=0.51±0.08 s），随后呼吸暂停（1.59±0.53 s），然后是短暂的强制呼气（T=0.42±0.5 s）。呼吸暂停期间，所有马匹的 URT 完全塌陷，包括外鼻孔、鼻咽和声门裂（杓状软骨和声带双侧内收），在 2 匹马中还出现会厌反转。没有马匹在陆地上运动时出现 URT 塌陷。游泳时没有观察到运动-呼吸耦联。游泳后中位数（IQR）血浆乳酸为 4.71 mmol/L（2.08-8.09 mmol/L），游泳前为 0.68 mmol/L（0.65-0.71 mmol/L）。游泳后内镜检查显示 2 匹马有 1 级运动性肺出血（EIPH）。中位数黏液等级为 1（范围 0-3）。
并非所有马匹均进行了陆上内镜检查。
游泳时马匹的 URT 完全塌陷与吸气后呼吸暂停有关。其原因尚不清楚，但可能有助于浮性或与哺乳动物潜水反应有关，这是一种生存反射，可保存氧气储备并防止水进入肺部。
