Abstract: | Objective – To establish a reference interval for tissue oxygen saturation (StO2) levels measured by a portable near‐infrared spectroscope and determine site(s) for reproducibly measuring StO2 levels in dogs. Design – Prospective experimental study. Setting – Veterinary teaching hospital. Animals – Seventy‐eight healthy dogs. Measurements and Main Results – A portable device that quantitatively measures StO2 levels directly in muscle tissue using near‐infrared spectroscopy (NIRS) was topically applied to shaved sites over 4 muscle bodies. Readings from the sartorius muscle were obtained 100% of the time. The digital extensors and biceps femoris muscles provided similar readings, but less consistently obtained StO2 values (70% and 67%, respectively). Mean StO2 levels measured over these 3 sites were not statistically different from one another. When readings from these 3 sites were combined, a mean ±1 SD of 92.9±7.4% was obtained. The epaxial muscles produced a significantly lower mean ±1 SD (68.5±22.4%), and readings were obtained only 60% of the time. Conclusions – In dogs, a mean ±1 SD of 92.9±7.4% can be used to investigate clinical applications of NIRS. The sartorius muscle most consistently allows for detection of StO2 levels (100%). The epaxial muscles are not consistent or reliable for obtaining StO2 readings and are not recommended for clinical application of near‐infrared spectroscope. Sex does not significantly affect StO2 readings at any site. Body condition score only affects readings obtained from the sartorius muscle. |