EMS Canine Evaluation of Oxygen Saturation (SpO2)

Anatomy and Physiology

Adept medical personnel are familiar with the basics of canine anatomy and physiology. Fortunately, canines have a similar cardiorespiratory system compared to humans. Air passes through the canine nares and oropharynx to the trachea and bilateral lungs. After this, the oxygenated blood will move throughout the canine circulatory system and oxygenate the tissue and organs of the body. The blood oxygenation level measured by pulse oximetry is a quick indicator of the global status of the canine's health. The normal canine oxygenation ranges from 94% to 100%. Deviations from this range may indicate a compromised cardiorespiratory system.

Indications

Pulse oximetry is a valuable, noninvasive tool to monitor a canine's SpO₂. Pulse oximetry and SpO₂ are essential in the early detection of hypoxemia and titration of supplemental oxygen.[1][4][5][6][7][8] Pulse oximetry allows medical personnel to assess the canine's respiratory status and monitor the effectiveness of oxygen therapy. Pulse oximetry is the standard of care in monitoring respiratory and circulatory function. Pulse oximetry guides several categories of therapeutic interventions, including emergent resuscitation, sedation, mechanical ventilation and oxygen therapy, intraoperative procedures, and anesthetic care.[7][8][9][10][11] 

If utilizing anesthesia or sedating medications, it is essential to use pulse oximetry to monitor the canine for hypoxemia and guide oxygen therapy. Clinical studies show that using pulse oximetry reduces the rate of adverse outcomes related to undiagnosed hypoxic events and decreases mortality rates when used with oxygen administration.[12][13][6][14][15]

Contraindications

While utilizing SpO₂ in humans and canines is a relatively safe, quick, and noninvasive procedure, several clinical situations limit the pulse oximeter's ability to obtain an accurate reading. If the comical situation allows, do not place the pulse oximetry sensor on an injured extremity or burned skin, which could have compromised blood flow and tissue perfusion.

SpO₂ measurements can be inaccurate in several situations analogous to human medical scenarios, such as critically ill patients with low perfusion, cold skin, dark skin, motion artifacts, and dyshemoglobins.[1][16][17][18] Pulse oximetry sensors can only differentiate oxygenated and deoxygenated hemoglobin; the sensor cannot detect carboxyhemoglobin or methemoglobin.[19]

Due to a canine's fur and hair, canine pulse oximetry is limited by poor sensor contact and light penetration through tissue. Canines might also require sedating medications or anxiolysis to tolerate the application of medical devices and sensors and remain still during the medical exam. Studies have shown that a canine with a chronic history of vascular disease can also have an inaccurate reading on pulse oximetry. Overall, a pulse oximeter falsely detects hypoxemia during motion and low-perfusion conditions. Medical personnel should be aware of these limitations and be prepared to use alternative methods to assess for hypoxemia.

Additionally, pulse oximetry measures oxygenation levels but not ventilation or carbon dioxide levels in the blood (PaO2). In conjunction with a pulse oximeter, capnography, or end-tidal CO₂ (ETCO₂), is used to evaluate the canine's ventilation status with a CO₂ waveform and PCO₂ level.[19]

Equipment

Medical personnel should be equipped with commercial oximeters designed for canines. These devices ensure proper placement on a canine's tongue, lip, ear, and even the prepuce vulva or webbing of the toes. These mucous membranes allow light to be emitted to measure oxygen saturation levels. If it becomes a situation in which a company needs to ensure the proper equipment is purchased, an adhesive, elastic infant pulse oximeter can be used as well. Commercial human pulse oximeters provide less accurate results when used on a canine.

By spectrophotometry and the Beer-Lambert Law, a pulse oximeter measures peripheral functional hemoglobin or arterial blood oxygen saturation (SpO₂).[2][20] The oxygen saturation from this noninvasive monitor estimates tissue oxygenation. Modern pulse oximeters are lightweight, portable, inexpensive, and provide rapid measurements [2]. The probes are adhesive single-use probes or multi-use clips.[5] Canine pulse oximetry probes are optimized for canine anatomy and hair and should be used when available. The pulse oximeter emits 2 lights and detects light wavelengths on the opposite side of the tissue bed with one sensor.[20][21]

Personnel

Emergent canine care requires a team of 2 or more medical personnel. Best practice integrates the working dog's handler and telemedicine consults for veterinary assistance. The canine’s handler should assist the medical team by placing a breathable muzzle and restraining the canine to ensure the safety of medical personnel and the dog.

Technique or Treatment

The first step in canine assessment is to apply a muzzle. The canine's handler should be asked to place a muzzle and restrain the dog to protect care providers and other team members assisting.

Appropriate sites for canine pulse oximetry probe placement (in order of preference) are the tongue, nonpigmented area of lip, ear pinna, prepuce (male), or vulva (female). In reality, accurate pulse oximetry probes placed on the tongue are only achievable on an unconscious or sedated/anesthetized canine. Human commercial neonatal pulse oximetry adhesive sensors attached to the base of a canine's tail may provide an alternative site.

The pulse oximeter probe should be placed so the light penetrates through tissue directly to the detector. The probe should be adequately secured to the tissue to provide a stable connection and accurate reading. The probe should fit well but not constrict or restrict circulation [8]. Ambient light and excessive movement can interfere with readings. Manufacturer guidelines for all probes should be used to ensure an appropriate probe placement and reading accuracy.

Clinical Significance

Normal canine oxygen saturation levels at sea level are 94% to 100% on room air, similar to humans.[20] Critical levels of 80% correlate to a partial pressure of 60 mm Hg and would prompt interventions for hypoxemia.[20]

Pulse oximeters are generally reliable and accurate; however, they are not calibrated to assess critically low blood oxygen saturation levels. Pulse oximeter readings of less than 70% are not considered accurate.[1][20] At critically low oxygen saturation levels, arterial blood gas measurements are considered more accurate, and the gold standard of determining oxygen saturation is clinically warranted.[3]

Enhancing Healthcare Team Outcomes

Proper training, quality equipment, and adherence to technique and treatment protocols are essential for accurate and effective SpO₂ monitoring. While there are challenges and limitations associated with canine SPO₂ monitoring, it remains a valuable tool in emergent canine care. SpO₂ monitoring in canine casualties can significantly improve patient outcomes and survival rates. Further research and clinical studies are needed to explore the accuracy and efficacy of canine pulse oximetry in different clinical scenarios and to establish standardized protocols and guidelines for its use in emergency canine care. Medical personnel should stay updated on the latest techniques and guidelines related to canine pulse oximetry.