Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to measure a dog's respiration rate [title] Take your dog's respiration rate when it is calm. [step] In order to determine your dog's respiration rate, make sure that it is calm. Dogs naturally increase their blood oxygen levels while at play or when anxious.

Ending1: However, sneezing, growling, lack of coordination, panting, and labored breathing are all signs of respiratory problems. [substeps] Allow the dog to " cool down " by putting a towel over its nose and mouth to protect it. Ending2: This increases their heart rate, which speeds up the respiration process. If your dog has an irregular respiratory rate, and your dog is disabled, it is more likely that it is struggling to breathe. Ending3: Some dogs may already be calm, but they may be more relaxed with night time play. [substeps] A high level of pressure on the lungs can draw blood vessels from the sinuses and cause vomiting or difficulty breathing. Ending4: This means that they breathe more in order to circulate more oxygen through their systems. Alternatively, if your dog has just finished playing and is hot, it will increase its breathing rate to exhale the heat in their bodies, in an effort to cool themselves down.

Answer format: ending1/ending2/ending3/ending4