A 7-year-old boy after playing with a cat suddenly developed problems with breathing. Objectively, the boy is pale. frightened, and sits, leaning onto his arms. His body temperature is 36.6°C. heart rate 120/min., respiration rate min., speaks in syllables. The exhale 42/ is long and accompanied by wheezing Percussion detects a handbox resonance over the lungs. An inhalation of ventolin (salbutamol) solution nebulizer. What can help assess the child's started via a need for oxygen therapy in this case?