A 3-year-old girl is brought to a pediatric clinic by her parents, who report that over the past few days she has developed a distinctive, harsh cough resembling a 'barking seal.' They note she's also had a runny nose and a low-grade fever, particularly at night, which seems to worsen her breathing. Her mother describes a 'whistling sound' when the child breathes in, especially when agitated. On examination, her temperature is 38.0 °C, respiratory rate 28 breaths/min, and oxygen saturation 96% on room air. She exhibits audible inspiratory stridor, particularly when crying, and there is mild suprasternal retraction. Auscultation of the lungs reveals clear breath sounds bilaterally without wheezes or crackles. Given this presentation, what is the most likely etiology and the immediate priority in her management?

A 3-year-old girl is brought to a pediatric urgent care clinic by her frantic parents who report that approximately an hour after bedtime, a distinctive "seal-like" barking cough emerged from her room. Upon checking, they found her struggling to breathe, producing a high-pitched whistling sound with each inhalation. Her parents mention she had a mild runny nose and a low-grade fever (37.8°C) for the past two days, but otherwise has been generally healthy. She has no history of choking episodes, and there are no small objects accessible in her sleeping area. On physical examination, the child is anxious and exhibits inspiratory stridor at rest, supraclavicular and intercostal retractions, and a respiratory rate of 40 breaths per minute. Her heart rate is 130 beats per minute. She is able to swallow her own secretions, and her voice, while hoarse, is present. Auscultation reveals clear breath sounds bilaterally with prolonged inspiration. Capillary refill time is less than 2 seconds, and her skin is warm and dry. Her oxygen saturation is 95% on room air. Lab results are pending. Which of the following is the most likely diagnosis and the appropriate initial management strategy for this patient's condition?

A 3-year-old girl is brought to an outpatient clinic by her guardians due to a persistent and worsening cough and noisy breathing. For the past three days, she has had symptoms consistent with a common cold, including a low-grade fever and rhinorrhea, which the parents managed with symptomatic care at home. However, last night, her cough developed a distinct "barking" quality, and her breathing became noticeably labored, especially when agitated. This morning, her inspiratory stridor is audible even at rest. She has no significant past medical history and is up-to-date on routine vaccinations. Her vital signs upon arrival are: temperature 38.50C, heart rate 130/min, respiratory rate 30/min, blood pressure 95/60 mmHg, and oxygen saturation 96% on room air. On physical examination, she appears fatigued but alert. There is clear evidence of inspiratory stridor, nasal flaring, and mild intercostal retractions. Her breath sounds are somewhat diminished, but no wheezes or crackles are heard. Capillary refill is less than 2 seconds, and mucous membranes are moist. A lateral neck radiograph, if performed, might reveal characteristic findings. Considering these findings, what is the most likely diagnosis and the critical initial intervention in an outpatient setting?

A 3-year-old girl is brought to an urgent care center by her parents due to a worsening cough and breathing difficulty over the past day. Initially, she had a low-grade fever and mild rhinorrhea for 24 hours. Her cough has progressively developed a distinctive barking, seal-like quality, especially at night. Her voice has become noticeably hoarse. On arrival, her temperature is 37.8°C, heart rate is 115/min, respiratory rate is 32/min, blood pressure is 90/55 mmHg, and oxygen saturation is 93% on room air. Physical examination reveals a distressed child with visible accessory muscle use. Auscultation of her chest reveals clear breath sounds, but prominent inspiratory stridor is heard at rest. Oral examination shows no pharyngeal exudates. Her capillary refill time is less than 2 seconds. Given this presentation, what is the most likely diagnosis and the subsequent most appropriate immediate management strategy?