Approach
Typically, the diagnosis is clinical; cough, tachypnoea, retractions, and wheeze are common clinical presentations. Other symptoms include rhinitis, fever, a fluctuating clinical course, and apnoea.[43] Diagnostic studies are primarily used to confirm the clinical impression or rule out other causes.
Clinical presentation
Bronchiolitis is primarily a disease of infancy and is rare in children over the age of 3 years. It is usually preceded by several days of upper respiratory tract symptoms, such as rhinitis and cough. Fever is common, but it is usually low-grade or moderate (<40°C [<104°F]).[46] The cough gradually increases in severity, and can sound wet or croupy. Symptoms of lower respiratory tract disease then develop, including retractions, audible wheezing, and laboured breathing. Additional systemic signs may occur, such as irritability, malaise, and poor feeding.
Physical examination
Usually reveals tachypnoea, retractions, wheezes, crackles, and sometimes thoracoabdominal asynchrony. Not all infants present with wheezes or crackles, and some clinical guidelines do not require these physical findings to make the diagnosis.[43]
The hallmark of bronchiolitis is fluctuating clinical findings, often within short time periods.[47] Some infants with respiratory syncytial virus (RSV) bronchiolitis can present with apnoea.[1] More severely affected infants demonstrate hypoxaemia and very laboured breathing.
Investigations
In the majority of cases the infection can be diagnosed clinically, and diagnostic studies are not necessary. Nonetheless, one single-centre study found that inappropriate use of diagnostic tests was prevalent in a population of hospitalised infants with a diagnosis of acute bronchiolitis; personal history of atopic dermatitis, longer duration of hospitalisation, and number of siblings at home were independent predictors of inappropriate use of diagnostic tests and treatments.[48]
Pulse oximetry
A simple, non-invasive method to assess for hypoxaemia and should be performed in any infant with more than mild symptoms for whom hospitalisation is being considered.[49] Although there is not complete consensus among different guidelines, most recommend the use of intermittent rather than continuous pulse oximetry monitoring.[50] In non-hypoxaemic inpatients, intermittent pulse oximetry did not affect the rate of escalation of care or duration of oxygen therapy, compared with continuous pulse oximetry monitoring.[51]
Guideline statements also differ in their recommended lowest acceptable oxyhaemoglobin saturation limits. The American Academy of Pediatrics recommends that infants who are hypoxaemic should be given supplemental oxygen to maintain an oxyhaemoglobin saturation (saturation of peripheral oxygen, SpO₂) of at least 90%, the point at which small decreases in arterial partial pressure of oxygen (PaO₂) are associated with large changes in SpO₂.[43][52]
One randomised controlled trial reported that a target SpO₂ of 90% was as safe and effective as a target SpO₂ of 94% in infants hospitalised with viral bronchiolitis. There was no significant difference between the two groups in time to resolution of symptoms, return to adequate feeding, re-admission to hospital, or adverse events. The infants with a target SpO₂ of 90% required a shorter duration of supplemental oxygen and were fit for hospital discharge sooner.[53]
No long-term neurodevelopmental outcome studies have been conducted comparing the use of lower SpO₂ targets (>90%) with higher ones (>94%). Because fever and acidosis shift the oxyhaemoglobin desaturation curve to the right, a higher SpO₂ goal may be more appropriate for children with those conditions: for example, some guidelines recommend an SpO₂ goal >92%.[54][55]
Other signs of impaired respiratory function, such as increased work of breathing or retractions, can be used as factors in deciding on supplemental oxygen therapy.
Infants with underlying cardiac or pulmonary disease may have baseline abnormalities in oxygenation. In these patients, the threshold for using supplemental oxygen may be higher.
Testing for RSV
Virological testing for RSV and other respiratory viruses can be performed, but it is not necessary for the diagnosis of bronchiolitis.[15] Reverse transcriptase polymerase chain reaction (RT-PCR) is an assay for detecting viral nucleic acid that is highly specific and much more sensitive than enzyme-linked immunosorbent assay (ELISA).
Test results can be used for infection control cohorting in the hospital setting, but there is some question as to whether testing adds any advantage over use of routine contact precautions.[47][54]
Testing is recommended in infants receiving immunoprophylaxis with palivizumab or nirsevimab who experience a breakthrough episode of bronchiolitis. If RSV is detected, monthly immunoprophylaxis should be discontinued because of the low likelihood of a second RSV infection in the same year.[43]
In addition to evaluation of the individual patient, viral testing can lend insight into the epidemiology of respiratory pathogens, and identify new pathogens or emerging respiratory epidemics.[50]
Imaging and other studies
Because there are no pathognomonic signs on chest x-ray, it should be performed only if there is a strong suspicion for bacterial pneumonia (e.g., fever >40°C [>104°F] and focal crackles) or when other complications (e.g., pneumothorax) are being considered.[56]
Full blood count or serum chemistry should not be performed for diagnosis of bronchiolitis, but may be indicated if the patient's clinical status is severe enough to warrant evaluation.
Use of this content is subject to our disclaimer