Upper airway obstruction is a potentially lethal condition, in both children and adults and requires prompt diagnosis and management. The degree of emergency with which it needs to be addressed depends on the severity of the obstruction since complete obstruction leads to rapid respiratory and subsequent circulatory failure.
Clinical presentation of the patient depends on the extent of the upper airway obstruction and symptoms include panic, choking, confusion, dyspnea, hoarseness, gasping, wheezing, stridor, tachypnea, tachycardia, hypertension, and pulsus paradoxus. Cyanosis sets in rather late, as the hypoxemia becomes severe.
Increased work of breathing indicates respiratory distress but does not necessarily signify airway obstruction  .
Clinical signs such as increased use of accessory respiratory muscles, seen as suprasternal, supraclavicular, subclavicular, intercostal and subcostal retractions or even paradoxical chest and abdomen movement can be observed. As oxygenated hemoglobin level decreases, the patient becomes agitated, develops altered sensorium, then becomes unconscious and finally lapses into a coma. Several symptoms are suggestive of a specific cause of the obstruction e.g. fever and barking cough imply croup; low pitched expiratory stridor may be encountered in epiglottitis; choking and aphonia with sudden onset could mean foreign object aspiration; urticaria and facial swelling are seen in anaphylaxis. If the obstruction is mild, the patient will be able to speak in full sentences, whereas more severe obstruction leads to fractioned words.
If the onset of the condition is gradual, exertional dyspnea is the first complaint, with no hypoxemia or hypercapnia symptoms at rest . As the obstruction grows more severe, dyspnea and stridor occur at rest  due to hypoventilation  .
On auscultation, an absence of breath sounds should raise suspicion of complete obstruction while foreign sounds mean partial obstruction. Stridor is found during inspiration if the location of the obstruction is laryngeal or during expiration if the obstruction is located lower in the respiratory system.
The clinician should also observe or inquire about the presence of other diseases, such as cardiac malformations, burns, bleeding that might obstruct the airway, anaphylaxis and periodically reassess patient status.
Spirometry and flow-volume loops are applicable in partial obstruction cases and offer valuable parameters like forced expiratory volume per second (FEV1), peak expiratory flow rate (PEFR), maximal voluntary ventilation (MVV), maximal mid-expiratory flow (MEF50) and maximal mid-inspiratory flow (MIF50)   , that may also indicate if the obstruction is fixed or variable. For instance, the MEF50/MIF50 ratio is increased in variable extrathoracic lesions and decreased in variable intrathoracic lesions . The FEV1/MEF ratio is useful, for instance, in patients with vocal cord paralysis  .
Obstructive sleep apnea, a frequent cause of chronic upper airway obstruction in adults, as well as neuromuscular diseases, Parkinson's disease, and episodic laryngeal dyskinesia, have a particular "sawtooth" appearance on the flow volume curves . It is important to remember during interpretation of the results that posture and activity influence the flow volume curves  .
Additional imaging techniques include spiral computer tomography and optic fiber bronchoscopy; these are especially useful in adult patients, especially those suspected of having a malignancy obstructing the upper respiratory system, but also in children suspected to have tracheomalacia. Another cause of upper respiratory obstruction in children may be lingual thyroglossal duct cysts,   and symptomatic patients should be evaluated with magnetic resonance imaging .