Pulse Oximetry Coupled With Spirometry in the Emergency Department Helps Differentiate an Asthma Exacerbation From Possible Vocal Cord Dysfunction

Abstract

Nolan PK, Chrysler M, Phillips G, Goodman D, Rusakow LS. Pediatr Pulmonol. 2007;42(7):605–609 PURPOSE OF THE STUDY. These investigators sought to determine if they could find evidence for vocal cord dysfunction (VCD) in asthmatic adolescents whose condition failed to respond adequately to treatment in the emergency department (ED) for a presumptive asthma exacerbation. STUDY POPULATION. Subjects with wheezing presenting to the ED of an urban children's hospital were recruited. Inclusion criteria were age 12 to 21 years, failure to respond to treatment for wheeze sufficiently to allow discharge, and pulse oximetry reading of ≥97%. Exclusion criteria were having other cardiac or pulmonary disease, inability to perform spirometry, or need for endotracheal intubation. METHODS. Spirometry with standard techniques was performed by using a computer-linked pneumotachygraph and appropriate software to capture both expiratory and inspiratory flow volume curves. Spirometric results were classified as small airway obstruction, variable extrathoracic airway obstruction (consistent with VCD), a combination of the 2 previous findings, or normal airflow. RESULTS. Twenty ED encounters with 17 subjects were studied. Only 5 (25%) of the encounters included spirometric evidence of small airway obstruction, but 12 of 20 had evidence for VCD (ie, variable extrathoracic airway obstruction on the inspiratory loop). These 12 included 3 that also had evidence for small airway obstruction. There were 6 encounters with no abnormality on spirometry. CONCLUSIONS. Spirometry may identify presumptive refractory asthma exacerbations that, instead, are episodes of VCD. REVIEWER COMMENTS. Several years ago we treated an 8-year-old boy who had been admitted to the hospital for status asthmaticus 4 times in 1 month but never had an oxygen requirement. A videotape of the boy when he was symptomatic (provided by the parents) showed obvious stridor, not wheezing. Similarly, in this study the cardinal observation was refractory “wheeze” without arterial desaturation. Computerized spirometry is not universally available in the ED, and in addition, not all such units have software capable of displaying the inspiratory limb of the flow-volume loop. However, in busy ED environments with large asthmatic populations, availability of this measurement should greatly aid the classification of wheezing events. Pediatricians need to be more aware that VCD may present symptoms that mimic asthma.