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. Author manuscript; available in PMC: 2016 Apr 13.
Published in final edited form as: J Allergy Clin Immunol Pract. 2013 Jun 28;1(4):387–393. doi: 10.1016/j.jaip.2013.05.005

Figure 3. Characteristic impedance curve of VCD.

Figure 3

A) Patient#2, 14 yo male with VCD and muscular tension dysphonia. Z5 curve shows dramatic spike (> 10 cmH2O/L/sec) in impedance with onset of inspiration (vertical lines) correlated with vocal cord closure and flattening in X. Severe respiratory impairment detected by spirometry. B) Patient#3, 48 yo female with VCD and asthma diagnosed by endoscopy. Spikes in Z5 are also seen during inspiration. Spirometry shows biphasic trapezoidal truncation.