Breathe In ... Breathe Out ... Stop Breathing: Does Phase of Respiration Affect the Haller Index in Patients With Pectus Excavatum?

OBJECTIVE. The purpose of this article is to determine whether the phase of respiration at the time of imaging affects chest wall measurements and compression of internal structures in patients with pectus excavatum. MATERIALS AND METHODS. Forty-seven patients (median age, 14 years) imaged for preoperative pectus excavatum underwent limited axial balanced steady-state free precession MRI of the chest at inspiration, expiration, and stop quiet breathing. Two radiologists, who were blinded to prior measurements, independently calculated the Haller index, asymmetry index, and sternal tilt in each phase of respiration. Compression of internal structures was recorded. Statistical comparison was performed. RESULTS. The Haller index was significantly lower at inspiration, compared with stop quiet breathing and expiration, with medians (interquartile ranges) of 3.96 (3.27-4.61), 5.16 (4.02-6.48), and 5.09 (4.14-6.63), respectively (p < 0.0001 for both). No significant difference in Haller indexes was observed between expiration and stop quiet breathing (p = 0.1171). Of 11 patients with a Haller index less than 3.25 at inspiration, eight (72.7%) had an index greater than 3.25 on expiration and stop quiet breathing, which accounted for 17% (8/47) of all patients imaged. Compression of the liver or vascular structures was present in 24 (51%) patients. There was no significant difference in the asymmetry index, sternal tilt, or right heart compression between phases of respiration. CONCLUSION. Obtaining the Haller Index at inspiration may result in a value significantly lower than that at expiration, potentially affecting surgical and financial decision making. Compression of the liver and vascular structures was observed in 51% of patients, but additional research is needed to determine the clinical significance of this finding.