Breathing levels during inspiration and expiration HRCT

Abstract

Introduction: Inadequate breathing manoeuvres during inspiratory and expiratory High Resolution Computed Tomography (HRCT) may conceal differences in lung density. Although spirometer-controlled HRCT is advocated, this technique is not common practice. The aim of this study was to determine breathing levels during inspiration and expiration HRCT as achieved after standard breathing instructions by the radiology assistant.

Methods: during HRCT Inspiratory Capacity (IC_insp,CT) and Expiratory Reserve Volume (ERV_exp,CT) were measured in 29 male construction workers (age 49 ±7 yrs; FEV₁/VC 75± 0,1 %) at risk for silicosis and compared with lung function (IC_LF, ERV_LF) performed after HRCT under similar conditions by a respiratory technician according to ERS/ATS criteria. Vital Capacity was measured during lung function (VC_LF) and for HRCT calculated by adding IC and ERV using two different manoeuvres (VC_constr,CT). Instructions of the radiology assistant and the moment at which the scan was started were recorded.

Results: IC_insp,CT was 0.85 l (0.7 l) and VC_constr,CT (0.6 l) 0.88 l lower as compared to lung function (p< 0,01). The difference was > 20% in 16 and 13 workers respectively. ERV did not differ significantly between HRCT and lung function. In 15/29 workers ERV_exp,CT exceeded ERV_LF because of changes in resting breathing level. Expiration HRCT was started during the expiration phase in 24/29 workers.

Conclusion: inspiratory and expiratory breathing levels during HRCT did not reach maximal levels as achieved during lung function. Spirometer-controlled or -triggered HRCT should be considered. However, the effect of these methods on the diagnostic yield of HRCT in interstitial lung disease has yet to be determined.