Tidal Breathing Studies
Tidal breathing analysis (TBA) is an attractive method of respiratory function testing because it can be done without the need for sedation or the requirement of forced expiratory maneuvers [21]. TBA can be performed using a face mask and pneumotachometer, but this can be challenging to apply in infants since it requires the infant to maintain a seal over the nose and mouth with the mask, which can also potentially alter infant breathing patterns. Electromagnetic inductance plethysmography (EIP) measures changes in the electromagnetic field created by tidal breathing while wearing a metallic vest through which a low voltage is applied. Sautter, et al used EIP to perform TBA in a cohort of 36 infants with bronchiolitis [22]. EIP was successfully performed in 80% of the infants, and a significant increase in the ratio of the total expiratory time over the inspiratory time (Te/Ti) was observed after inhalation of normal saline. The ratio of the time to peak expiratory flow over total expiratory time (Tptef/Te) decreased after administration of nebulized normal saline, but this change was not statistically significant. This study demonstrates the feasibility of using EIP for TBA and suggests that further study of the physiologic effects of inhaled normal saline in bronchiolitis are warranted. Traditionally TBA has been done manually, which is a time consuming and laborious process. A study by Gomes et al. compared two computing systems, AutoCAD and MATLAB, in their ability to obtain automated TBA data [23]. Thoracoabdominal area averages calculated with both systems were comparable, but MATLAB required less time and less user training to complete. They suggest that it could be used in the clinic setting to calculate or derive tidal volume measurements.