Lung Ultrasound STudy - Diaphragm dysfunction after lung transplant

Diaphragmatic dysfunction (DD) represents an important clinical problem after lung transplant and has a considerable influence on respiratory function and recovery. It frequently results in longer duration of mechanical ventilation; ICU and hospital stay which as a result may lead to further deconditioning. The incidence of diaphragmatic dysfunction following lung transplant surgery has been estimated at greater than 40 per cent. However, to date, its incidence has only been documented retrospectively using EMG techniques (Ferdinande, Bruyninckx, Van Raemdonck, Daenen, & Verleden, 2004). There is little documentation in the literature regarding the natural history and prognosis of diaphragmatic dysfunction in these patients. Ultrasound has been used to identify severe diaphragmatic dysfunction post cardiac surgery (Lerolle et al., 2009). Bedside ultrasound by Intensivists has been shown to be as accurate as fluoroscopy for diaphragmatic dysfunction in patients post cardiac surgery (Sanchez de Toledo et al., 2010). This assessment can be performed at the bedside and avoids the exposure to radiation. By documenting the incidence and extent of this problem, we hope to identify risk factors for developing DD and determine if any of these are preventable with future studies. Methods: Ultrasonographic examinations will be performed in the semirecumbent, 45 degree head up position. Measurements will be taken to assess diaphragm excursion (descent) and diaphragm thickening. For Excursion: Two-dimensional mode will be used to find the best approach and to select the exploration line of each hemidiaphragm. The liver will be used as a window on the right while the spleen will be used on the left hemidiaphragm. All examinations will be recorded on a computer for subsequent blind analysis. A subcostal or low intercostal probe position will be chosen between the anterior and mid axillary lines to obtain the best imaging of the left hemidiaphragmatic dome. The motion will be recorded during the same respiratory maneuvers as for the right hemidiaphragm. The diaphragm inspiratory amplitudes (excursions) will be measured from the M-mode sonography. For the Quiet Breathing and Deep Breathing measurements, the first caliper will be placed at the foot of the inspiration slope on the diaphragm echoic line and the second caliper will be placed at the apex of this slope. For Voluntary Sniff measurement, the amplitude of excursion will be measured on the vertical axis of the tracing from the baseline to the point of maximum height of inspiration on the graph. Several respiratory cycles will be recorded, and measurements will be averaged from at least three different cycles. Presence of ultrasonographic diaphragmatic dysfunction will be defined by diaphragmatic excursion of less than 10mm (Boussuges, Gole, & Blanc, 2009; Kim, Suh, Hong, Koh, & Lim, 2011). The treating team will be notified within 24hours if diaphragmatic dysfunction is identified. For Thickening: A linear transducer will be placed between the eighth and ninth intercostal space, between the anterior and medial axillary lines. Measurements of diaphragm thickness will be taken in B-mode at end-inspitation and end-expiration during normal spontaneous breathing. An average will be calculated from three independent breaths. Thickening fraction will be calculated as Thickness at End-inspiration minus Thickness at End expiration; divided by thickness at End-expiration (Matamis et al, 2013). Diaphragmatic thickening fraction can be used as an index of diaphragmatic efficiency as a pressure generator (Vivier et al, 2012) Each examination will be conducted by the physiotherapist or physician and will take approximately 15-20 minutes to complete at each time-point ie. pre-op, Day 1, Week 1, Month 1 and Month 3. To complete all five examinations we estimate it will require a total of 75 minutes per participant.