Nebulization during spontaneous breathing, CPAP, and bi-level positive-pressure ventilation: a randomized analysis of pulmonary radioaerosol deposition.

BACKGROUND There have been few reports of factors affecting aerosol delivery during noninvasive ventilation (NIV). Nebulization is a standard practice, and our objective was to determine the effect of spontaneous breathing (SB) and NIV mode on lung technetium-99m ((99m)Tc) deposition in subjects with normal lungs. METHODS Thirteen health care volunteers were submitted to a randomized radioaerosol nebulization with (99m)Tc during SB, CPAP (10 cm H2O), and bi-level positive-pressure ventilation (bi-level; inspiratory-expiratory pressures of 15/5 cm H2O). NIV was performed via a ventilator (VPAP II ST-A, ResMed, Sydney, Australia). The radioaerosol deposition was evaluated by pulmonary scintigraphy after 10 min of inhalation. Regions of interest (ROIs) were outlined on the left lung (LL), right lung (RL), and trachea (TRQ). The average number of counts/pixel in each ROI was determined, and the ratio of lung and trachea was calculated. RESULTS The three techniques showed comparable lung deposition. Analysis of radioaerosol deposition in the lungs showed a mean count at RL of 108.7 ± 40 with CPAP, 111.5 ± 15 with bi-level, and 196.6 ± 167 with SB. At LL, the values were 92.7 ± 15 with CPAP, 98.4 ± 14 with bi-level, and 225.0 ± 293 with SB. There was no difference between the means of radioaerosol deposition in RL, LL, or TRQ, as well as the lung calculated ratio (LCR = [RL + LL]/TRQ), which was similar in comparing ventilatory strategies. CONCLUSIONS Based on our data, there is an equivalent deposition of inhaled substances in individuals with healthy lungs when SB, CPAP, and bi-level are compared.