Efeitos da administração de pressão positiva contínua em vias aéreas de modo não invasivo sobre a aeração do parênquima pulmonar em pacientes com doença pulmonar obstrutiva crônica

Abstract

Introduction: The Chronic Obstructive Pulmonary Disease (COPD) is characterized by different stages of chronic bronchitis and pulmonary emphysema with air trapping and dynamic hyperinflation. These conditions lead to respiratory muscles fatigue and need of ventilator support. Noninvasive positive pressure support ventilation (NIPPV) is the treatment of choice for COPD exacerbations with mortality reduction. Continuous positive airway pressure (CPAP) effects on hyperinflation is controversy; it can worsen, attenuate or have no effect. Imaging methods can facility the comprehension of CPAP effects on COPD patients, including regional effects on lung parenchyma. Objectives: To evaluate the effect of CPAP application by NIPPV-CPAP on pulmonary hyperinflation in COPD patients. Patients and Method: This is a prospective and interventionist study that evaluated 11 patients with COPD. All patients were evaluated by high resolution CT (HRCT), without and with NIPPV-CPAP (5, 10 and 15 cmH2O) applied by nasal mask. The pressures sequence was randomized and the HRCT images were done in Functional Residual Capacity. HRCT images were done in three regions for each level of pressure: apex (2 cm above the aortic arc), hilar (1cm below the carina) and basis (2 cm above the diaphragm). The units with densities lower than -950 UH were considered hyperinflated. For analysis the results were divided in full lung and in regions: apex, hilar and basis and ventral, medial and dorsal. Results: It was observed a pulmonary density reduction and an increase of pixels on hyperinflated areas with application of CPAP levels greater than 10 cmH2O in all analyses (p<0,05). In grouped lung analysis the mean density was reduced gradually from -846 UH (without CPAP), -849 UH (5 CPAP of cmH2O), -859 UH (10 CPAP of cmH2O) to -869UH (15 CPAP of cmH2O) (p<0,05). In subdivisions, comparing without CPAP and with CPAP of 15 cm cmH2O: in apex it was observed reduction from -840 to -871UH (p<0,05), in hilar region from -848 to -882 UH (p<0,05), in basis from -848 to -876 UH (p<0,05), in ventral region from -859 to -885 UH (p<0,05), in medial region from -848 to -864 UH (p<0,05) and in dorsal region from -832 to -860UH (p<0,05). It was also noted an increase of the percentage of pixels on hyperinflated areas in the majority of analyses with CPAP of 10 and 15 cmH2O (p<0,05). In 2 patients it was observed elevation of mean pulmonary density with CPAP of 5 cmH2O. It was observed that pulmonary parenchyma aeration was distributed in a non homogeneous way with predominance of the apex area comparing with basis of the lung and of the ventral area comparing with dorsal area. Conclusion: The CPAP application by NIPPV resulted in increase of pulmonary hyperinflation with levels of CPAP of 10 and 15 cmH2O detectable by HRCT. However this was not homogeneous, a subgroup of patients had aeration reduction with CPAP of 5 cmH2O. The distribution of aeration induced by CPAP is heterogeneous inside pulmonary parenchyma and follows the heterogeneous basal hyperaeration.