Ultrasonographic assessment of diaphragmatic performance in two chronic obstructive pulmonary disease phenotypes admitted with acute exacerbation and its relation to outcome

Abstract

Introduction Diaphragm is considered a key point in the prognosis of acute chronic obstructive pulmonary disease (COPD) exacerbations. Diaphragmatic performance is an issue that is not fully studied in different COPD phenotypes. Aim To assess diaphragmatic performance by chest ultrasound (US) in patients with two COPD phenotypes admitted to respiratory ICU with an acute exacerbation and to assess its relation to outcome. Patients and methods US assessment of diaphragm position, excursion, inspiratory time, velocity, thickening fraction, and excursion-time (E-T) index was done for 100 patients with COPD with two phenotypes, that is, chronic bronchitis (CB) and emphysema (E), who were admitted at the respiratory ICU of Abbassia Chest Hospital. Assessment was done for all patients within 24 h of admission. Primary end point was the need for mechanical ventilation (MV) and secondary end point was discharge or ICU mortality. Results Position of the diaphragm was at the –six to eight intercostal space, with mean of 7.114 ± 0.404, in the E group and at the –five to seven intercostal space, with a mean of 5.946 ± 0.524, in the CB group, with P value less than 0.001. There was a higher velocity in E (3.324 ± 1.151 cm/s) compared with CB (2.757 ± 1.023 cm/s), with P=0.011, and a higher expiratory thickness in CB (3.312 ± 0.806) versus E (2.584 ± 0.786 mm), with P value less than 0.001. Regarding the need for MV, 62 (62%) cases required MV (nine noninvasive mechanical ventilation and 53 invasive mechanical ventilation). The need for MV was higher in E compared with CB group (35/50 cases, 70%, and 27/50 cases, 54%, respectively; P<0.001). There was a significant shorter inspiratory time and a lower E-T index in both phenotypes among patients who required MV (P=0.007 and 0.045, respectively). The cutoff value of the inspiratory time and the E-T index in predicting the need to MV was less than 0.65 s and less than 1 cm/s, respectively. Conclusion US assessment of the diaphragm during acute COPD exacerbations may help anticipate the need for MV. The need of MV was related to a shorter inspiratory time (cutoff point <0.65 s) and a lower E-T index (cutoff point <1 cm/s). There was no difference between CB and E phenotypes in this aspect.