高频通气(HFV)是一种高通气频率和低潮气量的通气方式，其通气频率至少为机体正常呼吸频率的4倍，而潮气量近于或小于解剖死腔。其主要类型包括：高频正压通气、高频喷射通气和高频振荡通气等。其中，高频振荡通气(HFOV)是目前公认的最先进高频通气技术，在临床中应用最广泛。
ObjectiveTo investigate the physiologic effects of different pressure assist (PA) on ventilatory status,oxygenation and work of breathing (WOB) when a new generation of proportional assist ventilation (PAV) is applied in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). MethodsA prospective,crossover randomized physiologic study was performed.80%PA,60%PA and 40%PA was sequentially randomized to be applied with the duration of 30 minutes,and pressure support ventilation (PSV) with the duration of 30 minutes was applied before each PA.Ventilatory status, oxygenation,dyspnea indexes in PSV and different PA were compared,and WOB of patients and ventilator were compared in different PA. ResultsTwenty-eight patients were recruited into the study.With the decrease of PA,peak inspiratory pressure (PIP),mean airway pressure (Pm),and tidal volume (VT) decreased gradually (P>0.05),respiratory rate (RR) increased gradually (P<0.05),while minute volume (MV),heart rate (HR),systolic blood pressure (SBP),mean arterial pressure (MAP),pH,arterial carbon dioxide tension (PaCO2),and arterial oxygen tension/inspired oxygen fraction (PaO2/FiO2) did not change significantly (P>0.05).Compared with PSV mode,PIP increased significantly in 80%PA (P<0.05),decreased significantly in 60%PA and 40%PA (P<0.05).Pm did not change significantly in 80%PA (P>0.05),decreased significantly in 60%PA and 40%PA (P<0.05).VT increased significantly in 80%PA (P<0.05),decreased significantly in 60%PA and 40%PA (P<0.05).RR did not change significantly in 80%PA (P>0.05),increased significantly in 60%PA and 40%PA (P<0.05).MV did not change significantly in 80%PA (P>0.05),decreased significantly in 60%PA and 40%PA (P<0.05).With the decrease of PA,Borg score and scale for accessory muscle use increased gradually (P<0.05).Compared with PSV mode,Borg score and scale for accessory muscle use did not change significantly in 80%PA (P>0.05),increased significantly in 60%PA and 40%PA (P<0.05).WOB of patients in 40%PA was significantly higher than that in 60%PA (P=0.000) and that in 80%PA (P=0.000),while which in 60%PA was significantly higher than that in 80%PA (P=0.000).On the contrary,WOB of ventilator in 40%PA was significantly lower than that in 60%PA (P=0.004) and that in 80%PA (P=0.000),while which in 60%PA was significantly lower than that in 80%PA (P=0.000). ConclusionThe new generation of PAV can safely and effectively provide respiratory support to patients with AECOPD.Respiratory pattern,levels of dyspnea and accessory muscle use in 80%PA are similar with those in PSV.With the decrease of PA,levels of spontaneous breathing and WOB increase and dyspnea worsens.PAV can promote spontaneous breathing and prevent respiratory muscle disuse atrophy even more, but easily lead to respiratory muscle fatigue with inappropriate use.
Objective To investigate the risk factors for early progression in patients with acute respiratory distress syndrome (ARDS), and to provide a reference for early detection and intervention of high-risk patients with ARDS progression. Methods Data from multicenter mechanically ventilated patients with mild to moderate ARDS were retrospectively analyzed. According to the severity grade of 72 h ARDS, the patients were divided into an early progressive group and a non-progressive group. Chi-square test was used to compare the risk factors of ARDS patients and the prognosis of the two groups were analyzed by Logistic regression. Results A total of 355 patients with mild to moderate ARDS were included in invasive mechanical ventilation, of which 97 patients (27.3%) progressed after 72 hours. 78.4% were female in the progressive group and 64.0% were female in the non-progressive group. Compared with the non-progressive group, the patients with ARDS in the progressive group had shorter 28-day no mechanical ventilation, higher ICU mortality, and lower survival rate at 30 days and 60 days（P<0.05）, but there was no significant difference in the length of ICU stay between the two groups (P>0.05). Univariate and multivariate regression analysis showed that the patients with ARDS in the progressive group had lower baseline oxygenation index (OR=0.979, 95%CI 0.961 - 0.986, P<0.01), higher peak airway pressure (OR=1.068, 95%CI 1.017 - 1.121, P<0.01), higher lactate level (OR=1.224, 95%CI 1.057 - 1.417, P<0.01), higher tidal volume (OR=1.159, 95%CI 1.002 - 1.341, P<0.05), higher age (OR=1.373, 95%CI 1.051 - 1.082, P<0.01), and more male patients (OR=2.583, 95%CI 1.336 - 4.995, P<0.05). Conclusions Early progression is common in mild to moderate ARDS patients with mechanical ventilation. The progressive group has shorter duration of 28 days without mechanical ventilation, higher ICU mortality and lower 30-day and 60-day survival rate than the non-progressive group. Male, low baseline oxygenation index levels, high peak airway pressure, tidal volume, lactate levels, and higher age are risk factors for early progression in patients with mild to moderate ARDS.