ObjectiveTo investigate the effects of different peak flow on the airway pressure to explore a preferable value of peak flow in ventilation during cardiopulmonary resuscitation (CPR) under volume control ventilation (VCV) mode and decreasing-wave. Methods30 patients who underwent CRP in the emergency unit between January 2012 and 2014 was recruited in the study. When the chest compressions came into a stable state by a same doctor,the peak flow was set at 50 L/min and 30 L/min respectively while other parameters fixed in the same patient. Then the pressure-time curve of a respiratory cycle was randomly frozen to achieve the highest peak pressure in inspiratory phase. ResultsThe highest peak airway pressures were (54.1±4.9)cm H2O and (35.5±5.3)cm H2O when the peak flow were set at 50 L/min and 30 L/min respectively with significant difference. The incidence of peak airway pressure greater than 40 cm H2O was 96.7% and 26.7%,and the incidence of peak airway pressure greater than 50 cm H2O was 76.7% and 0%,respectively. Compared with 50 L/min,the peak flow of 30 L/min obviously reduced the peak pressure (P=0.000). ConclusionIn the mechanical ventilation during CPR using VCV mode and decreasing-wave,compared with peak flow of 50 L/min,smaller peak flow of 30 L/min can significantly reduce peak airway pressure,and significantly reduce the adverse effects to ventilation by repeated violent changes in airway pressure caused by continuing chest compressions,and make airway peak pressure under 40 cm H2O in most patients,so it is a reasonable and safe choice.
ObjectiveTo analyze the sensitivity of peak flow meter screening in different subgroups of chronic obstructive pulmonary disease (COPD). MethodsA total of 156 outpatients with COPD from Peking Union Medical Hospital from May 2013 to December 2014 were recruited in the study. Each patient's symptoms,history of exposure to risk factors,and the times of exacerbation in last year was recorded. All patients completed CAT,mMRC,the St George's Respiratory Questionnaire (SGRQ),6 minutes walking test,spirometry,and peak expiratory flow (PEF) by peak flow meter. ResultsUsing the cut-off of PEF%pred=80%,the PEF detected 120 COPD patients in 156 subjects. The predictive factors of abnormal PEF%pred in COPD was FEV1%pred and the total score of SGRQ (P<0.05). PEF screening could identify 76.9% of COPD patients,30.0%-60.0% of patients of less symptoms (mMRC<2 or CAT<10 or SGRQ<25),83.3%-90.9% of COPD patients with more symptoms (mMRC ≥ 2 or CAT ≥ 10 or SGRQ ≥ 25),27.7% of COPD patients with mild airflow limitation,68.5% of COPD patients with moderate airflow limitation,83.3% of COPD patients with moderate to very severe airflow limitation. When grouped by GOLD combined assessment method,PEF screening could identify 35.2% of patients of group A,75.0% of patients of group B,and 95.9% of patients of group C and D. The cut-off value of PEF% pred=80% showed low sensitivity to early stage of COPD,but when using the cut-off value of PEF% pred=95%,that sensitivity increased signifcantly. ConclusionsPeak flow meter may be used as a tool to screen COPD. It can identify part of COPD patients especially for those patients with more symptoms,requiring regular treatment,with deteriorated pulmonary function and high risk of exacerbation.