title: Physiological Significance of Well-tolerated Inspiratory Pressure to Chronic Obstructive Pulmonary Disease Patient with Hypercapnia During Noninvasive Pressure Support Ventilation.
abstract: The inspiratory pressure is often set by tolerance of chronic obstructive pulmonary disease (COPD) patient during noninvasive pressure support ventilation (PSV). However, physiological effects of this setting remain unclear. This study was undertaken to assess the physiological effect of highest tolerated assist level on COPD patient.  The baseline inspiratory pressure (PS) was titrated by tolerance in 15 severe COPD patients with hypercapnia during acute exacerbation. In addition to the baseline PS, an additional decrease by 25% (PS- = 75% PS) or increase by 25% (PS+ = 125% PS) of PS was applied to the patients. Each level lasted at least 20 minutes. Respiratory rate (RR), tidal volume (Vt), inspiratory effort (PTPpesin/min), and neuro-ventilatory coupling (VE/RMS%) were measured. Asynchrony Index (AI) was calculated.  The Vt and VE/RMS% were significantly increased by PS level (Vt: 561 ± 102 ml, VE/RMS%: 1.06 ± 0.42 L/%, comfort score: 7.5 ± 1.1). The inspiratory muscles were sufficiently unloaded (PTPpesin/min 56.67 ± 32.71 cmH2O.S/min). In comparison with PS, PS+ resulted in a further increase in Vt, VE/RMS% and AI (P < 0.01), with no further reduction in neural drive (RMS) and respiratory muscle activity (P > 0.05).  Increasing inspiratory pressure significantly enhances the VE/RMS% and Vt. However, the inspiratory pressure higher than COPD patient's most tolerated level cannot lead to further reduction in respiratory muscle load and RMS, but more asynchrony events. Physiological data can monitor the patient's responses and the ventilator-patient interaction, which may provide objective criterion to ventilator setting.
authors.affiliation: a State Key Laboratory of Respiratory Disease, Guangzhou Medical University , Guangzhou , China.|b The First Affiliated Hospital of Guangzhou Medical College , Guangdong , China.
authors.forename: Jianheng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: a State Key Laboratory of Respiratory Disease, Guangzhou Medical University , Guangzhou , China.|b The First Affiliated Hospital of Guangzhou Medical College , Guangdong , China.
authors.forename: Qun
authors.initials: Q
authors.lastname: Luo
authors.affiliation: a State Key Laboratory of Respiratory Disease, Guangzhou Medical University , Guangzhou , China.|b The First Affiliated Hospital of Guangzhou Medical College , Guangdong , China.
authors.forename: Huijin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: a State Key Laboratory of Respiratory Disease, Guangzhou Medical University , Guangzhou , China.|b The First Affiliated Hospital of Guangzhou Medical College , Guangdong , China.
authors.forename: Rongchang
authors.initials: R
authors.lastname: Chen
mesh_terms: D000368:Aged; D018450:Disease Progression; D006801:Humans; D006935:Hypercapnia / Q000209:etiology; D001239:Inhalation / Q000502:physiology; D008875:Middle Aged; D063087:Noninvasive Ventilation / Q000379:methods*; D011312:Pressure; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000503:physiopathology* / Q000628:therapy*; D012132:Respiratory Muscles / Q000503:physiopathology; D056152:Respiratory Rate; D013990:Tidal Volume
keywords: inspiratory positive airway pressure; neural respiratory drive; neuro-ventilatory coupling; patient-ventilator interaction; respiratory failure; respiratory muscles load