General characteristics of the study participants (mean±SD).

<p>*: chi-square value, the others in the colume all represents t values; BMI: body mass index; FEV₁: forced expiratory volume for 1 second; MNI: multiparameter nutritional index; PA: physical activity.</p

Multiparameter nutritional index for all subjects.

<p>IBW: ideal body weight; TSF: triceps skinfold thickness; MAMC: mid-arm muscle circumference; %pred: percentage of predicted.</p

Quadriceps endurance time test: the lines on the top channel represent the sustained isometric contraction at 60% value of quadriceps maximal volitional contraction (QMVC); surface electromyography (SEMG) from vastus lateralis muscle (VL-M), rectus femoris muscle (RF-M) and vastus medialis muscle (VM-M) were shown below the force line; the number below the X axis was the time (minutes: seconds).

<p>The time to fatigue (QTf) in this figure was about 2 minutes and 20 seconds (140 seconds).</p

Quadriceps function and RMS of the SEMG during QMVC test (mean±<i>SD</i>).

<p>QMVC: quadriceps maximal volitional contraction; QTf: quadriceps time to fatigue; VL: vastus lateralis; RF-M: rectus femoris; VM: vastus medialis; RMS: root mean squares; RF: rectus femoris; RMS: root mean squares; SEMG: surface electromyography;</p

The functional test of quadriceps.

<p>The functional test of quadriceps.</p

Simultaneous force and surface electromyography (SEMG) recordings during quadriceps maximal volitional contraction (QMVC) tests: the lines on the top channel represent the 3 consecutive volitional contraction forces; SEMG signals from vastus lateralis muscle (VL-M), rectus femoris muscle (RF-M) and vastus medialis muscle (VM-M) were shown in channel 2, 3 and 4, respectively; the number below the X axis represents the time (minute: second).

<p>QMVC was about 25(<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084167#pone-0084167-g002" target="_blank">Figure 2A</a>) 40 kg in a male normal subject (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084167#pone-0084167-g002" target="_blank">Figure 2B</a>).</p

Factors correlated with QMVC and QTf in COPD patients.

<p>*: P<0.05;</p><p>**: P<0.01; CTG: skinfold corrected thigh girth; FEV1: forced expiratory volume for 1 second; MNI: multiparameter nutritional index; PA: physical activity; QMVC: quadriceps maximal volitional contraction; QTf: quadriceps time to fatigue; TNF-α: tumor necrosis factor alpha.</p

Coefficients for each predictor for QMVC obtained from multiple regression analysis.

<p>FEV1: forced expiratory volume for 1 second; MNI: multiparameter nutritional index; PA: physical activity; QMVC: quadriceps maximal volitional contraction.</p

High-flow nasal cannula <i>versus</i> conventional oxygen therapy in patients with dyspnea and hypoxemia before hospitalization

Introduction: Patients with dyspnea and hypoxemia are common in emergency departments. However, it is unknown whether high-flow nasal cannula (HFNC) reduces the risk of requiring more advanced ventilation support and whether HFNC relieves dyspnea better than conventional oxygen therapy (COT). Areas covered: We searched the PubMed, Cochrane Library, Ovid, and Embase databases from inception to 1 September 2019 to identify relevant-randomized controlled trials comparing the effect of HFNC with COT in emergency departments regarding the severity of dyspnea, hospitalization rate, intubation rate, and hospital mortality. We identified four studies. HFNC was associated with a lower rate of requiring more advanced ventilation. HFNC reduced the rate of dyspnea, lowered the dyspnea scale score, and decreased patients’ respiratory rate significantly. However, there was insufficient evidence to show a significant effect on HFNC regarding patients’ oxygenation and hospital mortality. Expert opinion: For patients with dyspnea and hypoxemia before hospitalization, the short-term effect of HFNC was undeniable. HFNC reduced the risk of requiring more advanced ventilation and relived dyspnea better than COT. HFNC might be considered as a first-line therapy even before making a clear diagnosis for dyspnea. More studies are needed to explore the effect of HFNC on oxygenation and patients’ prognosis.</p

Physiological Significance of Well-tolerated Inspiratory Pressure to Chronic Obstructive Pulmonary Disease Patient with Hypercapnia During Noninvasive Pressure Support Ventilation

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 0.05).  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.</p