Objective To compare the effects of oxygen therapy and local pressurization in alleviating plateau hypoxia at high altitude. Methods Forty-five healthy male soldiers were investigated at an altitude of 3992 meters. The subjects were randomly divided into three groups, ie. an oxygen inhalation group, a single-soldier oxygen increasing respirator ( SOIR) group and a BiPAP group. The oxygen inhalation group was treated with oxygen inhalation via nasal catheter at 2 L/ min. SOIR was used to assist breath in the SOIR group. The BiPAP group were treated with bi-level positive airway pressure ventilation, with IPAP of 10 cm H2O and EPAP of 4 cmH2 O. PaO2, PaCO2, SpO2 and heart rate were measured before and 30 minutes after the treatment. Results There were continuous increase of PaO2 from ( 53. 30 ±4. 88) mm Hg to( 58. 58 ±5. 05) mm Hg and ( 54. 43 ±3. 01) mm Hg to ( 91. 36 ±10. 99) mm Hg after BiPAP ventilation and oxygen inhalation, respectively ( both P lt; 0. 01) . However, the PaO2 of the SOIR group was decreased from( 56. 00 ±5. 75) mm Hg to ( 50. 82 ±5. 40) mm Hg( P lt; 0. 05 ) . In the other hand, the PaCO2 was increased from ( 30. 41 ±1. 51) mmHg to ( 32. 56 ±2. 98) mm Hg in the oxygen inhalation group ( P lt; 0. 05) , declined from( 28. 74 ±2. 91) mm Hg to ( 25. 82 ±4. 35) mm Hg in the BiPAP group( P lt;0. 05) ,and didn’t change significantly from( 28. 65 ±2. 78) mm Hg to ( 29. 75 ±3. 89) mmHg in the SOIR group ( P gt;0. 05) . Conclusions Both BiPAP ventilation and oxygen inhalation can alleviate plateau hypoxia by improving PaO2 at 3992 meter altitude while SOIR has no significant effect.
Objective To investigate the effects of noninvasive ventilation for the treatment of acute respiratory failure secondary to severe acute respiratory syndrome ( SARS) . Methods 127 patients with complete information were collected from the database of SARS in Guangdong province, who were all consistent with the ALI/ARDS diagnostic criteria. The patients were divided into three groups depending on ventilation status, ie. a no-ventilation group, a noninvasive ventilation group, and a mechanical ventilation group. The outcome of ventilation treatmentwas followed up.Multi-factor regression analysis was conducted to analyze the relations of ventilation treatment with ARDS and mortality, and factors associated with success of noninvasive ventilation. Results As soon as the patients met the diagnostic criteria of ALI/ARDS, the patients in the noninvasive ventilation group were in more serious condition and had a higher proportion of ARDS compared with the no-ventilation group ( P lt;0. 01) . The patients in the mechanical ventilation group had a higher mortality rate ( P lt;0.01) . 6 and 7 patients in the no-ventilation group had noninvasive ventilation and invasive ventilation thereafter, respectively. 15 patients in the noninvasive group switched to invasive ventilation. Compared with the patients without ventilation ( n =45) , the patients receiving noninvasive ventilation ( n = 61) were in more serious condition and at higher risk of developing ARDS ( P lt;0. 01) , but the mortality was not different between them ( P gt; 0. 05) . The patients who continued to receive noninvasive ventilation ( n = 40) were in more serious condition, and at higher risk of developing ARDS compared with the patients without ventilation ( n = 45) ( P lt; 0. 01) . 15 patients in the noninvasive group who switched to invasive ventilation were older than those patients continuing noninvasive ventilation.Conclusions For SARS patients fulfilling the ALI/ARDS criteria, the patients underwent noninvasive ventilation are more severe, run a higher probability of developing ARDS from ALI. But earlier initiation of noninvasive ventilation has no impact on mortality. The patients who tolerate noninvasive ventilation can avoid intubation, especially for young patients. However, the time and indication of shifting from noninvasive ventilation to invasive ventilation should be emphasized.
Objective To investigate the influence of pulmonary infection on noninvasive ventilation ( NIV) therapy in hypercapnic acute respiratory failure ( ARF) due to acute exacerbation of chronic obstructive pulmonary disease ( AECOPD) , and evaluate the predictive value of simplified version of clinical pulmonary infection score ( CPIS) for the efficacy of NIV therapy in ARF patients with AECOPD. Methods Eighty-four patients with ARF due to AECOPD were treated by NIV, and were divided into a successful group and an unsuccessful group by the therapeutic effect of NIV. The CPIS and simplified version of CPIS between two groups was compared. The predictive value of simplified version of CPIS for the efficacy of NIV wasevaluated using ROC curve analysis. Results The CPIS and the simplified version of CPIS of the successful treatment group ( 4. 0 ±2. 8, 3. 2 ±2. 4) were lower than those of the unsuccessful group ( 8. 0 ±2. 1, 7. 2 ±1. 8) significantly ( P =0. 006, 0. 007) . The area under ROC curve ( AUC) of CPIS and simplified version of CPIS were 0. 884 and 0. 914 respectively, the cut oint of CPIS and simplified version of CPIS were 6 ( sensitivity of 78. 0% , specificity of 91. 2% ) and 5 ( sensitivity of 80. 0% , specificity of 91. 2% ) respectively. Conclusions The level of pulmonary infection is an important influencing factor on the therapeutic effect of NIV in patients with ARF due to AECOPD. Simplified version of CPIS is a helpful predictor for the effect of NIV on ARF of AECOPD.
ObjectiveTo investigate the effect of noninvasive ventilation (NIV) in patients with myasthenic crisis after thymectomy. Methods31 myasthenic crisis patients after thymectomy who initially used NIV,admitted in the First Affiliated Hospital of Guangzhou Medical University between January 2011 and June 2013,were analyzed retrospectively.They were assigned to two groups according to the successful application of NIV or not,with 13 patients in the NIV success group and 18 patients in the NIV failure group.The related factors including gender,age,APACHEⅡ score when admitted to ICU,the results of blood gas analysis before NIV,thymoma or not,the history of myasthenic crisis,the history of chronic lung disease,and minute ventilation accounted for the largest percentage of predicted value (MVV%pred)were analyzed. ResultsThere were no significant differences in age,gender,or APACHEⅡ score between two groups (P>0.05).The PaCO2 in the NIV success group was lower than that in the NIV failure group.The preoperative MVV%pred in the NIV success group was higher than that in the NIV failure group.There were no significant differences between two groups in pH,PO2,thymoma or not,the history of myasthenic crisis,or the history of chronic lung disease (P>0.05).If using the 45 mm Hg as the cut-off value of PaCO2 and 60% as the cut-off value of MVV%pred,the incidence of PaCO2<45 mm Hg and the incidence of MVV%pred>60% were higher in the NIV success group than those in the NIV failure group (84.6% vs.33.3%, P<0.05;100% vs. 55.6%,P<0.05).Logistic regression analysis revealed that PaCO2<45 mm Hg was an independent influence factor for successful application of NIV in patients with myasthenic crisis after thymectomy. ConclusionPaCO2<45 mm Hg can be a predictor of successful application of NIV in patients with myasthenic crisis after thymectomy.For the patients underwent NIV whose PaCO2<45 mm Hg or MVV%pred<60%,the clinician should predict the possibility of failure and prepared for intubation.
Objective To investigate the safety of high fraction of inspired oxygen (FiO2)during noninvasive ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD)and carbon dioxide (CO2)retention. Methods Fifty-six AECOPD patients with CO2 retention admitted between March 2013 and August 2015 were recruited in the study.All patients received noninvasive ventilation treatment with FiO2<0.5.After stabilization of acute respiratory crisis,FiO2 was increased to 1.0 and lasted for 40 minutes.The changes of tidal volume,respiratory frequency,minute volume,Glasgow coma score,arterial blood gas and SpO2 were observed before and after the FiO2 reset. Results The mean PaO2 increased from (83±14)mm Hg to (165±41)mm Hg and the mean SpO2 increased from (92.4±3.1)% to (97.8±1.9)% significantly (both P<0.001).The mean PaCO2 did not changed obviously from (72±15)mm Hg to (72±14)mm Hg (P=0.438).There were also no significant changes in any of the other parameters. Conclusion During noninvasive ventilation with an FiO2 sufficient to maintain a normal PaO2,an increase in FiO2 does not further increase PaCO2 level in AECOPD patients with CO2 retention.
Objective This is a meta-analysis of the efficacy of noninvasive ventilation (NIV) with helmet compared to NIV with face mask in patients with acute respiratory failure (ARF). Methods " Helmet, face mask or facial mask” and " mechanical ventilation or noninvasive ventilation” were used as key words both in Chinese and English to search all the trials in PubMed, OVID, Embase, Scopus and Cochrane Library, websites, reference lists of articles, CNKI and Wanfang Database from inception to December 2016. Two reviewers independently assessed the methodological quality of the trials and extracted information. Revman 5.3 was used for data analysis. Results Ten randomized controlled trials (RCTs) and six case-control trials were included. NIV with a helmet reduced the intubation rate (OR=0.35, 95%CI 0.24 to 0.51, P<0.000 01), in-hospital mortality rate (OR=0.51, 95%CI 0.34 to 0.76, P=0.001), and NIV-related complications (OR=0.10, 95%CI 0.06 to 0.15, P<0.000 01) compared to NIV with face mask. There was no significant difference in gas exchange between two groups. In the subgroup analysis, types of ARF and ventilation mode did not affect the intubation rate and the complications relevant to NIV, but NIV with helmet mainly decreased the in-hospital mortality of the patients with hypoxemic ARF or pressure support ventilation. Conclusions NIV with a helmet can decrease the endotracheal intubation rate, in-hospital mortality, and NIV-related complications of the patients with ARF. And helmet is as effective as face mask in improving the gas exchange. However, larger or multicenter RCTs are needed to analyze the role of NIV with a helmet in this condition.
ObjectiveTo investigate the application value of noninvasive ventilation (NIV) performed in patients with unplanned extubation (UE) in intensive care unit (ICU).MethodsThis was a retrospective analysis. The clinical data, application of NIV, reintubation rate and prognosis of UE patients in the ICU of this hospital from January 2014 to December 2018 were reviewed, and the patients were assigned to the control group or the NIV group according to the application of NIV after UE. The data between the two groups were compared and the application effects of NIV in UE patients were evaluated.ResultsA total of 66 UE patients were enrolled in this study, including 44 males and 22 females and with an average age of (64.2±16.1) years. Out of them, 41 patients (62.1%) used nasal catheter or mask for oxygenation as the control group, 25 patients (37.9%) used NIV as the NIV group. The Acute Physiology andChronic Health EvaluationⅡ score of the control group and the NIV group were (18.6±7.7) vs. (14.8±6.3), P=0.043. The causes of respiratory failure in the control group and the NIV group were as follows: pneumonia 16 patients (39.0%) vs. 7 patients (28.0%), postoperative respiratory failure 7 patients (17.1%) vs. 8 patients (32.0%), chronic obstructive pulmonary disease 8 patients (19.5%) vs. 6 patients (24.0%), others 5 patients (12.2%) vs. 4 patients (16.0%), heart failure 3 patients (7.3%) vs. 0 patients (0%), nervous system diseases 2 (4.9%) vs. 0 patients (0%), which showed no significant difference between the two groups. Mechanical ventilation time before UE were (12.5±19.8) vs (12.7±15.2) d (P=0.966), PaO2 of the control group and the NIV group before UE was (114.9±37.4) vs. (114.4±46.3)mm Hg (P=0.964), and oxygenation index was (267.1±82.0) vs. (257.4±80.0)mm Hg (P=0.614). Reintubation rate was 65.9% in the control group and 24.0% in the NIV group (P=0.001). The duration of mechanical ventilation was (23.9±26.0) vs. (21.8±26.0)d (P=0.754), the length of stay in ICU was (34.4±36.6) vs. (28.5±25.8)d (P=0.48). The total mortality rate in this study was 19.7%. The mortality rate in the control group and NIV group were 22.0% and 16.0% (P=0.555).ConclusionPatients with UE in ICU may consider using NIV to avoid reintubation.
ObjectiveTo evaluate the accuracy of the new dynamic approach in the measurement of respiratory mechanics with different pressure support (PS) level during pressure support ventilation (PSV) via oral-nasal mask.MethodsThe Respironics V60 ventilator was connected to a ASL5000 lung simulator, which simulate lung mechanics in patients with chronic obstructive pulmonary disease ［system compliance (Crs)=50 mL/cm H2O, airway resistance (Raw)=20 cm H2O/(L·s), inspiratory time (TI)=1.6 s, breathing rate=15 beats per minute］. PSV were applied with different levels of PS ［positive end-expiratory pressure=5 cm H2O, PS=5/10/15/20/25 cm H2O) and back-up rate=10 beats per minute］. Measurements were conducted at system leaks with 25 – 28 L/min. The performance characteristics and patient-ventilator asynchrony were assessed, including flow, airway pressure, time and workload. Crs and Raw were calculated by using new dynamic approach.ResultsTidal volume (VT) was increased with increasing PS level ［(281.45±4.26)mL at PS 5 cm H2O vs. (456.81±1.91)mL at PS 10 cm H2O vs. (747.45±3.22)mL at PS 20 cm H2O, P<0.01］. Severe asynchronous was occurred frequently when PS is at 25 cm H2O. Inspiration cycling criterion (CC) was up-regulated accompanied by increasing PS level ［(15.62±3.11)% at 5 cm H2O, vs. (24.50±0.77)% at 20 cm H2O, P<0.01］. Premature cycling was always existed during PSV when PS < 20 cm H2O, which could be eliminated as PS level increasing. Delay cycling was found when PS was at 20 cm H2O, and cycling delay time was (33.60±15.91)ms (P<0.01). The measurement of Crs was (46.19±1.57)mL/cm H2O with PS at 10 cm H2O, which was closer to the preset values of simulated lung. The underestimate of Crs was observed during high level PS support. The calculation of inspiratory and expiratory resistance was approximate to 20 cm H2O/(L·s) when PS level was exceeded 15 cm H2O.ConclusionsThe new dynamic approach can continuously assess the respiratory mechanics during non-invasive ventilation, which is no need to interrupt the patient's spontaneous breathing. Higher inspiratory flow during PSV is beneficial for Raw measurement, whereas the accuracy of Crs was influenced by the value of actual VT.
ObjectiveTo investigate whether noninvasive positive pressure ventilation (NIV) will improve preoxygenation in critically ill patients in intensive care unit (ICU) before intubation, when compared with bag-valve-mask (BVM).MethodsThis was a single-centered, prospective and randomized study. The patients in the study were those who required tracheal intubation in the ICU of the First Affiliated Hospital of Guangzhou Medical University and Guangzhou Institute of Respiratory Health from June 2015 to June 2017. These critically ill patients were provided with BVM or NIV assisted preoxygenation randomly. The data of the NIV group and the control group were compared and the application values of NIV in preoxygenation of critically ill patients were evaluated.ResultsA total of 106 patients participated in this study, including 75 males and 31 females and with an average age of (65.0±12.6) years. The patients were classified either into the control group (BVM assisted preoxygenation, n=53), or the NIV group (NIV assisted pre-oxygenation, n=53). The causes of intubation in the control group and the NIV group were as follows: pneumonia [40 patients (75.5%) vs. 39 patients (73.6%)], chronic obstructive pulmonary disease [12 patients (22.6%) vs. 11 patients (20.8%)], and other disease [1 patient (1.9%) vs. 3 patients (5.7%)], which showed no significant difference between the two groups. The scores of the Acute Physiology and Chronic Health Evaluation System Ⅱ of the control group and the NIV group were 20 (17, 26) vs. 20 (16, 26), P=0.86, which also showed no significant difference. The oxygen saturation of the pulse (SpO2) before preoxygenation were similar in both the control group and the NIV group 92% (85%, 98%) vs. 91% (85%, 98%), P=0.87. After preoxygenation, SpO2 was significantly higher in the NIV group than in the control group 99% (96%, 100%) vs. 96% (90%, 99%), P=0.001. For the subgroup of patients with SpO2 less than 90% before preoxygenation, the respective SpO2 in the control group and the NIV group were 83% (73%, 85%) vs. 81% (75%, 86%), P=0.75; after preoxygenation, SpO2 in the NIV group was significantly higher than in the control group 99% (96%, 100%) vs. 94%(90%, 99%), P=0.000. For the subgroup of patients with SpO2 of 90% or more before preoxygenation, the respective SpO2 in the control group and the NIV group were similar 95.5% (92%, 99%) vs. 96% (94%, 99%), P=0.52; and continued to be similar after preoxygenation 98% (95%, 100%) vs. 99% (96%, 100%), P=0.1. The duration of mechanical ventilation of the control group and the NIV group was 17 (10, 23)d vs. 19 (11, 26)d (P=0.86). The 28 days survival rate of the control group and the NIV group was 73.6% vs. 71.7% (P=0.34). The mortality rate in the control group and NIV group were 31.3% and 31.7% (P=0.66).ConclusionsWhen compared with the use of BVM, NIV assisted preoxygenation is effective and safe for critically ill patients. Critically ill patients with severe hypoxemia will benefit more from NIV assisted preoxygenation.
Objective To evaluate the influence on the estimation of respiratory mechanics with dynamic signal analysis approach during noninvasive positive pressure ventilation (NPPV) under different inspiratory effort conditions. Methods The Respironics V60 ventilator was connected to a ASL5000 lung simulator, which simulate lung mechanics in healthy adults with body weight from 65 to 70 kg, and patients with chronic obstructive pulmonary disease (COPD) and acute respiratory distress (ARDS). Each lung models was subjected to 4 different muscle pressures (Pmus): 0, 5.0, 10.0, and 15.0 cm H2O. Inspiratory pressure support level was adjusted to maintain tidal volume (VT) achieving 7.0 mL/kg outputted by ventilator respectively. Positive end expiratory pressure was set at 5.0 cm H2O and back-up rate was 10 beats per minute. Measurements were conducted at system leaks with 25 to 28 L/min. The respiratory system compliance (Crs), inspiratory and expiratory resistance (Rinsp and Rexp) were estimated by special equations, which was derived from the exhaled VT, flow rate and airway pressure. Results The driving pressure (DP) was decreased with Pmus increasing, and was 1.0 cm H2O after Pmus exceeding 10.0 cm H2O and the VT was larger than 7.0 mL/kg in normal adult model. The estimated value of Crs was affected by the changes of Pmus in all three lung models. The significant underestimation of Raw and the overestimation of Crs were observed when Pmus level exceed 10.0 cm H2O. The measured errors of Crs and Rexp were within 10% in COPD and ARDS model when Pmus was at 5.0 cm H2O. The underestimation of Rinsp was always existed in all Pmus level (P<0.01). Conclusions Using dynamic signal analysis approach, the real-time estimation of respiratory mechanics (Crs and Raw) is no need to interrupt the spontaneous breathing during NPPV. Excessive effort will increase the patient’s inspiratory workload, which is not benefit to accurate estimation of respiratory mechanics.