| Part I Effects of High-Flow Oxygen through Nasal Cannula on the patients with moderate to severe type I respiratory failureBACKGROUND:Compared with standard oxygen therapy,High-flow oxygen through nasal cannula(HFNC)has the advantages of positive end expiratory pressure(PEEP)effects and increase the end expiratory volume in patients with acute respiratory failure.Compared with Non-invasive ventilation(NIV),it has the advantages of sufficient humidification and improvement of comfort,so as to increase the tolerance of patients to HFNC.The recent subgroup analysis of a multicenter randomized controlled study found that,compared with standard oxygen therapy and NIV,HFNC can reduce the intubation rate at day 28 and mortality at day 90 in patients who had acute hypoxemic respiratory failure and a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen of 200 mmHg or less,but the results need prospective study to prove.Therefore,this study was designed to compare the effects of HFNC and NIV on intubation rate at day 28 in patients with moderate to severe type Ⅰ respiratory failure.OBJECTIVE:To confirm the effects of HFNC on intubation rate at day 28 in patients with moderate to severe type Ⅰ hypoxic respiratory failure.METHODS:A multi-central randomized controlled,prospective trial in 7 ICUs in Jiangsu Province was performed,and the patients who had moderate to severe type I respiratory failure and a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen of 200 mmHg or less were recruited and randomized into HFNC or NIV therapy.In the HFNC group,oxygen was delivered through a heated humidifier and applied continuously through large-bore bi-nasal prongs,with a gas flow rate of 50 liters per minute and a FiO2 of 1.0 at initiation.The fraction of oxygen in the gas flowing in the system and flow was subsequently adjusted to maintain a SpO2 of 92%or more.HFNC was applied for at least 2 days;In the NIV group,the pressure-support level was adjusted with the aim of obtaining an expired tidal volume of 7 to 10 ml per kilogram of predicted body weight,with an initial PEEP between 2 and 10 cmH2O.The FiO2 or PEEP level(or both)were then adjusted to maintain SpO2 of 92%or more.The minimally required duration of noninvasive ventilation was 8 hours per day for at least 2 days.Between NIV sessions,patients received high-flow oxygen,as described above.The data were recorded at inclusion:(1)characteristics of the patients’ main demographics and clinical data(name,age,gender,height,weight,diagnosis,check in time,APACHE Ⅱ score etiology and so on).(2)Arterial blood gas analysis(pH,PaCO2,PaO2,PaO2/FiO2)at 6-hour,24-hour,and 48-hour respectively;(3)Respiratory comfort score and respiratory distress score at 6-hour,24-hour,and 48-hour,respectively;(4)Heart rate(HR)and mean arterial pressure(MAP)at 6-hour,24-hour,and 48-hour respectively.(5)The rate of intubation at day 28,all cause mortality at 28 days,the duration of ICU stay.During the course of observation,such as respiratory failure aggravated,hemodynamic instability,consciousness changed(GCS<12 points),endotracheal intubation and mechanical ventilation were needed.RESULTS:(1)From February 2016 through March 2017,a total of 123 patients were recruited and after the secondary exclusion of 2 patients who withdrew consent,121 patients were included in the analysis.A total of 63 patients were assigned to high-flow oxygen therapy,and 58 to noninvasive ventilation.Compared with Group NIV,the characteristics of the patients at enrollment were similar:Age(56±14 vs.60±13,p=0.12),APACHE score(19±8 vs.17±5,p=0.06),pHa(7.42±0.07 vs.7.41±0.08,p=0.61),PaO2(101±38mmHg vs.99±37mmHg,p=0.72),PaO2/FiO2(126±36mmHg vs.133±46mmHg,p=0.41)PaCO2(33±6mmHg vs.35±8mmHg,p=0.29);respiratory comfort score(2±1 vs.2± 1,p=0.61),respiratory distress score(6±2 vs.5±2,p=0.17),HR(110 ± 22bpm vs.105±17 bpm,p=0.16),MAP(92± 14mmHg vs.88± 14 mmHg,p=0.10).(2)The intubation rate was 23.8%(15 of 63 patients)in the HFNC group,48.3%(28 of 58)in the NIV group(p=0.04).Compared with NIV group,HFNC did not improve the 28-day mortality(25.9%vs.30.2%,p=0.79)and the duration of ICU stay(9±7 vs.10±7,p=0.19).(3)Effects on oxygenation:compared with NIV group,after enrollment for six hours pHa(7.42±0.09 vs.7.42±0.08,p=0.49),PaCO2(33.0±6.0mmHg vs.35.2±8.0 mmHg,p=0.39),PaO2(107±39mmHg vs,97±31mmHg,p=0.26),PaO2/FiO2(213±67mmHg vs.192±68mmHg,p=0.42)and 24 hours’ oxygenation:pHa(7.41±0.08 vs.7.41±0.08,p=0.62),PaCO2(34.6± 10.0mmHg vs.37.0±9.2mmHg,p=0.19),PaO2(99±37mmHg vs.91±31mmHg,p=0.32),PaO2/FiO2(221 ±93mmHg vs.210 ±70mmHg,p=0.07)had no significant difference.But after enrollment for 48 hours,PaO2(96±27mmHg vs.114±48mmHg,p=0.03),PaO2/FiO2(211±63mmHg vs.221 ±82mmHg,p=0.02)significantly improved,but pHa(7.42±0.09 vs.7.43±0.09,p=0.43),PaCO2(38.2±6.0mmHg vs.38.9±8.2mmHg,p=0.34)has no significant difference.(4)Effects on respiratory comfort:Respiratory comfort score at 6-hour(3 ± 1vs.4±1,p<0.01 =,24-hour(3 ± 1 vs.4± 1,P<0.01 =,48-hour(3±2 vs.4±2,p<0.01 = were significantly improved in HFNC group.(5)Effects on respiratory distress score:compared with NIV group,after enrollment for six hours,there was no statistical difference in respiratory distress score(6 ±4 vs.7 ±4,p=0.42)in the two groups.But HFNC could improve respiratory distress score at 24-hour(5±2 vs.4±3,p<0.01=and 48-hour(5 ±3 vs.4 ±2,p=0.04).(6)Effects on hemodynamics:compared with NIV group,there is no statistical difference in HR(101±21 bpm vs.96±23 bpm,p=0.16),MAP(89± 14mmHg vs.93± 12mmHg,p=0.14)at 6-hour,HR(95±15 bpm vs.94± 16 bpm,p=0.65)and MAP(92± 13mmHg vs.93±9mmHg,p=0.86)at 24-our,HR(95±15bpm vs.94± 16bpm,p=0.65)and MAP(92± 12mmHg vs.94±9mmHg,p=0.59)at 48-hour.Conclusions:In patients with moderate to severe type Ⅰ respiratory failure,compared with noninvasive ventilation,HFNC can reduce the intubation rate at 28 day and improve comfort,relieve respiratory distress.Part Ⅱ Physiologic effects of High-Flow Oxygen through Nasal Cannula in moderate to severe type Ⅰ respiratory failureBACKGROUND:High-flow oxygen through nasal cannula(HFNC)could improve oxygenation,reduce intubation rate at 28 days and mortality at 90 days in comparison with conventional oxygen therapy.However,the physiologic effects potentially underlying these clinical benefits of HFNC are still largely undefined.The purpose of this study is to monitor the gas exchange,intrapulmonary gas distribution,respiratory mechanics during HFNC treatment in patients with moderate to severe type I respiratory failure.OBJECTIVE:To observe the physiologic effects of HFNC on respiratory mechanics and intrapulmonary gas distribution in patients with moderate to severe type I respiratory failure during the treatment.METHODS:This was a single center,prospective,self-controlled study in non-intubated moderate to severe type I respiratory failure patients with PaO2/FiO2≤200mmHg admitted to the Department of critical care medicine,Zhongda Hospital Affiliated to Southeast University from August 2016 to September 2016.The data were recorded at inclusion:(1)Characteristics of the patients’ main demographics and clinical data(name,age,gender,height,weight,diagnosis,check in time,APACHE II score,etiology and so on).(2)To assess the effects of HFNC 30min and HFNC 60min on pulmonary gas exchange by blood gas analysis.(3)To monitor global inhomogeneity(GI)index and region of interest(ROI)by electrical impedance tomography(EIT)to evaluate the intrapulmonary gas distribution in FHFNC 30min and HFNC 60min;(4)To monitor the changes of esophageal pressure,airway pressure by the respiratory mechanics monitor to evaluate pulmonary respiratory mechanics in HFNC 30min and HFNC 60min;(5)To record the HR,SBP,DBP,MAP to assess hemodynamics changes in HFNC 30min and HFNC 60min.RESULTS:(1)14 patients with moderate to severe type I respiratory failure admitted to the general Intensive Care Unit of Zhongda Hospital were involved.In the course of the study,3 patients were excluded,because of intubation.(2)Effect of HFNC on gas exchange:compared with the basic status,after treatment of HFNC for 30min,there was no significant changes in pHa(7.45 ±0.05 vs.7.44±0.04,p=0.37),PaCO2(32.0±5.2mmHg vs.33.6±6.0mmHg,p=0.43),but PaO2(74.6±13.9mmHgvs.102.7±33.7mmHg,p=0.02)and PaO2/FiO2(149.7±31.2mmHg vs.187.5±58.7mmHg,p=0.03)were significantly improved;Compared with the basic status,after treatment of HFNC for 60 mins,there was no significant change in pHa(7.45 ±0.05 vs.7.45 ±0.05,p=0.23),PaCO2(32.0±5.2mmHg vs.32.4 ± 6.2mmHg,p=0.43),but PaO2(74.6±13.9mmHg vs.106.4±36.0mmHg,p=0.03)and PaO2/FiO2(149.7 ±31.2mmHg vs.174.3 ±51.1mmHg,p=0.04)were significantly improved;Compared with HFNC 30min,after treatment of HFNC for 60min,there is no significantly changes in pHa(7.44±0.04 vs.7.45±0.05,p=0.12),PaCO2(33.6±6.03mmHg vs.2.4±6.2mmHg,p=0.63),Pa02(102.7±33.7mmHg vs.106.4±36.0mmHg,p=0.23),Pa02/Fi02(187.5±58.7mmHg vs.174.3 ±51.1mmHg,p=0.29).(3)Effect of HFNC on intrapulmonary gas distribution:compared with the basic status,after treatment of HFNC for 30min,there was no improvement in ventilation in ROI1(0.06±0.1 lvs.0.02 ± 0.05,p=0.22),ROI2(0.15 ± 0.20 vs.0.12 ± 0.16,p=0.31),ROI4(0.08 ± 0.08 vs.0.07 ± 0.05,p=0.13),but GI index(0.73±0.20 vs.0.87±0.23,p=0.01)and ROI3(0.14±0.06 vs.0.15±0.03,p=0.02)were improved.The results showed that there was no excessive expansion of the alveoli in the non-dependent area,and the dependence area of ROI3 was improved.Compared with the basic status,after treatment of HFNC for 60min,there was no improvement in ventilation in ROI1(0.06±0.11 vs.0.02±0.06,p=0.87),ROI2(0.15±0.20 vs.0.12±0.18,p=0.72),ROI4(0.08±0.08 vs.0.10±0.07,p=0.11),but GI(0.73±0.20 vs.0.91±0.07,p<0.01)and R0I3(0.14±0.06vs.0.16±0.05,p=0.02)were improved.Indicated tht lung heterogeneity improved,ventilation of dependent area of ROI3 improved,and the non-dependent area of ROI1 and ROI2 had no statistical changes,it means there is no hyperinflation in non-dependent areas.Compared with HFNC 30min,after treatment of HFNC for 60min,no improvement in ventilation in ROI1(0.02 ±0.05 vs.0.02±0.06,p=0.92),ROI2(0.12±0.16 vs.0.12±0.18,p=0.93),ROI3(0.15±0.03 vs.0.16 ± 0.05,p=0.44),but GI index(0.87 ± 0.23 vs.0.91 ± 0.07,p=0.01)and ROI4(0.07±0.05 vs.0.10 ± 0.07,p=0.02)improved.The resultes shows that with the prolong of HFNC time,it can improve the pulmonary ventilation homogeneity,mainly to improve the lung ventilation in the ROI4 area of gravity dependent area,but there is no obvious improvement in ROI1 area,ROI2 area and ROI3 area.(4)Effects of HFNC on respiratory mechanics:compared with the basic status,after treatment of HFNC for 30min,PL,ei(11.43±3.18cmH2O vs.10.87±2.17cmH2O,p<0.01),△PL(12.94±3.52cmH2O vs.4.92±2.85cmH2O,p<0.01)decreased significantly.But PL,ee(-1.52±2.70cmH2O vs.5.94±2.14cmH2O,p<0.01)increase.Compared with the basic status,after treatment of HFNC for 60min,PL,ei(11.43±3.18cmH2O vs.11.05±2.26cmH2O,p<0.01),△PL(12.94±3.52cmH2O vs.7.64±3.36cmH2O,p<0.01)decreased significantly.But PL,ee(-1.52±2.70cmH2O vs.3.41 ±3.57cmH2O,p<0.01)increase.Compared with HFNC 30min,after treatment of HFNC for 60min,PL,ei(10.87±2.17cmH20 vs.11.05±2.26cmH2O,p=0.29),PL,ee(5.94±2.14cmH20 vs.3.41±3.57cmH2O,p=0.61),△PL(4.92±2.95cmH2O vs.7.64±3.36cmH2O,p=0.51)did not change significantly.(5)Effects of HFNC on hemodynamics:there was no significant change in HR,SBP,DBP,MAP between 3 time points(p>0.05).Conclusions:In patients with moderate to severe type I respiratory failure,HFNC can reduce the inspiratory transpulmonary pressure and the pulmonary driving pressure,increase end-expiratory pressure,improve intrapulmonary gas distribution. |
