Fluctuating PEEP (F–PEEP) versus conventional PEEP in dogs with asymmetrical lung injury

Fluctuating PEEP (F-PEEP) is a newly developed PEEP in which end-expiratory pressure (EEP) is periodically changed within a certain range. In a dog model with unilateral lung injury induced by the introduction of hydrochloric acid, F-PEEP in which the EEP was periodically changed from 0.5 to 1.5 kPa at periods of 6 min, and conventional PEEP (C-PEEP) with an optimized EEP of 1.0 kPa, were each applied for 30 min. F-PEEP produced a significantly greater improvement of PaO2 and intrapulmonary shunt (QS/QT) than C-PEEP, and at the low EEP phase, the greatest improvement accompanied by an increased dynamic compliance and a large cardiac output was obtained. These results suggest that F-PEEP provides a useful mode of artificial ventilation for the treatment of unilateral lung injury.     

Comparison between fluctuating PEEP and conventional PEEP in dogs with lung injury induced by blood aspiration

It has been documented that in some patients with acute hypoxic respiratory failure the application of positive end-expiratory pressure (PEEP) may produce no improvement or even a deterioration of pulmonary oxygenation due to an increase in ventilation-perfusion mismatching. Fluctuating PEEP (F-PEEP) is a newly developed PEEP in which end-expiratory pressure (EEP) is periodically changed within a certain range. In a dog model with localized lung injury induced by the aspiration of non-heparinized blood (2 ml.kg body weight-1), F-PEEP in which the EEP was periodically changed from 0.5 to 1.5 kPa at frequencies of 10 min, and conventional PEEP with 3 different fixed EEPs, 0.5, 1.0 and 1.5 kPa (C-PEEP0.5, C-PEEP1.0 and C-PEEP1.5) were each applied for 60 min. F-PEEP produced a periodical change in PaO2 and hemodynamic variables including cardiac output, and in comparison with C-PEEP0.5, C-PEEP1.0 and C-PEEP1.5, a significantly greater improvement of A-aDO2 and dynamic compliance with relatively large cardiac output in the low EEP phase. These results suggest that F-PEEP is a useful mode of artificial ventilation for treating some kinds of acute hypoxic respiratory failure due to increased ventilation-perfusion mismatching.     

Nasal CPAP reduces systemic blood pressure in patients with obstructive sleep apnoea and mild sleepiness

BACKGROUND: A randomised controlled study was undertaken to examine the effect of nasal continuous positive airway pressure (CPAP) on 24 hour systemic blood pressure (BP) in patients with obstructive sleep apnoea (OSA). METHODS: Patients were fitted with an ambulatory BP measuring device as outpatients during normal activities and recorded for 24 hours before starting therapeutic or subtherapeutic (4 cm H(2)O) CPAP treatment. BP monitoring was repeated before completion of 12 weeks of treatment. The primary end point was the change in 24 hour mean BP. RESULTS: Twenty three of 28 participants in each treatment arm completed the study. There was no significant difference between the two groups in age, body mass index, Epworth Sleepiness Score, apnoea-hypopnoea index, arousal index, and minimum Sao(2). Twenty four patients were hypertensive. The pressure in the therapeutic CPAP group was 10.7 (0.4) cm H(2)O. CPAP usage was 5.1 (0.4) and 2.6 (0.4) hours/night for the therapeutic and subtherapeutic CPAP groups, respectively (p<0.001). After 12 weeks of treatment there were significant differences between the two CPAP groups in mean (SE) changes in 24 hour diastolic BP (-2.4 (1.2) v 1.1 (1.0) mm Hg (95% CI -6.6 to -0.5), p = 0.025); 24 hour mean BP (-2.5 (1.3) v 1.3 (1.1) mm Hg (95% CI -7.2 to -0.2), p = 0.037); sleep time systolic BP (-4.1 (2.1) v 2.2 (1.8) mm Hg (95% CI -11.8 to -0.7), p = 0.028); and sleep time mean BP (-3.6 (1.7) v 1.3 (1.4) mm Hg (95% CI -9.2 to -0.4), p = 0.033). CONCLUSIONS: Compared with subtherapeutic CPAP, 12 weeks of treatment with therapeutic CPAP leads to reductions in 24 hour mean and diastolic BP by 3.8 mm Hg and 3.5 mm Hg, respectively, in mildly sleepy patients with OSA.     

Fluctuating PEEP versus conventional PEEP in diffuse and unilateral lung injury induced by oleic acid

Effects of fluctuating positive end-expiratory pressure (F-PEEP), in which end-expiratory pressure (EEP) was periodically changed from 0.5 to 1.5 kPa with a periodic time of 6 min, and conventional PEEP (C-PEEP) with a fixed EEP of 1.0 kPa, were comparatively studied in diffuse (Group I) and unilaterally dominant lung injury (Group II). Although F-PEEP produced cyclic alterations of PaO2 in both groups, PaO2 changed in proportion to EEP in Group I and in reciprocal proportion to EEP in Group II. There was no significant difference between PaO2 and QS/QT during F-PEEP and those during C-PEEP in Group I, whereas in Group II, F-PEEP produced a significantly greater improvement of pulmonary oxygenation at the low EEP phase than C-PEEP. In both groups, the degree of hemodynamic depression was proportional to EEP. These results suggest that F-PEEP should be indicated for acute hypoxic respiratory failure with uneven distribution of lung injury.     

Endotracheal tube versus face mask with and without continuous positive airway pressure (CPAP)

Various ways of delivering continuous positive airway pressure (CPAP) have been extensively studied, with little attention, however, being paid to the effects of an intubation tube compared with breathing through a face mask, with or without CPAP. Pulmonary and cardiovascular variables were measured while 12 patients recovering from coronary artery bypass grafting were spontaneously breathing at ambient airway pressure, then at 7.4 mmHg (1 kPa) CPAP, and again at ambient pressure just before extubation. The same stages were repeated immediately after extubation, with patients breathing through a tight-fitting face mask. Arterial oxygen tension (Pao₂, mean ± s.d.) was better when the patients were breathing at ambient pressure through a face mask (11.7±2.8 kPa) than when they were intubated (10.6±2.4 kPa, P < 0.05). Compared with ambient pressure, CPAP (7.4 mmHg) (1 kPa) increased Pao₂ in both modes (13.4 ± 3.5 kPa with mask, and 12.6 ± 3.5 kPa when intubated, n.s.). The best arterial oxygen saturation was measured during CPAP with a face mask (96± 1%). Cardiac output remained unchanged in all the breathing modes. After coronary artery bypass grafting, spontaneous breathing with a face mask resulted in better Pao₂ than breathing through an endotracheal tube, both with and without 7.4 mmHg (1 kPa) CPAP. This study indicates that unnecessary delay in extubation should be avoided.     

Sildenafil versus continuous positive airway pressure for erectile dysfunction in men with obstructive sleep apnea： a comparat-ive study of their efficacy and safety and the patient＇s satisfaction with treatment

Aim： To assess the efficacy of sildenafil and continuous positive airway pressure （CPAP） in the treatment of concurrent erectile dysfunction （ED） with obstructive sleep apnea （OSA）, and to gauge the level of treatment satisfaction in patients and their partners. Methods： Forty men were treated for 12 weeks with sildenafil 100 mg （20 men） or CPAP during nighttime sleep （20 men）. Treatment efficacy was assessed by the rate of successful intercourse attempts, and satisfaction with treatment was assessed by patients＇ and partners＇ answers to question 1 of the Erectile Dysfunction Inventory of Treatment Satisfaction. Results： Under sildenafil, 128 of 249 （51.4%） intercourse attempts were successful; under CPAP, 51 of 193 （26.9%） attempts were successful （^cp 〈 0.001）. Erectile function was improved in both groups. After sildenafil and CPAP treatment, the mean International Index for Erectile Function domain scores were 14.3 and 10.8, respectively （^bp = 0.025）, compared to 7.8 and 7 at baseline, respectively. CPAP and sildenafil were well tolerated. Sporadic episodes of nasal dryness under CPAP and transient headache and flushing under sildenafil were not significant. Fifty percent of patients treated with sildenafil and 25% with CPAP were satisfied with the treatment, and their partners were equally satisfied. The satisfaction scores for both patients and partners under sildenafil were superior to those under CPAP （^cP 〈 0.002）. Conclusion： Both sildenafil 100 mg and CPAP, used separately, had positive therapeutic impact but sildenafil was superior. Patients and their partners were more satisfied with sildenafil for the treatment of ED. However, because of the high proportion of dissatisfied men and partners, new therapeutic agents or a combination of the two methods must be studied further.     

Effect of continuous positive airway pressure (CPAP) in patients with chronic obstructive pulmonary chsease (COPD) depending on intrinsic PEEP levels

The application of continuous positive airway pressure (CPAP) is known to reduce inspiratory work of breathing in intubated patients with chronic obstructive pulmonary disease (COPD). This effect is caused by a decrease in elastic work related to a reduction in intrinsic PEEP. The aim of this study was to relate the decrease in inspiratory work due to CPAP to the intrinsic PEEP levels obtained during spontaneous breathing without positive pressure. Ten intubated patients with COPD who had been ventilated for acute respiratory failure were studied. Intrinsic PEEP was determined during tracheal occlusions performed at end-expiration when the patient was breathing without positive airway pressure. Inspiratory work was computed during breathing through a circuit with a CPAP of 0.5 kPa and the same circuit without positive pressure. Intrinsic PEEP-levels ranged from 0.26 to 1.31 kPa. Compared to spontaneous breathing without positive pressure, CPAP reduced the total inspiratory work per liter of ventilation (Wltot) from 1.42±0.48 to 1.24±0.50 J·1^-1 (means±SD P <0.01). This decrease was found to be related to the intrinsic PEEP-levels: the largest reductions were found in the patients with an intrinsic PEEP-level close to the CPAP-level applied. In intubated patients with COPD, the decrease in Wltot due to a CPAP of 0.5 kPa was found to be related to the intrinsic PEEP-levels present when no positive airway pressure was applied. The intrinsic PEEP measured during tracheal occlusions could be used to estimate the effect of CPAP in these patients.     

Early administration of surfactant in spontaneous breathing with nCPAP: feasibility and outcome in extremely premature infants (postmenstrual age </=27 weeks)

BACKGROUND: Spontaneous breathing supported by nasal continuous positive airway pressure (nCPAP) is thought to have some advantages compared with mechanical ventilation in extremely premature infants. In addition, early or prophylactic surfactant administration has been shown to be superior to delayed use. A strategy to combine these two principles was tested in our neonatal intensive care unit (NICU). The aim of this feasibility study was to describe the procedure and compare short-term results with a historical control. METHODS: The study took place in a level III NICU. In the observational period all extremely premature infants with clinical signs of moderate to severe respiratory distress syndrome despite nCPAP received 100 mg.kg(-1) of a natural surfactant preparation via an intratracheal catheter during spontaneous breathing. In the historical control period those infants were intubated and ventilated to receive surfactant. RESULTS: Twenty-nine of 42 infants fulfilled the criteria and were treated with the new approach. In five cases ventilation with manual bag was necessary after administration of surfactant but all infants could be retransferred to nCPAP within a few minutes. Ten infants were intubated later during the first 3 days. Mortality was 7% in the group of infants treated in this way and 12% in all infants treated during the observational period. Mortality was 35% in the historical control period. Morbidity was within ranges reported by other authors. CONCLUSIONS: Surfactant administration during nCPAP is feasible. First results indicate that early complications are rare. This warrants a prospective randomized trial.     

Airway pressure release ventilation during ex vivo lung perfusion attenuates injury

Objective

Critical organ shortages have resulted in ex vivo lung perfusion gaining clinical acceptance for lung evaluation and rehabilitation to expand the use of donation after circulatory death organs for lung transplantation. We hypothesized that an innovative use of airway pressure release ventilation during ex vivo lung perfusion improves lung function after transplantation.

Elastic work of breathing during continuous positive airway pressure in intubated patients with chronic obstructive pulmonary disease (theoretical analysis and experimental validation)

Background: Continuous positive airway pressure (CPAP) is known to decrease inspiratory work of breathing in patients with chronic obstructive pulmonary disease (COPD). This effect is primarily attributed to a reduction in inspiratory elastic work of breathing (Wi,el) related to a decrease in intrinsic positive end-expiratory pressure (PEEP).
Methods: The aim of this study is to design a model for computation of Wi,el on the basis of respiratory mechanics in patients with COPD, at various intrinsic PEEP- and CPAP-levels. The model was used to estimate the optimal CPAP-level with respect to the intrinsic PEEP-level in terms of reduction of Wi,el. Calculations of the decrease in Wi,el due to CPAP obtained with the model were compared to changes in Wi,el and total work of breathing (Wi,tot) determined from respiratory measurements in patients with COPD.
Results: Model calculations revealed that Wi,el was minimal whenever a CPAP-level equal to the intrinsic PEEP-level was applied. When a CPAP-level exceeding the intrinsic PEEP-level was applied, the reduction in Wi,el was less. Comparing these results to the respiratory measurements, a similar pattern in reduction of Wi,el and Wi,tot was established, although absolute values of the differences were smaller in the experimental data.
Conclusion: This study indicates that in order to reduce Wi, el in patients with COPD, intrinsic PEEP should be measured and the CPAP-level adjusted to the intrinsic PEEP-level.     

Evaluation of the measurement of the intraoperative transcutaneous partial pressure of oxygen (PtcO2) as a prognostic indicator in vascular reconstruction

The intraoperative transcutaneous partial pressure of oxygen (PtcO₂) was used to monitor 58 vascular reconstructive surgery procedures in 54 patients. The study comprised three groups: Group A (24 limbs without any ischemic symptoms or signs), Group B (45 limbs with intermittent claudication), and Group C (12 limbs with ischemic rest pain, ulceration, and gangrene). In addition in 31 patients the chest wall was monitored simultaneously as a control. The results showed that the PtcO₂ values increased immediately and significantly to varying degrees and at varying speeds after unclamping. The controls had higher values than Group A (P>0.05), Group B (P<0.05), and Group C (P<0.05) patients. Further study showed that there were no significant differences between the maximal values in the limbs with good distal vessel run-off in Groups A, B, and C, and in the controls (P>0.05). It is thus concluded that effective vascular reconstruction in the limbs is indicated by a rapid and marked increase of both the PtcO₂ value and the response value, while with a slow and low increase of the value, early graft failure and poor distal vessel run-off should be suspected. We believe that this monitoring method dynamically reflects the functional state during vascular reconstruction and is clinically valid.     

Duct stenting versus modified Blalock–Taussig shunt in neonates and infants with duct-dependent pulmonary blood flow: A systematic review and meta-analysis

ObjectiveThe aim of this systematic review and meta-analysis is to evaluate whether duct stenting is associated with better survival and other clinical outcomes compared with the modified Blalock–Taussig shunt in infants with duct-dependent pulmonary flow.MethodsA systematic search of the Medline, Embase, and Cochrane databases was performed by 4 independent reviewers from inception to March 2019. Meta-analysis was performed using the DerSimonian and Laird method with inverse-variance weighting. The quality of evidence was summarized using the Grading of Recommendations, Assessment, Development, and Evaluation framework.ResultsSix comparative observational studies were included, of which 3 were rated low risk of bias. There was no difference in 30-day mortality between the Blalock–Taussig shunt and duct stenting groups (risk ratio, 1.02; 95% confidence interval, 0.46-2.27; P = .96; I² = 0%). However, there was benefit in favor of duct stenting for medium-term mortality (risk ratio, 0.63; 95% confidence interval, 0.40-0.99; P = .05; I² = 0%). Duct stenting demonstrated a reduced risk for procedural complications compared with the Blalock–Taussig shunt (risk ratio, 0.50; 95% confidence interval, 0.31-0.81; P = .005; I² = 0%). However, there was an increased risk for unplanned reintervention for duct stenting (risk ratio, 1.77; 95% confidence interval, 1.39-2.26; P < .00001; I² = 10%). Duct stenting demonstrated shorter mean intensive care unit length of stay (mean difference, ?4.69 days; 95% confidence interval, ?7.30 to ?2.07; P = .0004; I² = 80%), as well as shorter hospital length of stay (mean difference, ?5.78 days; 95% confidence interval, ?9.27 to ?2.28; P = .0009, I² = 75%). The overall quality of evidence was rated low using the Grading of Recommendations, Assessment, Development, and Evaluation framework.ConclusionsDuct stenting demonstrated comparable early mortality, lower medium-term mortality, lower risk of procedural complications, and higher risk of reintervention compared with the Blalock–Taussig shunt.     

The effect of driving pressure-guided versus conventional mechanical ventilation strategy on pulmonary complications following on-pump cardiac surgery: A randomized clinical trial

Study objectivePostoperative pulmonary complications occur frequently and are associated with worse postoperative outcomes in cardiac surgical patients. The advantage of driving pressure-guided ventilation strategy in decreasing pulmonary complications remains to be definitively established. We aimed to investigate the effect of intraoperative driving pressure-guided ventilation strategy compared with conventional lung-protective ventilation on pulmonary complications following on-pump cardiac surgery.DesignProspective, two-arm, randomized controlled trial.SettingThe West China university hospital in Sichuan, China.PatientsAdult patients who were scheduled for elective on-pump cardiac surgery were enrolled in the study.InterventionsPatients undergoing on-pump cardiac surgery were randomized to receive driving pressure-guided ventilation strategy based on positive end-expiratory pressure (PEEP) titration or conventional lung-protective ventilation strategy with fixed 5 cmH₂O of PEEP.MeasurementsThe primary outcome of pulmonary complications (including acute respiratory distress syndrome, atelectasis, pneumonia, pleural effusion, and pneumothorax) within the first 7 postoperative days were prospectively identified. Secondary outcomes included pulmonary complication severity, ICU length of stay, and in-hospital and 30-day mortality.Main resultsBetween August 2020 and July 2021, we enrolled 694 eligible patients who were included in the final analysis. Postoperative pulmonary complications occurred in 140 (40.3%) patients in the driving pressure group and 142 (40.9%) in the conventional group (relative risk, 0.99; 95% confidence interval, 0.82–1.18; P = 0.877). Intention-to-treat analysis showed no significant difference between study groups regarding the incidence of primary outcome. The driving pressure group had less atelectasis than the conventional group (11.5% vs 17.0%; relative risk, 0.68; 95% confidence interval, 0.47–0.98; P = 0.039). Secondary outcomes did not differ between groups.ConclusionAmong patients who underwent on-pump cardiac surgery, the use of driving pressure-guided ventilation strategy did not reduce the risk of postoperative pulmonary complications when compared with conventional lung-protective ventilation strategy.     

Bilevel positive airway pressure for gastroscopy with sedation in patients at risk of hypoxemia: A prospective randomized controlled study

Study objectiveHypoxemia is one of the most frequent adverse events during sedated gastroscopy, and there is still no effective means to prevent and cure it. Therefore, we conducted this randomized trial to confirm our hypothesis that, compared with the nasal cannula group, bilevel positive airway pressure (BPAP) would decrease the incidence of hypoxemia in patients with obstructive sleep apnea (OSA) or overweight status undergoing gastroscopy.DesignIn a single-center, prospective, randomized controlled clinical trial, 80 patients aged 18–65 years and with OSA or overweight status who underwent gastroscopy with sedation were randomly assigned to two groups: the nasal cannula and BPAP groups. The primary outcome was the incidence of hypoxemia (75% < peripheral oxygen saturation [SpO2] < 90% for >5 sand <60 s).Main resultsCompared to the nasal cannula group, BPAP therapy significantly decreased the incidence of hypoxemia from 40.0% to 2.5% (absolute risk difference [ARD], 37.5% [95% confidence interval (CI), 21.6 to 53.4], p < 0.001), decreased subclinical respiratory depression from 52.5% to 22.5% (ARD, 30.0% [95% CI, 9.8 to 50.2], p = 0.006), and decreased severe hypoxemia from 17.5% to 0% (ARD, 17.5% [95% CI, 5.7 to 29.3], p = 0.006). The BPAP intervention also decreased the total propofol dosage and operation time and improved anesthesiologist's satisfaction.ConclusionBPAP therapy significantly decreased the incidence of hypoxemia in patients with OSA or overweight status who underwent gastroscopy.