Feasibility and Effect of Physiological-Based CPAP in Preterm Infants at Birth

Background: Preterm infants are commonly supported with 5–8 cmH2O CPAP. However, animal studies demonstrate that high initial CPAP levels (12–15 cmH2O) which are then reduced (termed physiological based (PB)-CPAP), improve lung aeration without adversely affecting cardiovascular function. We investigated the feasibility of PB-CPAP and the effect in preterm infants at birth.Methods: Preterm infants (24–30 weeks gestation) were randomized to PB-CPAP or 5–8 cmH2O CPAP for the first 10 min after birth. PB-CPAP consisted of 15 cmH2O CPAP that was decreased when infants were stabilized (heart rate ≥100 bpm, SpO2 ≥85%, FiO2 ≤ 0.4, spontaneous breathing) to 8 cmH2O with steps of ~2/3 cmH2O/min. Primary outcomes were feasibility and SpO2 in the first 5 min after birth. Secondary outcomes included physiological and breathing parameters and short-term neonatal outcomes. Planned enrollment was 42 infants.Results: The trial was stopped after enrolling 31 infants due to a low inclusion rate and recent changes in the local resuscitation guideline that conflict with the study protocol. Measurements were available for analysis in 28 infants (PB-CPAP n = 8, 5–8 cmH2O n = 20). Protocol deviations in the PB-CPAP group included one infant receiving 3 inflations with 15 cmH2O PEEP and two infants in which CPAP levels were decreased faster than described in the study protocol. In the 5–8 cmH2O CPAP group, three infants received 4, 10, and 12 cmH2O CPAP. During evaluations, caregivers indicated that the current PB-CPAP protocol was difficult to execute. The SpO2 in the first 5 min after birth was not different [61 (49–70) vs. 64 (47–74), p = 0.973]. However, infants receiving PB-CPAP achieved higher heart rates [121 (111–130) vs. 97 (82–119) bpm, p = 0.016] and duration of mask ventilation was shorter [0:42 (0:34–2:22) vs. 2:58 (1:36–6:03) min, p = 0.020]. Infants in the PB-CPAP group required 6:36 (5:49-11:03) min to stabilize, compared to 9:57 (6:58–15:06) min in the 5–8 cmH2O CPAP group (p = 0.256). There were no differences in short-term outcomes.Conclusion: Stabilization of preterm infants with PB-CPAP is feasible but tailoring CPAP appeared challenging. PB-CPAP did not lead to higher SpO2 but increased heart rate and shortened the duration of mask ventilation, which may reflect faster lung aeration.

Dry Wearable Textile Electrodes for Portable Electrical Impedance Tomography

Electrical impedance tomography (EIT), a noninvasive and radiation-free medical imaging technique, has been used for continuous real-time regional lung aeration. However, adhesive electrodes could cause discomfort and increase the risk of skin injury during prolonged measurement. Additionally, the conductive gel between the electrodes and skin could evaporate in long-term usage and deteriorate the signal quality. To address these issues, in this work, textile electrodes integrated with a clothing belt are proposed to achieve EIT lung imaging along with a custom portable EIT system. The simulation and experimental results have verified the validity of the proposed portable EIT system. Furthermore, the imaging results of using the proposed textile electrodes were compared with commercial electrocardiogram electrodes to evaluate their performance.

Lung ultrasound and the role of lung aeration score in patients with acute respiratory distress syndrome on extracorporeal membrane oxygenation

Objective: This was a pilot study to determine the utility of daily lung ultrasound (LUS) in patients requiring veno-venous extracorporeal membrane oxygenation (VV-ECMO) for acute respiratory distress syndrome (ARDS). Design: This was a prospective, observational study. Setting: The study took place in the intensive care unit at Royal Papworth Hospital in Cambridge, UK. Participants: We recruited adult patients receiving VV-ECMO for ARDS. Interventions: All patients received a lung computed tomography (CT) scan and LUS on admission. Bedside chest radiography (CXR) and LUS were done on a daily basis until patients were decannulated. Measurements and main results: Daily LUS aeration scores were calculated according to the appearance of four defined patterns. An independent radiologist calculated corresponding scores for CT and CXR, retrospectively. These were checked for correlation with LUS aeration scores. There were statistically significant correlations between LUS versus CT ( r = 0.868, p = 0.002) and LUS versus CXR ( r = 0.498, p = 0.018) with good agreement and no evidence of proportional bias. LUS was able to detect 13.5% of pleural effusions and 54.2% of pneumothorax that were not picked up on CXR. In most of the patients who were weaned off VV-ECMO, a progressive reduction of LUS aeration scores corresponding to lung re-aeration was observed. Conclusions: LUS correlated with findings on CT and CXR for quantifying lung aeration and the clinical presentation of patients. LUS also picked up more pleural effusions and pneumothorax than CXR. Together with traditional imaging techniques, the routine use of LUS should be considered for this patient group.

Lung Ultrasonography as Tool for Follow Up of Ventilated Neonates for Prediction of Weaning Readiness

Background Timing is crucial when deciding if a patient can be successfully extubated. Both premature discontinuation and unnecessary delay of mechanical ventilation weaning have been associated with poor outcome. There are no enough guidelines for the assessment of readiness of newborns for extubation. The degree of lung aeration loss in different clinical conditions can be quantified via lung ultrasound (LUS). Objectives To evaluate the lung ultrasound score as a follow up tool in ventilated neonates and its validity as predictor of extubation. Subjects and Methods Prospective study done on 39 mechanically ventilated neonates 27-42 weeks’ gestation. Lung ultrasound was done daily for each patient till the day of weaning and lung ultrasound (LUS) score was calculated. Patients were divided into 2 groups according to trial of weaning; Success “S” group: in which weaning succeeded and Failure “F” group: in which weaning failed. Results The “F” group had significantly higher LUS score at time of intubation, pre- extubation and post-extubation compared with the “S” group (P- value= 0.002, 0.003 and 0.001 respectively). A cut off value of ≤ 10 for LUS score pre-extubation predict successful weaning with sensitivity 76% and specificity 64.3%. Conclusion LUS is an indicator for lung aeration and can be used as a tool to predict success of weaning of ventilated neonates.

Evaluation of Lung Aeration and Respiratory System Mechanics in Obese Dogs Ventilated With Tidal Volumes Based on Ideal vs. Current Body Weight

We describe the respiratory mechanics and lung aeration in anesthetized obese dogs ventilated with tidal volumes (VT) based on ideal (VTi) vs. current (VTc) body weight. Six dogs with body condition scores ≥ 8/9 were included. End-expiratory respiratory mechanics and end-expiratory CT-scan were obtained at baseline for each dog. Thereafter, dogs were ventilated with VT 15 ml kg−1 based on VTi and VTc, applied randomly. Respiratory mechanics and CT-scan were repeated at end-inspiration during VTi and VTc. Data analyzed with linear mixed models and reported as mean ± SD or median [range]. Statistical significance p < 0.05. The elastance of the lung, chest wall and respiratory system indexed by ideal body weight (IBW) were positively correlated with body fat percentage, whereas the functional residual capacity indexed by IBW was negatively correlated with body fat percentage. At end-expiration, aeration (%) was: hyperaeration 0.03 [0.00–3.35], normoaeration 69.7 [44.6–82.2], hypoaeration 29.3 [13.6–49.4] and nonaeration (1.06% [0.37–6.02]). Next to the diaphragm, normoaeration dropped to 12 ± 11% and hypoaeration increased to 90 ± 8%. No differences in aeration between groups were found at end-inspiration. Airway driving pressure (cm H2O) was higher (p = 0.002) during VTc (9.8 ± 0.7) compared with VTi (7.6 ± 0.4). Lung strain was higher (p = 0.014) during VTc (55 ± 21%) than VTi (38 ± 10%). The stress index was higher (p = 0.012) during VTc (SI = 1.07 [0.14]) compared with VTi (SI = 0.93 [0.18]). This study indicates that body fat percentage influences the magnitude of lung, chest wall, and total respiratory system elastance and resistance, as well as functional residual capacity. Further, these results indicate that obese dogs have extensive areas of hypoaerated lungs, especially in caudodorsal regions. Finally, lung strain and airway driving pressure, surrogates of lung deformation, are higher during VTc than during VTi, suggesting that in obese anesthetized dogs, ventilation protocols based on IBW may be advantageous.

Lung-protective Ventilation Combined With Pressure-controlled Ventilation Volume-guaranteed in Children Undergoing One-lung Ventilation: A Randomised Controlled Trial

The purpose of study was to evaluate the effect of lung-protective ventilation (LPV) combined with PCV-VG in children undergoing OLV. Patients were randomly assigned to the LPV combined with PCV-VG group (PCV-VG) or LPV group (volume-controlled ventilation). Both groups received tidal-volume ventilation of 8 ml kg-1 body weight during two-lung ventilation, 6 ml kg‑1 during OLV, with sustained 5 cmH2O positive end-expiratory pressure.The PCV-VG group exhibited lower PIP than the LPV group at T1 (16.8±2.3 vs. 18.7±2.7, P=0.001), T2 (20.2±2.7 vs. 22.4±3.3, P=0.001), and T3 (23.8±3.2 vs. 26.36±3.7, P=0.01). Dynamic compliance was higher in the PCV-VG group at T1, T2 , and T3 (P=0.01). After anaesthesia induction, lung aeration deteriorated, but with no immediate postoperative difference in both groups. Postoperative lung aeration improved and returned to normal from 2.5 h postextubation in both groups. No differences were observed in postoperative pulmonary complications, intra-operative desaturation, hospital stay. In paediatric patients, who underwent thoracoscopic surgery, PCV-VG combined with LPV was superior to LPV in its ability to provide ventilation with lower PIP and higher dynamic compliance. However, the long-term benefits of different ventilation strategies should be further investigated.

Increased end-expiratory pressures improve lung function in near-term newborn rabbits with elevated airway liquid volume at birth

Approximately 53% of near-term newborns admitted into intensive care, experience respiratory distress. These newborns are commonly delivered by caesarean section and have elevated airway liquid volumes at birth, which can cause respiratory morbidity. We investigated the effect of providing respiratory support with a positive end expiratory pressure (PEEP) of 8cmH2O on lung function in newborn rabbit kittens with elevated airway liquid volumes at birth.Near-term rabbits (30d; term=32d) with airway liquid volumes that corresponded to vaginal delivery (~7mL/kg, Control, n=11) or caesarean section (~37mL/kg; Elevated Liquid (EL), n=11) were mechanically ventilated (tidal volume=8mL/kg). The PEEP was changed after lung aeration from 0 to 8 to 0 cmH2O (Control, n=6; EL, n=6) and in a separate group of kittens, PEEP was changed after lung aeration from 8 to 0 to 8 cmH2O (Control, n=5; EL, n=5). Lung function (ventilator parameters, compliance, lung gas volumes and distribution of gas within the lung) was evaluated using plethysmography and synchrotron-based phase contrast X-ray imaging. EL kittens initially receiving 0 cmH2O PEEP had reduced functional residual capacities and lung compliance, requiring higher inflation pressures to aerate the lung compared to Control kittens. Commencing ventilation with 8 cmH2O PEEP mitigated the adverse effects of EL, increasing lung compliance, functional residual capacity and the uniformity and distribution of lung aeration, but did not normalize aeration of the distal airways. Respiratory support with PEEP supports lung function in near-term newborn rabbits with elevated airway liquid volumes at birth who are at greater risk of suffering respiratory distress.

Diaphragm dysfunction, lung aeration loss and weaning-induced pulmonary oedema in difficult-to-wean patients

Background Diaphragm dysfunction and weaning-induced pulmonary oedema are commonly involved during weaning failure, but their physiological interactions have been poorly reported. Our hypothesis was that diaphragm dysfunction is not particularly associated with weaning-induced pulmonary oedema. Methods It was a single-centre and physiological study conducted in patients who had failed a first spontaneous breathing trial and who underwent a second trial. The diaphragm function was evaluated by measuring the tracheal pressure generated in response to a bilateral magnetic phrenic nerves stimulations. Weaning-induced pulmonary oedema was diagnosed in case of failure of the spontaneous breathing trial if patients exhibited signs of plasma concentration or echocardiographic diagnosis of pulmonary artery occlusion pressure elevation. Results Fifty-three patients were included and 31/53 (58%) failed the spontaneous breathing trial, including 24/31 (77%) patients with weaning-induced pulmonary oedema. Diaphragm dysfunction was present in 33/53 (62%) patients. Diaphragm dysfunction or weaning-induced pulmonary oedema were present in 26/31 (84%) of the patients who failed the spontaneous breathing trial. Weaning-induced pulmonary oedema occurred in 20/33 (61%) patients with a diaphragm dysfunction and in 4/20 (20%) patients without (p = 0.005). Conclusion Weaning-induced pulmonary oedema was three times more frequent in case of diaphragm dysfunction. Even in case of diaphragm dysfunction, physicians might be encouraged to investigate the presence of weaning-induced pulmonary oedema during weaning failure.

Assessment of the Effect of Recruitment Maneuver on Lung Aeration Through Imaging Analysis in Invasively Ventilated Patients: A Systematic Review

Background: Recruitment maneuvers (RMs) have heterogeneous effects on lung aeration and have adverse side effects. We aimed to identify morphological, anatomical, and functional imaging characteristics that might be used to predict the RMs on lung aeration in invasively ventilated patients.Methods: We performed a systemic review. Studies included invasively ventilated patients who received an RM and in whom re-aeration was examined with chest computed tomography (CT), electrical impedance tomography (EIT), and lung ultrasound (LUS) were included.Results: Twenty studies were identified. Different types of RMs were applied. The amount of re-aerated lung tissue after an RM was highly variable between patients in all studies, irrespective of the used imaging technique and the type of patients (ARDS or non-ARDS). Imaging findings suggesting a non-focal morphology (i.e., radiologic findings consistent with attenuations with diffuse or patchy loss of aeration) were associated with higher likelihood of recruitment and lower chance of overdistention than a focal morphology (i.e., radiological findings suggestive of lobar or segmental loss of aeration). This was independent of the used imaging technique but only observed in patients with ARDS. In patients without ARDS, the results were inconclusive.Conclusions: ARDS patients with imaging findings suggestive of non-focal morphology show most re-aeration of previously consolidated lung tissue after RMs. The role of imaging techniques in predicting the effect of RMs on re-aeration in patients without ARDS remains uncertain.