Severe Hypercapnia during Anaesthesia under Mechanical Ventilation in Two Paediatric Patients

Introduction: Current pediatric cardiopulmonary resuscitation (CPR) guidelines recommend that a rescuer performs manual ventilation at a rate of 20-30 breaths per minute (bpm) with an avoidance of excessive ventilation during CPR. Despite these recommendations, excessive ventilation is common during CPR, and performing manual ventilation can be difficult in settings with limited personnel. Using mechanical ventilation during CPR can provide relatively constant minute ventilation and offloads a rescuer to perform other tasks. Research Question: Does mechanical ventilation produce similar gas exchange and intra-arrest hemodynamics compared to manual ventilation during CPR? Aims: To compare gas exchange and intra-arrest hemodynamics when using manual ventilation versus three mechanical ventilation strategies: sustained inflation (SI), pressure-controlled mechanical ventilation (PCV), and volume-controlled mechanical ventilation (VCV). Methods: This was a randomized, crossover study design. Twenty 4-5 kg swine were anesthetized and underwent up to 4 episodes of 1 minute of ventricular fibrillation-induced (VF) cardiac arrest and resuscitation. Each swine was assigned 4 different intra-arrest ventilatory strategies in random order including: 1) manual ventilation at a rate of 25 bpm, 2) SI at 15 cm H 2 O, 3) PCV using pre-arrest peak inspiratory pressures, and 4) VCV using a pre-arrest tidal volume. Swine were resuscitated with chest compressions at 120 compressions per minute, epinephrine administration every 4 minutes, and defibrillation as clinically indicated starting 8 minutes into resuscitation. Arterial blood gases were obtained at baseline and at 4 and 8 min of resuscitation. Arterial diastolic blood pressure (DBP), myocardial perfusion pressure (MPP), and cerebral perfusion pressure (CPP) were measured at baseline and continuously during resuscitation. Results: The twenty swine underwent a total of 32 VF cardiac arrests and resuscitation. At 4 and 8 minutes of CPR, SI, PCV, and VCV produced PaCO 2 and PaO 2 levels similar to that of manual ventilation ( Figure 1 ). DBP, MPP, and CPP levels were also similar among the 4 groups at 4 and 8 minutes of resuscitation ( Figure 2 ). Conclusion: In this swine model of short VF pediatric cardiac arrest, sustained inflation, pressure-controlled and volume-controlled mechanical ventilation are feasible and provide adequate gas exchange and similar hemodynamics compared to manual ventilation.

Spontaneous breathing during mechanical ventilation increases transpulmonary pressure and Vt, and worsens lung injury. Intuitively, controlling Vt and transpulmonary pressure might limit injury caused by added spontaneous effort. To test the hypothesis that, during spontaneous effort in injured lungs, limitation of Vt and transpulmonary pressure by volume-controlled ventilation results in less injurious patterns of inflation. Dynamic computed tomography was used to determine patterns of regional inflation in rabbits with injured lungs during volume-controlled or pressure-controlled ventilation. Transpulmonary pressure was estimated by using esophageal balloon manometry [Pl(es)] with and without spontaneous effort. Local dependent lung stress was estimated as the swing (inspiratory change) in transpulmonary pressure measured by intrapleural manometry in dependent lung and was compared with the swing in Pl(es). Electrical impedance tomography was performed to evaluate the inflation pattern in a larger animal (pig) and in a patient with acute respiratory distress syndrome. Spontaneous breathing in injured lungs increased Pl(es) during pressure-controlled (but not volume-controlled) ventilation, but the pattern of dependent lung inflation was the same in both modes. In volume-controlled ventilation, spontaneous effort caused greater inflation and tidal recruitment of dorsal regions (greater than twofold) compared with during muscle paralysis, despite the same Vt and Pl(es). This was caused by higher local dependent lung stress (measured by intrapleural manometry). In injured lungs, esophageal manometry underestimated local dependent pleural pressure changes during spontaneous effort. Limitation of Vt and Pl(es) by volume-controlled ventilation could not eliminate harm caused by spontaneous breathing unless the level of spontaneous effort was lowered and local dependent lung stress was reduced.

Airway access for mechanical ventilation can be obtained by: orotracheal intubation, nasotracheal intubation, cricothyrotomy, ortracheostomy. Laryngeal mask and Combitube are devices that can be used in patients with difficult access to the airways (“not ventilate not intubate” situation). Mechanical ventilation is are source focused on healthcare of patients with compromised pulmonary gas exchange, whether caused by structural lung disease or conditions that result in alveolar hypoventilation. There are currently many options for ventilation support, but three of them are the most frequently used: volume controlled ventilation (VCV), pressure controlled ventilation (PCV) and pressure support ventilation (PSV). VCV guarantees tidal volume, but generates higher mean airway pressures, as a consequence of an initial peak pressure; PCV does not generate pressure peak, occurring lower medium pressures, but does not guarantee tidal volume. VCV and PCV allow assisted or controlled ventilation. PSV requires initial patient’s inspiratory stimulus, only functioning on assisted ventilation, and also does not guarantee tidal volume. For most patients VCV and PCV can be used at the beginning of assisted ventilation. There is no demonstration of superiority of one over the other, provided that their limitations are respected. Positive end expiratory pressure (PEEP) and continuous positive airway pressure (CPAP) promote increases in functional residual capacity, resulting in improved blood oxygenation and reduced inspiratory effort. Both PEEP and CPAP promote these benefits through alveolar opening, when totally closed or only partially opened, and redistributing liquid eventually present in alveoli. The strategy of daily interruption of sedation helps reducing mechanical ventilation duration and intensive care unit length of stay. Patients on prolonged mechanical ventilation require gradual process of weaning from mechanical ventilation.

Cuffed tracheal tubes are increasingly used in paediatric anaesthetic practice. This study compared tidal volume and leakage around cuffed and uncuffed tracheal tubes in children who required standardised mechanical ventilation of their lungs in the operating theatre. Children (0-16 years) undergoing elective surgery requiring tracheal intubation were randomly assigned to receive either a cuffed or an uncuffed tracheal tube. Assessments were made at five different time-points: during volume-controlled ventilation 6 ml.kg-1 , PEEP 5 cmH2 O and during pressure-controlled ventilation 10 cmH2 O / PEEP 5 cmH2 O. The pressure-controlled ventilation measurement time-points were: just before a standardised recruitment manoeuvre; just after recruitment manoeuvre; 10 min; and 30 min after the recruitment manoeuvre. Problems and complications were recorded. During volume-controlled ventilation, leakage was significantly less with cuffed tracheal tubes than with uncuffed tracheal tubes; in ml.kg-1 , median (IQR [range]) 0.20 (0.13-0.39 [0.04-0.60]) vs. 0.82 (0.58-1.38 [0.24-4.85]), respectively, p < 0.001. With pressure-controlled ventilation, leakage was less with cuffed tracheal tubes and stayed unchanged over a 30-min period, whereas with uncuffed tracheal tubes, leakage was higher and increased further over the 30-min period. Tidal volumes were higher in the cuffed group and increased over time, but in the uncuffed group were lower and decreased over time. Both groups showed an increase in tidal volumes following recruitment manoeuvres. There were more short-term complications with uncuffed tracheal tubes, but no major complications were recorded in either group at long-term follow-up. With standardised ventilator settings, cuffed tracheal tubes produced better ventilation characteristics compared with uncuffed tracheal tubes during general anaesthesia for routine elective surgery.

Background:Pneumoperitoneum and altered positioning 1in laparoscopic cholecystectomy predispose to alterations in cardiorespiratory physiology. We compared the effects of volume controlled, pressure controlled, and the newly introduced pressure controlled-volume guaranteed ventilation (PCV-VG) modes of ventilation on respiratory mechanics and oxygenation during laparoscopic cholecystectomy.Materials and Methods:Seventy-five physical status American Society of Anesthesiologists Classes I and II patients with normal lungs undergoing laparoscopic cholecystectomy were randomly allocated to receive volume controlled ventilation (VCV), pressure-controlled ventilation (PCV), or PCV-VG modes of ventilation during general anesthesia. In all modes of ventilation, the tidal volume was set at 8 mL/kg, and respiratory rate was set at 12 breaths/min with inspired oxygen of 0.4. After pneumoperitoneum, respiratory rate was adjusted to maintain an end-tidal carbon dioxide between 32 and 37 mm Hg. The peak airway pressures, compliance, the mean airway pressures, oxygen saturation, end tidal carbon dioxide and hemodynamics were recorded at the time of intubation (T1), 15 min after pneumoperitoneum (T2) and after desufflation (T3) and were compared. Arterial oxygen tension, arterial carbon dioxide tension at T2 and T3 were compared.Results:PCV-VG and PCV mode resulted in lower peak airway pressures than VCV (23.04 ± 3.43, 24.52 ± 2.79, and 27.24 ± 2.37 cm of water, respectively, P = 0.001). Compliance was better preserved in the pressure mediated modes than VCV (fall from baseline was 42%, 29%, and 30% in VCV, PCV, and PCV-VG). The arterial to end-tidal carbon dioxide gradient was lower in PCV-VG and PCV compared to VCV. No difference in oxygenation and hemodynamics were observed.Conclusion:PCV and PCV-VG modes are superior to VCV mode in providing adequate oxygenation at lower peak inspiratory pressures.

Objective To compare the pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV) in the patients undergoing spinal surgery in prone position supported by a Wilson frame.Methods Forty patients,of ASA physical status Ⅰ or Ⅱ,aged 30-64 yr,with body mass index ＜ 30 kg/m2,scheduled for elective spinal surgery in prone position supported by a Wilson frame under general anesthesia,were randomly allocated to receive mechanical ventilation using either VCV (n =20) or PCV (n =20) mode.Endotracheal intubation and mechanical ventilation were performed after induction of anesthesia.The tidal volume (VT) was set at 10 ml/kg according to the ideal body weight in group VCV.The maximal inspiratory pressure of the anesthesia machine was adjusted to maintain the VT at 10 ml/kg in group P.Both ventilation modes were required to maintain PET CO2 within the normal range.VT,respiratory rate,minute ventilation (MV),dynamic lung compliance (Cdyn),peak and mean airway pressure (Ppeak,Pmean),mean arterial pressure (MAP) and HR were recorded at 10 min after the patients were turned to supine position and at 30 min after the patients were turned to prone position after intubation.Arterial blood samples were collected for blood gas analysis,and oxygenation index(OI) and physiologic dead space fraction (VD/VT) were calculated.Results Compared with those at 10 min after turning to supine position,Ppeak was significantly increased and Cdyn,VT and MV were decreased at 30 min after turning to prone position in both groups.Compared with group VCV,Ppeak was significantly decreased,respiratory rate and Cdyn were increased,and no significant change was found in VT,MV,OI,VD/VT,Pmean,MAP and HR in PCV group.Conclusion Compared with VCV,PCV can improve the ventilatory efficacy and reduce the influence of prone position on respiratory dynamics in the patients undergoing spinal surgery in prone position supported by a Wilson frame. Key words: Respiration, artificial ; Prone position ; Wilson frame

To determine how percutaneous tracheostomy (PT) impacts on respiratory system compliance (Crs) and end-expiratory lung volume (EELV)during volume control ventilation and to test whether a recruitment maneuver (RM) at the end of PT may reverse lung derecruitment. This is a single center, prospective, applied physiology study. 25 patients with acute brain injury who underwent PT were studied. Patients were ventilated in volume control ventilation. Electrical impedance tomography (EIT) monitoring and respiratory mechanics measurements were performed in three steps: (a) baseline, (b) after PT, and (c) after a standardized RM (10 sighs of 30 cmH2O lasting 3s each within 1min). End-expiratory lung impedance (EELI) was used as a surrogate of EELV. PT determined a significant EELI loss (mean reduction of 432 arbitrary units p = 0.049) leading to a reduction in Crs (55 ± 13 vs. 62 ± 13 mL/cmH2O; p < 0.001) as compared to baseline. RM was able to revert EELI loss and restore Crs (68 ± 15 vs. 55 ± 13 mL/cmH2O; p < 0.001). In a subgroup of patients (N = 8, 31%), we observed a gradual but progressive increase in EELI. In this subgroup, patients did not experience a decrease of Crs after PT as compared to patients without dynamic inflation. Dynamic inflation did not cause hemodynamic impairment nor raising of intracranial pressure. We propose a novel and explorative hyperinflation risk index (HRI) formula. Volume control ventilation did not prevent the PT-induced lung derecruitment. RM could restore the baseline lung volume and mechanics. Dynamic inflation is common during PT, it can be monitored real-time by EIT and anticipated by HRI. The presence of dynamic inflation during PT may prevent lung derecruitment.

It is controversial as to which ventilation mode is better during one-lung ventilation (OLV). This study was designed to figure out whether there was any difference between volume controlled ventilation (VCV) and pressure controlled ventilation (PCV) on oxygenation and postoperative complications under the condition of protective ventilation (PV). Sixty-five patients undergoing video-assisted thoracoscopic lobectomy were randomized into two groups. Patients in group V received VCV mode during OLV while patients in group P received PCV. The tidal volume (VT) in both groups was 6 mL per predicted body weight (PBW). Positive end-expiratory pressure (PEEP) was set at the level of 5 cmH2O in both groups. Arterial gas analysis were performed preoperatively with room air (T0), at 15 mins (T1) and 1 h (T2) after OLV, at the end of OLV (T3), 30 min after PACU admission (T4), 24 h after surgery (post-operative day 1, POD1) and 48 h after surgery (post-operative day 2, POD2). Peak inspiratory airway pressure (Ppeak) and plateau airway pressure (Pplat) were recorded at T1, T2 and T3. The perioperative complications were also recorded. Sixty-four patients completed this study. Ppeak in group V was significantly higher than that in group P (T1 22.3±2.9 vs. 18.7±2.1 cmH2O; T2 22.2±2.8 vs. 18.7±2.6 cmH2O). There were no differences with Pplat and intraoperative oxygenation index (T1 203.3±109.7 vs. 198.1±93.4; T2 216.8±79.1 vs. 232.1±101.4). The postoperative oxygenation index (T4 525.0±160.9 vs. 520.7±127.1, post-operative day 1 (POD1) 452.1±161.3 vs. 446.1±109.1; post-operative day 2 (POD2) 403.8±93.4 vs. 396.7±92.8) and postoperative complications were also comparable between these two groups. When they were utilized during OLV, PCV and VCV had the same performance on the intraoperative oxygenation and postoperative complications under the condition of PV.

PurposePressure-controlled volume-guaranteed (PCV-VG) combines the characteristics of pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV). It has been reported that PCV-VG decreases airway pressure and improves oxygenation among the adult group. In this study, the respiratory dynamics of PCV-VG and VCV are compared in pediatric patients ventilated with laryngeal mask airway and underwent laparoscopic hernia of the sac ligation.Patients and MethodsSixty-four pediatric patients were included in this prospective, randomized clinical trial. Pediatric patients were randomly allocated to receive VCV and PCV-VG ventilation during the general anesthesia. The hemodynamic and respiratory variables were recorded at the time when laryngeal mask airway was placed, pneumoperitoneum began, 5 mins after pneumoperitoneum began, pneumoperitoneum ended, and the operation ended respectively. The respiratory adverse events were recorded after the operation and on the first day after the operation. In this study, respiratory adverse events are defined as cough, hoarseness, hypoxemia, laryngospasm, bronchospasm, and sore throat.ResultsThere was no statistical difference in hemodynamic variables at all time points between the two groups. Compared to the VCV group, peak airway pressure (Ppeak) and plateau airway pressure in the PCV-VG group decreased significantly. Pulmonary dynamic compliance (Cydn) in the PCV-VG group was significantly higher than that in the VCV group. The respiratory adverse events appeared to have no statistical difference between VCV and PCV groups.ConclusionPCV-VG provides a lower Ppeak and better Cydn in pediatric patients compared with the VCV group during laparoscopic surgery. The results suggested that PCV-VG may be a superior way of mechanical ventilation for pediatric patients who ventilated with laryngeal mask airway and experienced laparoscopic surgery.

Background: Precise control of minute ventilation is essential during the intraoperative anesthetic care of infants and children, as increased tidal volume (Vt) and consequently increased peak inflating pressure (PIP), may lead to volutrauma or barotrauma. During the intraoperative delivery of aerosolized medications such as albuterol, the additional flow required for delivery through nebulizers may alter Vt and secondarily PIP. The current study explores Vt changes during the use of a novel nebulizing device (Aerogen vibrating mesh) for the delivery of an aerosolized medication during mechanical ventilation. Methods: Using a lung analogue model, this in vitro study compared the set Vt on the anesthesia ventilator to the internally measured inspiratory and expiratory Vt on the Avance CS2 anesthesia machine during both pressure-controlled (PC) and volume-controlled (VC) modes while administering aerosols using the Aerogen device. Results: A total of 250 simulated breaths were delivered using the two modes of PC ventilation (PIP 15 and 20 cm H2O) and VC ventilation (Vt of 150 and 300 mL). In both PC and VC modes, there were no clinically significant differences between the set and the inspiratory or expiratory Vt or PIP at baseline when compared to those achieved following the addition of a continuous aerosol using the Aerogen device. Conclusions: The novel technology of the Aerogen vibrating mesh device allows the delivery of continuous aerosolized medications during intraoperative mechanical ventilation using a standard anesthesia circle system. The Aerogen device can be inserted between the Y-piece of the anesthesia circuit and the 15-mm adaptor of the endotracheal to easily allow the delivery of aerosolized medications without changes in mechanical ventilation parameters.

Partial liquid ventilation (PLV) has been shown to be an effective means of improving oxygenation in the injured lung. However, little is known about how approach to ventilation during PLV affects gas exchange and pulmonary mechanics. We hypothesized that gas exchange and pulmonary mechanics would be best with positive end-expiratory pressure (PEEP) set above the lower inflection point (LIP) of the pressure-volume (P-V) curve regardless of mode of ventilation or inspiratory to expiratory time (I:E) ratio and that the efficiency of ventilation would be greatest with volume-controlled ventilation (VCV) compared with pressure-controlled ventilation (PCV) and with long inspiratory time as compared with short inspiratory time. Lung injury was induced in 14 sheep by lavage, 10 of which were studied. Sheep were then assigned to high-PEEP (Group H, n = 5) and low-PEEP (Group L, n = 5) groups. In Group H applied PEEP was set at the LIP and in Group L applied PEEP was set at 5 cm H2O after the lung was filled with perflubron (PFB). We randomly compared VCV and PCV with I:E ratios of 1:2, 1:1, and 2:1. Peak inspiratory pressure and VT were adjusted to maintain a constant end-inspiratory plateau pressure (Pplat) of about 25 cm H2O in both groups and a constant total PEEP of about 5 cm H2O in Group L and about 12 cm H2O in Group H. There were no differences in oxygenation among modes in Group H. In Group L VCV 2:1 and all of the PCV modes in Group L had a lower PaO2 than VCV 1:1 (p < 0.05). PaCO2 and VD/VT were significantly different (p < 0.05) among modes. VD/VT was highest during PCV 1:2 with PEEP of 5 cm H2O (p < 0.05). Quasi-static compliance in Group H was higher than in Group L (p < 0.05). We conclude that during low PEEP gas exchange deteriorated in VCV with long inspiratory time and in PCV. Oxygenation was enhanced during VCV 1:1 when compared with VCV at longer I:E ratios or PCV at any I:E ratio. With PEEP set at the LIP, adequate gas exchange and improved lung mechanics could be obtained in all modes assessed.

Cardiopulmonary bypass deteriorates pulmonary functions to a certain extent. Patients with chronic obstructive pulmonary disease (COPD) are associated with increased mortality and morbidity risks in the postoperative period of open-heart surgery. In this study we compared 2 different mechanical ventilation modes, pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV), in this particular patient population. Forty patients with severe COPD were assigned to 1 of 2 groups and enrolled to receive PCV or VCV in the postoperative period. Arterial blood gases, respiratory parameters, and intensive care unit and hospital stays were compared between the 2 groups. Maximum airway pressure was higher in the VCV group. Pulmonary compliance was lower in the VCV group and minute ventilation was significantly lower in the group ventilated with PCV mode. The respiratory index was increased in the PCV group compared with the VCV group and with preoperative findings. Duration of mechanical ventilation was significantly shorter with PCV; however, intensive care unit and hospital stays did not differ. There is not a single widely accepted and established mode of ventilation for patients with COPD undergoing open-heart surgery. Our modest experience indicated promising results with PCV mode; however, further studies are warranted.

Mechanical ventilation mode (volume × pressure) does not change the variables obtained by indirect calorimetry in critically ill patients

Background Although numerous studies conducted in the past years, there is no superior guideline that indicates the best ventilation mode during laparoscopic anesthesia inobese patients. There are numerous studies with dissimilar controversial points. The management of oxygenation in a morbid obese patient undergoing laparoscopic procedures presents many challenging aspects to the anesthetist. Objective The aim of this study was to equate the effect of pressure controlled ventilation (PCV) vs. volume controlled ventilation (VCV) on respiratory, oxygenation parameters and post operative complications. Patients and Methods This study was conducted on 80 patients who underwent laparoscopic gastric sleeve surgery in Ain Shams University Hospitals. Post induction of Anesthesia, Patients were divided into two groups. The first group mechanical ventilation setting was volume controlled ventilation and the second group mechanical ventilation setting was pressure controlled ventilation. Results The results of our study shows that despite some valuable effects regarding plateau and mean airway pressure with PCV, there is no momentous clinical difference between volume controlled ventilation (VCV) and pressure controlled ventilation (PCV) in obese patients undergoing laparoscopic gastric sleeve surgery. However, pressure controlled ventilation shows slightly more favorable results regarding post extubation oxygen saturation and the decrease of post operative basal atelectasis. It appears that using dual modes would be an epitome approach with lower complications and similar outcomes.

Terminology vs Physiology and Mechanics