Pressure versus volume-controlled ventilation with a laryngeal mask airway in paediatric patients

Pressure-Controlled Volume-Guaranteed Ventilation Improves Respiratory Dynamics in Pediatric Patients During Laparoscopic Surgery: A Prospective Randomized Controlled Trial

Purpose

Pressure-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 Methods

Sixty-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.

Results

There 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.

Conclusion

PCV-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.

Clinical assessment of the efficacy of supraglottic airway devices compared with endotracheal tubes in cats during volume-controlled ventilation

The efficacies of a supraglottic airway device (SGAD) and an endotracheal tube (ETT) in cats under general anesthesia with volume-controlled ventilation (VCV) were compared. Thirty healthy cats were randomly allocated for airway control using either an SGAD or an ETT. Five tidal volumes (6, 8, 10, 12, and 14 mL/kg) were randomly tested, and respiratory rates were adjusted to achieve a minute ventilation of 100 mL/kg/min. The dose of propofol necessary to insert the SGAD or ETT, the static respiratory pressure, leakage during VCV, and end tidal CO₂ (ETCO₂) were recorded. Dosages of propofol and static respiratory measurements for the SGAD and ETT groups were compared using a t-test. The distribution of leakages and hypercapnia (ETCO₂ > 45 mmHg) were compared using Fisher's exact test. A significance level of p < 0.05 was established. No significant difference in dose of propofol was observed between the SGAD and ETT groups (7.1 ± 1.0, 7.3 ± 1.7 mg/kg; p = 0.55). Static resistance pressure of the SGAD (22.0 ± 8.1 cmH₂O/L/sec) was significantly lower than that of the ETT (36.6 ± 12.9 cmH₂O/L/sec; p < 0.01). Of the 75 trials, leakage was more frequent when using an SGAD (8 events) than when using an ETT (1 event; p = 0.03). Hypercapnia occurred more frequently with SGAD (18 events) than with ETT (3 events; p < 0.01). Although intubation with an ETT is the gold standard in small animal anesthesia, the use of an SGAD can reduce airway resistance and the work of breathing. Nonetheless, SGAD had more dead space and the tidal volume for VCV needs adjustment.

Clinical Comparison of I-Gel Supraglottic Airway Device and Cuffed Endotracheal Tube for Pressure-Controlled Ventilation During Routine Surgical Procedures

Objective

Recently, there has been a trend favouring the use of supraglottic airway devices over endotracheal tubes (ETT) during short surgical procedures. In this study, we are going to assess the suitability of one such supraglottic airway device, i-gel, for pressure-controlled ventilation (PCV) during routine surgical procedures.

Methods

The airway management for 60 patients was done with either i-gel (Group I) or cuffed tracheal tube (Group E) for this prospective, randomised, double-blinded study. Insertion time, number of attempts, ease of insertion and haemodynamic monitoring were recorded before, during and after insertion of these devices. Airway leak tests, leak volume and leak fraction were measured at 15, 20 and 25 cm H₂O PCV, and pharyngolaryngeal morbidity was evaluated postoperatively.

Results

I-gel is easier to insert than a tracheal tube (p=0.0056). The increase in heart rate and MAP was higher following insertion of tracheal tube in the first few minutes (p<0.001) and subsequently became comparable between the two groups. The leak volume and leak fraction between the two groups were comparable at 15 cm H₂O PCV, but significant difference was seen at 20 and 25 H₂O PCV between the two groups (p=0.232, p<0.001, p<0.001). Thirty minutes later, the leak volume and leak fraction between groups were comparable at 15 cm H₂O PCV (p=0.495, p=0.104) but not at 20 and 25 H₂O PCV (p<0.001, p<0.001). Pharyngolaryngeal morbidity was significantly lesser in the i-gel group.

Conclusion

I-gel provides a reasonable alternative to cuffed ETT for pressure-controlled ventilation provided the pressures can be limited to 15 to 20 cm H₂O.

A randomized comparison of volume- and pressure-controlled ventilation in children with the i-gel: Effects on peak inspiratory pressure, oropharyngeal leak pressure, and gastric insufflation

BACKGROUND

The i-gel provides good airway sealing but gastric insufflation may occur when peak inspiratory pressure (PIP) exceeds the sealing pressure of the i-gel without a gastric tube. Pressure-controlled ventilation (PCV) provides lower PIP compared with volume-controlled ventilation (VCV) and low PIP may reduce the incidence of gastric insufflation in children during positive pressure ventilation. This study was designed to evaluate PIP, oropharyngeal leak pressure, and gastric insufflation during VCV or PCV in children undergoing general anesthesia with i-gel without a gastric tube in situ.

METHODS

A prospective, randomized-controlled study was conducted. Thirty-four children, aged 6 to 84 months, were randomly allocated into the VCV or PCV group. Fiberoptic bronchoscopy was performed to confirm appropriate position of i-gel. Oropharyngeal leak pressure and PIP were measured after i-gel insertion, after caudal block, and after surgery. Ultrasonography was performed to detect gastric insufflation. Gastric tube was not inserted.

RESULTS

PIP in cm H2O was significantly lower in the PCV group than in the VCV group after i-gel insertion (10 [9-12] vs 12 [11-15], P = .021), after caudal block (11 [10-12] vs 13 [11-15], P = .014), and after surgery (10 [10-12] vs 13 [11-14], P = .002). There was no difference in the incidence of gastric insufflation between the 2 groups (4/17 in the VCV group and 3/17 in the PCV group) (P > .999).

CONCLUSION

When i-gel was used without a gastric tube, gastric insufflation occurred regardless of the ventilation modes, which provided different PIP.

Supraglottic airway devices vs tracheal intubation in children: a quantitative meta-analysis of respiratory complications

BACKGROUND

Rate of perioperative respiratory complications between tracheal intubation (TI) and laryngeal mask airway remains unclear during pediatric anesthesia.

OBJECTIVES

The aim of the present meta-analysis was to compare the perioperative respiratory complications between laryngeal mask airway and TI.

METHODS

A meta-analysis of available controlled studies comparing laryngeal mask airway to TI was conducted. Studies including patients with airway infection were excluded. Data from each trial were combined to calculate the pooled odds ratios (OR) or mean difference (MD) and 95% confidence intervals.

RESULTS

The meta-analysis was performed on 19 studies. In 12 studies, patients were given muscle relaxation, and in 16 studies, ventilation was controlled. During recovery from anesthesia, the incidence of desaturation (OR = 0.34 [0.19-0.62]), laryngospasm (OR = 0.34 [0.2-0.6]), cough (OR = 0.18 [0.11-0.27]), and breath holding (0.19 [0.05-0.68]) was lower when laryngeal mask airway was used to secure the airway. Postoperative incidences of sore throat (OR = 0.87 [0.53-1.44]), bronchospasm (OR = 0.56 [0.25-1.25]), aspiration (1.33 [0.46-3.91]) and blood staining on the device (OR = 0.62 [0.21-1.82]) did not differ between laryngeal mask airway and TI. Results were homogenous across the studies, with the exceptions of blood staining on the device.

CONCLUSIONS

This meta-analysis found that the use of laryngeal mask airway in pediatric anesthesia results in a decrease in a number of common postanesthetic complications. It is therefore a valuable device for the management of the pediatric airway.

The effect of head rotation on efficiency of ventilation and cuff pressure using the PLMA in pediatric patients

Background

This study examined whether changing the head position from neutral to side can affect expiratory tidal volume (TV) and cuff pressure when the appropriate sizes of a Proseal™ Laryngeal Mask Airway (PLMA)-depending on the body weight -are used in pediatric patients during pressure controlled ventilation (PCV).

Methods

Seventy-seven children (5-30 kg) were divided into three groups according to their body weight, PLMA#1.5 (group I, n = 24), #2 (group II, n = 26), and #2.5 (group III, n = 27). After anesthesia induction, a PLMA was placed with a cuff-pressure of 60 cmH₂O. The TV and existence of leakage at the peak inspiratory pressure (PIP) of 20 cmH₂O, and the appropriate PIP for TV 10 ml/kg were examined. Upon head rotation to the left side, the TV, PIP, cuff pressure changes, and the appropriate PIP to achieve a TV 10 ml/kg were evaluated.

Results

Head rotation of 45 degrees to the left side during PCV caused a significant increase in cuff pressure and a decrease in TV, and there was no definite leakage. Changes in PIP and TV were similar in the three groups. The cuff pressure increased but there was no significant difference between the three groups.

Conclusions

Although cuff pressure and TV of the PLMA were changed significantly after turning the head from the neutral position to the side, a re-adjustment of the cuff pressure and PIP to maintain a TV of 10 ml/kg can make the placed PLMA useful and successful in pediatric patients under general anesthesia.

Pressure vs. volume control ventilation: effects on gastric insufflation with size-1 LMA

BACKGROUND

In this randomized prospective study, peak airway pressure (PAP) and gastric insufflation were compared between volume control ventilation (VCV) and pressure control ventilation (PCV) using size-1 laryngeal mask airway (LMA) in babies weighing 2.5-5 kg.

METHODS

Forty ASA I and II children, weighing 2.5-5 kg, undergoing elective infraumbilical surgeries (duration < 60 min) were randomized to two groups of 20 each to receive either PCV or VCV. Patients at risk of aspiration, difficult airway and upper respiratory tract infection, and poor lung compliance were excluded. Anesthesia technique included sevoflurane/O(2)/N(2)O without neuromuscular blockade. PAP in PCV and tidal volume in VCV modes were changed to achieve adequate ventilation (P(E)CO(2) of 5-5.4 kPa). PAP was maintained below 20 cm H(2)O. Chi-squared test, Mann-Whitney U-test and Wilcoxon W-test were applied; P < 0.05 was considered significant.

RESULTS

Mean PAP (cm H(2)O) was 12.2 ± 1.09 in PCV and 13.60 ± 0.94 in VCV groups (P = 0.000). The confidence interval of mean difference of PAP varied from 0.79 to 2.10. Significant increases in abdominal circumference were observed in both groups: PCV: 0.94 ± 1.04 cm and VCV: 2.2 ± 1.3 cm; (P = 0.000). The SpO(2) and hemodynamic variables did not differ between the groups. One patient in VCV group (with PAP = 14 cm H(2)O) could not be ventilated to the target P(E)CO(2), and the LMA had to be replaced with tracheal tube.

CONCLUSION

In conclusion, PCV should be the preferred mode to provide positive pressure ventilatio (PPV), when using the size-1 cLMA in babies weighing 2.5-5 kg, in view of less gastric insufflation associated with it for surgeries of brief duration. More studies are required to validate the clinical significance of these two modes of ventilation in longer procedures, in this subpopulation.

Facemask pressure-controlled ventilation in children: what is the pressure limit?

BACKGROUND

In this study, we sought to determine the level of inspiratory pressures allowing adequate and safe ventilation without any risk of gastric insufflation (GI) in children according to age.

METHODS

One hundred children, aged 1 day to 16 years, ASA physical status I to II, scheduled for general anesthesia were studied prospectively. After induction of anesthesia, children's lungs were ventilated with pressure-controlled ventilation. The initial inspiratory pressure was 10 cm H(2)O and was increased by steps of 5 cm H(2)O, up to a maximum of 25 cm H(2)O. At each step, GI was detected by epigastric auscultation. The recorded data were age and weight. At each step, the inspiratory pressure, the respiratory rate, the expired tidal volume, the minute ventilation, and the occurrence of GI were also recorded.

RESULTS

GI occurred in 78 children. GI occurred in 95% of children younger than 1 year, in 93% of children aged 1 to 5 years, and 56% of children older than 5 years (P = 0.001). The pressure threshold at which GI occurred increased with age: the younger the child, the lower the GI pressure threshold. Tidal volume increased with inspiratory pressure, but at >15 cm H(2)O, tidal volume did not change significantly.

CONCLUSION

The inspiratory pressure threshold at which GI can occur depends on age. It is low in infants and increases with age. In most cases, proper ventilation without GI was obtained with an inspiratory pressure </=15 cm H(2)O. Increasing inspiratory pressure above this threshold results in an increase in GI and no change in tidal volume.

Insertion characteristics, sealing pressure and fiberoptic positioning of CobraPLA in children

BACKGROUND

The CobraPLA(TM) is a new supraglottic airway device designed for the use in spontaneously breathing and mechanically ventilated patients. In adults it has been found as effective as the LMA, but with better sealing qualities. The aim of the present study was to evaluate fit and sealing characteristics of CobraPLA size 1.5 and 2 in mechanically ventilated children.

METHODS

Forty children, ASA I/II, aged 1-10 years, weighing 10-35 kg were scheduled for minor surgical procedures. The number of attempts for insertion and fiberoptic positioning of the CobraPLA was assessed. After muscle relaxation had been achieved, airway sealing pressure was measured by gradually increasing maximum inspiratory pressure to a maximum of 30 cm H(2)O.

RESULTS

Insertion of CobraPLA was successful at the first attempt in 90% of patients. The vocal cords were visualized in 90% of patients (grade 0: 2.5%, grade 1: 7.5%, grade 2: 30%, grade 3: 15%, grade 4: 45%). Median sealing pressure was 20.0 +/- 6.0 cm H(2)O. In 21% of patients gastric insufflation was observed at a peak inspiratory pressure of 20 cm H(2)O or below.

CONCLUSIONS

The CobraPLA was found to have easy insertion characteristics and good anatomical fitting in children between 10 and 35 kg. If positive pressure ventilation with CobraPLA size 1.5 and 2.0 is required, peak inspiratory pressure should be kept below the leak pressure and the abdomen closely monitored for signs of gastric insufflation.

Pressure-controlled ventilation is superior to volume-controlled ventilation with a laryngeal mask airway in children

BACKGROUND

This prospective, randomized, crossover study had two purposes: first, to determine whether pressure-controlled ventilation (PCV) is safer than volume-controlled ventilation (VCV) by preventing gastric insufflation in children ventilated through an laryngeal mask airway (LMA); second, to assess whether the measurement of LMA leak pressure (P(leak)) is useful for preventing leakage during positive pressure ventilation (PPV).

METHODS

Forty-one, 2 to 15-year-old children underwent general anesthesia with an LMA. The expiratory valve was set at 30 cmH(2)O and P(leak) was measured using constant gas flow. Children were randomly ventilated using PCV or VCV for 5 min in order to reach a P(ET)CO(2) not exceeding 45 mm Hg, and then they were ventilated with the alternative mode. If the target P(ET)CO(2) could not be obtained in one mode, we switched to the other. If both modes failed, children were intubated. Tidal volumes, P(ET)CO(2) and airway pressures were noted and compared between modes. Gastric insufflation was checked by epigastric auscultation.

RESULTS

PCV provided more efficient ventilation than VCV, as targeted P(ET)CO(2) was obtained without gastric insufflation using PCV in all cases except one, whereas VCV failed in three cases. No gastric insufflation occurred when ventilating below peak.

CONCLUSIONS

These findings suggest that in the age group studied, PCV is more efficient than VCV for controlled ventilation with a laryngeal mask. Gastric insufflation did not occur with this mode.

Prospective, randomized comparison of laryngeal tube and laryngeal mask airway in pediatric patients

BACKGROUND

While reports of the use of laryngeal mask airway (LMA)-Classic in great patient numbers are available, data on the use of the laryngeal tube (LT) in this age group is limited. The two devices are compared in a prospective randomized trial to evaluate success rates and quality of airway seal.

METHODS

Sixty children, aged 2-8 years, scheduled for elective surgical interventions were randomized to be ventilated with LMA or LT. Standardized anesthesia was induced with fentanyl and propofol. Number of insertion attempts, time until first tidal volume and intraoperative tidal volumes, and peak pressures were recorded. Airway leak pressure was measured with cuff pressure adjusted to 60 cmH(2)O.

RESULTS

Demographic data were comparable, average age in the LMA/LT group was 5.2 +/- 1.9/5.3 +/- 1.9 years. Insertion was successful in 29 of 30 patients in the LMA group (second attempt 8) and in all patients in the LT group (second attempt 3). Time until first tidal volume for LMA/LT was 23.1 +/- 7.3/19.2 +/- 8.6 s (P < 0.05). Peak airway pressures for LMA and LT were 15.3 +/- 3.4 and 17.1 +/- 4.0 cmH(2)O (P < 0.05) with tidal volumes of 10.2 +/- 2.2 and 10.2 +/- 1.9 ml.kg(-1), airway leak pressure was 19.2 +/- 8.6 cmH(2)O for LMA and 26.3 +/- 7.3 cmH(2)O for LT (P < 0.001).

CONCLUSION

Insertion success rate is high with both LMA and LT in the age group studied. The airway leak pressure, serving as an estimate to judge quality of airway seal, is higher with the LT.

Les respirateurs d'anesthésie de nouvelle génération vont-ils modifier notre pratique chez l'enfant ?

Because of specific paediatric respiratory physiology (mainly decreased compliance and functional residual capacity, increased O2 demand and CO2 production), ventilators for paediatric anaesthesia need to be powerful and able to deliver small volumes at a high rate without compression volume loss. The compensation of compliance now available on every anaesthesia machine, compensates for the volume of gas lost by compression in the circuit tubing allowing the tidal volume to reach preset commands, even for bellow in box respirators. Preset tidal volume is then totally delivered to the lung by volume-controlled ventilation because it becomes independent of total pulmonary compliance and fresh gas flow. Increased precision of electronic flowmeters and better air-tightness of circuits allow reducing with precision fresh gas flow to values approaching children's O2 consumption and N2O diffusion. New modes of ventilation are now available on anaesthesia machine. Pressure controlled mode, by increasing and maintaining mean airway pressures, ameliorates intrapulmonary gas distribution and compensates for the gas leak from uncuffed tracheal tubes. Unsteady tidal volume resulting from variation of total compliance, is the main drawback of pressure-controlled ventilation that may be overcome by using the "autoflow" mode (better described as a pressure controlled mode ensuring tidal volume) available with one of the last generation of ventilators. Increased accuracy and security of the mode "pressure assist" might increase the use of spontaneous ventilation in paediatric anaesthesia even for low weight children. However tidal volume remains variable with compliance and depth of anaesthesia, which may require several adjustments of ventilator's settings. The clinical conditions (mainly airway control) of pressure assist use for children less than 10 kg should be elucidated before recommending its use.

Linear Model and Algorithm to Automatically Estimate the Pressure Limit of Pressure Controlled Ventilation for Delivering a Target Tidal Volume

OBJECTIVE

To theoretically assess the viability of an automatic procedure to support the anesthesiologist in properly setting mechanical ventilators when the operating conditions are switched from volume controlled to pressure controlled ventilation whilst maintaining the preset tidal volume. The procedure is based on a simple linear model of the ventilator breathing system with constant parameters and utilizes the signals gathered by the ventilator without the need to add further equipment. After a short period of stable volume controlled ventilation with the desired tidal volume, the herewith described algorithm allows the calculation of the value of pressure limit to set in pressure controlled mode which assures the previously settled tidal volume with the same breathing frequency and inspiratory-expiratory time ratio.

METHODS

The algorithm allows the online identification of the four parameters necessary for the mathematical model that are obtained by means of a direct comparison between the pressure, flow and volume waveforms generated by the model and the analog signals provided by the ventilator. The theoretical approach was validated by two different ventilators, various settings, two breathing circuits, endotracheal tubes of various sizes and two mechanical simulators of the respiratory system operating in various conditions.

RESULTS

Errors usually less than 5% (p < 0.05) on the target tidal volume were obtained for various settings typically used for adult ventilation in less than 10 s. The theoretical approach shows its limitations (errors of 10+/- 5%, p < 0.05) at high breathing frequencies (30-40 bpm) and low tidal volumes (200-300 ml).

CONCLUSIONS

The proposed theoretical approach shows the viability, for adult settings, of one of the simplest mathematical model for mechanical ventilation in order to quickly and safely switch from volume controlled to pressure controlled ventilation. The algorithm could easily be in perspective implemented in the software of the ventilator providing the anesthesiologist with an indication on the value of pressure limit to set in order to safely switch ventilation mode.

Einsatz der ProSeal®-Kehlkopfmaske der Größe 3 bei Kindern

BACKGROUND

The low-pressure airway seal of the Classic laryngeal mask airway (CLMA) can be inadequate for positive pressure ventilation (PPV) in children. The ProSeal laryngeal mask airway (PLMA) forms a more effective seal of the airway than the CLMA and facilitates gastric tube placement in adults. The size 3 PLMA can be used in adults and children.

METHODS

The CLMA and PLMA were studied in random order -- crossover -- in 30 anaesthetized, non-paralysed children (average age 10.6 years, average body weight 39 kg). Airway leak pressure, maximum tidal volume, ease of insertion, quality of initial airway and fiberoptic position were determined. Gastric tube placement was assessed for the PLMA.

RESULTS

The mean airway leak pressure in neutral head position (27.0 vs. 16.8 cm H(2)O), maximum flexion (38.3 vs. 26.2 cm H(2)O) and maximum extension (21.1 vs. 14.2 cm H(2)O) as well as the mean maximum tidal volume (1432 vs. 1062 ml) were significantly higher (p<0.001) for the PLMA. Air insufflation into the stomach occurred with the CLMA but not with the PLMA. Gastric tube placement was possible in all patients.

CONCLUSIONS

The high reliability of g-tube placement and the significantly increased airway leak pressure seem to make the size 3 PLMA a more suitable device for PPV in children than the same size CLMA.

The Size 1½ ProSeal™ Laryngeal Mask Airway in Infants: A Randomized, Crossover Investigation with the Classic™ Laryngeal Mask Airway

Many problems with the Classic laryngeal mask airway (CLMA) in infants are believed to be related to its inadequate cuff design. One of the main limitations of the CLMA is that the resulting low-pressure seal can be inadequate for positive pressure ventilation (PPV). The ProSeal LMA (PLMA), a new laryngeal mask airway with a modified cuff, has been shown to form a more effective seal than the CLMA in children. The first infant size PLMA, size 1(1/2), became available recently. We studied 30 anesthetized, nonparalyzed infants aged 15 mo (2-30 mo) and weighing 9 kg (5-12 kg). The CLMA and PLMA were inserted in random order into each patient. Airway leak pressure and maximum tidal volume were measured. Ease of insertion, quality of initial airway, and fiberoptic position were also determined. Gastric tube placement was assessed for the PLMA. The mean airway leak pressure in neutral head position (26.7 versus 18.9 cm H2O), maximum flexion (35.6 versus 28.2 cm H2O), and the mean maximum tidal volume (312 versus 260 mL) were significantly higher for the PLMA (P < 0.01). Air entered the stomach in eight patients with the CLMA but did not with the PLMA. Gastric tube placement was possible in all but one patient. In three patients, the use of the PLMA led to some degree of clinically relevant compression of the larynx. The size 1(1/2) PLMA seems to be a more suitable device for airway maintenance in infants than the same size CLMA. The ability to insert a gastric tube at the same time, and a significantly higher airway leak pressure than with the CLMA, may have important implications for its use for PPV in infants.

Comparison of cuffed, uncuffed tracheal tubes and laryngeal mask airways in low flow pressure controlled ventilation in children

BACKGROUND

The use of low flow circle systems necessitates a 'leak free' breathing system which is commonly achieved by using a cuffed tracheal tube (TT). We hypothesized that low flow circle system anesthesia can equally effectively be achieved by using the LMA in pediatric anesthesia.

METHODS

Following local ethics committee approval we randomly recruited 45 patients scheduled for elective surgery and requiring mechanical ventilation into three groups (cuffed TT, uncuffed TT and LMA group, n = 15). The size of the TT was determined by means of the formula (age/4) + 4.5 for uncuffed and (age/4) + 4 for cuffed TT whereas the size of the LMA size was dependent on weight. Following induction of anesthesia and muscle paralysis patients were ventilated with pressure controlled ventilation through a pediatric circle system and the lowest fresh gas flow (FGF) determined.

RESULTS

The FGF achieved were (median and range) 0.20 (0.2-0.25) l.min(-1) for the LMA group, 0.20 (0.2-0.4) l.min(-1) for the cuffed TT group and 1.15 (0.2-4.75) l.min(-1) for the uncuffed group. The differences between the LMA and cuffed TT compared with the uncuffed TT were significant (P < 0.0001 and P = 0.0002, respectively). The difference in FGF between LMA and cuffed TT was not significant.

CONCLUSION

We conclude that pressure controlled ventilation using an LMA is an alternative to a cuffed TT during low flow circle system anesthesia in children. Low FGF is unlikely to be achieved consistently using an uncuffed TT because of a substantial leak.

A randomized crossover comparison of the size 2 1/2 laryngeal mask airway ProSeal versus laryngeal mask airway-Classic in pediatric patients

The laryngeal mask airway (LMA)-ProSeal (P-LMA) forms a more effective seal than the LMA-Classic (C-LMA) and facilitates gastric tube (g-tube) placement in adults. The first pediatric sizes of P-LMA recently became available. In 30 anesthetized, nonparalyzed children, aged 7.7 +/- 2 yr and weighing 27 (20-35) kg, we inserted the size (1/2) P-LMA and C-LMA in random order. Ease of insertion, quality of initial airway, fiberoptic position, airway leak pressure, and maximum tidal volume were determined. G-tube placement was assessed for the P-LMA. Ease of insertion was similar for both devices. The quality of the initial airway was better for the P-LMA (P = 0.01). Airway leak pressure in neutral head position (22.6 versus 18.5 mbar; P = 0.003), maximum flexion (37 versus 26.3 mbar; P < 0.001), maximum extension (15.2 versus 13 mbar; P = 0.045), and maximum tidal volume (1088 versus 949 mL; P = 0.002) were significantly better for the P-LMA. Air entry into the stomach occurred with the C-LMA but not with the P-LMA (P = 0.014). G-tube placement was possible in all patients. The reliability of g-tube placement and the significantly increased airway leak pressure found in this investigation might have important implications for use of the size (1/2) P-LMA for positive pressure ventilation in children.

Size 2 ProSeal™ laryngeal mask airway: a randomized, crossover investigation with the standard laryngeal mask airway in paediatric patients

BACKGROUND

One of the main concerns with the use of the standard laryngeal mask airway (SLMA) in small infants is that its low-pressure seal might be inadequate for positive pressure ventilation so that there is a risk of gas leakage into the stomach with the subsequent risk of regurgitation. The new ProSeal LMA (PLMA) has been shown to form a more effective seal than the SLMA and to facilitate gastric tube placement in adults. The first paediatric size PLMA became available recently.

METHODS

Thirty anaesthetized, non-paralysed children aged 46 (19) months, weighing 16 (10-21) kg, were studied. The SLMA and PLMA were inserted in random order into each patient. Airway leak pressure and maximum tidal volume were measured. Ease of insertion, quality of initial airway and fibreoptic position were also determined. Gastric tube placement was assessed for the PLMA.

RESULTS

The airway leak pressure and maximum tidal volume were significantly higher for the PLMA (P=0.001). Ease of insertion and quality of initial airway were similar for both devices. Air entry into the stomach occurred more frequently with the SLMA (P=0.005). Gastric tube placement was possible in all patients.

CONCLUSIONS

The size 2 PLMA offered some advantages over the same size of SLMA in this crossover investigation. The high reliability of gastric tube placement and the significantly increased airway leak pressure might have important implications for use of this device for positive pressure ventilation in infants.

The ProSeal laryngeal mask airway in children

BACKGROUND

The ProSeal (PLMA) is a new laryngeal mask device with a modified cuff to improve the seal and a drain tube to provide access to the gastrointestinal tract. We assessed the performance of the size 2 (which has no dorsal cuff) and size 3 (which has a dorsal cuff) in terms of insertion success, efficacy of seal, tidal volume, gas exchange, fiberoptic position, gastric tube placement and frequency of problems.

METHODS

Eighty children undergoing minor surgery were studied (n = 40, size 2 PLMA, weight 10-25 kg; n = 40, size 3 PLMA, weight >25-50 kg). Induction was with remifentanil and propofol. Insertion was with the introducer tool and by experienced users. Maintenance was with propofol or sevoflurane and pressure controlled ventilation.

RESULTS

The first-time and overall insertion success rate was 84 and 100%, respectively. Oropharyngeal leak pressure was 31 +/- 5 cmH2O. There were no gastric or drain tube air leaks. Tidal volume and gas exchange was adequate in all patients, other than two brief episodes of hypoxia because of airway reflex activation. The vocal cords and epiglottis were visible in 99 and 80%, respectively, via the airway tube. The first-time and overall insertion success rate for gastric tube insertion was 87 and 100%, respectively. During maintenance, the PLMA was removed in one patient with airway reflex activation and another required epinephrine for bronchospasm. There were no differences in performance between the sizes 2 and 3 PLMA.

CONCLUSION

The PLMA is an effective airway device in children and isolates the glottis from the esophagus when correctly positioned. Despite the lack of a dorsal cuff, the performance of the size 2 was similar to the size 3 PLMA in the age groups tested.

[Laryngeal mask airway in paediatrics: when? How?]

Since its introduction in 1981 by Brain, the laryngeal mask airway has achieved increased popularity in pediatrics. Despite widespread use, the definitive role of the laryngeal mask airway has yet to be established. We attempt to clarify the role of the laryngeal mask airway in airway management during anaesthesia by discussing the advantages and disadvantages as well as the indications and contra-indications of its use. The use in failed or suspected difficult endotracheal intubation was also described. Finally, we review the techniques of insertion, details of misplacement, the removal and complication associated with the use of laryngeal mask airway. Cleaning, pre-use checking and maintenance were also discussed.

A comparison of the laryngeal mask airway ProSeal and the laryngeal tube airway in paralyzed anesthetized adult patients undergoing pressure-controlled ventilation

We compared the laryngeal mask airway ProSeal (PLMA) and the laryngeal tube airway (LTA), two new extraglottic airway devices, with respect to: 1) insertion success rates and times, 2) efficacy of seal, 3) ventilatory variables during pressure-controlled ventilation, 4) tidal volume in different head/neck positions, and 5) airway interventional requirements. One-hundred-twenty paralyzed anesthetized ASA physical status I and II adult patients were randomly allocated to the PLMA or LTA for airway management. A standardized anesthesia protocol was followed by two anesthesiologists experienced with both devices. The criteria for an effective airway included a minimal expired tidal volume of 6 mL/kg during pressure-controlled ventilation at 17 cm H(2)O with no oropharyngeal leak or gastric insufflation. First attempt success rates at achieving an effective airway were similar (PLMA: 85%; LTA: 87%), but after 3 attempts, success was more frequent for the PLMA (100% versus 92%, P = 0.02). Effective airway time was similar. Oropharyngeal leak pressure was larger for PLMA at 50% maximal recommended cuff volume (29 +/- 7 versus 21 +/- 6 cm H(2)O, P < 0.0001), but was similar at the maximal recommended cuff volume (33 +/- 7 versus 31 +/- 8 cm H(2)O). Tidal volumes (614 +/- 173 versus 456 +/- 207 mL, P < 0.0001) were larger and ETCO(2) (33 +/- 9 versus 40 +/- 11 mm Hg, P = 0.0001) lower for the PLMA. The number of airway interventions was significantly less frequent for the PLMA. Airway obstruction was more common with the LTA. When comparing mean tidal volumes in different head/neck positions, the quality of airway was unchanged in 56 of 60 patients (93%) with the PLMA and 42 of 55 (76%) with the LTA (P = 0.01). The PLMA offers advantages over the LTA in most technical aspects of airway management in paralyzed patients undergoing pressure-controlled ventilation.

IMPLICATIONS

The laryngeal mask airway ProSeal offers advantages over the laryngeal tube airway in most technical aspects of airway management in paralyzed patients undergoing pressure-controlled ventilation.

Management of the paediatric airway: new developments

During the last 2 years, some interesting new devices have been made available to improve airway management in children and infants, and several studies have advanced our understanding concerning risks and benefits of the current practice in the field. Certain risk factors for airway related problems during anaesthesia in children having a cold have been identified, and new aspects of the controversy concerning the use of cuffed endotracheal tubes in children presented. Novel video-assisted systems have been introduced for the management of the difficult airway in paediatric patients, and new applications for well known devices have been suggested, such as the laryngeal mask airway serving as guidance for fibreoptic intubation. Recent studies also demonstrated specific problems with the laryngeal mask airway in infants, as well as the advantages of a new prototypic laryngeal mask airway for children, similar to the ProSeal (LMA International S.A. Group, USA). Furthermore, the following review presents new data about the use of the cuffed oropharyngeal airway, the laryngeal tube, and the Arndt bronchus blocker in paediatric patients.