Neonatal Intensive Care

Effects of Synchronized Intermittent Mandatory Ventilation Versus Pressure Support Plus Volume Guarantee Ventilation in the Weaning Phase of Preterm Infants* Aydin Erdemir, MD; Zelal Kahramaner, MD; Ebru Turkoglu, MD; Hese Cosar, MD; Sumer Sutcuoglu, MD; Esra Arun Ozer, MD

Objective: To compare the effects and short-term outcomes of pressure support ventilation with volume guarantee versus synchronized intermittent mandatory ventilation in the weaning phase of very low–birth weight infants with respiratory distress syndrome. Design: Randomized controlled prospective study. Setting: Tertiary care neonatal unit. Patients: A total of 60 premature infants who were less than 33 weeks’ gestation and/or less than 1,500 g birth weight and received mechanical ventilation because of respiratory distress syndrome were studied. Interventions: All infants were ventilated from the time of admission with synchronized intermittent positive pressure ventilation mode after surfactant treatment for respiratory distress syndrome and then switched to pressure support ventilation with volume guarantee or synchronized intermittent mandatory ventilation mode in the weaning phase. The ventilatory variables and neonatal outcomes were recorded in each group. Measurements and Main Results: The mean peak inflation pressure was higher in synchronized intermittent mandatory ventilation group (p < 0.001) and the mean airway pressure was higher in pressure support ventilation with volume guarantee group (p = 0.03), whereas mean tidal volume and respiratory rates were similar in both groups. The prevalence of postextubation atelectasis was higher in synchronized intermittent mandatory ventilation group, but the difference was not statistically significant (p = 0.08). No differences were found in the prevalence of reintubation, patent ductus arteriosus, intraventricular hemorrhage, retinopathy of prematurity, bronchopulmonary dysplasia, and pneumothorax between the groups. *See also p. 272. All authors: Tepecik Education and Research Hospital, Department of Pediatrics, Neonatology Clinic, Yenisehir, Izmir, Turkey. The authors have disclosed that they do not have any potential conflicts of interest. For information regarding this article, E-mail: [email protected] Copyright © 2014 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies DOI: 10.1097/PCC.0b013e3182a5570e 236

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Conclusions: Pressure support ventilation with volume guarantee mode may be a safe and feasible mode during the weaning phase of very low–birth weight infants on mechanical ventilation support for respiratory distress syndrome with respect to reducing the frequency of postextubation atelectasis and using less peak inflation pressure. (Pediatr Crit Care Med 2014; 15:236–241) Key Words: mechanical ventilation; premature infant; pressure support ventilation; respiratory distress syndrome; synchronized intermittent mandatory ventilation; volume guarantee ventilation

R

espiratory distress syndrome (RDS) is one of the most common causes of mortality and morbidity in preterm neonates and is characterized by surfactant deficiency and structural immaturity in the lungs. Main treatments for RDS include mechanical ventilation and exogenous surfactant therapy (1). The goal in respiratory support is using the appropriate method of ventilation that minimizes lung injury. Recently, despite the development of many new ventilation methods, limited clinical data are available to evaluate their effectiveness. Pressure-limited or volume guarantee (VG) mode can be used in mechanical ventilation. The most widely used modality of pressure-limited ventilation is synchronized intermittent mandatory ventilation (SIMV). During SIMV, a constant peak inflation pressure (PIP) (2) regardless of the tidal volume (VT) is chosen; therefore, if ventilator settings are not weaned rapidly during the changes in respiratory effort, lung compliance, and airway resistance, lung injury may happen due to underventilation or overventilation (3). It is now clear that volume is more important contributor rather than pressure to ventilator-induced lung injury (4). In VG mode, the ventilator automatically sets the PIP according to changes in pulmonary mechanics to achieve the target VT. Pressure support ventilation (PSV) is a pressurelimited flow-cycled mode, which synchronizes the beginning of inspiration, terminates each breath, and allows expiration when March 2013 • Volume 15 • Number 3

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inspiratory flow declines to a preset threshold. Therefore, the onset, rate, and end of the breath are dependent on the infant (5). We thought that a combination of PSV with VG (PSV + VG) may provide an optimal synchrony between the infant and ventilator and reduce ventilator-associated lung injury. In this study, we aimed to compare the effects and short-term outcomes of PSV + VG versus SIMV in the weaning phase of very low–birth weight infants with RDS.

MATERIALS AND METHODS Study Population This randomized controlled prospective study was conducted at the Neonatology Clinic of Tepecik Education and Research Hospital, Izmir, Turkey, between January 2010 and January 2012. A total of 60 premature infants who were less than 33 weeks’ gestation and/or less than 1,500 g birth weight and received mechanical ventilation because of RDS were studied. All infants were diagnosed with RDS on the basis of radiologic and clinical findings. Exclusion criteria were admission after 6 hours of age; those with congenital cardiac, respiratory, or CNS malformations; congenital metabolic diseases; congenital pneumonia; sepsis; perinatal asphyxia; and leak less than 20% around the endotracheal tube. This study was approved by Ethics Committee of Izmir Tepecik Education and Research Hospital, and informed consent was obtained from all parents before study entry. Study Design After the criteria for entry into the study were fulfilled, infants were randomized to either PSV + VG group or SIMV group using sealed envelope randomization. After surfactant administration (Survanta, 100 mg/kg), all infants were ventilated from the time of admission by a Babylog 8000 plus ventilator (Drager Medical, Drager and Siemens Company, Lubeck, Germany) with synchronized intermittent positive pressure ventilation (SIPPV) mode. PIP was set at the minimal level that maintains target blood gas analysis (Pco2, 40–50 mm Hg; pH, 7.25–7.40). Inspiratory time (IT) and positive end-expiratory pressure (PEEP) were set at 0.4 seconds and 4 cm H2O, respectively. Fio2 was given as needed to achieve Sao2 between 88% and 93% by pulse oximetry. Repeated doses of intratracheal surfactant were administered if the oxygen requirements were higher than 40%. The infants were switched to SIMV or PSV + VG in the weaning phase when Fio2 was less than 0.4, respiratory rate (RR) was less than 60 mechanical breaths, PIP was 16 cm H2O, and PEEP was of 4 cm H2O with target blood gas analysis. Ventilator Management In the weaning phase, the infant was placed on the chosen mode of ventilation. The ventilatory variables were adjusted as follows: PIP, 16 cm H2O; PEEP, 4 cm H2O; IT, 0.4 seconds; and rate, 40 breaths in the SIMV mode. In the PSV + VG mode, the VT was set at 5 mL/kg, maximum IT was set at 0.5 seconds, and the PIP limit was set at 15–20% above the average PIP needed to achieve the target VT. Capillary blood gases were measured at admission and then at 4-hour intervals or more often as Pediatric Critical Care Medicine

needed. After each targeted capillary blood gases, the rate was reduced in a stepwise fashion with a prolonged expiratory time (1, 2, 3, and 5 s) in the SIMV mode and the VT was reduced by increments of 0.5 mL/kg in the PSV + VG mode. The infants who tolerated an expiratory time of 5 seconds in the SIMV mode and a VT of 3 mL/kg in PSV + VG mode with a target blood gas analysis, mean airway pressure (MAP) less than 7 cm H2O, and no tachypnea were extubated to nasal continuous positive airway pressure (CPAP). Prior to extubation, IV aminophylline was administered to all patients to prevent apnea and reintubation according to clinical protocol. Data Acquisition The variables VT, MAP, and PIP were recorded continuously at 10-second intervals using proprietary software called Babyview1 (Draeger, Lubeck, Germany). The data were then exported into a spreadsheet (Microsoft Excel, Microsoft, Redmond, WA) for analysis. The data were averaged over SIPPV phase, entire weaning phase, and 30-minute periods of starting and final weaning phase, and the mean values were compared between the groups. Clinical data including gestational age, birth weight, gender, delivery mode, use of antenatal corticosteroids, presence of patent ductus arteriosus (PDA) requiring treatment, intraventricular hemorrhage (IVH), retinopathy of prematurity (stage 2, ROP), bronchopulmonary dysplasia (BPD) (oxygen dependency at 36 weeks of postmenstrual age), air dissection (pulmonary interstitial emphysema, pneumothorax, or pneumomediastinum), postextubation atelectasis (developing new atelectasis within 48 hours after extubation, no air bronchogram in the atelectatic lung field on chest radiograph, and clinically deterioration related to this), reintubation, duration of hospitalization, mortality, and dose of surfactant were collected from the patients’ chart records. Duration of ventilation, time in SIPPV, weaning phase, and nasal CPAP were also recorded. Statistical Analysis Statistical analysis was performed using the Statistical Package of Social Science (SPSS), Version 15.0 (SPSS, Chicago, IL). Data were expressed as mean ± sd. Student t test and MannWhitney U test were used for comparing mean values. Chisquare test was used for comparing proportions. A p value of less than 0.05 was considered statistically significant.

RESULTS Sixty preterm infants requiring mechanical ventilation for RDS were included in the study. After surfactant administration, all infants were initially ventilated using SIPPV mode, and for the weaning phase, a total of 30 infants were randomized to the SIMV group and 30 infants to the PSV + VG group. No significant differences were observed between the two groups in terms of the birth weight, gestational age, gender, multiple pregnancy, delivery mode, antenatal glucocorticoid treatment, and small for gestational age (p > 0.05) (Table 1). Duration www.pccmjournal.org

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Table 1.

Demographic Characteristics of Groups Synchronized Intermittent Mandatory Ventilation (n = 30)

Pressure Support Ventilation With Volume Guarantee (n = 30)

p

28.2 ± 2.0

28.2 ± 2.8

0.95

1,069 ± 299

1,139 ± 410

0.45

Gender (male/female)

17/13

17/13

1

Delivery mode (vaginal/ cesarean)

10/20

11/19

0.78

Multiple pregnancy

4/30

7/30

0.31

Antenatal corticosteroids

6/30

6/30

1

Small for gestational age

1/30

2/30

0.55

Variable

Gestational age (wk)a Birth weight (g)

a

Values are presented as mean ± sd.

a

of hospitalization was not significantly different between the two groups (p > 0.05). Mortality was higher in SIMV group, but this difference was not statistically significant (p = 0.41). The mean doses of repeated surfactant instillations in SIMV group and in PSV + VG group were 1.4 ± 0.8 and 1.2 ± 0.5 times, respectively. The requirement for repeated surfactant instillations was not significantly different between the two groups (p > 0.05). The ventilatory variables of both groups are summarized in Table 2. The mean time in SIPPV, weaning phase, and the mean extubation time were higher in the SIMV group, but the difference was not statistically significant (p > 0.05). During SIPPV, the mean PIP, MAP, VT, and RRs of both groups did not differ significantly. During weaning phase, mean PIP was higher in SIMV group (Fig. 1) (p < 0.001) and mean MAP was higher in PSV + VG group (Fig. 2) (p = 0.03), whereas mean VT and RRs were similar in both groups. The prevalence of postextubation atelectasis was higher in SIMV group, but the difference was not statistically significant (p = 0.08). No differences were observed in the prevalence of reintubation, PDA, IVH, ROP, BPD, and pneumothorax between the groups (Table 3). Three infants had postextubation atelectasis in SIMV group, whereas no infant had postextubation atelectasis in PSV + VG group. No differences were observed in the prevalence of reintubation, PDA, IVH, ROP, and BPD between the groups.

DISCUSSION After advances in the perinatal management, particularly antenatal corticosteroid therapy, RDS is now more prevalent among premature infants and contributes to morbidity and mortality (6). The standard treatment for this condition is endotracheal intubation, mechanical ventilation, and exogenous surfactant therapy (1). Mechanical ventilation is life saving, but it may induce lung injury and contribute to the development of BPD with inappropriate inspiratory pressure and VT (7). There is no clear consensus on which ventilation mode is superior in both initial and weaning phase of ventilatory 238

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treatment of infants with RDS (8). Pressure-limited timecycled ventilation modes, such as SIMV, are routinely used in neonates due to its ease of use and safety. Fixed PIP regardless of changes in patient functional residual capacity, compliance, RR, resistance, and fixed IT regardless of patient respiration are the disadvantages of pressure-limited modes because they cause inconsistent VT and asynchrony with the patient (9, 10). It is now clear that volume is an important contributor to ventilator-induced lung injury and chronic lung disease and so that there is a growing interest to VG ventilation (4, 10). Volume-targeted ventilation achieves a target VT by using the lowest PIP and is recommended as a safe weaning mode. Despite changes in compliance, consistent VT avoids excessive ventilation and lung injury in volume-targeted ventilation (11). PSV allows the infant to control the onset, duration, and frequency of the ventilation (5). Combining these two modes may minimize ventilator-induced injury and provide more synchrony for the infant. In this trial, we compared the effect of SIMV and PSV + VG modes on extubation and neonatal prognosis in the weaning phase of the 60 preterm infants with RDS. We found that the mean PIP was statistically lower and the mean MAP was statistically higher in PSV + VG group. Although the duration of ventilation and the mean extubation time were found shorter in PSV + VG group, this difference was not statistically significant. Also neonatal outcomes such as BPD and IVH did not differ significantly between the two groups. VG ventilation can be combined with pressure-limited ventilation modes, such as assist/control (A/C), SIMV, and PSV. Scopesi et al (12) compared SIPPV + VG, SIMV + VG, and PSV + VG modes in the weaning phase of RDS, and they found lower PIP, RR, and more stable VT in SIPPV + VG and PSV + VG groups compared with SIMV + VG group. Cheema and Ahluwalia (13) compared SIMV with SIMV plus VG in a randomized study in preterm infants with RDS. They found lower PIP and MAP in SIMV + VG group. Similar to these studies, we found statistically lower PIP in PSV + VG group. In this study, there was no difference in mean VT between the groups, but it would be much more meaningful to have data on SIMV March 2014 • Volume 15 • Number 3

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Table 2.

Ventilatory Variables Synchronized Intermittent Mandatory Ventilation (n = 30)

Pressure Support Ventilation With Volume Guarantee (n = 30)

p

7.8 ± 9.8

4.4 ± 4.4

0.09

32.4 ± 35.5

21.1 ± 23.5

0.15

40.4 ± 44

25.2 ± 24.4

0.1

  PIP (cm H2O)

15.7 ± 1.8

16.1 ± 1.7

0.36

  MAP (cm H2O)

9.2 ± 1.5

8.8 ± 1.1

0.23

 VT (mL/kg)

4.8 ± 0.8

4.8 ± 1.6

0.97

66.7 ± 7.9

65.6 ± 8.1

0.59

  PIP (cm H2O)

14.8 ± 1.0

11.1 ± 2.9

< 0.001b

  MAP (cm H2O)

5.3 ± 0.8

5.7 ± 0.8

0.03a

 VT (mL/kg)

3.9 ± 0.9

4.3 ± 0.6

0.1

66.5 ± 12.9

67.1 ± 13.5

0.85

  PIP (cm H2O)

14.6 ± 1.3

13.8 ± 4.0

0.26

  MAP (cm H2O)

5.9 ± 1.0

6.3 ± 1.0

0.16

4.2 ± 1.2

4.3 ± 1.0

0.79

64.2 ± 14.3

66.7 ± 18.1

0.56

  PIP (cm H2O)

14.5 ± 1.5

9.1 ± 3.4

< 0.001b

  MAP (cm H2O)

4.7 ± 1.0

5.3 ± 1.1

0.03a

4.1 ± 1.3

3.8 ± 0.9

0.41

67.0 ± 15.3

68.0 ± 14.9

0.79

Variable

Time in SIPPV (hr)a Duration of weaning period (hr)

a

Extubation time (hr)

a

SIPPV variables (before the weaning period)

a

  Respiratory rate (breaths/min) Weaning variables (entire weaning period)

a

  Respiratory rate (breaths/min)b Weaning variables (starting values)a

 VT (mL/kg)   Respiratory rate (breaths/min)

b

Weaning variables (final values)

a

 VT (mL/kg)   Respiratory rate (breaths/min)

b

SIPPV = synchronized intermittent positive pressure ventilation, PIP = peak inflation pressure, MAP = mean airway pressure. a Values are presented as mean ± sd. b Ventilator cycling frequency in pressure support ventilation, spontaneous breathing rate of the infant in synchronized intermittent mandatory ventilation.

mechanical inflations alone rather than averaging all breaths. The SIMV inflations are typically about 33% larger than those seen in modes that support every breath (A/C or PSV) while the spontaneous breaths are often only 2–3 mL/kg (14). Lista et al (15) have demonstrated that the level of proinflammatory cytokines including interleukin (IL)-6 and IL-8 playing a role in the development of chronic lung disease were lower in PSV + VG than in PSV-alone group in preterm infants with RDS. Significantly lower PIP and MAP with the constant VT was found in the same study. Similar studies have reported a significant reduction in PIP and MAP with combination of PSV and VG modes (13, 15–17). In short-term studies, constant VT, lower PIP, and less hypocarbia were found with VG ventilation; however, no advantage was observed with PSV + VG when compared with SIMV in infants with acute phase of RDS after surfactant treatment (15, 18). Similarly, Nafday et al (5) compared SIMV and PSV Pediatric Critical Care Medicine

+ VG in infants with early stage of RDS, and they found no difference between the groups except reduction in the number of blood gas analysis in PSV + VG group. In the same study, lower MAP was found in SIMV group, as well as in our study. MAP was higher in PSV + VG because every patient breath was supported; therefore, there were many more inflations with shorter expiratory time. We used a target VT of 5 mL/kg in PSV + VG group in our study. Although there is no consensus and enough study for relevant target VT, Lista et al (15) demonstrated that the release of proinflammatory cytokines increased with low VT. Also Patel et al (19) showed increased work of breathing in low VT (4 mL/kg) as compared with high VT (6 mL/kg). Similar studies reported that using high VT (5–6 mL/kg) is more appropriate in the acute phase of RDS (17, 20). Abd El-Moneim et al (21) compared PSV + VG with SIMV during weaning in premature infants, and they found lower www.pccmjournal.org

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Figure 1. Mean peak inflation pressure (PIP) in synchronized intermittent mandatory ventilation (SIMV) and pressure support ventilation with volume guarantee (PSV + VG) groups.

Figure 2. Mean airway pressure (MAP) in synchronized intermittent mandatory ventilation (SIMV) and pressure support ventilation with volume guarantee (PSV + VG) groups.

Table 3.

ventilatory pressures and better synchrony between the patient and ventilator in PSV + VG mode. However, some infants were switched from PSV + VG to the SIMV mode due to temporary hyperventilation in this study, and they reported that hyperventilation should be considered with PSV + VG mode. Keszler and Abubakar (20) reported that VG provided constant VT but did not eliminate hypocarbia completely. Cheema et al (22) compared SIPPV and SIPPV + VG in the treatment of preterm infants with RDS and showed less hypocarbia in SIPPV + VG mode. In our study, we did not compare the groups in terms of hypocarbia, but lower PIP in PSV + VG can be explained by reduction in support of mechanical ventilation because of hypocarbia. Sinha et al (23) compared pressure-limited and VG ventilation in the treatment of RDS and found lower prevalence of IVH and BPD with VG ventilation. Similarly, Singh et al (24) found less BPD in VG ventilation, whereas no difference was observed in the prevalence of necrotizing enterocolitis (NEC), PDA, IVH, and periventricular leukomalacia between the groups. A meta-analysis comparing pressure-limited and VG ventilation showed less pneumothorax and grade 3–4 IVH with VG ventilation (25). The prevalence of BPD was found lower in VG ventilation in this meta-analysis, but the difference was not statistically significant. Nafday et al (5) reported that complications such as air dissection, NEC, PDA, severe IVH, and ROP did not differ between the PSV + VG and SIMV modes. In our study, the prevalence of postextubation atelectasis and pneumothorax were higher in SIMV group, but the difference was not statistically significant, and in accordance with the literature, no differences were observed in the neonatal complications, such as PDA, IVH, ROP, BPD, and mortality between the groups. The reason for the smaller risk of atelectasis in PSV + VG mode may be due to higher actual PEEP, which can explain the higher MAP in PSV + VG group. Studies comparing pressure-limited and VG ventilation had insufficient data about long-term neurodevelopmental outcomes of the infants, which is the limitation of our study. The other drawbacks of this study include small sample size and subjectivity in how ventilators were set up and managed

Neonatal Outcomes in the Two Groups Synchronized Intermittent Mandatory Ventilation (n = 30)

Variable

Pressure Support Ventilation With Volume Guarantee (n = 30)

p

Intraventricular hemorrhage

8/30

6/30

0.64

Retinopathy of prematurity

3/30

4/30

0.28

Bronchopulmonary dysplasia

9/30

9/30

0.91

13/30

14/30

0.79

5/30

1/30

0.08

Reintubation

11/30

12/30

0.82

Patent ductus arteriosus

15/30

12/30

0.43

2/30

0/30

0.15

Bronchopulmonary dysplasia or death Postextubation atelectasis

Pneumothorax 240

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(the weaning of target VT to 3 mL/kg could result in the infant receiving only endotracheal CPAP or the PEEP setting at 4 cm H2O could not support the “open lung concept”). The benefits of VG should be greater in the acute phase of RDS rather than the weaning phase due to rapid changes in lung compliance. Measuring the capillary blood gases instead of arterial blood gases, the data acquisition via Babyview which could not differentiate mechanical inflation or spontaneous breath and retrospectively recorded data rather than prospectively diminished confidence in the accuracy of the data.

CONCLUSION Our results suggest that PSV + VG mode may be a safe and feasible mode during the weaning phase of very low–birth weight infants on mechanical ventilation support for RDS with respect to reducing the frequency of postextubation atelectasis and using less PIP although more clinical trials are needed to investigate the optimum method of mechanical ventilation.

REFERENCES

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9. Dreyfuss D, Sauman G: Role of tidal volume, FRC, and end-inspiratory volume in the development of pulmonary edema following mechanical ventilation. Am J Respir Dis 1993; 148:1194–1203 10. Dreyfuss D, Saumon G: Ventilator-induced lung injury: Lessons from experimental studies. Am J Respir Crit Care Med 1998; 157:294–323 11. Keszler M, Abubakar KM: Volume guarantee ventilation. Clin Perinatol 2007; 34:107–116 12. Scopesi F, Calevo MG, Rolfe P, et al: Volume targeted ventilation (volume guarantee) in the weaning phase of premature newborn infants. Pediatr Pulmonol 2007; 42:864–870 13. Cheema IU, Ahluwalia JS: Feasibility of tidal volume-guided ventilation in newborn infants: A randomized, crossover trial using the volume guarantee modality. Pediatrics 2001; 107:1323–1328 14. Osorio W, Claure N, D’Ugard C, et al: Effects of pressure support during an acute reduction of synchronized intermittent mandatory ventilation in preterm infants. J Perinatol 2005; 25:412–416 15. Lista G, Marangione P, Azzali A, et al: The “guaranteed volume” in pressure support ventilation reduces the risk of barotrauma in premature children with severe respiratory syndrome. Acta Biomed Ateneo Parmense 2000; 71(Suppl 1):453–456 16. Bernstein G, Mannino FL, Heldt GP, et al: Randomized multicenter trial comparing synchronized and conventional intermittent mandatory ventilation in neonates. J Pediatr 1996; 128:453–463 17. Abubakar KM, Keszler M: Patient-ventilator interactions in new modes of patient-triggered ventilation. Pediatr Pulmonol 2001; 32:71–75 18. Olsen SL, Thibeault DW, Truog WE: Crossover trial comparing pressure support with synchronized intermittent mandatory ventilation. J Perinatol 2002; 22:461–466 19. Patel DS, Sharma A, Prendergast M, et al: Work of breathing and different levels of volume-targeted ventilation. Pediatrics 2009; 123:679–684 20. Keszler M, Abubakar K: Volume guarantee: Stability of tidal volume and incidence of hypocarbia. Pediatr Pulmonol 2004; 38:240–245 21. Abd El-Moneim ES, Fuerste HO, Krueger M, et al: Pressure support ventilation combined with volume guarantee versus synchronized intermittent mandatory ventilation: A pilot crossover trial in premature infants in their weaning phase. Pediatr Crit Care Med 2005; 6:286–292 22. Cheema IU, Sinha AK, Kempley ST, et al: Impact of volume guarantee ventilation on arterial carbon dioxide tension in newborn infants: A randomised controlled trial. Early Hum Dev 2007; 83:183–189 23. Sinha SK, Donn SM, Gavey J, et al: Randomised trial of volume controlled versus time cycled, pressure limited ventilation in preterm infants with respiratory distress syndrome. Arch Dis Child Fetal Neonatal Ed 1997; 77:202–205 24. Singh J, Sinha SK, Clarke P, et al: Mechanical ventilation of very low birth weight infants: Is volume or pressure a better target variable? J Pediatr 2006; 149:308–313 25. Wheeler K, Klingenberg C, McCallion N, et al: Volume-targeted versus pressure-limited ventilation in the neonate. Cochrane Database Sys Rev 2010; 11:CD003666

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Effects of synchronized intermittent mandatory ventilation versus pressure support plus volume guarantee ventilation in the weaning phase of preterm infants*.

To compare the effects and short-term outcomes of pressure support ventilation with volume guarantee versus synchronized intermittent mandatory ventil...
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