Volume-targeted ventilation and arterial carbon dioxide in neonates

OBJECTIVES: To review the arterial carbon dioxide tensions (PaCO(2)) in newborn infants ventilated using synchronized intermittent mandatory ventilation (SIMV) in volume guarantee mode (using the Dr?ger Babylog 8000+) with a unit policy targeting tidal volumes of approximately 4 mL/kg. METHODS: Data on ventilator settings and arterial PaCO(2) levels were collected on all arterial blood gases (ABG; n = 288) from 50 neonates (<33 weeks gestational age) ventilated using the Dr?ger Babylog 8000+ ventilator (Dr?ger Medizintechnik GmbH, Lübeck, Germany) in SIMV plus volume guarantee mode. Data were analysed for all blood gases done on the entire cohort in the first 48 h of life and a subanalysis was done on the first gas for each infant (n = 38) ventilated using volume guarantee from admission to the nursery. The number of ABG showing severe hypocapnoea (PaCO(2) < 25 mmHg) and/or severe hypercapnoea (PaCO(2) > 65 mmHg) were determined. RESULTS: The mean (SD) PaCO(2) during the first 48 h was 46.6 (9.0) mmHg. The mean (SD) PaCO(2) on the first blood gas of those infants commenced on volume guarantee from admission was 45.1 (12.5) mmHg. Severe hypo- or hypercapnoea occurred in 8% of infants at the time of their first blood gas measurement, and in <4% of blood gas measurements in the first 48 h. CONCLUSIONS: Infants ventilated with volume guarantee ventilation targeting approximately 4 mL/kg (range: 2.9-5.1) have acceptable PaCO(2) levels at the first blood gas measurement and during the first 48 h of life; and avoid severe hypo- or hypercapnoea over 90% of the time.     

Pressure-regulated volume control ventilation vs synchronized intermittent mandatory ventilation for very low-birth-weight infants: a randomized controlled trial

OBJECTIVE: To test the hypothesis that pressure-regulated volume control (PRVC), an assist/control mode of ventilation, would increase the proportion of very low-birth-weight infants who were alive and extubated at 14 days of age as compared with synchronized intermittent mandatory ventilation (SIMV). STUDY DESIGN: Ventilated infants with birth weight of 500 to 1249 g were randomized at less than 6 hours of age either to pressure-limited SIMV or to PRVC on the Servo 300 ventilator (Siemens Electromedical Group, Danvers, Mass). Infants received their assigned mode of ventilation until extubation, death, or meeting predetermined failure criteria. RESULTS: Mean +/- SD birth weights were similar in the SIMV (888 +/- 199 g, n = 108) and PRVC (884 +/- 203 g, n = 104) groups. No differences were detected between SIMV and PRVC groups in the proportion of infants alive and extubated at 14 days (41% vs 37%, respectively), length of mechanical ventilation in survivors (median, 24 days vs 33 days, respectively), or the proportion of infants alive without a supplemental oxygen requirement at 36 weeks' postmenstrual age (57% vs 63%, respectively). More infants receiving SIMV (33%) failed their assigned ventilator mode than did infants receiving PRVC (20%). Including failure as an adverse outcome did not alter the overall outcome (39% of infants in the SIMV group vs 35% of infants in the PRVC group were alive, extubated, and had not failed at 14 days). CONCLUSION: In mechanically ventilated infants with birth weights of 500 to 1249 g, using PRVC ventilation from birth did not alter time to extubation.     

Synchronous intermittent mandatory ventilation modes compared with patient triggered ventilation during weaning.

The efficacy of combining rate and pressure reduction during weaning by synchronous intermittent mandatory ventilation (SIMV) were compared with weaning by patient triggered ventilation (PTV) (pressure reduction alone) in two randomised trials. Regardless of ventilation mode, pressure was reduced to the same level according to the size of the infant. In the first trial, the SIMV rate was also reduced progressively to a minimum of 20 breaths/minute, and in the second to five breaths/minute. Forty premature infants aged 15 days of age or less were randomly allocated into each trial. No significant differences were found in the first trial between ventilation modes in either the duration of weaning or the number of infants in whom weaning failed. In the second trial, the duration of weaning was shorter by PTV than by SIMV (median 24 hours, range 7-432 v 50 hours, range 12-500; p < 0.05); weaning failed in two infants in the PTV group and in five in the SIMV group. It is concluded that weaning by a combination of pressure and rate reduction, such as can be achieved during SIMV, offers no significant advantage over pressure reduction alone.     

Effects of volume-targeted synchronized intermittent mandatory ventilation on spontaneous episodes of hypoxemia in preterm infants

BACKGROUND: Hypoxemic episodes in ventilated preterm infants are frequently caused by reduced ventilation due to a decrease in lung volume and acute worsening of respiratory mechanics. OBJECTIVE: To compare the efficacy of conventional time-cycled, pressure-limited flow synchronized intermittent mandatory ventilation (SIMV) and volume-targeted SIMV (VT-SIMV) in reducing the frequency and severity of these episodes. METHODS: SIMV and VT-SIMV were compared in preterm infants with frequent spontaneous episodes of hypoxemia. VT-SIMV was provided with the Draeger Babylog 8000plus ventilator in volume-guarantee mode. Results: In all, 32 infants (birth weight 668 +/- 126 g, gestational age 24.8 +/- 1.1 weeks, age 37.5 +/- 17.3 days) were studied during 2-hour periods of SIMV and VT-SIMV in random sequence. In an initial phase, a group of 12 infants was supported during VT-SIMV with a target tidal volume of 4.5 ml/kg (VT-SIMV 4.5). A planned interim analysis did not show differences in frequency and duration of hypoxemia between VT-SIMV 4.5 and SIMV, and the initial phase was stopped. In a second phase of the study, 20 infants were studied while supported with a target tidal volume of 6.0 ml/kg during VT-SIMV (VT-SIMV 6.0). In the second phase of the study, the frequency of the hypoxemic episodes did not change but the mean episode duration was shorter during VT-SIMV compared to SIMV. The proportion of mechanical breaths with small tidal volumes (< or =3 ml/kg) was reduced during VT-SIMV 6.0 versus SIMV, while the peak inspiratory pressure and mean airway pressure were increased. Conclusion: VT-SIMV did not reduce the frequency of hypoxemic episodes, but VT-SIMV 6.0 was effective in reducing the duration of the hypoxemic episodes.     

Comparison of weaning by patient triggered ventilation or synchronous intermittent mandatory ventilation in preterm infants

Forty preterm infants were entered into a randomized controlled trial to compare the efficacy and duration of weaning by patient triggered ventilation (PTV) to that of synchronous intermittent mandatory ventilation (SIMV). Infants were randomized during recovery from respiratory distress once ventilator rate had been reduced to 40 breaths per minute; weaning during PTV was by reduction in ventilator pressure only, whereas infants randomized to SIMV were weaned by reduction in rate only. Weaning failed in 12 infants, 6 from each group, the 12 infants were more immature than those in whom weaning succeeded ( p < 0.01). Overall, the duration of weaning did not differ significantly between the PTV and SIMV groups.     

神经调节辅助通气在早产儿呼吸窘迫综合征中的应用

目的观察神经调节辅助通气(neurally adjusted ventilatory assist,NAVA)对于早产儿呼吸窘迫综合征机械通气中触发同步性、气体交换和呼吸力学的影响。方法 10例呼吸窘迫综合征的早产儿先后给予NAVA和同步间歇指令通气(SIMV)模式通气各60 min,在模式选择顺序上采用随机化处理。比较不同通气模式中患儿生命体征、触发同步性和血气指标、呼吸力学参数。结果 NAVA模式下吸气触发延迟时间较SIMV模式明显缩短(P0.05);2种模式下动脉血pH、PaCO2、PaO2、PaO2/FiO2比较差异均无统计学意义;应用NAVA模式时自主呼吸频率、气道峰压、膈肌电活动信号和呼吸做功均较SIMV模式明显降低(P0.05)。结论对早产儿呼吸窘迫综合征进行机械通气治疗时,与SIMV模式相比,NAVA模式能改善触发同步性,降低气道峰压,并减少膈肌负荷和呼吸做功。     

Elimination of ventilator dead space during synchronized ventilation in premature infants

BACKGROUND: Mainstream airflow sensors used in neonatal ventilators to synchronize mechanical breaths with spontaneous inspiration and measure ventilation increase dead space and may impair carbon dioxide (CO(2)) elimination. OBJECTIVE: To evaluate a technique consisting of a continuous gas leakage at the endotracheal tube (ETT) adapter to wash out the airflow sensor for synchronization and ventilation monitoring without CO(2) rebreathing in preterm infants. DESIGN: Minute ventilation (V'(E)) by respiratory inductance plethysmography, end-inspiratory and end-expiratory CO(2) by side-stream microcapnography, and transcutaneous CO(2) tension (TcPCO(2)) were measured in 10 infants (body weight, 835+/-244 g; gestational age, 26+/-2 weeks; age, 19+/-9 days; weight, 856+/-206 g; ventilator rate, 21+/-6 beats/min; PIP, 16+/-1 centimeters of water (cmH(2)O); PEEP, 4.2+/-0.4 cmH(2)O; fraction of inspired oxygen (FIo(2)), 0.26+/-0.6). The measurements were made during four 30-minute periods in random order: IMV (without airflow sensor), IMV+Sensor, SIMV (with airflow sensor), and SIMV+Leak (ETT adapter continuous leakage). RESULTS: Airflow sensor presence during SIMV and IMV+Sensor periods resulted in higher end-inspiratory and end-expiratory CO(2), Tcpco(2), and spontaneous V'(E) compared with IMV. These effects were not observed during SIMV+Leak. CONCLUSIONS: The significant physiologic effects of airflow sensor dead space during synchronized ventilation in preterm infants can be effectively prevented by the ETT adapter continuous leakage technique.     

Effects of synchronization during nasal ventilation in clinically stable preterm infants

Nasal ventilation is increasingly used to reduce invasive ventilation in preterm infants. The effects of nasal ventilation and the advantages of synchronized nasal ventilation have not been fully evaluated. The objective was to compare the short-term effects of nasal intermittent mandatory ventilation (NIMV) and synchronized NIMV (S-NIMV) with nasal continuous positive airway pressure (NCPAP) on ventilation, gas exchange, and infant-ventilator interaction. Sixteen clinically stable preterm infants requiring NCPAP (GA, 27.6 ± 2.3 wk; birthweight (BW), 993 ± 248 g; and age, 15 ± 14 d) were exposed to NCPAP, NIMV at 20/min, NIMV at 40/min, S-NIMV at 20/min, and S-NIMV at 40/min for 1 h each (Infant-Star ventilator), in random order. Tidal volume, minute ventilation, and gas exchange did not differ significantly between NCPAP, NIMV, and S-NIMV. Inspiratory effort decreased during S-NIMV compared with NCPAP and NIMV, whereas inspiratory effort during NIMV did not differ from NCPAP. Active expiratory effort and expiratory duration increased during NIMV. Chest wall distortion, apnea and hypoxemia spells, abdominal girth, and comfort did not differ. In conclusion, there were no short-term benefits on ventilation and gas exchange of nasal ventilation compared with NCPAP in clinically stable preterm infants. However, synchronized nasal ventilation reduced breathing effort and resulted in better infant-ventilator interaction than nonsynchronized nasal ventilation.     

Volume guarantee ventilation, interrupted expiration, and expiratory braking

Background: In volume guarantee ventilation with the Dräger Babylog 8000 ventilator, inspiratory and expiratory flows are monitored and the expiratory tidal volume calculated following each inflation. The pressure for the next inflation is modified to ensure the expired tidal volume is close to the set value. Aim: To investigate interrupted expiration observed during volume guarantee ventilation of spontaneously breathing, ventilated infants. Methods: Spontaneously breathing infants, ventilated with volume guarantee, had recordings of gas flow, ventilator pressures, tidal volume waveforms, oximetry, heart rate, and transcutaneous oxygen and carbon dioxide during 10 minute recordings. Results: A total of 6540 inflations were analysed from 10 infants; 62% were triggered. Two different patterns were found: (1) Normal volume guarantee pattern with 97% of triggered and 91% untriggered inflations. It had a normal expiratory curve and a mean expired tidal volume within 3% of the set volume, but a large variation due to the babies'' breathing. (2) A pattern of interrupted expiratory flow after ～3% of inflations due to a small inspiration (～1.3 ml/kg) during expiration. This led the ventilator to calculate an inappropriate total expired tidal volume for that inflation and an increase in the pressure for the next inflation. Conclusions: After about 3% of inflations, with volume guarantee ventilation, interruption of the expiration causes an increased pressure for the next inflation of ～4.9 cm H₂O, compared with normal volume guarantee inflation. The interrupted expiration is most likely to be due to diaphragmatic braking.     

Volume guarantee ventilation, interrupted expiration, and expiratory braking.

BACKGROUND: In volume guarantee ventilation with the Dr?ger Babylog 8000 ventilator, inspiratory and expiratory flows are monitored and the expiratory tidal volume calculated following each inflation. The pressure for the next inflation is modified to ensure the expired tidal volume is close to the set value. AIM: To investigate interrupted expiration observed during volume guarantee ventilation of spontaneously breathing, ventilated infants. METHODS: Spontaneously breathing infants, ventilated with volume guarantee, had recordings of gas flow, ventilator pressures, tidal volume waveforms, oximetry, heart rate, and transcutaneous oxygen and carbon dioxide during 10 minute recordings. RESULTS: A total of 6540 inflations were analysed from 10 infants; 62% were triggered. Two different patterns were found: (1) Normal volume guarantee pattern with 97% of triggered and 91% untriggered inflations. It had a normal expiratory curve and a mean expired tidal volume within 3% of the set volume, but a large variation due to the babies' breathing. (2) A pattern of interrupted expiratory flow after approximately 3% of inflations due to a small inspiration (approximately 1.3 ml/kg) during expiration. This led the ventilator to calculate an inappropriate total expired tidal volume for that inflation and an increase in the pressure for the next inflation. CONCLUSIONS: After about 3% of inflations, with volume guarantee ventilation, interruption of the expiration causes an increased pressure for the next inflation of approximately 4.9 cm H2O, compared with normal volume guarantee inflation. The interrupted expiration is most likely to be due to diaphragmatic braking.     

Assisted ventilation in infants with acute bronchiolitis

Our experience concerns 36 infants ventilated for bronchiolitis over the last five years. Among the infants admitted in the pediatric department during the same period 11% have been ventilated. Their age ranged between 1.5 and 49.5 weeks (mean 9.2 weeks) and their weight between 2,700 and 8,000 g (mean 3,841 g). Fourteen were premature born infants. 16 patients have been intubated for apneas, 13 for clinical deterioration and 10 for hypercarbia. The duration of ventilation ranged between 1 and 18 days (mean 6.5 days). No death occurred. Neither neurological nor respiratory sequelae could be related to ventilation. Mechanical ventilation is a safe method able to suppress mortality in infants bronchiolitis.     

Morphine increases synchronous ventilation in preterm infants

Objectives: To examine the short-term cardiorespiratory effects of intravenous morphine infusion in ventilated preterm infants.
Methodology A randomized double-blind placebo-controlled trial in a neonatal intensive care unit. Twenty-six preterm infants (29-36 weeks gestation) with hyaline membrane disease requiring ventilatory assistance on the first day after birth were included in the study. A loading dose of morphine 100 μg/kg over 30 min followed by a continuous intravenous infusion at 10 μg/kg per hour was given. Primary measures were heart rate, blood pressure, respiratory rate and interaction of spontaneous respiration with mechanical ventilation. Secondary measures were durations of oxygen therapy, ventilator therapy and hospitalization as well as incidence of bronchopuimonary dysplasia, periventricular haemorrhage and pneumothorax.
Results Morphine-treated infants spent a significantly greater percentage of total ventilated time breathing in synchrony with their ventilators (median [IQ]= 72[58-87] vs 31 [17-51]%; P = 0.0008). Heart rate and respiratory rate, but not blood pressure, were reduced in morphine-treated infants. Duration of oxygen therapy was reduced (median [IQ]= 4.5[3-7] vs 8[4.75-12.5] days; P = 0.046).
Conclusions Intravenous morphine infusion increases synchronicity of spontaneous and ventilator-delivered breaths in preterm infants. Morphine reduces heart rate and respiratory rate without reducing blood pressure, and may help to reduce duration of oxygen therapy in preterm infants with hyaline membrane disease.     

Randomised study comparing extent of hypocarbia in preterm infants during conventional and patient triggered ventilation

AIM: To determine whether patient triggered ventilation (PTV) leads to greater exposure to significant hypocarbia than conventional ventilation (CMV) in premature infants during the first 72 hours of life. METHODS: Infants of 32 weeks gestation or less were included. Randomisation yielded 74 infants on PTV and 68 infants on CMV. Arterial PaCO(2) measurements were taken four hourly for the first 72 hours of life. RESULTS: The mean PaCO(2) levels on days 1, 2, and 3 were not significantly different between the two groups. The proportion of infants with PaCO(2) levels of 3.33 kPa or less did not differ between PTV and CMV infants. Mean percentages of infants with this level of hypocarbia at any time were 31.4%, 18.9%, 8.8% on days 1, 2, and 3 respectively. Cumulative hypocarbia, below a 3.33 kPa threshold, was 0.0084 kPa.h (PTV) versus 0.0263 kPa.h (CMV) per hour ventilated during the first 24 hours (p = 0.259). Risk factors associated with hypocarbia on day 1 were peak inspiratory pressure below 14 cm H(2)O (odds ratio 4.79) as well as FiO(2) below 0.30 (odds ratio 3.42). CONCLUSION: Exposure to hypocarbia (PaCO(2) 3.33 kPa or below) was not significantly different between PTV and CMV infants during the first 72 hours of life. Hypocarbia was common in both groups on day 1 and to a lesser extent on day 2. Infants with the least requirements for ventilatory support were at highest risk of hypocarbia on day 1 of life. Preterm infants with mild hyaline membrane disease require a more aggressive approach to weaning on both modes of ventilation, followed by extubation to limit the risk of hypocarbia.     

Neonatal resuscitation and preventive continuous positive pressure ventilation]

One of the aspects of prematurity in neonates is the respiratory distress syndrome. Although treatment with mechanical ventilation reduced the mortality rate, bronchopulmonary dysplasia still develops in many neonates. We have attempted to reduce intubation and mechanical ventilation by using, in the delivery room, humidified and warmed gas with fractional inspired oxygen as low as possible to obtain SaO2 between 85 and 95%. The gas was administered with a face mask using continuous positive air pressure 3-5 cm H2O. Seventeen out of 66 premature neonates born before the 35th week of gestation were ventilated immediately (n = 11) or subsequently (n = 6). Seven out of 26 infants (27%) born between 30 and 32 weeks required mechanical ventilation. In contrast, ventilation was necessary for eight out of 16 premature neonates born before the 29th week of gestation. Mortality rate was 6% (4/66) in the latter group (< 29 weeks), and only one neonate developed bronchopulmonary dysplasia.     

Mechanical ventilation in children

Mechanical ventilation can be lifesaving, but > 50% of complications in conditions that require intensive care are related to ventilatory support, particularly if it is prolonged. We retrospectively evaluated the medical records of patients who had mechanical ventilation in the Pediatric Intensive Care Unit (PICU) during a follow-up period between January 2002-May 2005. Medical records of 407 patients were reviewed. Ninety-one patients (22.3%) were treated with mechanical ventilation. Ages of all patients were between 1-180 (median: 8) months. The mechanical ventilation time was 18.8 +/- 14.1 days. Indication of mechanical ventilation could be divided into four groups as respiratory failure (64.8%), cardiovascular failure (19.7%), central nervous system disease (9.8%) and safety airway (5.4%). Tracheostomy was performed in four patients. The complication ratio of mechanically ventilated children was 42.8%, and diversity of complications was as follows: 26.3% atelectasia, 17.5% ventilator-associated pneumonia, 13.1% pneumothorax, 5.4% bleeding, 4.3% tracheal edema, and 2.1% chronic lung disease. The mortality rate of mechanically ventilated patients was 58.3%, but the overall mortality rate in the PICU was 12.2%. In conclusion, there are few published epidemiological data on the follow-up results and mortality in infants and children who are mechanically ventilated.     

Intermittent mandatory ventilation

Intermittent mandatory ventilation (IMV) is a mode of ventilation that allows the patient to make spontaneous breaths during the expiratory phase of mandatory ventilator breaths. There are two types of IMV according to whether respirator breaths are synchronized with the patient's respiratory efforts: Non-synchronized IMV and synchronized IMV (SIMV), and according to whether SIMV is volume- or pressure programmed. The main advantage of SIMV is that the respirator delivers the preset ventilator pressure and rate while allowing the patient to breath spontaneously, thus facilitating progressive weaning from mechanical ventilation. It diminishes the risk of barotrauma, produces less hemodynamic com-promise than control ventilation, reduces atrophy of respiratory muscles and the need for sedation and muscle relaxation and can be associated with pressure support ventilation.     

Haemodynamic features during high-frequency oscillatory ventilation in preterms

Aim: To compare the haemodynamic status during high-frequency oscillatory ventilation and conventional mechanical ventilation in very preterm infants with respiratory distress syndrome. Methods: Thirty-two neonates of less than 30 wk gestation randomly assigned to high-frequency oscillatory ventilation (n = 15) or conventional mechanical ventilation (n = 17) had three echocardiographies and one cerebral Doppler-echography under the same ventilation during the first 48 h of life. Results: Mean airway pressure was 2 cm H[Formula: See Text]O higher in infants ventilated with high-frequency oscillatory ventilation at the different echocardiographies. Comparable right ventricular indexes were observed in the two groups. Reduction of the ductus arteriosus diameter and ductal closure were significant only in neonates ventilated conventionally. Left ventricular performance and left ventricular contractility did not differ between the groups. The high-frequency group had lower end diastolic velocity and a higher resistance index in the anterior cerebral artery.

Conclusion: Compared with conventional mechanical ventilation, high-frequency oscillatory ventilation was achieved without altering cardiac function. However, the inability of the left ventricle to improve its performance in the presence of a significant ductal shunt suggests a narrow range of optimal pressures under this ventilatory mode.     

Endogenous pulmonary surfactant metabolism is not affected by mode of ventilation in premature infants with respiratory distress syndrome

OBJECTIVE: To determine if high frequency oscillatory ventilation (HFOV) decreases surfactant production in premature infants with respiratory distress syndrome (RDS). STUDY DESIGN: We randomized 19 infants <28 weeks of gestation to either HFOV (n = 8) or conventional ventilation (CV, n = 11) at 24 hours of life. After a 24-hour continuous infusion of uniformly labeled carbon 13 glucose (U-(13)C(6)) glucose, we measured (13)C enrichment in surfactant phosphatidylcholine (PC) in tracheal aspirate samples using gas chromatography/mass spectrometry. We calculated the fractional synthetic rate (FSR) of surfactant PC from labeled glucose and its half-life of clearance (T(1/2)). RESULTS: FSR did not differ between groups (4.7% +/- 2.7%/day CV vs 4.2% +/- 3.1%/day HFOV, P =.7). T(1/2) was 79 +/- 18 hours in the CV group and 76 +/- 23 hours in the HFOV group (P =.7). Neither degree of ventilatory support nor supplemental oxygen exposure correlated with surfactant metabolic indices. Three of 4 infants who died from RDS within the first month of life had a shorter T(1/2) than 14 of 15 infants who survived. CONCLUSION: Surfactant metabolism is similar in preterm infants ventilated with HFOV and CV. Shortened surfactant half-life may characterize a subset of preterm infants with lethal RDS.     

High frequency oscillatory ventilation <Emphasis Type="Italic">versus</Emphasis> synchronized intermittent mandatory ventilation in preterm neonates with hyaline membrane disease: <Emphasis Type="Italic">A randomized controlled trial</Emphasis>

This randomized controlled study was conducted to compare the efficacy and safety of High frequency oscillatory ventilation (HFOV) and Synchronized intermittent mandatory ventilation (SIMV) in preterm neonates with hyaline membrane disease requiring ventilation. The ventilation strategy in both the groups included achieving optimal lung recruitment and targeted blood gases. 49 patients received HFOV and 61 SIMV. The baseline characteristics were similar in both the groups. HFOV group demonstrated better early oxygenation, enabled reduction in oxygenation index (OI) within 24 h of ventilation (difference in mean OI at 1, 6, and 24 h of ventilation: P=0.004 in HFOV, and 0.271 in SIMV group). Duration of hospital stay was shorter in HFOV group (P=0.003). The complication rate and survival were similar in two groups.     

Pulmonary surfactant concentration during transition from high frequency oscillation to conventional mechanical ventilation

Objective: To test the hypothesis that conventional mechanical ventilation (CV) provides a greater stimulus to secretion of pulmonary surfactant than high frequency oscillatory ventilation (HFO).
Methodology: Sequential examination of surfactant indices in lung lavage fluid in a group of six infants with severe lung disease (group 1), ventilated with HFO and then converted back to CV as their lung disease recovered. A similar group of 10 infants (group 2) ventilated conventionally throughout the course of their illness were studied for comparison. In groups 1 and 2, two sequential tracheal aspirate samples were taken, the first once lung disease was noted to be improving, and the second 48–72 h later. Group 1 infants had converted from HFO to CV during this time.
Results: A marked increase in concentration of total surfactant phospholipid (PL) and disaturated phosphatidylcholine (DSPC) was seen in group 1 after transition from HFO to CV; the magnitude of this increase was significantly greater than that sequentially observed in group II (total PL: 9.4-fold increase in group 1 vs 1.8-fold in group 2, P =0.006; DSPC: group 1 6.4-fold increase vs . group 2 1.7-fold, P =0.02).
Conclusion: These findings suggest that intermittent lung inflation during CV produces more secretion of surfactant phospholipid than continuous alveolar distension on HFO, and raise the possibility that conservation and additional maturation of surfactant elements may occur when the injured lung is ventilated with HFO.