Weaning newborns from mechanical ventilation

Respiratory Care for the Ventilated Neonate

Invasive ventilation is often necessary for the treatment of newborn infants with respiratory insufficiency. The neonatal patient has unique physiological characteristics such as small airway caliber, few collateral airways, compliant chest wall, poor airway stability, and low functional residual capacity. Pathologies affecting the newborn's lung are also different from many others observed later in life. Several different ventilation modes and strategies are available to optimize mechanical ventilation and to prevent ventilator-induced lung injury. Important aspects to be considered in ventilating neonates include the use of correct sized endotracheal tube to minimize airway resistance and work of breathing, positioning of the patient, the nursing care, respiratory kinesiotherapy, sedation and analgesia, and infection prevention, namely, the ventilator-associated pneumonia and nosocomial infection, as well as prevention and treatment of complications such as air leaks and pulmonary hemorrhage. Aspects of ventilation in patients under ECMO (extracorporeal membrane oxygenation) and in palliative care are of increasing interest nowadays. Online pulmonary mechanics and function testing as well as capnography are becoming more commonly used. Echocardiography is now a routine in most neonatal units. Near infrared spectroscopy (NIRS) is an attractive tool potentially helping in preventing intraventricular hemorrhage and periventricular leukomalacia. Lung ultrasound is an emerging tool of diagnosis and can be of added value in helping monitoring the ventilated neonate. The aim of this scientific literature review is to address relevant aspects concerning the respiratory care and monitoring of the invasively ventilated newborn in order to help physicians to optimize the efficacy of care.

[Recommendations for respiratory support in the newborn]

The recommendations included in this document will be part a series of updated reviews of the literature on respiratory support in the newborn infant. These recommendations are structured into twelve modules, with modules 4, 5, and 6 presented here. Each module is the result of a consensus process of all members of the Surfactant and Respiratory Group of the Spanish Society of Neonatology. They represent a summary of the published papers on each specific topic, and of the clinical experience of each one of the members of the group. Each module includes a summary of the scientific evidence available, graded into 4 levels of recommendations.

Lower back-up rates improve ventilator triggering during assist-control ventilation: a randomized crossover trial

OBJECTIVE

The objective of this study is to compare the effects of back-up ventilation rates (BURs) on triggered inflations and patient cardiorespiratory stability during assist-control/volume guarantee ventilation (AC/VG).

STUDY DESIGN

This study is a randomized crossover trial conducted in a neonatal unit in an Australian tertiary NICU. In all, 26 stable preterm infants on AC/VG ventilation were studied at BUR settings of 30, 40 and 50 min(-1). Inflation rate, triggering and cardiorespiratory measures of patient stability were compared during 20 min epochs with 10 min washout periods.

RESULT

The 26 infants studied were median (inter-quartile range) gestational age 27 (26, 30) weeks, birth weight 0.84 (0.75, 1.14) kg and FiO(2) 0.24 (0.21, 0.31) and age 6 (4, 19) days. At BURs of 30, 40 and 50, the proportions of inflations, which were triggered, were mean (s.d.) 85% (11), 75% (19) and 61% (25); P<0.01 for all comparisons. Total delivered inflation rates were 56 (8), 58 (9) and 62 (8) min(-1), respectively. Cardiorespiratory parameters did not vary between the settings.

CONCLUSION

Using a lower BUR allows greater triggering of ventilator inflations. Cardiorespiratory parameters including CO(2) levels were stable at all rates.

[Factors related to extubation failure in premature infants less than 32 weeks of gestation]

Even though ventilatory support for preterm infants has improved over the past few decades, about 30% of intubated preterm infants fail an extubation attempt. There are still no simple standards to determine the optimal extubation time for those infants.

OBJECTIVE

To identify factors related to extubation success or failure in preterm infants less than 32 weeks of gestation (WG).

POPULATION AND METHODS

Retrospective study including 162 newborns less than 32 WG, requiring mechanical ventilation within the first 24h of life. Successful extubation was defined as no need for reintubation for any reason at least 7 days after the first extubation attempt.

RESULTS

Forty-one infants failed extubation (25.3%); 149 infants (92%) had mechanical ventilation in their first 30min of life. These infants had a lower gestational age (p<0.001) and a lower birth weight (p=0.003). They required a higher FiO(2) (p<0.001) and maximum inspiratory pressure (p=0.002). The infants who failed extubation had a lower pH (p=0.001) and hematocrit (p=0.032), and a higher PCO(2) (p=0.003).

CONCLUSION

As previously described, a low gestational age is a major factor predicting the extubation failure. However, our data suggests that ventilator settings and blood gas should also be considered when attempting extubation, following written guidelines.

Medida da freqüência respiratória e do volume corrente para prever a falha na extubação de recém-nascidos de muito baixo peso em ventilação mecânica

OBJETIVO: Verificar se a freqüência respiratória (FR), o volume corrente (VC) e a relação FR/VC poderiam prever a falha na extubação em recém-nascidos de muito baixo peso submetidos à ventilação mecânica. MÉTODOS: Estudo prospectivo, observacional, de recém-nascidos com idade gestacional <37 semanas, peso ao nascer <1.500g, ventilados desde o nascimento por 48 horas a 30 dias. Após a indicação da retirada da ventilação mecânica, o neonato foi colocado em pressão positiva contínua (CPAP) por via traqueal por dez minutos, avaliando-se FR, VC e relação FR/VC por meio de um pneumotacógrafo conectado entre a cânula traqueal e o circuito do ventilador. Em seguida, o recém-nascido foi extubado e colocado em CPAP nasal, considerando-se falha na extubação a necessidade de reintubação em 48 horas. RESULTADOS: Das 35 crianças estudadas, 20 (57%) foram extubadas com sucesso e 15 (43%) necessitaram de reintubação. A FR e a relação FR/VC tenderam a ser maiores no grupo que falhou na extubação; o VC foi similar nos dois grupos. A sensibilidade e a especificidade para falha na extubação foram, respectivamente, 50 e 67% para FR, 40 e 67% para o VC e 40 e 73% para a relação FR/VC. CONCLUSÕES: A FR, o VC e a relação FR/VC apresentaram baixa sensibilidade e especificidade para prever a falha na extubação em recém-nascidos de muito baixo peso.

Volume targeted ventilation (volume guarantee) in the weaning phase of premature newborn infants

OBJECTIVE

Several options are currently available in neonatal mechanical ventilation: complete breathing synchronization (patient triggered ventilation, synchronized intermittent positive pressure ventilation--SIPPV); positive pressure flow-cycled ventilation (pressure support ventilation, PSV); and volume targeted positive pressure ventilation (volume guarantee, VG). The software algorithm for the guarantee volume attempts to deliver a tidal volume (Vt) as close as possible to what has been selected by the clinician as the target volume. Main objectives of the present study were to compare patient-ventilator interactions and Vt variability in premature infants recovering from respiratory distress syndrome (RDS) who were weaned by various ventilator modes (SIMV/PSV + VG/SIPPV + VG and SIMV + VG).

METHODS

This was a short-term crossover trial in which each infant served as his/her own control. Ten premature infants born before the 32nd week of gestation in the recovery phase of RDS were enrolled in the study. All recruited infants started ventilation with SIPPV and in the weaning phase were switched to synchronized intermittent mandatory ventilation (SIMV). Baseline data were collected during an initial 20-min period of monitoring with the infant receiving SIMV alone, then they were switched to SIPPV + VG for a 20-min period and then switched back to SIMV for 15 min. Next, they were switched to PSV + VG for the study period and switched back to SIMV for a further 15 min. Finally, they were switched to SIMV + VG and, at the end of monitoring, they were again switched back to SIMV alone.

RESULTS

Each mode combined with VG discharged comparable Vts, which were very close to the target volume. Among the VG-combined modes, mean variability of Vt from preset Vt was significantly different. Variability from the target value was significantly lower in SIPPV and PSV modes than in SIMV (P < 0.0001 and P < 0.04 respectively). SIPPV + VG showed greater stability of Vt, fewer large breaths, lower respiratory rate, and allowed for lower peak inspiratory pressure than what was delivered by the ventilator during other modes. No significant changes in blood gases were observed after each of the study periods.

CONCLUSIONS

With regards to the weaning phase, among combined modes, both of the ones in which every breath is supported (SIPPV/PSV) are likely to be the most effective in the delivery of stable Vt using a low working pressure, thus, at least in the short term, likely more gentle for the neonatal lung. In summary, we can suggest that the VG option, when combined with traditional, patient triggered ventilation, adheres very closely to the proposed theoretical algorithm, achieving highly effective ventilation.

Predictors of successful extubation of preterm low-birth-weight infants with respiratory distress syndrome

OBJECTIVE

The aim of the study was to measure pulmonary mechanics in infants with respiratory distress syndrome before extubation and to correlate pulmonary function values with successful extubation.

DESIGN

Clinical study.

SETTING

Neonatal intensive care unit.

PATIENTS

Fifty-one infants (birth weight, 1158.6 +/- 150.6 g; gestational age, 29.1 +/- 2.0 wks).

INTERVENTIONS

Ventilation and daily ventilatory management.

MEASUREMENTS AND MAIN RESULTS

Of the 51 infants studied, 35 (60.8%) were successfully extubated, whereas 16 (39.2%) required reintubation and mechanical ventilation within 72 hrs after extubation. All patients met the clinical and biochemical criteria for extubation. Variables of artificial ventilation before extubation were minimal in all the studied cases (Fio(2) </=0.4, inspiratory pressure </=20 cm H(2)O, ventilatory rate, </=10/min). Pulmonary mechanics were measured before extubation using a noninvasive, mobile VenTrak measuring station.

RESULTS

Significant differences in pulmonary function values between the groups were found. Lower resistance of airways and work of breathing and higher dynamic compliance, tidal volume, and minute ventilation before extubation were associated with successful extubation.

CONCLUSION

On the average, tidal volume values of >6 mL/kg, minute ventilation of >309 mL/kg/min, work of breathing of <0.172 J/L, dynamic compliance of >/=1 mL/cm H(2)O/kg, and resistance of airways of </=176 cm H(2)O/L/sec predicted successful extubation. We recommend measurement of pulmonary function as an assessment tool in determining readiness for extubation.