The various controlled trials that have compared HFV with conventional ventilation have not had the encouraging results obtained in animal experiments. They have failed to demonstrate significant improvements in the variables under study. These discrepancies in the results are most likely due to the different therapeutic strategies used, variability in clinical practices between centres, variability in the included patients, and advances in conventional mechanical ventilation.5,6

The outcomes observed in the more than 4000 infants studied in the various clinical trials comparing HFV, with a high volume strategy, and conventional mechanical ventilation, with respiratory rates of more than 60cycles per minute and minimal tidal volumes, were similar.

With the high lung volume strategy, there was a higher incidence of air leak syndrome and there was not an increased incidence of grade III or IV intraventricular haemorrhage or periventricular leukomalacia, so HFV with high lung volume does not increase the risk of neurologic morbidity.

There is no clear evidence that HFV offers any advantages compared to conventional ventilation when used as the initial ventilation strategy in preterm infants with respiratory distress syndrome.7,8 However, 1 out of 5 very low birth weight newborns may receive HFV at some point during their stay in the intensive care unit.

The long-term followup of adolescents aged 11–14 years born before 29 weeks of gestation that had been included in a randomised trial comparing the use of HFOV versus conventional ventilation immediately after birth found that those who had received HFOV had superior lung function with no evidence of poorer functional outcomes.9

When it comes to rescue therapy, few clinical trials have studied the use of HFV as rescue therapy in preterm patients with severe respiratory distress syndrome and interstitial emphysema. The results of most favour HFV when it comes to the resolution of the respiratory problem, but have not shown differences in mortality or the incidence of bronchopulmonary dysplasia.6,9

The studies that compared HFV and conventional ventilation when the use of surfactant was not yet widespread found that in preterm newborns with air leak syndrome, the use of HFV improved gas exchange with lower peak and mean pressures and was associated with a quicker resolution of pulmonary interstitial emphysema and decreased mortality, which suggests that this ventilation modality is an efficient tool in the management of air leak syndromes.10

Evidence from retrospective and observational studies suggests that the use of HFOV could improve the incidence of bronchopulmonary dysplasia and mortality, and reduce the need for extracorporeal membrane oxygenation (ECMO) in newborns with isolated congenital diaphragmatic hernia.11,12

The first clinical trial that compared HFOV with conventional mechanical ventilation in infants with a prenatal diagnosis of congenital diaphragmatic hernia did not find a statistically significant difference in mortality or the incidence of bronchopulmonary dysplasia between the two groups. The study found a shorter duration of ventilation and a less frequent need for ECMO in the conventional ventilation group.13

High-frequency oscillatory ventilation is a more effective rescue therapy compared to conventional ventilation in newborns with severe and reversible pulmonary disease eligible for ECMO. It improves gas exchange in term or near-term newborns with severe respiratory failure with no apparent increase in morbidity. It has been associated with a reduced incidence of chronic lung disease and intracranial haemorrhage in infants treated successfully with HFOV compared to newborns that were refractory to it and required ECMO.

The effectiveness of HFOV in improving gas exchange depends on the underlying disease, and is greater in cases of pneumonia, meconium aspiration and surfactant deficit.14

The combined use of inhaled nitric oxide and HFOV may be more effective than therapy alone in the management of newborns with reversible severe pulmonary disease and pulmonary hypertension, reducing the use of ECMO. This improvement has been observed especially in newborns with meconium aspiration.15

Small studies support the use of HFV in patients with increased intra-abdominal pressure that hinders conventional mechanical ventilation (omphalocoele, gastroschisis or necrotising enterocolitis) and pulmonary haemorrhage.16

As we have seen, the main indication for HFV is the need for lung recruitment. We propose the open lung strategy, that is, the use of a mean airway pressure (MAP) that maximises alveolar recruitment while avoiding atelectasis.

No objective data are available for the purpose of establishing criteria for the use of HFV. The clinical consensus is to consider the use of this modality in the following situations10:

• 1.

  When peak inspiratory pressures of more than 25cmH2O are required in conventional mechanical ventilation to achieve adequate ventilation.

• 2.

  When a FiO2 of more than 0.6 is needed after optimising conventional mechanical ventilation and there are signs of overdistension (pressure–volume loop, C20/C<0.8).

• 3.

  Air leak.

Oxygenation. Fig. 1 proposes an algorithm to guide the initiation and maintenance of HFV with the aim of maximising lung volume while avoiding hyperinflation:

Figure 1.

Algorithm for the initial management and maintenance of high-frequency ventilation. MAP, mean airway pressure; CMV, conventional mechanical ventilation.

(0.15MB).

In cases of air leak, HFV will be initiated with the same CDP applied in conventional mechanical ventilation with a conservative approach, tolerating higher FiO2 and pCO2 values.

Different high-frequency ventilators may not produce the same degree of hyperinflation at the same MAP. Furthermore, other signs of hyperinflation should be taken into account, such as a flattened diaphragm or compressed heart contours.

Ventilation. The initial amplitude should be of 40–50% (depends on the type of ventilator used) and adjusted in 10% increments to maintain a tidal volume between 1.5 and 2cc/kg and/or a pCO2 adequate for the individual patient. The RR will be determined based on the weight of the patient: rates of 12–15Hz can be used in patients with weights of less than 1500g, while approximately 10Hz can be applied to late preterm or term newborns. Lower rates may be needed in cases of severe lung disease.

There are ventilators that offer a volume guarantee option for HFOV. The hypothetical benefit of this option compared to maintaining the pCO2 levels within an optimal range remains to be demonstrated.17

Table 2 proposes an oxygenation and ventilation protocol for HFV.

Weaning. Once lung recruitment has been achieved and oxygen requirements have dropped to approximately 0.3–0.35, progressive decreases in MAP will be attempted every 12h, maintaining the FiO2 within the desired threshold. The speed of weaning will depend on the disease and developmental stage of the patient.

Once the MAP reaches values of 10–12cmH2O, extubation will be contemplated. Extubation can be performed following a switch to conventional mechanical ventilation or directly from HFV (with MAP values of 8–10cmH2O).

Special care. The following recommendations constitute a general guideline for the optimal management of patients receiving HFV:

• •

  The tidal volume delivered to the patient varies with changes in pulmonary conditions, so close monitoring of pO2 and pCO2 by means of transcutaneous sensors is recommended.

• •

  Lung expansion should be assessed by chest radiography whenever substantial changes in MAP are made.

• •

  Arterial blood pressure and cardiac output should be optimised, including their exhaustive monitoring and contemplating the administration of fluids and/or inotropic support for their management.

• •

  Sedoanalgesia with or without muscle relaxants may be needed in some occasions when the respiratory efforts of the patient interfere with ventilation.

• •

  Endotracheal suctioning is indicated in case of decreased tactile fremitus, CO2 levels increase or oxygenation decreases with no other apparent cause. The use of closed suction systems is recommended to prevent lung derecruitment during disconnection from the ventilator.

Haemodynamic complications. When a high MAP is needed to achieve lung recruitment, certain complications may result from the increased intrathoracic pressure, such as increased central venous pressure or decreased venous return or cardiac output.

Air trapping.

• 1.

  HFV is used as rescue therapy in patients with severe lung disease in whom treatment with conventional mechanical ventilation has failed (B).

• 2.

  HFV is more effective in combination with inhaled nitric oxide (B).

• 3.

  HFV offers no advantages compared to conventional ventilation in the initial respiratory management of respiratory distress syndrome in preterm newborns (A).

• 4.

  The MAP optimisation strategy may be most appropriate (B).

• 1.

  Lethal chromosomal disorders

• 2.

  Severe irreversible brain damage

• 3.

  Grade III or greater intraventricular haemorrhage

• 1.

  Irreversible organ damage (possibility of transplantation)

• 2.

  Body weight<2kg

• 3.

  Postmenstrual age<34 weeks

• 4.

  Disease with a high probability of poor prognosis

The efficacy of ECMO is based on the ability of the patient to recover from lung disease in a short period of time (14–21 days).

From the second week of ECMO, the risks and complications associated with the technique (clot formation, nosocomial infection, mechanical problems in the circuit, etc.) increase. Most facilities accept a maximum duration of ECMO of 20–30 days, although improvements in the use of this technique have resulted in increases in this time interval.