Indications and practical approach to non-invasive ventilation in acute heart failure

Abstract

In acute heart failure (AHF) syndromes significant respiratory failure (RF) is essentially seen in patients with acute cardiogenic pulmonary oedema (ACPE) or cardiogenic shock (CS). Non-invasive ventilation (NIV), the application of positive intrathoracic pressure through an interface, has shown to be useful in the treatment of moderate to severe RF in several scenarios. There are two main modalities of NIV: continuous positive airway pressure (CPAP) and pressure support ventilation (NIPSV) with positive end expiratory pressure. Appropriate equipment and experience is needed for NIPSV, whereas CPAP may be administered without a ventilator, not requiring special training. Both modalities have shown to be effective in ACPE, by a reduction of respiratory distress and the endotracheal intubation rate compared to conventional oxygen therapy, but the impact on mortality is less conclusive. Non-invasive ventilation is also indicated in patients with AHF associated to pulmonary disease and may be considered, after haemodynamic stabilization, in some patients with CS. There are no differences in the outcomes in the studies comparing both techniques, but CPAP is a simpler technique that may be preferred in low-equipped areas like the pre-hospital setting, while NIPSV may be preferable in patients with significant hypercapnia. The new modality 'high-flow nasal cannula' seems promising in cases of AHF with less severe RF. The correct selection of patients and interfaces, early application of the technique, the achievement of a good synchrony between patients and the ventilator avoiding excessive leakage, close monitoring, proactive management, and in some cases mild sedation, may warrant the success of the technique.

Keywords: Acute cardiogenic pulmonary oedema; Acute heart failure; Bilevel pressure support; CPAP; High-flow nasal cannula; Non-invasive ventilation.

Figure 1

(A) Pressure/time curves in continuous positive airway pressure (CPAP). A patient breathing on room air and after the application of CPAP. (B) Continuous positive airway pressure Boussignac mask. Boussignac mask with a nebulizer inserted in the circuit. This mask generates positive end expiratory pressure through a high transversal flow that creates a barrier effect.

Figure 2

Pressure support (PS) curves. Pressure curves of a patient breathing on room air, after the application of PS of 12 cmH₂O and after adding positive end expiratory pressure (PEEP) of 10 cmH₂O. Blue arrows indicate patient’s inspiratory effort that triggers the ventilator to deliver a decelerating flow to reach the preset PS. Inspiration is interrupted when the patient finishes the inspiratory effort or the flow arrives to a percentage of the peak (usually 25%). Inspiratory positive airway pressure (IPAP) is the sum of PS and PEEP, whereas PEEP is equivalent to expiratory positive airway pressure (EPAP). Note that tidal volumes change in every cycle according to patient’s effort.

Figure 3

Main interfaces used in non-invasive ventilation (NIV). (A–B) Two different models of total-face mask (probably with the best patient-ventilator adaptation); (C) Oronasal mask: the most used interface; (D) Nasal mask: not indicated in patients breathing by the mouth as those with acute pulmonary oedema. (E) High-flow nasal cannula: (see text); (F) Helmet: mostly used for continuous positive airway pressure mode, it allows more patient autonomy (speaking and eating), convenient when anticipating prolonged NIV. Other interfaces like nasal pillows, mouthpieces or laryngeal masks are usually not considered in acute heart failure.

Figure 4

Pressure and flow curves in non-invasive pressure support ventilation (NIPSV). (A) Non-invasive pressure support ventilation delivered with a cycling off of 25% of the maximal peak flow. (B) Decrease of the inspiratory time after the reduction of the ramp and the increase of the cycling off to 40%. Example of flow curve with Auto-PEEP (the expiratory flow does not arrive to 0). PEEP, positive end expiratory pressure; PS, pressure support.

Take home Figure

Algorithm for non-invasive ventilation in acute heart failure syndromes. After any NIV technique, patients should receive conventional oxygen therapy (COT) before switching to room air. The administration of COT in patients with SpO₂ ranging 91–93% is not clear. ¹Continuous positive airway pressure may be preferred in pre-hospital and low equipped areas, whereas non-invasive pressure support ventilation may be chosen by experienced teams, in patients with significant hypercapnia or COPD. Proportional assist ventilation, adaptive servoventilation, and HFNC have also been used in some trials as first line therapy in ACPE. COPD, chronic obstructive pulmonary disease; HFNC, high-flow nasal cannula; EI, endotracheal intubation; COT, conventional oxygen therapy; ACPE, acute cardiogenic pulmonary oedema.