Setting up home noninvasive ventilation

Abstract

Home noninvasive ventilation (NIV) is widely used to correct nocturnal alveolar hypoventilation in patients with chronic respiratory failure of various etiologies. The most commonly used ventilation mode is pressure support with a backup respiratory rate. This mode requires six main settings, as well as some additional settings that should be adjusted according to the individual patient. This review details the effect of each setting, how the settings should be adjusted according to each patient, and the risks if they are not adjusted correctly. The examples described here are based on real patient cases and bench simulations. Optimizing the settings for home NIV may improve the quality and tolerance of the treatment.

Keywords: Home noninvasive ventilation; waveform analysis.

Figure 1.

Confusion between inspiratory IPAP and PS settings. The initial drop in pressure before the pressure increase from EPAP to IPAP represents the patient’s effort to trigger the mechanical breath. IPAP: inspiratory positive airway pressure; PS: pressure support; EPAP: expiratory positive airway pressure.

Figure 2.

(a) Asynchrony resulting from an EPAP setting that is too low in an obstructive patient with intrinsic PEP. Blue bars indicate ineffective inspiratory efforts. (b) Upper airway obstruction during NIV in a patient with obesity-hypoventilation syndrome. Airway obstruction can be partial (orange lines) or complete (red line), resulting in arousals with a large inspiratory flow (green lines). PEP: positive expiratory pressure; EPAP: expiratory positive airway pressure; NIV: noninvasive ventilation.

Figure 3.

(a) Mechanical breaths in a patient receiving home NIV triggered alternately by the patient (green lines) and the ventilator (yellow lines). Patient-triggered mechanical breaths result in a greater tidal volume than ventilator-triggered mechanical breaths. (b) A patient in complete asynchrony with the ventilator, making ineffective inspiratory efforts at their own pace (arrows) while the ventilator delivers controlled mechanical breaths according to the set backup respiratory rate. One possible reason is an inspiratory trigger set at a low sensitivity, which means the ventilator does not detect the patient’s inspiratory effort. (c) Mechanical breaths in a patient receiving home NIV triggered alternately by the patient (green lines) and the ventilator (yellow lines). The backup respiratory rate is set close to the spontaneous respiratory rate of the patient, thus “capturing it” (pink line). (d) Mechanical breaths in a patient on home NIV triggered alternately by the patient (green lines) and the ventilator (yellow lines). The expiratory time after the second patient-triggered mechanical breath is long without a patient inspiratory effort (pink line), which indicates a reduced ventilatory drive. NIV: noninvasive ventilation.

Figure 4.

(a) Example of an ineffective inspiratory effort due to a trigger setting that is not sensitive enough (left). Synchrony between the patient and ventilator is improved when the inspiratory trigger is set at the most sensitive level (right). (b) Auto-triggering due to an inspiratory trigger set at too sensitive a level.

Figure 5.

(a) Variations of the inspiratory pressure shape for the same EPAP and IPAP settings in four different ventilators. (b) Effect of a pressure rise time set at 100 ms (upper) and 700 ms (lower). When a long (shallow) pressure rise time is set, the IPAP of 15 cmH₂O is reached only at the end of inspiration. Inspiratory flow and tidal volume are reduced. (c) The peak in pressure and flow at the beginning of insufflation indicates that the increase in pressure (i.e. the pressure rise time) is too fast. EPAP: expiratory positive airway pressure.

Figure 6.

(a) Insufflation time depends on the pressure rise time, IPAP, expiratory trigger, and the patient’s respiratory mechanics which influences the inspiratory flow shape. The maximum insufflation time is achieved when the inspiratory flow reaches the baseline (pink line and arrow). (b) The minimum inspiratory time is set higher than the insufflation time. This results in a pause at the end of the inspiration (arrows) where the flow is zero. This pause occurs at the time the patient would start expiration, resulting in asynchrony that is usually uncomfortable for the patient. (c) During the pause, the flow becomes negative (arrows), indicating the patient is making an active expiratory effort.

Figure 7.

(a) Mechanical breath ending while the patient is still inspiring, as shown by the lower peak expiratory flow (first breath). This asynchrony disappears when the expiratory trigger setting is decreased (third breath). (b) Mechanical breath prolonged beyond the end of the patient inspiratory effort, as indicated by the pressure peak at the end of inspiration. The pressure peak disappears when the expiratory trigger setting is modified. (c) From left to right, the expiratory trigger is set at 70%, 50%, and 30% of the maximal inspiratory flow, respectively. The insufflation time increases when the expiratory trigger setting is lowered (1.1, 1.3, and 1.5 seconds, respectively). (d) The shape of the inspiratory flow curve depends on the patient’s respiratory mechanics: an obstructive lung (left), a normal lung (middle), and a restrictive lung (right). The same expiratory trigger setting (40%) results in an insufflation time that is too long for the obstructive and too short for the restrictive lung.

Figure 8.

(a) Usually, insufflation is ended by the expiratory trigger setting (percentage of the maximal inspiratory flow; left). Unintentional leaks prolong insufflation and create cycling asynchrony (middle). Setting a maximum inspiratory time results in an adequate insufflation time despite the leaks, and thus limits the leak-related asynchrony (right). (b) The inspiratory time setting is too short. All insufflations are of equal duration, irrespective of the patient’s neural time.

Figure 9.

(a) Pressure curve measured at the mask level with a 22-mm circuit with no configuration and no calibration (red line), and correctly configured (blue line). EPAP = 5 cmH₂O; IPAP = 15 cmH₂O. If the circuit is incorrectly configured and not calibrated, the pressure delivered at the mask may be different from the set pressure. (b) Pressure and flow measured at the mask when a face mask has been configured instead of a nasal mask. The inspiratory pressure delivered at the beginning of expiration is different from the setting. EPAP: expiratory positive airway pressure.

Figure 10.

(a) Example of an automatic ventilatory mode that increases EPAP when an obstructive event is detected (arrows). IPAP increases to maintain the set inspiratory pressure and unintentional leaks occur. (b) The pressure decay time is set longer from top to bottom. Peaks in pressure and flow are observed when the slope is too steep. (c) Progressive decrease in PS after accidental activation of negative ramping. The tidal volume is decreased and alveolar hypoventilation might occur. (d) Ramping decrease is activated accidentally at the beginning of ventilation. IPAP and EPAP diminish progressively over 5 minutes, and the patient spends the night with EPAP = IPAP = 3 cmH₂O, resulting in a marked reduction in tidal volume. EPAP: expiratory positive airway pressure.