Air Leaks During Noninvasive Positive Pressure Ventilation
To some degree, leaks are present when using nasal NIPPV during sleep in all patients. The major potential adverse effects of such leaks are reduced efficiency of ventilation and sleep fragmentation (115-118). A variety of measures, more or less efficacious, have been suggested to address problematic leaks. These include: preventing neck flexion, reclining in a semi-recumbent position, discouraging the mouth from opening by use of a chin strap (117) or a cervical collar, switching to pressure-preset mode (19), decreasing the peak inspiratory pressure, increasing the delivered volume (20), optimizing the interface (12,16), and possibly switching to nasal pillows or a full-face mask (119). The effectiveness of these measures must be confirmed during sleep recordings.
Nasal Dryness, Congestion, and Rhinitis
With reference to the CPAP literature, the side effects of nasal dryness, congestion, and rhinitis are related to a defect of humidification promoted by air leaks (120). For patients with nasal and mouth dryness, a cold passover or a heated humidifier (the latter is more effective) (121) can be used. Heat/moisture exchangers are not well adapted to the case of leaks since the "dry" flow from the ventilator is higher than the "dampened" flow returning from the patient. In a large series, a minority of patients needed humidifiers (10).
Aerophagia, or swallowing air, is frequently reported by patients, but rarely intolerable (122). Minor clinical signs are: eructation, flatulence, and abdominal discomfort. Aerophagia is usually dependent on the level of inspiratory pressure and is more commonly seen when using volume and/or mouthpiece ventilation and in the care of patients with neuromuscular disease. The incidence decreases if the peak inspiratory pressure is kept below 25 cm H2O pressure.
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