Efficacy of a New Full Face Mask for Noninvasive Positive Pressure Ventilation: Conclusion
Schwartzstein et al have shown a significant reduction in the sensation of dyspnea when normal subjects have cold air directed to the cheeks while breathing against an inspiratory resistive load. Di-Giorgio and Giulio showed similar results in normal subjects breathing through a range of linear resistive loads from 1.5 to 15 cm H2O when ambient air produced by a fan was applied to the subject’s face. Although, the mechanism(s) responsible for the reductions in dyspnea when cold or ambient air is directed to the face are unknown, Schwartzstein and colleagues hypothesized that stimulation of afferent trigeminal nerve receptors may have altered the central perception of breathlessness.
It is conceivable that stimulating facial cutaneous receptors via continuous airflow during NPPV via the TFM may have contributed in part to a reduction in the patient’s sensation of dyspnea while using this mask. Whatever the mechanism(s), however, all patients reported the greatest reduction in dyspnea during noninvasive ventilation when using the TFM so.
Complications that arose using the TFM ventilation were minimal. Since this form of face mask has a much larger volume, it has a significantly greater amount of dead space compared with other commercially available forms of N or NO masks. The dead space volume of the TFM is 1,500 ml, compared with 105 ml with the N mask and 250 ml with the NO mask (not accounting for a reduction in dead space by facial structures when wearing the mask). However, in no patient did this increased amount of dead space pose a problem by either increasing the patient’s sense of dyspnea or adversely affecting blood gas tensions.
To minimize the potentially adverse effects of an increased dead space with the full face mask, the manufacturer recommends a base flow sufficient to maintain an expiratory positive airway pressure of 4 or 5 cm H2O at all times.
Category: Respiratory Symptoms
Tags: face mask, hypercapnia, noninvasive ventilation, respiratory failure