Upper Airway Resistance During Mouth Breathing in Patients with Unilateral and Bilateral Paralysis of the Recurrent Laryngeal Nerve

Abstract

The upper airway—subglottic to mouth—resistance was measured as the relationship between the pressure drop across, and flow through, this part of the respiratory tract in 10 male and 5 female cases of unilateral and 1 male and 9 female cases of bilateral paralysis of the recurrent nerve. The pressure-flow relationship was curvilinear during both inspiration and expiration and both resting and hyperventilation. All curves could be represented in terms of second degree polynomials. Means of upper airway resistance at a flow rate of 0.51/sec were 1.0 and 0.9 cm H₂O/1/sec at rest and during hyperventilation, respectively, in male cases of unilateral paralysis of the recurrent nerve. Corresponding values for female cases were 4.1 and 2.0 cm H₂O/1/sec. In cases of bilateral paralysis the mean upper airway resistance at a flow of 0.51/sec at rest was 21.5 cm H₂O/1/sec. The mechanical work performed in moving air through the upper airway was determined as the cumulative product of ventilated volume and pressure drop across this segment of the tract. The mean value during resting ventilation was 0.009 kpm¹/1 of V˙^E for male cases and 0.024 for female cases of unilateral paralysis of the recurrent nerve. For bilateral cases it was 0.074 kpm/1 of V˙_E. Eight unilateral and 3 bilateral cases of paralysis of the recurrent nerve were examined by static and dynamic spirometry. All of them showed low or subnormal values of MVV_F.