DELIVERY OF HIGH-CONCENTRATIONS OF INSPIRED OXYGEN VIA TUSK MASK

Objectives: Nonrebreather face masks (NRM) are frequently used in pati ents with respiratory distress and profound hypoxemia , A simpler modi fication to the partial rebreather face mask, using only two pieces of respiratory tubing or ''tusks,'' has also been shown to increase Flo( 2) compared with the NRM in five normal subjects. Clinically, we have observed this modification to further increase Pao(2) in critically il l patients already using the NRM in the intensive care unit, This stud y was designed to compare the Tusk mask with the NRM in both a larger group of normal subjects and in patients with underlying lung disease. Design: Prospective, randomized, crossover study, Setting: A universi ty teaching hospital and tertiary care referral center. Subjects: Sixt een normal subjects (11 male and 5 female; age 30.4 +/- 6.8 [SD] yrs) and seven patients with interstitial lung disease (ILD) (3 male and 4 female; age 68.1 +/- 11.9 yrs), Interventions: Subjects and patients s erved as their own controls and were randomized to wear either the NRM or Tusk mask for a 30-min period. After a 60-min washout period, the other mask was applied, Measurements and Main Results: Arterial blood gas measurements were performed immediately before and at the end of e ach 30-min test period, Respiratory synchronization during the study p eriod was achieved, using a metronome. In the normal subjects, Pac, us ing the NRM and Tusk masks increased 290.0 +/- 57.1 torr(38.6 +/- 7.6 kPa) and 330.0 +/- 68.9 torr (44.0 +/- 9.2 kPa), respectively (p =.032 ). Pac, increased 293.4 +/- 38.0 torr (39.1 +/- 5.1 kPa) with the NRM and 378.4 +/- 61.7 torr (50.4 +/- 8.2 kPa) with the tusk mask (p=.001) in the patients with ILD. There was no statistically significant chan ge seen in mean Paco(2) with either mask in either group. The mean Pao (2) returned to within 6% of baseline in both groups after the washout period. Conclusions: Both normal subjects and patients with compromis ed pulmonary function achieved a higher Pao(2) using a Tusk mask than when using the conventional NRM, at the same oxygen flow rate. Patient s with hypoxemia may obtain lifesaving benefit from the additional con centration of oxygen delivered via the Tusk mask.