Objectives: Nonrebreather face masks (NRM) are frequently used in patients with respiratory distress and profound hypoxemia. A simpler modification to the partial rebreather face mask, using only two pieces of respiratory tubing or "tusks," has also been shown to increase FiO2 compared with the NRM in five normal subjects. Clinically, we have observed this modification to further increase PaO2 in critically ill patients already using the NRM in the intensive care unit. This study 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 university teaching hospital and tertiary care referral center.
Subjects: Sixteen 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 served 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 each 30-min test period. Respiratory synchronization during the study period was achieved, using a metronome. In the normal subjects, PaO2 using 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). PaO2 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 change seen in mean PaCO2 with either mask in either group. The mean PaO2 returned to within 6% of baseline in both groups after the washout period.
Conclusions: Both normal subjects and patients with compromised pulmonary function achieved a higher PaO2 using a Tusk mask than when using the conventional NRM, at the same oxygen flow rate. Patients with hypoxemia may obtain lifesaving benefit from the additional concentration of oxygen delivered via the Tusk mask.