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Effect of Face Mask Design on Inhaled Mass of Nebulized Albuterol, Hui-Ling Lin MSc RN RRT, Ruben D Restrepo MD RRT, Douglas S Gardenhire MSc RRT-NPS, BACKGROUND: Aerosol face mask design and the distance at which the face mask is held from the
face affect the delivery of nebulized medication to pediatric patients. OBJECTIVE: To measure the
inhaled mass of nebulized albuterol with 3 types of pediatric face mask, at 3 different distances from the
face, with a model of a spontaneously breathing infant. METHODS: We compared a standard pediatric
face mask and 2 proprietary pediatric face masks (one shaped to resemble a dragon face, the other
shaped to resemble a fish face). The albuterol was nebulized with a widely used jet nebulizer. Aerosol
delivery with each type of mask was measured with the mask at 0 cm (ie, mask directly applied to the
mannequin face), 1 cm, and 2 cm from the mannequin face. In each test the nebulizer was filled with a
3-mL unit dose of albuterol sulfate and powered by oxygen at 8 L/min, with a total nebulization time of
5 min. The mannequin face was connected to a lung simulator that simulated a spontaneously breathing
infant. We measured inhaled mass by collecting the aerosol on a 2-way anesthesia filter that was
attached to the back of the mannequin’s oral opening via a 15-mm silicon adapter. We also measured
residual drug left in the nebulizer, and estimated the drug lost to the atmosphere. RESULTS: The
mean
؎ SD inhaled percentage of the nominal dose values at 0 cm, 1 cm, and 2 cm, respectively, were
2.18
؎ 0.53%, 1.45 ؎ 0.46%, and 0.92 ؎ 0.51% with the standard mask; 2.65 ؎ 0.55%, 1.7 ؎ 0.38%,
and 1.3
؎ 0.37% with the dragon mask; and 3.67 ؎ 0.8%, 2.92 ؎ 0.4%, and 2.26 ؎ 0.56% with the fish
mask. With all 3 masks there was a statistically significant difference (p < 0.001) in inhaled mass
between the 0 cm and 2 cm distance. The fish mask had a significantly higher (p < 0.001) inhaled mass
than the dragon mask or the standard mask, at all 3 distances. CONCLUSIONS: The inhaled mass of
albuterol is significantly reduced when the mask is moved away from the face. The fish mask had
significantly higher inhaled mass than the standard mask or the dragon mask, under the conditions we
studied. Mask design may affect nebulized albuterol delivery to pediatric patients.
Key words: albuterol,
aerosol, face mask, inhaled drug mass, pediatric, jet nebulizer.
[Respir Care 2007;52(8):1021–1026. 2007
Daedalus Enterprises]
Hui-Ling Lin MSc RN RRT is affiliated with the Respiratory Care Pro- IngMar Medical, Pittsburgh, Pennsylvania, provided the Active Servo gram, Dakota State University, Madison, South Dakota. Ruben D Re- Lung 5000 simulator used in this research.
strepo MD RRT is affiliated with the Department of Respiratory Care,University of Texas Health Science Center, San Antonio, Texas. DouglasS Gardenhire MSc RRT-NPS and Joseph L Rau PhD RRT FAARC are The authors report no conflicts of interest related to the content of this paper.
affiliated with the Division of Respiratory Therapy, Georgia State Uni-versity, Atlanta, Georgia.
Correspondence: Ruben D Restrepo MD RRT, Department of Respira- This study represents the master’s thesis research of Hui-Ling Lin MSc RN tory Care, University of Texas Health Science Center at San Antonio, RRT in the Division of Respiratory Therapy at Georgia State University.
7703 Floyd Curl Drive, Mail Code 6248, San Antonio TX 78229-3900.
Hui-Ling Lin MSc RN RRT presented a version of this paper at the 51st International Respiratory Congress of the American Association for Respi-ratory Care, held December 3–6, 2005, in San Antonio, Texas, at which, forthe paper, Hui-Ling Lin MSc RN RRT was awarded a Fellowship for Aero-sol Technique Development from Monaghan Medical/Trudell.
RESPIRATORY CARE • AUGUST 2007 VOL 52 NO 8 EFFECT OF FACE MASK DESIGN ON INHALED MASS OF ALBUTEROL Introduction
Gas-powered jet nebulizers are commonly employed to deliver medications to patients’ airways via a mouthpieceor a face mask. Although no significant difference in clin-ical response has been found in adults between a mouth-piece and a fitted mask,1 administering nebulized medica-tion with a fitted face mask to infants and toddlers can bequite challenging. As infants grow older, they are increas-ingly aware of their surroundings and frequently becomedistressed with the application of a mask. When the childis upset, the seal between the face and the mask is easilybroken, which causes entrainment of ambient air and de-creases the quantity and the concentration of aerosol in- Fig. 1. Configuration of equipment for simulation of pediatric breath- ing and nebulized albuterol delivered via face mask, with the mask An alternative technique for aerosol delivery to the pe- at 0 cm, 1 cm, and 2 cm from the chin of the mannequin face.
diatric patient is “blow-by,” in which the clinician aims theaerosol flow toward the patient’s face instead of applying a mask. We previously reported a 43% reduction in theinhaled dose with a 1-cm gap between the mask and the Lung Model
inhalation hole on a mannequin face, and a 67% reduction A model of a spontaneously breathing infant was cre- with 2-cm gap.4 Similar data were previously found by ated with a lung simulator (ASL [Active Servo Lung] 5000, IngMar Medical, Pittsburgh, Pennsylvania). The sim-ulator was set at a maximum muscle pressure of13.5 cm H O, a resistance of 20 cm H O/L/s, and a com- pliance of 5 mL/cm H O, to generate a tidal volume of 60 mL. The respiratory rate was set at 20 breaths/min,inspiratory time was 0.7 s, inspiratory-expiratory ratio was1:3, and inspiratory flow was 120 mL/s.
There are several pediatric face masks available for use A mannequin face with a 15-mm silicon adapter was with jet nebulizers. Research on the efficiency of face attached to the inhalation filter (a 2-way, nonconductive masks with a metered-dose inhaler (MDI) with spacer/ anesthesia filter, model 1T0241, Baxter Healthcare, Deer- holding chamber suggests that the choice of face mask and field, Illinois), which collected the inhaled aerosol. A sim- the integrity of the interface between the mask and the ilar filter was attached to the lung simulator, for protection child’s face is critical in determining the inhaled dose in from inhaled aerosol, but was not used to calculate drug children.6–11 Newly redesigned masks for MDIs allow a better seal with the patient’s face. The pediatric face masksused with jet nebulizers have traditionally been smaller Study Design
versions of the masks used with adults. These pediatricmasks have a considerably larger volume of potential dead A nebulizer (Misty-Neb, Baxter Healthcare Corpora- space and relatively large side holes, compared to adult tion, Valencia, California) was attached to a standard face face masks. Manufacturers have designed pediatric face mask (Hudson RCI, Durham, North Carolina), then to a masks in an effort to improve drug delivery to children. In mask designed to resemble a dragon face (DragonMask, our preliminary literature search, we found a paucity of KidsMED, Hinsdale, Indiana), and then to a mask de- reports on inhaled drug mass with jet nebulizers attached signed to resemble a fish face (Bubbles the Fish, PARI to pediatric face masks of various designs.
Respiratory Equipment, Monterey, California) (Table 1).
The purpose of the present study was to determine the Each nebulizer was held in a vertical orientation with a inhaled drug mass, nebulizer residual drug loss, and esti- metal holder and a clamp to prevent error from misalignment.
mated ambient loss during delivery of nebulized albuterol All masks were held perpendicular to the inhalation filter to 3 brands of pediatric face mask, with the mask at 0 cm, 1 cm, and 2 cm from a mannequin face connected to a Each trial was conducted by placing the face mask at breathing simulator, with the breathing pattern of a spon- 0 cm (ie, the mask was in contact with the mannequin face), 1 cm, or 2 cm from the mannequin face, measured RESPIRATORY CARE • AUGUST 2007 VOL 52 NO 8 EFFECT OF FACE MASK DESIGN ON INHALED MASS OF ALBUTEROL *Designed specifically for use with PARI nebulizers.
†Mask volume was measured by filling the mask with water.
‡Holes on both sides.
from the lower edge of the mask to the chin of the man- terol, after each trial the mask and the mannequin face nequin face. Aerosol delivery with each type of mask was were wiped with an alcohol pad, and the 15-mm silicon To minimize variations among masks and among distances Because of the open nature of the model (ie, because of caused by nebulizers, we used 5 different Misty-Neb nebu- the open space between the mask and the mannequin face), lizers. Each nebulizer was used with all 3 mask types and at some aerosol was lost to the ambient air, so that aerosol all 3 distances, so each nebulizer was run a total of 9 times, could not be collected and measured. Instead, it was cal- in random order; thus, there were 45 separate trials.
culated by subtracting the inhaled drug mass and the dead All the nebulizers were powered by 50 psi oxygen at volume drug mass from the starting (nominal) dose of 8 L/min. Gas flow to the nebulizer was started immedi- ately after the first simulator breath. Then, 100 simulated A simple linear regression and prediction equation were breaths were run, in 5 min; then the gas flow was termi- developed from a known albuterol sulfate solution (Sigma, nated in synchrony with the simulator. In each trial the St Louis, Missouri). All drug amounts were analyzed via nebulizer was filled with a 3.0-mL unit dose of albuterol spectrophotometry (Beckman Instruments, Fullerton, Califor- sulfate, which contains 2.5 mg of albuterol base.
nia), at a wavelength of 276 nm. The solvent was 0.1 normalhydrochloric acid solution. The inhalation filter was washed Measurements
for 1 min, with gentle agitation. The spectrophotometer wascalibrated prior to trials, with a holmium oxide filter (Beck- The inhaled drug mass was measured by extracting the man Instruments, Fullerton, California) to determine the wave- aerosol from the inhalation filter. In bench models, the length accuracy, and set to zero by running the solvent alone inhalation filter is placed in the final path of aerosol that before each analysis. The concentration of the sample solu- would be inhaled by a patient.12 Each nebulizer was weighed tion and the amount of albuterol were calculated from a known before and after filling with albuterol, and following neb- concentration/absorbency relationship.
ulization, to determine the amount of solution remaining inthe device (dead volume). The dead volume was collectedby washing the nebulizer system components with 0.1 nor- Statistical Analysis
mal hydrochloric acid solution (JT Baker, Phillipsburg, Means and standard deviations were calculated New Jersey). The dead volume was then analyzed via (SPSS 11.5, SPSS, Chicago, Illinois) for each component spectrophotometry (Beckman Instruments, Fullerton, Cal- of the total drug mass, nebulizer loss, and estimated am- ifornia), using a known amount of solvent added to the bient loss. A 2-way factorial analysis of variance (ANOVA) dead volume. To avoid contamination with residual albu- was performed for the masks and distances, with an alpha RESPIRATORY CARE • AUGUST 2007 VOL 52 NO 8 EFFECT OF FACE MASK DESIGN ON INHALED MASS OF ALBUTEROL Fig. 2. Mean inhaled percentage of nominal dose with 3 types of face mask and 3 distances from the mannequin face. The differencesbetween the fish mask and both the standard mask and the dragon mask were significant at all distances. Inhaled percentage of nominaldose was significantly greater with all masks at 0 cm than at 2 cm. * p Ͻ 0.001 for all comparisons of 0 cm versus 2 cm. † p Ͻ 0.001 forfish mask versus standard mask and dragon mask at all distances.
level of 0.05.13 Follow-up comparisons of each device at the nebulizer, and lost to the ambient air, for each type of each distance were performed using 1-way ANOVA with A 1-way factorial ANOVA with Bonferroni adjustment We calculated the effect size, which is an index of the for masks and distances indicated a statistically greater magnitude of a treatment effect. Unlike tests for significance, inhaled drug mass with the fish mask than with the stan- measures of effect size in ANOVA determine the degree of dard mask or the dragon mask, overall (p Ͻ 0.001), and association between variables and the effect of the dependent significant decrease in inhaled drug mass as distance in- variable. We used the partial eta squared (␩2) value to esti- mate the degree of association between the samples.
Figure 2 shows the percentage of the nominal dose val- ues collected on the inhalation filter. Bonferroni compar- isons of the 3 masks showed significant differences(p Ͻ 0.001) in inhaled drug mass between the standard Table 2 lists the mean Ϯ SD values for the percent of mask and the fish mask, and between the fish mask and the the nominal dose collected on the inhalation filter, left in dragon mask. However, there was no significant differ- Drug Mass on the Inhalation Filter, Left in the Nebulizer, and Estimated Ambient Loss *Significant difference overall (p Ͻ 0.001).
†Significant difference overall across distances (p Ͻ 0.001).
RESPIRATORY CARE • AUGUST 2007 VOL 52 NO 8 EFFECT OF FACE MASK DESIGN ON INHALED MASS OF ALBUTEROL ence between the standard mask and the dragon mask. Thepartial ␩2 was 0.617 compared among the 3 distances, and0.591 compared among the 3 masks, which indicates thatthe probability of nonoverlap among the 3 groups is ap-proximately 33–38%, according to Cohen’s standard.14 Discussion
The results of this in vitro study indicate that the inhaled drug mass with the fish mask was significantly higher thanwith the standard mask or dragon mask. Furthermore, ourresults are consistent with previous studies that reported asignificant drop in the inhaled drug mass when the maskwas moved away from the face.4–11,15,16 The standard pediatric aerosol mask is a smaller version of the adult mask and has a considerably larger dead spacethan the fish mask or dragon mask. The 2-cm side holes inthe standard mask allow more aerosol particles to escape Fig. 3. Aerosol trajectory with the fish mask. With the fish mask theaerosol is aimed more directly at the nasal/oral area than with the during nebulization. The side-holes on the dragon mask are 1 cm in diameter, so, theoretically, less aerosol shouldbe lost than with the standard mask, but our results do notsupport that theory. The lower inhaled drug mass with the The standard mask and dragon mask direct the aerosol standard mask and dragon mask may be due to aerosol to the upper portion of the mask, whereas the fish mask inertia (the tendency of an object to travel in a straight line directs the aerosol towards the nasal/oral area (see Fig. 3).
once it is moving). In the standard mask and the dragon We hypothesize that the difference in angle of aerosol mask, the aerosol enters the mask traveling upwards, to- entry into the mask influences inhaled mass, because aim- wards the top of the mask, and inertia may cause the ing the aerosol more directly at the nasal/oral area reduces aerosol particles to impact the inner surface of the mask, aerosol impact on the mask. A recent 3-dimensional nu- whereas with the fish mask the aerosol travels directly merical study by Shakked et al17 on the administration of toward the nasal/oral area (Fig. 3). In a previous study that aerosolized drugs to infants via a hood supports our theory compared inhaled drug mass delivered via T-piece versus of the importance of directing the aerosol toward the nasal/ via standard pediatric mask, we found a higher inhaled oral area. Shakked et al found that the number of aerosol drug mass with the T-piece.4 The T-piece is constructed particles that penetrated the nostrils of their infant model with a 90° angle, with a nebulizer that directs the aerosol significantly decreased the further away the aerosol funnel stream toward the patient’s face. Because of this physical design, we hypothesized that the inhaled drug mass with It is also possible that a better face seal is created with the T-piece, with or without distancing the mask from the the fish mask, by the extended cover on the face. Also, the mannequin face, was greater than with all of the masks we fish mask’s smaller side holes may keep more aerosol particles in the mask during the treatment time and reduce Sangwan and collaborators15 nebulized radiolabeled nor- mal saline to an infant breathing model. They used 7 com- Though several studies have reported data on inhaled drug mercially available face masks interfaced with 3 compat- mass when the face mask is moved away from the face ible fitting nebulizers, to compare the facial deposition of model,4–11,15,16 we found only 3 studies that evaluated the aerosol. The fish mask in combination with the Pari LC impact of leak between the pediatric mask and the face on Plus nebulizer had the highest inhaled drug mass, at 6.0% inhaled drug mass when the aerosol is generated via jet neb- of the nominal dose. It also had one of the lowest eye and ulizer.4,5,16 Our previous study reported data that compared facial aerosol depositions. The combination of the Hudson the inhaled drug mass with a standard mask versus with a mask and the Misty-Neb nebulizer resulted in 66% less T-piece at 0 cm, 1 cm, and 2 cm from the inhalation filter.4 inhaled drug than the combination of the fish mask and the However, in that study, albuterol nebulization was run to the Pari LC Plus nebulizer.15 In a similar study, Smaldone and onset of sputtering, with no tapping of the nebulizer. The colleagues nebulized 0.25 mg of budesonide to a pediatric mean inhaled percentage of the nominal dose with the stan- breathing model. They found that the combination of the dard aerosol mask at 0 cm (2.88%), 1 cm (1.61%), and 2 cm fish mask and the Pari LC Plus yielded about 65% higher (1.3%) in that study4 compares well to the present results inhaled drug mass than the combination of the standard with the standard mask: 2.18%, 1.45%, and 0.92%, respec- mask and the Hudson Updraft II jet nebulizer.16 tively. The present study values also compare well to those RESPIRATORY CARE • AUGUST 2007 VOL 52 NO 8 EFFECT OF FACE MASK DESIGN ON INHALED MASS OF ALBUTEROL found by Everard et al, who nebulized 4 mL (40 mg) of uated as a clinical strategy for delivering aerosolized medi- sodium cromoglycate. Their mean percentage of the nominal cation to children. Also, the design of the face mask affects dose values at 0 cm, 1 cm, and 2 cm were 3.13%, 1.2%, and nebulized aerosol delivery to pediatric patients. Clinical re- 0.45%, respectively.5 Smaldone et al16 quantified in vitro the search is necessary to determine whether the design of nebu- influence of the face mask on the inhaled mass of budesonide lizers or face masks affects clinical response. These findings from jet nebulizers and pressurized MDIs with valved hold- may be useful for interpreting future clinical studies on face ing chambers. The configuration that lacked mask/face seal mask delivery of aerosolized drugs to pediatric patients.
was associated with significantly lower inhaled mass than thesealed mask/face configuration, with both the MDIs and the ACKNOWLEDGMENTS
A recent report by Shah et al, which evaluated force- Thanks to Stefan Frembgen PhD, IngMar Medical, Pittsburgh, Pennsyl- dependent static dead space of face masks used with valved vania, for instruction and assistance with the Active Servo Lung 5000 holding chambers, reinforced the importance of both the mask design and the integrity of the mask/face seal.8 Themask’s ability to seal to the face was evaluated by apply- REFERENCES
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