"With some masks, the amount of medicine available to the youngest children is severely decreased because of mask size, stiffness, and poor fit on the face," said Bruce Rubin, M.D., a professor of pediatrics. Rubin is a pediatric pulmonary specialist, a professor of biomedical engineering in the Wake Forest-Virginia Tech Biomedical Engineering & Sciences, and an aerosol scientist.
The researchers studied seven masks used in combination with pressurized metered-dose inhalers to deliver asthma medicine to children. The medication goes into a chamber attached to the mask and is then inhaled by the child. When the mask is placed on the child's face, some air still remains in the mask, which is called dead space volume.
The researchers found that some masks don't fit well or have too much dead space volume. "Dead space volume in the mask contains drug that doesn't get into the lung with each breath," said Rubin.
The seven masks evaluated were those used with the Aerochamber, Optichamber, Easivent, BreatheRite, Ace, Pocket Chamber and Vortex inhalers. The investigators measured mask volume by filling them with water after sealing the outlet end. Then, using an infant-sized mannequin head that is used to teach cardiopulmonary resuscitation, they measured the dead space volume of the masks.
This was done by placing the water-filled mask on a device that measures applied force and pushing the mannequin face into it with a controlled force of 1.5, 3, or 7 pounds to match the range of forces used by parents when applying the mask. The face displaced water from the masks. With masks that fit better on the face and were flexible, more water was pushed out at each force and less remained in the mask as dead space volume.
The researchers also measured how well the mask fit on the face by analyzing digital photographs to determine if there was any leak.
Dead space volume ranged from 20 ml to 100 ml – with the higher number meaning that less medicine gets to the lungs. Only the Aerochamber, Optichamber and the Vortex had dead space volume that was low enough for the mask to be emptied with the normal breathing of a six-month-old infant.
The poorest fit and biggest leak was with the Vortex, Pocket Chamber and BreatheRite masks. In fact, the Pocket Chamber was too stiff to seal at any force.
"The seal between the mask and the face is critical for drug delivery," said Rubin. "If the mask doesn't fit tightly enough, you're sucking in air from outside the mask that contains no medicine," said Rubin. He advised parents to check masks to make sure they fit comfortably.
The group didn't study the drug delivery, which is the ultimate test of effectiveness. This summer, they plan to do studies in children to evaluate how effectively medication is getting to the lungs.
Asthma is one of the most common chronic diseases of childhood. According to the American Lung Association, about 4 million children under 18 years old have had an asthma attack in the past 12 months, and many others have "hidden" or undiagnosed asthma.
Co-researchers were Samir Shah, with the Department of Biomedical Engineering at Wake Forest, and Ariel Berlinski, M.D., with Arkansas Children's Hospital.
Wake Forest University Baptist Medical Center is an academic health system comprised of North Carolina Baptist Hospital and Wake Forest University Health Sciences, which operates the university's School of Medicine. U.S. News & World Report ranks Wake Forest University School of Medicine 30th in primary care, 41st in research and 14th in geriatrics training among the nation's medical schools. It ranks 32nd in research funding by the National Institutes of Health. Almost 150 members of the medical school faculty are listed in Best Doctors in America.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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