Featured Research

from universities, journals, and other organizations

Preventing Ventilation Induced Lung Injury Depends On Giving The Right Number Of 'Sighs'

Date:
July 25, 2006
Source:
American Physiological Society
Summary:
Periodic deep inflation (akin to a sigh) combined with low tidal volume provides the best balance between keeping the lung open and preventing ventilator-induced lung injury, a study of ventilation therapy shows. The study with mice also clearly demonstrates that there is an optimal number of deep inflations. Ventilation therapy is used with patients who cannot breathe on their own because of trauma, lung injuries and chronic lung disease.

Ventilation therapy burst into the public consciousness more than 60 years ago with the "iron lung" and the polio epidemic. Mechanical ventilation has come a long way since then and is used today with patients who cannot breathe on their own because of trauma, lung injuries and chronic lung disease.

But ventilation demands a delicate balance between over inflating and under inflating the lungs, either of which can lead to further injury. Researchers have found that pumping too much air overdistends the lung, leading to ventilator-induced lung injury (VILI).

Doctors currently use small amounts of air (low tidal volume) to protect against VILI. But low tidal volumes can lead to progressive closure of the lungs' air cells, called alveoli, reducing the lung's ability to exchange gases. One way to reverse closure of the alveoli is to periodically give a more robust puff of air, known as deep inflation.

A new study in the online edition of the American Journal of Physiology-Lung Cellular and Molecular Physiology shows that low tidal volume combined with periodic deep inflation provides the best balance between keeping the lung open and preventing VILI in mice. And, using mice, these researchers have shown for the first time that although deep inflation is necessary, it can be overdone.

"There is still a lot of controversy and uncertainty about how best to ventilate the lung," said the study's senior author, Jason HT Bates of the University of Vermont. "One controversy is whether deep inflations, the "sighs" that each of us takes periodically, should ever be given, and if so, how frequently."

Researchers find optimal range

"This study demonstrates that an optimal frequency range of deep inflation delivery exists, at which point the potentially injurious effects of overdistention are outweighed by the protective benefits of maintaining a predominantly open lung," wrote Gilman B. Allen, Benjamin T. Suratt, Lisa Rinaldi, Joseph M. Petty and Bates in the AJP-Lung paper entitled "Choosing the frequency of deep inflation in mice: balancing recruitment against ventilator-induced lung injury."

Allen, a medical doctor with Fletcher Allen Health Care and the University of Vermont department of medicine, has treated patients on ventilation. Bates is a University of Vermont department of medicine researcher interested in lung physiology.

Ventilators are commonly used in hospital intensive care units with a variety of patients, including those with acute lung injury, acute respiratory distress syndrome, pneumonia, septic shock, trauma, aspiration of vomit and chemical inhalation. As a result of these conditions, fluid can build up in the lungs, blocking the alveoli. This causes the body to mount an inflammatory response, which injures the lung's epithelial lining, Bates said. At that point, doctors provide mechanical ventilation in the intensive care unit until the body heals itself.

Bates explains the difficulty of treating the injured lung this way: "Imagine you have two balloons which you fill by pumping in air. Now imagine you have only one balloon, and you must drive the same volume of air into the one balloon as you did into two," Bates explained. The same thing happens in the lungs. When parts of the lungs are no longer working, it places greater pressure on the portions of the lung that are working, with the remaining lung handling the air pressure that two lungs had handled.

Doctors consider tidal volume (the amount of air an individual normally inhales and exhales), deep inflation frequency (the number of deep breaths given) and PEEP (positive end-expiratory pressure), which helps keep lungs from collapsing by preventing the airways from emptying completely. PEEP also helps improve gas exchange within the lungs.

Low tidal volume, varied sigh rate

The researchers divided mice into three experimental groups. All three groups received PEEP and low tidal volume air. Each group was ventilated for two hours. The experimental groups differed according to how many deep inflations they received. They were as follows:

* HV (high volume) received one deep inflation each breath

* LV (low volume) received two deep inflations each hour

* LVDI (low volume deep inflation) received two deep inflations each minute

In addition, there were two control groups -- a surgical sham, which received no ventilation, and a group that received deep inflation every breath and no PEEP.

The study found that:

* The lungs of the mice given two big breaths every minute (LVDI) remained more open and functioned better than the LV and HV.

* The lungs of the mice that received only two deep breaths per hour (LV) became stiff and portions of the lungs collapsed. However, lung function returned briefly to normal when the mice received their infrequent deep inflations. This suggests that the lungs self-repair after the deep inflation, at least over the course of the first two hours.

* The lungs of the mice that received deep inflation every breath (HV) suffered overdistention injury to their lungs. This group was akin to a high tidal volume group, once again demonstrating that low tidal volume is safer.

* The control group that received high tidal volume but no PEEP showed the highest evidence of injury, even higher than the high tidal volume group. This indicates that PEEP helps reduce the negative effects of frequent deep inflation.

"We demonstrated it's possible to give deep breaths too frequently and too seldom," Bates explained. The middle ground -- two deep inflations per minute -- provides the most benefit to the mice we studied without injuring the lungs, he said.

"We conclude that frequent deep inflation can safely improve gas exchange and lung mechanics and may confer protection from biotrauma," the authors wrote. "Differences between LVDI and HV suggest that an optimal frequency range of deep inflation exists, within which the benefits of maintaining an open lung outweigh injury incurred from over-distention."

Next step

"Our findings have obvious implications for the recruitment of the injured human lung during low tidal ventilation," the authors wrote. "However, extrapolating our results to the clinical situation must be done guardedly. In the present study we employed uninjured mice, whereas it is known that the injured lung is more prone to atelectasis (collapse) than a normal lung."

Bates' team hopes to move to a human trial in the near future, now that they have established that deep inflation is beneficial and can be delivered with an optimal frequency.

Source

"Choosing the frequency of deep inflation in mice: balancing recruitment against ventilator-induced lung injury," by Gilman B. Allen, Benjamin T. Suratt, Lisa Rinaldi and Joseph M. Petty and Jason HT Bates, Vermont Lung Center, Department of Medicine, University of Vermont, Burlington. Allen, Suratt and Bates are also affiliated with the Fletcher Allen Health Care, Burlington. The study appears in the online edition of American Journal of Physiology Lung Cellular and Molecular Physiology published by The American Physiological Society.

Funding

The study was funded by grants from the National Institutes of Health's Centers of Biomedical Research Excellence and GlaxoSmithKline.


Story Source:

The above story is based on materials provided by American Physiological Society. Note: Materials may be edited for content and length.


Cite This Page:

American Physiological Society. "Preventing Ventilation Induced Lung Injury Depends On Giving The Right Number Of 'Sighs'." ScienceDaily. ScienceDaily, 25 July 2006. <www.sciencedaily.com/releases/2006/07/060725091950.htm>.
American Physiological Society. (2006, July 25). Preventing Ventilation Induced Lung Injury Depends On Giving The Right Number Of 'Sighs'. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2006/07/060725091950.htm
American Physiological Society. "Preventing Ventilation Induced Lung Injury Depends On Giving The Right Number Of 'Sighs'." ScienceDaily. www.sciencedaily.com/releases/2006/07/060725091950.htm (accessed July 23, 2014).

Share This




More Health & Medicine News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Courts Conflicted Over Healthcare Law

Courts Conflicted Over Healthcare Law

AP (July 22, 2014) Two federal appeals courts issued conflicting rulings Tuesday on the legality of the federally-run healthcare exchange that operates in 36 states. (July 22) Video provided by AP
Powered by NewsLook.com
Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Scientists Find New Way To Make Human Platelets

Scientists Find New Way To Make Human Platelets

Newsy (July 22, 2014) Boston scientists have discovered a new way to create fully functioning human platelets using a bioreactor and human stem cells. Video provided by Newsy
Powered by NewsLook.com
Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

TheStreet (July 21, 2014) New research shows Gilead Science's drug Sovaldi helps in curing hepatitis C in those who suffer from HIV. In a medical study, the combination of Gilead's Hep C drug with anti-viral drug Ribavirin cured 76% of HIV-positive patients suffering from the most common hepatitis C strain. Hepatitis C and related complications have been a top cause of death in HIV-positive patients. Typical medication used to treat the disease, including interferon proteins, tended to react badly with HIV drugs. However, Sovaldi's %1,000-a-pill price tag could limit the number of patients able to access the treatment. TheStreet's Keris Lahiff reports from New York. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins