Vol. 18 •Issue 20 • Page 25
PF Extremes:
On mountain peaks and ocean canyons, researchers look at pulmonary function levels
Listening to coaches screaming at their patients to exhale as hard as they possibly can is probably fairly common in our world of respiratory care. To an outsider, the yelling might appear to be verbal abuse rather than our tactical maneuver to obtain accurate pulmonary mechanics.
In the same vein, incarcerating someone in a body box may also appear an odd way to measure their breathing.
Whatever the rationale, pulmonary function testing has come a long way since the days we used basic peak flow meters to measure capacity to today’s use of full spirometry testing and diffusion studies for capturing a more complete record.
Pulmonary function testing is a state-of-the art diagnostic procedure used to determine the presence of respiratory diseases or disabilities. We routinely analyze the results of a patient’s performance by reviewing a number of graphics and numerical data and comparing them to predicted values in order to access the patient’s respiratory status. Over a period of time, this routine type of testing can become robotic and often boring. But the routine changed when we started looking at the lung capacities of individuals who typically go to regions where few other people dare to venture.
Why do we do it? Simple. We want to look at conditions like lung barotrauma, a serious condition we can encounter among accident victims and sports enthusiasts. The causes are typically the same and can be easily found among those hearty individuals in Hawaii known as free divers who challenge the laws of physics by speed dialing themselves into the extreme depths of the ocean while holding their breath.
This is where the rubber meets the road in terms of the lungs meeting some unusual atmospheric pressures.
Beneath Hawaiian Waves
Lung squeeze, an occupational hazard among Hawaii’s free divers, is serious. Divers with lung squeeze typically begin to feel a mild discomfort followed by wheezing, followed by their detecting blood in the sputum. Lung squeeze occurs when divers fail to pay attention to their body’s reaction to rapid changes in pressure as they plunge to deep depths below the ocean surface.
They learn the hard way that holding their breath long enough for them to reach a targeted depth is risky business, especially when they are holding on to a sled of weights spiraling down into a watery abyss.
Free diving is nothing new. It has been practiced for more than 2,000 years. What is new about free diving is it has now become an extreme sport with a common fundamental principle of maintaining thoracic integrity at great depths. How does a free diver achieve this?
“Packing it” or “buccal pumping” is a technique that allows a diver to build up a hyper-inflated lung volume. To attain this level, a diver gasps air into his mouth while the glottis is closed after already attaining a completed maximum inspiration. The diver then initiates a swallowing maneuver when the glottis is open due to positive oral pressure, allowing the air to be forcefully pumped into the lungs.
This maneuver is repeated until approximately 1.5 liters is added to the total lung capacity (TLC). The additional lung capacity can make the difference as a free diver attempts to set a new world record for diving to great depths and making it back to the surface alive.
Anyone for Climbing?
Underwater lung capacity is just part of the picture. Those who attempt to climb Mount Everest must work to develop top physical and mental training and to instill an absolute resolve if they hope to successfully reach the top.
Once a climber departs from the normal surroundings of sea level, certain physical laws and conditions begin to react with the human body.
Various studies have been conducted to monitor and evaluate respiratory functions among mountain climbers. The studies have been set up as a way to observe the effects of high altitude exposure as climbers charge up the mountain.
Researchers have already determined that Forced Vital Capacity (FVC) declines with altitude exposure as does Forced Expiratory Volume in one second ( FEV1). Peak expiratory flows increase moderately as does the reserve volume (RV). Meanwhile, the Total Lung Capacity (TLC) changes little.
Because of the nature of this extreme sport, questions of pathophysiology arise. The mechanism for changes observed in the pulmonary functions include pulmonary interstitial edema, pulmonary vasoconstriction, redistribution of pulmonary blood volume and regional changes in lung elastic recoil.
There are some serious potential ramifications for those who choose to place their bodies in nature’s way as they hit the slopes.
The Final Frontier
Space, the final frontier, offers scientists a unique opportunity to study how the human body reacts to a combination of extreme speeds and high altitudes. Fortunately, astronauts can take advantage of high tech pressurized suits to assist them during space flights.
During Skylab and Apollo-Soyuz missions, researchers gathered detailed data on residual volume determination (RV), closing volume (CV), Vital Capacity (VC), Forced Vital Capacity (FVC) and its derivatives as explorers moved from one atmospheric pressure to another. Readings were taken all along the way in order for researchers to compare pre-flight, in-flight and post-flight changes. Researchers learned vital capacity (VC) was decreased slightly (-10 percent) while no other major pre- to post-flight changes were observed.
Receiving and collecting clinical data from astronauts while they travel at extreme speeds and far distances is becoming easier due to the advancements in telemedicine which has been a part of medicine’s technical arsenal for years.
Pulmonary function during high altitude exposure is a significant clinical concern because of the changes in lung function which impacts the severity of hypoxemia. The decline in lung function reduces ventilatory reserves which are required to support exercise and may result in altitude sickness.
Millions of people are engaged in occupational or the more leisurely endeavors, so it is important to know what activities might impact the individual the most.
Problems of the Obese
Extreme sports and unusual working conditions are only part of the picture when it comes to looking at pulmonary function and its importance. One activity which has become a national concern is lung function during eating. Why is it important to look at this particular aspect of lung function? It is increasingly becoming vital because our population is moving into an overweight category. Being overweight can be a chronic condition requiring long-term management and often result in medical intervention.
About 97 million Americans (more than a third of the adult population) are overweight or obese, with 5 to 10 million of those in the morbidly obese category, defined as being 100 pounds or more over ideal body weight. This extreme condition is considered life-threatening because the excessive weight can contribute to a highly restrictive lifestyle.
It is generally accepted that respiratory compliance diminishes as body weight increases. In fact, there could be as much as a 30 percent reduction in extreme cases where low compliance is associated with reduced vital capacity and reduced gas exchange. This can also contribute to a reduced expiratory reserve volume and functional residual capacity because of the impact of excessive weight on chest wall mechanics.
In the United States, somewhere between 20 and 27 percent of all children and adolescents suffer from obesity.
Studies have indicated that as many as 58 percent of the overweight children tested had abnormal pulmonary function studies, primarily obstructive in nature. Maximum voluntary ventilation was decreased, as was the expiratory reserve volume.
Some researchers believe this is the result of a mass effect on the position of the diaphragm to include the impact on its mobility, decreased respiratory compliance, decreased respiration, muscle strength and fatty infiltration to the respiratory muscles.
It has often been said that the ocean and the air are very safe but terribly unforgiving. That can also be said of the extreme ranges, the mountain peaks and the ocean canyons. Even when we are not looking at the extremes, we simply die if we lack oxygen or the ability to process it in our lungs.
If my mid-life crisis took a turn for the worst and I decided to climb Mt. Kilimanjaro, my understanding of the mountain’s capabilities and my pulmonary status and limitations would be a priority and not something left to chance.
Michael Donnellan is a California practitioner.
