Document Detail

Effects of pregnancy, obesity and aging on the intensity of perceived breathlessness during exercise in healthy humans.
MedLine Citation:
PMID:  19450766     Owner:  NLM     Status:  MEDLINE    
The healthy human respiratory system has impressive ventilatory reserve and can easily meet the demands placed upon it by strenuous exercise. Several acute physiological adaptations during exercise ensure harmonious neuromechanical coupling of the respiratory system, which allow healthy humans to reach high levels of ventilation without perceiving undue respiratory discomfort (breathlessness). However, in certain circumstances, such as pregnancy, obesity and natural aging, ventilatory reserve becomes diminished and exertional breathlessness is present. In this review, we focus on what is known about the mechanisms of increased activity-related breathlessness in these populations. Notwithstanding the obvious physiological differences between the three conditions, they share some common perceptual and ventilatory responses to exercise. Breathlessness intensity ratings (described as an increased "sense of effort") are consistently higher than normal at any given submaximal power output; and central motor drive to the respiratory muscles is consistently increased, reflecting increased ventilatory stimulation. The increased contractile respiratory muscle effort required to support the increased ventilatory requirements of exercise remains the most plausible source of increased activity-related breathlessness in pregnant, obese and elderly humans. In all three conditions, static and dynamic respiratory mechanical/muscular function is, to some extent, altered or impaired. Nevertheless, breathlessness intensity ratings are not significantly increased (compared to normal) at any given exercise ventilation in any of these three conditions. This strongly suggests that respiratory mechanical/muscular factors, per se, may be less important in the genesis of breathlessness. Moreover, in pregnancy and obesity, we present evidence that effective physiological adjustments exist to counterbalance the potentially negative sensory consequences of the altered respiratory mechanical/muscular function peculiar to these conditions.
Dennis Jensen; Dror Ofir; Denis E O'Donnell
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Publication Detail:
Type:  Editorial; Research Support, Non-U.S. Gov't; Review     Date:  2009-02-07
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  167     ISSN:  1878-1519     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2009 May 
Date Detail:
Created Date:  2009-05-19     Completed Date:  2009-08-18     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  87-100     Citation Subset:  IM    
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MeSH Terms
Aging / physiology*
Dyspnea / physiopathology*,  psychology
Exercise / physiology*,  psychology
Obesity / physiopathology*
Perception / physiology
Pregnancy / physiology*
Respiratory Mechanics / physiology

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