Effect of helium-induced ventilatory unloading on breathing and diaphragm EMG in awake ponies.
Abstract: Two questions were addressed in this study: 1) Does respiratory resistive unloading (inspired O2 fraction = 0.21, inspired He fraction = 0.79) elicit a compensatory reduction in stimulation of the diaphragm? 2) Do diaphragm and lung afferents contribute to compensatory responses to unloading? Ten intact (I), five diaphragm-deafferented (DD), four hilar nerve-denervated (HND), and seven DD+HND adult ponies were studied at rest and during mild and moderate treadmill exercise. During steady-state unloading at rest, duration of the diaphragm electromyogram (EMGdi) was less (P < 0.05) than control in I ponies, but there were no additional significant changes in breathing or blood gases. Unloading during mild and moderate exercise increased (P 0.05) among the groups. With unloading during exercise, arterial PCO2 was within 1 Torr of control except in the DD+HND ponies, which were 1-2 Torr hypocapnic (P < 0.05). During exercise, the duration and rate of rise of the EMGdi were reduced (P < 0.05) below control, beginning at about the third unloaded breath. The decrease in rate of rise was usually not sustained, inasmuch as there was a gradual return toward control over 2 min of unloading. There were no consistent group differences in these EMGdi responses. We conclude that resistive unloading during mild and moderate exercise in ponies results in a transient reduction in neural drive to the diaphragm that is not critically dependent on diaphragm and pulmonary afferents.
Publication Date: 1994-07-01 PubMed ID: 7961269DOI: 10.1152/jappl.1994.77.1.452Google Scholar: Lookup
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- Journal Article
- Research Support
- U.S. Gov't
- Non-P.H.S.
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This study investigated whether breathing easier due to inhaling helium gas causes a decrease in diaphragm stimulation and considered the role of diaphragm and lung nerve responses in this process. The research was carried out on ponies at rest and during mild and moderate exercise.
Overview of the Research
This study aimed to examine the effect of respiratory resistive unloading, induced by inhaling helium gas, on the stimulation of the diaphragm, and understand the role of diaphragm and lung nerve responses on the compensatory responses to unloading.
The effect of helium-induced ease of breathing on diaphragm stimulation and the role of diaphragm and lung nerve responses was studied on 26 ponies divided into four groups: ten intact, five with diaphragm nerve endings removed, four with lung nerve endings desensitized, and seven with both diaphragm and lung nerve endings altered. The studies were conducted while the ponies were at rest and during mild and moderate treadmill exercise.
Research Findings
- At rest, helium breathing led to a reduction in the time for which the diaphragm muscle was active in the intact ponies only. No other changes in the respiration rate, blood gas levels or diaphragm activity were observed.
- Different levels of exercise led to an increase in the amount of air breathed in and out by all ponies, with no significant variance between the different groups.
- When the ponies exercised while breathing helium, the level of carbon dioxide in their arteries was at control levels, with the exception of the ponies who had both diaphragm and lung nerve endings altered but were significantly below this level.
- The time of diaphragm activity and the rate of diaphragm stimulation started decreasing from the third breath taken by the ponies during exercise, but this decrease was not sustained as the rates gradually returned to control levels within 2 minutes of unloading.
Conclusions
- The study concluded that breathing helium during mild and moderate exercise in ponies results in a temporary decrease in neural drive to the diaphragm. This means that the signals the nervous system sends to stimulate the diaphragm decreases, essentially reducing its workload.
- This reduction in neural drive to the diaphragm was not found to be critically dependent on the nerve endings in the diaphragm or the lungs.
Cite This Article
APA
Forster HV, Erickson BK, Lowry TF, Pan LG, Korducki MJ, Forster AL.
(1994).
Effect of helium-induced ventilatory unloading on breathing and diaphragm EMG in awake ponies.
J Appl Physiol (1985), 77(1), 452-462.
https://doi.org/10.1152/jappl.1994.77.1.452 Publication
Researcher Affiliations
- Department of Physiology, Medical College of Wisconsin, Milwaukee.
MeSH Terms
- Animals
- Blood Gas Analysis
- Carbon Dioxide / blood
- Diaphragm / innervation
- Diaphragm / physiology
- Electrodes, Implanted
- Electromyography
- Esophagus / physiology
- Helium
- Horses
- Muscle Denervation
- Neurons, Afferent / physiology
- Respiratory Mechanics / physiology
Grant Funding
- HL-25739 / NHLBI NIH HHS
Citations
This article has been cited 3 times.- Segizbaeva MO. Loading and unloading breathing during exercise: respiratory responses and compensatory mechanisms. Eur J Med Res 2010 Nov 4;15 Suppl 2(Suppl 2):157-63.
- Ogawa T, Calbet JA, Honda Y, Fujii N, Nishiyasu T. The effects of breathing a helium-oxygen gas mixture on maximal pulmonary ventilation and maximal oxygen consumption during exercise in acute moderate hypobaric hypoxia. Eur J Appl Physiol 2010 Nov;110(4):853-61.
- Ansley L, Petersen D, Thomas A, St Clair Gibson A, Robson-Ansley P, Noakes TD. The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal performance of exercise in well-trained athletes. Br J Sports Med 2007 Jan;41(1):2-7.
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