lecture 2. respiratory control & adaptations

8/14/2019 Lecture 2. Respiratory Control & Adaptations

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All Slides Greg D. Wells, Ph.D. (2009), All Rights ReservedWeb: www.per4m.ca Email: [email protected] Tel: 416-710-4618

Greg Wells, Ph.D.The University of Toronto

www.per4m.ca


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Part 1: The Ventilatory Responseto Exercise

Greg D. Wells, Ph.D. (2009)


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Organization of the Control of Breathing

Respiratory Rhythm Generator

(pre-Botz, VRG, NA)

Spinal Motoneurones (via

VRG & DRG)

Respiratory Muscles Lung (Pulmonary Ventilation)

Peripheral Chemoreflexes &

Lung / Airway Afferents

Nucleus of the Solitary TractReticular Activating System(Reticular Formation & Raphe)

Central Command

Central Chemoreflex

Afferent Feedback (Limbs)

Feed Forward Feed Back



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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Wakefulness drive (cerebralcortex)

Movements signals

(cerebellum)

Type III, IV afferents (MSNA

hypothesis)

H+, PCO2, SID

(medullary surface)

H+, PCO2, PO2, K+, La-

(carotid body)

Pulmonary stretch receptors

PCO2, PO2*

*

*

Basal ventilation

(medulla)

Cross-activation

(neuronal network)

Drives to Ventilation

* Greg D. Wells, Ph.D. (2009)


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Physiology During Incremental Exercise



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Ventilation During Constant Load Exercise

Mateika, J. H. and J. Duffin (1995). A review of the control of breathing during exercise. Eur J Appl

Physiol 71(1): 1-27.

*

*

*

*


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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Wakefulness drive (cerebralcortex)

Movements signals

(cerebellum)

Type III, IV afferents (MSNA

hypothesis)

H+, PCO2, SID

(medullary surface)

H+, PCO2, PO2, K+, La-

(carotid body)

Pulmonary stretch receptors

PCO2, PO2*

*

*

Basal ventilation

(medulla)

Cross-activation

(neuronal network)

Drives to Ventilation

*

* Shows areas where

training may have

an effect.



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Part 2: Adaptations of theRespiratory System to Training



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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Adaptation #1: Peripheral Chemoreflex



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Ventilation vs. Predicted PCO2

0

10

20

30

40

50

60

70

80

30 35 40 45 50 55 60

Predicted PCO2 (mmHg)

VentilationBTPS(L. min-1)

Basal Ventilation

1st VE Threshold

2nd VE Threshold

1st VE Sensitivity

2nd VE Sensitivity



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Ventilation vs. End-Tidal PCO2

0

10

20

30

40

50

60

70

30 35 40 45 50 55

End-Tidal PCO2 (mmHg)

Ventilation

BTPS(L. min-1)

Pre-training

Pre-training fitted

Post-training

Post-training fitted

Example of typical chemoreflex response pre- and post-training. The increase in

chemoreflex threshold is indicated.

EV ThresholdsChemoreflex



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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Exercise Limiting Factors

Exercise induced arterial hypoxemia Increased work of breathing Respiratory muscle fatigue Dyspnoea

Adaptation #1: Peripheral Chemoreflex



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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Adaptation #2: Pulmonary Function



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Results Pulmonary FunctionFEV - 1

3.0

3.2

3.4

3.6

3.8

4.0

4.2

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Time (wk)

Volume(L)

F E: T2 - T3 *

F E: T2 - T4 *

F C: T2 - T4 *

F C: T2 - T3 *

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Time (wk)

Volume(L)

*

F E: T2 - T4 *

F E: T2 - T3 *

FIV - 1



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Results Pulmonary FunctionForced Vital Capacity

3.5

3.7

3.9

4.1

4.3

4.5

4.7

4.9

5.1

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Time (wk)

VitalCapa

city(L)

F E: T2 - T3 *

F C: T2 - T3 *

F C: T2 - T4 *

F E: T2 - T4 *

Audrey Ferreras

She reached a depth of 412.5

feet (125 meters) in 2minutes, 3 seconds. Greg D. Wells, Ph.D. (2009)


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(pre-Botz, VRG, NA)


VRG & DRG)




Nucleus of the Solitary Tract

Reticular Activating System

(Reticular Formation & Raphe)

Central Command

Central Chemoreflex


Performance Limiting Factors


Adaptation #2: Pulmonary Function



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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Adaptation #3: Respiratory Muscle Function



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Back


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Mechanics at Rest

-6 -2-10 -832

36

40

44

48

52

% VC

Intrapleural Pressure cm H 2O

-6 -4 -2 0 -10 -8 -4 0

lung lungthorax

wall

INSPIRATION EXPIRATION

thorax

wall



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Mechanics During ExerciseW to overcome ER Lungs W to overcome ER CW

W to overcome FR CWW to overcome L flow resist.



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RMT Mechanisms: Q Legs

Harms, C. A., M. A. Babcock, et al. (1997). Respiratory muscle work compromises leg blood flow

during maximal exercise. J Appl Physiol 82(5): 1573-83.


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(pre-Botz, VRG, NA)


VRG & DRG)







Central Command

Central Chemoreflex

Afferent Feedback (Limb & RM)



Adaptation #3: Respiratory Muscle Function



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(pre-Botz, VRG, NA)


VRG & DRG)


Peripheral Chemoreflexes&





Central Command

Central Chemoreflex




Adaptation #4: Dyspnoea



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Pulmonary stretch

receptors

Central & peripheral

chemoreceptorsType I afferents M+ spindles

(length ~ volume)

Type II afferents GTO (tension

~ pressure: Pdi / Pmax)

Type III afferents M+ spindles

(contraction ~ V, Fb, Ti:Te)

Type IV afferents M+ spindles

(metaboreceptors ~ H+, K+)

Dyspnoea Mechanisms



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Dyspnoea Typical Application



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Pulmonary stretch

receptors

Central & peripheral

chemoreceptors

Type I afferents M+ spindles(length ~ volume)

Type II afferents GTO (tension

~ pressure: Pdi / Pmax)

Type III afferents M+ spindles

(contraction ~ V, Fb, Ti:Te)

Type IV afferents M+ spindles(metaboreceptors ~ H+, K+)

Pathogenesis of Dyspnoea

Hypoxia / hypercapnia

Dynamic hyperinflation



(lose mechanical adv)

RM weakness (Pmax)

Hyperventilation

RM fatigue



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(pre-Botz, VRG, NA)


VRG & DRG)





Central Command

Central Chemoreflex


Summary


lecture 2. respiratory control & adaptations

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