Respiration During Exercise Part 2 W7 Flashcards
What are the 3 phases that the ventilatory response to constant load steady-sate exercise occurs?
Phase 1: Immediate increase in VE
Phase 2: Exponential increase in VE
Phase 3: Plaetau
What is hyperpnoea?
Defined as PaCO2 regulation due to proportional changes in alveolar ventilation (VA) and metabolic rate (VCO2)
What is the ventilatory threshold (Tvent)?
50-75% peak workload (VO2peak)
Lactate/anaerobic threshold
What is ventilation relationship with exercise intensity/workload?
Linear Increase
What is hyperventilation?
Decrease PaCO2
What is PaCO2?
Partial pressure of carbon dioxide
What happens to ventilation after reaching the ventilatory threshold?
It increases exponentially= hyperventilation
What is EIAH?
Exercise-induced arterial hypoxaemia
What is EIAH defined?
A reduction in Pa02 of >10mmHg from rest
What individuals experience EIAH?
Highly trained males during heavy exercise (50%)
Majority of females regardless of fitness or exercise intensity
What are the causes of exercise-induced arterial hypoxaemia?
1) Diffusion Limitation
2) V/Q mismatch
3) Relative hypoventilation
What is VT?
Tidal Volume
At the onset of exercise, how are changes in VE largely achieved?
Increasing tidal volume
What percentage does tidal volume not exceed vital capacity?
60%
What factors are well maintained when looking at breathing patterns until heavy exercise?
Arterial PO2, PCO2 and pH
What happens to VT and VE during heavy exercise?
VT= Plateaus
VE= Further increases due to increased feedback
How do we work out work in breathing?
Work=Pressure x Volume
What is work within breathing?
The sum of elastic, flow-resistive and inertial forces
What values can respiratory muscle work exceed?
500J/min
500mL O2/min
What is Oesophageal Pressure?
An estimate of pleural pressure and can be used to calculate the mechanical work of breathing during exercise
What is Poes?
Oesophageal pressure
What are the 3 main group of neurons?
Ventral respiratory group (inspiratory and expiratory)
Dorsal respiratory group (inspiratory)
Pontine respiratory group (modulatory)
What is the central controller of ventilation?
Brain stem (medulla and pons)
What are the motor outputs of control of ventilation?
Resistance muscles (cricoarytenoid)
Pump muscles (diaphragm)
What are the feedback inputs of the control of ventilation?
Peripheral/Central Chemoreceptors
Muscle afferents (peripheral neurogenic)
VO2 flow (peripheral neurogenic)
Where are peripheral chemoreceptors located?
The aortic arch and carotid body
What do peripheral chemoreceptors do?
Detect changes in PO2 of blood perfusing systemic and cerebral circulation
What does a decrease in PaO2 result in?
Increase in VE
What stimuli activate peripheral chemoreceptors?
Temperature
Adrenaline
CO2
Changes to PaO2 and VE
Where does peripheral chemoreceptors relay sensory information to?
Medulla (NTS) via vagus (CN X) and glossopharyngeal (CN IX) nerves
What are central chemoreceptors?
PCO2 sensors
What are peripheral chemoreceptors?
PO2 sensors
Where are central chemoreceptors located?
Primarily in the ventral surface of the medulla= retrotrapezoid nucleus
What is RTN?
Retrotrapezoid nucleus
What does an increase in PaCO2 result in?
Increase in VE
What is RTN sensitive too?
Changes in PaCO2 and H+
What is the ventilatory response like to O2?
Curvilinear
What is the ventilatory response to CO2 like?
Linear
What are the chronic training adaptions to endurance training which improves aerobic capacity?
Decreased metabolite accumulation
Decreased afferent feedback
Decreased ventilatory drive
What is the difference of VE between trained and untrained individuals during submaximal exercise?
20-30% lower in trained individuals
What are the respiratory structural adaptations to training?
NONE
What fine tunes exercise during moderate-intensity exercise?
Peripheral chemoreceptors
What are the respiratory functional adaptations to training?
Increased:
Ve/VO2
Respiratory muscle strength
Respiratory muscle endurance
How may the pulmonary system limit exercise performance? (5)
1) Exercise-induced arterial hypoxaemia (EIAH)
2) Exercise-induced laryngeal obstruction (EILO)
3) Expiratory flow limitation
4) Respiratory muscle fatigue
5) Intrathoracic pressure effects on cardiac output
