Respiration during Exercise (2) Flashcards

1
Q

What are the 3 phases in the ventilatory response to constant load steady-state exercise?

A

o Phase 1: Immediate increase in VE
o Phase 2: Exponential increase in VE
o Phase 3: Plateau

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2
Q

What is hyperpnoea?

A

Hyperpnoea - PaCO2 regulation due to proportional changes in alveolar ventilation (VA) and metabolic rate (VCO2)

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3
Q

How does ventilation increase during incremental exercise? When does this stop?

A

Linearly - until a point commonly referred to as the ventilatory threshold (lactate/anaerobic threshold)

  • this occurs at 50-75% of peak workload (VO2 peak).
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4
Q

What happens after ventilatory threshold is reached?

A

VE increases exponentially, resulting in hyperventilation (decreases PaCO2)

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5
Q

What is exercise-induced arterial hypoxaemia (EIAH)?

A

The reduction in Pa02 of ≥10 mmHg from rest
- Occurs in highly trained males (50%) during heavy exercise and the majority of females regardless of fitness or exercise intensity.

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6
Q

Why is EIAH theorised to occur?

A

Because ventilatory demand exceeds capacity (demand vs capacity theory)

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7
Q

Although not fully understood, what are understood to be the 3 causes of EIAH?

A
  1. Diffusion limitation
  2. V/Q mismatch
  3. Relative hypoventilation
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8
Q

What are changes in VE achieved by at the onset of exericse?

A

Increasing tidal volume

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9
Q

During heavy exercise, tidal volume plateaus and further increases in VE are achieved by..?

A

Increased breathing frequency

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10
Q

Tidal volume does not exceed ? of vital capacity?

A

60%

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11
Q

Work = ? x ?

A

Work = force x volume
Applied to breathing: work = pressure x volume

Total work is the sum of elastic, flow-resistive, and inertial forces

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12
Q

How do you work out mechanical work of breathing during exercise?

A

By using oesophageal pressure (Poes)
- an estimate of pleural pressure

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13
Q

Where are respiratory central patterns located?

A

Within the brainstem (pons and medulla)

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14
Q

What are the 3 main groups of neurons?

A

o Ventral respiratory group (inspiratory and expiratory)
o Dorsal respiratory group (inspiratory)
o Pontine respiratory group (modulatory)

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15
Q

The control of ventilation has a 3-compartmental model. What are the 3 compartments of this model?

A
  • Central controlled (pons, medulla, other parts of brain)
  • Effectors (respiratory muscles)
  • Sensors (chemoreceptors, lung, + others)
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16
Q

Where are peripheral chemoreceptors located?

A

Aortic arch + carotid body
- These detect changes in P02 of blood perfusing systemic and cerebral circulation

Relays sensory info to the medulla via vagus and glossopharyngeal nerves

Other stimuli also activate peripheral
chemoreceptors, such as temperature,
adrenaline and CO2

17
Q

Where are central chemoreceptors located?

A

Central chemoreceptors are located primarily in the ventral surface of the medulla, known as the retrotrapezoid nucleus (RTN).

The RTN is sensitive to change in PaCO2/H+
o Many other brain sites are also sensitive to CO2, such as the NTS, locus coeruleus, raphe, and cerebellum

18
Q

Describe the chemoreceptor feedback

A
  1. Chemoreceptors detect error signals (disturbances to blood gas homeostasis)
  2. Central and peripheral chemoreceptors increase afferent
    input to the brainstem in response to increasing PaCO2or decreasing PaO2or pH
  3. Premotor neurons in the dorsal respiratory group are activated
  4. Inspiratory muscle contract, increasing VE
  5. Changes in VE elicit changes in PaO2, PaCO2and pH, thus restoring blood-gas balance
19
Q

How does the ventilatory response to O2 and CO2 different?

A

O2 - curvilinear
CO2 - linear

20
Q

Is there a change in PaCo2 during moderate exercise?

A

No change in mean PaCO2 during moderate exercise, primary exercise stimulus must be feedforward in origin.

21
Q

What fine-tunes breathing during mod-intensity exercise?

A

Peripheral chemoreceptors

22
Q

What happens to PaCO2 during severe exercise?

A

Falls and inhibits breathing
- additional sources of ventilatory stimulus come from increased body temp and augmented muscle afferent input.

23
Q

What is the difference in ventilation during submaximal exercise between trn and untrn individuals?

A

Ventilation is 20-30% lower during submaximal exercise in trained versus untrained individuals.

24
Q

What are 3 chronic training adaptations that improve aerobic capacity?

A
  • decreased metabolite accumulation
  • decreased afferent feedback
  • decreased ventilatory drive
25
Q

DO the lungs adapt to exercise training?

A

With few exceptions, the lungs and airways don’t adapt to physical training
- airways and lungs do not get bigger
- diffusing capacities are unchanged

Respiratory muscles may becomes stronger and more fatigue resistant.

26
Q

What are 5 examples of how the pulmonary system may limit exercise performance?

A
  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