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Exercise Physiology > Exam 2- Lecture 7 > Flashcards

Exam 2- Lecture 7 Flashcards

1
Q

Primary functions of the respiratory response to exercise

A
  1. increase oxygen uptake to support accelerated cellular metabolism
  2. remove carbon dioxide produced as a result of accelerated cellular metabolism and as a result of buffering metabolic acids (lactic acid)
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2
Q

What components of the respiratory response to exercise should you consider?

A
  • mechanics of ventilatory response
  • gas exchange at the alveolus
  • oxygen transport in the blood
  • oxygen extraction at the muscle capillary/tissue interface
  • regulation of the ventilatory response
  • does Ve limit max aerobic capacity?
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3
Q

Inspiration during exercise

A
  • diaphragm flattens
  • active contraction of external intercostals and scaleni to move rib case upward
  • net effect is to increase volume of thoracic cavity, “sucking” air into lungs
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4
Q

expiration during rest and light exercise

A

passive recoil and relaxation of inspiratory muscles

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5
Q

expiration during increased intensity of exercise

A

active expiration

internal intercostals and abdominal muscles contribute to expiration by reducing thoracic volume

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6
Q

airway resistance during exercise

A
  • resistance in the airways affects the rate of airflow

- with exercise, airway resistance decreases due to bronchodilation

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7
Q

what is a very important determinant of airway resistance?

A

airway diameter

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8
Q

how does bronchodilation occur during exercise?

A

sympathetic NS –> release NE and circulating E from adrenals –> these catacholemines relax bronchial smooth muscle via beta-2 receptors

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9
Q

3 phases of exercise hyperpnea

A
  • there is a step increase in Ve at the onset of exercise (phase I; 0-15 s)
  • Phase I is followed by a slower, exponential rise in Ve (phase II, about 3 mins for submaximal exercise)
  • phase III occurs after 3 mins
  • if submaximal exercise is being performed, Ve will stabilize
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10
Q

ventilatory response to a graded exercise test

A
  • ventilation will continue to rise as workload increases
  • response is linear up to a point called the ventilatory threshold, at which point further increases in workload are accompanied by a disproportional increase in Ve
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11
Q

Components of Ve response

A

Ve=Vt x f
At rest, ventilation = 500 ml x 12 = 6 L/m
With maximal exercise, Vt is about 2 L or greater; f= 35-45 breaths/min or higher

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12
Q

maximal exercise Ve

A

about 100-120 L/min

17-20x resting

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13
Q

does exercise Vt ever exceed 60% of FVC?

A

rarely

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14
Q

at moderate levels of exercise, what causes most of the rise in Ve?

A

increase in Vt

some smaller contribution from f

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15
Q

what occurs once Vt = 50-60% of FVC?

A

Ve can only increase further by f

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16
Q

what regulates the combination of Vt and f necessary for a given Ve?

A

the brainstem

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17
Q

Why does tidal volume increase at the expense of IRV and ERV?

A

during exercise, you are inspiring to a greater volume and expiring to a small lung volume so that tidal volume increases
there is a greater dependence on changes in inspiratory volume

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18
Q

Ve = ?

A

Ve= Vd + Va

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19
Q

What is alveolar ventilation?

A

the portion of the insured air (Ve) that participated in gas exchange

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20
Q

at the same Ve, what provides more effective alveolar ventilation?

A

deeper breathing and lower f

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21
Q

what does deeper breath cause?

A

a larger portion of the tidal volume to enter and mix with alveolar air

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22
Q

FEV1% =

A

% of FVC expelled in 1 second

inversely related to airway resistance

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23
Q

what can FEV1% be used to detect?

A

exercise-induced bronchospasm

10-15% fall in FEV1% suggests airway obstruction due to bronchospasm

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24
Q

Gas exchange in the alveolus

A
  • Diffusion of O2 and CO2 across alveolar membrane and capillary walls is a function of the partial pressure differential, surface area for exchange, and thickness of membranes
  • Most healthy individuals maintain adequate gas exchange during heavy exercise
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25
Q

What occurs to PaO2, even in heavy exercise?

A

it is well-maintained

26
Q

what occurs to PaCO2 as intensity increases past moderate exercise?

A

decreases

27
Q

Diffusion of CO2 across alveolar membrane and capillary walls are a function of what?

A

pressure differential
membrane thickness
surface area

28
Q

Why is there a fall in PaCO2 at higher intensities of exercise?

A

look up recording

29
Q

why does mixed venous PCO2 increase with increasing intensity?

A

look up recording

30
Q

What is exercise-induced arterial hypoxemia associated with?

A
  • Increased ventilation/perfusion (V/Q) mismatch
  • Diffusion limitation: the high pulmonary blood flow decreases time available for gas transfer (AKA diffusion disequilibrium)
31
Q

Mild EIAH

A

SaO2: 93-95%

32
Q

Moderate EIAH

A

SaO2: 88-93%

33
Q

Severe EIAH

A

SaO2 < 88%

34
Q

when is supplemental O2 during exercise indicated?

A

in patients with pulmonary disease who have a rising SaO2 < 88%

35
Q

why might elite endurance athletes may experience arterial desaturation during maximal exercise

A
  • Most likely due to diffusion limitation due to an exceptionally fast transit-time of red blood cells through the pulmonary capillaries (incomplete gas exchange), secondary to extremely high cardiac output
  • Other factors: mechanical constraints on airflow and a less than maximal ventilatory response
36
Q

When is VO2 measurably affected?

A
  • When SaO2 reaches 3% below resting levels (1.5-2% decrease in VO2max for every 1% reduction in SaO2)
37
Q

how much can EIAH decrease VO2 max?

A

up to 15%

38
Q

What is the relevance of EIAH?

A
  • It can limit VO2max in healthy, active individuals, and this effect will be magnified in hypoxic environments, like altitude
39
Q

Who is most affected by altitude?

A

Those with higher VO2max

40
Q

When do person with pulmonary disease show EIAH?

A
  • At low work rates

- They require supplemental O2 during exercise

41
Q

What occurs to PO2 during exercise?

A

it is well maintained

42
Q

when does PaCO2 decrease?

A

when the lactate or ventilatory threshold is reached because ventilation increases out of proportion to the CO2 production

43
Q

when might arterial O2 desaturation occur?

A

At high work rates in some well-trained persons (especially at high altitudes) and at lower work rates in persons with pulmonary disease

44
Q

How is oxygen transported in the blood?

A

Hemoglobin

45
Q

O2 content =

A

(Hb concentration x 1.34 ml O2/g Hb x SaO2) + 0.003 PaO2

46
Q

a-v O2 difference =

A

CaO2 - CvO2

47
Q

What is the difference of Hb concentration between men and women?

A
  • Hb concentration is 5-10% lower in women

- This lower Hb contributes to lower aerobic capacity in women

48
Q

What does alterations in Hb concentration affect?

A 
O2 content 
(iron-deficiency anemia)
49
Q

What does interference of binding of O2 to Hb affect?

A

O2 content

smoking–carbon dioxide

50
Q

what drives unloading of O2 from Hb?

A

Low tissue PO2

51
Q

what is the a-v O2 difference at rest?

A

4-5 ml O2/100ml at rest

52
Q

what does exercise do to a-v O2 difference?

A

increases it up to 15-16 ml/100 ml

53
Q

What does decrease in tissue PO2 from 40 at rest to 15 mmhm during exercise do?

A

increases the pressure gradient, favoring release of oxygen from Hb

54
Q

What factor facilitate unloading of oxygen/shift O2 dissociation curve to the right?

A
  • lower pH
  • increase body temperature
  • increase carbon dioxide concentration
55
Q

what is 2,3 DPG and what does it do?

A

it is produced in red blood cells during glycolysis and facilitates unloading of oxygen from Hb (reduces affinity of Hb for O2)

56
Q

what results in chronically increased levels of 2,3 DPG?

A

altitude or chronic cardiopulmonary disease

57
Q

do males or females have a higher level of 2,3- DPG?

A

females

58
Q

What is myoglobin?

A

an oxygen-binding protein found in skeletal and cardiac muscle

59
Q

where is there more myoglobin?

A

in the “red” muscles

60
Q

does training enhance the cell store of myoglobin?

A

it is not clear

61
Q

When does myoglobin release the O2 that it is storing?

A

At very low O2 tensions
Ex: at very start of exercise and during intense exercise
Thought to help shutting O2 to mitochondria

Exercise Physiology (17 decks)

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