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Physiology Test 2 > Journal > Flashcards

Journal Flashcards

1
Q

Definition Of VO2max?

A

The fastest rate at which the body can utilise O2 during heavy exercise is defined as the maximum rate of oxygen uptake (VO2max),

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2
Q

What Is VO2max An Indicator Of?

A

(VO2max) which is an index of maximal cardiovascular function, provided pulmonary function and ambient O2 concentration are normal.

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3
Q

How Is Fatigue Indicated In Normal Conditions?

A

Fatigue is often preceded by a plateau or even a decline in V˙ O2max.

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4
Q

Aim Of The Study?

A

To identify the primary factor that limits VO2max in healthy trained humans
Another aim was to determine the mechanisms
underlying the blunted VO2max and early fatigue associated with heat stress

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5
Q

Participant Information?

A

8 Healthy Trained Individuals
24”4 years, 78.1”7.4 kg, 9.8”0.9 kg, 181”5 cm,
191”6 bpm, and 4.7”0.5 L/min

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6
Q

How Was VO2 Measured?

A

Pulmonary VO2 was measured online with an Applied Electrochemistry OCM-2 metabolic cart

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7
Q

How Was Cardiac Output Measured?

A

Cardiac output was measured by indocyanine (ICG, Akon Inc) dye dilution.1

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8
Q

How Was Arterial Blood Pressure Measured?

A

Blood pressure was continuously monitored from the femoral artery

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9
Q

VO2max In H & N?

A

VO2max and time to fatigue were significantly diminished in H compared with N

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10
Q

What Are The Four Components Of Respiration?

A

Pulmonary Ventilation
External respiration
Transport Of respiratory gases
Internal respiration

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11
Q

Why Does Air Move Into The Lugs?

A

Due to inspiration and expiration

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12
Q

Mechanics Of Breathing

A

Inspiration - Diaphragm and external intercostal muscles
Thoracic dimensions expand
Volume increases pressure decreases air moves into the lungs (boyles law)

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13
Q

Muscles During Inhalation?

A

Prime Movers

  • Diaphragm 75%
  • External intercostals 25%

Sternocleidomastoid, serratus anterior, pectorals minor, scaline muscles that assist in lifting of the ribs

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14
Q

What Is Lung Compliance?

A

The ease with which the lungs can be expanded

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15
Q

What are the clinical measures of lung functioning?

A

Volume
Flow rate
Pressure

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16
Q

Definition of FEV1 & PEF?

A

FEV1 - The volume of air expelled in the first second of maximal forced expiration from a position of full inspiration

PEF - Peak expiratory flow, is the maximal expiratory flow rate achieved and this occurs very early in the forced expiratory manoeuvre

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17
Q

Restrictive Lung Disease?

A

Characterised by reduced lung volume, either because of an alteration in lung parenchyma or because of a disease of the pleura.

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18
Q

What are intrinsic lung diseases?

A

diseases of the lung parenchymal disease cause inflammation or scarring of the lung tissue or result in filling of air spaces with exudate and debris

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19
Q

What are extrinsic lung disorders?

A

diseases that the chest wall, pleura and respiratory muscles are the components of the respiratory pump, and they need to function normally for effective ventilation

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20
Q

What Is COPD?

A

Chronic obstructive pulmonary disease

a group of illnesses characterised by airflow limitation that is not fully reversible.

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21
Q

Asthma?

A

A chronic inflammatory disease of the airways with bronchial hyperesponsivness

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22
Q

Thermal Theory?

A

During exercise;
Minute ventilation increases with exercise
large volumes of cool dry air causes heal loss and airway cooling
After exercise rapid airway reheating occurs causing vasoconstriction and airway edema
airway narrowing
EIB can occur after inspiration of hot air

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23
Q

Hypersomolarity Theory?

A

Assures main causes is a change in osmolarity in airway cells
normally nose moistens and warms air but limited to minute ventilation ~30 L.min-1
At higher levels of ventilation bronchi contribute to warming and humidifying inspired air
this leads to loss of water and hyperosmolar conditions in airway cells
increased osmolarity triggers degranulation of mast cells esoniphils with the release of inflammatory mediators histamine leukotrines and prostaglandins

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24
Q

Three main findings from the study?

A

First, heat stress dramatically reduced VO2max compared with the normal conditions by accelerating the declines in Q and MAP (Mean arterial blood pressure).

The declining skeletal muscle VO2 before fatigue with or without heat stress was solely attributed to lowering in systemic and skeletal muscle O2 delivery

The reduced leg VO2 with heat stress was accompanied by an enhanced muscle lactate accumulation and ATP and PCr hydrolysis, yet muscle stores were not depleted on fatigue

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25
Q

What do the results suggested?

A

That impaired skeletal muscle aerobic energy provision and work capacity during maximal aerobic exercise in healthy trained humans are directly related to the inability of the heart maintain Q and O2 delivery to skeletal muscle

26
Q

What accounts for 90% of energy spent during exercise?

A

The working skeletal muscle cells, which account for more than 90% of energy spend during severe exercise, largely determine VO2max.

27
Q

Method

A
  • Rested in supine position, catheters were placed into the femoral artery, bilateral femoral veins, and antecubital forearm vein.
  • Completed 3 time cycle ergometer exercise tests in the upright position, starting with either high (Test 1) or normal (tests 2 or 3). Skin and core temperature. In tests 1 and 3 subjects cycled until volatile fatigue, where in test 2 they cycled for the same duration as in the heat stress test.
  • In every test power output was held at 356 +- 14 W.
  • Each test was separated by 1 hour of rest and was proceeded by 10-15 minutes of light intensity cycling (<50%VO2max) and 5 minutes of rest
  • The exercise intensity was selected so subjects would be exhaust within 5-10 minutes
  • To restore bodily fluid, subjects ingested ~2 litres of a carbohydrate-electrolyte solution during rest periods
  • In N trials subjects wore only shorts whilst cycling with 2 fans blowing at an ambient temperature of 14 to 16 degrees
  • During rest periods muscle biopsies from vastus lateralis was taken
  • On completion of each exercise bout, a post exercise muscle biopsy was taken within 20-40 seconds
28
Q

What was measured during each exercise bout?

A

Heart rate, pulmonary VO2, blood pressure, cardiac output and leg blood flow, and venous blood temperature

29
Q

What were muscle biopsies analysed for?

A

Lactate, Creatine Phosphate and glycogen

30
Q

Statistical test used?

A

Repeated-measures ANOVA

31
Q

H and N responses on Q, LBF and MAP?

A

Declined significantly before exhaustion compared with the corresponding peak exercise values

32
Q

Q during last 2 minutes of exercise?

A

Was associated with a greater reduction in stroke volume

33
Q

LBF and MAP in trials

A

In all trials, the magnitude of changes in LBF paralleled those of MAP and thus leg vascular conductance was unchanged throughout exercise.

34
Q

What declined when haemoglobin concentration increased?

A

The progressive declines in arterial O2 saturation and PO2 were accompanied by a proportional increase in haemoglobin concentration

35
Q

What happened before exhaustion in both H and N trials?

A

Systemic O2 delivery and O2 delivery to the legs decreased by 0.3 to 0.5 L/min

36
Q

How much did leg O2 extraction increase by in exhaustion trials?

A

91%

37
Q

How was muscle glycogen, lactate, ATP and creatine phosphate (PCr) affected before and after trials?

A

Were similar before, however after muscle lactate, PCr and ATP were greater and the rate of leg lactate release was higher

38
Q

What was found during the early stages of exercise?

A

Observed that when heat stress was added and the skin vasodilated, q was higher and blood flow to the legs was lower, but systemic and locomotive muscle VO2 were similar

39
Q

LBF effect of Vo2?

A

The lower LBF with heat stress was met by elevations in Cao2, arteriovenous O2 difference and O2 extraction, which permitted VO2 by the legs to be maintained

40
Q

What affected VO2max?

A

Findings was that impairment in VO2max was initiated by the more rapid decline in Q and MAP (Mean arterial blood pressure)

41
Q

How was leg vascular conductance affected between trials? And what does this suggest?

A

Was unchanged between trials, which suggests that lowering LBF and O2 transport was due to reduction in Q and perfusion pressure

42
Q

Relationship between Heat stress and cardiovascular system?

A

Heat stress pushes the cardiovascular system to its regulatory limit quicker.

43
Q

What limits the diffusion of O2?

A

Limitations to the diffusion of O2 from the muscle capillary to the mitochondrial cytochrome have been postulated to restrict VO2max

44
Q

What happened to leg arteriovenous and O2 extraction?

A

leg arteriovenous O2 difference and O2 extraction increased progressively until the end of exercise.

45
Q

What was responsible for the decline in leg VO2?

A

the greater decline in convective O2 transport to the leg muscles was clearly the cause of the reductions in leg Vo2

46
Q

The effect of muscle O2 conductance on Vo2?

A

The contribution of muscle O2 conductance in limiting locomotive muscle VO2 during whole body exercise is very small

47
Q

As a restrictive lung disease how might obesity increase the cost of breathing at rest?

A

Obesity will increase subcutaneous fat around the rib cage [1] and increase the amount of visceral fat in the abdomen [1]. This will increase the resistance to inspiration and require more effort by the respiratory muscles external intercostal muscles and diaphragm [2]. The energy cost of breathing will be increased. [1].

48
Q

What happened to leg O2 extraction and femoral venous blood when exposed to heat stress and normal conditions?

A

Reached equal values of 91% when exposed to either heat stress or normal conditions

49
Q

What did the decline in Q, LBF and MAP show related to maximal cardiovascular functioning?

A

Q, LBF and MAP declined significantly before maximal heart rate shows that maximal cardiovascular function was attained below maximal hear rate

50
Q

What was the cause of the impaired stroke volume in heat stress trial?

A

Reduction in central blood volume and cardiac filling secondary to the increased skin blood flow and volume was the cause of the impaired stroke volume with heat stress

51
Q

What also fell with stoke volume in the last 2 minutes?

A

The fall in stoke volume during the last 2 minutes of exercise in both fatiguing trials coincided with a declining MAP, body temperature and maximal heart rate

52
Q

What could also have caused a reduce in MAP?

A

That different factors interact to alter preload and or left ventricular systolic and diastolic function and impair stroke volume

53
Q

Why does stroke volume decline in heavy exercise?

A

As the simple restriction in left ventricular filling time and left ventricular end diastolic volume that accompanies tachycardia

54
Q

What is tachycardia?

A

A abnormal heart rate

55
Q

What was the main bodily tissue responsible for reductions in peripheral blood flow and Vo2?

A

Locomotive skeletal muscle

56
Q

How was femoral venous blood temperature affected by each trial?

A

Similar in both trials - 39.5-39.7 degrees

57
Q

What contributes to fatigue in heavy exercise?

A

Accumulation of P, ADP and H+ in the muscle cells which inhibits muscle contractile proccesses

58
Q

What reduced Vo2Max in heat stress?

A

By an accelerated decline in Q, MAP which lead to decrements in skeletal muscle flow

59
Q

With reference to respiratory muscles, thoracic dimensions, intrapulmonary volume and pressure explain the mechanical process of inspiration. [ 7 marks]

A

At rest, primer movers 25% external intercostal muscles and 75% diaphragm.

Inspiration (breathing in) occurs when the thoracic dimensions [1] increase by the action of the diaphragm moving inferiorly (moving down) [2] and the external intercostal muscles lifting the ribs increasing the anterior-posterior and lateral dimensions [2]. These actions increase lung volume and intrapulmonary pressure decreases [1]. This creates a pressure gradient with intrapulmonary pressure less than atmospheric pressure and air moves into the lungs [1].

60
Q

With reference to figure 1 explain why a restrictive disease increases the energy cost of breathing?

A

A restrictive lung disease is represented by fibrosis [1]. For a given distending pressure there is lower change in lung volume compared to normal [1] or the rate of change of volume is less as distending pressure increases [1]. More force (effort) is required by the inspiratory muscles to breath [1]

61
Q

What is Lung compliance?

A

Lung compliance, or pulmonary compliance, is a measure of the lung’s ability to stretch and expand (distensibility of elastic tissue).

62
Q

With reference to the pressure volume curve in figure 2 explain the shape of the curves for the disease conditions, emphysema and fibrosis, compared to the normal curve

A

The effort of breathing is indicated by the distending pressure. The volume shows the amount of expansion (distension or stretch) of the lungs for given pressure. 1 mark
In emphysema the lungs are stretched (expanded) easily and for a given pressure increase in volume more than normal. 2mark
In fibrosis the lungs do not stretch (expand) easily and for a given pressure increase less in volume than normal

Physiology Test 2 (1 decks)

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