VO2max and 6MWT

Question 1

Equation to Estimate VO2max

Answer 1

VO2max = 15 x (HRmax/HRrest)

Question 2

Factors that can affect O2 extraction and utilization (4)

Answer 2

Hemoglobin carrying O2
Nr. of capillaries
Nr. of mitochondria
Muscle fibers:
Type 1: use mitochondria to convert O2 to ATP, higher VO2max
Type 2: don’t use O2, lower VoO2max.

Question 3

Affects Cardiac, Pulmonary and Muscle Structure and Function on Different Components of Cardiorespiratory Fitness

Answer 3

Vasodilation, arterial resistance (nitric oxide), blood flow distribution and capillarization have affect on cardiac, pulmonary and muscle function.
Cardiac: ↑EF, ↑compliance, ↓afterload, ↑plasma, ↑preload, ↑blood volume affects Q.
Pulmonary: Resp. fatigue, diffusion capacity, V/Q matching (↓ dead space) affects CaO2.
Muscle: Mitochondrial content, O2 utilization, Type 1 fibers, time for lactate production, time for O2 extraction affects CvO2.

Question 4

CPET - Values Measured

Answer 4

Spirometry: O2 uptake (VO2), CO2 output (VCO2), ventilation (VE).
HR, BP, work rate, ECG findings and symptoms (dyspnea, muscle fatigue, chest pain: BORG).

Question 5

VO2max Convertion

Answer 5

VO2max = ml/kg/min
VO2 (L/min): 3
Body weight: 75kg
3 L/min x 1000 ml/L = 3000 ml/min
3000 ml / 75 kg = 40 ml/kg/min

Question 6

CPET - Intensity

Answer 6

Cycle-ergometer: ↑ 20W every minute with 50-60 RPM.
Treadmill: increasing incline or speed.
Maximal tests need physicians present, more accurate.
Submaximal tests don’t, but are safer and faster (85% of HRmax or 70% of HRR%)

Question 7

Maximal CPET - When to Stop

Answer 7

1. VO2 plateau despite increase in workload
2. HR within 10 beats of age predicted max.
3. > 8 millimoles per litre blood lactate concentration
4. Respiratory exchange ratio (RER) (VCO2/VO2) of 1,15 or above.
5. Borg scale 17 or mBorg 9.

Question 8

Graded Test vs Ramp Test

Answer 8

Graded: multistage exercise protocol. Increase of workload every 1-3 minutes.
Ramp: progressive incremental. Small increases throughout the minute to reach the desired increase within that minute. Uniform increase in hemodynamic and physiologic responses (more accurate).

Question 9

Calculating how much load should be increased every minute

Answer 9

Ramp = VO2peak - VO2unloaded/100
unloaded = 150 + (6 x weight) mL/min
peak = (height,cm - age) x 20 mL/min
Ramp = w/min

Question 10

Intensity Protocols (3)

Answer 10

Bruce: large increments every 3 minutes. Better for younger, physically active individuals.
Naughton and Balke: smaller increments better for older or deconditioned individuals and chronic pulmonary disease patient.

Question 11

CPET - Cardiovascular Response

Answer 11

Sympathetic discharge maximal, vasoconstriction except in exercising muscles, cerebral and coronary circulation.
Q increases, peripheral vascular resistance decreases due to vasodilation in exercising muscles.
DBP remains same or decreases slightly.

Question 12

CPET - Ventilatory Response

Answer 12

VE: minute ventilation increases linear.
VT: tidal volume increases first then plateau, then RR takes over and increases.

Question 13

CPET - Metabolic Response

Answer 13

Ventilatory threshold, change of metabolic predominance from aerobic to anaerobic. Lactate starts to accumulate in blood, ↑ acid, ↓pH. To counteract it we ↑ RR to get rid of CO2 ↓.
Seen on graph when VCO2 is in higher concentration than VO2.

Question 14

Cycle Ergometer Test

Answer 14

Assessment tool to identify exercise tolerance, identify max work rate.
Less specific than CPET, no spirometry, gas exchange analysis.
Measure: HR, RR, SBP, SpO2 (peripheric), perceived dyspnea and lower limb fatigue.
Maintenance: 50W (50-60RPM) until exhaustion.
Incremental: 20W every 2 minutes until exhaustion.

Question 15

6MWT - Contraindication

Answer 15

Absolute: unstable angina, recent myocardial infarction.
Relative: HR>120bpm at rest, PAS>180mmHg, PAD>100mmHg.

Question 16

6MWT - Instructions Before

Answer 16

Long time so you will be exerting yourself.
Permitted to slow down, stop and rest if necessary, resume walking as soon as you are able!
Walk as far as possible! for 6 minutes. Not run or jog.

Question 17

6MWT - Instructions During

Answer 17

Monitor HR, SpO2 and Borg every minute.
You are doing well. you have 5 minutes to go.
Keep up the good work. you have 4 min to go.
——. you are halfway.
——. you have only 2 minutes left.
——. you only have 1 minute to go.
Please stop where you are.
Sit patient down and monitor again.

Question 18

6MWT - Reference Equations (if patient failed the test or not)

Answer 18

Male: (7.57 x height,cm) - (5.02 x age) - (1.76 x weight) - 309m. Subtract 153m for lower limit.
Female: (2.11 x height,cm) - (2,29 x weight) - (5.78 x age) + 667m. Subtract 139m for lower limit.

Question 19

6MWT - VO2 Prediction (Equations)

Answer 19

Moderate to severe CPD: 4.948 + 0.023 x mean 6MWD (meters) = ml/kg/min.
Healthy: 70.161 + (0.023 x 6MWD) - (0.276 x weight) - (6.79 x sex (m:0, f:1)) - (0.193 x HRrest) - (0.191 x age) = ml/kg/min.

Question 20

Cardiovascular Limitation

Answer 20

HRpeak/HRmax
HRmax use correct formula!
HRpeak in test.
>90% cardiovascular limitation.

Question 21

Ventilatory Limitation

Answer 21

VEmax / MVV
MVV: maximal voluntary ventilation: FEV1 (L) x 40.
> 70% ventilatory limitation.