# به نام خدا. دكتر محمد امامي فوق تخصص ريه عضوهيات علمي دانشگاه علوم پزشكي اصفهان.

## Presentation on theme: "به نام خدا. دكتر محمد امامي فوق تخصص ريه عضوهيات علمي دانشگاه علوم پزشكي اصفهان."— Presentation transcript:

به نام خدا

دكتر محمد امامي فوق تخصص ريه عضوهيات علمي دانشگاه علوم پزشكي اصفهان

Cardiopulmonary Exercise Testing

JOSEPH PRIESTLY (1733-1804) Discovers Oxygen

Exercise requires the coordinated function of several integrated systems: 1-Heart 2-Lung 3-Blood 4-Muscle

Oxygen content The arterial oxygen content (CaO2) is the amount of oxygen bound to hemoglobin plus the amount of oxygen dissolved in arterial blood CaO2 (mL O2/dL) = (1.34 x hemoglobin concentration x SaO2) + (0.0031 x PaO2) Normal CaO2 is approximately 20 mL O2/dL.

the mixed venous blood oxygen content (CvO2) is the amount of oxygen bound to hemoglobin plus the amount of oxygen dissolved in mixed venous blood CvO2 (mL O2/dL) = (1.34 x hemoglobin concentration x SvO2) + (0.0031 x PvO2) Normal CvO2 is approximately 15 mL O2/dL

Oxygen delivery Oxygen delivery (DO2) is the rate at which oxygen is transported from the lungs to the microcirculation DO2 (mL/min) = Q x CaO2 Normal DO2 is approximately 1000 mL/min AV oxygen difference (mL O2/dL) = CaO2 - CvO2

Oxygen consumption (VO2) Oxygen consumption (VO2) is the rate at which oxygen is removed from the blood for use by the tissues Normal VO2 in a conscious, resting person is approximately 250 mL O2/min VO2 (mL O2/min) = Q x (CaO2 - CvO2)

Oxygen extraction Oxygen extraction is the slope of the relationship between oxygen delivery (DO2) and oxygen consumption (VO2) O2 Extraction Ratio = (CaO2 - CvO2)/CaO2 Normal O2 extraction ratios range from 0.25 to 0.30

NORMAL PHYSIOLOGY Oxygen consumption (VO2) is proportional to oxygen delivery (DO2) and oxygen extraction DO2 and oxygen extraction are inversely proportional to one another At rest, VO2 remains constant over a wide range of oxygen delivery (DO2) because changes in DO2 are balanced by reciprocal changes in oxygen extraction

VO2 decreases if DO2 declines to such a degree that it cannot be balanced by increasing oxygen extraction The threshold value of DO2 below which VO2 will fall is called the "critical DO2"

PATHOPHYSIOLOGY PATHOPHYSIOLOGY Decreased oxygen delivery or increased metabolic demand are common sequelae of medical illness

Decreased oxygen delivery Oxygen delivery (DO2) will decrease if cardiac output falls or arterial oxygen content (CaO2) declines Cardiac output can decrease due to cardiac disease or hypovolemia CaO2 can decrease due to anemia or poor oxygenation. The latter can be caused by lung disease (eg, ventilation-perfusion mismatch, diffusion limitation), a right-to-left shunt, diminished inspired oxygen, or hypoventilation

Increased metabolic demand Metabolic demand is elevated in critically ill patients (eg, acute respiratory distress syndrome, sepsis, or septic shock)

Cardiac Pump CO=HRxSV The predicted maximum HR is 220 minus age in years (alternate: 210 - [0.65 x age in years])

O2 Pulse O2 pulse is Vo2/HR, obtained by dividing these two simultaneous measurements taken during exercise

AT Most of the metabolic work performed by the muscles during exercise is done via aerobic mechanisms There is workload above which a given person his or her or her physiologic capability to do most of the work aerobically, and incremental work rates result in progressive lactic acidosis in the blood due to anaerobic metabolism in muscle

The Ventilatory Pump VE=TVxRR Early in exercise, VE increases mostly due to increases in TV As TV reaches approximately 50 to 60% of vital capacity (VC), it begins to plateau, and further increases in VE are mostly due to increases in RR

Gas Exchange in the Lung Total VE=VA+VD VD/VT Ratio=0.3 at rest VD/VT Ratio=0.18 during maximum exercise VD/VT=Paco2-pEco2/Paco2

O2 Transfer During exercise, P(A-a)O2 increases due V/Q mismatching, O2 diffusion limitation, and low Svo2

Exercise physiology Skeletal muscle metabolism can rise quickly to fifty times its resting rate during heavy exercise. VO2 increases linearly versus work rate with a slope of approximately 10 mL/min per watt in normal subjects A true maximal VO2, identified by a plateau of VO2 versus work, occurs only in a small subset of normal subjects and patients normal VO2max is greater than 20 mL/kg per min, and can be predicted from age, gender, height, and lean body weight.

The VO2max increases as a function of training and decreases with age A young, world-class endurance athlete may have a VO2max greater than 80 mL/kg per minute

Minute ventilation (VE) normally rises during incremental exercise as a result of a linear increase in breathing frequency (up to about 50 breaths/minute in normal adults) and a hyperbolic increase in tidal volume (Vt)

During exercise, the partial pressure of oxygen in arterial blood (PaO2) remains near resting values despite marked reductions in mixed venous oxygen tension (PvO2) and an abbreviated red cell transit time through the pulmonary capillaries

External and Internal Measurements of Work During an incremental exercise test, there is a steady, linear increase in external work rate performed by the patient. This is expressed in watts. Internal metabolic work performed by the muscles is generally represented by the linear increase in Vo2 with increasing work

The shift into increasing anaerobic metabolism is a reflection of limitations in O2 delivery or in muscle oxidative capacity, or both

Patient Safety a relatively safe procedure The risk of complications is related to the underlying disease Rate of death is between 2 and 5 per 100,000 tests

Primary Measurements ECG: The ECG is used for heart rate (HR), Stsegment depression, and arrhythmia detection Collection of Expired Gases Pulse Oximetry Arterial Catheterization BP

Indications for CPET Unexplained Exertional Intolerance: Dyspnea or Fatigue Objective Assessment of Capacity/Impairment Establish Organ System-Limiting ExerciseWhen Multiple Diagnoses Are Present Preoperative Assessment Before Lung Resection Diagnose Exercise-Induced Asthma

Identify Gas Exchange Abnormalities Titrate O2 Flow During Exercise Pulmonary Rehabilitation Prescription and Assessment of Response Transplant Referral and Prognosis Assess Response to Therapy

Absolute Contraindications to CPETs 1-acute myocardial infarction (prior 3 to 5 days) 2-unstable angina 3-uncontrolled, symptomatic arrhythmias 4-syncope 5-active endocarditis; acute myocarditis or pericarditis 6-symptomatic severe aortic stenosis 7-uncontrolled heart failure

8-thrombosis of lower extremities 9-suspected dissecting aneurysm 10-uncontrolled asthma 11-pulmonary edema 12-room air saturation,85% (can exercise with supplemental O2); 13-respiratory failure 14-mental impairment leading to inability to cooperate

Relative Contraindications to CPETs left main coronary stenosis or equivalent moderate stenotic valvular heart disease severe untreated arterial hypertension at rest (.200 mm Hg systolic,.120 mm Hg diastolic) tachyarrhythmias or bradyarrhythmias high-degree atrioventricular block Hypertrophic cardiomyopathy significant pulmonary hypertension (although this can be done safely) advanced or complicated pregnancy electrolyte abnormalities orthopedic impairment that compromises exercise performance

Indications for Exercise Termination chest pain suggestive of ischemia ischemic ECG changes complex ectopy Second or third-degree heart block fall in systolic BP> 20 mm Hg hypertension (>250 mm Hg systolic, >120 mm Hg diastolic) desaturation (Spo2<80% when accompanied by symptoms and signs of severe hypoxemia) sudden pallor loss of coordination mental confusion; dizziness or faintness signs of respiratory failure

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