Workup of Dyspnea - Pulmonary

Joel A Wirth, MD, FCCP

Director, Division of Pulmonary and Critical Care Medicine, Maine

Medical Center

Staff Physician, Chest Medicine Associates

Case 248 year old woman with unexplained exertional dyspnea.

Age 9: CHD (ASD with endocardial cushion defect) with a late repair at Boston Children’s Hospital Age 10: Mitral Valve replacement ( porcine) Age 13: Mechanical valve. Age 40: MV re-do with a TV ring and pacemaker placement.

Worsening DOE for the past 8 years. She is a lifelong nonsmoker, has history of mild asthma. Episodes of daily chest tightness are very severe, aggravated climbing stairs, supine position and humidity. Associated symptoms include dry cough, fatigue, lower extremity edema and occasional wheezing.

48 year old woman with unexplained exertional dyspnea.

Age 9: CHD (ASD with endocardial cushion defect) with a late repair at Boston Children’s Hospital Age 10: Mitral Valve replacement ( porcine) Age 13: Mechanical valve. Age 40: MV re-do with a TV ring and pacemaker placement.

Worsening DOE for the past 8 years. She is a lifelong nonsmoker, has history of mild asthma. Episodes of daily chest tightness are very severe, aggravated climbing stairs, supine position and humidity. Associated symptoms include dry cough, fatigue, lower extremity edema and occasional wheezing.

Case 2 (Continued)Past Medical/Surgical HistoryCongenital heart disease s/p ASD and MV repair, TV ring

Secondary pulmonary hypertensionBradycardia s/p pacemaker placement Right hemidiaphragm paralysis

(phrenic nerve injury) 2005Diastolic heart failure

Hepatitis CAsthma

MedicationsVITAMIN B COMPLEX, VALIUM, COUMADIN, CITALOPRAM, ATIVAN

Social History Education and Employment: Radiation therapist. Never smoker.

PHYSICAL EXAMINATION

Vital Signs P RR BP SpO2 Weight kg/lbBMI78 16 104/6897% on RA 59.320/130.8 21.43

Physical ExamConstitutional No apparent distress. Thin and well developed.Head / Face Normocephalic. ENT Normal. No mucosal lesions.Respiratory Normal to inspection and palpation. Lungs CTA.

Right hemidiaphragm diminished excursion to percussion.Cardiovascular RRR. Crisp MV Prosthetic HS. No MRG.Abdomen Soft, non-tender without organomegaly or masses.Back / Spine No kyphosis or scoliosis.Musculoskeletal No skeletal tenderness or joint deformity. Extremities No edema or cyanosis, no clubbing.Neurological Alert and oriented. Psychiatric No anxiety or depression.

Case 2 (Continued)

Our Patient: Resting Echocardiogram

Basic Workup of Exertional Dyspnea

Lung Disease Airways disease Interstitial Lung DiseaseNeuromuscular Disease Vocal Cord Dysfunction

PFTs

Chest Imaging (CXR, CT)

Methacholine Challenge

Testing

Heart DiseaseMyocardial Disease (Systolic, Diastolic)Valvular Heart DiseaseCoronary Artery Disease

EKG

Echocardiography

BNP

Pulmonary Vascular Disease (Pulmonary Hypertension, PE)

Echocardiography, CTPA,

V/Q

Metabolic Disease Anemia Thyroid Disease

CBC, TFTs

Deconditioning, Anxiety Exclusion

Our Differential Diagnosis for her Dyspnea:

1. Lung Disease • Airways disease (Asthma)• Interstitial Lung Disease• Vocal Cord Dysfunction• Thoracic Cage Abnormality (Paralyzed right

hemidiaphragm)

2. Heart Disease• Left ventricular diastolic dysfunction• Valvular Heart Disease• Pacemaker Malfunction• Coronary Artery Disease

3. Pulmonary Vascular Disease (Pulmonary Hypertension, PE)

4. Peripheral (Myopathy/Malnutrition/Neuromuscular dysfunction)

5. Anemia6. Thyroid Disease7. Deconditioning8. Perception/Anxiety

Evaluation of Unexplained Dyspnea

Balady G J et al. Circulation. 2010;122:191-225

Does Anemia cause dyspnea and exercise limitation?

Cote et al., Eur Resp J. 2007 29:923-929

Thyroid Disease: Mechanisms for Exertional Dyspnea

Hyperthyroidism: Reduced Heart Rate Reserve

Slower Heart Rate and BP Recovery

Hypothyroidism: Impaired oxygen metabolism

Reduced maximal Heart RateReduced maximal Ventilation

Causes of dyspnea as assessed by Spirometry Echocardiography, &

EKG in 129 Danish SubjectsOnly 69% of patients were diagnosed by these 3 tests

* Heart Disease defined as AFib, LV systolicdysfunction or valve disease

† Lung Disease defined as FEV1% < 70%

‡ Obesity defined as BMI > 30 kg/m2

Pedersen et al., Int J Clin Pract, 2007, 61, 9, 1481–1491

Why perform exercise testing for exertional dyspnea?

• Cardiopulmonary measurements obtained at rest

may not reliably reflect functional capacity or

limitations

• Determine if dyspnea is physiologic or pathologic

• Determine cause of limitation: cardiac, pulmonary, or

peripheral

Types of Exercise Tests

• 6-min walk test Submaximal

• Shuttle walk test Incremental, maximal, symptom-limited

• Exercise bronchoprovocation

• Exertional oximetry

• Cardiac stress test

• Exercise echocardiography

• Cardiopulmonary Exercise Testing (CPET)

What can CPET do for YOU?1. Evaluation of dyspnea

• Distinguish Cardiac vs Pulmonary vs Peripheral limitation

• Detection of exercise-induced bronchospasm (EIB)

2. Pulmonary rehabilitation• Exercise intensity/prescription• Response to participation

3. Pre-op evaluation and risk stratification• Lung resection

4. Prognostication of life expectancy• Congestive Heart Failure/Cardiomyopathy• Pulmonary Arterial Hypertension• Cystic Fibrosis

5. Assess response to therapy• COPD, Asthma, PAH

6. Disability determination

7. Fitness evaluation

Internal and External Respiration

What is CPET?

• Symptom-limited exercise test

• Measure workload, ventilation,

SpO2, HR, Blood Pressure, EKG,

oxygen consumed and carbon

dioxide expired, respiratory

exchange ratio (RER)

• Allows calculation of peak

oxygen consumption,

anaerobic threshold

• Identifies general cause of

exercise limitation and if limit is

normal or abnormal

Contraindications to CPET• Acute MI• Unstable angina• Unstable arrhythmia• Acute endocarditis, myocarditis, pericarditis• Syncope• Severe, symptomatic AS• Uncontrolled CHF• Acute PE, DVT• Respiratory failure• Uncontrolled asthma• SpO2 < 88% on RA• Significant non-cardiopulmonary disorder that

may affect or be adversely affected by exercise• Psychiatric/cognitive impairment limiting

cooperation

Relative Contraindications to CPET

• Left main or 3-V CAD• Severe arterial HTN (>200/120)• Significant pulmonary HTN• Tachyarrhythmia, bradyarrhythmia• High degree AV block• Hypertrophic cardiomyopathy• Electrolyte abnormality• Moderate stenotic valvular heart disease• Advanced or complicated pregnancy• Orthopedic impairment

General Mechanisms of Exercise Limitation

• Pulmonary

– Ventilatory

– Respiratory muscle

dysfunction

– Impaired gas exchange

• Cardiovascular

– Reduced stroke volume

– Abnormal HR response

– Circulatory abnormality

– Blood abnormality

• Peripheral

– Inactivity/Atrophy/

Malnutrition

– Neuromuscular

dysfunction

– Reduced oxidative

capacity of skeletal muscle

• Perceptual

• Motivational

General Mechanisms of Exercise Limitation

• Pulmonary

– Ventilatory

– Respiratory muscle

dysfunction

– Impaired gas exchange

• Cardiovascular

– Reduced stroke volume

– Abnormal HR response

– Circulatory abnormality

– Blood abnormality

• Peripheral

– Inactivity/Atrophy/

Malnutrition

– Neuromuscular

dysfunction

– Reduced oxidative

capacity of skeletal muscle

• Perceptual

• Motivational

Figure 7. Flow-volume loops.

Balady G J et al. Circulation. 2010;122:191-225

Ventilatory Limits to Exercise: Expiratory Flow Rates and

MVV

Figure 6. V̇3 o2 kinetics.

Balady G J et al. Circulation. 2010;122:191-225

Oxygenation Limits to Exercise: Oxygen Deficit and

Debt

Use of the “V-Slope” Method to detect the Ventilatory

(Anaerobic) Threshold, VT (AT)

Balady G J et al. Circulation. 2010;122:191-225

CPET Pulmonary Parameters

1. O2 consumed = VO2

2. CO2 produced = VCO2

3. Respiratory Exchange Ratio (RER) = CO2 produced / O2 consumed=VCO2 / VO2

4. Maximum Minute Ventilation (Vemax) = measured exhaled volume (L/min)

5. Maximum Voluntary Ventilation = Peak Ventilation in L/min

• Normal = 35 to 41 times FEV1

6. Breathing Reserve = (Predicted MVV – Vemax /Predicted MVV) x 100%

• Normal > 30%

7. Ventilatory equivalent for CO2 = Ve / VCO2

• Efficiency of ventilation, normal is < 30 and improves during exercise• Liters of ventilation to eliminate 1 L of CO2

8. Ventilatory equivalent for O2 = Ve / VO2

• Liters of ventilation per L of oxygen uptake

General Mechanisms of Exercise Limitation

• Pulmonary

– Ventilatory

– Respiratory muscle

dysfunction

– Impaired gas exchange

• Cardiovascular

– Reduced stroke volume

– Abnormal HR response

– Circulatory abnormality

– Blood abnormality

• Peripheral

– Inactivity/Atrophy/

Malnutrition

– Neuromuscular

dysfunction

– Reduced oxidative

capacity of skeletal muscle

• Perceptual

• Motivational

Cardiac Limits to Exercise: Maximum HR by Age

Oxygen Consumption: Fick Equation

• Fick Equation:

Q = VO2 / C(a-v)O2

VO2 = Q x 1.34(SaO2 - SvO2)(Hgb)

VO2 = SV x HR x 1.34(SaO2 - SvO2)

(Hgb)Heart disease Heart disease

Muscle diseaseDeconditioning

Lung disease Anemia

CPET Cardiac Parameters

1. Maximum Heart Rate = HRmax

2. Heart Rate Reserve =

(Predicted HRmax – HRmax)/Predicted HRmax x 100%

Normal is < 15%

3. Heart Rate Response (HRR) =

Change in HR/Change in VO2

4. Oxygen Pulse = VO2 / HR ≈ SV Fick Equation: VO2 = SV x HR x C(a-v)O2

VO2 / HR = SV x C(a-v)O2

Oxygen Pulse: “. . .the amount of oxygen consumed by the body from the blood of one systolic discharge of the heart.” Henderson and Prince. Am J Physiol 35:106, 1914

Abnormal Exercise Responses during CPET

Balady G J et al. Circulation. 2010;122:191-225

CPET Patterns of Cardiac and Pulmonary Disease during

Exercise

Adapted from: Balady G J et al. Circulation. 2010;122:191-225

MEASUREMENTSYMBO

L

CARDIACPULMONAR

Y

FINDINGS

Maximum Oxygen

ConsumptionVO2max Reduced Reduced

Maximum Heart Rate HRmax

> 85%

predicted

< 85%

predicted

Breathing Reserve BR > 30% < 15%

Oxygen Saturation SaO2 > 90% < 90%

Oxygen PulseVO2max/

HR

< 12

ml/beat

> 12

ml/beat

Ventilatory Equivalent

for CO2VE/VCO2 < 30 > 30

Anaerobic

Threshold/VO2max

AT (or

VT)< 40% > 40%

Our Patient

Our Patient: Pulmonary FunctionParamet

er

Patient %Predict

ed

FVC 2.66L 69%

FEV1 2.24L 74%

FEV1% 84%

TLC 4.24L 79%

FRC 2.91L 96%

RV 1.57L 84%

DLCO 15.9 62%

Our Patient: CPET

Paramet

er

Patient Normal

VO2max

22.3

ml/min/kg

30.2 (74%)

RER 1.1 >1.0

HRmax 98 beats/min 168 (58%)

VO2max/

HR

13.9 ml/beat 10.5

(132%)

BR(87-38)/87 =

56%

> 30%

VE/VCO2 27 < 30

SaO2 96% > 92%

AT (or

VT)

69% > 40%

Our Patient: CPET

168

87

12

Our Differential Diagnosis for her Dyspnea:1. Lung Disease

• Airways disease (Asthma)• Interstitial Lung Disease• Vocal Cord Dysfunction• Thoracic Cage Abnormality (Paralyzed right

hemidiaphragm)

2. Heart Disease• Left ventricular diastolic dysfunction• Valvular Heart Disease• Pacemaker Malfunction• Coronary Artery Disease

3. Pulmonary Vascular Disease (Pulmonary Hypertension, PE)

4. Peripheral (Myopathy/Malnutrition/Neuromuscular dysfunction)

5. Anemia6. Thyroid Disease7. Deconditioning8. Perception/Anxiety