Cardiopulmonary Exercise Testing Techniques to Evaluate Exercise Intolerance

Abstract

The use of exercise testing is an important tool for the pediatric pulmonologist. Physical stress often reveals cardiorespiratory abnormalities that are not apparent on conventional static tests. There is little doubt the information acquired from exercise tests have diagnostic and prognostic value, but exercise tests may also be critical to determine success or failure of treatment strategies. The purpose of this chapter is to provide the pediatric specialist with an overview of exercise evaluation that may assist in the diagnosis of and management of disease in pediatric and adolescent patients with physical activity intolerance, especially those with cardiorespiratory diseases. The specific aims of this chapter are to: (1) describe various exercise tests and the biomechanical and physiological principles of those tests necessary to assess patients; (2) discuss methods to assess the physical fitness profile of patients with cardiorespiratory diseases and physical limitations; (3) provide specific strategies for an exercise prescription based on the fitness and clinical profile of the patient and; (4) assist the provider in developing a center for exercise evaluation. Although each aim provides unique information, the overall goal of this chapter is to stimulate the pediatric pulmonologist to develop an understanding of indications for cardiopulmonary exercise testing (CPET) and implement strategies to systematically assess each patient’s fitness profile; to track patient’s disease or training progression or alternatively to monitor responses of medical interventions; and to prescribe a well-rounded exercise prescription to maximize functional ability and wellness of individual patients. This chapter is not intended to be an in depth review for exercise physiologists, but is designed to assist the practicing clinician in the logistics of developing a program and a comfort in interpreting studies.

Appendices

Case Studies

Case 1: CPRT Performed Pre-pectus Repair Nuss Bar

Patient 17 year old with Erlos-Danlos Syndrome.

Test variable	Predicted max	Rest	AT	AT2	VO2 max (peak)
RER		0.89	0.92		0.98
Pulse O2	18	2	5	7	9
Work (Watts)	306		34	60	62
HHR%		100	85	78	75
BR%		95	92	87	81
HRR (bpm)		109	93	85	82
VO2 slope	–	–	–	–	–
VO 2 pred (%)		6	14	22	32
HR pred (%)		47	55	59	60
Exer time (min)			2	4	6
BP systolic		122			121
BP diastolic		81			75
PETO2		108	106	105	108
PETCO2		34	37	39	39
VO2 ml/kg/min	>35	3.6	8.2	12.9	18.9
HR bpm	205	96	112	120	123
VECO2		32	28	27	28
Vd/VT (estimated)		0.26	0.2	0.18	0.17
RR (br/min)

Variable checklist used to identify the pathophysiologic mechanism resulting in activity/exercise intolerance (N for normal range)

Variable	Y	N	H	L	Other
VO2 max predicted attained or		x
Maximum VO2 reached?		x
Work load predicted from equations attained?		x
Oxygen use high for work level		x
Plateau of VO2 or heart rate with increasing work rate?		x
RER maximal test (1.15)?		x
Maximum HR predicted achieved?		x
Max HR to low (sick heart-chronotropy)?		x
Max HR too High (sick heart-inotropy)?		x
ST segment displaced?		x
Cardiac arrhythmias?		x
Echocardiogram result		x
Was the breathing reserve low (<20)?		x
Was the breathing reserve normal or high?	x
Dead space ventilation increase or decrease (VD/VT)?		x
Oxygenation by (SaO2) normal		x
Obese?		x
Effort reason for stopping (if patient stopped)					Dyspnea fatigue
Blood pressure increase appropriately?		x
Is the patient a performance athlete?		x
HRR normal?
HR1 (1 min postexercise)?					x
HR2 (2 min postexercise)?					x
Pulse O2 normal (rise and plateau)?		x
VAT percent of VO2 (V-slope)?					x
VE too high or VE too low?		x

Variable	Result
PETCO2 (no change) or VECO2 (increase)	Normal
Breathing reserve low	No (high)
VAT (ventilatory threshold) present	Yes low
Pulse O2	low
Breathing reserve normal	High (normal)
VAT present	low

Cause-and-Effect Diagram Result (Case 1: Check All That Apply)

Conclusion: (check or circle)

• Cardiac Limitation.

• Respiratory Limitation.

• Peripheral Vascular Limitation (PVD).

• Pulmonary Hypertension (Circulation).

• Metabolic Limitation.

• Muscle Limitation.

• Deconditioned.

• Poor Effort.

Summary:

CPRT performed pre-pectus repair Nuss Bar.

Patient with Erlos-Danlos Syndrome.

The PETCO₂ did not decrease, but VAT was achieved. The BR was normal. PaETO₂ and VD/VT were normal as well. The pulse O₂ was significantly low as was the VO₂ max at levels seen in cardiomyopathies. The Echo results note a normal structured heart with good ejection fraction. Cardiac limitation likely from decrease left ventricular filling at higher (nonresting) level due to abnormal chest wall dynamics and decrease LV filling and stroke volumes at higher work levels. The patient is not physically fit.

Case 2: 14-year-old female complaints of dyspnea and inability to run cross country recent onset last 2 months.

Variable	Result
PETCO2 decrease or VECO2 increase	Normal yes
Breathing reserve low	Normal
VAT (ventilatory threshold) present	Yes (early)
Pulse O2	Low
Breathing reserve normal	Normal
VAT present	Yes

Suggest Cardiac Limitation

Other data:

• VO₂ max low

• SaO₂ low at max exercise

• RR less than 50

• HRR normal

• Basal HR Slightly High for Age and Fitness Level (Runner)

• Normal Chronotropic Response (80% of predicted maximal HR)

• Hemoglobin 5.9

Cause-and-Effect Diagram Result (Case 2: Check All That Apply)

Conclusion: (check or circle)
° Cardiac limitation
° Respiratory limitation
° Peripheral vascular limitation (PVD)
° Pulmonary hypertension (circulation)
° Metabolic limitation
° Muscle limitation
° Deconditioned
° Poor Effort
° Anemia

Summary:

Good Effort (RER . 1.15)

Additional History:

• Complaints of dyspnea and inability to run cross country recent onset last 2 months.

• Complete study with dyspnea at end, stopped complaining of fatigue, leg cramps, and dizziness. BP increase appropriately and the HRR reserve was normal though basal HR was increased. Leg Cramps likely from early VAT and low peripheral oxygen extraction at muscle level.

• Pre-study same day pulmonary function tests pending calculation of DLCO

• CBC reviewed (low hemoglobin)

• SaO₂ decrease likely secondary to increase oxygen extraction.

• Exercise Intolerance secondary to anemia.

• Additional History—teen with dysfunctional uterine bleeding menorrhagia for 4 months.

• Diet vegetarian.

• Sent to adolescent to reproductive health and iron indices ordered. sports nutrition discussed.

• Primary care informed for follow-up.

Case 3: 22 year old prior 28 week premie born 1,088 g and did not receive surfactant. Bronchopulmonary dysplasia (BPD), intraventricular hemorrhage, osteopenia, and retinopathy of prematurity. College Student Masters Program Psychology.

Test variable	Predicted max	Rest	AT	AT2	VO2 max (peak)
RER			0.85	1.04	1.28
Pulse O2	8	2	3	6	9
Work (Watts)
HHR%		100	101	30	28
BR%		92	91	50	37
HRR	105	106	32	30	39
VO2 slope
VO2 pred (%)		13	15	62	91
HR pred (%)
Exer time		2	7	15	16
BP systolic
BP diastolic
PETO2		106	107	124	121
PETCO2		34	33	24	25
VO2 ml/kg/min	38	5.1	5.7	23	34
HR bpm	198	92	116	168	172
VE/VCO2	42	44	45	44	46
Vd/VT (estimated)		0.22	0.22	0.13	0.14
RR (br/min)		20	24	40	68

Variable	Result
PETCO2 decrease or VECO2 increase	+
Breathing reserve low	Normal
VAT (ventilatory threshold) present	+
Pulse O2	Normal
Breathing reserve normal	Normal
VAT present	+

Other data

• VO₂ ml/kg min⁻¹ (normal).

• RR > 50 at VO₂ max.

• FEV1 105 % predicted.

• FVC 98 % predicted.

• EKG normal during study.

Cause-and-Effect Diagram Result (Case 3: Check All That Apply)

Conclusion: (check or circle)

• Cardiac limitation.

• Respiratory limitation.

• Peripheral vascular limitation (PVD).

• Pulmonary hypertension (circulation).

• Metabolic limitation.

• Muscle limitation.

• Deconditioned.

• Poor effort.

• None

Summary

Complains of chest pain with exercise

22 year old prior 28 week premie born 1,088 g and did not receive surfactant. Bronchopulmonary dysplasia (BPD), intraventricular hemorrhage, osteopenia, and retinopathy of prematurity. Gymnastics and Cheerleading at local university runs for exercise complaining of chest pain. Problems with cervical and thoracic scoliosis with secondary neuropathy manifest as pain, restless leg syndrome, and periodic limb movement disorder of sleep. Anxiety disorder and ADHD. Good student on medications

Medications:

• 1. Pregbalin.

• 2. Vyvanse.

• 3. Adderall 7.5 mg prn once daily.

• 4. Dulera two puffs twice a day.

Results:

There is no evidence of cardiopulmonary limitation. The VO₂ max is normal and the cause-and-effect diagram is not valid in this case. The spirometry data shows no pre–post difference. However, the use of the cause-and effect-diagram does point out an interesting finding, at maximal work the RR was greater than 50 breaths-per-minute. If the VO₂ was low and PETCO₂ did not decrease and dead space ventilation not decrease, then respiratory limitation would be likely if the breathing reserve was low. The breathing reserve was normal and with the clinical history of BPD and prematurity pulmonary vascular disease should be considered. The dynamics of chest wall movement should also be considered due to the longstanding cervico-thoracic scoliosis. Exercise associated anxiety should also be entertained as the patient has a known issue.

Recommendations:

• 1. Close follow-up and yearly CPET- Echo/EKG monitoring for evidence of pulmonary hypertension.

• 2. Cognitive behavioral therapy for anxiety. Monitor scoliosis and associated neuropathy with sleep problems.