Impedance cardiography estimate of the Q˙‐V˙O2 relationship in  pulmonary hypertension

Aitken, C; Lin, A; Seale, H; Feenstra, J; Trotter, M; Sabapathy, S; Walsh, J; Morris, N

Author(s)

Aitken, C

Lin, A

Seale, H

Feenstra, J

Trotter, M

Sabapathy, S

Walsh, J

Morris, N

Griffith University Author(s)

Sabapathy, Surendran

Aitken, Craig R.

Morris, Norman

Year published

2020

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Abstract

Introduction/Aim. The assessment of cardiac function, specifically cardiac output(Q˙), is one of the most robust indicators of right ventricular function and prognosis in pulmonary arterial hypertension (PH). Impedance cardiography (IC), is non‐invasive, easily accessible and can be used at rest and exercise. Preliminary studies, have suggested IC estimates of Q˙ during exercise may be inaccurate(1). One indirect method of validation is to examine the relationship between Q˙ and oxygen uptake(V˙O2) during exercise, which is well established. The aim of this study was to investigate the Q˙‐V˙O2 relationship in a group of PH ...
View more >Introduction/Aim. The assessment of cardiac function, specifically cardiac output(Q˙), is one of the most robust indicators of right ventricular function and prognosis in pulmonary arterial hypertension (PH). Impedance cardiography (IC), is non‐invasive, easily accessible and can be used at rest and exercise. Preliminary studies, have suggested IC estimates of Q˙ during exercise may be inaccurate(1). One indirect method of validation is to examine the relationship between Q˙ and oxygen uptake(V˙O2) during exercise, which is well established. The aim of this study was to investigate the Q˙‐V˙O2 relationship in a group of PH participants through IC. Method. In this preliminary study, 5 medically stable individuals with PH(WHO Functional class II‐III) were recruited. All participants completed an incremental exercise test (CPET), to establish peak exercise capacity and on a separate day a submaximal CPET at 30 and 60% of their respective peak workload. During exercise Q˙ was measured using IC (PhysioFlow,) and V˙O2 measured using open circuit spirometry (Metamax) simultaneously. The Q˙‐V˙O2 was estimated per participant using resting and exercise data. Results. The mean peak workload for the group was 91 ± 20 W. During the submaximal exercise test, there was a significant increase in Q˙(Rest: 5.2 ± 1.1; 30%: 7.4 ± 2.0; 60%: 10.2 ± 3.8 L.min‐1), V˙O2(Rest: 0.33 ± 0.06; 30%: 0.68 ± 0.04; 60%:1.03 ± 0.14 L.min‐1), heart rate(Rest: 74 ± 17; 30%: 94 ± 16, 60%: 113 ± 17 beats.min‐1) and stroke volume(Rest: 76.9 ± 38.4, 30%: 83.4 ± 39.3, 60% 95.8 ± 51.2 mL‐1). The mean slope of the Q˙‐V˙O2 relationship was 5.9 ± 4.1 (range 1.8‐10.8) which compares favourably with the mean slope from previous studies of 5.5 ± 0.5(2). Conclusion. The results of this preliminary study suggest that when Q˙ is measured using IC, the Q˙‐V˙O2 relationship was similar to that reported by others. However, there was marked variance in the response and further studies are warranted in the PH population.
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