Respiratory gas kinetics in patients with congestive heart failure during recovery from peak exercise

Patti, Alessandro; Blumberg, Yair; Hedman, Kristofer; Neunhäuserer, Daniel; Haddad, Francois; Wheeler, Matthew; Ashley, Euan; Moneghetti, Kegan J.; Myers, Jonathan; Christle, Jeffrey W.

doi:10.1016/j.clinsp.2023.100225

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Sumário

Original articles • Clinics 78 • 2023 • https://doi.org/10.1016/j.clinsp.2023.100225 copy

Respiratory gas kinetics in patients with congestive heart failure during recovery from peak exercise

Authorship SCIMAGO INSTITUTIONS RANKINGS

Highlights

Analysis of recovery from cardiopulmonary exercise testing reveals pathophysiology.
Recovery of respiratory gases from peak exercise is hindered in heart failure.
Recovery from peak exercise in heart failure is negatively correlated with peak VO₂ but not baseline LVEF.

Abstract

Background

Cardiopulmonary Exercise Testing (CPX) is essential for the assessment of exercise capacity for patients with Chronic Heart Failure (CHF). Respiratory gas and hemodynamic parameters such as Ventilatory Efficiency (VE/VCO₂ slope), peak oxygen uptake (peak VO₂), and heart rate recovery are established diagnostic and prognostic markers for clinical populations. Previous studies have suggested the clinical value of metrics related to respiratory gas collected during recovery from peak exercise, particularly recovery time to 50% (T1/2) of peak VO₂. The current study explores these metrics in detail during recovery from peak exercise in CHF.

Methods

Patients with CHF who were referred for CPX and healthy individuals without formal diagnoses were assessed for inclusion. All subjects performed CPX on cycle ergometers to volitional exhaustion and were monitored for at least five minutes of recovery. CPX data were analyzed for overshoot of respiratory exchange ratio (RER=VCO₂/VO₂), ventilatory equivalent for oxygen (VE/VO₂), end-tidal partial pressure of oxygen (PETO₂), and T1/2 of peak VO₂ and VCO₂.

Results

Thirty-two patients with CHF and 30 controls were included. Peak VO₂ differed significantly between patients and controls (13.5 ± 3.8 vs. 32.5 ± 9.8 mL/Kg*min⁻¹, p < 0.001). Mean Left Ventricular Ejection Fraction (LVEF) was 35.9 ± 9.8% for patients with CHF compared to 61.1 ± 8.2% in the control group. The T1/2 of VO₂, VCO₂ and VE was significantly higher in patients (111.3 ± 51.0, 132.0 ± 38.8 and 155.6 ± 45.5s) than in controls (58.08 ± 13.2, 74.3 ± 21.1, 96.7 ± 36.8s; p < 0.001) while the overshoot of PETO₂, VE/VO₂ and RER was significantly lower in patients (7.2 ± 3.3, 41.9 ± 29.1 and 25.0 ± 13.6%) than in controls (10.1 ± 4.6, 62.1 ± 17.7 and 38.7 ± 15.1%; all p < 0.01). Most of the recovery metrics were significantly correlated with peak VO₂ in CHF patients, but not with LVEF.

Conclusions

Patients with CHF have a significantly blunted recovery from peak exercise. This is reflected in delays of VO₂, VCO₂, VE, PETO₂, RER and VE/VO₂, reflecting a greater energy required to return to baseline. Abnormal respiratory gas kinetics in CHF was negatively correlated with peak VO₂ but not baseline LVEF.

Keywords
Respiratory exchange ratio (RER); Cardiopulmonary exercise testing; Oxygen uptake; Carbon dioxide production; Overshoot

	CHF	Controls	p-value
Sex (F)	11 (34.4%)	14 (46.7%)	0.32
Age (yrs)	46.8 ± 13.0	43.1 ± 12.2	0.24
BMI (Kg/m²)	27.9 ± 5.0	24.5 ± 2.9	0.002
Peak VO₂ (mL/min)	1134.9 ± 419.4	2407.5 ± 787.2	<0.001
*Peak VO₂ (mL/Kgmin⁻¹)**	13.5 ± 3.8	32.5 ± 9.8	<0.001
Peak RER	1.04 ± 0.09	1.16 ± 0.08	<0.001
LVEF (%)	35.9 ± 9.8	61.1 ± 8.2	<0.001
Weber's Class
A	1 (3%)
B	10 (31%)
C	13 (41%)
D	8 (25%)
Peak VCO₂ (mL/min)	1196.7 ± 492.7	2783.5 ± 887.0	<0.001
Peak VE (L/min)	42.5 ± 16.1	89.1 ± 33.1	<0.001
VE/VCO₂ slope	37.1 ± 10.7	29.7 ± 4.0	<0.001
VO₂/HR	9.7 ± 3.1	14.7 ± 4.5	<0.001

	Patients	Controls	p
Average recovery (s)	248.8 ± 39.9	264.0 ± 29.3	<0.01
T1/2 VO₂ (s)	111.3 ± 51.0	58.0 ± 13.2	<0.001
T1/2 VCO₂ (s)	132.0 ± 38.8	74.3 ± 21.1	<0.001
T1/2 VE (s)	155.6 ± 45.5	96.7 ± 36.8	<0.001
Overshoot of PETO₂ (%)	7.2 ± 3.3	10.1 ± 4.6	0.007
Overshoot of VE/VO₂ (%)	41.9 ± 29.1	62.1 ± 17.7	0.002
Overshoot of RER (%)	25.0 ± 13.6	38.7 ± 15.1	<0.001

	T_1/2 VO₂	T_1/2 VCO₂	T_1/2 VE	PETO₂ Mag	VE/VO₂ Mag	RER Mag
Age	‒	‒	‒	‒	‒	‒
BMI	‒	‒	‒	‒	‒	‒
Peak VO₂ (mL/min)	‒	‒	‒	‒	0.447^a a Correlation is significant at the 0.05 level.	0.580^b b Correlation is significant at the 0.01 level.
Peak VO₂ (mL/Kg/min)	-0.732^b b Correlation is significant at the 0.01 level.	-0.604^b b Correlation is significant at the 0.01 level.	-0.473^a a Correlation is significant at the 0.05 level.	0.531^b b Correlation is significant at the 0.01 level.	0.604^b b Correlation is significant at the 0.01 level.	0.789^b b Correlation is significant at the 0.01 level.
Peak VCO₂ (mL/min)	‒	‒	‒	‒	0.415^a a Correlation is significant at the 0.05 level.	0.526^b b Correlation is significant at the 0.01 level.
Peak RER	‒	‒	‒	‒	‒	‒
Peak VE	‒	‒	‒	‒	‒	0.495^b b Correlation is significant at the 0.01 level.
VE/VCO₂ Slope	‒	‒	‒	-0.472^b b Correlation is significant at the 0.01 level.	‒	‒
LVEF	‒	‒	‒	‒	‒	‒
VO₂/HR	-0.406^b b Correlation is significant at the 0.01 level.	-0.451^b b Correlation is significant at the 0.01 level.	-0.425^b b Correlation is significant at the 0.01 level.	‒	0.312^a a Correlation is significant at the 0.05 level.	0.617

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[1] * Corresponding author. E-mail address;christle@stanford.edu (J.W. Christle).