Cardiorespiratory Optimal Point: A Submaximal Exercise Variable to Assess Panic Disorder Patients

Abstract

Panic disorder (PD) patients often report respiratory symptoms and tend to perform poorly during maximal cardiopulmonary exercise testing (CPX), at least partially, due to phobic anxiety. Thus, we hypothesized that a submaximal exercise variable, minimum VE/VO2 - hereafter named cardiorespiratory optimal point (COP) -, may be useful in their clinical assessment. Data from 2,338 subjects were retrospectively analyzed and 52 (2.2%) patients diagnosed with PD (PDG) (70% women; aged 48±13 years). PD patients were compared with a healthy control group (CG) precisely matched to number of cases, age and gender profiles. PDG was further divided into two subgroups, based on having achieved a maximal or a submaximal CPX (unwilling to continue until exhaustion). We compared COP, VO2 max, maximum heart rate (HR max) between PDG and CG, and also COP between maximal and submaximal PD subgroups. COP was similar between PDG and CG (21.9±0.5 vs. 23.4±0.6; p = 0.07), as well as, for PD subgroups of maximal and submaximal CPX (22.0±0.5 vs. 21.6±1.3; p = 0.746). Additionally, PD patients completing a maximal CPX obtained VO2 max (mL.kg−1.min−1) (32.9±1.57 vs 29.6±1.48; p = 0.145) and HR max (bpm) similar to controls (173±2.0 vs 168±2.7; p = 0.178). No adverse complications occurred during CPX. Although clinically safe, it is sometimes difficult to obtain a true maximal CPX in PD patients. Normalcy of cardiorespiratory interaction at submaximal effort as assessed by COP may contribute to reassure both patients and physicians that there is no physiological substrate for exercise-related respiratory symptoms often reported by PD patients.

Cardiorespiratory optimal point during exercise testing as a predictor of all-cause mortality

“…COP in fact has several advantages over other CPET variables, considering that it is obtained at relatively low-intensity exercise, i.e., at 30-50% of VO 2 max, 17 and much earlier than VAT, thereby considerably reducing the effort required for clinical assessment. COP in fact has several advantages over other CPET variables, considering that it is obtained at relatively low-intensity exercise, i.e., at 30-50% of VO 2 max, 17 and much earlier than VAT, thereby considerably reducing the effort required for clinical assessment.…”

“…15 The cardiorespiratory optimal point (COP) constitutes a novel submaximal CPET index which provides an alternative approach to respiratory physiology. 16,17 The COP represents the lowest value of the oxygen ventilatory equivalent (the ratio between ventilation [VE] in l/min and oxygen consumption [VO 2 ] in l/min, VE/VO 2 ) in a given minute during incremental exercise. As an index that quantifies the lowest ventilation required to extract 1 l of oxygen, COP characterizes the interplay between the circulatory and respiratory systems.…”

“…16,17 The COP represents the lowest value of the oxygen ventilatory equivalent (the ratio between ventilation [VE] in l/min and oxygen consumption [VO 2 ] in l/min, VE/VO 2 ) in a given minute during incremental exercise. 17 COP is simple to identify and occurs at modest exercise levels (30-50% of VO 2 max), much earlier than VAT. 17 COP is simple to identify and occurs at modest exercise levels (30-50% of VO 2 max), much earlier than VAT.…”

“…As an index that quantifies the lowest ventilation required to extract 1 l of oxygen, COP characterizes the interplay between the circulatory and respiratory systems. 17 While COP has been shown to be reliable 16 and reference values are available, 17 its utility as a clinical prognostic indicator has not been evaluated. 17 While COP has been shown to be reliable 16 and reference values are available, 17 its utility as a clinical prognostic indicator has not been evaluated.…”

Influence of central obesity in estimating maximal oxygen uptake

“…A CPET session was defined as maximum if it was not prematurely terminated due to adverse signs/symptoms and if it fulfilled physiological criteria 8. Additionally, measures of perceived exertion were obtained to assess somatic exhaustion, a score of 10 on the 0-10 Borg scale 9, which was further indicated by the inability to maintain the required pedal cadence (65-75 rev/min) despite strong verbal encouragement.…”