TITLE:
Dead Space Breathing in Patients with Malignancies: Determination by Cardiopulmonary Exercise Testing
AUTHORS:
Harrison Ngue, Maranda Ngue, Ian Lee, Ching-Fei Chang, Ahmet Baydur
KEYWORDS:
Cardiopulmonary Exercise Testing, Cardiovascular Limitation, Dead Space Breathing, Dyspnea, Malignancies, Oxygen Uptake, Pulmonary Vascular Limitation, Ventilatory Equivalents
JOURNAL NAME:
Open Journal of Respiratory Diseases,
Vol.12 No.1,
February
28,
2022
ABSTRACT: Rationale: Patients with cancer commonly experience dyspnea originating from ventilatory, circulatory and musculoskeletal
sources, and dyspnea is best determined by
cardiopulmonary exercise testing (CPET). Objectives: In this
retrospective pilot study, we
evaluated patients with hematologic and solid malignancies by CPET to determine
the primary source of their dyspnea. Methods: Subjects were exercised on
a cycle ergometer with increasing workloads. Minute ventilation, heart rate,
breathing reserve, oxygen uptake (V’O2), O2-pulse,
ventilatory equivalents for carbon dioxide and oxygen (V’E/V’CO2 and V’E/V’O2, respectively) were measured at baseline and
peak exercise. The slope and intercept for V’E/V’CO2 was
computed for all subjects. Peak V’O2 4% predicted indicated a circulatory or ventilatory
limitation. Results: Complete clinical and physiological data were
available for 36 patients (M/F 20/16); 32 (89%) exhibited ventilatory or
circulatory limitation as shown by a reduced peak V’O2 and 10
subjects with normal physiologic data. The largest cohort comprised the
pulmonary vascular group (n = 18) whose mean ± SD peak V’O2 was 61% ± 17%
predicted. There were close associations between V’O2 and
spirometric values. Peak V’E/V’O2 and V’E/V’CO2 were highest in the circulatory and
ventilatory cohorts, consistent with increase in dead space breathing. The
intercept of the V’E-V’CO2 relationship was lowest in
patients with cardiovascular impairment. Conclusion: Dyspneic patients
with malignancies exhibit dead space breathing, many exhibiting a circulatory
source for exercise limitation with a prominent pulmonary vascular component. Potential
factors include effects of chemo- and radiation therapy on cardiac function and
pulmonary vascular endothelium.