Background
Methods that predict prognosis and response to therapy in pulmonary hypertension (PH) are lacking. We tested whether the noninvasive estimation of hemodynamic parameters during 6MWT in PH patients provides information that can improve the value of the test.
Methods
We estimated hemodynamic parameters during the 6MWT using a portable, signal-morphology based, impedance cardiograph (PhysioFlow Enduro, Paris, France) with real time wireless monitoring via a bluetooth USB adapter.
Results
We recruited 48 subjects in the study (30 with PH and 18 healthy controls). PH patients had significantly lower maximum SV and CI and slower CO acceleration and decelerations slopes during the test when compared with healthy controls. In PH patients, CI change was associated with total distance walked (R=0.62, p<0.001) and percentage of predicted (R=0.4, p=0.03), HR recovery at 1 min (0.57, p<0.001), 2 min (0.65, p<0.001) and 3 min (0.66, p<0.001). Interestingly, in PH patients CO change during the test was predominantly related to an increase in SV instead of HR.
Conclusions
Estimation of hemodynamic parameters such as cardiac index during six-minute walk test is feasible and may provide useful information in patients with pulmonary hypertension.
In the present study, pulse oximetry commonly overestimated the SaO2. Increased carboxyhemoglobin levels are independently associated with the difference between SpO2 and SaO2, a finding particularly relevant in smokers.
In pulmonary function testing by spirometry, bronchodilator responsiveness (BDR) evaluates the degree of volume and airflow improvement in response to an inhaled short-acting bronchodilator (BD). The traditional, binary categorization (present vs absent BDR) has multiple pitfalls and limitations. To overcome these limitations, a novel classification that defines five categories (negative, minimal, mild, moderate and marked BDR), and based on % and absolute changes in forced expiratory volume in 1 s (FEV1), has been recently developed and validated in patients with chronic obstructive pulmonary disease, and against multiple objective and subjective measurements. In this study, working on several large spirometry cohorts from two different institutions (n=31 598 tests), we redefined the novel BDR categories based on delta post-BD–pre-BD FEV1 % predicted values. Our newly proposed BDR partition is based on several distinct intervals for delta post-BD–pre-BD % predicted FEV1 using Global Lung Initiative predictive equations. In testing, training and validation cohorts, the model performed well in all BDR categories. In a validation set that included only normal baseline spirometries, the partition model had a higher rate of misclassification, possibly due to unrestricted BD use prior to baseline testing. A partition that uses delta % predicted FEV1 with the following intervals ≤0%, 0%–2%, 2%–4%, 4%–8% and >8% may be a valid and easy-to-use tool for assessing BDR in spirometry. We confirmed in our cohorts that these thresholds are characterized by low variance and that they are generally gender-independent and race-independent. Future validation in other cohorts and in other populations is needed.
The statements and opinions expressed in COVID-19 Curbside Consults are based on experience and the available literature as of the date posted. While we try to regularly update this content, any offered recommendations cannot be substituted for the clinical judgment of clinicians caring for individual patients.
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