doppler-ultrasound-based-leg-blood-flow-assessment-during-single-leg

Doppler Ultrasound-Based Leg Blood Flow Assessment During Single-Leg Knee-Extensor Exercise in an Uncontrolled Setting

Doppler ultrasound has revolutionized the assessment of organ blood flow and is widely used in research and clinical settings. While Doppler ...

dual-test-gas-pulmonary-diffusing-capacity-measurement-during

Dual Test Gas Pulmonary Diffusing Capacity Measurement During Exercise in Humans Using the Single-Breath Method

The combined single-breath measurement of the diffusing capacity of carbon monoxide (DL,CO) and nitric oxide (DL,NO) is a useful technique to measure ...

Copenhagen University Hospital

University of Copenhagen

Copenhagen University Hospital - Rigshospitalet

What is the topic of this review? The use of proning for improving pulmonary gas exchange in critically ill patients. What advances does it highlight? Proning places the lung in its 'natural' posture, and thus optimises the ventilation-perfusion distribution, which enables lung protective ventilation and the alleviation of potentially life-threatening hypoxaemia in COVID-19 and other types of critical illness with respiratory failure.

Therapeutic benefits of proning to improve pulmonary gas exchange in severe respiratory failure: focus on fundamentals of physiology.

 Skeletal muscle convective and diffusive oxygen (O) transport are peripheral determinants of exercise capacity in both patients with chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF). We hypothesised that differences in these peripheral determinants of performance between COPD and CHF patients are revealed during small muscle mass exercise, where the cardiorespiratory limitations to exercise are diminished.  Eight patients with moderate to severe COPD, eight patients with CHF (NYHA II), and eight age- and sex-matched controls were studied. We measured leg blood flow (Q̇) by Doppler ultrasound during submaximal one-legged knee-extensor exercise (KEE), while sampling arterio-venous variables across the leg. The capillary oxyhaemoglobin dissociation curve was reconstructed from paired femoral arterial-venous oxygen tensions and saturations, which enabled the estimation of O parameters at the microvascular level within skeletal muscle, so that skeletal muscle oxygen conductance (DO) could be calculated and adjusted for flow (DO/Q̇) to distinguish convective from diffusive oxygen transport.  During KEE, Q̇ increased to a similar extent in CHF (2.0 (0.4) L/min) and controls (2.3 (0.3) L/min), but less in COPD patients (1.8 (0.3) L/min) ( <0.03). There was no difference in resting DO between COPD and CHF and when adjusting for flow, the DO was higher in both groups compared to controls (COPD: 0.97 (0.23) vs. controls 0.63 (0.24) mM/kPa, = 0.02; CHF 0.98 (0.11) mM/kPa vs. controls, = 0.001). The Q̇-adjusted DO was not different in COPD and CHF during KEE (COPD: 1.19 (0.11) vs. CHF: 1.00 (0.18) mM/kPa; = 0.24) but higher in COPD vs. controls: 0.87 (0.28) mM/kPa (= 0.02), and only CHF did not increase Q̇-adjusted DO from rest (= 0.2).  Disease-specific factors may play a role in peripheral exercise limitation in patients with COPD compared with CHF. Thus, low convective O transport to contracting muscle seemed to predominate in COPD, whereas muscle diffusive O transport was unresponsive in CHF.

Regulation of the microvasculature during small muscle mass exercise in chronic obstructive pulmonary disease vs. chronic heart failure.

What is the central question in this study? How reliable is the combined measurement of the pulmonary diffusing capacity to carbon monoxide and nitric oxide (D ) during exercise and in the resting supine position, respectively? What is the main finding and its importance? The D technique is reliable with a very low day-to-day variability both during exercise and in the resting supine position, and may thus provide a useful physiological outcome that reflects the alveolar-capillary reserve in humans.

ArticleTotal : 2	Year
Publication title	2023
Publication title	2024

Article	Year
Therapeutic benefits of proning to improve pulmonary gas exchange in severe respiratory failure: focus on fundamentals of physiology. Experimental physiology\| PubMed ID: 34242438	2022
Regulation of the microvasculature during small muscle mass exercise in chronic obstructive pulmonary disease vs. chronic heart failure. Frontiers in physiology\| PubMed ID: 36134330	2022
Pulmonary diffusing capacity to nitric oxide and carbon monoxide during exercise and in the supine position: a test-retest reliability study. Experimental physiology\| PubMed ID: 36621806	2023
Physiolometrics and the puzzle of methodical acumen. Experimental physiology\| PubMed ID: 37555751	2023

Jacob Peter Hartmann

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