Validation of a Noninvasive Assessment of Pulmonary Gas Exchange During Exercise in Hypoxia

Howe, Connor A.; MacLeod, David B.; Wainman, Liisa; Oliver, Samuel J.; Ainslie, Philip N.

doi:10.1016/j.chest.2020.04.017

Cited by 13 publications

(14 citation statements)

References 22 publications

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“…Pulmonary gas exchange Pulmonary gas exchange efficiency was evaluated and indexed via the O 2 deficit -the difference between the end-tidal and the calculated arterial P O 2 (via pulse oximetry and corrected for the Bohr effect by using the end-tidal P CO 2 ; AGM100, MediPines Corp., Yorba Linda, CA, USA). The O 2 deficit compares well with the traditional ideal alveolararterial P O 2 difference (A − aD O 2 ) calculated from arterial blood gases, and has been validated in a variety of healthy and patient populations (West et al, 2019) and during exercise (Howe et al, 2020)). In the normal healthy lung, there exists regional differences in ventilationperfusion matching, which varies depending on whether the individual is upright (West, 1962) or supine (Wagner et al, 1974).…”

Section: Experimental Measuresmentioning

confidence: 74%

Temporal changes in pulmonary gas exchange efficiency when breath‐hold diving below residual volume

Patrician

Spajić

Gasho

et al. 2021

Experimental Physiology

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Breath-hold diving involves highly integrative and extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. Over two diving training camps (Study 1 and 2), 25 breath-hold divers (recreational to worldchampion) performed 66 dives to 57 ± 20 m (range: 18-117 m). Using the deepest dive from each diver, temporal changes in cardiopulmonary function were assessed using non-invasive pulmonary gas exchange (indexed via the O 2 deficit), ultrasound B-line scores, lung compliance and pulmonary haemodynamics at baseline and following the dive. Hydrostatically induced lung compression was quantified in Study 2, using spirometry and lung volume measurement, enabling each dive to be categorized by its residual volume (RV)-equivalent depth. From both studies, pulmonary gas exchange inefficiency-defined as an increase in O 2 deficit-was related to the depth of the dive (r 2 = 0.345; P < 0.001), with dives associated with lung squeeze symptoms exhibiting the greatest deficits. In Study 1, although B-lines doubled from baseline (P = 0.027), cardiac output and pulmonary artery systolic pressure were unchanged post-dive. In Study 2, dives with lung compression to ≤RV had higher O 2 deficits at 9 min, compared to dives that did not exceed RV (24 ± 25 vs. 5 ± 8 mmHg; P = 0.021). The physiological significance of a small increase in estimated lung compliance post-dive (via decreased and increased/unaltered airway resistance and reactance, respectively) remains equivocal. Following deep dives, the current study highlights an integrated link between hydrostatically induced lung compression and transient impairments in pulmonary gas exchange efficiency.

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Section: Experimental Measuresmentioning

confidence: 74%

Temporal changes in pulmonary gas exchange efficiency when breath‐hold diving below residual volume

Patrician

Spajić

Gasho

et al. 2021

Experimental Physiology

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“…The measurement of oxygen deficit encompasses the effects of low VA/Q and high VA/Q, although the effect of high VA/Q regions on arterial PO 2 is small because of the shape of the O 2 -Hb dissociation curve. The large overlap in the areas of influence of the two methods ( Figure 2 ) means that the two measurements would be expected to be highly correlated, albeit not the same, and this was demonstrated with a strong correlation between measures of A-aDO 2 and OD ( West et al, 2018c ; Howe et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

“…A recent study has also demonstrated the validity of the non-invasive approach to measure a gas exchange deficit. A direct comparison between OD and arterial blood gas (ABG) was performed in 25 normal subjects during hypoxic exercise, showing a correlation between OD and A-aDO 2 with an r 2 =0.71, and with a small bias between the two, with OD being on average 5.2±5.0mmHg higher than A-aDO 2 ( Howe et al, 2020 ). The non-invasive nature of the measurement serves to enable measurements in conditions in where it would be challenging to perform ABGs, and in particular, serial ABGs.…”

Section: Oxygen Deficit In Normal Subjectsmentioning

confidence: 99%

Non-invasive Measurement of Pulmonary Gas Exchange Efficiency: The Oxygen Deficit

Prisk

West

2021

Front. Physiol.

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The efficiency of pulmonary gas exchange has long been assessed using the alveolar-arterial difference in PO2, the A-aDO2, a construct developed by Richard Riley ~70years ago. However, this measurement is invasive (requiring an arterial blood sample), time consuming, expensive, uncomfortable for the patients, and as such not ideal for serial measurements. Recent advances in the technology now provide for portable and rapidly responding measurement of the PO2 and PCO2 in expired gas, which combined with the well-established measurement of arterial oxygen saturation via pulse oximetry (SpO2) make practical a non-invasive surrogate measurement of the A-aDO2, the oxygen deficit. The oxygen deficit is the difference between the end-tidal PO2 and the calculated arterial PO2 derived from the SpO2 and taking into account the PCO2, also measured from end-tidal gas. The oxygen deficit shares the underlying basis of the measurement of gas exchange efficiency that the A-aDO2 uses, and thus the two measurements are well-correlated (r2~0.72). Studies have shown that the new approach is sensitive and can detect the age-related decline in gas exchange efficiency associated with healthy aging. In patients with lung disease the oxygen deficit is greatly elevated compared to normal subjects. The portable and non-invasive nature of the approach suggests potential uses in first responders, in military applications, and in underserved areas. Further, the completely non-invasive and rapid nature of the measurement makes it ideally suited to serial measurements of acutely ill patients including those with COVID-19, allowing patients to be closely monitored if required.

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“…A-aDO 2 and RI can evaluate the pulmonary ventilation function reliably. In addition, A-aDO 2 is a sensitive indicator of pulmonary diffusion function and pulmonary gas exchange e ciency in the early stage of ventilation insu ciency [24,25]. OI indicates the lung ventilation function and oxygen utilization, is directly proportional to lung function.…”

Section: Discussionmentioning

confidence: 99%

Transcutaneous Electrical Acupoint Stimulation Attenuates Lung Injury Caused by Tourniquet-induced Limb Ischemia/reperfusion During Lower Extremity Surgery: A Randomized Controlled Trial

Gong

Zhao

et al. 2020

Preprint

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Background: Tourniquet-induced extremity ischemia-reperfusion injury is one of the major complications in patients with lower extremity surgery, while lung is the most vulnerable organ to insult subsequent to ischemia-reperfusion. Current scientific research data has shown that electric stimulation at special acupoints could suppress inflammasome activation and subsequently exert protective effects in the lungs. Thus, the effect of transcutaneous electrical acupuncture point stimulation (TEAS) on lung injury induced by limb ischemia/reperfusion remains to be elucidated. Methods: One hundred individuals scheduled for unilateral lower extremity surgery were randomly divided into 2 groups (n=50 each): transcutaneous electrical acupoint stimulation group (group T) and control group (group C). Patients in group T were given TEAS at FeiShu (BL13, bilateral) acupoints and ZuSanLi (ST36, non-surgical side) acupoint, while patients in group C received sham stimulation (no current) at the same acupoints for the same time as the TEAS group. Arterial blood samples were collected to assess blood gas analysis and other indicators. Results: The TEAS group showed significant improvements in blood gas analysis. Compared with group C, PaO2 and oxygenation index (OI) in group T were significantly increased at T4(4h after removing the tourniquet), while A-aDO2 and respiratory index (RI) were decreased at T4. There was an increase in the HO-1 levels in group T at T3(2h after removing the tourniquet) and T4 compared with group C. Compared with group T, SOD levels were signiﬁcantly lower at T4 in group C. At T4, the levels of ICAM-1, IL-6 and IL8 were significantly lower in group T when compared to group C. At T3 and T4, IL-10 levels were higher when compared to group C, while TNF-a levels were significantly lower.Conclusions: Transcutaneous electrical acupoint stimulation attenuates lung injury following tourniquet-induced extremity ischemia-reperfusion in patients, and HO-1 is endowed of potential mechanism of cytoprotective effects against tourniquet-induced lung injury. Trial registration: Chinese Clinical Trial Registry, ChiCTR-IOR-16008264. Registered 11 April 2016, http://www.chictr.org.cn/ ChiCTR-IOR-16008264

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Validation of a Noninvasive Assessment of Pulmonary Gas Exchange During Exercise in Hypoxia

Abstract: Validation of a Non-invasive Assessment of Pulmonary Gas Exchange During Exercise in 2 Hypoxia 3 4 Running Head: Non-invasive pulmonary gas exchange in hypoxic exercise 5

Cited by 13 publications

References 22 publications

Temporal changes in pulmonary gas exchange efficiency when breath‐hold diving below residual volume

Temporal changes in pulmonary gas exchange efficiency when breath‐hold diving below residual volume

Non-invasive Measurement of Pulmonary Gas Exchange Efficiency: The Oxygen Deficit

Transcutaneous Electrical Acupoint Stimulation Attenuates Lung Injury Caused by Tourniquet-induced Limb Ischemia/reperfusion During Lower Extremity Surgery: A Randomized Controlled Trial

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