Taylor, Bryan J

Aging is associated with deterioration in the structure and function of the pulmonary circulation. We characterized the lung diffusing capacity for carbon monoxide (DLCO), alveolar-capillary membrane conductance (DmCO), and pulmonary-capillary blood volume (Vc) response to discontinuous incremental exercise at 25, 50, 75, and 90% of peak work (Wpeak) in four groups: 1) Young [27 ± 3 yr, maximal oxygen consumption (V̇o2max): 110 ± 18% age predicted]; 2) Young Highly Fit (27 ± 3 yr, V̇o2max: 147 ± 8% age predicted); 3) Old (69 ± 5 yr, V̇o2max: 116 ± 13% age predicted); and 4) Old Highly Fit (65 ± 5 yr, V̇o2max: 162 ± 18% age predicted). At rest and at 90% Wpeak, DLCO, DmCO, and Vc were decreased with age. At 90% Wpeak, DLCO, DmCO, and Vc were greater in Old Highly Fit vs. Old adults. The slope of the DLCO-cardiac output (Q̇) relationship from rest to end exercise at 90% Wpeak was not different between Young, Young Highly Fit, Old, and Old Highly Fit (1.35 vs. 1.44 vs. 1.10 vs. 1.35 mlCO·mmHg−1·liter blood−1, P = 0.388), with no evidence of a plateau in this relationship during exercise; this was also true for DmCO-Q̇ and Vc-Q̇. V̇o2max was positively correlated with 1) DLCO, DmCO, and Vc at rest; and 2) the rest to end exercise change in DLCO, DmCO, and Vc. In conclusion, these data suggest that despite the age-associated deterioration in the structure and function of the pulmonary circulation, expansion of the pulmonary capillary network does not become limited during exercise in healthy individuals regardless of age or cardiorespiratory fitness level. NEW & NOTEWORTHY Healthy aging is a crucial area of research. This article details how differences in age and cardiorespiratory fitness level affect lung diffusing capacity, particularly during high-intensity exercise. We conclude that highly fit older adults do not experience a limit in lung diffusing capacity during high-intensity exercise. Interestingly, however, we found that highly fit older individuals demonstrate greater values of lung diffusing capacity during high-intensity exercise than their less fit age-matched counterparts.

Objective It is well documented that cognitive performance may be altered with ascent to altitude, but the association of various cognitive performance tests with symptoms of acute mountain sickness (AMS) is not well understood. Our objective was to assess and compare cognitive performance during a high-altitude expedition using several tests and to report the association of each test with AMS, headache, and quality of sleep. Methods During an expedition to Mount Everest, 3 cognitive tests (Stroop, Trail Making, and the real-time cognitive assessment tool, an in-house developed motor accuracy test) were used along with a questionnaire to assess health and AMS. Eight team members were assessed pre-expedition, postexpedition, and at several time points during the expedition. Results There were no significant differences ( P >.05) found among scores taken at 3 time points at base camp and the postexpedition scores for all 3 tests. Changes in the Stroop test scores were significantly associated with the odds of AMS ( P <.05). The logistic regression results show that the percent change from baseline for Stroop score (β = −5.637; P = .032) and Stroop attempts (β = −5.269; P = .049) are significantly associated with the odds of meeting the criteria for AMS. Conclusions No significant changes were found in overall cognitive performance at altitude, but a significant relationship was found between symptoms of AMS and performance in certain cognitive tests. This research shows the need for more investigation of objective physiologic assessments to associate with self-perceived metrics of AMS to gauge effect on cognitive performance.

We determined whether a non-invasive gas exchange based estimate of pulmonary vascular (PV) capacitance [PV CAP = stroke volume (SV) x pulmonary arterial pressure (Ppa)] (GX CAP ) tracked the PV response to exercise in heart-failure (HF) patients. Pulmonary wedge pressure (Ppw), Ppa, PV resistance (PVR), and gas exchange were measured simultaneously during cycle exercise in 42 HF patients undergoing right-heart catheterization. During exercise, P ET CO 2 and V E /VCO 2 were related to each other ( r= -0.93, P < 0.01) and similarly related to mean Ppa (mPpa) ( r = -0.39 and 0.36; P < 0.05); P ET CO 2 was subsequently used as a metric of mPpa. Oxygen pulse (O 2 pulse) tracked the SV response to exercise (r = 0.91, P < 0.01). Thus, GX CAP was calculated as O 2 pulse x P ET CO 2 . During exercise, invasively determined PV CAP and non-invasive GX CAP were related (r = 0.86, P < 0.01), and GX CAP correlated with mPpa and PVR (r = -0.46 and -0.54; P < 0.01). In conclusion, noninvasive gas exchange measures may represent a simple way to track the PV response to exercise in HF.

Objective Although the majority of high altitude studies have used doubly labeled water to assess energy expenditure (EE), minimal research has examined variation in intensity levels while participating in such an expedition. The purpose of this study was to use ambulatory monitoring technology to assess EE and time spent in moderate (3.0–6.0 METS), vigorous (6.0–9.0 METS), and very vigorous (>9.0 METS) intensities during an expedition to summit a 6170-m peak in Northern Pakistan. Methods Twelve men and 2 women were studied. Their EE was determined from galvanic skin response, heat flux, and biaxial accelerometry using a multisensor armband. Lake Louise Scores for altitude illness assessment were obtained each morning. Results Average daily total EE and number of steps taken was 4173 ± 848 kcal/d (range, 3332 to 4838 kcal/d) and 26,232 ± 7210 steps/d (range, 11,788 to 34,979 steps/d), respectively. On average, subjects spent approximately 7.7 h/d performing physical activity (>3.0 METS). Of this, subjects spent 399 ± 107, 61 ± 77, and 3 ± 10 min/d at moderate, vigorous, and very vigorous intensity levels, respectively, corresponding to 88%, 11%, and 1% of total physical activity time. During summit day, subjects climbed at an intensity equivalent to approximately 42% of their high altitude predicted maximal oxygen consumption at 5100 m). Conclusions During a high altitude expedition, subjects predominantly exercise at a moderate intensity, with limited time spent at higher intensity levels. Use of accelerometer-based technology may provide more cost-effective and logistically easier means of assessing EE in extreme environments.

To determine whether expiratory muscle fatigue (EMF) is involved in regulating operating lung volumes during exercise, nine recreationally active subjects cycled at 90% of peak work rate to the limit of tolerance with prior induction of EMF (EMF-ex) and for a time equal to that achieved in EMF-ex without prior induction of EMF (ISO-ex). EMF was assessed by measuring changes in magnetically evoked gastric twitch pressure. Changes in end-expiratory and end-inspiratory lung volume (EELV and EILV) and the degree of expiratory flow limitation (EFL) were quantified using maximal expiratory flow-volume curves and inspiratory capacity maneuvers. Resistive breathing reduced gastric twitch pressure (−24 ± 14%, P = 0.004). During EMF-ex, EELV decreased from rest to the 3rd min of exercise [39 ± 8 vs. 27 ± 7% of forced vital capacity (FVC), P = 0.001] before increasing toward baseline (34 ± 8% of FVC end exercise, P = 0.073 vs. rest). EILV increased from rest to the 3rd min of exercise (54 ± 8 vs. 84 ± 9% of FVC, P = 0.006) and remained elevated to end exercise (88 ± 9% of FVC). Neither EELV ( P = 0.18) nor EILV ( P = 0.26) was different at any time point during EMF-ex vs. ISO-ex. Four subjects became expiratory flow limited during the final minute of EMF-ex and ISO-ex; the degree of EFL was not different between trials (37 ± 18 vs. 35 ± 16% of tidal volume, P = 0.38). At end exercise in both trials, EELV was greater in subjects without vs. subjects with EFL. These findings suggest that 1) contractile fatigue of the expiratory muscles in healthy humans does not regulate operating lung volumes during high-intensity sustained cycle exercise; and 2) factors other than “frank” EFL cause the terminal increase in EELV.