Hypercapnia elicits differential vascular and blood flow responses in the cerebral circulation and active skeletal muscles in exercising humans

Abstract

The purpose of this study was to investigate the effects of a rise in arterial carbon dioxide pressure (PaCO 2 ) on vascular and blood flow responses in the cerebral circulation and active skeletal muscles during dynamic exercise in humans. Thirteen healthy young adults (three women) participated in hypercapnia and normocapnia trials. In both trials, participants performed a two‐legged dynamic knee extension exercise at a constant workload that increased heart rate to roughly 100 beats min −1 . In the hypercapnia trial, participants performed the exercise with spontaneous breathing while end‐tidal carbon dioxide pressure (P ET CO 2 ), an index of PaCO 2 , was held at 60 mmHg by inhaling hypercapnic gas (O 2 : 20.3 ± 0.1%; CO 2 : 6.0 ± 0.5%). In the normocapnia trial, minute ventilation during exercise was matched to the value in the hypercapnia trial by performing voluntary hyperventilation with P ET CO 2 clamped at baseline level (i.e., 40–45 mmHg) through inhalation of mildly hypercapnic gas (O 2 : 20.6 ± 0.1%; CO 2 : 2.7 ± 1.0%). Middle cerebral artery mean blood velocity and the cerebral vascular conductance index were higher in the hypercapnia trial than in the normocapnia trial. By contrast, vascular conductance in the exercising leg was lower in the hypercapnia trial than in the normocapnia trial. Blood flow to the exercising leg did not differ between the two trials. These results demonstrate that hypercapnia‐induced vasomotion in active skeletal muscles is opposite to that in the cerebral circulation. These differential vascular responses may cause a preferential rise in cerebral blood flow.

Brain Oxygenation Response to Hypercapnia in Patients with Acute Brain Injury

“…On a total of 163 eligible patients, we identi ed 23 (14%) patients who underwent moderate hypoventilation (PaCO 2 from 44 [42][43][44][45] to 50 [49-53] mmHg; p < 0.001) during the study period at a median of 6 (4-10) days following ICU admission; 6 patients had traumatic brain injury (TBI) and 17 had subarachnoid hemorrhage (SAH). A signi cant overall increase in median PbtO 2 values from baseline [21 (19-26) to 24 (22-26) mmHg; p = 0.02] was observed.…”

Mass Sportrometry: An annual look back at applications of mass spectrometry in sport and exercise science

“…In 2022, targeted analyses were the most commonly applied approach for MS-based research in SES, with 52 human participant studies published. These experiments were predominantly performed in plasma 6,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] or serum, [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] with other biosamples mediums utilized such as urine, [51][52][53][54][55] fecal matter, 56,57 breath gases, [58][59][60][61][62][63] red blood cells, …”

“…In 2022, targeted analyses were the most commonly applied approach for MS‐based research in SES, with 52 human participant studies published. These experiments were predominantly performed in plasma 6,16–35 or serum, 36–50 with other biosamples mediums utilized such as urine, 51–55 fecal matter, 56,57 breath gases, 58–63 red blood cells, 64 cerebrospinal fluid, 25 hair, 65 and whole blood via microsampling 66 . This excludes the use of IR and elemental MS to target specific isotope/elemental signatures, which are discussed individually within section 3.5.…”

“…In 2022, targeted analyses were the most commonly applied approach for MS‐based research in SES, with 52 human participant studies published. These experiments were predominantly performed in plasma 6 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 or serum, 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 with other biosamples mediums utilized such as urine, 51 , 52 , 53 , 54 , 55 fecal matter, 56 , 57 breath gases, 58 , 59 , 60 , 61 , …”

The effect of intraoperative transnasal humidified rapid-insufflation ventilatory exchange on emergence from general anesthesia in patients undergoing microlaryngeal surgery: a randomized controlled trial

“…Hypercapnia is considered organ-protective compared to hypocapnia [ 17 ], and in some cases, it is well tolerated in anesthetized patient [ 18 ]. Hypercapnia may lead to hemodynamic instability and may influence emergence from anesthesia [ 19 – 24 ]. The current evidence showed that compared with mechanical ventilation through an endotracheal tube, using THRIVE in short duration surgery was not associated with obvious intraoperative adverse events [ 3 , 25 , 26 ].…”