Cardiorespiratory Responses to Voluntary Hyperventilation During Normobaric Hypoxia.

BACKGROUND: Unexplained physiological events (PE), possibly related to hypoxia and hyperventilation, are a concern for some air forces. Physiological monitoring could aid research into PEs, with measurement of arterial oxygen saturation (Spo2) often suggested despite potential limitations in its use. Given similar physiological responses to hypoxia and hyperventilation, the present study characterized the cardiovascular and respiratory responses to each.METHODS: Ten healthy subjects were exposed to 55 mins of normobaric hypoxia simulating altitudes of 0, 8000, and 12,000 ft (0, 2438, and 3658 m) while breathing normally and voluntarily hyperventilating (doubling minute ventilation). Respiratory gas analysis and spirometry measured end-tidal gases (PETo2 and PETco2) and minute ventilation. Spo2 was assessed using finger pulse oximetry. Mean arterial, systolic, and diastolic blood pressure were measured noninvasively. Cognitive impairment was assessed using the Stroop test.RESULTS: Voluntary hyperventilation resulted in a doubling of minute ventilation and lowered PETco2, while altitude had no effect on these. PETo2 and Spo2 declined with increasing altitude. However, despite a significant drop in PETo2 of 15.2 mmHg from 8000 to 12,000 ft, Spo2 was similar when hyperventilating (94.7 ± 2.3% vs. 93.4 ± 4.3%, respectively). The only cardiovascular response was an increase in heart rate while hyperventilating. Altitude had no effect on cognitive impairment, but hyperventilation did.DISCUSSION: For many cardiovascular and respiratory variables, there is minimal difference in responses to hypoxia and hyperventilation, making these challenging to differentiate. Spo2 is not a reliable marker of environmental hypoxia in the presence of hyperventilation and should not be used as such without additional monitoring of minute ventilation and end-tidal gases.Haddon A, Kanhai J, Nako O, Smith TG, Hodkinson PD, Pollock RD. Cardiorespiratory responses to voluntary hyperventilation during normobaric hypoxia. Aerosp Med Hum Perform. 2023; 94(2):59-65.

Chronic Total Occlusion of the Left Main Coronary Artery in an HIV-Infected Patient.

Coronary artery disease (CAD) is amongst the leading causes of death in human immunodeficiency virus (HIV)-infected persons. Severe left main disease (LMD) occurs in approximately five percent of HIV-infected patients, with chronic total occlusion (CTO) of this vessel being an even rarer phenomenon. We describe a non-adherent HIV-infected patient with a left main coronary artery (LMCA) CTO that presented with heart failure with mildly reduced ejection fraction (HFrEF) and ventricular tachycardia (VT).

Experimental evaluation of ethanolic extract of Carapa guianensis L. Leaf for its wound healing activity using three wound models.

The leaves of Carapa guianensis have been used to treat ulcers, skin parasites, and skin problems. The ethanolic extract of C. guianensis leaf was evaluated for its antibacterial and wound healing activity using excision, incision and dead space wound models in rats. The animals were randomly divided into two groups (n = 6) in all the models. In the excision wound model test group animals were treated topically with the leaf extract (250 mg kg(-1) body weight) whereas, control animals were treated with petroleum jelly. In the incision and dead space wound models, the test group animals were treated with extract (250 mg kg(-1) day(-1)) orally by mixing in drinking water and the control group animals were maintained with plain drinking water. Healing was assessed by the rate of wound contraction, period of epithelialization, skin breaking strength, granulation tissue weight and hydoxyproline content. On Day 15 extract-treated animals exhibited 100% reduction in the wound area when compared to controls (95%) with significant decrease in the epithelialization period. The extract failed to demonstrate antibacterial activity. Skin breaking strength (P < .001), wet (P < .002) and dry (P < .02) granulation tissue and hydroxyproline content (P < .03) were significantly higher in extract treated animals. The increased rate of wound contraction, skin breaking strength and hydroxyproline content supports potential application of C. guianensis in wound healing.

Investigation of the wound healing activity of Carapa guianensis L. (Meliaceae) bark extract in rats using excision, incision, and dead space wound models

The objective of our study is to investigate the wound healing activity of the bark extract of Carapa guianensis in rats using three different wound models. The animals were randomly divided into two groups of six each in all the models. Test group animals were treated topically with the bark extract (200 mg/kg of body weight), and the controls were treated with petroleum jelly in the excision wound model. In the incision and dead space wound models the test group animals were treated with the extract of C. guianensis (200 mg/kg/day) orally by mixing in drinking water, and the control group animals were maintained with plain drinking water. Healing was assessed by the rate of wound contraction, period of epithelialization, skin breaking strength, granulation tissue weight, and hydoxyproline content. Antimicrobial activities of the extract against the microorganisms were also assessed. On day 15 extract-treated animals exhibited 99% reduction in the wound area compared to controls (93%). The extract-treated wounds were found to epithelialize faster than controls (P < .02). The skin breaking strength was significantly higher in extract-treated animals compared to controls (P < .001). The weight and hydroxyproline content of granulation tissue were significantly increased compared to controls. These observations support the use of C. guianensis is in the management of wound healing.

Investigation of the wound healing activity of Carapa guianensis L. (Meliaceae) bark extract in rats using excision, incision, and dead space wound models.

The objective of our study is to investigate the wound healing activity of the bark extract of Carapa guianensis in rats using three different wound models. The animals were randomly divided into two groups of six each in all the models. Test group animals were treated topically with the bark extract (200 mg/kg of body weight), and the controls were treated with petroleum jelly in the excision wound model. In the incision and dead space wound models the test group animals were treated with the extract of C. guianensis (200 mg/kg/day) orally by mixing in drinking water, and the control group animals were maintained with plain drinking water. Healing was assessed by the rate of wound contraction, period of epithelialization, skin breaking strength, granulation tissue weight, and hydoxyproline content. Antimicrobial activities of the extract against the microorganisms were also assessed. On day 15 extract-treated animals exhibited 99% reduction in the wound area compared to controls (93%). The extract-treated wounds were found to epithelialize faster than controls (P < .02). The skin breaking strength was significantly higher in extract-treated animals compared to controls (P < .001). The weight and hydroxyproline content of granulation tissue were significantly increased compared to controls. These observations support the use of C. guianensis is in the management of wound healing.