Physical dilatation of the nostrils lowers the thermal strain of exercising humans

Facial Blood Flow Responses to Dynamic Exercise

We reported previously that a static handgrip exercise evoked regional differences in the facial blood flow. The present study examined whether regional differences in facial blood flow are also evoked during dynamic exercise. Facial blood flow was measured by laser speckle flowgraphy during 15 min of cycling exercise at heart rates of 120 bpm, 140 bpm and 160 bpm in 12 subjects. The facial vascular conductance index was calculated from the blood flow and mean arterial pressure. The regional blood flow and conductance index values were determined in the forehead, eyelid, nose, cheek, ear and lip. One-way ANOVA and Tukey's post-hoc test were used to examine effects of exercise intensity and target regions. The blood flow and conductance index in skin areas increased significantly with the exercise intensity. The blood flow and conductance index in the lip increased significantly at 120 bpm and 140 bpm compared to the control, while the values in the lip at 160 bpm did not change from the control values. These results suggest that the blood flow in facial skin areas, not in the lip, responds similarly to dynamic exercise, in contrast to the responses to static exercise.

Thermoregulation following spinal cord injury

Spinal cord injury results in physiologic adaptations affecting heat production (reduced muscle mass) and heat dissipation (blood redistribution and reduced sweating capacity below the level of lesion). However, it is the balance between these factors which determines whether heat balance is achieved. Core temperature estimates are generally consistent with those for the able-bodied, with cooler values reported in some instances. More notable differences are demonstrated through cooler lower-body skin temperatures at rest and a loss of anticipatory control during exposure to heat and cold when compared to the able-bodied. During exercise in cool conditions persons with paraplegia demonstrate similar body temperature responses as for the able-bodied but retain heat during recovery. Persons with tetraplegia demonstrate continual increases in core temperature and thus thermal imbalance along with greater heat retention. During exercise in the heat, athletes with paraplegia appear to be able to regulate body temperature to a similar extent as the able-bodied. Those with tetraplegia again show thermal imbalance but to a much greater extent than in the cold. Future work should focus upon specific sweating responses and adaptations following spinal cord injury, the effects of completeness of lesion, perceptual responses to environmental challenges, and how these translate to undertaking activities of daily living.

Transnasal cooling: a Pandora's box of transnasal patho-physiology

The innovative concept of transnasal evaporative cooling for therapeutic hypothermia in cardio-pulmonary-cerebro-resuscitation has therapeutic implications with evidence of rapid and selective brain cooling; however, this author wants to elicit that this concept may hold answers for many physiological phenomena which have not been explored or completely understood up till now. To affirm the physiological role of transnasal cooling, the innovative non-invasive brain temperature monitoring can help the investigators to explore and understand the following transnasal pathophysiological phenomena: (1) understanding correlation of brain temperature and sinus headache secondary to nasal blockade, (2) exploring the therapeutic role of nasal oxygen for prevention of delirium in intubated patients, (3) realizing the impact of controlled enclosed environments on the mood and affect of the inhabitants, (4) understanding the etio-pathogenesis of claustrophobia after excluding the confounding factors of morbid obesity, severe cardiopulmonary disease and incapacitating musculoskeletal diseases, (5) exploring the anthropological role of male pattern of moustache, beard and hair loss, and (6) possible development of a coolant moustache as proposed by the author. In summary, transnasal pathophysiology offers many promising lines of fruitful research to explore the non-olfactory physiological functions of nose in human beings.

Decrease of resistance to air flow with nasal strips as measured with the airflow perturbation device

Background

Nasal strips are used by athletes, people who snore, and asthmatics to ease the burden of breathing. Although there are some published studies that demonstrate higher flow with nasal strips, none had directly measured the effect of the strips on nasal resistance using the airflow perturbation device (APD). The APD is an inexpensive instrument that can measure respiratory resistance based on changes in mouth pressure and rate of airflow.

Method

This study tested forty-seven volunteers (14 men and 33 women), ranging in age from 17 to 51. Each volunteer was instructed to breathe normally into the APD using an oronasal mask with and without nasal strips. The APD measured respiratory resistance during inhalation, exhalation, and an average of the two.

Results

Results of a paired mean t-test comparing nasal strip against no nasal strip were statistically significant at the p = 0.05 level. The Breathe Right™ nasal dilator strips lowered nasal resistance by an average of 0.5 cm H₂0/Lps from an average nasal resistance of 5.5 cm H₂0/Lps.

Conclusions

Nasal strips reduce nasal resistance when measured with the APD. The effect is equal during exhalation and during inhalation.

Effects of spinal cord lesion level upon thermoregulation during exercise in the heat

PURPOSE

This study examined the effects of the level of spinal cord injury upon the thermoregulatory responses of wheelchair athletes during prolonged wheelchair exercise in warm conditions.

METHODS

Eight tetraplegic (TP), 10 high-level paraplegic (HP), and 10 low-level paraplegic (LP) athletes exercised for 60 min at 60% [OV0312]O(2peak) in a warm environment (31.5 +/- 1.7 degrees C, 42.9 +/- 8.0% relative humidity). Skin temperature and aural temperature were monitored.

RESULTS

Aural temperature increased gradually during the exercise period by 1.1 +/- 0.3 and 1.4 +/- 0.5 degrees C for the HP and LP groups, with a more marked increase observed for the TP group (2.1 +/- 0.5 degrees C; P < 0.05). Upper-arm skin temperature was higher for the TP when compared with the HP and LP between 30 and 60 min (P < 0.05). Back skin temperature was higher for the TP when compared with the HP and LP between 45 and 60 min (P < 0.05). No differences were noted between groups for the thigh or calf skin temperatures. During recovery, skin temperature remained elevated for the TP group when compared with the HP and LP groups (P < 0.05). Heat storage was greatest for the TP athletes at the end of exercise and remained elevated throughout recovery (P < 0.05).

CONCLUSIONS

All athletes completed the exercise task even though the gradual increase in aural temperature observed for the HP and LP groups suggests a degree of thermal imbalance. However, this was much less than observed for TP athletes, who demonstrated a much greater imbalance in temperature regulation. Increasing the exercise or environmental strain may result in the thermoregulatory responses of athletes with a spinal cord injury being compromised.

Temperature gradient across the skin's layers has no influence on local skin vasomotor responses

The normal negative temperature gradient within the skin of the cheek was reversed by simultaneously heating the skin externally with an infrared lamp and cooling it internally, inside the mouth, with ice. Cutaneous blood flow was measured locally under four different conditions: negative and positive gradient of local skin temperature in hypothermia and hyperthermia. There were no significant differences between negative and positive skin temperature gradients. Cutaneous blood flow depended on the core body temperature. These results show that the local skin temperature gradient can not induce vasomotor responses.

Beard vs. forehead, ten years later

Ten years ago (1988), we observed in a sample of 100 men that the area of the glabrous skin above the eyebrows was proportional to the area of the hairy skin on the cheeks, lips, and chin. Ten to 11 years later, we measured again 39 of the former subjects to check longitudinally whether the relationship would still be valid. In the group of 39 subjects, the correlation was again significant and the regression was practically the same as that obtained in the same sample 10 years earlier. This would tend to show that ontogeny follows phylogeny. This results is understood as indirect evidence in favor of selective brain cooling in humans. Am. J. Hum. Biol. 12:460-464, 2000. Copyright 2000 Wiley-Liss, Inc.

Selective brain cooling in hyperthermia: the mechanisms and medical implications

We hypothesize that selective brain cooling (SBC) can occur in hyperthermic humans despite the fact that humans have no carotid rete, a vascular structure that facilitates countercurrent heat exchange and that is located at the base of the skull in some mammals. We postulate that an increase in emissary and angular ocular venous flows contributes to SBC. The efficiency of SBC is increased by evaporation of sweat on the head and by ventilation through the nose. A body position that increases the intravenous pressure gradient across the skull increases emissary flows and hence enhances the efficiency of SBC. The validity of using tympanic temperature as an index of brain temperature is also postulated.