Fluid distribution and tissue thickness changes in 29 men during 1 week at moderate altitude (2,315 m)

Positive expiratory pressure improves arterial and cerebral oxygenation in acute normobaric and hypobaric hypoxia

Positive expiratory pressure (PEP) has been shown to limit hypoxia-induced reduction in arterial oxygen saturation, but its effectiveness on systemic and cerebral adaptations, depending on the type of hypoxic exposure [normobaric (NH) versus hypobaric (HH)], remains unknown. Thirteen healthy volunteers completed three randomized sessions consisting of 24-h exposure to either normobaric normoxia (NN), NH (inspiratory oxygen fraction, FiO2 = 13.6%; barometric pressure, BP = 716 mmHg; inspired oxygen partial pressure, PiO2 = 90.9 ± 1.0 mmHg), or HH (3,450 m, FiO2 = 20.9%, BP = 482 mmHg, PiO2 = 91.0 ± 0.6 mmHg). After the 6th and the 22nd hours, participants breathed quietly through a facemask with a 10-cmH₂O PEP for 2 × 5 min interspaced with 5 min of free breathing. Arterial (SpO2, pulse oximetry), quadriceps, and cerebral (near-infrared spectroscopy) oxygenation, middle cerebral artery blood velocity (MCAv; transcranial Doppler), ventilation, and cardiovascular responses were recorded continuously. SpO2without PEP was significantly lower in HH (87 ± 4% on average for both time points, P < 0.001) compared with NH (91 ± 3%) and NN (97 ± 1%). PEP breathing did not change SpO2 in NN but increased it similarly in NH and HH (+4.3 ± 2.5 and +4.7 ± 4.1% after 6h; +3.5 ± 2.2 and +4.1 ± 2.9% after 22h, both P < 0.001). Although MCAv was reduced by PEP (in all sessions and at all time points, -6.0 ± 4.2 cm/s on average, P < 0.001), the cerebral oxygenation was significantly improved (P < 0.05) with PEP in both NH and HH, with no difference between conditions. These data indicate that PEP could be an attractive nonpharmacological means to improve arterial and cerebral oxygenation under both normobaric and hypobaric mild hypoxic conditions in healthy participants.

The use of skeletal muscle near infrared spectroscopy and a vascular occlusion test at high altitude

Microcirculatory function, central to tissue regulation of oxygen flux, may be altered by the chronic hypoxemia experienced at high altitude. We hypothesized that at high altitude, adaptations within skeletal muscle would result in reduced oxygen consumption and reduced microcirculatory responsiveness, detectable by near infrared spectroscopy (NIRS) during a vascular occlusion test (VOT). The VOT comprised 3 min of noninvasive arterial occlusion; thenar eminence tissue oxygenation (Sto2) was measured by NIRS during the VOT at sea level, 4900 m and 5600 m (after 7 and 17 days at altitude, respectively) in 12 healthy volunteers. Data were derived from Sto2 time-curves using specifically designed computer software. Mean (±SD) resting Sto2 was reduced at 4900 m and 5600 m (69.3 (± 8.2)% (p=0.001) and 64.2 (± 6.1)% (p<0.001) respectively) when compared to sea level (84.4 (± 6.0)%. The rate of Sto2 recovery after vascular occlusion (Sto2 upslope) was significantly reduced at 4900 m (2.4 (± 0.4)%/sec) and 5600 m (2.4 (± 0.8)%/sec) compared to sea level (3.7 (± 1.3)%/sec) (p=0.021 and p=0.032, respectively). There was no change from sea level in the rate of desaturation during occlusion (Sto2 downslope) at either altitude. The findings suggest that in resting skeletal muscle of acclimatizing healthy volunteers at high altitude, microvascular reactivity is reduced (Sto2 upslope after a short period of ischemia) but that oxygen consumption remains unchanged (Sto2 downslope).

Leg edema formation and venous blood flow velocity during a simulated long-haul flight

INTRODUCTION

Long-distance traveling in a sitting position may be associated with an increased incidence for venous thromboembolism. As major contributing factors immobility and compression of leg veins are discussed. At present no studies have been performed measuring the time course of lower limb blood flow, leg volume and leg tissue thickness during a long-haul flight.

MATERIALS AND METHODS

We measured limb volumes (plethysmographic method), lower leg tissue thickness and lower limb venous hemodynamics before, during and after 10 h sitting in modern aircraft chairs under normobaric hypoxia in healthy volunteers (n=12).

RESULTS

Lower leg volume was already significantly increased after 4 h sitting (+109 ml) reaching its maximum after 10 h (+145 ml). These changes were accompanied by an increased body weight, total body water, extracellular water and tissue thickness of the tibia. No significant changes were measured for leg vessel cross-section diameters and maximal flow velocities in superficial femoral veins. After 10 h sitting core temperature, overall surface temperature and skin temperatures in front of the tibia were significantly increased. All parameters returned to baseline one day after sitting.

CONCLUSIONS

Prolonged sitting in modern aircraft seats is associated with a remarkable fluid accumulation in the lower legs which mainly occurred during the first hours. These fluid shifts were independent of lower limb venous hemodynamics and vessel cross-sectional diameters.

Forehead donor site full-thickness skin graft

BACKGROUND

Full-thickness skin grafts (FTSGs) are useful for reconstructing nasal defects. Traditional reported donor sites include the preauricular, postauricular, supraclavicular, clavicular, conchal bowl, melolabial fold, and upper eyelid skin. Selection of the "best" donor site is based on the "best" tissue match and ability to camouflage the donor scar.

OBJECTIVE

The purpose was to report our experience with FTSGs harvested from the forehead for reconstruction of nasal defects following Mohs' surgery.

METHODS

A retrospective query of the Mohs' surgery database was performed to identify nasal defects repaired with a FTSG harvested from the forehead skin. The research record contained the patient age and gender, defect size, and cosmetic and functional outcomes interpreted by the patient and surgeon.

RESULTS

FTSGs from forehead skin were used to repair the nasal defects in three patients. The functional and cosmetic outcome of all three cases was deemed excellent by the patient and surgeon. Donor site scars were well concealed within preexisting rhytids.

CONCLUSION

FTSGs harvested from the forehead, although limited in practical utility, may offer an optimal FTSG match for limited select defects while also providing an easily camouflaged donor site scar within a forehead rhytid.

Formation of edema and fluid shifts during a long-haul flight

BACKGROUND

More than 1.5 billion passengers travel by aircraft every year. Leg edema, as a sign of venous stasis, is a well-known problem among passengers during and after long-haul flights. Until now, no studies have been done on the development of leg edema and fluid shifts under real flight conditions. The aim of our study was to evaluate edema formation in the leg and to investigate possible fluid shifts to the interstitial space under real flight conditions.

METHODS

Twenty participants, 10 without risk and 10 with moderate risk for venous thrombosis, were selected. They flew from Vienna to Washington, flight time 9 h, and returned 2 days later. Investigations were done 48 h before the flight, between the fifth and eighth flight hour on board to Washington and back to Vienna, immediately after arrival in Vienna, and 1 and 3 days after arrival. Plethysmographic measurements were carried out using an optoelectronic scanner system (Perometer). Thickness of the skin was measured at the forehead and in front of the tibia.

RESULTS

There were no differences in all measurements between both groups. The volume of the leg increased from 8242 +/- 1420 mL to 8496 +/- 1474 mL after the flight (p <.001). Volume accumulation was distributed to the lower leg as well as to the thigh. Skin thickness in front of the tibia increased significantly during the flight (p <.05), and remained elevated 1 day after arrival.

CONCLUSION

We have demonstrated that long-haul flights induce significant fluid accumulation in the lower extremity, involving the lower leg and thigh. This increase in tissue thickness was maintained for some days after the flights.

Differential effects of short-term prednisolone treatment on peripheral and abdominal subcutaneous thickness in children assessed by ultrasound

Long-term glucocorticoid excess decreases peripheral and increases abdominal subcutaneous thickness. Short-term prednisolone treatment is used in the treatment of many acute and chronic conditions in children. The aim of the present study was to elucidate if changes in thickness of cutis, subcutis, or dermal water content may be induced by short-term prednisolone treatment in children. Twenty children with asthma aged 7.7-13.8 years were included in a double-blind, randomized, placebo-controlled crossover trial. Active treatment was 5mg prednisolone daily. Treatment, run-in, and wash-out periods were 1 week. On days 1 and 7 of each treatment period, 20 MHz ultrasound scanning of the skin was performed on the thigh, forearm, and abdomen. Prednisolone treatment was associated with decreases in the total thickness of the cutis and subcutis in the thigh (0.28 mm) and forearm (0.15 mm), and an increase in the abdomen (0.23 mm). During placebo treatment the thickness was increased in the thigh (0.07 mm) and abdomen (0.05 mm), and reduced in the forearm (0.03 mm). The differences between prednisolone and placebo treatment were statistically significant in the thigh (P=0.04). The increase in thickness in the abdomen during prednisolone treatment was statistically significantly different from the reductions in the thigh (P=0.03) and forearm (P=0.05). There were no statistically significant differences in the dermal thickness or water content during prednisolone treatment compared to placebo.Short-term treatment with 5mg prednisolone daily may cause differential effects in peripheral and abdominal subcutaneous thickness in children.

Influence of body water distribution on skin thickness: measurements using high-frequency ultrasound

BACKGROUND

Although it is known that the skin acts as a water reservoir and participates in the fluid content of the whole body, no method has been established to quantify the fluid shifts in superficial tissue.

OBJECTIVES

The aim of this study was to investigate changes in dermal and subcutis thickness and echodensity at the forehead and lower leg by high-frequency (20 MHz) ultrasound under various physiological conditions influencing water balance.

METHODS

These parameters were measured in the skin of 20 healthy male volunteers at baseline and successively at 30 min after lying down, in a head-down position, after physical activity and after infusion of 10 mL kg-1 body weight of Ringer's solution.

RESULTS

Dermal thickness at the forehead showed a significant increase from baseline to a horizontal position and a further increase in the head-down position. Physical activity did not lead to further changes, whereas after fluid infusion the dermal thickness also increased markedly. The echodensity showed inverse changes, with decreasing values. The thickness of the subcutis increased slightly from baseline to a lying position and decreased in the head-down position and after fluid infusion. At the lower leg, skin thickness decreased slightly in the head-down position with elevated legs, and increased after fluid infusion.

CONCLUSIONS

Our results show that slight changes in the water distribution of the body influence the thickness and the echodensity of the dermis. Changes are more pronounced at the forehead than on the lower legs. Further, the fluid storage takes place mainly in the dermis and not in the subcutis. High-frequency ultrasound is able to quantify these effects and is a sensitive method for measuring fluid intake and balance during anaesthesia and therapy.

Perioperative tissue thickness measurement by a new miniature ultrasound device

INTRODUCTION

A recently developed mini ultrasound device for measurement of peripheral tissue thickness is now available for use in clinical practice. Whether this device allows a better guidance of perioperative fluid therapy has to be investigated. Therefore, it is necessary to get basic data on the parameter tissue thickness in otherwise healthy patients during surgery. The aim of the present study was to evaluate differences in tissue thickness change between patients in supine and head down position with a novel handheld ultrasound device during the perioperative course of healthy surgical patients under a standardized fluid regimen.

METHODS

After obtaining ethics committee approval and informed consent we studied 19 ASA 1-2 female patients undergoing gynecological procedures in supine (SUP, n = 11) or in 30 degrees head down position (HD, n = 8) in general anesthesia. Preoperative NPO status was comparable in both groups. Lactated Ringer's solution (LR) was continuously infused at a rate of 8 ml/kg b.w./h over 90 min and tissue thickness (TT) was determined by ultrasound before induction (t0) and in 30 min intervals (t30, t60, t90) at the forehead. Simultaneously plasma viscosity (PV) was evaluated.

RESULTS

Group SUP presented at t0 a forehead TT of 5.3 mm (SD +/- 0.5), at t30 TT was unchanged. At t60 mean TT increased significantly to 5.6 mm, (+/- 0.6). At t90 mean TT remained stable at 5.7 mm (+/- 0.5). Group HD presented at t0 a mean TT of 4.6 mm (+/- 0.7), at t30 mean TT was 4.9 mm (+/- 0.7) and at t60 mean TT of the forehead skin was measured as 5.3 mm (+/- 0.6). Significance to t0 was reached at t90 with a mean TT of 5.4 mm (+/- 0.7). Group HD showed a steeper increase and a parallel stabilization phase at the end. Differences between t0 and t90 have been significant. Mean PV in the SUP group at t0 (1.361 mPa*s, SD: +/- 0.045) decreased under the infusion therapy to 1.276 mPa*s (+/- 0.04) at t90. Mean PV in the HD group was determined 1.351 mPa*s (+/- 0.06) at t0 and declined to 1.274 mPa*s (+/- 0.03) at t90.

CONCLUSIONS

The findings suggest that fluid replacement after an NPO period and the expected changes of forehead TT due to positioning of the patient are detectable by this new ultrasound device.