Evidence for increased intrathoracic fluid volume in man at high altitude

Abstract

To determine if subclinical pulmonary edema occurs commonly at high altitude, 25 soldiers participated in two consecutive 72-h field exercises, the first at low altitude (200–875 m) and the second at high altitude (3,000–4,300 m). Various aspects of ventilatory function and pulmonary mechanics were measured at 0, 36, and 72 h of each exercise. Based on physical examination and chest radiographs there was no evidence of pulmonary edema at high altitude. There was, however, an immediate and sustained decrease in vital capacity and transthoracic electrical impedance as well as a clockwise rotation of the transpulmonary pressure-volume curve. In contrast, closing capacity and residual volume did not change immediately upon arrival at high altitude but did increase later during the exposure. These observations are consistent with an abrupt increase in thoracic intravascular fluid volume upon arrival at high altitude followed by a more gradual increase in extravascular fluid volume in the peribronchial spaces of dependent lung regions.

The effect of an acute bout of exercise on selected pulmonary function measurements

“…Both of these studies (11,18) are consistent with the increase in RV and TLC reported in studies I, II, and III. The increases in TLC could also be due to increased patency, and possibly an increased number of conducting airways, as speculated by Kagawa and Kerr (12).…”

“…Such a procedure has previously been used by Jaeger et a1. (11). This value was also significantly decreased below the pre-exercise value through 3D-minutes of recovery.…”

“…In a study they performed on 43 dogs and 9 patients, they were able to detect fluid accumulation as small as 50 ml within the intact thorax. In a more recent study, Jaeger et al (11), used TEl to determine if sub-clinical pulmonary edema was a common occurrence among non-acclimatized men following rapid accent to 4300 meters. Upon physical examination no signs of pulmonary edema were present, and no definite radiographic evidence of fluid accumulation was found.…”

No evidence for interstitial lung oedema by extensive pulmonary function testing at 4,559 m

“…Furthermore, seven studies [4][5][6][7][8][9]12] reporting decreased FVC had 4-26 subjects, i.e. had less statistical power than the present study.…”

“…P revious investigations reported reduced forced vital capacity (FVC) [1][2][3][4][5][6][7][8][9][10][11][12] and reduced forced expiratory volume in 1 s (FEV1) [3,7,9,10,12], as well as increased closing volume (CV) [4,12,13], during the first days after ascent to altitudes of 2,800-5,300 m. These findings were interpreted as being consistent with pulmonary interstitial fluid accumulation or subclinical high-altitude pulmonary oedema (HAPE). However, there are several other factors that could also account for or contribute to the observed changes.…”