Effects of Immersion in Water and Changes in Intrathoracic Blood Volume on Lung Function in Man

Abstract

1. In healthy, normal subjects simultaneous peripheral venous occlusion of all four limbs caused a small but significant increase in vital capacity (VC) and single-breath carbon monoxide transfer factor (DLCO) without significantly changing total lung capacity (TLC), residual volume (RV), pulmonary gas flow or pulmonary compliance. 2. Immersion in water to the neck resulted in a small but significant fall in VC, FEV 1.0/FVC and TLC, and a rise in DLCO, but flow/volume curves and 'closing volume' were unchanged. Peripheral venous occlusion during immersion only significantly increased VC and DLCO; pulmonary compliance and flow/volume curves did not alter significantly. 3. It is concluded that peripheral venous occlusion produces these effects by altering intrathoracic blood volume. Water immersion reduces TLC, mainly from the hydrostatic pressure, and VC is reduced from both the hydrostatic pressure and the increase in intrathoracic blood volume consequent on immersion. The increase in DLCO is due, almost entirely, to the increase in intrathoracic blood volume.

Respiratory and Hemodynamic Adjustment During Head Out Water Immersion

“…The data obtained on resistance to breathing correspond well to the data of Agostini et al (3), who reported an increase of airway resistance of about 60 %, analyzed by the esophageal pressure method. The results are also consistent with findings of increased closing volume during head out water immersion (9,19,20), indicating that airway closure occurs earlier during immersion than under dry conditions. The time course of the airway resistance when the level of submersion increases clearly indicates that compression of the rib cage and the ascent of the diaphragm, due to hydrostatic pressure, contribute mainly to airway narrowing.…”

“…In addition, a decrease of functional residual capacity, often described during immersion, reduces airway caliber and is not compensated for by the shift of the breathing level toward expiration. However, increased intrathoracic blood volume following blood shift reduces compliance of lung tissue and causes instability of small airways (3,9,20). This then corresponds to findings of Muir et al (21), who described an increase of the closing volume after a rapid saline infusion.…”

“…For example, cardiac output has been described to decrease (4), to increase (1, 5), or to remain unchanged (6). Conflicting results are also known with regard to diffusing capacity (5, 7,8,9). The alveolar arterial difference for oxygen (AaDO2) has consistently been found to increase during immersion to the neck (8,10).…”

“…The alveolar arterial difference for oxygen (AaDO2) has consistently been found to increase during immersion to the neck (8,10). However, results on pulmonary partial functions contributing to an increased AaDO2 still conflict (8,9,10) or have not yet been studied, e.g., diffusing capacity and its components. The objectives of the present study were to analyze pulmonary and circulatory function during immersion to the neck.…”

Microgravity and the respiratory system

“…Unlike vital capacity or FRC, both of which are known to change with posture, residual volume is very resistant to change, with upright to supine transitions [15,16] and water immersion [17,18] showing little change. However, somewhat surprisingly, residual volume in microgravity was lower than that standing by 310 mL, an 18% reduction, and lower than that supine by 220 mL [11].…”