Warkander D E, Nagasawa G K, Lundgren C E
Center for Research and Education in Special Environments, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, USA.
Undersea Hyperb Med. 2001 Summer;28(2):63-73.
This study was performed to determine if inspiratory breathing resistance causes greater or smaller changes than expiratory resistance. Unacceptable inspiratory resistances were also determined. Five subjects exercised at 60% of their VO2max while immersed in a hyperbaric chamber. The chamber was pressurized to either 147 kPa (1.45 atm abs, 4.5 msw, 15 fsw) or 690 kPa (6.8 atm abs, 57 msw, 190 fsw). Breathing resistance was imposed on the inspiratory or expiratory side and was as high as 0.8-1.2 kPa liter(-1) x s(-1) (8-12 cm H2O x liter(-1) x s(-1)) at a flow of 2-3 liter x s(-1) at 1 atm abs., the other side being unloaded. The subjects reacted to the imposed load by prolonging the phase of breathing that was loaded. Inspiratory breathing resistance caused greater changes than expiratory resistance in end-tidal CO2, dyspnea scores, maximum voluntary ventilation, and respiratory duty cycle. Using previously published criteria for acceptable levels of dyspnea scores and the CO2 levels, we found that an inspiratory resistance inducing a volume-averaged pressure of 1.5 kPa is not acceptable. Similarly, an expiratory resistance should not induce a volume-averaged pressure exceeding 2.0 kPa
本研究旨在确定吸气呼吸阻力引起的变化是否比呼气阻力更大或更小。还确定了不可接受的吸气阻力。五名受试者在沉浸于高压舱的情况下，以其最大摄氧量的60%进行运动。高压舱被加压至147 kPa（绝对压力1.45 atm，水下4.5 m，水下15英尺）或690 kPa（绝对压力6.8 atm，水下57 m，水下190英尺）。在吸气或呼气侧施加呼吸阻力，在绝对压力1 atm下，当流量为2 - 3升/秒时，阻力高达0.8 - 1.2 kPa·升⁻¹·秒⁻¹（8 - 12 cmH₂O·升⁻¹·秒⁻¹），另一侧则无负荷。受试者通过延长有负荷的呼吸阶段来应对施加的负荷。吸气呼吸阻力在呼出末二氧化碳、呼吸困难评分、最大自主通气量和呼吸周期方面引起的变化比呼气阻力更大。使用先前公布的关于可接受的呼吸困难评分水平和二氧化碳水平的标准，我们发现诱导体积平均压力为1.5 kPa的吸气阻力是不可接受的。同样，呼气阻力不应诱导超过2.0 kPa的体积平均压力。
