Components of aircraft life support systems interact with each other and the user.

The life support system in a tactical aircraft provides necessary supplemental oxygen to the aircrew. However, interactions among its various components may generate unexpected breathing loads. We focus here on the interactions between a regulator and breathing mask commonly used together in the U.

Exercise carbon dioxide (CO2) retention with inhaled CO2 and breathing resistance.

Combined effects on respiratory minute ventilation (VE)--and thus, on end-tidal carbon dioxide partial pressure (P(ET)CO2)--of breathing resistance and elevated inspired carbon dioxide (CO2) had not been determined during heavy exercise. In this Institutional Review Board-approved, dry, sea-level study, 12 subjects in each of three phases exercised to exhaustion at 85% peak oxygen uptake while V(E) and P(ET)CO2 were measured. Participants inhaled 0%, 1%, 2% or 3% CO2 in air, or 0% or 2% CO2 in oxygen, with or without breathing resistance, mimicking the U.

Physiologically acceptable resistance of an air purifying respirator.

Physiologically acceptable limits of inspiratory impediment for air purifying respirators (APRs) were sought.Measurements on 30 subjects included pressure in, and flow through, an APR, and respiratory and cardiovascular variables. Exercise with and without APR included ladder climbing, load lift and transfer, incremental running and endurance running, with endurance at 85% peak oxygen uptake.

Effects of respiratory muscle training on respiratory CO2 sensitivity in SCUBA divers.

Typically, ventilation is tightly matched to CO2 production. However, in some cases CO2 is retained (SCUBA diving). One factor behind hypoventilation in divers may be low respiratory CO2 sensitivity.

Respiratory muscle training improves swimming endurance in divers.

Respiratory muscles can fatigue during prolonged and maximal exercise, thus reducing performance. The respiratory system is challenged during underwater exercise due to increased hydrostatic pressure and breathing resistance. The purpose of this study was to determine if two different respiratory muscle training protocols enhance respiratory function and swimming performance in divers.