Effects of breathing pattern and inspired air conditions on breath condensate volume, pH, nitrite, and protein concentrations

Abstract

Background: The effects of breathing pattern and inspired air conditions on the volume and content of exhaled breath condensate (EBC) were investigated. Methods: Total exhaled water (TEW), EBC volume, pH, nitrite and protein concentrations were measured in three groups of 10 healthy subjects breathing into a condenser at different target minute ventilations (Vm), tidal volumes (Vt), and inspired air conditions. Results: The volumes of both TEW and EBC increased significantly with Vm. For Vm 7.5, 15 and 22.5 l/ min, mean (SD) EBC was 627 (258) ml, 1019 (313) ml, and 1358 (364) ml, respectively (p,0.001) and TEW was 1879 (378) ml, 2986 (496) ml, and 4679 (700) ml, respectively (p,0.001). TEW was significantly higher than EBC, reflecting a condenser efficiency of 40% at a target Vm of 7.5 l/min which reduced to 29% at Vm 22.5 l/min. Lower Vt gave less TEW than higher Vt (26.6 v 30.7 ml/l, mean difference 4.1 (95% CI 2.6 to 5.6), p,0.001) and a smaller EBC volume (4.3 v 7.6 ml/l, mean difference 3.4 (95% CI 2.3 to 4.5), p,0.001). Cooler and drier inspired air yielded less water vapour and less breath condensate than standard conditions (p,0.05). Changes in the breathing pattern had no effect on EBC protein and nitrite concentrations and pH. Conclusion: These results show that condensate volume can be increased by using high Vt and increased Vm without compromising the dilution of the sample.

Exhaled breath condensate biomarkers in COPD

“…The volume of EBC obtained increases with higher minute ventilation and/or tidal volume [12,[16][17][18]. This may simply reflect the increase in volume of air exhaled or be due to greater turbulence generating increased aerosolisation of ALF.…”

“…EBC hydrogen peroxide (H 2 O 2 ) concentration is inversely proportional to the expiratory flow rate during collection in asthma patients and healthy subjects using resistors to generate flow rates of 140, 69 and 48 mL?s -1 [17]. In contrast, the pattern of breathing has no significant effect on concentrations of leukotriene (LT)B 4 , LTE 4 , prostaglandin (PG)E 2 [16], aldehydes [9], pH [12,18], NO 3 -or total protein [18]. The effect of breathing pattern is therefore dependent on the specific mediator examined.…”

The effect of gas standardisation on exhaled breath condensate pH: Fig. 1—

“…It has been argued that CO 2 is unwelcome ''noise'' in the sample and, although the completeness of CO 2 removal has not been confirmed, gas-standardised EBC pH is stable and provides reproducible measurements [3,4]. However, some authors regard CO 2 as a relevant component of EBC and have measured pH without gas standardisation [5,6]. These variations in methodology make comparison between studies difficult.…”

Safety and feasibility of exhaled breath condensate collection in ventilated infants and children

“…The effect of ventilation on droplet formation or on the evaporation of water is not well understood. Some, but not all, studies have reported little effect of minute volume ventilation on the concentration of exhaled makers [22,23]. SCHLEISS et al [24] found a falling hydrogen peroxide concentration with increasing expiratory flow in healthy volunteers and asthmatics.…”

“…MOLONEY et al [16] described its use in 26 ventilated adults without observing adverse effects. To the present authors' knowledge, there are no published data regarding its safety in ventilated paediatric subjects, and little is also known about the influence of ventilatory parameters on the amount and composition of collected condensate [22][23][24].…”