Mask humidity during CPAP: influence of ambient temperature, heated humidification and heated tubing

Figures & data

Table 1 Subject characteristics

Characteristics	Overall (n=18)	Summer (n=11)	Winter (n=7)
Age, years	54.3±8.5	54.5±7.9	54.0±7.8
Height, cm	179.9±8.4	179.4±5.2	180.9±5.1
Weight, kg	102.7±20.6	98.9±17.0	108.6±15.1
BMI, kg/^2	31.6±5.4	30.7±4.6	33.1±4.5
ESS score	9.8±5.9	8.9±5.8	11.3±5.0
AHI baseline,/h	31.9±22.0	26.6±21.3	41.5±21.0
CPAP, cmH2O	9.0±2.4	8.6±2.2	9.6±2.8

Notes: Values are mean ± standard deviation.

Abbreviations: BMI, body mass index; ESS, Epworth Sleepiness Scale; AHI, apnea-hypopnea index; CPAP, continuous positive airway pressure.

Table 2 Relative humidity (rH), temperature (T) and absolute humidity (aH) during continuous positive airway pressure (CPAP) therapy under different humidification conditions, with and without additional mask leakage, at two pressure levels (8 and 12 cmH₂O), in summer and winter

Setting	Summer				Winter
	8 cmH2O		12 cmH2O		8 cmH2O		12 cmH2O
	No mask leak	With mask leak	No mask leak	With mask leak	No mask leak	With mask leak	No mask leak	With mask leak
No humidification
rH, %	74.2±6.6	72.0±6.9	70.1±7.9	68.5±7.0	70.7±5.7	68.3± 5.9	68.6±5.2	67.0±4.2*
T, °C	26.5±0.8	26.5±0.8	26.2±0.7	26.2±0.6	21.5± 0.9*	21.7± 0.9*	21.2±1.1*	21.2±1.1*
aH, mg/L	18.4±1.7	18.0±1.9	17.2±1.9	16.8±1.7	13.2±1.5*	12.9±1.5*	12.7±1.6*	12.3±0.9*
Controlled heated humidification
rH, %	93.1±3.6	90.0±5.2	88.6±5.7	85.8±6.0	93.4±3.1	91.7±3.9	93.3±3.4	92.2±2.3
T, °C	26.9±0.7	26.8±0.7	26.3±0.8	26.1±0.7	23.3±0.8*	23.0±1.0*	22.5±1.1*	22.2±1.2*
aH, mg/L	23.7±1.4	22.8±1.4	21.8±1.8	20.9±1.6	19.2±0.9*	18.6±1.1*	18.4±1.3*	17.9±1.4*
Controlled heated humidification with heated tube climate line
rH, %	82.8±8.2	81.3±6.7	82.5±5.9	81.1±5.3	77.7±4.2	75.2±3.1	77.3±2.6	77.0±3.2
T, °C	28.1±0.8	28.2±0.8	27.9±0.6	27.8±0.7	26.4±1.0*	26.2±1.0*	25.9±0.6*	25.7±0.5*
aH, mg/L	22.6±2.5	22.3±1.9	22.3±1.9	21.8±1.6	19.2±1.4*	18.4±1.2*	18.6±0.9*	18.3±1.1*

Notes: Data are presented as mean ± standard deviation.

* p < 0.01 vs. summer.

Figure 1 Relationship between temperature and humidity.

Notes: Relative humidity (rH; %) and absolute humidity (aH, mg/L) dependent on temperature under winter and summer conditions during continuous positive airway pressure (CPAP) therapy with no humidification (nH; blue circles), standard heated humidification (HH; green circles) and heated tube humidification (CL; red circles). Data are combined for CPAP at 8 and 12 cmH₂O, with and without leakage
Abbreviation: CL, climate line.

Figure 2 Overall subjective humidity and temperature evaluation during the applied pressure and leakage conditions.

Abbreviations: nH, no humidity; HH, heated humidity; CL, climate line (0 = uncomfortable, 5 = comfortable).