The respiratory response to inspiratory resistive loading during rapid eye movement sleep in humans

We investigated the respiratory response to an added inspiratory resistive load (IRL) during rapid eye movement (REM) sleep in humans and compared this with those in non-REM (NREM) sleep and wakefulness. Results were obtained from 7 out of 15 healthy subjects (n = 7; 32 +/- 9 years, mean +/- s.d.). Linearised IRLs (4 and 12 cmH(2)O l(-1) s(-1)) were applied for five breaths during NREM sleep (4-10 trials per subject; total 101), REM sleep (2-5 trials; total 46) and wakefulness (2-3 trials; total 40). Respiratory variables were compared, between unloaded breathing (UL: mean of 5 breaths preceding IRL) and the 1st (B1) and 5th (B5) loaded breaths in each state. During wakefulness, 12 cmH(2)O l(-1) s(-1) IRL produced an immediate respiratory compensation with prolongation of inspiratory time (T(I); UL: 2.0 +/- 0.6; B1: 2.6 +/- 0.7 s) and an increase in tidal volume (V(T); UL: 0.49 +/- 0.12; B1: 0.52 +/- 0.12 l). During REM sleep, T(I) was prolonged (UL: 2.0 +/- 0.3; B1: 2.2 +/- 0.5 s), although V(T) fell (UL: 0.27 +/- 0.15; B1: 0.22 +/- 0.10 l). For both wakefulness and REM sleep the TI response was significantly greater than seen in NREM sleep (UL: 1.9 +/- 0.3; B1: 1.9 +/- 0.3 s.). For VT, only the wakefulness response was significantly different from NREM sleep (UL: 0.31 +/- 0.14; B1: 0.21 +/- 0.10 l). The B5 responses were not significantly different between states for any of the variables. REM sleep is associated with partial respiratory load compensation suggesting that exacerbation of sleep disordered breathing in REM (compared to NREM) sleep is unlikely to be secondary to an inability to overcome increases in upper airway resistance.