Influence of sleep on lung volume in asthmatic patients and normal subjects

Abstract

To assess the effect of sleep on functional residual capacity (FRC) in normal subjects and asthmatic patients, 10 adult subjects (5 asthmatic patients with nocturnal worsening, 5 normal controls) were monitored overnight in a horizontal volume-displacement body plethysmograph. With the use of a single inspiratory occlusion technique, we determined that when supine and awake, asthmatic patients were hyperinflated relative to normal controls (FRC = 3.46 +/- 0.18 and 2.95 +/- 0.13 liters, respectively; P less than 0.05). During sleep FRC decreased in both groups, but the decrease was significantly greater in asthmatic patients such that during rapid-eye-movement (REM) sleep FRC was equivalent between the asthmatic and normal groups (FRC = 2.46 +/- 0.23 and 2.45 +/- 0.09 liters, respectively). Specific pulmonary conductance decreased progressively and significantly in the asthmatic patients during the night, falling from 0.047 +/- 0.007 to 0.018 +/- 0.002 cmH2O-1.s-1 (P less than 0.01). There was a significant linear relationship through the night between FRC and pulmonary conductance in only two of the five asthmatic patients (r = 0.55 and 0.65, respectively). We conclude that 1) FRC falls during sleep in both normal subjects and asthmatic patients, 2) the hyperinflation observed in awake asthmatic patients is diminished during non-REM sleep and eliminated during REM sleep, and 3) sleep-associated reductions in FRC may contribute to but do not account for all the nocturnal increase in airflow resistance observed in asthmatic patients with nocturnal worsening.

Effects of Inhaled Fluticasone on Upper Airway during Sleep and Wakefulness in Asthma: A Pilot Study

“…38 Patients with nocturnal asthma, who start the night hyperinflated relative to controls, experience an augmented decline in functional residual capacity (FRC) to levels comparable to those of control subjects during REM sleep. 39 It is thus possible that the improved lung mechanics with FP also attenuated the degree of decline in FRC during sleep; the resultant increase in pharyngeal UAW tethering via tracheal tug could have rendered it stiffer, 40 thereby also improving the Pcrit. Further studies accounting for nasal resistance and sleep related changes in lower airway mechanics will be needed; (2) an unchanged Pcrit could result from above changes being offset by deleterious effects, discussed next; (3) a deterioration in Pcrit could result from a predominant increase in the surrounding tissue pressure, including fat accumulation, and from changes in the properties of UAW muscle, as suggested by our findings on the tongue discussed below.…”

Pulmonary hyperinflation a clinical overview

“…BALLARD et al [48] showed that, while the FRC of patients with mild asthma when awake was greater than control subjects, during sleep the fall in FRC exceeded that in normals, so that during rapid eye movement (REM) sleep FRC was similar in the two groups ( fig. 5a).…”

Effect of increased lung volume on sleep disordered breathing in patients with sleep apnoea

“…[2][3][4][5] During sleep, in normal subjects, upper airway resistance increases and functional residual capacity decreases. [6][7][8] This sleep induced decrease in lung volume is believed to result in increased upper airway collapsibility and to contribute to inspiratory flow limitation, although the exact mechanisms have not been delineated. Animal data using mongrel dogs have suggested that thoracic inflation increases upper airway pharyngeal size and stiffness through caudal traction on the trachea independently of upper airway muscle activity.…”