Role of abdominal muscles activity on duration and severity of hypoxemia episodes in mechanically ventilated preterm infants.
BACKGROUND
Episodes of hypoxemia are often observed in ventilated preterm infants. The factors that determine their duration, severity and the failure of the mechanical breaths to maintain ventilation have not been fully defined.


OBJECTIVE
To determine the relation between activity of the abdominal muscles and the duration and severity of hypoxemia episodes in ventilated preterm infants.


METHODS
Clinically stable ventilated preterm infants weighing between 500 and 1,000 g at birth, who presented with frequent episodes of hypoxemia, were studied. Recordings of arterial oxygen saturation (SpO(2)), tidal volume and abdominal surface electromyography were obtained during 4 h to assess the temporal relationship between activation of abdominal musculature with the onset, duration and severity of hypoxemia episodes.


RESULTS
In 15 infants, GA (mean +/- SD) 25 +/- 1.5 weeks, BW 697 +/- 141 g, age 37 +/- 14 days, synchronized intermittent mandatory ventilation rate 17 +/- 6 breaths/min, peak inspiratory pressure 18 +/- 1.9 cm H(2)O, positive end-expiratory pressure 4.8 +/- 0.6 cm H(2)O, and fraction of inspired oxygen (FiO(2)) 0.4 +/- 0.1 were studied. These infants presented with 7.2 +/- 4.4 episodes of hypoxemia (SpO(2) <88%) per hour. The number of abdominal muscle contractions per episode correlated with the duration and severity of the episodes of hypoxemia. The episode duration increased by 14 +/- 18 s per abdominal muscle contraction. The lowest SpO(2) reached during an episode of hypoxemia decreased by 1.7 +/- 1.4% for every abdominal muscle contraction.


CONCLUSIONS
These data document a relationship between abdominal muscles contraction and the duration and severity of hypoxemia episodes in ventilated preterm infants. These findings can explain the failure of mechanical ventilation to prevent their occurrence or decrease their severity.
Esquer
Cristian
C
Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
Claure
Nelson
N
D'Ugard
Carmen
C
Wada
Yoshiro
Y
Bancalari
Eduardo
E
D000009:Abdominal Muscles / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods; D005865:Gestational Age; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007231:Infant, Newborn; D007234:Infant, Premature; D009119:Muscle Contraction / Q000502:physiology*; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D012121:Respiration, Artificial / Q000379:methods*; D013990:Tidal Volume / Q000502:physiology
D010100:Oxygen