Invasive mechanical ventilation induces ventilator induced diaphragmatic dysfunction particularly when used for long time and Intercostal muscles as well contribute to the important work of respiratory movement by expanding the thorax , and determining the thickness of them would be a useful parameter in evaluating respiratory muscle activity.

This study will add the impact of mechanical ventilation on the diaphragm and intercostal muscles in preterm infants using ultrasound.

Inclusion Criteria:

1. Preterm infants from 28-36 weeks gestation
2. In need for invasive mechanical ventilation according to work of breathing, oxygen saturation and blood gases .

Exclusion Criteria:

• 1) Significant congenital anomalies including cardiac, abdominal or respiratory.

  2) Congenital anomalies involving the diaphragm. 3) Phrenic nerve paralysis. 4) Congenital muscular dystrophies. 5) Major upper or lower airway anomalies. 6) Storage diseases.

The study will be conducted on neonates admitted to NICU.