Hemodynamic changes during weaning from nasal continuous positive airway pressure.

BACKGROUND

Nasal continuous positive airway pressure is frequently used to support preterm infants with respiratory distress syndrome. Little is known about the hemodynamic changes that occur, particularly during the weaning phase when lung compliance has improved and most of the airway pressure can be transmitted to the heart and major blood vessels.

METHODS

We conducted a prospective study on preterm infants (gestational age <or=32 weeks) with resolving respiratory distress syndrome, who were receiving nasal continuous positive airway pressure of 5 cm H(2)O and 21% oxygen. While cycling nasal continuous positive airway pressure, we performed 2-dimensional M-mode and pulsed Doppler echocardiography on all infants during nasal continuous positive airway pressure and 1 hour after being off nasal continuous positive airway pressure.

RESULTS

A total of 25 preterm infant were studied. The use of nasal continuous positive airway pressure significantly decreased right ventricular output (320 +/- 22.7 vs 410.5 +/- 44.1 mL/kg per min); right ventricular end diastolic diameter (6 +/- 0.7 vs 6.4 +/- 0.4 mm), left ventricular end diastolic diameter (11.6 +/- 0.9 vs 13.6 +/- 0.7 mm), left ventricular end systolic diameter (7.1 +/- 0.6 vs 8.3 +/- 0.4 mm), left atrial diameter (6.3 +/- 0.5 vs 8 +/- 0.5 mm), aortic root diameter (6.4 +/- 0.3 vs 6.6 +/- 0.4 mm), superior vena cava flow (70.2 +/- 8.5 vs 91.1 +/- 4 mL/kg per minute), and pulmonary maximum velocity (0.6 +/- 0.1 vs 0.7 +/- 0.1 m/seconds). It significantly increased mean inferior vena cava diameter (4.3 +/- 0.5 vs 3.5 +/- 0.6 mm), whereas nasal continuous positive airway pressure did not influence left ventricular output, aortic maximum velocity, fractional shortening, heart rate, or mean arterial blood pressure. Changes associated with nasal continuous positive airway pressure were similar in infants with (n = 8) and without (n = 17) patent ductus arteriosus.

CONCLUSIONS

In infants with resolving respiratory distress syndrome, nasal continuous positive airway pressure can impede systemic and pulmonary venous return, but it does not compromise systemic arterial pressure or heart rate. It is not clear whether the degree of these hemodynamic changes can affect the success of weaning off nasal continuous positive airway pressure.