Table 1

Clinical trials and physiological studies of continuous distending pressures

YearTrialsResults
1971Gregory et al 19 First use of CPAP in neonates showed oxygenation increased by 38% within 12 hours and survival improved.
1973Rhodes and Hall20 Randomised infants to face mask CPAP or control. Mortality was 53% in controls and 27% with CPAP.
1973Kattwinkel et al 21 22 Showed that CPAP significantly reduces the duration of exposure to high levels of oxygen.
1973Herman and Reynolds23 Showed that oxygenation increased as PEEP increased from 0 to 5 cm H2O with no extra improvement at 10 cm H2O.  Arterial PaCO2 increased as the PEEP increased but at 10 cm H2O the PaCO2 was “unacceptably high”.
1976Berman et al 24 Intubated infants recovering from RDS had the lowest oxygenation and lung volume with zero PEEP. They improved when  the infants received a PEEP of 2 cm H2O or were extubated.
1976Speidal et al 25 Nasal CPAP regularised the respiratory pattern and abolished or reduced apnoeic attacks.
1979Alexanderet al 26 Nasal CPAP and continuous negative pressure both improved oxygenation. Nasal CPAP was easier. Both techniques produce  some air leaks.
1981Stewartet al 27 Increases in PEEP improved oxygenation per cm H2O mean airway pressure than increasing peak inspiratory pressure or  changing the I:E ratio. Increasing PEEP increased the PaCO2.
1982Engelkeet al 28 Nasal CPAP post extubation compared with head box oxygen showed that nasal CPAP improved oxygenation, carbon  dioxide levels, pH, chest x-rays and lowered the respiratory rate.
1986Kim et al 29 Endotracheal tube CPAP for six hours reduced extubation success compared with extubation to a head box.
1987Hausdorf et al 30 Increasing PEEP proportionally reduced the left and right ventricular stroke volume and cardiac output and slightly impaired  the systemic and pulmonary blood flows.
1988Trang et al 31 Cardiac index fell at PEEP of 3, 6, 9 cm H2O by 6%, 11% and 19%. The stiffer the lungs the smaller the effect. Despite this,  heart rate and mean blood pressure did not change.
1991Higgins et al 32 In a randomised trial of extubation strategies for babies <1 kg: 75% were successfully extubated when treated with nasal CPAP and only 30% if treated in a head box.
1992Greenough et al 33 Acutely ventilated infants increased oxygenation and carbon dioxide as PEEP levels increased. Chronically ventilated infants  showed the same trends for oxygen but with little effect on PaCO2.
1993Chan et al 34 Compared extubation to head-box oxygen or nasal CPAP at 3 cm H2O and showed no difference in failure rate between the  two.
1994Da Silva et al 35 Increasing PEEP from 2 to 5 cm H2O increased the FRC from 18.4 ml/kg to 22.6 ml/kg (about 20 to 30 ml/kg in healthy  neonates). Increasing PEEP by 1 cm H2O increased the FRC on average by 1.3 ml/kg.
1994Bartholomew et al 36 A 1 cm H2O change in PEEP had twice the effect on tidal volume as a 2 cm H2O change in peak pressure in paralysed
 infants.  Reductions in PEEP are as effective at reducing PaCO2 as increasing the peak inspiratory pressure.
1995Tapia et al 37 Showed no clear effect of extubating babies to nasal CPAP compared with head-box oxygen at 3 to 4 cm H2O.
1995So et al 38 Reintubation occurred in 16% of infants treated with CPAP compared with 52% treated in a head box.
1998Davis et al 39 Different levels of CPAP applied to infants with tracheomalacia increased the lung volume but did not alter the forced  expiratory flow.
1998Ahluwalia et al 40 In a cross over study showed there was no difference in oxygenation, other physiological parameters or comfort score between  single prong nasal CPAP and the Infant Flow Driver.
1998Davis et al 41 This study randomised extubated babies to nasal CPAP or head box and showed that 66% were successfully extubated to  CPAP and 40% to head box. Nasal CPAP after extubation reduces the adverse events without increasing side effects.
1998Robertsonet al 42 Ventilated premature babies were randomised at extubation to nasal CPAP or head box oxygen although the head box group  also received CPAP if criteria were met. There was no difference in successful extubation between the groups. Therefore  CPAP may be used for prophylaxis or rescue treatment at extubation.