Background - Methods - Results - Characteristics of Included Studies - References - Data Tables & Graphs
No new trials were identified in the search dated September 2002, and as a result no substantive changes were made in the review.
A baby born too early (before 34 weeks) often has immature lungs. This is a major cause of breathing failure and death. Mechanical ventilation (machine assisted breathing) keeps the baby breathing and reduces the risk of lung injury and disease. Endotracheal suctioning (removing unwanted fluid through the windpipe) is a routine part of mechanical ventilation, but can have serious complications of pneumothorax (air in the lung cavity) and bradycardia (slow heart rate). Giving oxygen just before suctioning (preoxygenation) may minimise the risk of these complications. The review of trials did not find enough evidence on the effects of preoxygenation. More research is needed.
However there are a number of complications associated with this procedure which have been well documented (Downs 1978; Vaughan 1978; Simbruner 1981; Hill 1982; Perlman 1983, Alpan 1984; Drew 1986; Prendiville 1986; Macpherson 1988; Mehrabani 1991; Shorten 1991), and include hypoxemia, bradycardia, tachycardia, atelectasis, pneumonia, fluctuations in blood pressure and intracranial pressure, localised trauma to the airway, sepsis and tube dislodgement.
Protocols for endotracheal care vary widely between institutions and are not, in general, based on sound evidence. Practices vary in relation to the use of normal saline instillation, chest wall vibrations and percussion, adaptors to enable closed methods of suction, increasing of ventilatory pressures and rate, manual ventilation, number of operators, suctioning frequency, and preoxygenation (Turner 1983; Tolles 1990).
Preoxygenation is a technique of increasing inspired oxygen immediately prior to the suction procedure to increase arterial oxygen saturation. It has been suggested that preoxygenation may minimise the hypoxemia and other adverse effects associated with endotracheal suctioning (Young 1984; Cheng 1989). However, this intervention may cause hyperoxia which is associated with oxygen free radical damage and there is emerging data to suggest that oxygen free radical damage is associated with major morbidity (periventricular leukomalacia, retinopathy of prematurity, chronic lung disease) with the potential for major long term sequelae (Tolles 1990; Taylor 1999; Inder 2000).
Sub-group analyses are planned to determine whether the results differ by:
Population (newborn infants) :
• by gestational age <30 weeks, <34 weeks and <37 weeks; and
• by disease, infants with chronic lung disease compared to those without.
Intervention (different techniques of endotracheal suctioning):
• with or without disconnection from the ventilator;
• increased mechanical ventilation; and
• use of manual ventilation and chest wall vibrations or percussion.
Secondary outcomes:
• Chronic lung disease [infant receiving any respiratory support (supplemental
oxygen or any form of assisted ventilation) for a chronic pulmonary disorder
i) on the day they reached 36 weeks' post menstrual age; and ii) at 28
days postnatal age].
• Hypoxemia ( TcPO2 <50 mmHg or SaO2 <90%)
• Hyperoxemia (TcPO2 >95 mmHg or Sao2 >98%)
• Blood pressure change (percentage change from the baseline to during
suction)
• Bradycardia (decrease in heart rate to < 30% of baseline, or <100
beats per minute)
Methods used for assessing data quality:
Four major sources of potential bias and methods of avoidance of these
biases were considered when assessing trial quality; 1) Selection bias
- blinding of randomization; 2) Performance bias - blinding of intervention;
3) Attrition bias - complete follow-up; 4) Detection bias - blinding of
outcome assessment. The Cochrane Neonatal Group bases its quality assessments
on systematic assessment of the opportunity for each of these biases to
arise. Thus, the reviewers judged from the report of the trial whether
each of the criteria (methods of avoidance) was met. Each criterion was
given a rating of either A if Yes (Adequate), B if Can't Tell (Unclear),
or C if No (Inadequate). The quality assessment rating included in the
Table of Included Studies refers to blinding of randomization alone.
The methodological quality of each trial was reviewed by each author who then compared and resolved differences. Additional information was sought for all identified potentially eligible studies on randomization method. However, at the time of the review no correspondence was received.
Methods used to collect data from included studies:
Each author independently extracted data, then compared and resolved
differences.
Methods used to analyze the data:
Relative risk (RR) was computed for categorical data and Mean difference
(MD) for data measured on a continuous scale, with 95% confidence intervals
(CI) presented for all reported outcomes.
The included study utilised a cross-over design and involved 21 infants. Participants were preterm infants with gestational age 31.4 (± 2.5) weeks, birthweight 1586 (± 682) grams and postnatal age at enrolment 4 (± 4.5) days [(Mean (SD)]. All infants were mechanically ventilated for respiratory distress with FiO2 > 0.30.
In this study, two suctioning procedures were compared. Procedure A included the following sequence of events: chest vibration using a hand held vibrator for two minutes, instillation of normal saline, reconnection to ventilator for 30 seconds, endotracheal tube suctioning with infant's head to one side, returned to ventilator for 30 seconds, second endotracheal suctioning with head on the opposite side, and then returned to ventilator. Procedure B included the same sequence of events as described in procedure A with the addition of preoxygenation which involved an increase in FiO2 until TcPO2 reached between 90 -100 mmHg and stabilised for two minutes. Following suction the FiO2 was gradually reduced to base line setting. Each infant was studied for one suction in each of the two procedures.
The trial measured effects of preoxygenation prior to suctioning on hypoxemia and bradycardia. Transcutaneous oxygen (TcPO2) values were reported at ten time points over a suctioning procedure. In this review, data is presented for three of these measurement points, chosen because of clinical relevance. These points are: 1) end of first endotracheal suction 2) end of second endotracheal suction and 3) at 120 seconds from the end of second suction.
The number of infants with hypoxemia (defined as TcPO2 <40 mmHg) and mean TcPO2 were measured at these points. Other outcomes include TcPO2 recovery (time taken for TcPO2 to return to baseline values) and the numbers of infants experiencing bradycardia (heart rate < 100 beats per minute during the suctioning procedure).
For further details see characteristics of included studies.
Oxygenation:
Preoxygenation prior to suctioning resulted in a statistically significant
reduction in the number of infants with hypoxemia (TcPO2 <40 mmHg) at
the end of the first suction (RR 0.18, 95% CI 0.05, 0.69) and at the end
of the second suction (RR 0.23, 95% CI 0.08, 0.66) and also at 120 seconds
post second suction (RR 0.10, 95% CI 0.01, 0.69).
The mean TcPO2 was statistically significantly higher in the preoxygenation group at the end of first suction (MD 25.00 mmHg, 95%CI 14.20, 35.80), second suction (MD 24.80, 95% CI 14.80, 34.80) and at 120 seconds after the second suction (MD 29.10, 95% CI 14.96, 43.24). Episodes of hyperoxia were not reported.
Recovery time (time taken to return to baseline oxygenation status) was shorter than in the group not receiving preoxygenation (MD -2.12 minutes, 95% CI -3.82, -0.42).
Bradycardia:
No episodes of bradycardia were experienced by infants during the suction
procedure in either of the study groups.
Due to insufficient data, this review was unable to assess the effects of preoxygenation on other important outcomes (retinopathy of prematurity, intraventricular haemorrhage, chronic lung disease, hyperoxia, blood pressure) or on specified sub-groups (gestational age groups, acute or chronic neonatal respiratory failure, use of different suctioning techniques)
There have been many changes in clinical care since the trial included in this review was undertaken. Many of these changes may render the results of this review redundant and difficult to generalize to today's population of ventilated infants. Changes in neonatal care over this time include the use of humidification, exogenous surfactant, physiotherapy, new ventilation modes and a move towards individualised rather than routine care procedures including endotracheal suctioning.
The use of systems which enable delivery of some ventilatory support during suction (usually by an adapter allowing suctioning without disconnection from the ventilator) are now widely available for use in most countries. In this review, subgroup analysis of disconnection from the ventilator could not be undertaken due to insufficient data. The effects of tracheal suctioning without disconnection in intubated ventilated neonates are addressed as the primary objective in another Cochrane Neonatal Review (Woodgate 2002). The effects of other techniques used with preoxygenation for endotracheal suctioning were also not able to be assessed in this review. These techniques include the use of saline instillation, one or two operators, use of manual ventilation, and use of chest wall vibration or percussion.
This review demonstrates benefit in terms of hypoxemia at the time of endotracheal suctioning with preoxygenation. Hypoxemia and its relationship with other alterations in systemic and cerebral hemodynamic changes during endotracheal suctioning may place the preterm infant at risk of intraventricular hemorrhage and possible long term sequelae. The potentially serious side effects of hyperoxemia which may be associated with the technique of preoxygenation is of concern and could not be addressed in this review. The cross-over design of this study precludes the meaningful exploration of long-term outcomes. As the population of infants included in this review may differ substantially from today's intensive care nursery populations, the generalisability of these findings is somewhat limited. The decision whether or not to use preoxygenation for tracheal suctioning in preterm ventilated infants cannot be adequately answered by this review.
| Study | Methods | Participants | Interventions | Outcomes | Notes | Allocation concealment |
| Walsh 1987 | Concealment at randomization- can't tell; Blinding of intervention- no; Completeness of followup-no; Blinding of outcome assessment - can't tell. | 21 preterm infants born at 27 to 35 weeks gestation receiving tracheal intubation and mechanical ventilation for respiratory distress with Fi02 >0.3. | Experimental(B).
FiO2 increased until TcPO2 was between 90-100 mmHg. Infant left to stabilise for two minutes. Chest vibration, instillation of normal saline, suctioning with head to the left, reconnection of ETT for 30 seconds, second suction with head to the right, returned to ventilator. Control(A). As in Experimental group but without preoxygenation. |
Hypoxemia:
Mean TcPO2 and hypoxaemia (TcPO2<40 mmHg) at ten different time points during the suctioning procedure and TcPO2 recovery: time (in minutes) to return to baseline. Bradycardia (HR < 100bpm). |
Pre-trial power calculations-not stated.
Cross-over study design used. 5 post randomization exclusions. |
B |
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Graff 1987 {published data only}
Graff M, France J, Hiatt M, Hegyi T. Prevention of hypoxia and hyperoxia during endotracheal suctioning. Crit Care Med 1987;15:1133-1135.
* indicates the primary reference for the study
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Vicki J Flenady
Centre for Clinical Studies-Women's and Children's Health
Mater Hospital
South Brisbane
Queensland AUSTRALIA
4101
Telephone 1: +61 7 3840 1591
Facsimile: +61 7 3840 1588
E-mail: vflenady@mater.org.au