Relationship of neonatal endotracheal tube size and airway resistance

relationship of neonatal endotracheal tube size and airway resistance

Crt Care Med 28 (5) 6. Oca M J, Becker M A, Dechert R E, Donn S M ( ) Relationship of neonatal endotracheal tube size and airway resistance. These conditions effectuate high airway flows with excessive flow acceleration The most relevant for ΔPETT was the ETT size, followed by (in. Test Lung via standard neonatal endotracheal tubes. R, inspiratory (RJ, and the normal upper airway, but through endotracheal tubes of varying diameter tube size and its resistance (R) has previously been reported by other . ever, the relation between V, and changes in PEEP was slightly curvilinear.

Sophisticated systems composed of reservoirs, wires, heating devices, and other elements are of common use in the intensive care unit [ 49 ]. Aerosolization and Nebulization Aerosol therapy has proven to be an effective form of drug delivery. Despite routine use in the NICUs, the development of appropriate devices as well as medical agents still presents a challenge [ 5051 ]. Equipment for aerosolization in neonates include inhalers metered dose inhalers MDIholding chambers, and nebulizers ultrasonic, jet and vibrating mesh nebulizers, and capillary aerosol generator [ 50 — 52 ].

Examples of drugs used in critically ill neonates are surfactants, corticosteroids, bronchodilators, diuretics, and antiviral and vasoactive agents [ 5051 ].

The particular characteristics of neonatal population low tidal volumes and functional residual capacity, high respiratory rate, a shortened particle residence time, and smaller airway diameters account for the diminished delivery of inhaled aerosol [ 5051 ]. Effectiveness of inhalational therapies is influenced by numerous other factors, including the device itself, type and location of the nebulizer, aerosol characteristics particle size, shape, and densityventilation gas conditions flow and humiditypatient interface, and mode of breathing support [ 50 — 53 ].

Current recommendations for the conventionally ventilated neonate SIMV, AC, VG, and VC and for those who are on CPAP continuous positive airway pressure aim to clean the artificial airways before nebulization, remove the ventilator flow sensor from the wye connector, use vibrating mesh nebulizer Aeroneb, Pari e-flow or MDI with holding chamber, place the device in the inspiratory limb in the circuit 20 cm from the wye connector, and optimize breathing support increase inspiratory time as much as possible, decrease respiratory rate as much as possible, bypass the humidifier, and maintaining air flow heating during nebulization [ 53 ].

Prevention of Infection Infection, and its prevention, is an important concern in neonatal ventilated patients, particularly those of very low birth weight. There are no universally accepted criteria to diagnose VAP in the neonatal period [ 58 ]. Less than month-old infant Center of Disease Control VAP diagnostic guidelines have been used in neonates, according to which, in order to be diagnosed with VAP, the ventilated patient has to fulfil clinical at least one of the following: Microbiological study of tracheal aspirates is not reliable for the diagnosis of VAP since airway colonization cannot be dismissed by this technique.

The standard for microbiological sampling of the airway is bronchoscopic bronchoalveolar lavage and protected specimen brush, whose invasive character precludes its universal use in neonates intubated with small diameter tubes for whom blind-protected bronchoalveolar lavage should be applied [ 61 — 65 ].

Several risk factors have been associated with the occurrence of VAP. Of these, duration of mechanical ventilation and ELBW infants seem to be the most significant in multivariate analysis [ 6061 ], although others like length of hospital stay, reintubation, enteral feeding, mechanical ventilation, transfusion, low birth weight, prematurity, bronchopulmonary dysplasia, and parenteral nutrition have been identified in a recent meta-analysis of observational studies [ 62 ].

On the contrary, decreasing the frequency of ventilator circuit changes from every seven to 14 days does not seem to influence the VAP rate [ 62 ].

Neonate Endotracheal Tube Securement ‘H’ Technique

The most common agents involved in VAP are Gram-negative bacteria particularly Pseudomonas aeruginosa, Enterobacter species, and Klebsiella species although Gram-positive bacteria, namely, coagulase negative staphylococci and Staphylococcus aureus, also play a role [ 61626465 ].

Polymicrobial cultures are frequently found when tracheal aspirate sampling is used. There is no consensus for the initial treatment of VAP. Initial empirical treatment should include broad spectrum antibiotics with coverage for Gram-positive and Gram-negative bacteria, based on likely causative agents and local antimicrobial resistance patterns [ 65 ].

VAP is associated with increased length of hospital stay and mortality [ 61 ]. In the Neo-Kiss registry, Leistner and coworkers found that VAP incidence may influence mortality rate in infants with birth weight between g and g [ 56 ], in accordance with results from other groups of researchers [ 64 ]. Such bundles, which apply several evidence-based practices at the same time, have proved to result in greater practice improvements than the sum of the benefits of each practice on its own [ 66 ].

They should include practices relative to head position in the ventilated neonate, the use of closed multiuse suction catheters, frequency at which suctioning systems should be changed, routine changing of breathing circuits, assessment of readiness for extubation and cautious evaluation of the need for reintubation, use of medications that interfere with gastric acidity, use of antibiotic bowel decontamination and oral hygiene, and use of separate oral and tracheal suctioning equipment [ 66 ].

As with other healthcare-related infections, improvement of caregiver education and hand hygiene remains a very important measure to control VAP incidence. Sedation and Analgesia It is now known that preterm infants are more sensitive to pain than older children and that intubation and invasive mechanical ventilation have physiologic changes determining stress and pain, which can be reduced with sedatives and analgesics [ 67 ].

Nowadays, the prevention and treatment of pain and distress represents an essential component of clinical practice [ 6768 ]. After the correct pain assessment, the treatment of pain and stress should be done. Nonpharmacological interventions such as nonnutritive sucking and sucrose must be tried.

relationship of neonatal endotracheal tube size and airway resistance

Their use in extremely preterm, unstable, ventilated neonates needs to be addressed [ 71 ]. Routine administration of sedation or analgesia in preterm neonates is not recommended due to the safety concerns regarding the pharmacotherapy. Nevertheless, preterm newborns who remain ventilated can be under morphine.

Rarely fentanyl or remifentanil should be used [ 71 ]. We focus in the sedative and analgesic medication usually used in NICUs: Sedative and analgesic medication usually used. In the delivery room, nasal midazolam was more efficient than ketamine to adequately sedate neonates requiring intubation.

The hemodynamics and respiratory effects of both drugs were comparable [ 78 ]. Preterm infants receiving MIST minimal invasive surfactant therapy were more comfortable when sedation was given, but needed ventilation more often [ 79 ]. A randomized controlled trial is necessary to test whether the benefit of sedation outweighs the risks of complications. A neonatal pain and sedation protocol should be implemented in each NICU.

It can increase the opiate exposure, but seems not to affect neurodevelopmental outcomes of extremely preterm infants [ 80 ]. However, as with any medication, the possibility of short- and long-term adverse reactions must be considered.

Nonpharmacological therapy should be used as much as possible [ 8182 ]. Neuromuscular blocking agents are not recommended in the NICU. A transient curarization can be used during brief diagnostic or therapeutic procedures in order to avoid hemodynamic consequences of deep sedation [ 83 ].

Sedation should be reduced and stopped if possible before extubation [ 85 ]. Methylxanthines are helpful in the preterm neonate, and these populations should be started on nasal CPAP or high flow nasal cannula after extubation [ 86 ].

relationship of neonatal endotracheal tube size and airway resistance

Systemic steroids and diuretics may be useful to extubate preterms still ventilated after the first week of life [ 86 ]. Prone positioning can be helpful in stabilizing the chest wall and improving diaphragmatic excursion. A chest radiograph is not routinely necessary, unless there is clinical evidence of respiratory distress [ 86 ].

Tracheostomy Neonatal tracheostomy is a common need of newborns requiring prolonged ventilation. Studies have shown that early tracheostomy reduces the incidence of subglottic and tracheal stenosis in children who are intubated for long periods and results in improved comfort, decreased need for sedation, systemic corticosteroid, improved nutrition and growth, ability to attempt oral feeds, and, once established, vocalization with a speaking valve.

Improved survival of extremely low and very low birth weight and medically complex infants can result in prolonged mechanical ventilation and sometimes tracheostomy [ 87 ]. The indications for neonatal tracheostomy have changed over time. With the need for long-term ventilation, it has become more common [ 88 ].

Overall tracheostomy rate was 6. Common indications for neonatal and infant tracheostomy include congenital or acquired airway obstruction and chronic medical conditions cardiac disease, neuromuscular disease, and bronchopulmonary dysplasia.

Decisions about tracheostomy in neonates involve careful consideration of a number of factors. Mortality, potential short- and long-term outcomes, prospects for home ventilation therapy, and alternatives to tracheostomy should be considered [ 89 ]. The specific technique of neonatal tracheostomy varies little from a well-performed tracheostomy and should be performed in the operating room [ 90 ]. Tracheostomy has the potential for significant morbidity. Meticulous technique, surgeon experience, and specialized care may play a role in reducing the complication rate.

However, complications are usually minor in neonates and do not require additional surgical interventions [ 91 ]. Ventilation in Palliative Care Despite advances in neonatal medicine and intensive care, there are some infants whose treatments are harmful, are not or are no longer beneficial, and may be discontinued after discussion with the family [ 92 ].

The aim of palliative care is to keep the baby comfortable and to support the parents in caring for their baby according to their wishes and beliefs [ 9394 ]. The process of withdrawal includes the explanation to the parents what will happen; which member of staff will be responsible for the actual removal of the endotracheal tube and turning the ventilator off; the aspiration of the nasogastric tube considering not feeding the infant just prior to extubation ; the alarms of the ventilator and monitors should be turned off prior the disconnection; the endotracheal tube should be suctioned before removal; the parents should be given the choice of being present and holding their infant.

Withdrawal of less invasive forms or respiratory support such as nasal continuous positive airway pressure and nasal cannula oxygen may be appropriate if a baby is dying and continued provision of respiratory support only serves to delay death [ 92 — 95 ]. Neuromuscular blocking agents should never be introduced when the ventilator is being withdrawn.

If the newborn has been on paralytics, these should ideally have been weaned off hours to days earlier [ 93 ]. Analgesics and sedatives should be titrated to relieve pain. It is common for children to experience increased pain, agitation, and dyspnea after extubation, requiring increased doses of medication [ 92 ].

In some cases, it is not necessary to turn off the ventilator or extubate the neonate, the parameters of ventilation can be decreased until reaching minimum values, with a decrease of oxygen. Noninvasive ventilation can be used to relief signs of respiratory distress [ 93 ].

Veno-arterial VA ECMO, in addition to increasing blood oxygen content, may provide hemodynamic support by increasing systemic blood flow.

relationship of neonatal endotracheal tube size and airway resistance

This technique, in the presence of pulmonary pathology, should allow the recovery of pulmonary structure and function in order to ensure the survival of the newborn [ 9697 ]. Improvement of native cardiac function may translate into a reduction in arterial oxygen saturation, but with increased tissue oxygen delivery.

After initiating VV-ECMO, weaning from ventilatory and hemodynamic support should be done slowly and with caution, since oxygen delivery is dependent on native myocardial function and, on the other hand, the native lung still provides gas exchanges.

The use of a high PEEP may compromise pulmonary blood flow and cardiac output. In acute technical failure e. Air Leaks and Pulmonary Hemorrhage Air leak syndrome refers to the extravasation of air from the tracheobronchial tree into the lung parenchyma and pleural spaces where it is not normally present, and includes pneumothorax, pulmonary interstitial emphysema, pneumomediastinum, pneumopericardium, pneumoperitoneum, subcutaneous emphysema, and systemic air embolism.

Risk factors include prematurity, very low birth weight, low Apgar score, high peak inspiratory pressure, high tidal volume, high inspiratory time, respiratory distress syndrome, meconium aspiration syndrome, amniotic fluid aspiration, pneumonia, and pulmonary hypoplasia [ — ]. The most frequent air leak in mechanical ventilated newborns is pneumothorax. Different ventilatory strategies affect the risk of pneumothorax with evidence that high-frequency ventilation [ ], volume-targeted ventilation [ ], and increased PEEP [ ] are associated with a decreased risk, and continuous positive inspiratory pressure is associated with an increased risk of pneumothorax [].

The clinical presentation ranges from asymptomatic to severe progressive respiratory distress [ ] and, in case of tension pneumothorax, hemodynamic compromise [ ]. Physical examination may reveal tracheal deviation, asymmetrical chest rise, diminished breath sounds over the affected side, and muffled or shifted heart sounds [ ].

Diagnosis is usually made by radiography [ ]. However, in neonates, the classic appearance may be more difficult to recognize. Therefore, these signs should be looked for in ventilated newborns in order to perform an early diagnosis of pneumothorax.

A tension pneumothorax requires immediate diagnosis and intervention even before imaging is obtained, and chest transillumination plays a role in these cases []. Treatment options include conservative management, nitrogen washout with oxygen, needle aspiration, intercostals tube drainage, and placement of a pigtail catheter. A study including only adult patients reports a rate of spontaneous reabsorption of pneumothorax of 1. An expectant management may be effective even in neonates undergoing mechanical ventilation [], but intervention is most often needed [ ].

Placing the infant under high concentrations of oxygen may hasten the reabsorption of gas in the pleural space by creating a diffusion gradient. However, in neonates, this technique is limited by the oxygen toxicity and increased risk of retinopathy of prematurity [ ].

Needle thoracentesis with aspiration is the preferred treatment in emergencies such as a tension pneumothorax, but may not completely correct the situation [].

Respiratory Care for the Ventilated Neonate

The most traditional method of treatment of a pneumothorax is a chest tube placed by thoracostomy [, ]. However, a recent systematic review found insufficient evidence to determine the efficacy and safety of needle aspiration versus intercostal tube drainage in the management of pneumothorax in newborns [ ].

More recently, pigtail catheters have been used for treatment of pneumothorax in newborns, with evidence to be safe, effective, and reduce discomfort during insertion and complications [ ] including in preterm neonates [ ].

  • Relationship of neonatal endotracheal tube size and airway resistance.
  • Canadian Respiratory Journal

Further prospective randomized controlled trials are necessary to determine which method is superior in the management of neonatal pneumothorax in mechanical ventilated patients.

Other risk factors include pulmonary interstitial emphysema PIEpneumothorax, pulmonary infection, metabolic acidosis, shock, hypothermia, hypoglycemia, disseminated intravascular coagulation DICECMO therapy, hereditary coagulation disorders, and airway trauma especially following endotracheal intubation [].

Pulmonary hemorrhage clinically presents with a rapidly worsening pulmonary function the speed of the setting depends obviously on the magnitude of the hemorrhagewith hypoxia, hypercarbia, and the need for increased ventilatory parameters. Blood can be seen in oropharyngeal or tracheal aspirates.

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A systemic deterioration is established with metabolic acidosis and shock. Investigations should include a chest X-ray, an echocardiogram to exclude a PDAwork-up for sepsis, and eventual screening for hereditary diseases of coagulation if no other risk factors are detected [ ]. Original dimensions mm of shouldered and straight endotracheal tubes of comparable size Figure 1.

Photograph of a 3. Diagrammatic representation of the apparatus used. ETT resistance in the 3. ETT resistance was directly proportional to tube length; shortening a 4. Relationship of resistance to flow rate for the straight endotracheal tubes. Comparison of the relationship of resistance to flow rate of a Cole tube with two straight tubes Solid downward-pointing triangles, 3. Relationship of resistance to flow rate of standard and a shortened 4. Solid diamonds, standard tube Although similar relationships would be expected in vivo, the levels of resistance demonstrated in this and other in vitro studies may be higher than would occur in vivo.

The change in cross-sectional area at the end of a tube influences the total pressure drop along a tube. The greater the change in cross-sectional area, the greater the dissipation of kinetic energy, attributable to the velocity in the tube as it is discharged, and hence the greater total pressure drop along the tube 6.

Generally, pediatric and neonatal ETTs are uncuffed but are relatively close fitting within the trachea to minimize airleak. Under these conditions, there is no abrupt change in cross-sectional area at the distal end of the ETT, and the velocity in this region may be considered constant with no loss of kinetic energy.

In vitro, however, with the distal end of the ETT open to the atmosphere, the change in cross-sectional area is infinite, and the total pressure drop along the tube and hence ETT resistance are much greater as kinetic energy is completely dissipated to the atmosphere. Hence, the values obtained for ETT resistance measured in vitro with the end of the ETT open to the atmosphere, as in this study, will be much greater than ETT resistance under in vivo conditions.

As a consequence, when a ventilated patient in the intensive care setting is measured, subtracting the resistance of the ETT measured in vitro from the results obtained would not give a true assessment of respiratory resistance. To evaluate the total pressure drop along an ETT tube in vitro, with the distal end open to the atmosphere, the total energy at the proximal end must be measured. When Bernoulli's theorem is used, the total energy includes both the pressure energy static pressure and kinetic energy dynamic pressure.

Relationship of neonatal endotracheal tube size and airway resistance.

Static pressure is the pressure exerted by the fluid on any plane parallel to the direction of motion within the tube and is measured with respect to atmosphere, whereas dynamic pressure is the force required to bring the fluid in the tube to rest.

At a constant flow rate, if the tube diameter is reduced, kinetic energy increases. Measurement of dynamic pressure, however, is impractical in very small tubes, because the measuring device itself, a Pitot tube, would significantly disrupt the air flow and prevent accurate pressure measurement. However, when the cross-sectional area of a tube is large, the kinetic energy component is very small compared with the total energy and often can be ignored.

In the present study, flow direction was inspiratory with proximal pressure being measured in a large- diameter ETT We therefore considered the kinetic energy component negligible and, thus, we did not measure the dynamic pressure and do not believe that this would significantly bias our results. Previous studies have given conflicting results. This conflict is easily explained. Hatch 7 compared straight and Cole ETTs of similar outer diameter rather than inner diameter. The mean inner diameter of the Cole tubes is 0.

In the present study, we compared straight tubes of similar inner diameters to the narrow section of the Cole tubes and demonstrated a lower resistance of the latter ETTs, suggesting that shouldered ETT would have an advantage in terms of ETT resistance over the straight tubes in clinical use. However, the sizes commonly used to describe the dimensions of shouldered Cole tubes do not refer to the inner diameters of the wider and the narrow section of the ETT, but rather the inner diameter and outer diameter of the narrow section Table 1.

Hence we compared 3. The outer diameter of the tracheal section of the smaller shouldered Cole tubes is often greater than that of the equivalent straight tube Table 1 ; for example, the outer diameter of a 2. When considering whether to use a smaller Cole ETT, therefore, the clinician must balance the lower ETT resistance against the greater outer diameter and, as a consequence, the possible increased risk of subglottic stenosis.

A number of factors have been proposed as important in the development of subglottic stenosis, including birth weight, gestational age, route and trauma of intubation, frequency of tube change, infection, and duration of ventilation; but Sherman et al. Additionally, there have been concerns that use of Cole tubes might increase the incidence of subglottic stenosis, because of impaction of the shouldered part of the tube onto the cricoid ring, leading to rapid pressure necrosis in the subglottic region Impaction of the tube can be avoided if the tip of the tube is positioned at or above the level of the clavicles on chest radiograph.

This can be achieved either by using a fiberoptic light source at the tube tip or by directly observing the colored tube tip disappearing partially below the vocal chords 11, Our results demonstrate a significantly greater difference in ETT resistance per unit air flow when smaller inner diameter ETTs below 4.

The system characteristics are that pressure drop is proportional to flow rate 2 and therefore inversely proportional to ETT diameter 4. We conclude that ETTs should be cut to an appropriate length and endotracheal tube resistance must be considered if small tubes are to be used, particularly if high flow rates are used. Effects of bronchodilators on airway resistance in ventilator dependent neonates with chronic lung disease. J Pediatr ; Farstad T, Bratlid D: