Cuff compliance of pediatric and adult cuffed tracheal tubes: an experimental study

BACKGROUND: Tracheal mucosal damage related to tracheal intubation has been widely described in pediatric and adult patients. High volume-low pressure cuffs (HVLPC) are being advertised as safe to avoid this particularly unpleasant complication. Compliances of these supposed pediatric and adult HVLPC are not mentioned by manufacturers and still remain unknown. METHODS: The compliance of HVLPC was measured in vitro and defined as the straight portion of the pressure-volume curve. Cuff pressure was measured after incremental 0.1 ml filling volumes of air for sizes 3.0-8.0 of internal diameter of Rüsch and Mallinckrodt tracheal tubes. Compliances were assessed in air and in a rigid tube. The filling volume to achieve a 25-mmHg intracuff pressure was also measured. RESULTS: In air, each 0.1 ml step almost linearly increased cuff pressure by 1 mmHg (size 8.0) to 9 mmHg (size 3). In air, the volume needed to maintain a cuff pressure < 25 mmHg was small for sizes 3-5.5 (0.35-2 ml). The 25 mmHg inflated cuff volume and compliance were decreased within a rigid tube, especially for adult sizes. In a rigid tube simulating a trachea, the compliances of almost every Rüsch tracheal tube were statistically higher than those of the Mallinckrodt. CONCLUSION: We conclude that the tested tracheal tube cuffs have low compliance and cannot be defined as high volume-low pressure.     

Pressure in the cuffs of tracheal tubes at altitude

Pressures in the cuffs of three commonly used tracheal tubes (Portex Profile Softseal, Mallinckrodt Lo-Contour and Mallinckrodt Hi-Contour, size 8.0 mm and 9.0 mm internal diameter), inflated with air, were measured during simulated ascents in an altitude chamber to 10 000 ft. There was no detectable difference in performance between sizes for each type of tracheal tube. When averaged over the two sizes for each type of tube, cuff pressure reached the critical perfusion pressure 50 cmH2O (37 mmHg) for tracheal mucosa at a higher altitude in the Portex Profile Softseal (2837 ft, 95% CI 2488-3186 ft) than in the Mallinckrodt Lo-Contour (2128 ft, 95% CI 1779-2476 ft; p = 0.02) and Mallinckrodt Hi-Contour (1820 ft; 95% CI 1471-2168 ft; p = 0.002) tracheal tubes. When the cuffs of the 9.0-mm tracheal tubes were inflated with saline, much smaller increases in pressure were measured with increasing altitude, although inflation of the cuffs with saline was technically difficult. Commonly used tracheal tubes with air-inflated cuffs can be used for aeromedical retrieval, but air should be evacuated from the cuffs after increases in altitude of as little as 2000-3000 ft.     

Air leakage around endotracheal tube cuffs

BACKGROUND AND OBJECTIVE: To compare the recently introduced Microcuff endotracheal tube with conventional tubes in respect of the cuff pressures required to prevent air leakage. METHODS: The following tubes (ID 7.0mm) were compared: Microcuff HVLP ICU, Mallinckrodt HiLo, Portex Profile Soft Seal, Rüsch Super Safety Clear and Sheridan CF. Fifty patients undergoing endotracheal intubation with a cuffed tube of internal diameter 7.0 mm were studied. Tracheas were intubated using one of the endotracheal tubes in random order. Cuff pressure to prevent air leakage at standardized ventilator setting (peak inspiratory pressure 20 cmH2O/PEEP 5 cmH2O/respiratory rate 15 breaths min(-1)) was assessed by auscultation of audible sounds at the mouth. Patients characteristics and cuff pressures from each brand were compared to the Microcuff group using the Mann-Whitney U-test (P < 0.05 was chosen as the level of statistical significance). RESULTS: Patients' median age (range) was 14.2 (12.0-17.1) yr, body weight 57.5 (40.0-81.9) kg and length 164.9 (146.5-190.0) cm. No significant differences in patients' characteristics were found between groups. Mean cuff pressure (all tubes) required for air sealing was 19.1 (8-42) cmH2O. The Microcuff tube required significantly lower sealing pressures (9.5 (8-12) cmH2O) compared to the other brands of endotracheal tube (P < 0.05, Mann-Whitney U-test). CONCLUSION: The Microcuff endotracheal tube with its ultra-thin polyurethane cuff membrane required the lowest sealing pressure to prevent air leakage. These features are potentially of interest for long-term intubated patients and for cuffed endotracheal tubes in children, allowing tracheal sealing at lower cuff pressures implying less damage to the trachea.     

Leakage of fluid around high-volume, low-pressure cuffs apparatus A comparison of four tracheal tubes

We studied the ability of high-volume, low-pressure tracheal tube cuffs (Portex Soft Seal, Portex Profile, Mallinckrodt Lo-Contour and Mallinckrodt Hi-Lo tubes) to prevent leakage of fluid into the airway, in a model trachea and lung. Five tubes (7.0 and 8.0 mm internal diameter) of each type were used. Each tube was inserted into the model trachea and the cuff inflated until the intracuff pressure reached either 20, 30 or 40 cm H2O. The model lung was ventilated with a tidal volume of 700 ml and respiratory rate of 14 breath.min-1 at a compliance of 20 cm H2O. Ten millilitres of 0.01% methylene blue solution were infused over the cuff and the volume of fluid leaking past the cuff over 5 min was measured. The leak volume for the Soft Seal tube was less than that for the Profile or Lo-Contour tubes at all intracuff pressures (all p<0.05). Compared with the Hi-Lo tube, the volume leaking past the cuff for the Soft Seal tube was greater at an intracuff pressure of 20 cm H2O (p<0.05), whereas there was no significant difference between these two tubes at an intracuff pressure of 30 or 40 cm H2O. We conclude that the cuff of the Portex Soft Seal tube prevented leakage of fluid significantly more than that of the Portex Profile or Mallinckrodt Lo-Contour tubes, and to a similar degree to that of the Mallinckrodt Hi-Lo tube.     

Bronchial cuff pressure change caused by left-sided double-lumen endobronchial tube displacement

PURPOSE: The bronchial cuff pressures (BCPs) of left-sided double-lumen endobronchial tubes (DLTs) manufactured by Rüsch and Mallinckrodt were measured in 80 patients when the tubes were withdrawn to compare the effect of tube design on BCP change. METHODS: During general anesthesia with muscle relaxation, the cephalad surface of the endobronchial cuff was positioned either 2.5 cm distal to the carina (Rüsch Group R-I; n = 20 and Mallinckrodt Group B-I; n = 20) or just below the carina (Rüsch Group R- II; n = 20 and Mallinckrodt Group B- II; n = 20) and the cuff was inflated to 35 cm H2O. The tube was then withdrawn in 0.5-cm steps until the cuff was 2.0 cm proximal to the carina, the position just before the capnogram or pressure-volume loop of tracheal lumen changed. The BCP at each step was measured. The rate of decrease in BCP was defined as the decrease of BCP divided by the length of displacement of DLT. RESULTS: The rates of decrease from the +2.5 cm position to the end point in Group B-I (7.7+/-0.8 cm H2O x cm(-1) and those from the most proximal acceptable position to the end point in Group B-II (19.5+/-4.8 cm H2O x cm(-1) were greater than those in Group R-I (6.9+/-0.9 cm H2O x cm(-1) (P<0.01) and in Group R-II (12.4+/-3.1 cm H2O x cm(-1)) (P<0.01), respectively. CONCLUSION: The BCP decreased in both of the Mallinckrodt and Rüsch DLTs, and the rates of decrease of the former were greater than those of the latter.     

Outer diameter and shape of paediatric tracheal tube cuffs at higher inflation pressures

Cuffed tracheal tubes are becoming increasingly popular in paediatric anaesthesia and intensive care medicine. To avoid cuff related complications and airway morbidity, a thorough understanding of cuff volume/pressure behaviour and management is required. In this study, the outer cuff diameter and form stability of the cuff at high cuff pressure were assessed in a series of different paediatric cuffed tracheal tubes with internal diameter of between 3.0 and 5.0 mm. The main findings were that small amounts of inflated air led to a rapid increase in cuff pressure and volume and that the outer cuff diameters increased to 2-2.5 times the age-corresponding internal tracheal diameter following inadvertent syringe inflation. Careful cuff inflation under cuff pressure monitoring and/or automatic cuff pressure release is recommended in paediatric tracheal tube cuffs to prevent airway damage caused by manual inflation, pilot balloon compression and nitrous oxide diffusion.     

Nitrous oxide diffusion into tracheal tube cuffs: comparison of five different tracheal tube cuffs

BACKGROUND: The aim of this study was to investigate cuff compliance and cuff pressure during nitrous oxide exposure in the recently introduced Microcuff tracheal tube with a polyurethane cuff (Microcuff GmbH, Weinheim, Germany), and to compare it to conventional tracheal tubes with PVC cuffs. METHODS: In an in vitro set up, five cuffed tracheal tubes (ID 7.0 mm) from different manufacturers (Microcuff HVLP, Portex Profile Soft Seal, Mallinckrodt HiLo, Rüsch Super Safety Clear and Sheridan CF) were studied. Pressure-volume curves were assessed and changes of cuff pressure during exposure to nitrous oxide (for 60 min; 66% N(2)O in oxygen) were recorded without and with restriction of the cuff in a trachea model. Each experiment was performed four times using two exemplars of each tube twice. Sixty-minute values of the Microcuff group were compared with the other groups using the Mann- Whitney test (P < 0.05). RESULTS: The Microcuff polyurethane cuff demonstrated an intermediate cuff compliance but the highest cuff pressure increase during nitrous oxide exposure under unrestricted conditions. When inflated within the artificial trachea its cuff compliance became the highest of all tested tracheal tubes. However, exposure to N(2)O, again led to a rapid increase in cuff pressure. CONCLUSION: The ultra-thin polyurethane tube cuff demonstrated higher permeability for nitrous oxide than conventional PVC cuffs and led to a rapid cuff pressure increase when exposed to N(2)O. Routinely checking of cuff-pressure or filling the cuff with nitrous oxide are more important than the brand of tube used.     

Tracheal sealing by auto-inflation in tracheal tube cuffs

BACKGROUND: The purpose of this study was to determine if inspiratory pressure from intermittent positive pressure ventilation may be sufficient to inflate the cuff (thus 'auto-inflation') and thereby seal the trachea. METHODS: In a laboratory model we investigated the ability of cuffs of seven 5.0 mm internal diameter (ID) tracheal tubes (Sheridan CF, Mallinckrodt Hi-Contour, Mallinckrodt Sealguard, Mallinckrodt Safety-Flex, Portex Soft Seal, Rueschelit Super-Safety Clear and Microcuff PET) to seal the trachea by auto-inflation, i.e. by using the inspiratory pressure to expand and keep open the cuff within the trachea. A mechanical lung connected to a model trachea made from clear, rigid polyvinylchloride (PVC) (12 mm ID) was used to simulate changes in inspiratory pressures. Respirator settings were: fresh gas flow (air) 6 lxmin(-1); positive end-expiratory pressure 5 cmH(2)O; respiratory rate 20 brxmin(-1); I : E ratio = 1 : 2; inspiratory pressure 5, 10, 15, 20, and 25 cmH(2)O. Percentage of expiratory to inspiratory tidal volume (E : I V(t) volume ratio) was calculated. RESULTS: Using lubricated Mallinckrodt Seal Guard tube cuffs E : I V(t) volume ratio was almost 100% at a peak inspiratory pressure of 10 cmH(2)o whereas in tube cuffs particularly made of PVC an E : I ratio was achieved only at higher inspiratory pressures, if at all. CONCLUSIONS: Auto-inflation in the Mallinckrodt Seal Guard with high volume-low pressure polyurethane cuff can produce adequate tracheal sealing in the model trachea used. The implication is that such auto-inflation should decrease the risk of tracheal injury from acute or persistent cuff hyperinflation.     

Tracheal sealing characteristics of pediatric cuffed tracheal tubes

BACKGROUND: The aim of the study was to compare sealing characteristics of the new Microcuff pediatric tracheal tube featuring a high volume-low pressure (HVLP) cuff with ultrathin membrane with three conventional pediatric cuffed tracheal tubes. METHODS: After obtaining approval of the local ethical committee, 80 children aged 2-4 years were tracheally intubated with the following tubes (i.d. 4.0 mm) in random order: Microcuff P-HVLP, Mallinckrodt Hi-Contour P, Rüschelit Super Safety Clear, and Sheridan CF. Cuff pressure to prevent air leakage at standardized ventilator setting (PIP 20 cm H2O/PEEP 5 cm H2O/RR 20 min(-1)) was assessed within 5 min after intubation by auscultation of audible sounds at the mouth. Cuff pressures required with each group were compared with Kruskall-Wallis test (P < 0.05). Values are median and range. RESULTS: No significant differences in patient characteristics were found between the four groups. The Microcuff tube required significantly lower sealing pressures [11 cm H2O (6-26)] compared with the other tracheal tube brands [Mallinckrodt: 36 cm H2O (18-48); Rüschelit: 21 cm H2O (8-46); Sheridan: 26 cm H2O (18-60), (P < 0.0001)]. CONCLUSION: This preliminary investigation suggests that the new Microcuff pediatric tracheal tube with ultrathin high volume-low pressure cuff membrane allows effective tracheal sealing at very low cuff pressures. This represents a benefit for children with regard to their lower mucosal perfusion pressures compared with adult patients.     

Pressure-volume relationship for paediatric cuffed tracheal tube

OBJECTIVE: Define the pressure-volume relationship of the cuff of paediatric cuffed tracheal tubes. STUDY DESIGN: Experimental study. MATERIALS AND METHODS: The cuff pressure was measured after incremental 0.1 ml filling volumes for 6 sizes (3.0 to 5.5 mm of internal diameter) of paediatric high volume-low pressure cuffed-tracheal tubes. The pressure-volume relationship of the cuff was assessed with and without resistance to the filling. Results were expressed with medium +/- SD. RESULT: Each increment increased the cuff pressure, without resistance, of 7.3 +/- 1.7 mmHg for sizes 3.0, 3.5 and 4.0, 4.8 +/- 1.6 mmHg for size 4.5, and 2.3 +/- 0.9 mmHg for sizes 5 and 5.5. The resistance decreased the filling volume of the cuff for each size of tracheal tubes. CONCLUSION: The margin of safety provided by cuff of smallest cuffed tracheal tubes is too small. Then, the smallest sizes (3.0 to 4.5) should not be called low pressure-high volume cuff.     

Evaluation of a new recommendation for improved cuffed tracheal tube size selection in infants and small children

BACKGROUND: The purpose of this study was to evaluate a new recommendation for tracheal tube size selection using second-generation Microcuff paediatric endotracheal tubes (PETs) with optimized outer diameter (OD) of the distal tube. METHODS: With Ethics Committee approval, patients aged from birth to 5 years, requiring general anaesthesia with orotracheal intubation, were included. Tracheal tube sizes were selected as follows: internal diameter (ID) 3.0 mm, birth (if > or =3 kg) to <6 months; ID 3.5 mm, 6 to <18 months; ID 4.0 mm, 18 months to <3 years; ID 4.5 mm, 3 to <5 years. Tracheal tubes with the cuff not inflated were classified as too large if no air leak was obtained at an airway pressure of < or =20 cmH2O. Post-intubation stridor requiring therapy was noted. RESULTS: Three hundred and fifty children were studied. Nine tracheal tubes (2.6%) were too large and had to be exchanged: in patients requiring tracheal tubes of ID 3.0 mm and 3.5 mm, three and four tracheal tubes, respectively, and, in patients requiring tracheal tubes of ID 4.0 mm and 4.5 mm, one tracheal tube in each group. In three patients (0.9%), post-intubation stridor occurred which required therapy. CONCLUSION: The new recommendation presented for the use of second-generation Microcuff PETs with improved OD to ID ratio allows the selection of cuffed tracheal tubes with larger IDs than previously recommended for small children without increased need for tracheal tube exchange or increased incidence of post-intubation stridor in these age groups.     

Prevention of silent aspiration due to leaks around cuffs of endotracheal tubes

Significant aspiration may occur around correctly inflated high volume, low pressure endotracheal tube cuffs. The prevention of silent aspiration due to leaks around cuffs of endotracheal tubes was investigated during general anesthesia for hip replacement in 47 patients. The patients were randomly assigned to one of three groups, in which one of three endotracheal tubes of different designs were used for intubation. The following three tubes were used: the red rubber Rüsch tube with low residual volume cuff, inflated to minimum occluding volume; the Mallinckrodt Hi-Lo tube with high residual volume cuff; the NL tube with high residual volume cuff and automatic cuff pressure regulation. The cuffs on the Mallinckrodt and the NL tubes were inflated to 29-31 cm H2O. One hour before termination of the surgical procedure, 1 ml methylene blue dye was injected into the trachea just above the cuff through a thin channel built into the tubes. At termination of the operation, the trachea below the cuff was inspected with a fiberoptic bronchoscope. Aspiration was found in 12.5% with the Rüsch tube, in 31.2% with the Mallinckrodt tube, and in 0% with the NL tube. Our results show that silent aspiration is still a problem with standard endotracheal tubes, but that it may be minimized by use of appropriate tubes, cuffs, and control of cuff inflation.     

Configuration of the SCOTI device with different tracheal tubes

We have evaluated the Sonomatic Confirmation of Tracheal Intubation device (SCOTI) by testing its ability to be correctly configured with a variety of tracheal tubes of differing internal diameter and length. The device only configured correctly for RAE tubes with internal diameter of 7.0 mm or greater and for armoured tubes of internal diameter 8.5 mm. For conventional tubes of varying internal diameter cut to different lengths, configuration was only successful with certain dimensions. The inability to configure the device correctly with all types and lengths of tracheal tubes limits its usefulness as a indicator of tracheal intubation.     

Fit and seal characteristics of a new paediatric tracheal tube with high volume-low pressure polyurethane cuff

BACKGROUND: To evaluate a new paediatric tracheal tube (Microcuff, Weinheim, Germany) with an ultrathin high volume-low pressure polyurethane cuff. METHODS: With approval of the Hospital Ethics Committee tracheas of children undergoing general anaesthesia were intubated using a Microcuff tube. Tube sizes were selected according to: internal diameter (mm) = age/4 + 3.5 in children aged > or = 2 years. In newborns (> or = 3 kg) < or = 1 year, ID 3.0-mm tubes, and in children from 1 to 2 years, internal diameter 3.5-mm tubes were used. Tubes were classified too large if no air leakage was obtained at an airway pressure of 20 cm H2O with the cuff not inflated. Sealing pressure was assessed by auscultation. Post-extubation croup requiring therapy was noted. RESULTS: Five-hundred children were studied. In eight children the tubes were too large. Sealing pressure was 9.7 +/- 2.5 cm H2O (4-20). In two patients postextubation croup required singular short-term therapy. CONCLUSIONS: Microcuff paediatric tracheal tubes provided tracheal sealing with cuff pressures considerably lower than usually accepted. The rate of tube exchange was very low (1.6%), as was the rate of airway morbidity (croup requiring therapy; 0.4%).     

TRACHEAL TUBES AND CONNECTORS USED IN NEONATES-DIMENSIONS AND RESISTANCE TO BREATHING

The dimensions of tracheal tubes and connectors in common usewere measured together with the resistance to breathing at flowrates occurring in babies breathing quietly. The outside diametersof rubber tubes varied more than those of plastic tubes. Themain factors influencing resistance were the internal diameterand a sudden change in diameter or direction of flow. Theseare of particular importance in tubes of 2.5 mm i.d. and lessand may cause an increase in the work of breathing during spontaneousventilation. The resistance of small Cole pattern tubes wasgreater than that of plain tubes of similar o.d.     

Evaluation of pressure changes in a new design tracheal tube cuff, the Portex Soft Seal, during nitrous oxide anaesthesia

We have measured pressure changes in a newly designed tracheal tube cuff, the Portex Soft Seal, during nitrous oxide anaesthesia compared with a Mallinckrodt Lo-Contour tube and a Portex Profile tube. The pressure increases in both control groups were significantly greater than those with the new design (P < 0.0001 in each case). The mean increase in pressure in the Mallinckrodt Lo-Contour tube cuff was 9.9 (SD 3.4) mm Hg compared with 10.3 (1.8) mm Hg in the Portex Profile tube cuff and 2.1 (1.5) mm Hg in the Portex Soft Seal tube cuff. We conclude that the Portex Soft Seal cuff prevented a significant increase in intracuff pressure during nitrous oxide anaesthesia.      

Tracheal tube size in adults undergoing elective surgery – a narrative review

Tracheal tubes are routinely used in adults undergoing elective surgery. The size of the tracheal tube, defined by its internal diameter, is often generically selected according to sex, with 7–7.5 mm and 8–8.5 mm tubes recommended in women and men, respectively. Tracheal diameter in adults is highly variable, being narrowest at the subglottis, and is affected by height and sex. The outer diameter of routinely used tracheal tubes may exceed these dimensions, traumatise the airway and increase the risk of postoperative sore throat and hoarseness. These complications disproportionately affect women and may be mitigated by using smaller tracheal tubes (6–6.5 mm). Patient safety concerns about using small tracheal tubes are based on critical care populations undergoing prolonged periods of tracheal intubation and not patients undergoing elective surgery. The internal diameter of the tube corresponds to its clinical utility. Tracheal tubes as small as 6.0 mm will accommodate routinely used intubation aids, suction devices and slim-line fibreoptic bronchoscopes. Positive pressure ventilation may be performed without increasing the risk of ventilator-induced lung injury or air trapping, even when high minute volumes are required. There is also no demonstrable increased risk of aspiration or cuff pressure damage when using smaller tracheal tubes. Small tracheal tubes may not be safe in all patients, such as those with high secretion loads and airflow limitation. A balanced view of risks and benefits should be taken appropriate to the clinical context, to select the smallest tracheal tube that permits safe peri-operative management.     

The additional work of breathing through Portex Polar 'Blue-Line' pre-formed paediatric tracheal tubes.

The work of breathing through north- and south-facing Portex Polar 'Blue-Line' paediatric tracheal tubes of sizes 3.0-7.0 mm ID has been measured using sinusoidal flow at equivalent ventilatory rates of 10-50 breaths min-1 with tidal volumes of 10-500 ml. North-facing tubes are designed to sit with the connection on the forehead after intubation, whilst south-facing ones are designed so that the connection sits on the chin of the patient. It was found that the total work of breathing through north-facing tubes is approximately 8% higher than the total work of breathing through south-facing tubes of the same size, irrespective of tidal volume or respiration rate. The total work of breathing was dependent on total tube length but independent of tube design. The endotracheal connectors themselves were found to contribute a significant proportion of the total work of breathing but there was no significant difference between the inspiratory and expiratory performance of the tubes.     

Improving the shape and compliance characteristics of a high-volume, low-pressure cuff improves tracheal seal

A prototype design of a compliant latex, high-volume, low-pressure cuffed tracheal tube cuff (CHVLP) was compared with the Mallinckrodt Hi- Lo, Sheridan preformed and Portex Profile high-volume, low-pressure (HVLP) cuffed tracheal tubes for leakage of dye placed above the cuff in a benchtop mechanical ventilation model and in five isolated pig tracheas. There was no leakage in the ventilation model or in the pig tracheas with the prototype CHVLP. There was rapid leakage in the ventilation model and in all the pig tracheas for the Mallinckrodt Hi- Lo, the Sheridan preformed and the Portex Profile cuffs. This benchtop study suggests that improved HVLP cuff compliance characteristics may be beneficial in the prevention of leakage of fluid to the lungs known to occur with HVLP cuffs.      

Tracheal tube resistance and airway and alveolar pressures during mechanical ventilation in the neonate

The relationship between peak airway pressure, alveolar pressure and respiratory frequency was calculated for the range of compliances and airway resistances which might be encountered during mechanical ventilation of a 3-kg neonate. The pressure/flow relationships of 2.5, 3.0, 3.5 and 4-mm tracheal tubes were determined at a series of flows from 0.5 to 4 litres/minute. Peak airway and alveolar pressures were then measured at various frequencies and inspiratory:expiratory ratios with the tubes incorporated in a model lung. Large differences between peak airway and alveolar pressures developed when frequency was increased or inspiratory time decreased; the differences were greatest with the smaller tubes. Shortening expiratory time by increasing the frequency or altering the inspiratory:expiratory ratio resulted in increased end-expiratory pressure because of incomplete emptying of the lung.