Kyoji Tsuno

Design and Development of Ultrathin-walled, Nonkinking Endotracheal Tubes of a New “No-pressure” Laryngeal Seal Design: A Preliminary Report

BackgroundEndotracheal tubes (ETTs) of conventional design and manufacture greatly increase the air-flow resistance of the upper airways. This increase in upper-airway resistance can lead to a significant increase in the work of breathing and may necessitate the use of assisted mechanical ventilation. Current ETTs are relatively stiff and contribute greatly to patient discomfort. The inflatable cuffs now mounted onto the ETTs function well in short-term use but impart significant morbidity when used over longer periods. These issues were addressed by the designing of a low-resistance ETT. MethodsUsing new techniques, we developed ultrathin-walled, wire reinforced ETTs of conventional configuration and ETTs the oropharyngeal-section diameter of which was a few millimeters larger than the diameter of the tracheal section. The wall thickness was a constant 0.20 mm. The wire reinforcement was stainless steel flat wire or superelastic nickel-titanium alloy. The superelastic nickel-titanium alloy reinforcement made those ETTs crush-proof; after forceful manual compression, recovery was complete. To obtain a seal with the upper airways, we first shaped a short section of the oropharyngeal section of the ETT from round to oval (or egg-shaped) to conform better to the larynx. We then attached to this segment numerous soft, pliable, 0.025–0.075-mm-thick rings of polyurethane to occlude voids for potential air leaks from within the larynx. ResultsIn vitro pressure-flow studies showed a decrease by as much as four- or fivefold in air-flow resistance in the adult ETT range, effectively increasing the internal diameter by 2.3–3.7 mm, compared with conventional ETTs of the same outside diameter. In vivo studies for 24 h in sheep showed no air leaks at airway pressures to 30 cmH2O and minimal leak at greater pressures. The gross appearance of the trachea was normal. ConclusionsAlthough the new tubes appear to offer advantages to those currently used, testing in humans is required to assess the clinical utility of the tube-cuff design.

Acute respiratory failure induced by mechanical pulmonary ventilation at a peak inspiratory pressure of 40 cmH20

The effects of high pressure mechanical pulmonary ventilation at a peak inspiratory pressure of 40 cmH20 were studied on the lungs of healthy newborn pigs (14–21 days after birth). Forty percent oxygen in nitrogen was used for ventilation to prevent oxygen intoxication. The control group (6 pigs) was ventilated for 48 hours at a peak inspiratory pressure less than 18 cmH20 and a PEEP of 3–5 cmH20 with a normal tidal volume, and a respiratory rate of 20 times/min. The control group showed few deleterious changes in the lungs for 48 hours. Eleven newborn pigs were ventilated at a peak inspiratory pressure of 40 cmH20 with a PEEP of 3–5 CmH20 and a respiratory rate of 20 times/min. To avoid respiratory alkalosis, a dead space was placed in the respiratory circuit, and normocarbia was maintained by adjusting dead space volume. In all cases in the latter group, severe pulmonary impairments, such as abnormal chest roentgenograms, hypoxemia, decreased total static lung compliance, high incidence of pneumothorax, congestive atelectasis, and increased lung weight were found within 48 hours of ventilation. When the pulmonary impairments became manifest, 6 of the 11 newborn pigs were switched to the conventional medical and ventilatory therapies for 3–6 days. However, all of them became ventilator dependent, and severe lung pathology was found at autopsy. These pulmonary insults by high pressure mechanical pulmonary ventilation could be occurring not infrequently in the respiratory management of patients with respiratory failure.

Newborn extracorporeal lung assist using a novel double lumen catheter and a heparin-bonded membrane lung

We report the clinical application of a novel double lumen catheter for veno-venous extracorporeal lung assist (ECLA) and the use of a heparin-bonded hollow fiber membrane lung, in the treatment of newborn respiratory failure. The outer lumen of the double lumen catheter was 14 Fr and was used for blood drainage; while the inner 8 Fr catheter was used for blood return. The double lumen catheter was made of spiral wire reinforced polyurethane, with a wall thickness of 0.25 mm. The hollow fiber membrane was made of non-microporous polyolefin, and was not permeable to water or plasma. We used this system to treat a newborn patient with meconium aspiration syndrome. Heparin was infused continuously at a rate of 18–25 units/kg/h, equal to 1/3 of the usual amount when a non-heparin bonded ECLA system was used and maintaining the activated clotting time near 120 s. Bleeding from cutdown sites was negligible. Only the right internal jugular vein was sacrificed. The patient was successfully weaned from ECLA and appears normal one year following discharge.

To-and-fro veno-venous extracorporeal lung assist for newborns with severe respiratory distress

A veno-venous to-and-fro bypass method through a single blood access for extracorporeal lung assist with an artificial membrane lung is introduced. A premature newborn with severe respiratory distress was treated with this method. A 12 Fr. single lumen catheter with a spiral-embedded thin-wall, 0.25 mm in wall thickness, was placed in the right internal jugular vein. Venous blood was withdrawn and oxygenated blood returned alternately through the same catheter. Thus both carotid arteries and other large veins were kept intact. During the extracorporeal bypass, the patient was put on intermittent mandatory ventilation of 2 times/min for lung rest providing adequate arterial blood gases, and he survived.

Extracorporeal lung assist for two cases of severe acute respiratory failure

Mechanical pulmonary ventilation (MY) is routinely used for patients with acute respiratory failure (ARF). High airway pressures are at times required to attain alveolar ventilation according to the lung stiffness. However, Kolobow et al. l 3 have recently warned of the insulting effects of MY on the healthy lung. They suggest that the .upper safety limit of lung inflation should be less than 3 times of the normal tidal volume and/or less than 30 cmH20 of the peak inspiratory pressure (PIP). MY with a high PIP might iatrogenically cause overinflation of the still functioning healthy alveoli in the damaged lungs, and worsen ARF. A PIP of over 50 cmH20 was neeessary for two critically ill patients with ARF during conventional MY, and a lifethreatening barotrauma developed. They were treated with veno-venous extracorporeal bypass with an artificial membrane lung (ML). The PIP was lowered to 3035 cmH2 0 or less by decreasing the tidal volume (YT ) during the bypass, and it resulted in an improvement in the lungs.

Treatment of Hypoxemia during Esophagectomy by High Frequency Jet Ventilation

Severe hypoxemia due to lung collapse on the operation side sometimes occurs during thoracotomy. It can usually be COUIlt.eracted with a high FlO,. But, we have experienced a patient who showed refractory hypoxemia even under intermittent positive pressure ventilation (IPPV) through a single lumen endotracheal tube at an Flo, of 1.0 during esophagcctorny, The collapsed lung was inflated and the bilateral lungs were ventilated manually or with mechanical ventilation (MV) to maintain Pao, at a physiologic range. However, the inflated hmg hid the operation field. When the lung was placed aside with a retractor for continuing the operation, the Pao, fell again below an acceptable level. Therefore, we superimposed high frequency jet ventilation (HFJV) on IPPV. Superimposed HF,lV resulted in good pulmonary oxygenation as well as providing satisfactory operative conditions, Case Report A 66-years-old male, with a past history of hypertension and cerebral apoplexy, underwent esophagectorny for esophageal carcinoma. He had worked as a miner for 15

To-and-fro extracorporeal lung assist (ECLA) through a single catheter — in premature goats as an experimental model of infant respiratory insufficiency

A new to-and-fro V-V bypass extracorporeal lung assist (ECLA) through a single catheter as a blood access was investigated for its efficacy on six premature goats delivered by Cesarean section at a gestational age of 118 ∼ 139 days as an experimental model of infant respiratory insufficiency, then applied to a human premature infant suffering from life threatening barotrauma that had developed from mechanical pulmonary ventilation. The extracorporeal bypass flow and the gas flow to the artificial membrane lung were controlled to keep PaO2 above 40 mmHg and PaCO2 within normal limits. The neonate’s own lungs were treated with a continuous positive airway pressure of 5 ∼ 12 cmH2O, apneic oxygenation or IMV. Two goats weighing 1250 g and 700 g died 2 ∼ 2.5 hours after birth from severe circulatory distress. However, the other four neonates which were heavier than 2000 g, were successfully weaned from ECLA, and three of these could be weaned from mechanical ventilation as well. A human infant also survived and was weaned from ECLA on the third day.