Unidirectional valve malfunction by the breakage or malposition of disc: two cases report / 대한마취과학회지

Malfunction of the unidirectional valve in a breathing circuit system may cause hypercapnia from the rebreathing of expired gas, ventilation failure, and barotrauma. Capnography is a useful method for monitoring the integrity of the unidirectional valve. We experienced two cases of malfunction of a unidirectional valve which caused leakage and reverse flow, diagnosed early as a change of the capnographic waveform. One case was caused by expiratory unidirectional valve breakage. The other was caused by an incorrectly-assembled inspiratory unidirectional valve.

Ventilation impairment caused by upside-down connected unidirectional valves: A case report / 대한마취과학회지

We experienced a case of ventilation impairment resulted by the wrong-assembled unidirectional valves passed the automatic checkout of ventilator during general anesthesia. A 63-year-old man was scheduled for Ivor-Lewis operation due to esophageal cancer. After endotracheal intubation, ventilation impairment and abdominal distension were developed. No abnormal finding was found with bronchofiberoscopic examination. Suspecting anesthetic equipment failure, unidirectional valves were separated and they were proved to be connected upside-down.

Expiratory Valve Malfunction Detected Immediately after Endotracheal Intubation: A case report / 대한마취과학회지

The malfunction of an expiratory unidirectional valve (EV) can cause rebreath of expired gas, barotraumas, or ventilatory failure during the general anesthesia. The following is a report on a case of ventilatoryfailure caused by an EV that failed to open during the induction of anesthesia. A 57-year-old man was scheduled for the biopsy of a vocal cord polyp. After intubation, we could not detect the evidence of ventilation through the endotracheal tube. Suspecting the esophageal intubation, we administered extubation. The patient was still having difficulty in ventilating even after a retrial of intubation. Then we discovered the EV was failing to open properly with ventilation and thus not able to function properly. The common cause of ventilatory failure immediately after intubation is malposition of an endotracheal tube, like esophageal intubation, and equipment failure also has reported. Accordingly, we should remember possible causes of ventilatory failure after intubations and routine conscientious inspection of the ventilator.

Comparação de dois métodos de mensuração da pressão inspiratória máxima em pacientes com e sem alterações do nível de consciência / Comparison of two methods for measurement of maximal inspiratory pressure in patients with and without alterations of the conscience's level

JUSTIFICATIVA E OBJETIVOS: Não existe consenso na literatura sobre o tempo de oclusão das vias aéreas necessário para se obter uma PImax verdadeira durante o desmame da ventilação mecânica (VM). Assim, o presente estudo teve por objetivos comparar dois métodos de mensuração da PImax e avaliar a influência do nível de consciência do paciente nessas medidas. MÉTODO: População composta de 28 pacientes gerais de UTI, com tempo de VM > 48h, em processo de desmame, divididos em dois grupos de acordo com a pontuação na escala de coma de Glasgow (ECGL): com (ECGL< 15) e sem alteração do nível de consciência (ECGL = 15). A via aérea foi ocluída com uma válvula unidirecional por 20s (PImaxT20), ou pelo tempo máximo de um minuto, se um platô de pressão inspiratória não foi observado durante três inspirações consecutivas (PImaxTid). RESULTADOS: A PI Max T20 (média ± DP, cmH2O) foi semelhante em ambos os grupos (44 ± 16 vs 42 ± 15, p = 0,52). No entanto, os valores da PImaxTid, assim como o tempo necessário para sua obtenção, foram maiores no grupo ECGL< 15 (65 ± 24 vs 47 ± 23 cmH2O e 37 ± 10 vs 24 ± 8s, p = 0,04 e 0,0019, respectivamente). CONCLUSÕES: O método comumente utilizado de 20s de oclusão da via aérea parece ser insuficiente para se mensurar a verdadeira PImax em pacientes com alterações do nível de consciência. Estudos adicionais, agora num grupo mais homogêneo de pacientes (p. ex.: com alterações neurológicas estruturais), são necessários para maior esclarecimento destes resultados.

BACKGROUND AND OBJECTIVES: There is no literature consensus about the time of airway occlusion sufficient enough to get a true PImax during weaning from mechanical ventilation (MV). So, the main objectives of the present study were to compare two methods PImax measurement and to evaluate the influence of patients' level of conscience on them. METHODS: The population was composed by 28 general ICU patients, with MV > 48h, in a weaning process, divided into two groups according to Glasgow coma scale score: with (GCS < 15) and without (GCS = 15) alterations of conscience level. The airway was occluded by using an unidirectional valve for 20s (PImaxT20), or for a maximum time of one minute if a plateau of inspiratory pressure was not observed during three consecutive inspirations (PImaxTid). RESULTS: PImaxT20 (mean ± SD, cmH2O) values were similar in both groups (44 ± 16 vs42 ± 15, p = 0.52). However, PImaxTid values, as long as the time needed to their attainment, were greater in GCS < 15 group (65 ± 24 vs 47 ± 23cmH2O and 37 ± 10 vs24 ± 8s, p = 0.04 and 0.0019, respectively). CONCLUSIONS: The method commonly used of 20s airway occlusion seems to be inadequate to get the true PImax in patients with alterations of the level of conscience. Additional studies, now in a more homogeneous group (e. g.: patients with structural brain lesion), are needed to clarify these findings.

Expiratory Unidirectional Valve Malfunction Detected by Capnographic Waveform Change: A case report / 대한마취과학회지

Unidirectional valve (UDV) malfunction causes rebreathing of expired gas during anesthesia. However, the resultant hypercarbia without hypoxemia by UDV malfunction is not easily detected. We experienced a case of severe hypercarbia which caused by sticking expiratory valve at 45 minutes after the induction of anesthesia, in spite of checking UDV function preoperatively. In this case, expiratory UDV malfunction was diagnosed with the change of capnographic waveform. And so, we recommend monitoring of capnographic waveform during every anesthesia, in addition to preoperative UDV checking.

A Report of Three Cases of Hypercarbia During General Anesthesia / 대한마취과학회지

It is common to use semiclosed circle system for general anesthesia because of economy, easy controllability of humidity and temperature, less contamination of operating room with anesthetic gas etc, but in case of malfunction of unidirectional valve, inappropriate absorption of carbon dioxide,leakage or obstruction of circle system the patient may become fatal. During general anesthesia with newly purchased anesthesia machine(Ohmeda Modulus II plus) we experienced three cases of hypercarbia because of malfunction of expiratory valve which could not be easily found due to overlying PEEP valve.

Occurrence of Hypercarbia due to a Defective Unidirectional Valve / 대한마취과학회지

Hypercarbia can occur in spite of adequate ventilation if removal of carbon dioxide from the inspired gases is inadequate. Neither blood pressure nor heart rate is a reliable indicator of hypercarbia. A 53-year old male, ASA physical status II with mild hypertensive patient underwent primary repair because of rotator cuff tear of the shoulder. Anesthesia was induced with thiopental-succinylcholine and maintained with pancuronium- Halothane-N2O-O2 in a semiclosed circle system. We report occurrence of hypercarbia due to replacement with an incorrect unidirectional valve which is too small to function properly.