Airway Suctioning Research Articles

Effect of Endotracheal Suctioning with and without Normal Saline on Hemodynamic and Respiratory Parameters in Patients Undergoing Mechanical Ventilation in ICU of Hospitals Supervised by Guilan University of Medical Sciences

Airway suction is one of the most popular methods for drainage airways in patients with artificial airway; thus, correct suction of airways is important. Hence, the purpose of this study is to determine the effects of suction methods with and without normal saline on hemodynamic and respiratory patients. This randomized crossover clinical trial was conducted on two groups consisting of 37 mechanically ventilated patients by suctioning with and without normal saline. After at least 2 hours, the second stage was conducted and the patients were displaced in groups A and B. respiratory and hemodynamic parameters were measured at different intervals. The average age of patients was 21.8 ± 51.2; in terms of consciousness, 70% of patients were Sedate. Systolic blood pressure (P = 0.20), diastolic blood pressure (P <0.0001), average arterial pressure (P <0.0001) and heart rate (P <0.0001) increased over time immediately after the suction and then declined; in approximately 5 minutes after suction, it approached its baseline. This difference was significant in other cases except for systolic blood pressure. The mean respiratory rate, mean airway pressure, mean oxygen-saturated haemoglobin, mean end-tidal carbon dioxide were similar in both suction groups with and without normal saline during different time steps and no significant differences were observed. As long as there is no sufficient evidence to use normal saline on endotracheal suctioning, this method is not recommended to be used routinely. It is recommended to substitute strategies such as airway hydration, adequate hydration of patients, early mobilization of patients and administration of mucolytic drugs.

Characteristics and Outcomes for Hospitalized Patients With Recurrent Clinical Deterioration and Repeat Medical Emergency Team Activation*

To describe the occurrence of recurrent clinical deterioration and repeat medical emergency team activation and assess its effect on processes and outcomes of care. Retrospective cohort study. Two community hospitals and two tertiary care hospitals, Alberta, Canada. Consecutive hospitalized adult patients with sudden clinical deterioration and medical emergency team activation without admission to ICU. None. We compared ICU admission rates (admissions > 2 hr following index medical emergency team), hospital length of stay, and hospital mortality for a cohort of 3,200 patients with and without recurrent clinical deterioration following medical emergency team activation adjusting for patient, provider, and hospital characteristics.The cohort consisted of 3,200 patients. Ten percent of patients (n = 337) experienced recurrent clinical deterioration and repeat medical emergency team activation during their hospital stay. Patients more likely to experience recurrent clinical deterioration and repeat medical emergency team activation included those with chronic liver disease (odds ratio, 1.75; 95% CI, 1.14-2.69) or who received airway suctioning (odds ratio, 1.66; 95% CI, 1.23-2.25), noninvasive mechanical ventilation (odds ratio, 1.67; 95% CI, 0.94-2.94), or central IV catheter insertion (odds ratio, 1.81; 95% CI, 1.02-3.21) during the index medical emergency team activation. Patients with recurrent clinical deterioration were more likely than patients without recurrent clinical deterioration to be subsequently admitted to ICU (43% vs 13%; odds ratio, 6.11; 95% CI, 4.67-8.00; p < 0.01), to have longer lengths of hospital stay (median, 31 d vs 13 d; p < 0.01), and to die during their hospital stay (34% vs 23%; odds ratio, 1.98; 95% CI, 1.47-2.67; p < 0.01). Recurrent clinical deterioration and repeat medical emergency team activation are common and associated with increased risk of subsequent ICU admission, increased length of hospital stay, and increased hospital mortality. It may be possible to identify patients at risk of recurrent clinical deterioration following medical emergency team activation and target interventions to improve patient care.

Management of the artificial airway.

Management of the artificial airway includes securing the tube to prevent dislodgement or migration as well as removal of secretions. Preventive measures include adequate humidification and appropriate airway suctioning. Monitoring airway patency and removing obstruction are potentially life-saving components of airway management. Cuff pressure management is important for preventing aspiration and mucosal damage as well as assuring adequate ventilation. A number of new monitoring techniques have been introduced, and automated cuff pressure control is becoming more common. The respiratory therapist should be adept with all these devices and understand the appropriate application and management.

The Process of Prehospital Airway Management

Endotracheal intubation success rates in the prehospital setting are variable. Our objective was to describe the challenges encountered and corrective actions taken during the process of endotracheal intubation by paramedics. Analysis of prehospital airway management using a prospective registry that was linked to an emergency medical services administrative database. Emergency medical services system serving King County, Washington, 2006-2011. Paramedics in this system have the capability to administer neuromuscular blocking agents to facilitate intubation (i.e., rapid sequence intubation). A total of 7,523 patients more than 12 years old in whom paramedics attempted prehospital endotracheal intubation. None. An intubation attempt was defined as the introduction of the laryngoscope into the patient's mouth, and the attempt concluded when the laryngoscope was removed from the mouth. Endotracheal intubation was successful on the first attempt in 77% and ultimately successful in 99% of patients (7,433 of 7,523). Paramedics used a rapid sequence intubation strategy on 54% of first attempts. Among the subset with a failed first attempt (n = 1,715), bodily fluids obstructing the laryngeal view (50%), obesity (28%), patient positioning (17%), and facial or spinal trauma (6%) were identified as challenges to intubation. A variety of adjustments were made to achieve intubation success, including upper airway suctioning (used in 43% of attempts resulting in success), patient repositioning (38%), rescue bougie use (19%), operator change (16%), and rescue rapid sequence intubation (6%). Surgical cricothyrotomy (0.4%, n = 27) and bag-valve-mask ventilation (0.8%, n = 60) were rarely performed by paramedics as final rescue airway strategies. Airway management in the prehospital setting has substantial challenges. Success can require a collection of adjustments that involve equipment, personnel, and medication often in a simultaneous fashion.

Perception of artificial airway suction from patients and nurses: a literature review

Objective To study the perception of patients and nurses for the artificial airway suction,in order to provide theoretical reference for building the artificial airway suction clinical practice guidelines.Methods CNKI,Wanfang,VIP,Pubmed,Science direct databases were searched for papers of patients and/or nurses' perception over the limited period of 2005 to 2013.The retrieved papers were analyzed.Results Nineteen eligible papers were identified.Extract relevant contents found the majority of patients retained the memory of that airway suction,mainly for pain,choking,suffocation,and eager to get the relevant knowledge and information.There were few researches on nurses' subjective feeling about airway suction.Conclusion We should pay attention to the perception of patients,while strengthening the research on nurses' perception of artificial airway suction and improve communication with patients,in order to relieve their discomfort experience,and could be helpful for the building of airway suction clinical practice guidelines. Key words: Artificial airway suctioning; Subjective feelings; At home and abroad; Literature review

Open versus closed suctioning of artificial airways in critically ill adult patients: An evidence review

Suctioning of a tracheal tube is a frequent and integral activity to airway management in adult intensive care. Airway suctioning can have deleterious effects on physiological function. Both Open Suction Systems (OSS) and Closed Suction Systems (CSS) have been used in critical care settings. The objective of this review was to determine which system (OSS or CSS) has an evidence based advantage for clinical practice. A systematic literature review was conducted. Medline, Ovid SP and PubMed databases were searched using the keywords suction, critical/intensive care, open suction system and closed suction system. Search filters were: human, adult, english language and published between 2006 and June 2012. Two reviewers extracted data using a standardised tool which incorporated the Scottish Intercollegiate Guideline Network quality criteria. Eleven articles met the inclusion criteria, two meta-analysis, four systematic reviews, two randomised control trials, one interrupted time series, an observational study, and a convenience sample review. The evidence favoured OSS for tube colonisation and costs for <4 days ventilation; whereas CSS was better regarding end expiratory lung volume losses and for ventilation costs >4 days. There was no difference between systems for oxygenation, haemodynamics, sputum clearance, iatrogenic pneumonia, environmental contamination, patient length of mechanical ventilated days, length of stay, or mortality. Current evidence is limited by heterogeneity of study design and volume of studies; making it difficult to advocate for one system over the other. More research is required to inform and support clinical practice.

Effects of manually-assisted cough combined with postural drainage, saline instillation and airway suctioning in critically-ill patients during high-frequency oscillatory ventilation: a prospective observational single centre trial

Background: Chest physiotherapy may aid sputum clearance during conventional ventilation. However, the role of chest physiotherapy during high-frequency oscillatory ventilation (HFOV) is unclear. This study aimed to determine the effects manually-assisted cough (MAC), postural drainage, saline instillation and airway suction during HFOV. Methods: This was an observational study of a chest physiotherapy intervention in adult critically ill patients during HFOV. Measures included gas exchange, HFOV and haemodynamic variables 1 h before, immediately before, and 15 min, 1 h, 6 h and 12 h after intervention. Wet weight of airway secretions was also measured. Linear mixed modelling compared pre-intervention gas exchange, HFOV and haemodynamic variables with the four specified time-points after intervention. Results: Seventeen adults (ten females) with moderate to severe respiratory failure were studied (age, 49 years SD 14; Acute Physiology and Chronic Health Evaluation II score (APACHE II score) 21 SD 6; PaO2/FiO2 of 139 mmHg SD 51). There was a statistically, although not clinically significant reduction in PaO2/FiO2 for up to 1 h after intervention, but no significant changes in oxygenation index, PaCO2, pH, or haemodynamic parameters up to 12 h after intervention. A reduction in delta pressure (ΔPaw) at 15 min (p < 0.05) and 1 h (p < 0.05) post intervention was not correlated with sputum wet weight. Conclusions: MAC, postural drainage, saline instillation and airway suctioning during HFOV in critically ill patients was well tolerated with no clinically significant effect on arterial blood gases or haemodynamics. ΔPaw decreased for up to 1 h after intervention, but was not explained by the weight of sputum removed.

Quantifying the risk of respiratory infection in healthcare workers performing high-risk procedures.

This study determined the risk of respiratory infection associated with high-risk procedures (HRPs) performed by healthcare workers (HCWs) in high-risk settings. We prospectively studied 481 hospital HCWs in China, documented risk factors for infection, including performing HRPs, measured new infections, and analysed whether HRPs predicted infection. Infection outcomes were clinical respiratory infection (CRI), laboratory-confirmed viral or bacterial infection, and an influenza infection. About 12% (56/481) of the study participants performed at least one HRP, the most common being airway suctioning (7·7%, 37/481). HCWs who performed a HRP were at significantly higher risk of developing CRI and laboratory-confirmed infection [adjusted relative risk 2·9, 95% confidence interval (CI) 1·42-5·87 and 2·9, 95% CI 1·37-6·22, respectively]. Performing a HRP resulted in a threefold increase in the risk of respiratory infections. This is the first time the risk has been prospectively quantified in HCWs, providing data to inform occupational health and safety policies.

Acute effects of physiotherapeutic respiratory maneuvers in critically ill patients with craniocerebral trauma

OBJECTIVE:To evaluate the effects of physiotherapeutic respiratory maneuvers on cerebral and cardiovascular hemodynamics and blood gas variables.METHOD:A descriptive, longitudinal, prospective, nonrandomized clinical trial that included 20 critical patients with severe craniocerebral trauma who were receiving mechanical ventilation and who were admitted to the intensive care unit. Each patient was subjected to the physiotherapeutic maneuvers of vibrocompression and increased manual expiratory flow (5 minutes on each hemithorax), along with subsequent airway suctioning with prior instillation of saline solution, hyperinflation and hyperoxygenation. Variables related to cardiovascular and cerebral hemodynamics and blood gas variables were recorded after each vibrocompression, increased manual expiratory flow and airway suctioning maneuver and 10 minutes after the end of airway suctioning.RESULTS:The hemodynamic and blood gas variables were maintained during vibrocompression and increased manual expiratory flow maneuvers; however, there were increases in mean arterial pressure, intracranial pressure, heart rate, pulmonary arterial pressure and pulmonary capillary pressure during airway suctioning. All of the values returned to baseline 10 minutes after the end of airway suctioning.CONCLUSION:Respiratory physiotherapy can be safely performed on patients with severe craniocerebral trauma. Additional caution must be taken when performing airway suctioning because this technique alters cerebral and cardiovascular hemodynamics, even in sedated and paralyzed patients.

Uso de máscara laríngea en un lactante con estenosis subglótica. Reporte de caso y revisión de la literatura

The laryngeal mask has become an alternative to manage the pediatric airway. This is a clinical case of an infant with VACTERL association requiring anesthesia for tracheoesophageal fistula closure and esophageal anastomosis; the infant was successfully managed with laryngeal mask upon failed intubation.The use of the laryngeal mask is an option for the management of the airway in neonates and infants with craniofacial malformations, either alone or as an adjuvant for tracheal intubation and also in neonates with normal airway for complex surgeries, including heart surgery. The evidence points to the use of second-generation devices that allow for an improved airway seal and suction of the GI tract (Proseal® or Supreme®). It is also an alternate device during neonatal resuscitation in patients over 2000 g that cannot be properly managed with a face mask or intubated.

The use of laryngeal mask in an infant with subglottic stenosis—Case report and literature review

The laryngeal mask has become an alternative to manage the pediatric airway. This is a clinical case of an infant with VACTERL association requiring anesthesia for tracheoesophageal fistula closure and esophageal anastomosis; the infant was successfully managed with laryngeal mask upon failed intubation.The use of the laryngeal mask is an option for the management of the airway in neonates and infants with craniofacial malformations, either alone or as an adjuvant for tracheal intubation and also in neonates with normal airway for complex surgeries, including heart surgery. The evidence points to the use of second-generation devices that allow for an improved airway seal and suction of the GI tract (Proseal® or Supreme®). It is also an alternate device during neonatal resuscitation in patients over 2000g that cannot be properly managed with a face mask or intubated.

Practice patterns of physiotherapists in neonatal intensive care units: A national survey

Objective:To determine practice pattern of physiotherapists in the neonatal intensive care units (ICUs) in India with regards to cardiopulmonary and neuromuscular physiotherapy.Materials and Methods:A cross-sectional survey was conducted across India, in which 285 questionnaires were sent via e-mail to physiotherapists working in neonatal intensive care units.Results:A total of 139 completed questionnaires were returned with a response rate of 48.7%, with a majority of responses from Karnataka, Maharashtra and Gujarat. More than 90% of physiotherapists performed chest physiotherapy in neonatal ICUs. Chest physiotherapy assessment predominantly focused on vital parameter assessment (86%) and in treatment predominantly focused on percussion (74.1%), vibration (75.5%), chest manipulation (73.3%), postural drainage (67.6%) and suction (65.4%). In neuromuscular physiotherapy more than 60% of physiotherapists used positioning, and parent education, whereas more than 45% focused on passive range of motion exercise and therapeutic handling.Conclusion:The practice pattern of physiotherapists for neonates in neonatal intensive care units involves both chest physiotherapy as well neuromuscular physiotherapy. Chest physiotherapy assessment focused mainly on vital parameter assessment (heart rate, respiratory rate and partial pressure of oxygen saturation SpO2). Treatment focused on airway clearance techniques including percussion, vibration, postural drainage and airway suction. In neuromuscular physiotherapy most physiotherapists focused on parent education and passive range of motion exercise, therapeutic handling, as well as positioning.

I Recomendação brasileira de fisioterapia respiratória em unidade de terapia intensiva pediátrica e neonatal

Developing guidelines for the role of the physiotherapist in neonatal and pediatric intensive care units is essential because these professionals are responsible for the rehabilitation of critically ill patients. Rehabilitation includes the evaluation and prevention of functional kinetic alterations, application of treatment interventions (respiratory and/or motor physiotherapy), control and application of medical gases, care of mechanical ventilation, weaning and extubation, tracheal gas insufflation, inflation/deflation of the endotracheal cuff protocol, and surfactant application, aiming to allow patients to have a full recovery and return to their functional activities. In this article, we present guidelines that are intended to guide the physiotherapist in some of the prevention/treatment interventions in respiratory therapy (airway clearance, lung expansion, position in bed, airway suction, drug inhalation, and cough assist), which help in the rehabilitation process of newborns and children in intensive care units during mechanical ventilation and up to 12 hours following extubation.

Chest physical therapy is effective in reducing the clinical score in bronchiolitis: randomized controlled trial

To evaluate the effectiveness of chest physical therapy (CP) in reducing the clinical score in infants with acute viral bronchiolitis (AVB). Randomized controlled trial of 30 previously healthy infants (mean age 4.08 SD 3.0 months) with AVB and positive for respiratory syncytial virus (RSV), evaluated at three moments: at admission, then at 48 and 72 hours after admission. The procedures were conducted by blinded assessors to each of three groups: G1 - new Chest Physical therapy- nCPT (Prolonged slow expiration - PSE and Clearance rhinopharyngeal retrograde - CRR), G2 - conventional Chest Physical therapy- cCPT (modified postural drainage, expiratory compression, vibration and percussion) and G3 - aspiration of the upper airways. The outcomes of interest were the Wang's clinical score (CS) and its components: Retractions (RE), Respiratory Rate (RR), Wheezing (WH) and General Conditions (GC). The CS on admission was reduced in G1 (7.0-4.0) and G2 (7.5-5.5) but was unchanged in G3 (7.5-7.0). We observed a change 48 hours after hospitalization in G1 (5.5-3.0) and G2 (4.0-2.0) and in 72 hours, there was a change in G1 (2.0-1.0). The CP was effective in reducing the CS in infants with AVB compared with upper airway suction only. After 48 hours of admission, both techniques were effective and nCPT techniques were also effective in the 72 hours after hospitalization compared with cCPT techniques.

Effect of a Lung Protective Strategy for Organ Donors on Eligibility and Availability of Lungs for Transplantation

Mascia, Luciana*; Pasero, Daniela*; Slutsky, Arthur S.†; Arguis, M. Jose‡; Berardino, Maurizio§; Grasso, Salvatore∥; Munari, Marina¶; Boifava, Silvia#; Cornara, Giuseppe**; Della Corte, Francesco††; Vivaldi, Nicoletta‡‡; Malacarne, Paolo§§; Del Gaudio, Paolo∥∥; Livigni, Sergio¶¶; Zavala, Elisabeth‡; Filippini, Claudia*; Martin, Erica L.*; Donadio, Pier Paolo*; Mastromauro, Ilaria*; Ranieri, V. Marco* Author Information

The Effect of Computer Based Learning (CBL) Regarding Endotracheal Airway Suctioning on Knowledge and Skill Retention of Third Year Pediatric Nursing Students

Endotracheal airway suctioning (ETS) is one of the important pediatric nursing skills that should be used only after careful assessment. High qualified pediatric nursing care requires interesting in clinical skill education and seeking innovative learning methods. Reviewed studies comparing the effectiveness of CBL with traditional methods reported lack of studies that tested knowledge or skill retention. This quasi-experimental study evaluated the effect of CBL regarding ETS on knowledge and skill retention of third year pediatric nursing students. A total 120 students were divided into experimental and control groups. The experimental group was taught used an interactive, multimedia, self-directed computer-based learning module. The control group was taught used face to face lecture and demonstration in a pediatric clinical skills laboratory. Data were collected using knowledge test at four time points and at three time points using ETS performance checklist. The study revealed that CBL method produce significant cognitive gains and higher skill performance scores for the experimental students at immediate follow up but the retained knowledge was almost similar in both groups at 2 weeks follow up. The experimental group achieved significant higher differences emerging in retained knowledge at the 6 week follow up and in retained skill performance at 2 & 6weeksfollow ups. The findings indicated that CBL was an effective strategy for teaching both knowledge and practice. It also produced better knowledge and skill retention than in case of traditional learning method.

Computerised lung sound monitoring to assess effectiveness of chest physiotherapy and secretion removal: a feasibility study

ObjectivesTo explore the feasibility of computerised lung sound monitoring to evaluate secretion removal in intubated and mechanically ventilated adult patients. DesignBefore and after observational investigation. SettingIntensive care unit. ParticipantsFifteen intubated and mechanically ventilated adult patients receiving chest physiotherapy. InterventionsChest physiotherapy included combinations of standard closed airway suctioning, saline lavage, postural drainage, chest wall vibrations, manual-assisted cough and/or lung hyperinflation, dependent upon clinical indications. Main outcome measuresLung sound amplitude at peak inspiration was assessed using computerised lung sound monitoring. Measurements were performed immediately before and after chest physiotherapy. Data are reported as mean [standard deviation (SD)], mean difference and 95% confidence intervals (CI). Significance testing was not performed due to the small sample size and the exploratory nature of the study. ResultsFifteen patients were included in the study [11 males, four females, mean age 65 (SD 14) years]. The mean total lung sound amplitude at peak inspiration decreased two-fold from 38 (SD 59) units before treatment to 17 (SD 19) units after treatment (mean difference 22, 95% CI of difference −3 to 46). The mean total lung sound amplitude from the lungs of patients with a large amount of secretions (n=9) was over four times ‘louder’ than the lungs of patients with a moderate or small amount of secretions (n=6) [56 (SD 72) units vs 12 (13) units, respectively; mean difference −44, 95% CI of difference −100 to 11]. The mean total lung sound amplitude decreased in the group of ‘loud’ right and left lungs (n=15) from 37 (SD 36) units before treatment to 15 (SD 13) units after treatment (mean difference 22, 95% CI of difference 6 to 38). ConclusionComputerised lung sound monitoring in this small group of patients demonstrated a two-fold decrease in lung sound amplitude following chest physiotherapy. Subgroup analysis also demonstrated decreasing trends in lung sound amplitude in the group of ‘loud’ lungs following chest physiotherapy. Due to the small sample size and large SDs with high variability in the lung sound amplitude measurements, significance testing was not reported. Further investigation is needed in a larger sample of patients with more accurate measurement of sputum wet weight in order to distinguish between secretion-related effects and changes due to other factors such as airflow rate and pattern.

Airway Suctioning and Clearance Techniques for Respiratory Disorders

Airway Suctioning and Clearance Techniques for Respiratory Disorders

Endotracheal and upper airways suctioning: changes in newborns’ physiological parameters

This study investigated which physiological parameters change when endotracheal and upper airway suctioning is performed immediately before, immediately after and five minutes after this procedure is performed in newborns hospitalized in a Neonatal Intensive Care Unit (NICU). This is a quantitative and longitudinal study, before and after type, performed in the NICU of a public institution in the city of Fortaleza, CE, Brazil. The sample was composed of 104 newborns using oxigenotherapy and who needed endotracheal and upper airway suctioning. The results showed significant alterations in respiratory and heart rates (p<0.05) in neonates using Oxyhood and nasal CPAP while the pulse significantly changed (p<0.05) in newborns placed in oxyhood, using nasal CPAP and Mechanical Ventilation; oxygen saturation was the only parameter that did not alter significantly. We propose that nurses develop non-pharmacological interventions to reduce potential alterations caused in newborns' physiological parameters due to this procedure.

Awake fibreoptic intubation with high risk of aspiration

Following a recent case of pulmonary aspiration of gastric contents, we seek guidance on the timing of inflation of the tracheal tube cuff, and the best method of assessing adequate seal, following awake fibreoptic intubation in patients at risk of aspiration. Our patient had severe gastric distension that we were unable to decompress; despite several attempts, we were unable to pass a gastric tube. Faced with an unknown airway, we performed an uncomplicated awake fibreoptic intubation. Due to the aspiration risk, we inflated the cuff before general anaesthesia, using a syringe, with manual palpation of the pilot balloon. As we induced general anaesthesia, a large quantity of fluid flowed from the stomach, some of which passed beyond the cuff to soil the airway. We added more air to the cuff to improve the seal, and carried out airway suctioning, but the patient required a 7-day ICU stay postoperatively. We are unaware of any advice about the optimal timing of cuff inflation in patients at risk of aspiration following awake fibreoptic intubation. Inflating the cuff before induction of general anaesthesia risks a stimulatory physiological response that could cause harm, e.g. in trauma, head injury or ischaemic heart disease. Waiting until after induction risks missing any cuff damage incurred on insertion, and risks aspiration in the event of regurgitation. Application of cricoid pressure may provide some protection against aspiration, but may deform the trachea [1] leading to a reduction in cuff pressure on its removal and inadequate seal with a risk of aspiration. The NAP4 project [2] (in which this case was included) recommends that ‘once placed a tracheal tube offers the highest protection against aspiration’, but does not comment on how best to confirm adequacy of the cuff’s seal. One could ask the patient to breathe against a partially closed adjustable pressure-limiting valve and assess for a leak, but we feel this may be poorly tolerated and unreliable. A manometer could be used to assess the pressure, but we could find no clear target value in the literature. An inflated cuff may also cause discomfort. In our experience, the cuff should only be inflated immediately before induction of anaesthesia. Awake fibreoptic intubation has been described as a suitable technique for patients at high risk of aspiration [3] and appears in some algorithms designed for use in situations where aspiration is a possibility [4]. We would be grateful for the expert opinions of anaesthetists with experience in using this technique to manage patients at high risk of aspiration as to when the cuff should be inflated and, if inflated before general anaesthesia, whether the adequacy of the seal can safely be tested.