Clinical Update. Non-invasive Positive Pressure Ventilation in children

Transcription

1 DOI / Kundan Mittal *, N Rungta **, Vinayak Patki ***, H K Aggarwal**** * Senior Professor Pediatrics, ****Senior Professor & Head of Unit Medicine and Nephrologist,Pt B D Sharma, PGIMS, Rohtak, Haryana, India. **Head, Critical Care Medicine, JNU Institute of Medical sciences and Research Center, Jaipur, Rajasthan, India. ***Chief, Advanced Pediatric Critical Care Centre, Wanless Hospital, Miraj, Maharashtra, India. Received: 12-Jun-18/Accepted: 27-Jun-18/Published online: 30-Jun-18 ABSTRACT Respiratory problems are common in pediatric population and need advanced respiratory support in intensive care for various reasons. Mechanical ventilation is most important mode of therapy/support of modern era in intensive care units. This can be provided invasively or non-invasively, in the hospital and outside the hospital settings. Non-invasive ventilation has many advantages over invasive with some limitations. Pressure applied throughout respiratory cycle is known as continuous distending pressure and has many ways of application. Recently average volume assured pressure support and heated humidified high flow nasal canula have been introduced as method of non-invasive positive pressure ventilation. Non-invasive positive pressure ventilation is better suited in hypercapnic respiratory failure. Key words: NIV, CDP, CPAP, PEEP, Resp. Failure Continuous Distending Pressure 1-3 Continuous distending pressure (CDP) is the pressure applied throughout the respiratory cycle. It includes continuous positive airway pressure (CPAP): a mode of non-invasive positive pressure ventilation, positive end expiratory pressure (PEEP); a mode of invasive positive pressure ventilation, Heated Humidified High flow nasal canula (H3FNC) and negative pressure ventilation. The main function of CDP is to maintain lung volume (FRC: functional residual capacity), increase in mean airway pressure (MAP) and supporting the airway thus increasing surface area for improving alveolar ventilation, diffusion and preventing ventilationperfusion mismatch leading to improvement in oxygenation and helping in removal of carbon dioxide. CDP also helps in stabilizing the chest wall, improves diaphragm activity, lung mechanics, alveolar curvature and compliance, decreases upper airway occlusion, resistance and work of breathing. Excessive CDP leads to pulmonary over-distension contributing to air-leak syndrome, increase in intrathoracic pressure and pulmonary vascular resistance, impairing lung mechanics and compliane. Correspondence: Dr. Kundan Mittal, Senior Professor Pediatrics, Pt B D Sharma, PGIMS, Rohtak Haryana, India, Phone , -kundanmittal@gmail.com Non-invasive Positive Pressure Ventilation (BIPAP) Ventilating a child without invasive methods mean no intubation and or tracheostomy. Non-invasive positive pressure ventilation (NIPPV) can augment both ventilation and oxygenation. Modes Both pressure and volume preset mode can be used depending upon the availability and experience. Volume cycled machine are better in children with changing respiratory mechanics. Assist Mode: Patient triggers the breath and supported by machine. Physician must set targeted pressure or volume, I: E ratio or inspiratory time and inspiratory trigger sensitivity. Assist-control mode: Patient triggers the breath and between when patient is apnoeic will have controlled ventilation. Inspiration cycle is determined by operator. Controlled rate is less than patient respiratory rate and inspiration is time cycled. Controlled Mode: Everything is controlled by machine and all work is done by ventilator. Patient respiratory centre is controlled by machine. Spontaneous: Patient triggers rate and depth of breathing and inspiratory and expiratory pressure cycle. Risk of respiratory acidosis if breathing rate is low. This is similar to pressure support ventilation. 98

2 Spontaneous/timed: Machine breath are delivered at set frequency for patient who are intermittently apnoeic. Physician sets the rate, inspiratory time, IPAP and EPAP. Timed positive pressure: Breaths are delivered at set frequency/time but patient can breathe spontaneously. Average volume and assured pressure support (AVAPS): AVPAS uses fixed tidal volume that automatically adjusts to patient needs. Continuous positive airway pressure (CPAP): Continuous pressure applied throughout the cycle specially end of expiration. Patient breathes spontaneously at baseline pressure and controls rate and depth. Flow and pressure transducers respond to patient efforts and maintain the stable pressure. Rise time: Some machine allows to set rise time. Four types of ventilator can be used to deliver NIPPV Critical care ventilator: These are used in intensive care setting. These ventilators have separate inspiratory and expiratory limb with active exhalation valve. Pressure support is difference between PIP -PEEP Bilevel ventilator: This ventilator has only inspiratory limb and passive exhalation port. IPAP and EPAP are adjusted. IPAP is EPAP plus pressure support. Some of bi-level ventilators adjust inspiratory trigger and expiratory cycle by tracking patient inspiratory and expiratory flow. Patient initiates breath and there is no set rate. Intermediate ventilator: These types of ventilators have single inspiratory limb with passive exhalation port or active exhalation valve. Stand-alone CPAP: Suited for hypoxemic respiratory failure when respiratory drive and muscles are well. Newer Mode: Pressure targeted assist control, Proportional Assist Ventilation, Neurallyadjusted ventilatory assistance, Average volume assured pressure support (automatically adapts pressure support as per demand). Contraindications Hemodynamically unstable child Unconscious child Unable to protect airway Severe hypoxemia Excessive secretions Respiratory arrest or cardiac arrest Progressive respiratory failure Inability to clear the secretion or risk of aspiration Mask issues Uncooperative child Non-respiratory organ failure Vomiting Undrained pneumothorax Bowel obstruction Moribund child Severe comorbidity Indications Hyaline membrane disease Upper airway obstruction Bronchiolitis Asthma: Combination of higher IPAP and low EPAP are more effective. It improves ventilation and oxygenation, FEV1 and PEFR rapidly. Pneumonia Acute respiratory distress syndrome Progressive neuromuscular disease Central hypoventilation Pre-oxygenation before intubation: It improves oxygen saturation during & after intubation and decrease the episodes of desaturation. Obstructive sleep apnoea Acute cardiogenic pulmonary oedema: CPAP alone improves oxygenation, FRC and decreases the intubation rate. Extubation failure Facilitate weaning Do not intubate status: NIPPV role in palliative care is controversial. 99

3 Consequences of NIPPV Alveolar recruitment Increased functional residual capacity Increased PaO2 and decreased PaCo2 Respiratory muscle unloading and improvement Lung volume improvement Improved quality of life Interface Quality of interface: Light weight, transparent, leak free (proper fitting), non-traumatic, stable, longlasting, non-allergic, low cost, minimal dead space, and less resistance to airflow, easy to clean Types of Interface Nasal mask: Easy to apply, less dead space, easy to clear secretions, less claustrophobic, but risk of mouth leak, nasal dryness, difficult in case of nasal obstruction Oro-nasal mask: Less mouth leak, increased dead space, claustrophobic, better for mouth breather, difficulty in eating and speaking Nasal pillows: Simple and easy to fit, mouth leak present, able to speak Mouth piece: Less dead space, nasal leak present Total face mask: Comfortable, easy to use in children with facial irregularities, increased dead space, unable to deliver nebulised medicine, better for mouth breather, no pressure on nasal bridge Helmet: Easy to use but poor patient-ventilator synchrony For CPAP exclusively: Face mask, single nasal prong or short-binasal prong, long nasopharyngeal canula and head box Complications Associated with invasive procedures are; Intubation may result trauma to oropharyngeal structures, oesophagus, airway, barotrauma, hypotension, cardiac arrhythmias, irritation, ciliary dysfunction, suction injury, hypersecretion, patient discomfort requires sedation, analgesia and neuro-paralytic agents and their complications, bacterial colonisation, sinusitis, pneumonia, Tracheostomy tube placement may also result bleeding, stomal infection, mediastinitis, acute injury to surrounding structures, prolonging nursing care Poor communication, hoarseness of voice, tracheal stenosis, airway obstruction, anxiety NIV can prevent many of above complications, patient is able to communicate, eat and drink, airway defence mechanism is also protected. Setting of Ventilator Define goal whether problem is oxygenation or ventilation or both Inform care giver and or child if able to understand about the procedure In infants use CPAP only and titre the response Children 1-2year: IPAP 8cm, EPAP 4cm (minimum difference should be 4cm). EPAP can be increased up to 8-12cm Children >2years: IPAP 10cm, EPAP 5cm If problem is oxygenation increase EPAP by 2cm and IPAP in same value If problem is of ventilation (CO2) increase IPAP by 2cm and monitor the response One can start with high pressure and come down slowly known as high-low approach or vice-versa Reassess the child after one hour and if no response change accordingly Check arterial blood gas after one hour Check leaks Monitoring on NIPPV Patient comfort Vital signs Work of breathing and coordination between patient and ventilator Delivered tidal volume Accessory muscle use Oxygen saturation Arterial blood gas (one to two hourly) Neurological status Mask leak and excessive tightness Hydration and nutrition 100

4 Pressure sores Patient ventilator asynchrony Expected results of changing Non-invasive ventilator setting Setting Adjustment Expected results IPAP Increase TV, MV, PCO 2 Decrease TV, MV, PCO 2 EPAP Increase FRC, PaO 2, TV Decrease FRC, PaO 2, TV, PCO 2 Possible rebreathing of CO 2 if EPAP<4 FiO 2 Increase PaO 2, Flow >15L/min will affect triggering Decrease PaO 2 Rate Increase PCO 2, MV Decrease MV, PCO 2 EPAP: This is the pressure in expiration when patient breathe out. It keeps alveoli open, recruit alveoli, improves oxygenation, prevents rebreathing, decreases inspiratory work load and increases lung volume (FRC). IPAP: This is pressure on inspiration. Machine senses the patient inspiratory efforts and blows the air/oxygen. IPAP provides inspiratory support, tidal volume and removes carbon dioxide. CPAP: is useful only in hypoxemic child while BiPAP in both type of respiratory insufficiency. Average volume-assured pressure support (AVAPS) is similar to BiPAP; the inherent difference is the clinician-defined parameters. IPAP range is selected to target a goal tidal volume. Therefore, as patient effort varies, the ventilator will either up titrate IPAP to increase, or down titrate to decrease to the targeted inhaled tidal volume or minute ventilation. Pressure Support: This is the difference between IPAP and EPAP and improves patient efforts. Contraindications Pneumothorax CO2 > 48mmHg Facial trauma Heated Humidified High Flow Nasal Cannula (H3FNC) 4-6 Heated Humidified High Flow Nasal Cannula (H3FNC) therapy is a simple to use system that delivers warm, moist (>99% of relative humidity) medical gas at different flow rates (higher than patient inspiratory flow rate) with adjusted FiO 2 delivering higher oxygen concentration that generate positive airway pressure. When used at flow rates of 1-2 L/kg/min., this technique is associated with washout of nasopharyngeal dead space (3mL/kg in neonates), reduction of the inhalation resistance through the nasopharyngeal airway, improvement in pulmonary compliance, bronchoconstriction and elasticity (because of heated and humidified air), lung mucociliary clearance, higher oxygen concentration (higher placement of nasal canula preventing dilutional effect and wash out of carbon dioxide) minute ventilation, decreases metabolic rate, and variable degree of distending pressure for alveolar recruitment (Pressure = Flow x Resistance). Highflow system obtains better oxygen concentration than low-flow system. High-flow rate is usually 2-8L/min in infants, 5-20L/min in children and 6-40L/min in adults. Essential to Know about H3FNC Nasal cannula selection depends on size of nostrils and should not cover more than 50% Monitor child respiratory rate, saturation and heart rate Target oxygen saturation >92% Instruction for use Infants: 1 L/kg/min up to 2 L/kg/min Children 1 L/kg/min up to 1.5 L/kg/min (max L/min) Adults: 20 L/min up to L/min Keep initial FiO2 40% and document flow rate Respiratory Paediatric Early Warning Score (PEWS) should be recorded at 0, 30, 60minute and later hourly observation should be done If child is stable start feeding after 4hours Oxygen should be weaned (5-10% every 4hr) before flow (FiO 2 is 25% start low flow oxygen) 101

5 End Expiratory Pressure Generated by H3FNC Flow: Pressure generation depends on weight/size, flow rate, diameter of canula compared to nares, and position of mouth. 2L 2cm (2-2) 3L 3cm (2-5) 4 5cm (3-7) 5 5cm (5-8) 6L 7cm (5-10) 7L 8cm (6-13) 8L 9cm (6-15) Disadvantages: Rhinorrhoea, pneumothorax, nasal trauma, not useful in type II respiratory failure Contraindications of H3FNC Nasal obstruction Gastric distension Life threatening hypoxia / apnoea / haemodynamic instability Facial and chest trauma Poisoning Foreign body aspiration Pneumothorax Blood gas PCO 2 >48mmHg Decreased level of consciousness (LOC) Congenital heart disease Source of funding: Nil Conflict of interest: Nil References 1. Stefeno Nava, Francesco Fanfulla. Non-Invasive Artificial Ventilation. Verlag Italia: Springer; Antonio M. Esquinas. 2nd ed. Noninasive Mechanical Ventilation. Switzerland: Springer; Steven M Donn, Sunil K Sinha. 4th ed. Manual of Respiratory Care. Switzerland: Springer; Gonzalo H, Oriol R, Laura Colinas. High-flow nasal cannula support therapy: new insights and improving performance. Critical Care 2017; 21: Ke-Yun Chao, Yi-Ling Chen, Li-Yi Tsai Yu-Hsuan Chien, Shu-Chi Mu. The Role of Heated Humidified High-flow Nasal Cannula as Non-invasive Respiratory Support in Neonates. Pediatrics and Neonatology 2017;58: Masaji Nishimura. High-Flow Nasal Cannula Oxygen Therapy in Adults: Physiological Benefits, Indication, Clinical Benefits, and Adverse Effects. Respir Care 2016;61(4): How to cite this article: Mittal K, Rungta N, Patki V, Aggarwal HK. Clinical Update-. J Pediatr Crit Care 2018;5(3): How to cite this URL: Mittal K, Rungta N, Patki V, Aggarwal HK. Clinical Update-. J Pediatr Crit Care 2018;5(3): Available from: 102