The pressure applied within the cuirass acts uniformly over the thorax. Subsequently, lung expansion is also uniform ventilating all areas of the lungs. In positive pressure ventilation (PPV) the gas pushed into the lungs naturally follows the path of least resistance therefore ventilating the already well ventilated areas. Increase in pressures/volumes to aid ventilation of all areas of the lungs leads to barotrauma, volutrauma and possible development of a pnuemothorax. These complications, along with those of ventilator associated pneumonia, are of no relevance with BCV.
BCV in conjunction with PPV is used as an aid to weaning, to increase right ventricular function and aid in expansion of areas of collapse references 12, 13, 38, 40, 41, 55, 60.
- Acute Respiratory Failure
- Chronic Obstructive Pulmonary Disease (COPD)
- Neuromuscular (e.g. SMA, Duchennes etc)
- Head and Spinal Injuries
- Problems with Weaning from PPV
- Ventilation during anaesthesia in Ear Nose and Throat (ENT) Procedures
- Cystic Fibrosis (CF), and those who require physiotherapy
- Aids Related Lung Disease
- Asthma
- Ventilation post-operation Eg. post-coronary bypass, Fontan, Fallot, post-pneumonectomy
Used in conditions with increased work of breathing, small airways disease, V/Q mismatching and those infants who may tire easily post extubation.
This mode of support can be easily adjusted/manipulated to suit the individual patients - requirements. Start your CNEP roughly 2cms H2O more than you would CPAP. This level is then adjusted until the increase work of breathing decreases. This will be noted with decreased recession, use of expiratory muscles, metabolic acidosis, stable or falling CO2 and improved oxygenation.
The air within the cuirass can cause the infants to be at risk of temperature loss. It is advisable to dress them in pyjamas or warm clothes, without buttons as these can affect the seal on the cuirass. Or place them under a radiant heater
Once a suitable level of CNEP is found and the patient is n the recovery phase of their illness weaning from CNEP can be initiated by bringing down the level of CNEP and then once at an expectable level taking the patient off for controlled periods. These are gradual lengthened to suit the patient.
CNEP helps improve right ventricular function, especially when used in conjunction to PPV. References: 10, 11, 12, 13, 15.
Control Mode
This mode provides full control over the patient' s respiration
- Mandatory respiratory rate is set and delivered; patients do not fight against the mandatory breaths as the Hayek RTX uses their own respiratory muscles to breath. This is a unique function of the Hayek RTX as it mimics physiological respiration.
- Controls both inspiratory and expiratory phases and you have control over the I:E ratio
- Commence rate at 2 above their own current spontaneous rate, then can slowly decrease the rate as patients breathing controlled by Hayek RTX
- If PaCO2 increases alter I:E ratio to 1:1.2 - 1:1.5
- At frequency' s over 60 the inspiratory pressure and the expiratory pressures should set at the same figures i.e. -15 and +15
- At frequencies of 240-1200cpm you can only preset frequency and inspiratory pressure parameters
- It is in this mode that you are able to oscillate the patient from 1-20Hz with pressures up to +/- 50 cmH2O
There are 2 modes which are triggered by the patient' s respiratory effort. These modes can be used as pressure support modes and an aid to weaning.
Respiratory triggered
- Provides triggered ventilation with the respiratory cycle triggered by the patient' s actual respiratory requirements
- The frequency is determined by either the patients rate or the minimum frequency set by the physician
- The I:E ratio is determined and set by the physician
- The trigger can either be through the cuirass or through the airway tube placed at or near the patients airway e.g. by the patients nose or mouth. Cuirass trigger will pick up more vigorous spontaneous breathing, whereas airway mode can be triggered by smaller, shallower respiratory effort.
- As the respiratory cycle is triggered by the patients own respiration, this allows better adjustment to the patients actual requirements. The respirator will wait for a period for the trigger; this is dependant on the trigger sensitivity set. If no trigger is detected during this period then the respirator will begin another cycle. In the event of apnoea the Hayek RTX will deliver the set back up rate.
- Trigger % should be 80-85% if higher you may need to adjust sensitivity, this is to ensure false triggers are prevented
- Minimum backup rate is 6 per minute i.e. 1 every 10 seconds
- Maximum backup rate is 60 per minute i.e.1 per second
Respiratory synchronised
- This mode is fully synchronised with the patients own respiration, automatically adjusting the arte and shape of breathing in sympathy with the natural breathing adjustments being made by the patient themselves.
- The patient' s inspiratory effort creates an initial trigger which is followed by a further trigger by the initial effort of expiration. The trigger can be either through the cuirass or airway.
- Difference between this mode at respiratory triggered is that on this mode the support is timed with patients own respiratory pattern, so no I:E ratio is set by the physician
- The I:E ration will be calculated and displayed
- This mode will allow the patient to breathe both at their own rate and determine their own shape.
- In the event of apnoea the Hayek RTX will deliver the set back up rate delivering fully controlled ventilation at the pressures set
Normal lung:
Neuromuscular conditions, ventilation during anaesthesia, and ventilation post cardiac surgery (especially in Children), Head and Spinal Injuries references: 10, 11, 12, 13, 13,14, 15, 16, 17, 23, 24, 25, 26, 27, 28, 29, 35, 36, 52
Inspiratory: -21
Expiratory: +7
I:E Ratio: 1:1
Frequency: * see below
* When using synchronised mode set a minimum backup frequency at 10 less than the patient's spontaneous breathing rate (lowest is 6cpm).
* When using control mode begin by setting frequency at 2-4 breaths above patient's own spontaneous breathing rate.
Sick lung:
Restrictive
Bronchiolitis** Cardiogenic Pulmonary Oedema, Chronic Obstructive Pulmonary Disease (COPD), Emphysema, CF, references: 39, 45, 46, 49, 53, 54
Inspiratory: -18
Expiratory: +6
I:E Ratio: 1:1
Frequency : 60 cpm in control mode (can be increased up to 120 to improve results where necessary), 40 cpm backup in synchronised.
If necessary it is also possible to increase span and pressures keeping a pressure ratio 3:1
e.g. change -21 +7 or -24 +8
Obstructive
Asthma, bronchiolitis**, PCP, TB Pneumonia
Inspiratory: -24
Expiratory: +8
I:E Ratio: 1:1 or 1:2
Frequency: at spontaneous respiratory rate of patient in control mode, or respiratory rate of patient -10pcm as backup in synchronised mode
Low Compliance/Low Lung Volume
Respiratory Distress Syndrome references: 33, 38, 41, 44
Inspiratory: -30 Expiratory: +10 I:E Ratio: 2:1 Frequency: 40, 50, 60cpm up to 120cpm depending on patient
** The pathophysiology of bronchiolitis means that there are both restrictive and restrictive phases during the disease process.
Divided into two parts
Vibration mode
This mode shakes and thins secretions
Insp/Expiratory: -8 +8
I:E Ratio: 1:1
Frequency: 800cpm *
Time 3-4minutes
* decrease the frequency for more tenacious secretions
Expiratory pressures in vibration mode are defaulted to the same as inspiratory pressures. Higher pressures are tolerated well e.g. +/- 15
Cough mode
This mode assists with expelling the secretions and can act as a mini sustained inflation.
Inspiratory: -25
Expiratory: +15
I:E Ratio: 4:1
Frequency: 50
Time: 3minutes
The negative pressure can be made more negative as required.
Completion of both modes represents one cycle of secretion clearance mode
Each secretion clearance session should last between 30-60 minutes
It is possible to use higher pressures in cough mode e.g. -35 +25 as tolerated by the patient
It is helpful to introduce one or two cycles every few hours for most infants with bronchiolitis. The number and frequency of cycles can be adjusted according to the severity of the infant's condition. Occasionally some infants cannot tolerate a full 3 minutes of cough when it is first introduced, in which case the mode setting can be changed earlier. They usually do get used to it fairly quickly.
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