Management of volume loss in ITU Flashcards
Techniques to increase lung volume in critical care:
- Positioning
- Deep breathing on the ventilator
- Manual hyperinflations (bagging)
- Neurophysiological facilitation
Positioning in ITU:
Remember too long in supine → basal atelectasis
So Turning from supine to side lying helps to:
-reverse atelectasis
-Reduce risk of pneumonia
-Promote comfort
-Protect tissue viability
Deep breathing on the ventilator in ITU:
Can be done if the ventilator allows for some spontaneous effort. You and the patient can see the results by watching the tidal volumes change on the ventilator monitor.
Neurophysiological facilitation in ITU:
(perioral stimulation) as it is useful for drowsy patients
Define MHI (bagging)
A powerful means of opening atelectasis lung areas, improving oxygenation, and facilitating the removal of secretions which ultimately improves lung compliance.
Essentially mimics ACBT (TEE and huffing and gentle tidal breathing)
The technique uses a manual bag circuit to deliver extra volume and oxygen to the lungs.
It is not the same as manual ventilation which is squeezing gas into the lungs at normal tidal volume
Indications for MHI
Prior/post endotracheal suctioning for:
- Removal of excessive or retained secretions that are not easily cleared by suctioning
- To reverse atelectasis - need pressures of 30 to 40cmH2O
- Poor cough mechanism
Self-ventilating tracheostomy patients who have Chest x-ray changes of lung collapse and/or consolidation or by areas that are poorly ventilated on auscultation
Indications to continue MHI:
Hypoxia to provide 100% oxygen
Sometimes to aid auscultation in the absence of any contraindications
Therapeutic effects of MHI:
- Facilitate mobilisation of secretions by mimicking huff/cough
- Improves oxygenation by optimising alveolar ventilation
- Improves lung compliance by removing secretions and reversing atelectasis
Consideration to make MHI more effective:
- Consider the use of 0.9% saline (2-10 ml) for thicker secretions
- Suction as soon as secretions are heard
- Shaking: to accelerate expiratory flow rates
- valve readjusted in response to lung compliance (or opened if the patient is coughing)
- if patient is awake the breaths should be times to inspiratory effort
Aim of MHI:
- Delivered at a rate that matches patients- aimed at increasing lung volume and enhancing expiratory flow rate to mimic deep breathing and forced expiration
- Slow deep inspiration: to gently increase tidal volume and steadily fill alveoli. Minimises risk of barotrauma or haemodynamic instability
- Inspiratory hold: to increase recruitment of alveoli via collateral ventilation helping mobilise secretions on expiration and increase lung volume.
- Increasing TV: elastic recoil of the lungs and chest wall is increased thereby increasing the expiratory flow rate
- Rapid release of bag: accelerate expiratory flow rates to mimic the huff, facilitating movement of mucus towards the mouth.
MHI technique:
- explain procedures to patient to reduce anxiety: inform patient they will miss a breath and then feel cool air
- position for PD if appropriate
- check vital signs (post position change)
- Connect to O2 & start flow (15L/min) & check bag not leaking
- switch off ventilator alarm and put ventilator on standby
- Connect the bag to the patient via catheter mount/closed suction circuit
- Deliver 3-4 slow normal tidal volume breaths at a rate matching patients RR using both hands. Observe thoracic expansion.
- Warn patient when to expect deep breath then give 1 manual hyperinflation breath with or without inspiratory hold (40cmH2O maximum pressure) for 2-3 secs.
- Quickly releasing the rebreathing bag after a MHI mimics a huff
- explain procedure throughout entire process
- continue until secretion are audible or perform suction if patient coughs or if no further secretions are heard/chest clear on auscultation.
- do not continue if any signs of distress, BP falls or if sustained arrhythmia develop or worsen
Complications of MHI:
- Barotrauma - pressures of 40cm H2O are required to reverse atelectasis. High pressures can rupture the respiratory tract into the surrounding tissue and can cause pneumothorax
- Hypoxia - If not performed well enough and the flow rate is not high enough
- Depression of respiratory drive - can occur when patients are being weaned from the ventilator as you taking over breathing can reduce the patients effort in taking their own breaths
- CV instability because increased intrathoracic pressure reduces venous return and consequent reduced cardiac output.
Contraindication to MHI:
- Severe bronchospasm (can be seen by peak airway pressure increase): increased risk of barotrauma
- PEEP < 15cmH20: causes desaturation on disconnection
- Undrained pneumothorax – look out for # ribs on x ray and surgical/subcutaneous emphysema: increase risk of barotrauma and consequent CVS instability
- Bullae – from emphysema check CXR increased risk of pneumothorax
Precautions for MHI:
-Low/high or unstable BP: Consider Risks vs benefits
-Cardiac arrhythmias/instability: Compromised venous return- further increases effort required to maintain adequate tissue perfusion
-High peak airway pressures:↑ risk of barotrauma
-Bronchospasm:↑ risk of barotrauma
(use a slow technique)
-PEEP 10 - 14cmH2O: The break in the circuit will cause loss of PEEP and can de-recruit lung → hypoxia and collapse
-Pneumothorax with bubbling chest drain: Increased bubbling means gas is escaping and you are not being effective
High FiO2 (> 0.8) or high tidal volumes > 800mls: No room for reserve
-↑ ICP
CPP=MAP-ICP: Increased intrathoracic pressure reduces mean arterial pressure (MAP) which can compromise ICP and cerebral perfusion pressure (CPP) → secondary brain injury. If the pt is hypoxic due to sputum retention then MHI may outway the risks – just keep your eye on the BP
-Post Lung Surgery: less lung means reduced lung volumes. High airway pressure may cause trauma/pneumothorax. Check with surgeons regarding stump pressure (be careful up to 20 days post op)
-Weaning patients from ventilatory support: May depress their respiratory drive
What is an alternative to MHI:
Ventilator Hyperinflation (VHI):
- Adjusting the ventilator settings to increase tidal volumes, simulating a deep breath to recruit collapsed alveoli
- Dangers & precautions the same as MHI – except for high PEEP (≥10cmH2O) & high FiO2
