Respiratory: Respiratory Support Flashcards
What is meant by PEEP? [1]
Give three mechanisms of PEEP [3]
PEEP:
- Additional pressure in the airways at the end of exhalation stops the airways from collapsing at the end of exhalation
Positive end-expiratory pressure is added by:
* High-flow nasal cannula
* Non-invasive ventilation
* Mechanical ventilation
How does a high-flow nasal cannula work? [3]
Reduces the amount of room air that the patient inhales alongside the supplementary oxygen, increasing the concentration of oxygen inhaled with each breath.
It also adds some positive end-expiratory pressure to help prevent the airways from collapsing at the end of exhalation (although this effect is reduced if the patient opens their mouth).
Also, provides dead space washout: normally, dead space is ar that remains in airwaays and oropharnyx, not undergoing respiration. High-flow oxygen effectively clears this and replaces it with oxygen, improving patient oxygenation.
When is NIV normally given (in the day)? [1]
Why? [1]
At night (and then ok during the day)
During REM sleep your respiratory muscles are at their weakest
What does recruitment mean? [1]
Recruitment refers to a process where bronchioles and alveoli which would normally collapse at the end of expiration, are kept open (more lung volume is ‘recruited’).
The phase of breathing that requires the most energy is the process of overcoming the pressure required to re-expand collapsed segments of the lung
Describe the difference in pressures between CPAP and NIV / BIPAP
CPAP:
- One continous pressure
BIPAP:
- Two pressures: high pressure when you breath in and low pressure when you breath out. Difference in pressure helps ventilation
When [5] and where [2] is NIV indicated?
Acute T2RF: COPD exacerbations
- Inpatient
Chronic T2RF: At home
- Kyphoscoliosis
- Neuromuscular
- Obesity hypoventilation syndrome
- COPD
Which complications of hypoxia does long term oxygen therapy reduce? [2]
Cor pulmonale
Polycythaemia
Describe how NIV works to provide O2 therapy [3]
NIV delivers differing air pressure depending on inspiration and expiration.
The inspiratory positive airways pressure (iPAP) is higher than the expiratory positive airways pressure (ePAP).
Therefore, ventilation is provided mainly by iPAP, whereas ePAP recruits underventilated or collapsed alveoli for gas exchange and allows for the removal of the exhaled gas.
Explain how CPAP works (when providing oxygen therapy) [1]
CPAP supplies constant fixed positive pressure throughout inspiration AND expiration. It, therefore, is not a form of ventilation, but splints the airways open
What are the indications for NIV? [3]
Indications for NIV include:
- COPD with respiratory acidosis (pH < 7.35)
- Hypercapnic respiratory failure secondary to chest wall deformity (scoliosis, thoracoplasty) neuromuscular disease
- Weaning from tracheal intubation
NB: These indications assume that optimal medical management is already in place.
What are the indications for CPAP? [4]
- Hypoxia in the context of chest wall trauma despite adequate anaesthesia and high flow oxygen (pneumothorax should be ruled out using a chest x-ray prior to commencing CPAP)
- Cardiogenic pulmonary oedema
- Pneumonia: as an interim measure before invasive ventilation or as a ceiling of treatment
- Obstructive sleep apnoea
CPAP is often started at [] H2O and gradually increased to reduce hypoxia.
NIV is often started at iPAP [] and ePAP []
H2O is typically increased in [] cm intervals by approximately [] cms every [] minutes until a therapeutic response is achieved.
CPAP is often started at 4cm H2O and gradually increased to reduce hypoxia.
NIV is often started at iPAP 10 and ePAP 4.4
H2O is typically increased in 2-5cm intervals by approximately 5cms every 10 minutes until a therapeutic response is achieved.
Based on current evidence CPAP & NIV pressures should not exceed [] cm H2O at any point.
Based on current evidence CPAP & NIV pressures should not exceed 25 cm H2O at any point.
Name a complication of having ePAP [1] and iPAP [3] too high
ePAP
- hypotension
iPAP
- mask to leak
- reduce patient tolerance
- cause stomach inflation increasing the risk of aspiration.
Oxygen can be delivered in many ways. State the 3 devices used and the oxygen flow rates (L/min) and approximate FiO2s they can give.
Nasal Cannula
- 1L/min: 24% FiO2
- 2L/min: 28% FiO2
- 3L/min: 36% FiO2
Simple Face mask:
- 5L/min: 40% FiO2
- 8 L/min: 60% FiO2
Face mask with reservoir (non rebreather mask):
- 8L/min: 80% FiO2
- 10L/min: 95% FiO2