Acid-Base Balance


I had intended to write about Acidosis this time but having spent sometime reading the literature I decided that the article written by Appel et al was the most informative data available.

It was published in a peer reviewed nursing journal this year and having appraised the reference list I feel is academically sound.

‘Acidosis can be described as a physiologic condition caused by the body’s inability to buffer excess H+ ions’ (Appel, 2015).

Understanding Acid-Base balance


Duncan Wright. RID: I-3810-2015



Appel, S. (2015). Understanding acid-based balance. Nursing, 38, 9-11.


Acute respiratory failure

Management of acute postoperative respiratory failure.



‘Non Invasive Positive Pressure Ventilation (NIPPV) is becoming the treatment of choice for patients with type 1 and type 2 respiratory failures in both the Emergency Department and general medical wards. Non Invasive Positive Pressure Ventilation is an overarching term to describe two different ventilation modes, Continuous Positive Pressure Ventilation (CPAP), and Non Invasive Ventilation (NIV). However, the choice of ventilation mode to treat the respiratory failure appears to be driven by personal opinion’, (Wright, 2015).

This talk will offer information for nurses to make informed clinical decisions regarding the appropriate mode of NIV to use.

Evidence suggests that respiratory failure can be divided in to two groups.

Type 1: which includes acute pulmonary odeama (APO) and acute respiratory depression syndrome (ARDS)

Type 2: which includes chronic obstructive pulmonary disease (COPD)

Clinical interpretation is often difficult and should be supported by arterial blood gas (ABG) analysis.

Type 1 is represented by low SPO2 and normal or reduced CO2

Type 2 is represented by low SPO2 and high CO2


Type 1

Non-Cardiogenic Oedema

In non-cardiogenic oedema, there is usually minimal elevation of pulmonary capillary pressure, except in volume overload due to oliguric renal failure.

It may reflect altered alveolar-capillary membrane permeability, such as Acute Respiratory Distress Syndrome (ARDS), and also lymphatic insufficiency following lung transplant.

Causes of Acute Pulmonary Oedema

The causes of acute exacerbation of congestive cardiac failure are conveniently summarized by the

acronym MADHATTER – Myocardial infarct, Anaemia, Drugs or dietary high fluid or salt intake,

Hypertension, Arrhythmias, Thyrotoxicosis, Toxic i.e. infection,

Endocarditis or embolism (pulmonary),

R enal failure or pregnancy (‘ruptured placenta’)

􀂃 M yocardial infarct,

􀂃 A naemia,

􀂃 D rugs or d ietary high fluid or salt intake,

􀂃 H ypertension,

􀂃 A rrhythmias,

􀂃 T hyrotoxicosis,

􀂃 T oxic i.e. infection,

􀂃 E ndocarditis or embolism (pulmonary),

􀂃 R enal failure or pregnancy (‘ruptured placenta’)

Type 1 should be treated by applying Continuous Positive Pressure ventilation (CPAP) and oxygen concentration used to regulate SPO2.

Type 2 by Bi-level NIV using a defined inspiratory positive airway pressure (IPAP) to increase ventilation, and a defined expiatory positive airway pressure (EPAP) to increase oxygenation.

The recommended starting pressures are: IPAP= 12-14 EPAP 6-8

The IPAP can be titrated upwards to reduce high CO2

And EPAP titrated upwards to increase oxygenation.


 Duncan Wright. RID: I-3810-2015



Beringer, R. (2006). Non Invasive ventilation in the Intensive care unit. Anaesthesia UK. from

Chawla, R., Chaudhry, D., Kansal, S., Khilnani, G., Mani, R., Nasa, P., . . . Suri, J. (2013). Guidelines for noninvasive ventilation in acute respiratory failure. Indian Journal of Critical Care Medicine, 17, 42-70.

Hannan, L. M., Dominelli, G. S., Chen, Y.-W., Darlene Reid, W., & Road, J. (2014). Systematic review of non-invasive positive pressure ventilation for chronic respiratory failure. Respiratory Medicine, 108(2), 229-243. doi:

Purwar, S., Venkataraman, R., Senthilkumar, R., Ramakrishnan, N., & Abraham, B. (2014). Noninvasive ventilation: Are we overdoing it? Indian Journal of Critical Care Medicine, 18(8), 503-507. doi:

Literature review


In order to provide high quality evidence based care, it is vital that our knowledge base is current and supported by sound academic literature. So how can we validate what we read?

Sourcing literature can be  a time consuming and endless process, it is therefore important to have a sound plan and objective.

1. Understand your topic.

We must first establish what it is we are looking for or wanting to ask:

The development of a clear and focused question is paramount. The Problem,Intervention,Comparison,Outcomes. ‘PICO’ system will help develop sound clinical questions.

To give an example. (P) In patients with type two respiratory failure. (I) Is CPAP. (C) as effective as Bi Level NIV (O) in reducing high levels of C02?

We can now search your usual databases  for the literature surrounding this specific clinical question (my personal favourite is The Translating Research into Practice, TRIP database) This will reduce the need to wade through hundreds of articles which have no relevance to our question.

 2. Decide on the level of evidence you require to change or confirm your practice.

Levels of evidence:

Literature is often published or provided from many sources, validating its  academic integrity is essential.Often outdated, ritualistic and substandard practice is passed on either personally from one clinician to another or as is often the case via poor non peer review journal articles. Now that you have your journal article you must validate the academic credibility of each.

The most recognised system of evidence classification is illustrated below:


(However this still has limited application in sound evidenced based practice but for the purpose of this post we will use the above.)

It is said that in order to change clinical practice one must read at least three pieces of evidence of level III or above prior to considering any change. I would go further and say that protocols, policy and guidelines for clinical practice need to be supported by sound level I & II evidence.

3. Critically appraise what you find.

Did the article answer my question? If no read no more and move on.

If it did, what method of data collection was used? Meta analysis, Systematic review,Randomised trial (you can grade the evidence level from this).If it meets your evidence requirement then add to you reading list.

Once you have graded your literature you can formally compare and contrast each against the other. I personally draft a short annotated bibliography which I use to formulate a later opinion, but this is not necessary. Formulate an opinion of your own based on evaluation of the evidence, if it is credible then it might be worth discussing with peers and planning a practice change.

icon3 Duncan Wright. RID: I-3810-2015


  1. Centre for Evidence Based Medicine. (2014). Asking Focused Questions. 2014,
  2. Lynn, G.-F., Ellen, F.-O., Bernadette Mazurek, M., & Susan, B. S. (2011). Implementing an Evidence-Based Practice Change. The American Journal of Nursing, 111(3), 54.
  3. Yu-Chih, C., Lee-Chun, T., & Shin-Shang, C. (2013). Strategy for Promoting Evidence-Based Nursing Practice in Hospital. Hu Li Za Zhi, 60(5), 25.