Respiratory evaluation of patients requiring ventilator support due to acute respiratory failure

doi:10.4236/ojn.2012.223049

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Open Journal of Nursing, 2012, 2, 336-340 OJN

http://dx.doi.org/10.4236/ojn.2012.223049 Published Online November 2012 (http://www.SciRP.org/journal/ojn/)

Respiratory evaluation of patients requiring

ventilator support due to acute respiratory failure

Carmen Silvia Valente Barbas, Giovana Caroline Lopes, Débora Feijó Vieira, Lara Poletto Couto,

Letícia Kawano Dourado, Eliana Caser

University of São Paulo, São Paulo, Brazil

Email: [email protected], [email protected]

Received 16 September 2012; revised 19 October 2012; accepted 28 October 2012

ABSTRACT

This review, based on relevant published evidence

and the authors’ clinical experience, presents how to

evaluate a patient with acute respiratory failure re-

quiring ventilatory support. This patient must be care-

fully evaluated by nurses, physiotherapists, respira-

tory care practitioners and physicians regarding the

elucidation of the cause of the acute episode of respi-

ratory failure by means of physical examination with

the measurement of respiratory parameters and as-

sessment of arterial blood gases analysis to make a

correct respiratory diagnosis. After the initial evalua-

tion, the patient must quickly receive adequate oxy-

gen and ventilatory support that has to be carefully

monitored until its discontinuation. When available, a

noninvasive ventilation trial must be done in patients

presenting desaturation during oxygen mask and or

PaCO2 retention, especially in cases of cardiogenic

pulmonary edema and severe exacerbation of chronic

obstructive pulmonary disease. In cases of noninva-

sive ventilation trial-failure, endotracheal intubation

and invasive protective mechanical ventilation must

be promptly initiated. In severe ARDS patients, low

tidal ventilation, higher PEEP levels, prone position-

ing and recruitment maneuvers with adequate PEEP

titration should be used. Recently, new modes of ven-

tilation should allow a better patient-ventilator inter-

action or synchrony permitting a sufficient unloading

of respiratory muscles and increase patient comfort.

Patients with chronic obstructive pulmonary disease

may be considered for a trial for early extubation to

noninvasive positive pressure ventilation in centers

with extensive experience in noninvasive positive pres-

sure ventilation.

Keywords: Respiratory Failure; Noninvasive Ventilation;

Endotracheal Int ubat i on; I nvasive Mechanic al

Ventilation; Patient-Ventilator Synchrony

1. INTRODUCTION

Acute respiratory failure is a condition in which the res-

piratory system fails to keep an adequate arterial blood

oxygenation or carbon dioxide concentration. The main

causes that lead to an acute insufficient oxygenation (less

than 60 mmHg while breathing room air) or a PaCO2

elevation (more than 50 mmHg with a concomitant de-

crease in arterial pH) are: 1) Pulmonary parenchyma dis-

ease; 2) Cardiovascular disease (left ventricular failure,

pulmonary embolism); 3) Airway disease, 4) Neuro-mus-

cular disease; and 5) Respiratory drive alterations. It is

crucial to assess the cause of the acute respiratory failure

episode in order to give the patient the best treatment

option allowing its reversion [1].

2. FIRST ACTIONS IN RESPIRATORY

FAILURE PATIENTS

During the acute episode of respiratory failure, it is ne-

cessary to verify the level of consciousness, respiratory

frequency, tidal volume and peripheral oxygen saturation

(SpO2) and PaCO2 levels. If the patient is hypoxemic an

oxygen mask must be coupled to his/her face and pulse

oximetry should be monitored to obtain a peripheral

oxygen saturation above 90%. Use of high flow nasal

cannula oxygen (HFNC) is increasingly popular in adult

ICUs for patients with acute hypoxemic respiratory fail-

ure. This is the result of the successful long-term use of

HFNC in the neonatal field and recent clinical data in

adults indicating beneficial effects of HFNC over con-

ventional facemask oxygen therapy. HFNC rapidly alle-

viates symptoms of respiratory distress and improves

oxygenation by several mechanisms, including dead-

space washout, reduction in oxygen dilution and in in-

spiratory nasopharyngeal resistance, a moderate positive

airway pressure effect that may generate alveolar re-

cruitment and an overall greater tolerance and comfort

with the interface and the heated and humidified inspired

gases. Indications of HFNC are broad, encompassing

most if not all causes of acute hypoxemic respiratory

OPEN ACCESS

C. S. V. Barbas et al. / Open Journal of Nursing 2 (2012) 336-340 337

failure [2].

3. WHEN TO PROCEED TO

ENDOTRACHEAL INTUBATION? IN

WHICH PATIENTS IS A NONINVASIVE

VENTILATION TRIAL POSSIBLE?

If the patient is obtunded with irregular respirations, a

bag-mask ventilation with a as high as possible dose of

oxygen must be coupled to the patient’s face and an en-

dotracheal intubation and mechanical ventilation must be

initiated. Respiratory arrest, mental deterioration, and pro-

gressive exhaustion of respiratory muscles are also indi-

cations for endotracheal intubatio n

In patients already coupled to an oxygen mask that

present desaturation or have an arterial CO2 above 50

mmHg with a concomitant decrease in arterial pH a trial

of noninvasive ventilation may be initiated [3-5]. Pa-

tients with acute respiratory distress syndrome or hypo-

xemia, either in the postoperative setting or in the pres-

ence of immunosuppression, may also be considered for

a trial of noninvasive positive pressure ventilation. A

comfort interface with a shape and size that adequately

fits the patient’s face avoiding air-leaks is crucial for the

noninvasive ventilation trial success determining the pa-

tient’s compliance and the best synchrony between the

patient and the machine. A variety of interfaces for non-

invasive ventilation can be used in the acute care setting.

Nevertheless, prevention and monitoring of interfaces

related side-effects and evaluation of patient’s tolerance

are crucial to avoid noninvasive ventilation failure [3,4].

Assessing the success/failure of the noninvasive

ventilation trial:

After 30 minutes to 2 hours of the noninvasive venti-

lation trial initiation the patients must present:

1) A better level of consciousness and airway protec-

tion;

2) Being comfortable with the mask;

3) Decreased/normalization of respiratory rate;

4) Increased tidal volume compared to the beginning

of the trial;

5) Improved PaO2;

6) Lower PaCO2;

7) Hemodynamic stability

8) Not having a large abdominal distension.

If the patient responds well to the noninvasive me-

chanical ventilation trial, this ventilatory support moda-

lity must be continued while clinical treatment is con-

comitantly administered until the patient recovers from

the acute episode of respiratory failure allowing the dis-

continuation of noninvasive ventilation and the reinstitu-

tion of oxygen mask or room air ventilation [5].

If the patient does not respond well to the noninvasive

mechanical ventilation trial, keeping low tidal volume

ventilation, high respiratory rate, limited oxygen satura-

tion (less than 92% with FIO2 higher than 50%), pH less

than 7.2 and PaCO2 higher than 60 mmHg, endotracheal

intubation and invasive mechanical ventilation must be

promptly instituted in order to avoid complications and

guarantee a secure intubation [6-8]. After intubation, the

adequate positioning of the endotracheal tube must be

checked with a capnography or Chest-X-ray and the tube

cuff-pressure checked with a manometer and kept around

20 - 25 mmHg.

A capnography is usually used in Intensive Care to

monitor ventilation, mainly in neurologic patients. Car-

bon dioxide levels are frequently monitored during car-

diopulmonary resuscitation to aid in determining the

proper placement of an endotracheal tube and to assess

the effectiveness of resuscitation efforts. Although pulse

oximetry is useful in the assessment of oxygenation,

capnography provides more direct information on the

ventilatory status of a patient. This is particularly true

when patients are receiving supplemental oxygen, during

which oxygen saturation may be normal despite the

presence of marked hypoventilation. Conversely, capno-

graphy does not monitor oxygenation; hypoxemia may

be present even when a capnography tracing is normal.

There are two types of capnographs. Mainstream capno-

graphs use sensors that are placed directly into the

breathing circuit of a ventilator. Sidestream capnographs

draw a sample of gas away from the breathing circuit to a

separate gas sensor (The response of a sidestream device

to changes in carbon dioxide concentration is delayed by

a few seconds, since the gas must travel through the

sampling line before it can be analyzed. However, side-

stream capnographs can be used conveniently in a patient

who is not intubated if the patient is fitted with a face

mask or nasal cannula to monitor respiration. Nasal can-

nulas and face masks that feature integrated carbon di-

oxide sampling lines are commercially available. You can

modify standard face masks by attaching the sampling

line directly to the orifice of a mask or by securing the

sampling line inside the mask. A normal capnogram

shows a regular, nearly square waveform that oscillates

at the same frequency as the patient’s respiratory rate.

During inspiration, the capnogram should be at zero as

the patient breathes in fresh gas. When the patient starts

to exhale, th e first gas exhaled will be from the anatomi-

cal dead space and will contain little or no carbon diox-

ide. However, the concentration of carbon dioxide in the

exhaled gas will rise rapidly and plateau as the alveoli

begin to empty. As exhalation proceeds, the concentra-

tion of carbon dioxide remains high and increases sligh-

tly. The peak concentration reached at the end of exhala-

tion is the ETCO2. As the patient begins to inhale again,

the capnogram falls rapidly to zero, indicating the ab-

sence of carbon dioxide in the inspired gas. Capno-

C. S. V. Barbas et al. / Open Journal of Nursing 2 (2012) 336-340

338

grams must always be interpreted in conjunction with

other physiological variables, and clinical judgment is

important. Loss of the capnographic waveform may oc-

cur in several circumstances. These include apnea, the

disconnection of a ventilator circuit, the occlusion or

dislodgment of an endotracheal tube, or the occlusion or

disconnection of the sampling catheter. Waveforms that

do not return to zero during inspiration indicate re-

breathing of carbon dioxide, which can occur if the car-

bon dioxide absorber in an anesthesia machine is chemi-

cally exhausted, if a valve in the ventilator circuit is not

functioning properly, or if the flow of fresh gas is insuf-

ficient. An elevated baseline can also be seen if the de-

vice is calibrated incorrectly. Decreases in ETCO2 can

result from hyperventilation, pulmonary embolism, car-

diac arrest, sudden hypotension, hypovolemia, hypother-

mia, leaks in the sampling system, or a partial airway

obstruction [4]. Increases in ETCO2 may be caused by

hypoventilation, rising body temperature, bronchospasm,

adrenergic discharge, release of a tourniquet on an arm or

leg, or ventilation of a previously unventilated lung. Shal-

low breathing causes transient lowering of ETCO2 be-

cause of dead-space ventilation, but the ETCO2 rises

again after a deep inspiration when full gas exchange

occurs.

A gradient exists between the PaCO2 and the ETCO2;

this gradient increases as the dead-space volume in-

creases. In disease states characterized by increased dead

space and ventilation-perfusion mismatch, such as em-

physema, an arterial blood gas analysis is necessary to

obtain an accurate determination of the PaCO2 [9].

Several recent studies have advanced our understand-

ing of dead-space ventilation in patients with acute lung

injury/acute respiratory distress syndrome (ALI/ARDS).

They have demonstrated the utility of measuring physi-

ologic dead-space-to-tidal volume ratio (VD/VT) and re-

lated variables in assessing outcomes as well as thera-

peutic interventions. These studies have included the

evaluation of mortality risk, pulmonary perfusion, as

well as the effectiveness of drug therapy, prone position-

ing, positive end-expiratory pressure (PEEP) titration,

and inspiratory pattern in improving gas exchange. In

patients with ALI/ARDS managed with lung-protective

ventilation a significant relationship between elevated

VD/VT and increased mortality continues to be reported

in both early and intermediate phases of ALI/ARDS.

Some clinical evidence now supports the suggestion that

elevated VD/VT in part reflects the severity of pulmo-

nary vascular endothelial damage. Monitoring VD/VT

also appears useful in assessing alveolar recruitment

when titrating PEEP and may be a particularly expedient

method for assessing the effectiveness of prone position-

ing. It also has revealed how subtle manipulations of

inspiratory time and pattern can improve CO2 excretion.

Much of this has been accomplished using volumetric

capnography. This allows for more sophisticated meas-

urements of pulmonary gas exchange function including:

alveolar VD/VT, the volume of CO2 excretion and the

slope of the alveolar plateau which reflects ventilation:

perfusion heterogeneity. Many of these measurements

now can be made non-invasively which should only in-

crease the research and clinical utility of volumetric

capnography in studying and managing patients with

ALI/ ARDS [10].

4. USING INVASIVE MECHANICAL

VENTILATION DURING ACUTE

RESPIRATORY FAILURE

Assist-controlled modes are often used after sedation and

sometimes curarization for endo tracheal intubation. Usu-

ally a FIO2 of 100% is set to allo w an ad equate oxygen a-

tion until an arterial blood gas analysis is obtained. A

respiratory rate from 12 to 20 breaths per minute is often

adequate in most cases, preferably being lower in ob-

structive patients and higher in restrictive ones. Tidal

volume must be set between 5 - 7 mL/predicted body

weight, the lower values being the most suited in severe

cases with extremely low compliances and high resis-

tances [6-8]. To have the fatigued respiratory muscles

rest in these patients, 24 - 48 hours of full ventilatory

support may be needed, with sedation to su ppress the pa-

tients’ respiratory effort. In severe ARDS patients (PaO2/

FIO2 less than 120), a randomized controlled trial com-

paring cisatracurium to placebo for 48 hours showed an

improved adjusted 90-day survival rate and increased

ventilator free days in the cisatracurium group without a

significant increase in muscleweakness. Short-term pa-

ralysis may facilitate patient-ventilator synchrony in the

setting of lung protective ventilation. Short-term paraly-

sis would eliminate patient triggering and expiratory mu-

scle activity. In combination, these effects may serve to

limit regional overdistension and cyclic alveolar col-

lapse. Paralysis may also act to lower metabolism and

overall ventilatory demand [11].

In ARDS patients, protective lung ventilation strate-

gies with tidal volumes equal or less than 6 mL/kg of

predicted body weight have been associated with lower

mortality when compared with 12 mL/kg of predicted

body weight [12,13]. Use of PEEP titrated by the lower

inflection point of the inspiratory pressure-volume curve

has been associated with lower mortality in two random-

ized, prospective and randomized trial [14,15]. Recent

meta-analysis suggest survival benefits of higher PEEP

levels [16] and prone position in ARDS patients (PaO2/

FIO2 < 200) [17]. Early high pressure lung recruitment

maneuvers and application of sufficient PEEP levels to

maintain an open lung can be used in severe cases of

C. S. V. Barbas et al. / Open Journal of Nursing 2 (2012) 336-340 339

ARDS [18,19].

Controlled hypoventilation appears to improve the

clinical outcome of patients who have status asthmaticus.

Low tidal volume ventilation, acceptance of higher levels

of PaCO2 (till 80 mmHg), pH equal or higher than 7.2

and auto-PEEP monitoring to keep it less than 15 cm

H20 appears to decrease barotrauma occurrence [20].

In chronic obstructive pulmonary disease patients that

require invasive mechanical ventilation, an equilibrium

point among low tidal volume, high inspiratory flow rate

and prolonged expiratory time must be reached to avoid

excessive auto-PEEP or dynamic hyperinflation [19,20].

After 24 - 48 hours of respiratory muscles rest, as-

sisted or pressure support ventilation must be initiated in

order to preserve respiratory muscle activity and avoid

respiratory muscle dystroph y [20,21]. Patients with chro -

nic obstructive pulmonary disease may be considered for

a trial for early extubation to noninvasive positive pres-

sure ventilation in centers with extensive experience to

decrease mechanical ventilation duration [5,22].

Recently, new modes of ventilation such as neutrally

adjust ventilation (NAVA), proportional assist ventilation

plus (PAV-PLUS) and adaptative support ventilation (ASV)

are introduced in order to increase the patient control of

the ventilator and to increase information about lung

mechanics and respiratory drive. These new modes of

ventilation should allow a better patient-ventilator inter-

action or synchrony permitting a sufficient unloading of

respiratory muscles and increase patient comfort [23].

5. CONCLUSION

The evaluation of a patient in respirator y failure is a mul-

tidisciplinary task. It should be accomplished in a timely

manner, monitoring the patient, sequentially evaluating

physical signs and symptoms, laboratory data and timing

of noninvasive ventilation trial; endotracheal intubation.

After noninvasive ventilation or mechanical ventilation

is instituted, care should be taken to evaluate patient

comfort, synchrony and success of ventilatory support

which is a dynamic process demanding frequent re-

evaluations until the patient is ready to the spontaneous

breathing trial (SBT) and to the extubation process.

REFERENCES

[1] McLean, B.A. (2012) Acute respiratory failure and inten-

sive measures. Critical Care Nursing Clinics of North

America, 24, 361-375. doi:10.1016/j.ccell.2012.06.008

[2] Ricard, J.D. (2012) High flow nasal oxygen in acute res-

piratory failure. Minerva Anestesiol, 78, 836-841.

[3] Sferrazza P.G.F., Di Marco, F., Akoumianaki, E. and Bro-

chard, L. (2012) Recent advances in interfaces for nonin-

vasive ventilation: From bench studies to practical is-

sues. Minerva Anestesiol, 78, 1146-1153.

[4] Pisani, L., Carlucci, A. and Nava, S. (2012) Interfaces for

noninvasive mechanical ventilation: Technical aspects and

efficiency. Minerva Anestesiol, 78, 1154-1161.

[5] Keenan, S.P., Sinuff, T., Burns, K.E., Muscedere, J., Kut-

sogiannis, J, Mehta, S., Cook, D.J., Ayas, N., Adhikari,

N.K., Hand, L., Scales, D.C., Pagnotta, R., Lazosky, L.,

Rocker, G., Dial, S., Laupland, K., Sanders, K., Dodek, P.

and Canadian Critical Care Trials Group/Canadian Criti-

cal Care Society Noninvasive Ventilation Guidelines

Group (2011) Clinical practice guidelines for the use of

noninvasive positive-pressure ventilation andnoninvasive

continuous positive airway pressure in the acute care set-

ting. CMAJ, 183, E195-E214.

[6] Brochard, L., Martin, G.S., Blanch, L., Pelosi, P., Belda,

F.J., Jubran, A., Gattinoni, L., Mancebo, J., Ranieri, V.M.,

Richard, J.C., Gommers, D., Vieillard-Baron, A., Pesenti,

A., Jaber, S., Stenqvist, O. and Vincent, J.L. (2012) Cli-

nical review: Respiratory monitoring in the ICU: A con-

sensus of 16. Critical Care, 16, 219.

[7] Domingo, C., Blanch, L., Murias, G. and Luján, M. (2010)

State-of-the-Art Sensor Technology in Spain: Invasive

and non-invasive techniques for monitoring respiratory

variables. Sensors (Basel), 10, 4655-4674.

doi:10.3390/s100504655

[8] Kipnis, E., Ramsingh, D., Bhargava, M., Dincer, E., Can-

nesson, M., Broccard, A., Vallet, B., Bendjelid, K. and

Thibault, R. (2012) Monitoring in the Intensive Care. Cri-

tical Care Research and Practice, 2, 473-507.

[9] Ortega, R., Connor, C., Kim, S., Djang, R. and Patel, K.

(2012) Monitoring ventilation with capnography. New

England Journal of Medicine, 367, e27.

[10] Kallet, R.H. (2012) Measuring dead-space in acute lung

injury. Minerva Anestesiol, 78, 1297-1305.

[11] Papazian, L., Forel, J., Gacouin, A., Penot-Ragon, C., Per-

rin, G., Loundou, A., et al. (2010) Neuromuscular block-

ers in early acute re spiratory distress syndrome. The New

England Journal of Medicine, 363, 1107-1116.

doi:10.1056/NEJMoa1005372

[12] The Acute Respiratory Distre ss Syndrome Netwo rk (2000)

Ventilation with lower tidal volumes as compared with

traditional tidal volumes for acute lung injury and the

acute respiratory distress syndrome. The New England

Journal of Medicine, 342, 1301e8.

[13] Burns, K.E.A., Adhikari, N.K.J., Slutsky, A.S., Guyatt,

G.H., Villar, J., Zhang, H.B., Zhou, Q., Cook, D.J.,

Stewart, T.E. and Meade, M.O. (2011) Pressure and vol-

ume limited ventilation for the ventilatory management of

patients with acute lung injury: A systematic review and

meta-analysis. PLoS One , 6, e14623.

doi:10.1371/journal.pone.0014623

[14] Amato, M.B., Barbas, C.S., Medeiros, D.M., Magaldi,

R.B., Schettino, G.P., Lorenzi-Filho, G., Kairalla, R.A.,

Deheinzelin, D., Munoz, C., Oliveira, R., et al. (1998) Ef-

fect of a protective-ventilation strategy on mortality in the

acute respiratory distress syndrome. The New England

Journal of Medicine, 338, 347-354.

doi:10.1056/NEJM199802053380602

[15] Villar, J., Kacmarek, R.M., Perez-Mendez, L. and Aguirre-

Jaime, A. (2006) A high positive end-expiratory pressure,

C. S. V. Barbas et al. / Open Journal of Nursing 2 (2012) 336-340

340

OPEN ACCESS

low tidal volume ventilatory strategy improves outcome

in persistent acute respiratory distress syndrome: A ran-

domized, controlled trial. Critical Care Medicine, 34,

1311-1318. doi:10.1097/01.CCM.0000215598.84885.01

[16] Briel, M., Meade, M., Mercat, A., Brower, R.G., Talmor,

D., Walter, S.D., Slutsky, A.S., Pullenayegum, E., Zhou,

Q., Cook, D., Brochard, L., Richard, J.C., Lamontagne, F.,

Bhatnagar, N., Stewart, T.E. and Guyatt, G. (2010) High-

er vs lower positive end-expiratory pressure in patients

with acute lung injury and acute respiratory distress syn-

drome: Systematic review and meta-analysis. Journal of

the American Medical Association, 303, 865-873.

doi:10.1001/jama.2010.218

[17] Abroug, F., Ouanes-Besbes, L., Dachraoui, F., Ouanes, I.

and Brochard, L. (2011). An updated study-level meta-

analysis of randomised controlled trials on proning in

ARDS and acute lung injury. Critical Care, 15, R6.

doi:10.1186/cc9403

[18] Marini, J.J. (2010) Safer ventilation of the injured lung:

One step closer. Critical Care, 14, 192.

doi:10.1186/cc9028

[19] Barbas, C.S., Matos, G.F.J., Amato, M.B.P. and Carvalho,

C.R.R. (2012) Goal-oriented respiratory management for

critically ill patients with acute respiratory distress syn-

drome. Critical Care Research and Practice, 2012,

952168. doi:10.1155/2012/952168

[20] Younsuck, K. (2007) Ventilatory management in patients

with chronic airflow obstruction. Critical Care Clinics,

23, 169-181.

[21] Marini, J.J. (2011) Dynamic hyperinflation and auto-po-

sitive end-expiratory pressure: Lessons learned over 30

years. American Journal of Respiratory and Critical Care

Medicine, 184, 756-762.

[22] Glossop, A.J., Shepherd, N., Bryden, D.C. and Mills, G.H.

(2012) Non-invasive ventilation for weaning, avoiding

reintubation after extubation and in the postoperative pe-

riod: A meta-analysis. British Journal of Anaesthesia,

109, 305-314. doi:10.1093/bja/aes270

[23] Moerer, O. (2012) Effort-adapted modes of assisted brea-

thing. Current Care, 18, 61-69.