Page 405 - Clinical Small Animal Internal Medicine

373

VetBooks.ir

38

Respiratory Monitoring in Critical Care

Mathew Mellema, DVM, PhD, DACVECC

Applaud Medical, San Francisco, CA, USA

Purpose sensations of feeling unable to catch one’s breath or being
consciously aware of one’s breathing effort. The three
The purpose and goals of respiratory monitoring in criti- subcategories of dyspnea sensations identified in humans
cal care typically include the following: are air hunger, increased work/effort, and asthmatic
chest tightness. Experimental evidence exists to suggest
identification of patients in respiratory distress and
● that vertebrates other than humans are able to experi-
those experiencing dyspnea ence the first two of these. To date, no experimental
determination of response to specific or empiric
● approaches have been developed to determine if animals
therapies are likely to experience asthmatic chest tightness. Ideally,
assessment of the adequacy of alveolar ventilation
● the term dyspnea would be reserved for consideration of
assessment of the adequacy of oxygenation
● the sensory experience (akin to pain) and respiratory dis-
evaluation of gas exchange efficiency
● tress would be used to describe what clinicians might
evaluation of pulmonary mechanics in order to cate-
● observe (akin to nociceptive responses). Serial monitor-
gorize disease states, explain other related clinical ing of patients for signs of respiratory distress or dyspnea
findings, or monitor response to therapy. is the cornerstone of respiratory monitoring. Respiratory
monitoring may include many other tools, but these are
always best evaluated in light of current patient status
Identifying Respiratory Distress and clinical context.
and Dyspnea

Clinical Signs of Respiratory Distress
Respiratory distress is a state in which breathing efforts
are excessive or inadequate relative to the healthy state Box 38.1 provides an outline of broad categories of clini-
or the patient’s current requirements. While many defi- cal signs that may be present in a patient with respiratory
nitions rely on inadequate oxygenation or ventilation, dysfunction or distress. Two categories of sounds may
such approaches fail to account for patients in whom herald respiratory distress: those heard with the ear and
adequate gas exchange is obtained only with excessive those heard with the stethoscope. Stertor and stridor are
effort. Tachypnea (increased respiratory rate) and hyper- sounds that typically do not require a stethoscope to be
pnea (increased respiratory effort and/or chest excur- audible. Stertor is the presence of snoring‐like noises
sions) are often considered the hallmarks of respiratory during respiration. It is the result of abrupt displacement
distress; however, a smaller subset of patients may pre- of upper airway soft tissue structures and altered gas
sent with hyponea (decreased respiratory effort and/or flows. It is typically low‐pitched, discontinuous, and
chest excursions), bradypnea (decreased respiratory nonmusical in character. It may be evident on inspira-
rate), or both. This second type of patient is also in res- tion, exhalation, or both. Stridor is a high‐pitched, musi-
piratory distress. cal respiratory sound generated by altered gas flows in
Dyspnea is a term often used synonymously with res- the large airway. It is more typically heard on inspiration.
piratory distress in veterinary practice, although it has Either stertor or stridor can indicate an abnormality of
been suggested that this convention is not ideal. In the proximal upper airways (i.e., cranial to the thoracic
human medicine, dyspnea refers to the unpleasant inlet).

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical